STCAEM-CAB: A Mouthful of a Mars Mission (Space Exploration Initiative, Part II)

STCAEM-CAB schematic diagram

A schematic of the STCAEM-CAB Mars space vehicle. The twin heat shields (the scoop-shaped structures) were needed as the craft was too massive to aerobrake in one piece even after the TMIS was jettisoned. The MEV and MTV would separate before the Mars encounter, aerobrake and enter orbit separately, then rendezvous and dock while high above the Red Planet. Public domain image by the author, based on one published in Space Transfer Concepts and Analysis for Exploration Missions, Implementation Plan and Element Description Document (draft final) Volume 2: Cryo/Aerobrake Vehicle. Click for a larger view.

What it was: One of the products of 1991 study by Boeing for a Mars mission vehicle. Technologically it was the most conservative of the possible craft they suggested, relying entirely on cryogenic propulsion, but the trade-off was a hair-raising mission profile including a hard aerobraking maneuver at Mars.

Details: In 1989 the then-President of the United States, George H. W. Bush, put forward a proposal to (among other things) send astronauts to Mars. While NASA had always kept Mars contingency plans up to date since even before Apollo 11, this was one of the few times where it looked for a while like they might actually be able to put their plans into motion. In 1989 they produced a strategic plan known informally as the “90 Day Study” and then set various contractors to work on its different goals.

One of these was “deliver cargo reliably to the surfaces of Moon and Mars, and to get people to these places and back safely”. Boeing was the contractor primarily concerned with this this one, and performed an initial study in 1989 before amplifying it in 1991-92. For Phase 1 of the later study they worked their way through the pros and cons of several different approaches to crewed Mars missions for NASA to choose between, most of which involved novel propulsion systems like nuclear rockets and solar-electric ion engines.

One was more conventional though, closely hewing to NASA’s own baseline for the mission, and was presented first in their Phase 1 final study. All the Mars craft were assigned the clumsy name of the study, Space Transfer Concepts and Analyses for Exploration Missions (STCAEM), and differentiated by their propulsion method. The first craft was accordingly the STCAEM-CAB, the final thee letters standing for “cryogenic/aerobraking”.

The Mars mission was placed firmly in the context of the whole Space Exploration Initiative, not least because the vehicle in question was going to ring in at a whopping 801 tons. No conceivable rocket was going to lift it in one piece, and so the SEI’s space station Freedom was to serve as a base for the in-orbit assembly of the massive ship. A Moon base was also assumed, and served two purposes insofar as Mars was considered: as a test bed for the various technologies, and also a place to put a deliberately isolated habitation module that would simulate a long Mars mission without leaving the immediate vicinity of the Earth-Moon system.

Shuttle-Z in

Another Shuttle-derived launcher (not the Shuttle-Z) charmingly called the “Ninja Turtle” configuration–lifting the STCAEM-CAB’s two aeroshells off Earth and to Freedom. Public domain image from NASA, same source as previous. Click for a larger view.

Using what was called the Shuttle-Z (a variant on the Space Shuttle wherein the orbiter was replaced almost entirely with 87.5 tons of payload, leaving only the main engines, the boosters, and the iconic orange tank), eight trips would be made to Freedom with various components of the ship. After assembly, the STCAEM-CAB would consist of several sections, the largest of which was the Trans-Mars Injection Stage (TMIS) at 545.5 tons. Fuelled with liquid hydrogen and liquid oxygen, the cryogenics referred to in its name, the four-engined TMIS would push the entire craft into a Mars-bound trajectory before being jettisoned. Boeing studied a number of missions that could be flown and came to the conclusion that the relatively less efficient cryogenics propellants would work best when Mars was at opposition, leading to a 580-day mission.

