TKS: Chelomei’s “Soyuz”

TKS spacecraft

A cutaway view of the TKS, with its associated Almaz station in the background. The VA is the white section at left, while the FGB is the green portion with the solar panels. Image originally published in Russian space magazine Novosti Kosmonavtiki.

What it was: A Soviet transport and resupply spacecraft for use with the Almaz space station.

Details: On February 7, 1991, Salyut 7 orbited the Earth for the final time, re-entering over southern Argentina and scattering its pieces over a wide area. Sixteen hours before this the Federation of American Scientists used Doppler radar to image it as it flew overhead, producing this remarkable picture. The murky image clearly showed the thing that made Salyut 7 most notable: on the top of the station proper was what was then known as Kosmos 1686. The Soviet station had been the first truly modular space station, and the Kosmos 1686 module had been docked to Salyut 7’s core module for more than five years. It was the harbinger of a new thing in orbit, space-based construction, that would be followed up in both Mir and the ISS. But as well as being the start of something it represented the end of one too: a crewed spacecraft that shares with the shuttle Buran the peculiar distinction of having flown, but never with anyone aboard.

The Kosmos label was used as a smoke screen for a variety of Soviet programs, and Kosmos 1686, along with numbers 929, 1267, and 1443 were used to hide perennial bridesmaid Vladimir Chelomei‘s answer to the Soyuz: the Transport Supply Spacecraft, or TKS, to use its Russian acronym (“Transportnyi Korabl’ Snabzheniia”).

The story of the TKS begins with the fallout of the battle between Chelomei’s OKB-52 and Sergei Korolev OKB-1 over the Soviet Moon program in 1964-65. Korolev won the war but died before he could make his victory complete. Chelomei’s contribution was greatly reduced but still consisted of the rocket for the the circumlunar Zond mission, the capsule for which was to be based on OKB-1’s tech. Chelomei reloaded for space stations and took the capsule he was developing for the LK-1 (his alternative circumlunar craft) and the LK-700 into the new project. The station was soon dubbed Almaz, and the LK-derived TKS was worked up to serve as a crew and supply ferry, much as the Soyuz and Progress do for the ISS.

The first thing to note is that the TKS would run both missions simultaneously, as opposed to the aforementioned ISS ships, which do one or the other. Despite countless upgrades over the years the Soyuz spacecraft is still rather cramped and there’s only enough room for astronauts or supplies, not both. As a result the Russians have been trying to replace the Soyuz for almost as long as they’ve been flying it, which accounts for the Zarya, the Kliper, the Energia/Buran shuttle, and the one they’re working on now, Federation, just to name a non-exhaustive few. The TKS was bigger—a lot bigger—and was Chelomei’s flying rebuke to OKB-1’s compact ship.

The TKS consisted of two modules. The first was the orphaned VA crew capsule (Vozvraschaemyi Apparat, “Return Vehicle”), which was attached to the new FGB support module (Funktsionalno-Gruzovoy Blok, “Functional Cargo Block”) which also served as a crew habitation module.

The VA was made of two components itself (three, if one includes the abort tower that was jettisoned after launch). The main portion was a truncated-cone capsule with a habitable volume of 4.56 cubic meters and a base of 2.79 meters. While originally designed for one person to make a loop around the Moon, as a LEO craft it was to hold three. Many commentators have mentioned the similarity in appearance of the VA’s capsule and the Apollo capsule, but the TKS’ was considerably smaller than the one used by NASA, which came in at 6.17 cubic meters and 3.91 meters. Where the VA diverged from Apollo even more sharply was in its nose module, the NO (Nosovoj Otsek, “Nose Compartment”), which took some of the support functionality out of the FGB support module and perched it at the front of the craft. Most notably this included the de-orbiting engines, but the communications equipment and the parachutes were loaded in it as well. Altogether this part of the ship weighed 3800 kilograms and was 7.3 meters long.

The rather beaky-looking VA was attached at its base to the FGB, which was a cylindrical module another 5.9 meters in length and 4.15 meters in diameter. While the VA was capable of being used as a complete craft it had endurance for only 31 hours and could carry only 50 kilograms of cargo. This was where the FGB picked up the slack. Sporting two solar panels with a span of 17 meters and a habitable volume of 41.08 cubic meters, it extended the TKS’ mission duration to a week, or 200 days if docked to an Almaz. Discounting the abort tower, together they made a 17,510 kilogram spacecraft which meant that it cleared the payload limit of a Proton-K (AKA the UR-500 designed by Chelomei’s bureau) by a couple of tonnes. With the joint capabilities of its modules, the TKS was specifically designed to be a “space truck”, ferrying passengers and cargo to a space station: the FGB’s maneuvering engines (which burned N2O4 and UDMH, like the Proton) would let it rendezvous with one in a higher orbit, and the docking adapter at its aft end would let it connect up. As the adapter took up the usual position of a rocket motor, the engines—four of them—were moved to the sides of the FGB, as were the engines’ fuel tanks.

