What it was: A last-line-of-defense system for getting astronauts out of orbit by ballistic re-entry when all else had failed. With it the endangered spacefarer could put a heat shield around himself and then skydive from orbit. Backwards.
Details: Getting a spacecraft’s crew out of orbit during a dire emergency has been a problem considered since the earliest days of the Space Age. A capsule returning from orbit hits the air at no less than 7 kilometers per second and needs a heat shield capable of handling something like 2,000 to 3,000 Celsius, which is beyond what even most solid metals can handle. What hope does a fragile person have? Since the mid-1970s the answer has almost always been “none whatsoever” and the solution to most problems in orbit has usually been to scramble another craft into orbit for rescue purposes, a situation that has thankfully never occurred as of this writing. But not everyone has always been so pessimistic (or realistic).
Self-recovery from orbit stems from efforts made at altitudes only moderately lower. By the mid-1950s the Air Force had become concerned with the greatly increasing height at which its planes were flying. The air where they went was so thin and so cold there was no way an unprotected human could survive a bailout, and so researchers and engineers went to work to find out what would be necessary to save a pilot who had to parachute from that height.
First came Operation High Dive, which hoisted dummies into the stratosphere and then dropped them to see what would happen. As well as the anticipated problems, the researchers made the discovery that a human form would spin as it picked up speed, often reaching 200 revolutions per minute—fast enough to kill if it kept up for the duration of the descent. Aerodynamic stability was needed.
Dummies would only take you so far, though: what about blood pressure or the fluid in one’s ears or eyes in a near-vacuum? What about air? What about freezing? Project Excelsior launched in 1959 and saw a person—Capt. Joseph Kittinger, to be precise—make three jumps from a balloon-lifted capsule. He wore a variation on the MC-3 partial pressure suit worn by high-altitude pilots at the time, bulked up with heating equipment and insulation to the point that it verged on a spacesuit. When falling from as high as 31.3 kilometers (where he was above 99% of the atmosphere) he naturally assumed a seated position with his back to the ground, and that discovery led to the proposed approach for orbital rescue in the next few years.
By the early 1960s the Air Force were sending pilots to the very edge of space: on July 17, 1962 Robert White got to 95.9 kilometers in an X-15. Once the X-20 “Dynasoar” was flying, Air Force personnel would be in orbit. Pilots get an ejection seat, that had been standard in Air Force planes since not long after WWII ended. The Dynasoar needed one and that was that.
Douglas Aircraft led off with the Paracone in 1963. Their suggestion was to build a shroud of nickel-chromium-cobalt alloy (René-41, which was also used to make the outer shell of the Mercury capsule) into the pilot’s seat. On ejection the astronaut would use an attached retro-rocket to slow his orbital velocity, then inflate the shroud into a rounded cone some 7.6 meters in diameter with himself in the centre of the concave side. The Paracone would drop into the atmosphere, keeping re-entry heat relatively low through its large surface area and low terminal velocity—only 42 kilometers per hour. The last of the Paracone’s speed would then be bled off the hard way: on crashing into land, it had a crushable nosecone that would have worked much like the crumple zones on modern automobiles. The astronaut could then get up and walk away, thus meeting the formal definition of a good landing, though the initial plan was that he might be as much as 800km away from where he aimed.
At about the same time, General Electric proposed the MOOSE—“Man Out Of Space, Easiest” though this was later backronymed to the more sedate “Manned Orbital Operations Safety Equipment”. This is the most famous of the options for getting out of orbit. It was a simpler and smaller system than Paracone: on ejection the pilot would pull a ripcord on his chest to trigger a canister of polyurethane foam inside a fabric container. When filled this would leave him partially embedded in an ablative heat shield 1.9 meters in diameter. After MOOSE’s solid retrorocket was fired, the pilot would re-enter with his back to the atmosphere. When he approached the ground he would pull a second ripcord on his chest that deployed a parachute—the shock of the parachute catching air would pop him loose of his foam casing and then the MOOSE would be left to its fate as the rescued astronaut drifted down. There appears to be no literature discussing what would happen if the pilot pulled the two ripcords in the wrong order.
As it happened the X-20 was cancelled in late 1963 (to be replaced by the Manned Orbiting Laboratory), but the idea of getting people out of space once more sophisticated stations were built remained. This led to two more proposals from contractors associated with the Air Force and NASA.
SAVER was Rockwell International’s contribution in 1966. The pilot’s ejection seat was virtually all of that rescue pod, and it had a solid heat shield on the back of it. The seat was supported by an inflatable balloon some ten meters in diameter, which slowed the craft to survivable speeds. AIRMAT, on the other hand, was suggested by Goodyear in 1968. Perhaps fittingly for that manufacturer it resembled a small blimp, with two astronauts riding inside it. Both systems once again had the stricken astronauts falling backwards to Earth as a fabric heat shield protected them. Neither design made it off the drawing board.
What happened to make it fail: A few tests were performed on the Paracone and MOOSE concepts. In the former case it was mostly wind tunnel tests to confirm the cone’s terminal velocity and impact tests on the nosecone. MOOSE’s ablative shield was heat tested, and one experiment was run to see if it would orient itself correctly in the air: a dummy wearing a MOOSE shield was tossed off a six meter bridge near Valley Forge, Pennsylvania (some sources say it was in Massachusetts somewhere), landing on its back in the water as hoped and then floating downstream.
But with the exception of a short period during the initial development of the Space Shuttle in the early 1970s, NASA has always taken the position that sending a rescue craft is the better way to go. With either of MOOSE or the Paracone, the agency would have had to develop new training for the astronauts and the contractors would have had to develop new materials and new technologies. At least with a rescue craft they were dealing with a spacecraft that they were going to be developing and testing anyway for the main missions.
So during the Apollo program the idea was to always have another Saturn V and Apollo craft ready to launch if the Apollo craft that was on a mission became stranded in Earth orbit. In the actual event this was not done, as it came to be recognized that the rescue mission was as likely to put another astronaut in jeopardy (the Command Module would have to be unsafely flown by only one person, so there’d be room for the three being rescued), and the de facto situation was that the astronauts in a Mercury, Gemini, or Apollo capsule were on their own once they reached orbit. Skylab did return to the idea with a modified CM that allowed for five on-board.
After the loss of the Space Shuttle Columbia, NASA’s approach for Space Shuttles was to have another Shuttle ready to go within 40 days so that it could be launched on a rescue mission if the first one could not return to Earth for whatever reason. The crew of the disabled Shuttle would simply wait out the interval on rationed air (carbon dioxide scrubbers being the limiting factor). After May 2009, the International Space Station was sufficiently large and capable that the plan became for anyone stranded in orbit to go to the ISS where they can be indefinitely supplied—since that’s the only place American and Russian astronauts are going these days, this is OK. The ISS itself always has a Soyuz-TM capsule attached to it for emergency re-entries in case the station becomes uninhabitable.
What was necessary for it to succeed: Despite the fact that returning from space essentially naked looks at first glance to be insane, there doesn’t appear to be any particular reason why it couldn’t work except for an interest in doing so despite the danger.
With the rise of commercial space flights, the author expects to see sometime in his lifetime a rich adventure-seeker in the mold of Richard Branson give it a shot purely for the sake of doing it.