Missions for Mars have often included odd wrinkles in their plans to help cut down the amount of propellant needed to pull them off; for example, the Integrated Program Plan’s mission avoided a circularization burn at Mars, leaving it in an elliptical orbit that made the lander’s descent to the surface start at a higher speed—but better to have to slow down the relatively small MEM than the entire interplanetary craft. In the case of the STCAEM-CAB the trick was unusual enough to warrant mention. For the bulk of the outbound trip, the two other main components of the craft, the Mars Excursion Vehicle (MEV) and the Mars Transfer Vehicle (MTV), would stay docked, with a small transfer tunnel between the two of them. In this configuration it would serve as the habitation for the crew of four astronauts, with the MTV’s crew module being 7.6 meters by 9 meters. This would give each astronaut something on the order 50 cubic meters to live in, with another 50 for everyone to share in the MEV, at least on the way out. With fifty days to go before Mars, however, the two would separate (the crew staying in the MTV, which had the capability of returning them to Earth) so that they could each dive into the Martian atmosphere at closest approach and slow down behind their individual heat shields.The MEV would brake first, 24 hours before the MTV and crew, giving Mission Control a chance to observe Mars close up and decide if it was safe for the second aerobraking maneuver.

Side and front views of the Mars Excursion Vehicle

Side and front views of the MEV after jettisoning its aerobrake and landing on Mars. Public Domain image from NASA, same source as previous. Click here for a larger view.

This approach also had the advantage of making the aerobraking shells smaller, as even done this way they approached the length of a Shuttle Orbiter (30 meters, as opposed to 37.2 meters) and so the shell for a singular craft would have been impossible for a Shuttle-derived stack.

After both had aerobraked and entered orbit, they would dock again, the crew would transfer to the MEV, and then descend to the surface. Several landers were mooted, from one with a 0.5 lift-to-drag ratio (the favored option, pictured at left), one with a 1.1 ratio, and a biconic lander that was going to require a launcher back on Earth that had a diameter of 12 meters(!).

The astronauts would stay on Mars for 30 days, then a subset of the MEV (the third and uppermost of the circles in the MEV image shown, as well as the tankage underneath it) would launch skywards again to dock with the MTV. This would in turn get them back out of Mars orbit and home to Earth, where they would aerobrake again to bleed off some velocity and enter Earth orbit. The crew would finally enter an 3.9 meter wide by 2.7 meter tall Apollo-like capsule for re-entry to somewhere in the ocean. Optionally the MTV would remain in orbit and be refurbished for another journey.

Mars Transfer Vehicle and aeroshell

A closer view of the MTV, which alone would make the journey back from Mars with the crew aboard. The aeroshell would make the trip too, as the craft would aerobrake into Earth orbit too. Public domain image from NASA, same source as previous. Click for a larger view

Boeing scheduled out the launch of the first Mars mission three different ways. One was a “Minimum Program”, intended to do no more than meet the 90 Day Study’s stated goals, one was a “Full Science Program”, while the last was an eyebrow-raising “Industrialization and Settlement Program”. The latter was on Mars by 2009, and saw a permanent Mars base with 24 inhabitants in 2024, some astronauts staying there for years. The science-oriented program made it by late 2010, and saw a permanent lunar base of four (the settlement plan saw 30!) but only a periodically inhabited Mars base of six astronauts. The minimum options saw a first Mars landing, by coincidence, in 2016. It had neither permanent Mars or Moon base. As for the cost of each, Boeing includes various graphs but only gives one number, for the Industrial and Settlement Program: an eye-watering $100 billion from 2001 to 2036, with a peak of $19 billion in 2020.

What happened to make it fail: Well, “$100 billion…with a peak of $19 billion” for a start. While the Bush Administration was obviously looking for their own version of a “Kennedy Moment” when they announced the Space Exploration Initiative, they were not all that keen on actually paying for it. Couple that with extreme hostility from Congress anyway, and the SEI’s ultimate goal of Mars mission was in trouble right from the start. Likewise NASA blew it by proposing grandiose plans like an 800-ton Mars ship, the full space station Freedom, and a permanent lunar base, to the point that the backlash led to the “faster, better, cheaper” era under Dan Goldin (which had its own problems, but that’s another story). Boeing even spent some pages in Phase 1 trying to determine returns on investment and the like, with some of their anxiety at the cost coming through in their prose. This includes an unflattering comparison to the development of the Alaskan oil pipeline and the investment in supertankers during the closure of the Suez Canal from 1967-75.

As far as the STCAEM-CAB in particular was concerned, it also suffered from being “good under most circumstances but never the best”. Boeing preferred the Nuclear Thermal Rocket variation, and focused on that going forward from Phase 1 of the study, even though Goldin had been NASA administrator for a year and a half by the time their final work on the project was completed. The NTR variant was certainly not going to go ahead thanks to NASA’s new focus, and the CAB had already fallen by the wayside.

