Sidebar: The Tupolev OOS

clean

A model of the OOS shuttle, believed to be from a Russian magazine in the 1990s. If you have more information about this picture, please contact the author.

During the 80s the USSR’s space program stayed remarkably focused on Energia/Buran and the Mir space station, especially when compared to the infighting that marred the years 1966-1975. It fended off or adapted to a number of distractions, whether it was Vladimir Chelomei‘s repeated attempts to regain his previous, short-lived position on top of it, or airplane design bureaus suggesting anything from conservative alternatives to the recently discussed Myasishchev M-19 nuclear scram/ramjet.

The OOS was a late Soviet-era shuttle proposal from the Tupolev bureau, an also-ran in that country’s space business despite a strong position in civil aviation and strategic bomber development. Proposed as a fully reusable replacement for Buran sometime around the year 2000, it was about the same size as that craft or the American Space Shuttle, though somewhat heavier at 100 tonnes when fuelled. With a crew of two cosmonauts. it had a payload of 10 tonnes to and from low-Earth orbit.

If you’re a long-time reader of this blog, or just sufficiently into spacecraft, you probably slotted the shuttle pictured above toward the conservative end of that spectrum. Apart from the more-rounded contours, it looks to be much like the Shuttle, particularly in the shape of the underside. There, too, we have the usual ceramic tiles for dissipating the heat of re-entry. The engines are not visible, but I can tell you that there were three, burning LH2 and LOX during the ascent to orbit (though, curiously, switching out the hydrogen with kerosene for orbital maneuvers). Knowing that would likely not change your opinion at all.

Given that it’s was to be fully reusable, the ten-tonne payload mentioned earlier may have got you wondering, though. The actual American and Soviet shuttles had payloads in the 25-30 tonne range, so alright—there’s clearly some sort of tradeoff there. You’d be well-advised to wonder about the rest of the OOS’s configuration. Side boosters but no external tank? Perched on a reusable rocket in some manner, maybe?

Well, no. “OOS” stood for Odnostupenchati Orbitalni Samolyot, ‘one-stage orbital plane’, But a single-stage-to-orbit craft the size of the Orbiter? Surely that’s not possible.

This goes to show that you don’t think like a Soviet aircraft designer circa 1989. The OOS was to have been air-launched, and the other half of the system was the Antonov AKS:

AKS

Aerospace aficionados will remember that the An-225, which was used to piggy-back the Buran shuttle around the Soviet Union, was by most measures the largest aircraft ever built. This is two of them, one wing apiece removed and replaced with a sort of aerodynamic bridge, and then 675 tonnes of spacecraft and rocket propellants attached to its underside. It had twelve turbojet engines for when it flew without the orbiter attached (the dark circles in the diagram above, at lower right), with a supplementary ten more being added during launch operations (the white circles). The Aristocrats! With a length of 83 meters (272 feet), a wheelbase of 40m (131 feet) and a wingspan of 153m (502 feet), the combination came in at a whopping 1650 tonnes. By contrast, a fully fueled late-model 747 has a maximum takeoff weight of just under 440 tonnes.

There has been only one successful air-launching system in the world to date, Orbital ATK’s Pegasus. It weighs 23.1 tonnes and can put 0.44 tonnes in orbit; it’s launched from a Lockheed L-1011, already getting into the neighborhood of large airplanes. So start with some skepticism that 20 times this in launch mass and payload are a possibility for the late-era USSR.

Further, I haven’t (unfortunately) been able to find a detailed description of the AKS/OOS’s mission profile. I’d like to see it because I’m having a hard time picturing what the moment of separation would look like. Or rather, I have an image of the support crew aboard the AKS bouncing around like ping-pong balls in a boxcar once the plane, straining to get the orbiter to altitude, suddenly cuts loose 675 tonnes. For that matter, the OOS would have to light its engines pretty quickly thereafter or defeat the purpose of an air launch. As these were in the same class as the RS-25’s on the American Shuttle—the noise aboard the AKS, now presumably not all that far above and behind it, would have been intense.

I’m on record for my begrudging appreciation of the come-what-may technological megalomania that gripped the superpowers post-WWII. The US grew out that uncritical mindset after Love Canal and Three Mile Island, while the Soviets carried on until 1989. That extra time coupled with fossilized technocrats in charge allowed awe-inspiring audacity in technology of it to grow even greater than it did in the West.

Even so, I can’t imagine anyone with the power to make the Tu-OOS happen actually doing so. It would have been an immensely expensive and difficult project right at a time when the Soviet Union was in no position to take one up, and technological limitations would have prevented anything like it at an earlier point in that country’s history. The OOS/AKS was a paper project, and would have remained so.

Sources:

OOS, la bestia de Tupolev y Antonov

OOS, el sistema espacial de lanzamiento aéreo definitivo

Artist Vadim Lukashevich has numerous renders of the AKS/OOS combination on Buran.ru (screll down to the second half of the page).

Readers will note a lack of primary sources here. I’m convinced of this project’s existence, but any pointers to a source that’s a little more direct than what I’ve relied upon here would be most welcome.

 

LANTR LTV/LEV: A New Way to the Moon

lantr-lev-side-by-side-comparison

Two versions of the LANTR LTV/LEV. On the left is one suggested for a SSTO launcher that could carry 20 tons to orbit and had a 13.5 meter payload bay. The one on the right could fit in a 9.5 meter cargo bay, at the cost of using less efficient methane for lander fuel, a smaller crew capsule, and a fiddly tank-within-a-tank to hold some of the craft’s liquid oxygen oxidizer. Public domain image composited from two separate diagrams in NASA’s Human Lunar Mission Capabilities Using SSTO, ISRU and LOX-Augmented NTR Technologies A Preliminary Assessment. Click for a larger view.

What it was: A mid-90s proposal for a lunar mission using an innovative rocket engine for the trip to the Moon and some basic lunar industry to refuel its chemically-driven lander for the trip back. It was one of the first proposals for a Moon mission to try and move away from a brute-force Apollo-style mission that was impossible to fund.

Details: The core difficulty with a Moon mission, or a mission to much of anywhere really, is that you need such massive vehicles. The Saturn V, for example, was 2950 tonnes when fueled, and was 111 meters tall. It was accordingly expensive: approximately US$700 million in 2016 dollars. Reusability was the route taken in the decades since to try and bring this down, but the Space Shuttle ended its life costing US$450 million per launch and for a considerably smaller payload being taken to orbit too.

By the early 1990s, in-situ resource utilization (ISRU) was seen as the next coming thing for making missions cheaper. This is to say, don’t haul all the mass you need up into space, take advantage of whatever mass is already there wherever you’re going. The difficulty here is that that mass is useless rock and, to a much lesser extent, water ice. The most obvious thing to do would be to refine cryogenic rocket propellants from it, as both rock and ice can be sources of oxygen and hydrogen. By the mid-90s people had been thinking for several years about how to do that, and what what would be possible once it could be done.

The most famous fruit of this effort was planning for Mars missions, partly because the vehicles for a traditional flight there would be ridiculously large even by Saturn V standards and partly because Mars’ carbon dioxide atmosphere is almost trivially easy to turn into methane (a decent rocket propellant) if you bring along some hydrogen from Earth. Less well-known is a lunar mission using ISRU which was developed at NASA’s Lewis Research Center.

In the early 1990s Lewis had been involved in the development of a nuclear rocket of an unusual type, what they called a LOX Augmented Nuclear Thermal Rocket (LANTR). A regular nuclear thermal rocket like NERVA runs on pure hydrogen, not burning anything at all and simply relying on nuclear power to heat the propellant and produce a high specific impulse. Unfortunately liquid hydrogen is very low density, and so the tank to hold it has to be large—and it doesn’t matter how light something is if you literally can’t fit it into the cargo bay of the Space Shuttle, or however else it is you’re planning on getting it into orbit.

The LANTR solved this problem by using liquid oxygen along with the hydrogen. After being heated by the reactor, the hydrogen was mixed with oxygen, which would then burn. This had the paradoxical effects of reducing the engine’s specific impulse, but also radically reducing the amount of hydrogen needed and making the necessary hydrogen tank much smaller. Liquid oxygen is seventy times denser than LH2, so its tank would be small too. The usual mix of oxygen to hydrogen is near 1:2 (as the chemical formula “H2O” would suggest), but even when mixed 5, 6 or 7:1 with the hydrogen the reduced specific impulse of the LANTR was still considerably better than you got with a conventional LOX/LH2 rocket while also being smaller than a pure-hydrogen nuclear rocket..

artist

“Artist’s Illustration of a Self-Contained, Modular LUNOX Production Unit”, plus an astronaut apparently taking a selfie. Public domain image from A Revolutionary Lunar Space Transportation System Architecture Using Extraterrestrial LOX-Augmented NTR Propulsion. Click here for a larger view.

The leap to lunar ISRU came with the realization that oxygen was a major component of the Moon’s soil. For example, the orange soil famously (and excitedly) discovered by Jack Schmitt during Apollo 17 contained hydrated iron oxide, and was rich in oxygen and water. At Lewis, the combination of LANTR and ISRU for a Moon mission crystallized in a flurry of papers spearheaded an engineer there, Stanley Borowski, in combination with a variety of colleagues. Rather than go with an already compact Moon mission using entirely Earth-sourced oxygen, why not use the Moon’s native oxygen for oxidizer on the way back? The result would be smaller and cheaper still.

The result was a proposal to build a Moon landing ship that was embedded in some basic Lunar industry that would be set up prior to the crewed landing. The first step would be to send an automated lander with a teleoperated mining equipment to a site where ilmenite or some other oxygen-rich rock had been pinpointed from orbit. Also included would be a 35-kilowatt nuclear reactor, which would provide the heat to break down the lunar rock with the hydrogen that would be brought along too, producing water. The water in turn would be broken down to oxygen and hydrogen, the former being stored and the latter recycled to start the process again on the next batch of rock.

Once 10.5 tons of liquid oxygen had been built up (a process which would take a year), the LANTR LTV/LEV (Lunar Transfer Vehicle/Lunar Excursion Vehicle) crewed mission would begin. Here a little bit of variation appears. When first suggested in 1994 the craft was assumed to be using a Shuttle-C, a derivative of the Shuttle for cargo only, to get to orbit—the LANTR wasn’t powerful enough to lift the whole works by itself (and no-one was very keen on firing a nuclear engine at ground level in any case). The Shuttle-C was already a cancelled project, however, and by 1995 NASA had been pinning its hopes on the VentureStar or some similar SSTO. At the time the LANTR LTV/LEV was being bruited about, the size of the SSTO’s payload bay hadn’t been nailed down and while NASA had specified 20 tons to LEO it was unclear how long the cargo it carried could be, Accordingly Lewis Research Center came up with two LANTR LTV/LEV configurations, each of which would be lifted in three pieces and mated in orbit.