The most revolutionary aspect of the TKS was what happened when it was time to go home. If so desired the entire TKS could disconnect and return its cosmonauts to Earth (in particular to a landing in the Kazakh SSR, softened by last-moment solid fuel rockets), with the FGB burning up. However, the other possibility was to use the VA’s autonomous capability to do the same while the FGB, which could be customized to one of many roles, stayed behind to be the latest module of the station.

What happened to make it fail: Chelomei’s efforts were an entirely parallel space program to the one being run by Glushko’s Energia, a military one comparable to the X-20/Manned Orbiting Laboratory on the American side. It ran into the same difficulty as the American one too: there turns out to not be a lot of military use for crewed spacecraft and stations. As Buran was also being built on the insistence of the Soviet military and it was tremendously expensive, the TKS and the Almaz stations were constantly in danger of being cut entirely or folded into the Buran/Mir ecosystem.

The TKS had a champion, Minister of Defense Andrei Grechko, who died in 1976. From then on Chelomei was unable to resist the pressure coming from Valentin Glushko and his champion Dmitri Ustinov, candidate member of the Politburo and then full member and Grechko’s successor as Minister following Grechko’s death.Ustinov is known to have had a personal grudge against Chelomei dating back to Chelomei’s temporary time in the sun under Nikita Khrushchev: he perceived Chelemei as an interloper from the Aviation Ministry whereas he represented the Artillery, under which ballistic missiles had been assigned for decades. Well before he reached the height of his power, in 1970, Ustinov as the Deputy Minister responsible for space travel had already ordered that Almaz be melded with the Salyut station project underway at TsKBEM (as NPO Energia was called at the time). From 1976 onwards he continued picking away at it, eventually leading to the TKS program being subsumed by Mir.

Before then, though, Chelomei’s bureau managed to get off six uncrewed flights and recoveries of the VA capsule beginning in 1976 and four uncrewed flights of an integrated TKS (VA with NO, and FGB) beginning in 1977. The spacecraft was tested and ready to go. But Ustinov had his way and there was never a full-up flight of a TKS with a crew aboard—three of the four TKS flights were in support of NPO Energia’s Salyut 6 and 7, while Kosmos 1686 in particular was modified so that it could not undock from Salyut-7, and its VA was gutted and filled with instruments. While two cosmonauts used the final TKS for some experiments during the Soyuz T-15 mission in 1986 it was merely a part of the space station at the time.

What was necessary for it to succeed: A lot of the projects we’ve discussed on False Steps are well down at the far end of the plausibility spectrum; “on paper only” is one of the most commonly used meta-tags around here. TKS is the antithesis of that. It was done, had been flown remotely, and needed only a final push to turn it into an operational system. As a result there’s several possible ways one can imagine that gets flying cosmonauts.

  • When OKB-1 was shaken up and Vasily Mishin relieved of his leadership, have Chelomei be the new leader instead of Glushko. This is not very likely because of Ustinov, but is the most direct route.
  • Have Marshal Grechko live and stay on as the Minister of Defense for a few years more than he did.
  • Have Minister Ustinov hold less of a grudge against Chelomei despite events in the Khrushchev era.
  • Have Energia/Buran be just slightly less of a money sink than it actually was.
  • Or give Energia some teething pains rather than two successful launches out of two tries, so that the Soviet leadership outside of Ustinov started looking more closely at the alternatives.

Any one of these would have been enough, and once flying it’s easy to see the TKS becoming the Soyuz replacement that Russia has been looking for since before the fall of the Berlin Wall.

As it was, the intriguing ability of the FGB to dual-purpose between being a spacecraft component or a space station component led to it alone becoming one of the cornerstones of space station construction from 1986 to the present day. No less than five of Mir‘s modules were based on the FGB, and on the ISS one current (Zarya) and one future (Nauka) module have the same base. The jerry-built Polyus payload for Energia’s first launch was also based on an FGB.


Khrushchev, Sergei N. Nikita Khrushchev and the Creation of a Superpower. Penn State University Press. University Park, PA, 2010.