Ultimately, though, this mission suffers from the same problem as the Integrated Program Plan’s Mars Mission from the early 70s. It existed down near a long line of large programs, few of which actually happened. You need to join back up several links in a chain to get to the launch of this spacecraft. Ultimately, quite a few things would need to change for STCAEM-CAB to make its trip, making it quite unlikely under any circumstances.

Sources

Space Transfer Concepts and Analysis for Exploration Missions, Implementation Plan and Element Description Document (draft final) Volume 2: Cryo/Aerobrake Vehicle, Gordon.R. Woodcock. Boeing Aerospace and Electronics. Huntsville, Alabama. 1992.

The Mars Excursion Module: One More Small Step (Integrated Program Plan, Part IV)

Mars Excursion Module 1967

The Mars Excursion Module, as shown in 1967’s “Definition of Experimental Tests for a Manned Mars Excursion Module, Volume IV”. By 1969 it would evolve to have a truncated rather than rounded nose, and the base section was larger to notionally support storing a rover. This view affords an excellent look at the central ascent vehicle and its tanks, which would leave the rest behind. Public Domain image via NASA. Click for a larger view.

What it was: The last piece of the Integrated Program Plan’s mission to land astronauts on Mars in the 1980s. First proposed in 1966 (though with a similar, smaller craft being advocated by Philip Bono in 1964), in 1969 it was presented by Wernher von Braun to the Space Task Group and adopted as part of NASA’s proposal for the post-Apollo focus of that agency. Though not developed by him, it represented the culmination of his lifelong dream to visit Mars vicariously through the people he would be instrumental in sending.

Details: In a world where NASA’s Integrated Program Plan of 1969 went forward, you might be an astronaut on the first mission to Mars. After getting to orbit on board the Space Shuttle (likely the “DC-10” of Max Faget‘s design, or similar), you’d board a Nuclear Shuttle-driven

mem-schematic

MEM schematic view, 1969, showing the standing pilots and the tunnel to the lab and living area in the lower section. Public domain image from NASA. Click for a larger view.

interplanetary ship gingerly fuelled by personnel in Space Tugs. The journey would be a long one: hundreds of days, and possibly including a flyby of Venus, the exact duration depending on the year when the mission got underway. Eventually you’d get to your destination, though, and assuming all was well your ship would settled into an elongated orbit around the Red Planet. Half of the crew would stay aboard, while the remaining six astronauts (hopefully including you) would get to go down to the surface. To accomplish that, you’d use the Mars Excursion Module (MEM).

NASA studied a variety of craft that might make this final leg of the journey, but the MEM as pictured in 1969 first made an appearance in a study done at the Marshall Space Flight Center in June of 1966. A year previous, Mariner IV had shown that NASA’s previous best estimate of Mars’ atmospheric density, which had been about 25 millibars, or about 2.5% of Earth’s atmosphere, was much lower than expected at just 6 millibars. Previous designs were useless, relying as they did on lifting bodies and parachutes that would get some “bite” from the air on the way down. Marshall’s suggested shape, resembling an oversized Apollo capsule, was the first to deal with the reality of the situation: after entering the Martian atmosphere, even the MEM’s capsule-shaped body would only slow to a terminal velocity of 900 m/s and then carry on at that rate until hitting the ground. As this is just a little over 2000 miles per hour, it would bring the “terminal” to the fore if nothing else were done.

By November 1967 the details had been worked out after the problem was handed off to North American Rockwell. Their MEM was now recognizably the craft pitched by von Braun in 1969, though different in carrying four astronauts. During the descent the crew would be in the command module which took up the point of the MEM’s conical shape, while the lower deck’s laboratory, living quarters, and external airlock would be reached through an internal airlock and tunnel. The capsule was 30 feet in diameter at its base (9.1 meters) and 29 feet tall (8.8 meters). At re-entry time it would weigh 46.1 tonnes. Altogether this made it approximately the same size as the full Apollo CSM if the latter craft’s service module had continued the slope of the capsule on top of it instead of following parallel lines down to the engine. The contents of the extra volume enclosed made for a 14-tonne difference in mass, though, and later iterations of the MEM upped its base to 32 feet, the same diameter as a Saturn V, with a corresponding increase in weight.