If the SSTO gave them 13.5 meters to work with, the result was a 58.8-ton, 26.2 meter-long craft. Compare that with roughly 140 tons and 35 meters for the Apollo LM/CSM/S-IVB that launched the Apollo astronauts to the Moon. This version of the LANTR LTV/LEV would have be entirely fueled by LOX and LH2, excepting (presumably, as none of the sources say) hydrazine for the RCS thrusters as usual. On top was a curiously inverted command module; the author could find no discussion of how that was handled when time came for re-entry, so one presumes rotatable seats for the crew.

The longest part of this variation was the joint LH2/LOX tank for the transfer vehicle, while the widest was the bulbous hydrogen tanks on the lander. Both had to go to get into the smaller 9.5-meter SSTO payload bay suggested. The lander was switched to a more-compact but less efficient fuel, liquid methane, while one of the two oxygen tanks for the LANTR was moved to inside the LH2 tank, and outfitted with a double wall that would keep the supremely cold hydrogen from solidifying the oxygen within. The resulting craft was slightly lighter at 58.5 tons and definitely shorter at 24.2 meters, but in return they had to come up with some way of shaving 700 kilograms off of the crew capsule. Both variations of the capsule were approximately the same size as the Apollo CM, though the first’s was slightly larger than the second.

profile

The LANTR LTV/LEV mission profile. Note the direct descent and direct return. Public domain image via NASA from Human Lunar Mission Capabilities Using SSTO, ISRU and LOX-Augmented NTR Technologies A Preliminary Assessment. Click here for a larger view.

There was no LM, though, because the LEV was a direct-descent, direct-return vehicle. This did mean that if the stay on the lunar surface was to be of any length, a third mission, automated like the LOX plant, would have to be sent beforehand to give the astronauts a habitat. The LEV itself was inadequate otherwise.

What happened to make it fail: Though the mission was considerably cheaper than an Apollo-style trip to Moon—Johnson Space Center was looking at the time to spend less than US$1 billion on a Lunar return mission—not even that amount of money turned out to be available in NASA’s budget, particularly after the decisions were taken to continue with the Space Shuttle and build the International Space Station around the same time as the proposed first flight of a LANTR LTV/LEV’s, around 2001.

It also didn’t help that the craft came to an unwieldy size. It was intended to be launched on the VentureStar, and that never came to fruition. A comparable mission restricted to launch vehicles that actually existed needed one Shuttle mission and one launch of a Titan IV (which could lift longer payloads than the Shuttle could), a peculiar and expensive combination.

Something like it still could have begun as late as the about ten years ago, but then a discovery about the Moon put the final nail in its coffin. From 1994 through 2009 it became increasingly clear that the Moon had ice in some of its South Polar craters, with the case being settled by the Chandrayaan-1 probe. This changed the game for ISRU, since ice is a lot more useful raw material than lunar soil. Essentially all serious planning for a Moon mission since then has reflected this, and lunar rock has fallen by the wayside.

What was necessary for it to succeed: Much like the First Lunar Outpost, the LANTR LTV/LEV’s best bet would have been at the time the Clinton Administration was trying to decide how to help occupy the former Soviet Union’s rocket scientists so that they wouldn’t end up designing missiles for who knows what country. The decision to go for an joint space station rather than a joint lunar mission or base was a relatively easy one, given the USSR’s experience with stations, but it’s not too difficult to see the US deciding to go for the public relations spectacle of the Moon over the more staid ISS.

Otherwise the LANTR LTV/LEV is a sound concept if the promised Isp advantage holds, to the point that (by the standards of this blog) something much like it still would be worth building and flying. The primary difficulty with it in 2016 might be, oddly enough, that it’s too small. Sixty tons falls into the “between two stools” range that we discussed in the entry on the R-56, too big for something like an Ariane 5 or Delta IV Heavy, but too small for the upcoming SLS. Given that you’re going to have to use an SLS and that rocket will quickly outstrip 60 tons by a lot, why not design a spacecraft that uses up the extra payload capacity? Fans of SpaceX’s Falcon Heavy effort might want to take some notes, though.

Sources

A Revolutionary Lunar Space Transportation System Architecture Using Extraterrestrial LOX-Augmented NTR Propulsion. Stanley K. Borowski, Robert R. Corban, Donald W. Culver, Melvin J. Bulman, and Mel C. Mcilwain. 1994

Human Lunar Mission Capabilities Using SSTO, ISRU and LOX-Augmented NTR  Technologies A Preliminary Assessment. Stanley K. Borowski, 1995

High Leverage Space Transportation System Technologies for Human Exploration Missions
to the Moon and Beyond. Stanley K. Borowski and Leonard A. Dudzinski. 1996

The R-56: “Yangel Works for Us”

Thre possible arrangements of the R-56 rocket

Three possible arrangements of the R-56 rocket. The one on the right is the “4-4-1” module arrangement initially favoured, while the one at centre is close to the monoblock version finally settled on (it is missing the flared skirt necessary to house all of its engines). Original source unknown.

What it was: A four-stage rocket proposed by OKB-586 in the early 60s. It was aimed at the Moon, despite having a payload of 40 to 50 tonnes, making it much lighter than any of the Saturn V, N1, or Energia. It still would have lifted more than any rocket being flown in 2016.

Details: In February 1962 Nikita Khrushchev organized a meeting of the USSR’s Defense Council with the main missile designers in the Soviet Union at his dacha in Pitsunda (a resort town in the Georgian SSR) for the purpose of rationalizing their missile and space programs. The main players were Sergei Korolev with OKB-1 and Vladimir Chelomei with OKB-52, but a third invitee was Mikhail Yangel, the head of OKB-586.

While Korolev had surged to the head of the Soviet space program post-1957 and initially stood first in ICBM development, all based on variations of the R-7 rocket, by 1962 he had lost leadership in the latter to Yangel. The previous November his R-16 had become operational, and its use of storable propellants made it more militarily desirable than the liquid oxygen-using R-9 that was OKB-1’s response. Though the R-9 could be fuelled and fired in roughly the same amount of time, the feeling among almost everyone but Korolev was that storable fuels were the way forward when it came to developing a nuclear strike capability that could be used with little notice.

Meanwhile a fourth man and his bureau was working behind the scenes. Valentin Glushko had been trying to make large engines that used LOX for oxidizer. The tremendous vibration in his prototypes led to combustion instabilities that caused, as they say, “rapid disassembly”. Convinced that the problem could not be cracked, he had come around to storable propellants, and this had become a problem between him and Korolev. OKB-1 was pushing ahead with the N1 and, while storables were considered for that project, the writing was on the wall: Korolev wanted LOX and kerosene, or LOX and liquid hydrogen. A few years previous Glushko could have pushed back effectively, but Khrushchev had been downsizing the USSR’s military aviation efforts, and underemployed bomber-designing bureaus had been growing new departments devoted to rockets—the N1 would end up flying, for sadly abbreviated distances, using engines developed by Nikolai Kuznetsov’s OKB-276.

Glushko hedged his bets by teaming up with Chelomei on the UR-700 and the UR-500, which were aimed at the 70+ and 20-tonne payload targets set by Khrushchev. The former was to be a super-heavy interplanetary space launcher and the latter was a combination heavy LEO space launcher and ICBM. The smaller of the two figures was apparently selected due to the test of the RDS-220 hydrogen bomb (better known by the name given to it in the West, the “Tsar Bomba”) a few months earlier. This 100-megaton demonstrator had come in at just under 27 tonnes, and it was thought that refined versions with about half the yield would come in several tonnes less than that.

These two rockets were OKB-52’s proposal to the Defense Council meeting. OKB-1 countered with the already-underway N1 and, for the smaller launcher, the N2, which was essentially the N1 with its tetchy first stage removed. Seemingly out of worry that OKB-1 would still prevail, Glushko had arranged for another card in his hand—Yangel.

A relative newcomer to the space side of missile work, Yangel had earned a reputation as someone who listened to the military with the R-12 and R-16 missiles, in contrast with Chelomei and Korolev, who were viewed to varying extents as prima donnas, or at least less than entirely focused on military applications of their rockets. Yangel parleyed this approval into an unmanned satellite launch that was to go ahead the next month: Kosmos-1, the very first mission of the soon-to-be-ubiquitous Kosmos program that represented the large majority of Soviet launches from 1961 until the fall of the USSR. Yangel was interested in extending his nascent space work into manned programs, at least to the extent of designing the rockets for them, and he and Glushko had initially worked on creating a rocket, the RK-100, using the same storable propellant engines that OKB-52 was designing for Chelomei. If Glushko failed to unseat Korolev through Chelomei, then teaming with Yangel would give him another bite at the apple.

The RK-100 was a clustered rocket and Yangel was reportedly displeased with the particular design that his OKB-586 came up with. In any case the first comprehensive space policy statement by the Soviet government, made in 1960, ruled out any possibility of it going forward. At this point the focus shifted to another Yangel-Glushko collaboration. Once again a clustered approach was used. Working on the base of a booster “module” resembling the smaller rockets with which OKB-586 had had success, this new rocket consisted of four modules on the first stage, four on the second, and then a core booster being the third and final stage. This proposal was dubbed the R-56, and Yangel brought it and another design, the R-36, to the conference.

What he didn’t do was go head-to-head with Korolev and Chelomei. As initially conceived the R-56 would slot into the space between the 20 and 70 tonne launchers, lifting 30-40 tonnes or so, while the R-36 was much smaller than any of the other rockets mentioned, aiming for a sweet spot in automated satellite launches around 1-2 tonnes to LEO.

The meeting did not go well for Yangel’s crewed space ambitions as by April a turgidly named decree called “On the most important projects of intercontinental ballistic and global missiles and carriers of space objects” was issued. It instructed the bureaus involved to go for the N1 as a space vehicle, the UR500 (which would eventually become the Proton) as both a space vehicle and ICBM, and the R-36 solely as a missile—though it too would become a satellite launcher one day, the Tsyklon. However, in the few weeks of space between the original meeting and the decision, Glushko began lobbying the Strategic Rocket Forces and Dmitri Ustinov about not only the “4-4-1” module version but one with a “7-6-1” configuration that he said would lift 70 tonnes—obviously the direct challenge to the N1 and UR-700 that Yangel did not make himself. His efforts paid off. While not authorizing the R-56, OKB-586 were given permission to at least study the “4-4-1” configuration.