Portree, David S.F. Mir Hardware Heritage. Houston, Texas. Johnson Space Center, 1995.

The TKS ferry for the Almaz Space Station“, Sven Grahn.

TKS“, Anatoly Zak.

OLS: The Orbiting Lunar Station (Integrated Program Plan, Part III)

OLS Schematic

The (surprisingly crude) schematic of the OLS from North American Rockwell’s Orbiting Lunar Station (OLS) Phase A Feasability and Definition Study, Vol. V. Public Domain image via NASA.

What it was: An April 1971 study by North American Rockwell, commissioned by NASA, on putting an eight-astronaut space station in polar orbit around the Moon.

Details: There was a short period of time prior to NASA settling on the Integrated Program Plan when some within that organization advocated a more conservative “space stations everywhere” program instead. A combination of NASA administrator Thomas Paine’s insistence on being bold and Spiro Agnew’s enthusiasm for Mars got the focus shifted to the Red Planet, but the space agency did its due diligence and took a look at the suggested stations in the context of the IPP.

From the standpoint of the 21st century, the most unusual of of these was a space station around the Moon, plainly dubbed the Orbiting Lunar Station, or OLS for short. North American Rockwell got the contract to flesh out the idea and dropped the result on NASA desks in April of 1971, just as Apollo 13 was gripping the world.

NASA’s basic intention was that the orbiting station would have several purposes. Scientific study of the Moon from orbit was one, and so was a supporting role for a surface base—communications with the Far Side, for example, or serving as an emergency shelter, or as a command station for remote rovers (thus alleviating the roughly 2.5 second round-trip delay between the Earth and the Moon). There was also a requirement to use the station for astronomy, including an intriguing suggestion to perform high-resolution X-ray astronomy using the edge of the Moon as an occulting edge, and the idea that the station would serve as an excellent test bed for the systems that would be used in the orbiting command centers that would probably feature during interplanetary missions.

What North American Rockwell presented was a station that would have been launched on a Saturn INT-21 (essentially a Saturn V without its upper stage, similar to what was used to launch Skylab) or in the cargo bay of the then-conceptual Shuttle that NASA was working on. After being checked out in LEO by a crew which would return to Earth, the unmanned OLS would be sent into lunar orbit using a Nuclear Shuttle, and then the first eight-astronaut expedition to the station would be sent using another. The vagaries of the Moon’s orbit around the Earth suggested a mission every 109 days to the station, with North American Rockwell arbitrarily deciding to swap half the crew out each time. After ten years, the OLS would be decommissioned.

As to where the astronauts were going, exactly, North American Rockwell came up with two possibilities. One was a purpose-built station, to which they specifically assigned the name OLS, while the alternative was a refit of a modular station originally built for Earth-orbital activities, which they dubbed the MSS. The end result was functionally the same, however, so for the purpose of simplicity we’ll focus on the OLS.


The four habitable decks of the OLS. Composite image from the same source as previous. Click for a larger view. Public Domain image via NASA.

The station would have been built around a cylindrical core module 60.83 feet long and 27 feet in diameter (18.5 × 8.2 meters). It would have four receptive docking ports around its side, and one “neuter” port on each end, all intended for docking visiting ships or expansion with further modules later. Within were six decks, four of which were pressurized for human habitation. Access between these decks was provided by a series of circular openings on the station’s long axis; the exception was between decks 2 and 3, which were connected by a hatch that could be sealed off in the case of emergency.

One of the end ports would be used to attach a 33.42′- (10.2 meter-) long power module, which would unfurl four solar arrays totaling 10,000 square feet (929 square meters) hooked to regenerative fuel cells for storage, while one of the four receptive ports would house experiments that needed “a clear field of view” (the astronomy experiments, one presumes) and a bay for storing and repairing satellites the station would drop into other lunar orbits. Altogether it would have a dry mass of 107,745 pounds (48.75 tons); compared to other stations it would have been intermediate in size to the larger Skylab and the smaller Salyut-7.

The core module would also have a radiation shelter on the second deck, containing a secondary control room, backup galley, and toilet, protected by the stations 16,000 pounds of water (roughly 7250 liters) stored in a jacket around the shelter. The water was also used by the thermal radiators to deal with what NAR termed “the significantly more severe” environment in lunar orbit.

The OLS’s ten-year lifespan was specifically targeted to the 1980s, giving some idea of how long North American Rockwell though it would take to get it up and running.