The MEM in the context of the larger Mars Expedition craft.

The MEM in the context of the larger Mars Expedition craft. Public Domain image from 1968’s “Integrated Manned Interplanetary Spacecraft Definition, Volume IV”, via NASA.

After departing the Mars Expedition ship, the MEM would use a solid retrorocket to leave orbit and a liquid fuelled one to land, parachutes being all but useless in the thin air. On the plus side NAR’s engineers noted that Mars’ pitiful atmosphere meant that heat shields could be a lot lighter than those needed for re-entry on Earth. The one on the underside would a titanium honeycomb covered with ablating AVCOAT, also used by the Apollo capsule as well as with the Orion MPCV. The ones on the upper slopes of the MEM, made of titanium or L605 cobalt alloy depending on the heat it would endure, could be jettisoned to lose weight partway through the trip down to the ground. Daringly, two of the crew would remain standing to pilot the craft (probably supported by a harness when under heavy deceleration loads), and get the MEM landed on its six-legged landing gear. If they had to, they could hover the MEM above the surface for as much as two minutes.

Once down, the crew of the MEM would begin a 30-day stay on Mars. On the surface the MEM would be powered by two fuel cells in the mission module. An S band microwave link would be used for a TV signal back to Earth, as well as telemetry and voice communications, while a VHF link would be used for communications back to the orbiter as well as linking astronauts on the surface to the capsule.

Various configurations of the MEM as it goes through its mission

The many faces of the NAR MEM, from Mars deorbit, lower left, to ascent and rendezvous with orbiter, lower right. Public domain image via NASA, same source as previous. Click for a larger view.

When the mission was over, the toroidal mission module and the landing gear of the MEM would be discarded. Getting back off Mars was arguably the most difficult part of the mission, as North American Rockwell found that even LOX and LH2 was not powerful enough to do the job. Instead they settled on FLOX (70% liquid oxygen and 30% liquid fluorine) as the oxidizer and methane as the fuel, with careful staging of the ascent module’s tanks to minimize mass during the flight, in order to make it back to orbit. Rather than have to deal with two different sets of propellants, the landing engine would have burned the same. This is a somewhat alarming choice, both because the words “liquid fluorine” are always alarming and because FLOX and methane have never been used together in an operational rocket engine (Atlas engines had tested with FLOX and kerosene at least, in the years prior to 1967). The MEM’s reaction thrusters used an odd combination too, chlorine pentafluoride as an oxidixer and hydrazine.

North American Rockwell declared that they could build the MEM given seven years from 1971 to 1978, including heat shield tests from orbit, two manned test flights, and a 242-day “soak” in LEO vacuum to simulate the transit to Mars, with an actual Mars mission sometime from 1981 onward. Hardware development costs would be in the range of US$3.1 to US$5.0 billion.

What happened to make it fail: We’ve discussed the Mars Expedition as a whole previously, and the answer is still the same. Richard Nixon was uninterested in manned space programs and was only willing to support the Space Shuttle for fear of being remembered as the man who ended the Space Age. It’s easy to paint Nixon as the villain here, but he was a reflection of the reality that was the incoming 1970s: the economy was sputtering, Vietnam was costing a fortune, a majority of the American public didn’t care, and Congress was deeply hostile to a Mars mission. A crewed trip to Mars was pushed off nebulously to the year 2000, safely a minimum of five presidential administrations away. Even slight familiarity with American politics unmasks this as the political equivalent of your mother saying “We’ll see” when you asked her for a dog.

What was necessary for it to succeed: The IPP’s Mars landing was the end point of a large number of complex programs. In rough order these were: a Space Shuttle based on a winged orbiter, a LEO Space Station, small Space Tugs, orbiting propellant depots, Reusable Nuclear Shuttles, a Moon base, and possibly an Orbiting Lunar Station. By 1972 NASA’s future was busted down to the Shuttle, and as of 2016 they’re all the way up to step two.