A year later, in 1963, the order for the R-56 was revised to specify that it should lift 40 tonnes to LEO. While Yangel’s bureau studied modular rockets that could handle this new requirement, for all intents and purposes they went back to the drawing board and settled on a completely different approach: a four-stage “monoblock” arrangement, to use the Russian term. This is the familiar, boosterless approach where each stage is singular and is merely put on top of another singular stage—the Saturn V being the most famous example of this. The first two stages of this R-56 did the heavy work of getting a payload into orbit, while the third was used to get it to geosynchronous orbit, if that was the intended destination. The optional fourth stage would be for the extra push needed on lunar and planetary missions.

The first stage would be outfitted with sixteen RD-253 engines, the same one to be used on the UR-500 (which had six) and which was ready to fly in July, 1965. This cluster of engines was actually wider than the intended 6.5-meter diameter of the first stage, so it was installed with a short skirt which enclosed 8.2 meters at the base. The second stage had one of the same engine, equipped with a modified bell tuned for operations in vacuum, as well as a small steering engine that produced 15% of that stage’s total thrust. The third stage tapered from 6.5 meters down to 4 meters in diameter, which was the gauge of the rocket up to the top of its 67.8 meter tall stack. Loaded up with Glushko and Yangel’s preferred N2O4 and UDMH, it would weigh in at 1421 tonnes. Compare this with the Saturn V’s 110.6 meters and 2970 tonnes, or the Energia’s 2270 tonnes (not counting Buran) and 58.765 meters. While not in their class, this new R-56 was heading in their direction. If it had been built to spec, it would have been able to lift a little over 46 tonnes to a 200-kilometer orbit when launched from Baikonur, or 12.6 tonnes to the Moon.

What happened to make it fail: All the meetings and decrees regarding the Soviet space program failed to straighten out the USSR’s lunar program. At the end of 1963, multiple boosters and spacecraft were still in play, and the Soviet leadership had still not even formally authorized an attempt by their country at the Moon landing. In an effort to finally settle things, in March 1964 Yangel proposed to the Military-Industrial Commission that Soviet space efforts be split three ways: OKB-1 would work on the lunar spacecraft, Chelomei’s group would get the automated probes to the Moon and the planets, and he would build the rockets.

The Commission turned him down, reasoning that too much work had been put into the N1 already for it to be replaced now. There was reportedly also some discomfort with the fact that the R-56 would need two launches (at minimum) for a Moon mission, which implied a docking in orbit at a time when the first Soviet docking was more than three years in the future.

Yangel then petitioned in succession both Dmitri Ustinov and Leonid Brezhnev (seven months from becoming leader of the USSR, but then in charge of the space program and a native of Dnepropetrovsk where OKB-586 was based). Neither would back him, and the R-56 was formally cancelled by another decree, “On speeding up work on the N1 complex”, that was made on June 19, 1964.

After the Moon program was finally approved in August of 1964, Yangel’s bureau was assigned to work on the terminal descent/ascent engine for the LK-1, the program’s lunar lander. It thus had the distinction of being one of the few pieces of the Soviet Moon landing craft to make it into space, as it was tested successfully in orbit three times in 1970-71.

What was necessary for it to succeed: The main problem with the R-56 program seems to have been Yangel’s willingness to let go, as opposed to the on-rushing bulls that were Korolev and Chelomei. If he’d been willing to push harder or been a little luckier during the 1962 meeting he might have won the day—Sergei Khrushchev specifically says that he thinks his father would have picked the R-56 at that time if Yangel had presented first rather than last.

On the other hand, even down to 2016 no-one has ever built a rocket with a payload capacity in the 40-50 tonne range (SpaceX’s under-development Falcon Heavy is closest, at 54.4 tonnes). Smaller is fine for almost all launches, and crewed missions absolutely require more if going to the Moon or beyond (barring the construction of a larger craft using multiple launches, which has also never been done). There’s good reason to believe that even if it had flown, the R-56 might have ended up not being good for much of anything.

Sources

“Heavy Launch Vehicles of the Yangel Design Bureau, Part 1”, Bart Hendrickx. Journal of the British Interplanetary Society, vol. 63, Supplement 2. 2010

“Heavy Launch Vehicles of the Yangel Design Bureau, Part 2”, Bart Hendrickx. Journal of the British Interplanetary Society, vol. 64 Supplement 1. 2011.

Nikita Khrushchev and the Creation of a Superpower, Sergei Khrushchev. Penn State University Press. 2001.

Sidebar: Alexeyev/Sukhoi Albatros

albatros

A conjectural diagram of the Albatros launcher, by Mark Wade of Encyclopedia Astronautica. Click for a link to the associated article. Used with permission.

Rostislav Alexeyev built the latter part of his engineering career on ground effect, which is the demonstrable fact that a wing generates more lift and experiences less drag when it’s in close proximity to the ground than it does while high in the air. In general aircraft don’t take advantage of it when cruising because of the increased risk—the ground is right therein the event of something going wrong, but Alexeyev was an expert on hydrofoil design and felt that the problem was sufficiently mitigated by flying over water to be worth attacking. Between the Khrushchev era and his death in 1980 he built his largest ekranoplan (“screen plane”), the so-called “Kaspian Monster” (KM: korabl maket, “test vehicle”) which met a watery fate in an accident not long after Alexeyev’s demise.

If you’re the sort of person who’s interested in Soviet crewed spaceflight you’re probably the sort of person who finds Russian ekranoplans and hydrofoils interesting too, but you may be wondering where the connection is between the two that would cause the latter to show up on a  blog devoted to the former. The intersection of this particular Venn diagram is the Albatros, outlined in a remarkable letter to the British Interplanetary Society’s Spaceflight magazine, published in 1983.

Long-time readers will recall that the Soviet space program was in disarray for much of the early 1970s, with 1974 being the year of crisis. Vasili Mishin was replaced by Valentin Glushko as the man in charge, and officials higher than him forced a change in focus from Moon missions to a space shuttle and space stations. For a period of time everything was in the air, and as was endemic to the Soviet space effort various other empire builders tried to get themselves a piece of the pie.

The design bureau of OKB-51 lurked on the edges of the Russian space program right from the very beginning, but never managed to convert its expertise in high-performance aircraft into any concrete projects. In 1974 they teamed with Alexeyev’s Central Hydrofoil Design Bureau to make a claim on the shuttle project, as at the time it was not yet settled that the Soviets would emulate the American Space Shuttle closely to produce Energia/Buran (consider, for example, Glushko’s MTKVP, which also dates to the same time). Their proposal was named Albatros, and it’s, so long as the source, space historian and writer Neville Kidger, got his Cold War information right, the only triphibious spaceplane ever proposed, requiring both water and air to get into orbit and land for its return.

One can see what, perhaps, they were thinking: margins are punishing on space vehicles, and it takes only a little inefficiency to turn a potentially useful craft into something that lifts a uselessly small amount of mass to orbit. Using aircraft as airborne launchers has been mooted a few times, why not use a ground effect “aircraft” to squeeze a little more oomph into your package?

The result was a three-stage vehicle, the first of which would have been a roughly 1800-ton, 70-meter long, Alexeyev-built, hydrofoilnot a full-fledged ekranoplan, alasthat could be thought of as a maritime version of the Space Shuttle’s external fuel tank. It would carry 200 tons of LOX and LH2 to feed the initial boost of the second stage’s motors.

Mounted on top of the hydrofoil, the estimated 210-ton second stage would use the first’s fuel to get up the whole arrangement up to 180 km/h over the course of 110 seconds, using the Caspian Sea (or the Aral or Lake Baikal) as a runway. Then it would disconnect and launch itself off the now-empty barge to consume its own propellants. This stage would be a high-speed reusable winged rocket plane/booster from Sukhoi that would lift the third stage—the actual spaceplane, also from Sukhoi—to a high altitude. There the latter would kick itself into orbit while the booster coasted into landing, possibly under pilot control; sources don’t say if the booster was to be manned, but with Sukhoi’s background it likely was.

The final stage was a tail-less rocket plane, about 80 tons in mass and 40 meters in length, so comparable to the American orbiter. It was estimated to have 30 tons of payload to LEO and a crew of two. It would have been larger than but was otherwise similar in appearance to some iterations of the Hermes shuttle, or to a lesser extent the later Russian/European Kliper. It was the most run-of-the-mill part of the whole vehicle, its design actually being closer to the American shuttle than the MTKVP. The air-based launcher was a radical approach, if not unique, but the underlying hydrofoil was the truly surprising suggestion.

It’s not difficult to see why the idea never went anywhere. Even putting aside the two partners’ inexperience with designing spacecraft, their proposed setup is ludicrous on its face, with tons of volatile propellant skimming over the water at triple-digit speeds, regardless of what its engineers might have actually calculated and put to paper. The likes of Dmitri Ustinov would have blanched if asked to sign off on it, as the country’s internal politics made Soviet decision makers inherently conservative. If they were eventually driven to insist on a close analog to the Shuttle over other proposals, one can only imagine what they thought about this one.

Sources:

“Albatros”, Mark Wade, http://www.astronautix.com/a/albatros.html.

VR-190: Stalin’s Rocket

GPN-2002-000162

Diagram of the VR-190’s capsule. NASA image via archive.org

What it was: An attempt to turn a Soviet copy of the V-2, the R-1, into a suborbital manned rocket.

Details: After the fall of the Third Reich and the scattering of its rocket scientists to the winds, all three of the main Allied powers found themselves in possession of at least a few V-2 rockets. All of them then considered putting a man on top of one for a suborbital flight. In the case of the British and the Americans this was barely more formal than someone saying “Hey, why don’t we put a man on top of one of these things?”, but in the Soviet Union a considerable amount of design work was done before the project eventually came to a halt.

To some extent this was because the Russians did far more work with the V-2 than the other two powers. They managed to retrieve only a very few German-built V-2s and so set about learning how to build them on their own. In 1951 the home-built R-1, a copy of the V-2 with a few local improvements, was accepted into the Soviet military as their first operational ballistic missile. This work was done by OKB-1 under Sergei Korolev and lead quickly to the R-2 (AKA the Scud), the abortive R-3, and eventually the R-7 that was used to launch Sputnik and Yuri Gagarin into space.

The R-7 was famously built to use a core engine with strap-on boosters (four in the case of the R-7), as opposed to the Americans’ pre-Shuttle tendency to use serially fired stages for manned flights. The initial Soviet studies on strap-on launchers were done by a relatively unknown GIRD member named Mikhail Tikonravov, who was one of the very few notable rocket engineers to escape the pre-War purges and so was well-positioned to work on Russian missiles as soon as the war was over.

His projects prior to studying the pros and cons of what he called “packet” launchers included the VR-190. As mentioned earlier, the US and UK never got very far into manned space travel based on the V-2 due to extreme skepticism on the part of the responsible parties in both countries. The USSR was the exception, and surprisingly Stalin was not only aware of it—Tikhonravov mailed a proposal directly to him in March 1946—the Soviet dictator specifically approved of it. The designer, who was Deputy Chief of NII-1 (“Scientific Research Institute-1”) worked on this goal until 1949.