What happened to make it fail: Like the rest of the IPP with which it was associated (with the partial exception of the Space Shuttle) the OLS ran into the avalanche that was the early 1970s. As well as major budget cuts and indifference on the part of the government and the American public toward space ventures, it had the additional problem of no high-level advocate. NASA administrator Tom Paine in particular was critical of the “stations everywhere” approach and preferred Wernher von Braun‘s more audacious Mars mission. There it would be only a minor part, if it existed at all.

What was necessary for it to succeed: You’ve got to start somewhere, begin with an administrator or a “rock star” like von Braun backing it to the full. Then all you have to do is prevent the economic troubles of the 1970s, end the Vietnam War, and somehow get one of the President or the general public on side. Piece of cake.

If you relax the requirement for success to include a lunar station not directly descending from NAR’s study, the situation gets a little easier. The American and Russian space agencies have discussed the possibility of a lunar station as a follow-up to the ISS, and it’s to North American Rockwell’s credit that both have described a setup not too dissimilar from the OLS. Though NASA still seems more interested in an asteroid redirect mission or a Mars mission at the moment, there’s a halfway decent chance that, about sixty years after the fact, the OLS’s descendant will take flight.


Orbiting Lunar Station (OLS) Phase A Feasibility and Definition Study, Vol. V; Space Division North American Rockwell; Downey, California; April 1971.

The Space Shuttle Decision; T.A. Heppenheimer; NASA History Office; Washington, DC; 1999.




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.

Sidebar: Sonnengewehr, the “Sun Gun”


Illustration of the Sonnengewehr “Sun Gun” as published by Life magazine on July 23, 1945. Image copyright status unknown, possibly owned by Time, Inc.. Click for a larger view.

At the end of World War II the United States famously snapped up as many German scientists as it could with Operation Paperclip. While they were from a wide variety of disciplines, the ones most remembered today were the rocket designers and, as London and Amsterdam were still sporting spectacular V-2 craters, public interest in them was high at the time.

By the end of 1945 most of them would relocate to the United States, but in the period immediately following the end of fighting in Europe they were still in Western Europe and being interrogated by US intelligence personnel keen to learn about a line of weapons development in which the Nazis had jumped far ahead of the rest of the world.

It was in this setting that a few articles were published in major US newspapers and magazines (Time, Life, the New York Times and others) during July 1945 outlining one bit of information the US was getting from the captured scientists. All the articles were based on a single news conference held in Paris at the end of the previous month. While the conference apparently covered a wide variety of weapons that had been under development when the war ended, the articles picked up on one spectacular one and focused on it: the Sonnengewehr, quickly dubbed the “Sun Gun”.

The Sun Gun idea had been brought to the attention of the US by a group of scientists and engineers at Hillersleben, Germany (now part of the town of Westheide in Saxony-Anhalt, which was once part of East Germany). Though mostly unassociated with Wernher von Braun’s more-famous group they too had experience with rocketry, having worked on rocket-assisted artillery weapons and tank shells during the war.

As reported, in an unfortunately garbled way that makes it clear the reporters didn’t understand the underlying physics, the Sun Gun would have been a disc-shaped space station in a 3100-mile (5000-kilometer) orbit; some sources say 5100 miles, but this seems unlikely as German engineers would have expressed themselves in kilometers and that would be an unwieldy 8208 of them. Either way, neither would have been geosynchronous, an oddity pointed out even by some of the reporters in 1945.

Regardless, the station would have been coated with metallic sodium—chemically reactive and so easy to tarnish in the atmosphere, but which would stay clean in vacuum—polished into a mirror. The mirror would be pointed at a receiver off the coast of Europe and used to boil ocean water for power, but when the need arose it could be used on military targets—it had a projected ability to heat anything on the surface to 200 Celsius. Other numbers are scant and not clearly from the scientists themselves, but one that raises an eyebrow is that the mirror would have had an area of 5000 square miles (a round number in non-metric units, which is suspicious, and matches a diameter of 128.4 kilometers). Other sources suggest a much more realistic 9 square kilometers.

Life magazine was the most expansive on the topic, and published several drawings on the construction and operation of the station. Unfortunately their accompanying text and some of the details in the illustrations themselves suggest that the article’s authors were engaging in speculation on both topics. For example, they have the station being built of pre-made sections—cubes, oddly enough, which makes it a bit hard to produce a disk—when there’s reason to believe that it would have been made on a skeleton of long cables reeled out from a central station. Also contrary to this, Life has the inhabitable area around the edge of the disk, though this would have turned the Sonnengewehr into a “filled-in” version of the torus-shaped stations so favoured by von Braun during his lifetime

Immediate post-war reports to the contrary, it’s very unlikely that there was any sort of official work done on the Sonnengewehr beyond some tentative memos and discussions. If nothing else, consider the sheer mass of material that would have to be lifted into high orbit to build it. One source suggests one million tonnes of sodium metal, a figure considerably larger than the mass of everything ever lifted into orbit by all the world’s nations between 1957 and the present day.