The world where the Integrated Program Plan was followed is a very different one from ours, so it’s difficult to say what could possibly have brought the MEM to fruition. The best-known attempt is SF author Stephen Baxter’s misanthropic novel Voyage, but his suggested alternate outcome of the Kennedy Assassination isn’t sufficiently different to overcome the economic and social tides that sunk the IPP. Early collapse of the USSR in the late 1960s? Election of Gerard O’Neill as dark-horse, third-party President of the United States in 1976? Wernher von Braun finds a magic monkey paw? Your guess is as good as mine.

Technically, the MEM was sound. It was just about everything else outside its conical shell that went awry.

Other Fun Stuff

A picture of a MEM on the surface of Mars by artist Tom Peters

A neat shot of the heat shield jettison on a variant MEM using a ballute to maintain attitude, also by Tom Peters.

Sources

“An Initial Concept of a Manned Mars Excursion Vehicle for a Tenuous Mars Atmosphere”, Gordon R. Woodcock. NASA, Marshall Spaceflight Center. 1966.

“Definition of Experimental Tests for a Manned Mars Excursion Module. Final Report, Volume IV—Briefing”, Geoffrey S. Canetti. North American Rockwell. 1967.

“Integrated Manned Interplanetary Spacecraft Definition, Volume IV, System Definition”, Anonymous. Boeing. 1968.

TMK-1/MAVR: Red Planet

MAVR sketch schematic

Soviet-era schematic of MAVR, provenance and copyright status unknown. Please contact the author if you know of its source. 2 is the greenhouse, 3 is the drop probe for Mars, 9 the probe for Venus, 10 the telescope, and 11 the living quarters.

What it was: Two separate, competing Mars flyby/lander missions (with the same name) from OKB-1, synthesized into a Mars/Venus flyby mission that was the original purpose of the N1.

Details: Wernher von Braun was famously focused on Mars for much of his life, so it’s no surprise that there were two serious proposals to send American astronauts to our next neighbour out during his heyday at NASA. Less well-known is that Sergei Korolev was likewise enamoured of a Mars mission. When the N1 rocket was first floated in 1956, it was quite specifically intended as a launcher for Korolev’s early partner Mikhail Tikhonravov’s proposal of the MPK (марсианского пилотируемого комплекса, “Mars Piloted Complex”). The MPK spacecraft was wildly ambitious—a 1630 tonne ship requiring 20 to 25 N1 launches!—and never even got to the point of sketch plans.

The basic reason for the MPK’s enormous mass was that it was both a landing mission and relied on chemical propulsion. That implied two possible routes out of the dilemma, and in the wake of Korolev and OKB-1’s success with Sputnik, work got underway on studying both under the umbrella name of TMK (Тяжелый Межпланетный Корабль, “Heavy Interplanetary Spacecraft”). One group headed by Konstantin Feoktistov—later famous as a member of the first multi-person crew aboard Voskhod-1—studied an ion-propulsion driven landing mission, while Gleb Maksimov spearheaded a conventionally propelled flyby craft.

Feoktitsov’s TMK settled on a nuclear reactor to power a “slow but steady wins the race” approach that would spiral up, unmanned, through the Van Allen radiation belts. A conventionally launched mission would sprint through the belts and catch up, depositing cosmonauts aboard this spindly-looking ion drive-driven craft for the long journey to Mars. This arrangement initiated one “look” for Soviet and Russian long-term manned missions since then: the dangerous reactor, its engine, and the necessary cooling vanes were all arrayed along a long boom that kept them away from the fragile men aboard.

Maximov’s TMK was far more conservative from a modern perspective, and actually somewhat resembles both the MVF and Skylab. This was the option selected for moving forward. By the end of 1961 the basic parameters of the craft were settled and the mission tentatively aimed at leaving Earth on June 8, 1971 and returning on July 10, 1974—by far the longest manned mission seriously considered of which the author is aware, topping even the Triple Flyby variant of NASA’s MVF.

During coast and flyby it would have been 12 meters in length and weighed 35 tonnes—prior to Mars injection this would have been 75 tonnes including propellant, hence accounting for the lifting capability of a single N1. There would have been 50 cubic meters of space inside, split evenly between habitation and work space. A visual-light telescope for astronomical observations was attached to the side, a communications antenna to the fore, and a spread of solar panels girdled it. During coast the craft would have rotated end-over-end for a bit of artificial gravity, and during flyby there was an unmanned probe to drop off for landing. At the end of the mission a return capsule, nestled in the aft end to that point, would bring the cosmonauts back to the ground.