Dubbed the VR-190 (Vysotnaya Raketa, “High-Altitude Rocket”), Tikhonravov’s variation on the V-2 took advantage of Russian work (partly done by the German engineers they had dragooned back to Kaliningrad) on separable nosecones for the V-2 that had been incorporated into the R-1. The German missile had problems with falling apart as it re-entered the atmosphere and the Russians and their Germans had realized that they could save weight and trouble by only worrying about the payload — the rocket itself had done its job by the time the dive back down arrived, and it could be dispensed with.

With the idea of a nosecone that could be swapped in or out now floating around, there were several different ideas put forward for how this capability could be used scientifically. In the early 1950s OKB-1 would fire R-1s into suborbital space with scientific instruments, gas sampling containers, and “biologicals” on board; the first living things to go to space and return were a pair of dogs, Dezik and Tsygan, who went up on July 29, 1951 (Charmingly, Tsygan was adopted as a pet afterwards by physicist Anatoli Blagonravov, later a negotiator for the Apollo-Soyuz Test Project. Dezik, unfortunately, did not survive his second flight).

The VR-190’s payload was to be a manned capsule containing two cosmonauts—a word coined by Tikhonravov—seated side-by-side but facing in opposite directions. Its mission was not even suborbital in the technical sense that it would not have been launched any distance downrange. Rather, it was a pure vertical hop, aimed for maximum height at the cost of all else.

Perched atop the modified R-1, the cosmonauts would have ridden up to 190 kilometers before their capsule separated from the main body of the rocket. A parachute would have returned them safely to Earth, where dry land was the target. A moment before actual landing a probe on the underside of the capsule would detect the ground and fire retrorockets to counter the last of the craft’s speed—a tactic familiar from actual Soviet and Russian craft built later, first conceived of here.

What happened to make it fail: Despite Stalin’s approval, it seems to have bogged down in bureaucratic rigmarole and never got the attention or funding it would have needed. Certainly many of the people to whom Tikhonravov reported were skeptical of spaceflight, and in the atmosphere of terror that Lavrenti Beria cultivated in the 1940s USSR few were willing to stick out their necks, not least because there’s evidence that Beria himself was not sold on manned spaceflight. A few months after making his proposal Tikhonravov was moved out of NII-1, where he was under the control of a doubtful Ministry of Aviation, to the newly formed NII-4. This new bureau’s job was to develop theoretical concepts for military use of rockets but he was assigned quite strictly to that. He and his team continued to work on the VR-190 in his spare time.

By 1949 the focus of biological experiments had been shifted to the aforementioned dogs, and Stalin’s interest had drifted toward the far more sophisticated Sänger-Bredt spaceplane and sent Mstislav Keldysh on a quixotic quest to build one for the Soviet Union. Tikhonravov’s attempt to refocus it back in early 1950 was slapped down by the powers-that-be, who felt he should stick to what he had been asked to think about. Tikonravov was demoted from his position at NII-4 and eventually wound up at OKB-1 working under Sergei Korolev as a spacecraft designer. His previous work was instrumental to getting approval for launching Sputnik 1 in 1957, and he was a key person in the design of “Object D”, later dubbed Sputnik 3, which followed Sputnik 1 and Laika’s Sputnik 2 into space.

What was necessary for it to succeed: At the time rocketry was #2 on Stalin’s list of important military goals. Developing nuclear weapons was #1 and rocketry research was relatively focused on military applications of fission and then fusion bombs. The key turning points both came in 1953: Stalin’s death in March, and the first Soviet thermonuclear bomb test on October 12, 1953. The Soviet leadership was thrown into fratricidal chaos internally and stasis externally, not least because of Stalin’s micromanagement—for example, Georgy Malenkov, one of the initial triumvirate which took over, was ostensibly on the committee controlling the development of ballistic missiles prior to Stalin’s death but in practice he actually knew very little about the projects he supposedly oversaw.

With the pressure off to catch up with the United States in nuclear arms after the successful test, missiles to deliver them moved to the top of the Soviet wish list at the same time the grip of the country’s leadership had faltered enough to let the designers work on space projects that would have got them shot under Stalin and Beria (the latter judicially murdered himself in December 1953).

So the key to getting the VR-190 into space with its two cosmonauts aboard might be to have Stalin die (or be assassinated) not long after he approved Tikhnonravov’s initial proposal. The new leadership would be inclined to let things roll on their course for a while until more sure of themselves (as they did in real history) and the shakeups of the Politburo’s civil wars might have got pro-rocket Ministers in place of the pro-aviation ones that stopped Tikhonravov in 1949-50. This wouldn’t have been a sure route, but it would at least open up possibilities that did not exist in the late Stalin-era USSR.

That the VR-190 could have been successful is fairly clear given the pace at which events moved from 1953 to 1957. The R-1 was much less powerful than the R-7, but then the R-7 was much above the requirements of a suborbital flight. Reaching space in a vertical shot is much easier than orbiting the Earth, yet Vostok 1’s historic flight was a full orbit  launched on top of a slight variant of the very rocket which produced Sputnik 1 in 1957. The VR-190 would have been dangerous (two of its eight dog flights ended in death) but the USSR or, for that matter, the US or even UK with their captured V-2s, could have grabbed the first laurel of human spaceflight sometime about 1951, more than half a decade before the Space Age actually began.

Sources: Challenge to Apollo, Asif Siddiqi. “The Man Behind the Curtain”, Asif Siddiqi, published in Air and Space Magazine, Oct.-Nov. 2007. “Tikhonravov”, Russian Space Web, Anatoly Zak.

The Reusable Nuclear Shuttle: To the Moon, Again and Again (Integrated Program Plan, Part II)

Sample Nuclear Shuttle configurations

A 1971 slide prepared by Marshall Space Flight Center showing an unloaded Nuclear Shuttle (top) and two configurations with a various components docked to its forward end (middle and bottom). Public domain image by NASA via Wikimedia Commons. Click for a larger view.

What it was: The solution NASA envisioned to the difficulty of getting large payloads to anywhere much beyond Earth with mere chemical rockets. Something like a dozen of them would serve as the brute force “trucks” of the American space program beyond Low Earth Orbit.

Details: We’ve already discussed some aspects of the Integrated Program Plan, NASA’s ambitious 1969 proposal to follow up the Apollo Moon landings with a new goal and new technology. The new goal was a manned Mars Mission, but the new technology had two particular pieces that would do the grunt work of building a space station and a Moon base as intermediate steps to the red planet: a reusable orbiting space plane (not yet dubbed the “Space Shuttle”) and the Reusable Nuclear Shuttle (RNS), many of which would have been built. It would have been the space plane’s role to get astronauts and cargo into low Earth orbit, while the RNS would have been used for the “high frontier”, so to speak. If something was going to go higher a few hundred kilometers, it would be offloaded from the spaceplane to an RNS, and then sent on its way—potentially to the Moon, or even beyond.

The RNS was suited for this task and similarly restricted from landing on Earth for one reason: their engines were given oomph by a nuclear reactor, but approaching one too closely at the wrong angle would expose a person to a fatal dose of radiation.

Start with the Nuclear Shuttle’s advantages. A variety of factors affect the power of a rocket, but the dominant number is the specific impulse (ISP) of the propellants it uses (to be precise, it’s a proportional measure of how much propellant the rocket has to use to add or subtract a given amount of velocity, though confusingly its unit is the second). With variations due to several other factors, rocket engines that use UDMH and N2O4 produce a specific impulse in the neighbourhood of 280 seconds, while LOX/LH2 is much more efficient at around 450 seconds (the low density of liquid hydrogen hamstrings it, though, so it’s often only used in upper stages where the rocket is already well underway and moving fast).

Unfortunately, all chemical fuels with a better ISP than that are either fantastically explosive, corrosive, toxic, or some hellacious combination of all three of those characteristics. Even at that, the best known ISP ever obtained (with a tripropellant of lithium, hydrogen, and fluorine) is 542 seconds.

Ultimately this because chemical propellants depend on chemical bonds, and there’s only so much energy you can contain in those. Quite early on rocket engineers realized that a good way to higher ISP was to use a different source of energy. In the absence of real exotics like nuclear fusion and matter/antimatter reactions, nuclear fission was the way to go. Hydrogen heated by a nuclear reactor can have an arbitrarily high ISP; it’s just a matter of how much heat one can get away with before the physical components of the engine are melted away.

When John F. Kennedy made his famous 1961 speech that started the race to the Moon he made a largely-forgotten reference to the Rover nuclear rocket, a contemporary project that was working on a preliminary nuclear-fission powered rocket. This in turn led to successively more advanced nuclear engines with the colourful names KIWI, Phoebus, and Peewee-1. By the end of 1969, NASA had a design for a functional nuclear rocket engine, the NERVA-2.

NERVA-2 would have had a specific impulse of 825 seconds in vacuum, and be able to burn for 20 minutes and produce 399.5 kilonewtons of thrust. Compare this to the J-2, NASA’s comparable workhorse engine (used on the second stage of the Saturn V, among others): it produced 486.2 kN of thrust, but was far less efficient at just 421 seconds of ISP. Accordingly, even though the NERVA-2 was far larger and heavier than the J-2 (having an entire nuclear reactor on board does that), the savings on propellant mass and the mass of the tanks needed to store it would make any spacecraft using one smaller than the same spacecraft based around a J-2.

Getting to the Moon is considerably more difficult than getting to orbit—you need to add another 3 to 4 kilometers per second to your orbital speed—and so the radically reduced fuel consumption of a NERVA-2 engine was very useful. Enter the Reusable Nuclear Shuttle. This was a conceptually simple ship: a single large fuel tank containing LH2 would have a NERVA-2 attached to one end, while the other had a docking adapter that could connect up to a variety of payload containers. Attach your payload, light the engine, and the RNS would push the payload into high orbit, to the Moon, or even beyond. Ideally you’d also put it on a trajectory which would let it return to Earth orbit, as the NERVA-2 was designed for ten round trips before it would be unsafe to light up again.

The disadvantage of the RNS lay in the radiation environment it produced. The rocket’s exhaust was only marginally radioactive and so arguably acceptable to allow on a launchpad, but in the event of a containment breach on the ground or, worse, in the air the engine would have sprayed uranium all over the environment. Even in the heady days of the late 1960s this was considered too risky, so the plan was to launch an RNS on top of a Saturn rocket using conventional fuels—if the Saturn blew up, the reactors were sufficiently ruggedized that they could survive the accident intact and fall into the ocean safely (by 1960s standards anyway).