Instead it seems to have been at best something batted around as a possible ultimate destination—even the scientists involved were thinking along the lines of the year 2000—in the culture of grandiosity that Nazism embraced and that also produced things like the Landkreuzer P. 1500 and Hitler’s architectural enabler Albert Speer. Even the mainstream rocketry program at Peenemünde was looking to run before it learned to walk, and this was just an extreme example of this attitude in the embryonic German space program. It may not have even been as tentative as that: at worst, it was merely discussions of an idea floated by the father of German rocketry, Hermann Oberth, in 1929.

Any gloss of reality the Sonnengewehr got likely came once the war was over and the Hillersleben group were under the control of the American military. In that precarious situation they would have been searching for anything to impress their captors of their usefulness and the Sun Gun inflated from cafeteria-table discussions to the preliminaries of a project. It did get them a little attention at the time, to be sure, but its sheer fantasticalness made it quickly drop back out of the limelight.

“Big G”: Getting to Orbit Post-Apollo


A schematic of one Big G configuration. The original Gemini capsule can be seen on the left, while everything from the passenger compartment on to the right was new. The adapter on the far right was designed to allow yet another cargo module, space lab, or habitation/life3 support module depending on the mission. Public domain image from a short briefing document given to NASA in December 1967. Click for a larger view.

What it was: A 1967 proposal by McDonnell Douglas to build a new Gemini spacecraft with an extra module attached to its aft end. This would be the craft for flying astronauts to and supplying the proposed space stations—both civilian and military—that were to follow the Apollo landings. It would have been able to deliver twelve people (ten on top of the pilot and co-pilot of the original Gemini) and 2500 kilograms of cargo to low Earth orbit; with an optional extension module it could have taken 27,300 kilograms.

Details: NASA was well into post-Apollo planning by 1967 and at that early stage it was far from settled that they were going to go for a spaceplane as their next major spacecraft. Even if they did go for one, some (including Wernher von Braun) felt that an interim system was needed until what was slowly turning into the Space Shuttle was ready. Basic research on lifting bodies was still underway and while landing on land was already considered desirable, at the time NASA’s chief spacecraft designer Max Faget favoured doing so with a ballistic capsule using a device that the agency had been working on for years: a Rogallo parawing to brake its descent.


A clear view of the third, cylindrical module which would have been used for some Big G missions. Public domain image dating to 1969 via the NASA publication SP-4011 Skylab: A Chronology.

While there had been discussions about using the parawing with an Apollo capsule, the Gemini had the advantage in that it was the one where that program had begun; it had progressed as far as manned drop tests—Jack Swigert of “Houston, we’ve had a problem here” fame started his career as an astronaut flying a Gemini mockup under a parawing. McDonnell Douglas then sweetened the pot by reconfiguring their Gemini B so that it had the same base diameter as an Apollo capsule (making it simple to attach to a Saturn rocket) while giving twice the cargo capacity of its competitor. A modification of the Apollo CSM had studied in the years prior to Big G, and the so-called MODAP could match this increase, and even go beyond it with external cargo capsules—but then this is where the Big G’s cylindrical extension module came in and blew the Apollo derivative out of the water.

The Gemini B had begun as a logistics craft for the USAF’s Manned Orbiting Laboratory that, for the purposes of this discussion, had one important difference from the regular Gemini. It needed to be able to dock to the MOL and the most reasonable way to do so was at its aft end. This necessitated cutting a hatch into the capsule’s heat shield. While this looked like a dangerous strategy on the surface, it was proven to work and it became possible to attach other things to the Gemini B’s underside. For the basic Big G this was a truncated cone that increased the base diameter of the new craft to match that of the Apollo spacecraft, making it easier to mate it with Apollo hardware—and not just rockets. While they preferred their own cylindrical module for the third module that made a regular Big G into the nearly thirty-ton large cargo craft, McDonnell Douglas also came up with a side proposal to use Apollo Service Modules in that slot if NASA so desired.