Both life support and food would have been dependent upon a greenhouse based on Chlorella chlorophyte algae, which was calculated to give better value for mass than chemical oxygen plants: 27 kilograms of oxygen per day per kilogram of algae. The food it made would have been supplemented partly by prepared stores. Getting this plant (no pun intended) up and running was considered the key breakthrough needed for the craft, and considerable work was done through the 1960s. Three men were sealed into a close-looped simulator ecosystem based on it in 1967.

A mockup of the MAVR (MArs-VeneRa) itself—as TMK-1 was renamed once a Mars/Venus flyby path was found that was shorter than the 1000-day mission mentioned above—was begun in 1964 but foundered due to zero funding.

What happened to make it fail: MAVR was ready to roll as exactly the wrong time. Khrushchev had grown disenchanted with Korolev’s follow-up to the R-7 missile, the R-9, and instead was coming to favour the line of storable-propellant missiles developed by Mikhail Yangel. Vladimir Chelomei jumped on this and proposed his own set of manned spacecraft, one of which was for interplanetary voyages, after poaching engine designer Valentin Glushko from Korolev to build his own rockets.

By the time Korolev regained control of the Soviet manned space program he and his nation’s leaders had decided that the gauntlet thrown down by Kennedy for a race to the Moon was serious, and moreover that they should pick it up. The N1 was “stretched” to become a Moon rocket, the Mars mission was put off into the indefinite future, and the rest is history.

What was necessary for it to succeed: Getting people to Mars has turned out to be far harder than expected, so the breezy optimism that had the MAVR at Mars by the mid-1970s is hard to sustain. A lot of things went against it: the early-60s infighting in the Soviet space program, disinterest in space on the part of the Soviet military, Korolev’s egotistic insistence on going head-to-head with Apollo, the shift in the USSR’s manned spaceflight focus to shuttle and space station during the 70s…the list goes on.

One thing that would have cleaned up a lot of them, or at least softened their impact, was the transfer of the space program away from the Soviet military, in particular the GRAU which funded the rockets. They wanted missiles not launch vehicles, and so logically if Khrushchev has been serious about wanting a space program he would have accepted a proposal from Korolev made post-Sputnik that OKB-1 be reorganized as a civilian organization like NASA. It didn’t happen.

One more note: long-time readers with good memories might have noted that the initial dates selected for the mission (though it was extraordinarily unlikely that the Soviets could have hit their targets) were roughly similar to those mentioned in our discussion of the NASA Mars-Venus Flyby. As mentioned in that post, there was a tremendous solar flare in 1972 that, by NASA’s estimate, would have hit anyone outside of the Earth’s protective magnetosphere with roughly 4 grays of radiation, with death resulting in the next few weeks.

A fine image of what MAVR might have looked like as it passed Mars can be seen on the Deviantart page of Polish artist Maciej Rebisz.

Mars Expedition 1969: NASA’s Waterloo (Integrated Program Plan, Part I)

A cutaway view of the Mars craft proposed by MSFC in 1969.

A cutaway view of the Planetary Mission Module (centre) and Mars Expedition Module (right) on top of the Nuclear Shuttle (fully visible on the second ship in the background). Public domain image from the Marshall Space Flight Center, NASA. Click for a larger view.

What it was: NASA’s follow-up to the Apollo program. A manned mission to Mars would have been launched in November 1981, brought twelve men to Mars—six of them landing—and then returned to Earth in August of 1983 (with a flyby of Venus along the return route). There would be two more manned missions by the end of 1985, and a manned base by the middle of 1987.

Details: Neil Armstrong stepped onto the Moon on July 21, 1969 and the obvious next question was “Now what?”

NASA had been answering it intermittently for years prior to this but now they got down to business. In particular, while they supported the Apollo Applications Project they were not content to stick to those missions’ main goal: to find out new things to do with the hardware they had already developed. Quite reasonably they decided that they needed to carry onwards and upwards with their engineering. Not only was a manned mission to Mars the obvious next step from an exploratory standpoint, it had the advantage of requiring that they move beyond Apollo equipment.