What was more problematic was the NERVA-2 in orbit. Once the reactor was up and running it needed a great deal of shielding to protect approaching astronauts. As shielding was heavy, the RNS wasn’t going to have much of it. Instead the approach chosen was the have a “shadow shield”, where the propellant tank and any propellant aboard would provide most of the shielding. This meant that humans getting close to an RNS had to approach it from the front at a fairly shallow angle, using the bulk of the RNS to cover them from the reactor. If they approached from the sides or, God forbid, the aft where the engine was located they were assured of radiation sickness or death. Even on top of the RNS, a crew member would get about the recommended annual maximum radiation dose each time the engine fired.

Nevertheless, the advantages of the RNS outweighed the disadvantages in NASA’s collective mind, and the Integrated Program Plan called for it to be the workhorse of the space program beyond Earth orbit. Each would be used up to ten times (with refueling gingerly taking place after each use), after which it would be discarded in a high orbit due to its extreme residual radioactivity. With it, crews and payloads could be sent to the Moon and returned, and ultimately the American manned Mars mission craft envisioned for the early eighties would be perched on top of three of them.

What happened to make it fail: As with much of the IPP, the nuclear shuttle never got built because of a combination of disinterest from the Nixon administration and the falling budgets that that caused. Of all its parts, only the re-usable Space Shuttle and its rocket stack made it off the ground.

The RNS has its own particular story embedded in this larger tale, though. For many years the nuclear rocket engine program had been championed by New Mexico Senator Clinton P. Anderson, as much of the work on NERVA had been done at Los Alamos. Just as NERVA-2 was ready to become operational he became seriously ill and unable to press his case as much as he had in the past. The White House convinced Congress to pull the plug on the nuclear rocket on the grounds that it would be the basis of a manned mission to Mars, a goal about which Congress was quite negative at the time. The plan was that the freed-up funds could be used for the more-practical Boeing 2707, a Mach 2.7 supersonic commercial passenger plane similar to the Concorde or the Soviet Tu-144. Ironically, Anderson had enough clout remaining in the Senate to apparently engineer a 51-46 vote against moving ahead with that project; the House of Representatives soon followed. While the exact maneuvering involved has never been documented, the vote was widely considered retaliation for the cancellation of NERVA.

Regardless, with its funding quickly dwindling despite Congressional efforts to keep it going, NERVA was cancelled on January 5, 1973, and the Reusable Nuclear Shuttle was dead.

What was necessary for it to succeed: Like much of the Integrated Program Plan, the RNS was doomed by the political currents in Washington, within NASA, and in the general public. When it came down to picking something to move forward on NASA picked the Space Shuttle and the hope that one day they would be able to move on to a space station from there. The RNS ranked third (with the Moon base and Mars landing fourth and fifth) on their priority list, and they even tried very hard to claim that without the Space Shuttle they would not be able to get any nuclear shuttles into space. This was not actually true as the initial plan to use NERVA involved an upgraded Saturn rocket, but it was a measure of NASA’s determination to do anything to get the Space Shuttle built.

Ultimately that’s the main route to getting the RNS into the sky. NASA engaged in a great deal of internal debate from 1968 to 1970 over whether to continue with ballistic capsules or move on to a reusable, winged orbiter. Related to this was the debate over whether or not to focus on Earth orbit as a testing ground or push hard into the rest of the solar system. If both debates had gone the other way, a nuclear engine would have been very attractive to planetary mission planners and the money would have been there to continue with NERVA and the RNS–despite Congress’ objections to Mars missions, the presidential Office of Management and Budget had considerable discretion to ignore how it was told to allocate the money it received until a post-Nixon backlash in 1975.

Instead the arguments settled around a winged orbiter and sticking close into Earth unless the mission was unmanned, and we got the space program that we did from 1975 to the first decade of the 21st century. Nuclear rockets were revived for a short while during the days of the Strategic Defense Initiative’s Project Timberwind, but again it never came to anything.

Even if the RNS got built, there’s the possibility that it would have been much restricted in use or even cancelled outright no matter what successes it scored. The Three Mile Island accident in 1979 soured the American public on nuclear power in general, and after the Challenger explosion in 1986 NASA became very leery about dangerous payloads–for example, deciding against the planned Centaur-B booster that was to be orbited aboard STS-61-G later in the same year for the purposes of getting the Galileo probe to Jupiter. While both were specific incidents, they were each the culmination of long-term cultural trends that likely would have choked off the use of the RNS no later than the mid-1980s, and possibly earlier if one of them was involved in an accident.

FLO: The First Lunar Outpost (Space Exploration Initiative, Part I)

FLO Base Lander

One of two landers for the First Lunar Outpost, this an unmanned one with an adapted Space Station module on top for use as a place to live during the mission. The astronauts would arrive at roughly the same time aboard a manned lander. This picture is somewhat incorrect in that the real lander would have had two large solar panels stretching to the right and left. Public domain image from NASA.

What is was: A 1992 benchmark mission for NASA to return to the Moon, using expendable launchers and a direct descent lander, and build a small periodically-inhabited lunar base on the Mare Smythii.

Details: Early during the presidency of George H. W. Bush, the White House directed NASA via Vice-President Dan Quayle to come up with a plan to go to Mars—a goal announced to the public as the Space Exploration Initiative (SEI). To say that NASA botched this opportunity is to put it mildly.

Their (admittedly non-mandatory) orders were that NASA should come up with a plan that could get to Mars relatively cheaply, probably using technology that had developed since the end of Apollo. Instead they put forward an obvious relative of von Braun’s 1969 Mars Expedition, ditching the nuclear rockets but otherwise following the path of building a big space station, a permanent Moon base, and then finally moving on to Mars. The total cost of the program was estimated to be about US$540 billion over about thirty years—or, to put it another way, a rough doubling of NASA’s annual budget through the next several presidential administrations. This was political suicide and the whole thing collapsed in acrimony almost the moment it was put forward. Richard Truly’s career as NASA administrator came to an end in large part because of the fiasco and he was replaced by Dan Goldin in 1992.

Goldin’s mantra for NASA was famously “faster, better, cheaper” and he arranged for another study that would attempt to recover the manned lunar exploration part of the SEI. It was explicitly to be based on new ideas from the so-called Stafford Report (properly known as America at the Threshold: Report of the Synthesis Group on America’s Space Exploration Initiative) from the previous year. Out of this study grew the First Lunar Outpost (FLO) proposal.

Comet rocket for FLO

An artist’s rendition of the proposed HLV for the mission, referred to informally as Comet. Public Domain image from NASA.

The first step to the outpost was literally getting there. The initial SEI plan had foundered in part because of its allegiance to the Space Shuttle which, as it could lift only 25 tonnes to LEO, meant that NASA needed to build their Moon craft in Earth orbit; that in turn required a space station. FLO was based on a return to an expendable launch vehicle, and it would have been a monster: the core of the launcher would either be an all-new rocket or a stretched version of the Saturn V (to the extent that that program could be revived 20 years after its end); either would have been flanked with two boosters. Its resulting payload to LEO was to have been in the vicinity of 200 tonnes. Contrast that with the Saturn V at 118 tonnes, or 88 tonnes for the Energia.

This massive increase in capability was to be used in two ways: the Moon craft would not have to reconfigure itself in Earth orbit like the Apollo arrangement did, and it would land directly at its destination on the Moon rather than sending down a landing craft followed by a lunar orbit rendezvous before returning to Earth. As well as making the missions safer by allowing more ways to abort and opening up more of the lunar surface for exploration, this simplicity was believed to be the route to a cheaper mission despite the upfront cost of the rocket that launched it.

FLO-spacecraft

The FLO spacecraft on top of its TLI stage in Earth orbit. Public domain image from NASA.

Nuclear thermal engines were studied for the trans-lunar injection stage of the FLO spaceship, but it was assumed that it would probably use a J-2S LOX/LH2 engine—essentially the same as was used by the Apollo S-IVB injection stage, though slightly upgraded to use a de Laval nozzle. The lander itself would have used four RL-10s, repurposed from the tried-and-true Centaur.  Again, these choices were made with an eye to saving money by using what the American aerospace industry already had to offer.

The direct-descent/direct-return profile of the actual landing forced the lander to be quite different, though. Admittedly a scaled-up version of the Apollo CM was perched on top of it, where it would carry four astronauts in the relative comfort of 11.3 cubic meters—somewhat larger than the old CM and LM taken together. Below that, though, was a much bigger spacecraft.

It would have packed no less than ten propellant tanks, four smaller ones in an upper tier for the ascent stage, and six larger ones underneath for the lander itself. Sitting on a relatively robust landing truss and four very long legs the whole arrangement would have been 56.7 tonnes with propellant, which is more than four times the mass of the Apollo LM. It would have towered 14.1 meters above the lunar surface, and been 18.8 meters from landing-leg foot to landing-leg foot.

Another big change from the Apollo program was actually a return to what had been planned for the original Moon landings post-Apollo 20. A second, unmanned lander would have been sent prior to the manned one and landed within an easy Moon rover drive, no more than two kilometers. Its entire ascent stage would be swapped out and replaced with a 35-tonne habitation module made in the manner of a Space Station Freedom module with as few changes as possible—again as a nod towards cost.

Inside-FLO-base

A sketch of the interior of the FLO habitation module on top of the unmanned lander Note the solar panels. Public domain image from NASA.

This module would have been the actual base. The crew of the manned mission launched in tandem with it would live there for 45 days, exploring the region within 10 kilometers using the aforementioned rover driven by astronauts, and up to 100 kilometers driving it by remote control from the habitat. The explorers would then return home to Earth but the base would not be closed up permanently. Powered by two solar arrays that brought the width of the base craft to just over 41 meters, the intention was that further groups of astronauts could be landed nearby as often as every six months and would find themselves with usable living quarters right away.

flo-lander-ascent

Leaving the Moon in the Ascent/TEI stage, leaving behind the landing stage. Public domain image from NASA.

Once the lunar surface mission was over, the astronauts would return to their original landing craft. Its central stack would ignite a hypergolic N202/MMH engine (hydrogen being too tricky to hold on to for 45 days on the lunar surface) and head directly for home. The final twist on the Apollo mission design would have seen the FLO capsule land on dry land, rather than splash down into the ocean.

By sticking as much as possible to technology they already had, or at the very least were already developing, the cost of the project to the end of the first landing mission was estimated at US$25 billion, with the unmanned base touching down around 2000 and the manned follow-up soon after. Just over half of this money would be for the development of the launcher and building three rockets. Even making allowances for the inevitable cost and schedule overruns, it was a remarkably different result from the original SEI.