The Big G was designed to be launched by one of three rockets. In its smallest configuration, it would be lofted by a Titan IIIM, a man-rated version of the Titan III which the USAF had started working on as a rocket for the Dyna-Soar program and then moved over to the MOL when Dyna-Soar was cancelled. This was the least powerful of the three alternatives, and would have been able to launch only the basic Big G. For one with the full complement of extra modules the choices were one of two Saturn variants that NASA was interested in building, either the Saturn INT-11 (the first stage of a Saturn V with four of the strap-on boosters used for the Titan IIIM) or the Saturn INT-20 (which would have consisted of a Saturn V’s third stage directly mated to the same rocket’s first stage).

As Big G was proposed not long after the Apollo 1 fire, it was designed to use an oxygen and helium mixture for its atmosphere, a difference from the pure oxygen of the original Geminis. The interior of the craft was also heavily reworked, with all of its systems upgraded and improved from the original’s. After all, as successful as it had been the previously flown Gemini had been only the second model of spacecraft flown by the United States.

When launched the Big G could have flown directly to a space station of short resupply or astronaut delivery-or-return missions. Alternatively the third module could be adapted to be a mini space lab, or a life support and habitation module capable of stretching the flight to 45 days; when the Big G was first being discussed, the then-record longest spaceflight of 13 days, 8 hours, 35 minutes had been achieved in an original model Gemini.


Coming in for a dry-land landing under its triangular parachute, the Rogallo wing. Public domain image from McDonnell Douglas briefing to NASA, December 1967.

As previously mentioned, the end of the mission would see the re-entry capsule of the Big G bring its  astronauts home to somewhere in the United States by landing with a Rogallo wing. The capsule itself would have three landing skids that would cushion the impact of swooping into the ground, and then bring the vehicle to a stop.

Using the Big G as its transportation backbone, NASA’s hope was to have a 12-man space station in orbit by the time the Space Shuttle was ready to fly in 1975 (to use what turned out to be the optimistic estimate of 1969).

What happened to make it fail: The late 60s were an era of falling budgets for NASA, and there was a great deal of concern that the cost of launches was going to sink the manned space program—the Saturn V was notoriously expensive on a per kilogram-to-LEO basis (one figure, adjusted for inflation to modern dollars is $US22,000 per kilogram). Prices were anticipated to come down, but in general even the cheapest expendable launch vehicles have only beaten this figure by about a factor of three.

A re-usable launch vehicle had the promising appeal of bringing these costs down a great deal (projections, unfortunately based on unrealistic launch schedules, ranged as low as $US1,400 per kilogram). For crew return this made a glider of some sort necessary—either a lifting body or a winged craft—and when a high cross-range capability in NASA’s next spacecraft was cemented as desirable about 1970, wings became an absolute necessity. All possibility of a capsule, Big G included, fell by the wayside.

What was necessary for it to succeed: In retrospect the Space Shuttle looks like a mistake—its most basic reason for existence was to be a cheaper way to orbit than missions launched on expendable launchers and it never did so—most calculations pin it as more expensive per kilogram to orbit than the already expensive Saturn rockets it replaced. It’s important not to apply too much hindsight to this decision, but even in 1969 there were signs that sticking with capsules for manned spaceflight was the way to go. NASA had a strong constituency for this approach including, at first, the chief designer for the manned spaceflight program Max Faget. If he had stayed on-board with capsules, there’s a good chance that things would have turned out that way.

If they’d decided to go with a capsule, the two main options were continuing using Apollo spacecraft or building the Big G. Apollo had the advantage of still being in production, and it could have been launched on very similar rockets to the ones suggested for Big G. Big G, as mentioned, had the advantage of considerably more cargo space. Which of the two would have been picked comes down to an impossible-to-settle question of which advantage would be seen as tipping the scale.

The other possibility is that the Shuttle could have gone ahead, but that NASA could have realized just how long it was going to take before it flew: instead of going to space in 1975 its first mission was pushed back to April 12, 1981. If in 1967-69 they had had a better handle on the challenge they faced, the idea of using Big G as an interim logistics craft until the Space Shuttle was ready to fly would have been more attractive. The only problem with this scenario is that the Shuttle’s development costs put a big dent in NASA’s budget through the 1970s, so the space station that the Big G would have supported would have been hard to build while also going ahead with the orbiters.

Mir-2: The Once-and-Future Station


A schematic of the final Mir-2 design circa 1993. DOS-8 is the large module just above the central junction. Image source unknown, believed to be NPO Energiya. Click for a larger view.

What it was: The next in in the long line of increasingly large and sophisticated Soviet space stations that stretched from Salyut 1 in 1971 to Mir in 1986.