To that end they turned once again to Wernher von Braun. This was the culmination of his life dream: he’d published a Mars program in 1948, made a splash with the variant of it published in Collier’s in 1954, come up with another smaller expedition in 1956, and then sponsored the so-called EMPIRE and UMPIRE studies in 1962-64. On August 4, 1969 he made a presentation of what would be his final Mars proposal to the Space Task Group (STG), chaired by Vice President Spiro Agnew.

The mission was to be the penultimate part of a two-decade effort, the Integrated Program Plan, which could really be thought of as “Apollo 2.0”: another vast effort with an end goal, designed to replace the one that had just finished. As such it was part of an integrated whole that developed orbital operations into a finely tuned science, first by practicing with the Apollo Applications Program space stations and lunar base. One of the tools was to be a new space-only booster based on NERVA—which is to say, the first ever nuclear thermal rocket. This piece of equipment, dubbed the Nuclear Shuttle, was intermediate in mass between the second and third stages of a Saturn V, and had a higher specific impulse than any rocket ever flown.

Individual Nuclear Shuttles would be fueled in orbit with liquid hydrogen and used to push men and cargo to the Moon, then the empties returned to Earth orbit when they could be refueled and used again—up to ten times in all. Regular Saturn V launches would occur all through the early to mid-70s, building a space station and generally preparing the necessary infrastructure to be a “gas station”.

Meanwhile the other necessary equipment would be tested as part of an Apollo Moon base (basically a revival of the ALSS Lunar Base, which had been cancelled when new Saturn V production went into hiatus). There would be tests of the Nuclear Shuttle by the end of 1977, and 25 men living on the Moon by 1982.

With all that shaken out, the Mars mission would begin on November 12, 1981 with two ships launched on a Mars-bound a trajectory from low-Earth orbit. Each would consist of three Nuclear Shuttles strapped in tandem and a Mars craft made up of a Planetary Mission Module (PMM) habitation section and a Mars Excursion Module (MEM) lander mated to the tip of the one in the centre. The two side Shuttles would get the centre one and its payload up to speed, then peel loose and re-enter Earth orbit for reuse, while the two diminished mission craft would carry on their way.

There were two because the mission had the unique profile of backing itself up. Strictly speaking only one would be necessary for the mission, but the second would fly in formation to be a lifeboat in the case something went horribly wrong on the first—and the first served the same purpose for the second.

This kind of redundancy was necessary because the mission’s twelve crew were going to be away a long time. They’d arrive at Mars on August 9, 1982, stay there for almost three months, and then return to Earth for August 14, 1983: 640 days in all. In theory you wanted to minimize the weight of what you sent, but no margin for error meant nothing could go wrong without endangering the whole mission. NASA had always operated on the principle that you needed something to work with in case of an emergency, a principle that would prove its worth a few months after von Braun’s presentation when one whole side blew off of Apollo 13’s CSM and the astronauts on board were able to ride the excess margins back to Earth. Away from Earth for far longer than any space mission flown to that point, the Mars expedition would get its margin by literally flying two missions at once.

While at Mars six astronauts would stay aboard the PMM and Nuclear Shuttle combinations, flying in an elliptical orbit (a clever innovation by von Braun which made docking harder but cut the mass needed for the mission in half). After a remote sampler determined that it was safe to descend, six more astronauts would go to the surface in two groups of three aboard the Mars Expedition Modules, a capsule derived from the cone-shaped Apollo Command Module. They would slow down in what had only recently been discovered to be Mars’ very thin atmosphere by combination of a parachute, a ballute (a balloon-shaped inflatable parachute that works well at low atmospheric densities), and finally retrorockets starting three kilometers up.

Cutaway view of a MEM

Cutaway view of a MEM lander. Public Domain image from NASA’s Humans to Mars: Fifty Years of Mission Planning, 1950-2000. Click for a larger view.

A MEM could support its crew on the ground for up to sixty days, then its upper stage could climb back into orbit for rendezvous with the PMMs and Nuclear Shuttles. The latter would then fire up one more time and start the long journey back to Earth on 28 October, 1982.

The mission was not quite done, however. Their trajectory would take them back inside Earth’s orbit on a flyby of Venus on February 12, 1983. While this was a second opportunity for scientific study, it was primarily a speed-shedding maneuver. Four probes would be dropped on the way by.