What happened to make it fail: George H. W. Bush lost the 1992 presidential election and the Clinton administration was noticeably less interested in manned space exploration for its own sake. NASA reoriented itself toward keeping people in LEO, primarily building what had now become the International Space Station, and unmanned space probes beyond Earth orbit.

Extended manned lunar missions did creep back onto the agenda over the next few years, particularly as part of George W. Bush’s “Vision of Space Exploration” which pictured them as a test-bed for an ultimate Mars mission. But the discovery of water ice at the Moon’s south pole by the Clementine satellite in 1994 changed the nature of all future Moon base proposals by slewing them heavily towards using that water. Despite its generally innovative approach to a lunar landing, the First Lunar Outpost turned out to be the last gasp of an older paradigm for exploring the Moon.

What was necessary for it to succeed: This one is more speculative than most, but it’s interesting to consider the First Lunar Outpost in terms of what happened to Space Station Alpha in the same time period. The station came perilously close to cancellation and was only saved by a foreign policy decision: to turn it into the International Space Station, specifically in partnership with Russia in an attempt to absorb the time and skills of the Russian space engineers freed up by the collapse of the Soviet Union.

If you were looking to start an American make-work project in 1993 that capitalized on Russian expertise, a space station made the most sense. After all, Mir was beyond anything the United States had ever accomplished. But it’s not too hard to picture the busy-work being fulfilled by a different major space program. Since a manned Mars mission was out of the question due to expense, the relatively cheap First Lunar Outpost might have been the choice if the Clinton White House had been more interested in the inspirational side of space exploration than its nuts and bolts. They wouldn’t have been the first administration to feel that way.

Energia: The Last Big Rocket

energiya-buran-launch

A rendering of the Energia rocket launching its primary payload, Buran. Unlike the American shuttle stack, the rocket could be launched on its own, and was in the same class as the Saturn V. Image source and copyright status unknown. Please contact the author if you know of its origins. Click for a larger view.

What it was: A Soviet super-heavy lift launcher. It was one of the three most powerful rockets ever built, in the same class as the Saturn V as well as the ill-fated N1 it was partially intended to replace. Its other main role was to act as a booster for the Soviet space shuttle, unlike the American one which got itself to space using its own engines fed by its large external fuel tank. Though it did go to space twice in 1987-88 it qualifies for this blog because it didn’t fly any more after that, despite being intended as the heavy-lift backbone of the Soviet Union for well into the 21st century.

Details: For about twenty months after taking over TsKBEM (the former OKB-1) from the disgraced Vasili Mishin, Valentin Glushko worked toward a lunar base centred on a derivative of the Proton rocket, a design of Vladimir Chelomei’s using hypergolic engines designed by Glushko.

By early 1976, however, Glushko had been told by Soviet leadership to stop work leading to the Moon and instead focus on a Soviet space shuttle in response to what they perceived as the military threat posed by the US’ own Space Shuttle. While the eventual Buran shuttle would bear a strong resemblance to the American orbiters, Glushko made one major change that let him keep his Moon base alive surreptitiously.

In the American Space Shuttle, two strap-on boosters helped pushed the shuttle stack to 46 kilometers high. But some of the thrust up to that level, and all of it from the moment of booster separation, came from engines on the aft end of the Shuttle. In other words, the Shuttle was at least partly its own launch vehicle, while the external tank to which it was attached was not in any way a rocket. It existed solely to carry fuel for the Space Shuttle’s main engines.

Glushko chose instead to build Buran with no engines at all. It was solely a glider for returning to Earth, while it was lifted into orbit by engines on the end of what superficially appeared to be a copy of the US Shuttle’s external fuel tank—but was actually the Energia rocket. In other words, the Soviet Union’s chief designer hid a Saturn V-class booster, potentially useful for his beloved Moon base, in his space shuttle system.

Energia began when Glushko took over TsKBM (in fact the name “Energia” was applied to the newly reorganized department as NPO Energiya long before it was given to the rocket) and brought with him his new RLA (“Rocket Flight Apparatus” in Russian) rocket designs. In the early 1970s the Soviet Union had no less than three active launchers, discounting the N1—R-7 derivatives, the Tsyklon, and the Proton. All three were different from one another in design and construction, and the cost of running them were accordingly high. For the third generation of Soviet launch vehicles the requirement was to build light, medium, heavy, and super-heavy launchers from one common set of components, and the RLA was Glushko’s proposal to meet this. Of the various designs, the super-heavy RLA-135 is the one that interests us.

The RLA series was passed over in favour of the Zenit rockets of the Yangel Design Bureau but Yangel didn’t have a super-heavy solution, stopping instead at the “medium” level and leaving an opening for Energia. Glushko took his RLA-135 design, which had a large core rocket and strap-on boosters, and proposed it again with a modular version of the Zenit as the boosters and the core being a new rocket designed by his bureau. His suggestion was accepted and the Energia was born.

Glushko did have to take one other hit to his ego, though. For years the Soviet space program had been hampered by the fact that he refused to go along with Sergei Korolev’s judgment that LOX and liquid hydrogen were the best fuels to use on a large rocket. The N1 accordingly had engines built by a far less experienced designer, Nikolai Kuznetsov, while Glushko focused on nitric acid and dimethylhydazine.

But while those propellants have the advantage of being dense and storable, they’re also not as powerful by weight and have the disadvantage of being a toxic disaster to clean up if a rocket fails. Furthermore, the Soviet leadership were interested in catching up with the United States in LOX/LH2 engines—the USSR had never built a large one, while the second and third stages of the Saturn V used them, as would the Space Shuttle Main Engine. Partly of his own accord but also because of this political pressure, Glushko had to concede in his ongoing argument with the eight-years-dead Korolev.

That said, he pulled it off. Over the course of the next ten years (which is long, but not too long: the Saturn V took a bit less than seven years from proposal to first launch) NPO Energiya developed the massive core stage of the rocket. The side boosters were relatively easier, being smaller and using the kind of LOX/kerosene engines that the USSR had plenty of experience with, so the entire rocket stack was ready to fly for the first time by October of 1986.

Unfortunately they didn’t have a payload for it. While there had been some problems developing the Energia, the Buran shuttle was having a far worse time of it and wasn’t anywhere near completion. Up to this point the name “Energia” had been applied to both the booster and the spaceplane taken together, but Glushko’s earlier misdirection came back to the forefront. The rocket didn’t need to wait until its other half was ready. As it entered its last year of development, the decision was made to launch it first without Buran.

Between the fall of 1985 and fall of 1986, a new payload was quickly whipped up named Polyus. It was one of Vladimir Chelomei’s Functional Cargo Blocks, repurposed from a space station module and closely related to the Zarya module of the ISS. Polyus carried a wide variety of experiments, but its main purpose was to test the Skif-DM, a 1-megawatt carbon dioxide gas laser weapon that the USSR had been working on since 1983. Retrospectively this is less alarming than it seems, as the USSR had been hammering the US over the Strategic Defense Initiative and Mikhail Gorbachev was less than keen to risk the Americans finding out that his country was countering militarily; the Reykjavik Summit had ended in October 1986 with the two countries close to radical nuclear weapons reductions, and they would conclude the INF treaty in December of 1987. Various components of the laser were deliberately left out, leaving it with only the ability to track targets, and Gorbachev is reported to have banned testing of even that during a visit to Baikonur a few days before launch. From the standpoint of the rocket, however, Gorbachev’s visit is most interesting as it led finally to the formal naming of the launcher (as distinct from the shuttle it was supposed to launch) as Energia: it was painted on its side just prior to his tour.

The General Secretary’s misgivings notwithstanding, the first launch of Energia went ahead on May 15, 1987. During the first few seconds of its flight, before it cleared the launch tower, it tilted noticeably to one side but then corrected itself when the rocket’s attitude control system kicked in at T+3 seconds. From then Energia flew beautifully, watched only by a sole Soviet MiG as from the standpoint of the ground it quickly disappeared in low-hanging cloud. Its boosters were seen to separate correctly (though for this flight and the next they were not fitted with the parachutes that would make them recoverable), and then the core stage flew out of range of even the jet watching it. Upon burning out, it released Polyus and re-entered into the Pacific Ocean, as planned.

Polyus weighed 80 tons, and so to reach its useful orbit it had to fire a small rocket engine of its own after being released. To do so it had to rotate 180 degrees, and unfortunately for it a programming error made it continue to rotate as the engine fired—deorbiting it instead of pushing it higher. It too crashed in the Pacific.

While this was an embarrassing result, the rocket itself was a complete success. Work continued on Buran and the largely completed shuttle (while flyable, at the time it could generate only enough power for one day in orbit) was mated to another Energia and launched on an unmanned mission on November 15, 1988. Again, the rocket performed admirably (with a change in its own programming to prevent the alarming blast-off tilt) and this time its payload did too: Buran landed automatically at Baikonur after two orbits, three hours and twenty-five minutes later.

So by the beginning of 1989 the Soviet Union had itself what was at the time the most powerful rocket in production, and one that hasn’t been approached closely ever since. It could launch a space shuttle with a payload similar to that of the US’ orbiters, and if used as a rocket on its own could lift 88 tonnes into low Earth orbit or 32 tonnes to the Moon (compare to 118 and 45 for the Saturn V, and 92.7 and 23.5 for the N1 it replaced). Further development was expected to push this to 100 tonnes, and work moved forward to build a dedicated cargo pod rather than the cobbled-together Polyus to lift. A smaller version of the rocket dubbed the Energia-M, with one engine and two boosters, was underway too so that smaller payloads up to 34 tonnes could be lifted more cheaply.

What happened to make it fail: Clearly the collapse of the Soviet Union was the major cause. Just as the launcher was finding its legs the security concerns of being a superpower evaporated, as did money for any large-scale scientific missions it could have supported. There was also the problem that the Zenit-derived strap-on boosters were built by a company that was now in the independent Ukraine.

Even before that, though, Energia was already suffering from a lack of missions—if you’re not going to the Moon, lifting 100 tonnes to orbit is a bit superfluous. The shuttles it was primarily designed to lift had the same flaws as the American shuttle, and didn’t have the advantage of being the country’s sole launcher of note (as the US Shuttle did prior to the Challenger explosion in 1986).

NPO Energiya’s desperation comes through when you examine some of the missions they proposed:

  • Orbiting massive lasers to deconstruct oxygen in the upper atmosphere, for the purpose of rebuilding the ozone layer over the course of several decades.
  • Using it to build a Helium-3 mining base on the Moon—bearing in mind that Helium-3 is only useful in fusion power plants being developed by an international consortium that believes they’ll be ready to go in 2050.
  • Launching spent nuclear fuel waste into “graveyard” heliocentric orbits.