Details: Mir is the least-heralded of the major space firsts. Sputnik-1 and Yuri Gagarin rightly retain their fame, and of course the United States can answer with Apollo 11. Yet of the “big five” goals of the early manned space programs (the fifth being the still-yet unclaimed manned Mars landing) Mir fulfilled one: the first “real” space station. There had been other stations before, as far back as Salyut 1 and Skylab in the early 1970s, but they were not what was envisioned when an orbital outpost had first been seriously discussed in the late 1950s. Unlike the earlier single-piece stations Mir was the first “building” in space, in the literal sense of the word, constructed out of multiple components sent up over time and joined to make a functional whole. Salyut 7 had had one experimental module (TKS-4) attached after launch, but Mir was the real thing.

The station was built around the so-called Base Module (DOS-7), the ultimate version of the DOS framework derived from Vasili Mishin’s civilian Salyuts and Vladimir Chelomei’s Almazes. While it was being built the Soviets also built a backup base module, DOS-8, in case something went wrong with the first one. From the beginning, though, they were also making plans for what to do with the backup if DOS-7 and its launch went as planned. When they did, DOS-8 definitely became the centrepiece of a second space station.

At first Mir-2 was to have been “just another Mir”, which is not too surprising considering that they shared the same design for the core module. The only major difference between the two was the addition of a truss extending from the end of the station, greatly increasing its length, for solar panels and other equipment. But in 1982 Leonid Brezhnev died and was replaced by Yuri Andropov; in the United States, Ronald Reagan had become president the year previous and four months after Andropov’s takeover the US leader initiated the Strategic Defense Initiative. Andropov chose to fight fire with fire, and the Soviet space program was re-oriented to deal with the newly perceived threat. Mir-2 began to change.

There were actually several major redesigns of the station before 1993. One was still fairly close to the original Mir, in that most of its modules were designed to be lifted by Proton rockets and so had to stay in the 20-tonne range. But the station’s solar panels and a larger core module were designed with Energia in mind, and could range up to ninety tonnes. In fact the Energia’s first test payload the space weapon testbed Polyus, which was hurriedly cobbled together from several pieces of equipment, was in part based on a test article of the proposed Mir-2 core. The truss was also turned into a long docking tunnel meaning that one more manned ship or supply craft could visit this version of Mir-2 as compared to the original.

While that design went a fair distance, by the end of the 80s Mir-2 had grown again into what was formally called the Orbital Assembly and Operations Center but generally referred to as “Mir 2.0”. The first two designs had belonged to the Fili Branch of TsKBM, which is to say largely the Almaz design bureau that had been taken from Vladimir Chelomei after the death of his Politburo supporter Andrei Grechko. This version of the station was entirely NPO Energia’s baby and so under the close watch of Valentin Glushko.


The largest version of Mir-2, with its dual keels. Public domain image via NASA.

The new design was similar in appearance to the largest of all the American designs for their space station Freedom, the dual-keel arrangement proposed by McDonnell-Douglas in 1986; Mir 2.0 was to have been constructed around a rectangle made of four trusses. After the launch of DOS-8, Energia rockets would do the rest of the work: a 90-ton core module, then the truss and solar panels, then three more launches carrying three more 90-ton modules. The modules and the solar panels would be attached to a cross-beam on the truss, while various pieces of equipment would be balanced around the rectangle to balance tidal forces as the station orbited Earth.

By the time Mir 2.0 was getting really underway though, the ground had shifted again. Andropov and his successor Konstantin Chernenko were gone, replaced by Mikhail Gorbachev. The US and the Soviet Union had begun reducing their nuclear arsenals with the INF Treaty, Eastern Europe had cut ties with the Soviet Union, and the USSR itself was in an economic collapse. Now Mir-2’s design started heading in the other direction.

“Mir 1.5” was once again based on the DOS-8 block. Dedicated Energia launches were no longer in the picture, so smaller modules in the seven tonne range were assumed now. The real twist was that now DOS-8 was to be launched sometime around 1994 along with the second flight of the Soviet shuttle Buran—its first manned mission. Using the orbiter’s robotic arm, DOS-8 would be maneuvered to join up with the original Mir station; a power module and a biotechnology module would be launched and automatically docked later. When those were all in place, some two years later, DOS-7 would be detached and allowed to deorbit. The newly hatched station would then be built up with additional modules (including a second biotech lab) and a long cross-truss on which to attach solar panels and some equipment, the latter brought by another flight of Buran. This version of Mir-2 would see the second Soviet shuttle (supposedly to be named Burya) arrive every six months to swap out the biotechnology modules, returning their manufactured goods to Earth.