Having got the right trajectory and speed, the two Mars craft would pull into Earth orbit where they would dock with the space station (while not the Orbiting Quarantine Facility, which was proposed several years later, it would serve the same purpose). From there they would be picked up by the Space Shuttle for the last leg of the journey home. If for whatever reason the space station didn’t exist or wouldn’t be suitable for this, the mission could be designed instead with an Apollo-style command module would let the crew splashdown directly to Earth.

Note that four of the Nuclear Shuttles had returned to LEO near the start of the mission; now the last two had done the same and so had their associated Mars craft. Only the MEMs would have been used up. Accordingly the ships would be refurbished and sent out again in 1986. Meanwhile, a second pair of ships would have been launched early in 1983, and on return be re-launched in 1988. By mid-1989, the intention was to have a 48-man semi-permanent base on Mars.

Bearing in mind that the proposal was part of a larger manned space effort including the Space Shuttle and a Moon base, the total cost of NASA’s programs was estimated about US$7 billion per year through at 1976 and $8 to 10 billion for the few years after that. The Space Task Group accepted von Braun’s Mars proposal and the NASA Integrated Program Plan as a whole, and passed it on to President Nixon on September 15, 1969.

What happened to make it fail: There was an utter disconnect between what NASA thought they should get in funding and what everyone else in the government was willing to give them. Even the Space Task Group was uneasy about the von Braun plan and offered two decompressed (and cheaper) versions of it—one where the Mars landing didn’t take place until 1986 and another where the landing was the goal but there was no set date for it. They still underestimated the opposition they would face.

Mariner 7 flew by Mars the day after von Braun made his presentation to the Space Task Group, and appeared to back up what Mariners 4 and 6 had shown previously: that Mars was a dead world, cratered not overly different from the Moon. We now know that by bad luck these missions happened to photograph the most inhospitable parts of Mars rather than the (slightly) more Earth-like northern Hemisphere, but that realization was in the future. Initial jubilation over Apollo 11 faded within a few months in favour of hard questions about why men had to go to Mars in light of what had been learned.

There was also a strong sense among the public and politicians that the United States had to get its house in order down on Earth. Protests against the Vietnam War were at their height and the country was still reeling from the urban riots of 1968. The Republicans had been voted back into power in the presidency in response (though the Democrats still controlled Congress) and Nixon was to continue the squeeze on the NASA budget that his Democratic predecessor had begun. When his director of the Office of Management and Budget Robert Mayo—an observer on the STG—objected to NASA’s proposal for FY 1971 coming in 29% over the cap he had imposed on them (US$4.5 billion instead of $3.5 billion) he convinced Nixon to put his foot down and NASA’s entire manned space program entered a death spiral.

By the time the dust settled almost all of von Braun and NASA’s programs had been cut. On March 3, 1970 Nixon announced that he’d allow only a truncated Apollo program, one space station (Skylab) and a commitment to the Space Shuttle. NASA would try one more Mars proposal in 1971; Wernher von Braun left NASA in 1972 and died in 1977 even before his proposed mission would have launched.

What was necessary for it to succeed: Almost everything was pointing against a Mars mission being approved in 1969. Public opinion was dubious (a Gallup poll in July 1969 found 53% of Americans against it—as Apollo 11 was going on!), the political interest to explore space was fading away in the Democratic Party as John F. Kennedy receded into the past, and Nixon was struggling with paying for the Vietnam War just as the US economy was sliding into recession. After his presidency various inside sources reported that he had been looking for a way to wrap up Apollo without looking like “The Man Who Killed the Space Program”; ironically, the less-ambitious options included in the STG’s report gave him the loophole he needed to dive through.

One possibility that could have brought about the mission would be a virtual tie in the space race, with the Americans and Russians getting to the Moon in a dead heat or possibly even the Russians getting a man on the Moon first. Under those circumstances the US might have committed to “Space Race, Round 2” and go for Mars. But this is a hard one to get flying, for all that it’s about the closest we’ve ever been to seeing a manned Mars mission. Even if it had been approved how much it would have had to shrink and delay as it rode out the 1973 Oil Crisis and the jittery economic conditions that lasted into the early 1980s is an open question.

Some very nice renders of this mission can be found on the DeviantArt page of Drell-7, AKA Tom Peters.