Ultimately it came down to a question of what it was supposed to do that couldn’t be done by smaller, cheaper rockets—each launch of an Energia cost $US240 million, even at the more favourable black market rate of the rouble to dollar in the late 80s. Even if launches were reserved for situations where only it was capable enough, just keeping the plant in place to build it would have cost a not-so-small fortune, which the Soviet Union didn’t have and post-1991 Russia most definitely didn’t have.

What was necessary to succeed: Keep the Soviet Union a going concern. This is difficult if one subscribes to the theory that the Soviet Union collapsed primarily because of financial pressures, because you can also reasonably say that Energiya/Buran was one of the main straws breaking the camel’s back. It was representative of the unchecked spending that killed the USSR and if the only way they could have continued would have been to not do this sort of thing.

On the other hand, one can reasonably argue that it was Mikhail Gorbachev’s reaction to the country’s finances that did the worst damage, and that the USSR could have limped along into the present day if the Politburo had come up with someone other than Gorbachev as leader following Konstantin Chernenko.

That solves the major problem with a large booster—that it’s not economically feasible to run one for anything other than special purpose missions. The Soviet leadership got the USSR into financial trouble by ignoring costs when it suited them, so Energia probably would have flown every now and then until the belated collapse of this postulated Soviet Union did finally occur.

Putting aside the more radical missions mentioned above, what would Energia been used for? Likeliest would be a space station built around one or more large modules, with other smaller ones being lifted by the Energia-Buran combination. Mir-2 was redesigned to be built solely from 30-ton modules as late as 1991.

Also possible was a smaller shuttle, OK-M2, which would have perched on top of the Energia stack rather than on the side. If the USSR’s leaders had reached the same conclusion about their space shuttle as many people did about the American one, it’s entirely possible they would have scrapped Buran and its follow-up orbiters, flown Energia as a cargo rocket for a while, and developed this smaller proposed shuttle as a replacement.

Glushko’s bet that the Soviet space program would go through a future shake-up, as it had several times before, was probably a good one too. While it’s obviously more efficient to design a launcher around proposed missions, past history shows that once a system is designed people start figuring out ways to use it. With a super-heavy launcher at hand, it seems likely that the Soviet Union would have eventually got around to a Moon landing, and only somewhat less likely that they’d have moved on to a Moon base. It really would have come down to a race between deteriorating Soviet finances (assuming that they couldn’t have come up with a softer landing at some later point than actually happened ) and the time when someone with power in the Politburo and Secretariat came to champion it. It would have been expensive and somewhat pointless, but that was the USSR’s modus operandi in any number of megaprojects. As it happened, Glushko died on January 10, 1989, less than two months after the Energia’s second, and last, flight, and before his bet had a chance to pay off.

Though none of this ever came to pass, Energiya does have a continuing legacy down to the present day. The Zenit rocket that shares so much technology with the Energia’s strap-on boosters became the cheapest of all current launchers (at about US$2500 to $3600 per kilogram). In 2010 NPO Energiya bought out its partners in the Sea Launch consortium that uses them, and is now in charge of firing them from their ocean platform as well as from Baikonur in Kazakhstan.

The RD-170 engine developed for the Zenit and the Energia strap-ons have also proven to be one of the best rocket engines ever developed. Its derivatives are still used on the Zenit, on a South Korean rocket called the Naro-1, the upcoming Russian Angara rocket family, and surprisingly even on the American Atlas V, which not only launched scientific missions like the Curiosity rover and the New Horizons probe to Pluto but also is used by the US military. Such is the difference between 1988 and the present day.

YouTube video of the first Energia launch, including its alarming tilt away from the launch tower before its attitude control system kicked in, can be seen here.

Army/RAND World-Circling Spaceship: War is Over, Space Is Just Begun

World-Circling Spaceship

Three views of the World-Circling Spaceship. On the left is the two-stage LOX/LH2 version, while in the centre is the more-developed four-stage LOX/Alcohol version. On the right is a view of the four-stage rocket as it might be assembled on the pad (support vehicle shown, far right). Images from Preliminary Design of a World-Circling Spaceship. Click for a larger version.

What it was: The first attempt to build a ship that could actually reach orbit by an organization that had the wherewithal to do it. Proposed in May 1946, the World Circling Spaceship was in fact two of them: a four-stage Liquid Oxygen/Alcohol rocket whose 500-pound (227-kilogram) upper stage would reach orbit, and an alternative two-stage LOX/Liquid Hydrogen rocket with a similar 500-pound upper stage. While primarily intended for unmanned payloads, putting a man into space with either was considered.

Details: The WWII German rocket team had a design, but no backing. Right after the war, the US Navy could have come up with the funds, but their design (actually several designs) to build a single-stage-to-orbit vehicle would never have worked—SSTO was beyond the technology of the 1940s.

The US Army Air Force, however, could have had both sometime immediately following the spring of 1946. In March they arranged for Douglas Aircraft to put together Project RAND to study intercontinental warfare by means of missiles. Their list of consultants was stellar, and even included Luis Alvarez, later much more famous for his paper proposing an asteroid strike as the cause of the extinction of the dinosaurs, and who would also be on the commission looking into the Challenger disaster.

By May 2, 1946 they had produced the first of what would be a very long line of reports from what would soon be the Rand Corporation. This one was devoted to artificial satellites and was called Preliminary Design of an Experimental World-Circling Spaceship. In it they studied the various issues standing between the present state of the art in rocketry and putting something into orbit, and they came to the conclusion that it could be done with 1946-era engineering. Working backwards from a goal of putting 500 pounds into orbit, they then proceeded to lay out two preliminary designs: a four-stage rocket using liquid oxygen and alcohol for fuel (the same fuels used by the V2 rocket) and an all-cryogenic two-stage rocket using liquid oxygen and liquid hydrogen. They also noted that their initial analysis’ conclusion that a rocket burning LOX/LH2 would be best if it had two stages had turned out to be wrong, and that if time permitted they would have redesigned the second concept to use three stages—not a bad result for 1948, as this prefigures any number of successful three-stage rockets developed since then.

The first actual all-cryogenic three-stage rocket didn’t come about until the Delta IV in the early 21st century, though, as liquid hydrogen is a bit of a bear to handle. In 1946 the knowledge of how to do so simply didn’t exist, so the alcohol fuelled rocket was considered the more conservative choice. As a result the report focused on the four-stage vehicle. Its length was 60 to 70 feet, and its width at its maximum was 12 to 14 feet. Altogether before launch (and including fuel) it would have weighed about 100 tonnes. Promisingly, this makes it quite similar in size to the two-stage Atlas B, a late 1950s rocket which had a payload of 70 kilograms.

A hypothetical launch of one of these rockets would begin on an equatorial Pacific Island, an idea we’d see again a few years later in the Army’s proposal to use Christmas Island as a spaceport for a lunar base. As with that future plan, this was to take advantage of a long downrange area clear of human life as well as getting the maximum possible boost from the Earth’s rotation.

The rocket’s four stages, from largest to smallest and first-firing to last, were charmingly named Grandma, Mother, Daughter, and Baby, with the final one being the orbiting section; in the cryogenic rocket, Baby was perched on one single large stage (unnamed in the report, but call it “The Mother of All Stages” if you like). Each of these stages would have been stripped-down accumulations of fuel and rocket engines with the exception of Baby; it was in charge of guidance for itself and any earlier stage still attached to it and firing, an approach taken by the Proton K/D used for the Soviet circumlunar Zond spacecraft.

Baby’s payload cone would have been 3 feet (0.9 meters) in diameter and 7 feet (2.1 meters) in length, with an internal space of 20 cubic feet (0.57 cubic meters), and the payload’s weight would be no more than 500 pounds. While the assumption was that at first the Baby would be unmanned, a short chapter in the report—almost an aside, not even two full pages long—suggests that this would be big enough for a man and a vivarium to provide him with oxygen. Considering that the cramped Mercury capsule, by far the smallest manned craft ever made, had 60 cubic feet (1.70 cubic meters) of internal space, this was probably optimistic.

Baby’s instrument payload would be swapped in and out to fill a variety of roles. Fundamental research of the near-Earth environment was first, and RAND also pointed out the usefulness of a satellite for geodesy, ultraviolet astronomy, and communications. They even discuss the advantages of a satellite in geostationary orbit, but never actually mention that there’s a considerable difference between 500 pounds to LEO and 500 pounds to 35,786 kilometers up. Probably bearing in mind that RAND was funded by the Army Air Force, they also suggested that Baby could watch the weather over enemy territory, act as a spotter for a nuclear missile in a co-orbit, and send back pictures after an attack to assess its effect. There’s also a surprisingly prescient prediction, eleven years before the Sputnik 1 flap, that Baby would provide value simply by existing, so that it could increase world opinion of the United States.

Though they do mention using television to return images, they considered how best to return Baby to Earth with photographs until such time as radio downlinks were up to the task (and not incidentally so our previously mentioned claustrophilic astronaut could come home). Their solution was to add small wings about 30 square feet in area (2.8 square meters) to the orbiting capsule. This is particularly interesting as it only highlights that Harvey Allen’s discovery that a blunt shape actually reduced re-entry heat with its bow shock—one of the fundamental discoveries of space exploration—was still several years in the future. Lacking that knowledge, RAND suggested that Baby could use its wings to slow the craft’s descent and cut the temperature that way. Both the wings and the capsule’s skin were to be made with stainless steel, which is worrisome in hindsight and appears to be the only place where their analysis missed out on a good understanding of what would be necessary to launch and retrieve an orbital satellite.

RAND suggested that, once given the go-ahead, designing and launching the World-Circling Spaceship would cost US$150 million and take 5 years.

What happened to make it fail: RAND’s report came out at a time when rockets were on the upswing with the Army Air Force (and the independent USAF that followed in 1947). In particular, they were headed by General Carl Spaatz, who was believer in the future role of rocketry in war.

He retired in February of 1948, however, and in October of the same year General Curtis LeMay took over the Strategic Air Command—and they were in charge of any Air Force missiles on American soil. LeMay was of the opposing school to Spaatz, and believed that the future of air war was in bombers. As a result his influence stalled any and all long-range missile projects, let alone one that was as speculative as an orbital launcher in a time of military budget austerity. The World-Circling Spaceship never gained the backing it needed, and soon withered away.

What was necessary for it to succeed: If it had been launched as designed, with stainless steel leading edges on the wings, the first few Babys may have made it into space but weren’t coming home. Apart from that, though, Preliminary Design of an Experimental World-Circling Spaceship is remarkably close to something that could fly considering that it was spec’d out in the Precambrian of the Space Age. With the right personnel (say if Wernher von Braun and his crew had gone along with the Air Force during the divorce from the Army) and someone other than Curtis LeMay in charge of the Strategic Air Command, it’s not hard to see an upgraded Baby beeping its way around the Earth by the end of 1952—a tight schedule, but not out of the question.