Then the USSR came apart completely. Toward the end of 1993 Mir 1.5 was no longer going to begin its life attached to the original Mir. It was down to just four modules at this point, and would hold a crew of two. By this point, except for the cross-truss, it was largely the same model as Mir, made better primarily by the experience of building the first station.

What happened to make it fail: By then the Soviet Union itself had come apart, and the Russian economy was approaching its nadir, contracting something like 40% in the first half of the 90s. Meanwhile, the American space station Alpha was in very severe trouble. In March of 1993 the new President Bill Clinton had told NASA to look at bringing Russia into the space station effort (which, while primarily American, was also being supported by the ESA, Japan, and Canada). On November 1 of the same year NASA and the Russian Space Agency agreed to merge Mir-2 and Alpha into the International Space Station.

What was necessary for it to succeed: In a sense it did. The third piece of the ISS was the Russian module Zvezda, which is in fact the well-travelled DOS-8 block. Altogether there are five Russian pieces to the ISS as of this writing and, while most of them are newly designed for this station, one more beyond DOS-8 has its roots in the older project: the Rassvet module is built on the repurposed hull of the SPP module which was to have powered the final redesign of Mir 1.5 prior to its folding into the international effort.

For that matter, the ISS is due to be decommissioned sometime after 2020. In 2008, Roscosmos informed the US that they intend to detach some of their modules—both already in space and planned to be attached to the ISS between now and then—starting in the late 2010s and use them as the core of a new station, OPSEK (“Orbital Piloted Assembly and Experiment Complex”, in Russian). One of the modules to be detached is DOS-8, and the designs of OPSEK seen to date bear a family resemblance to Mir’s once-proposed descendant.

Sidebar: The Mercury Space Station


One of two configurations of a proposed Mercury-based space station. The other had the capsule stay in place with an inflatable tunnel running between the two hatches. Click for a larger view.

(Another little experiment along the lines of the Chief Designer posts. I’m finding a few space projects here and there that couldn’t support an entire discussion in False Steps’ usual format, but that still are worth examining. I’m thinking that perhaps they can be used as short sidebars here and there in the final product. I’ve tried two of them out on Reddit so far and they seem popular enough, so here they are for you too.)

In August 1960 McDonnell Aircraft suggested to NASA that a Mercury capsule should be extended into a small space station. This was despite the fact that a human being could just barely fit into a Mercury capsule, and couldn’t live in one for long—the final Mercury, Mercury-Atlas 9, could only last a full day because it was stripped down to hold more consumables, and even at that Gordon Cooper was only able to get it back to Earth through heroic efforts on his part.

That didn’t deter McDonnell. They suggested building a secondary, cylindrical capsule with the main Mercury capsule mounted to one end, and then sticking the whole thing on top of an Atlas LV-3B to fire it into space. Since it would be too heavy for that rocket to lift, the new capsule would have an Agena motor attached to its other end, which would finish pushing the spaceship into orbit.

They stated that the one man aboard the capsule could, with the aid of the extra living and storage space, live on board for an entire two weeks, performing experiments and whatnot until it was time to return home. As a result, they pitched it as a “space station”, but it really was no such thing. Altogether the whole thing only massed a few hundred kilograms more than the Vostok capsule that carried Yuri Gagarin into space; its internal living space was actually smaller than a modern-day Soyuz capsule. Nobody calls either of those craft space stations.

The Mercury Station never got built and likely the kicker was that the Mercury was pretty much an experimental craft. It was never intended to be upgraded and so McDonnell had to resort to a remarkable kludge just to let the astronaut onboard climb between the two pressurized volumes. Ideally there would have been a tunnel directly between the two when they were docked normally, but the Mercury’s retrorockets were in the way. So as designed, this craft would have had to take one of two approaches. Either the Mercury would stay in place and an inflatable half-toroid would join the hatch on the side of the capsule with the hatch on the secondary module, or else the Mercury would bend backwards on a hinge until its side hatch actually touched the side of the new capsule. Only then would the astronaut be able to clamber from one to the other.

NASA said no thanks and nothing ever came of it, but the basic idea seems to have evolved into the Manned Orbiting Laboratory for the US Air Force. Gemini was called “Mercury Mark II” after all, and was configured so that a tunnel could run between its base and any add-on modules behind it. It was quite natural, then to take the concept and adapt it to the newer, more capable spacecraft.