Even if they didn’t pull it off by then, after the election of Eisenhower in November of that year it’s an open question if the new president’s preference for civilian control of space exploration would have been enough to stop a project that hadn’t yet put something into orbit but was getting close.

SERV/MURP: Chrysler’s Space Truck

SERV-MURP

A schematic diagram of Chrysler’s SERV, an unusual VTOL Shuttle proposal to NASA in 1969-71. This is the final version, which could have mounted a crew capsule on top as shown here, or the capsule could have been swapped out for the MERP D-10, shown in the upper right. Image from the 1971 NASA document Project SERV Final Review. Click for a larger view.

What it was: A contender for the position of Space Shuttle at NASA. Unlike all the other possibilities raised during the Shuttle’s early development, it was a squat single-stage-to-orbit rocket booster that could get to orbit, release a small crew vehicle or cargo container, return to Earth ballistically, and soft-land on its original launch pad under its own power using jet engines. Both sections of the craft were reusable.

Details: A reusable Space Shuttle was originally a small part of a large post-Apollo NASA program, but over the years 1969-1971 it became progressively clearer that it was all they were going to get of that program. As a result the competition to build it was intense, with at least a dozen proposals—solicited and unsolicited—coming to them before they picked the “winged-orbiter-external-tank-two-side-boosters” approach that actually ended up getting built.

NASA had made it known that they were primarily interested in a winged orbiter, and so accordingly almost all of the proposals they received started from that base. But they didn’t explicitly rule out another approach. Chrysler produced the only notable proposal that came from outside the box.

The first iteration of the SERV/MURP came in November 1969, as part of Phase A of the competition. Chrysler had already done a lot of work for NASA, as they were the ones to build the Saturn I-C (the first and largest stage of the Saturn V), and with the Apollo program winding down they were looking to continue using the Michoud Assembly Facility in New Orleans that they’d been using to fabricate it. Their new proposal started from an interesting solution to a basic problem: two of the requirements for the shuttle, cargo capacity and cross-range capability, were at odds. Making a spacecraft better at either one would eat into the other. Chrysler’s idea was to split the two capabilities.

One module (MURP, the Manned Upper-stage Reusable Payload), was a manned orbiter outsourced McDonnell Douglas. It had a high cross-range ability but no real cargo capacity, while the other (SERV, the Single-stage Earth-orbital Reusable Vehicle) would be a single-stage-to-orbit booster with no real ability to move cross-range but with a huge cargo bay. The SERV and MURP would be mated, with the booster lifting the orbiter that was sitting on its tip. The booster would separate once in LEO, deliver its cargo, and then return to Cape Canaveral, while the orbiter could carry its people on their merry way to wherever it was they were headed—be it the proposed NASA Space Station, or to dock with injection stages headed for the Moon.

The MURP was fairly straightforward, a winged craft based on the HL-10 lifting body that NASA had been testing since 1966. There were actually two MURPs in the original proposal, one larger (the D-34) and one smaller (the D-10). The D-34 had 85 cubic meters of internal cargo space, while the smaller had only 5 cubic meters but made up the difference with a cylindrical cargo pod attached to its aft end. As the cylinder was a more efficient use of materials to enclose the space, the D-10 was considerably lighter than its bigger brother, 11,640 kilograms as compared to 16,150. Both would take two crew and carry up to ten passengers, and each had only a small amount of fuel—the SERV would get it into orbit, so it only needed to be able to go to a higher space station orbit on its own and perform a de-orbit burn. It would be covered with a spray-on silicone ablative skin (peeled off and refreshed after every trip) that would protect it from re-entry, and it would be able to land at any landing strip of reasonable length.

While the MURP was interesting, it was essentially just a very small version of what the other contenders for the Shuttle contract were proposing. Where Chrysler diverged most strongly from its competitors was with the SERV.

SERV would have been a tubby rocket, actually wider than it was tall; even with the MURP on the top of it, it would have only been 38.5 meters in height as compared to 28 meters wide.  In contrast, the actually-built Space Shuttle stack was 56.1 meters tall.

It had these measurements because it returned from orbit ballistically, and in fact resembled a gigantic Apollo capsule. This choice let the SERV benefit from the years of aerodynamic research put into that shape. Maximum heat was 1700 Celsius, on the uppermost edge of the blunt underside so it had a heat shield made of a silicone ablative material embedded in a metal honeycomb framework, individual sections of which could be swapped in and out.

Integral Aerospike Engine

The underside of the SERV, with its ablative heat shield and the aerospike engine that would fire the vehicle into orbit. Its concave profile would act as half of an exhaust bell, with the atmosphere as the other. This tuned the rocket’s performance as air pressure changed. Image from Project SERV Final Review. Click for a larger view.

To get into orbit, the SERV used another innovation, an aerospike engine. The typical exhaust  nozzle on a rocket engine is bell-shaped, which has the peculiar effect of making the engine most powerful at one particular air pressure. In other words, a rocket loses efficiency if it’s running at a height lower or higher than the one it’s tuned for—and of course an orbital rocket has to run through a whole range of heights from sea level on up. An aerospike, on the other hand, inverts the bell so that the concave curves are on the outside—now one half of the bell is solid, while the other half is formed by the atmosphere pushing against the side of the exhaust. This has the effect of continuously increasing the size of the imaginary bell as air pressure drops, an on-the-fly reconfiguration that keeps the efficiency of the engine up. On top of that, the SERV engine was going to be extremely powerful: 32 kilonewtons of force, compared to the actual Space Shuttle’s SSMEs at 1.9 kN (of which the Shuttle Orbiters had three), or even the most powerful liquid fuelled engines ever built, the Energiya rocket’s RD-170 at 7.9kN.

As a result it was so powerful that it could get into orbit by itself, even with the dead weight of a MURP attached to the top of it. In all it could lift as much as 39 tonnes to LEO with its single stage, about 40% of what the far more massive Saturn V could do. By the time of the Phase B proposal in 1971, Chrysler tried to make the SERV more attractive by adding to the possible modules that could be mated to its top. As well as a MURP they came up with a ballistic passenger capsule similar in size and shape to an Apollo CM (which was cheaper and smaller than even a D-10, and so the SERV could lift even more cargo), a high fineness ratio nose spike that would make an unmanned version of the craft more aerodynamic so that it could lift even more, and finally a nuclear-rocket launched upper stage that would be perfect for heavy Moon missions or manned trips to Mars.

On its ballistic return to earth the SERV could aim for an area about 15 kilometers in diameter, but unfortunately that was not accurate enough to meet NASA’s requirements. Undaunted, Chrysler proposed to put a ring of 28 jet engines with associated air intake doors around the edge of the SERV’s tubby body, inside its fairing so their profile wouldn’t disturb the booster’s smooth aerodynamics. These would kick in at 7600 meters of altitude, gulping air for oxidizer (and saving some weight by doing so, rather than using liquid oxygen) and push the SERV even closer to its goal. It could even hover for as long as its jet fuel held out. With the aid of the jets, it could get to within 75 meters of its aim point. Two special landing pads would have been built at Cape Canaveral right next to maintenance buildings on the shore of the Banana River so that returning SERVs could be whisked in for a post-mission checkup and refurbishment.

With that kind of performance, Chrysler pointed out in its Phase A proposal that the SERV would be within striking distance of providing a commercially viable suborbital “space airline” between major cities. Almost anywhere on Earth was forty minutes away. The main stumbling block was the cost of fuel, which brought the cost of a ticket to about US$33,000 (in 1969 currency). Chrysler somewhat arbitrarily felt that fuel costs would drop by three-quarters given the volumes that would be made to accommodate NASA’s requirement that any Shuttle would have to fly at a punishing schedule of roughly three times per month. Under those circumstances per-person costs would be only about US$10,900

If given the contract on January 1, 1973, Chrysler anticipated that the SERV/MURP’s first test flight would be towards the end of 1977, with the first operational flight in the first quarter of 1978. The total cost of flying four SERVs with three MURPs was pegged at US$10.01 billion, including operations through the end of 1986.

What happened to make it fail: The SERV, as proposed, had a number of small advantages over the spaceplanes that were submitted to NASA in the Shuttle competition, so it’s a little surprising that it got no traction at all. While it did make it through the Phase A first cut and into Phase B, it was never seriously considered.

The reason for this is speculative as it was the sort of thing that doesn’t get much documentation. Any project at NASA needed a broad constituency, and the SERV failed to make it off the drawing board because its peculiarities turned every possible supporter against it. NASA’s management had come to the conclusion that a large spaceplane was the way to go, and had only allowed other arrangements as a sop to due diligence. NASA’s astronauts didn’t like that the SERV (as ultimately envisioned in the Phase B proposal) could fly unmanned, cargo-only missions. And NASA engineers were concerned about the SSTO/Aerospike engine approach, which is very sensitive to weight and thrust. Marginal failures to meet the proposed engine characteristics or rocket weight can radically reduce the payload that can be carried to LEO, or even keep the craft from reaching orbit at all.

What was necessary for it to succeed: Besides its lack of support, the marginal failures just mentioned were the biggest problem the SERV/MURP had. As proposed, it looks a lot better than the Shuttle that was actually built, but of course the proposals for the actual Shuttle were far more comparable. Besides the aerospike engine, the SERV/MURP needed a number of technologies that were less well worked out than what went into the real Shuttle. If the real Shuttle went over time (it did, by several years) and budget (it did, by about a billion dollars) during development, what would have happened to the SERV, which even in its proposal was going to be more expensive and take longer? The MURP relied on an ablative coating technique that had been a near disaster the one time it was used, on X-15A-2, when that craft was nearly lost due to its ventral stabilizer nearly burning off. The SERV was enormously larger than an Apollo capsule—was it wise to be sure that it would have a similar heating profile?

Ultimately it’s impossible to be sure. It’s easy to take NASA to task for picking a conservative design that ended up being a far more marginal spacecraft than they had hoped, but the fact remains that with similar bad luck on the SERV they could have ended up with something that couldn’t fly at all—and they were being asked to spend the majority of their budget on it for a number of years. As they didn’t have the benefit of hindsight, it becomes easy to see why they went for the more conservative approach.

So to get the SERV to fly you need to make it so that it’s the less radical of the two options. The large winged orbiter of the Space Shuttle had the advantage of years of aerodynamic and thermal studies on other planes, such as ASSET/PRIME, the X-15, the HL-10, and the X-24A. Eliminate that and the orbiter suddenly becomes an unknown, at which point the SERV mated to a ballistic crew capsule (rather than the MURP) starts looking a lot more attractive.