That hadn’t stopped other engineers from exploring similar bailout concepts, though. Other companies had learned of the FIRST project, and throughout the 1960s they came up with various ways to improve on it. General Electric produced probably the most famous concept, called MOOSE (the acronym originally stood for Man Out Of Space Easiest, but the name was later changed to the more sober Manned Orbital Operations Safety Equipment). Instead of inflating the structure with gas, MOOSE engineers used fast-setting polyurethane foam to hold a conical shape; the hardware, which fit in a suitcase-like container and weighed 200 pounds, was even tested on a spacesuited volunteer.
Douglas Aircraft had a similar concept: Paracone, an inflatable shuttlecock-shaped structure made of Teflon-coated Rene-41 alloy fabric. The reentry vehicle was slowed to about 25 mph at impact, so no parachute was required, although the astronaut experienced about 10 Gs of acceleration.
The inflatable designs often were met with the same reaction from potential customers and other outsiders. “They were skeptical,” says Robert Kendall, who worked on Paracone at Douglas in the 1960s. He tried to overcome the doubts by pointing to inflatable structures used by the U.S. Navy: “I mentioned common, everyday inflatable structure applications such as truck tires, bags around payloads, vessel-side protective balloons.”
It was still a tough sell, and remains so, even though the idea has resurfaced more than once since then. In Russia, engineers at the Babakin Space Center in Moscow turned to inflatables in the 1980s to produce lightweight vehicles for descending to Mars. The Mars 96 mission included an inflatable aerobraking system to slow down two small atmospheric-entry probes meant to study the Martian weather. But the spacecraft went off course immediately after its launch in 1996, crashing down into the Andes Mountains.
It was that project that led to current interest in inflatable reentry vehicles. While the Mars work was under way in Russia in the early 1990s, officials at the European Space Agency were eyeing a future need to return samples, film, tape, equipment, and other material from the proposed International Space Station (ISS). With cargo estimates running to nearly a ton a year, ESA managers realized that if they used NASA’s space shuttle, they faced shipping charges exceeding $20 million annually.
Then Babakin, in partnership with the German aerospace company Astrium, knocked on the door with a concept for a low-cost ISS Download System, based on the Mars craft, that could return several hundred pounds at a time. In principle, it was similar to the Russian Raduga capsule, which had been used to bring material back from the Mir space station. But this system would be much lighter and cheaper.
ESA was intrigued enough to give the companies almost $2 million for the Inflatable Reentry Descent Technology program, which aims to prove the ability to bring back payloads from space inside an inflatable vehicle. First the team built a probe called Demonstrator to carry a sensor package weighing about 44 pounds. Engineers at Babakin designed a wastebasket-size cylinder to house the instruments and payload and surrounded them with a pair of inflatable shields coated with ablating material. The first “cascade,” as the shields were called, was eight feet in diameter and would slow the vehicle during the first phase of reentry. A second, 14-foot cascade would open during final descent to soften the landing.
In February 2000, a test of the shielded probe came close to success. The Demonstrator hardware flew on the first test of the Fregat, a new upper stage for Russia’s Soyuz rocket. Attached to the Fregat, the Demonstrator made five orbits at an altitude of 375 miles, then separated from the upper stage and inflated its first cascade. Tracked by Russian air defense radars, the vehicle descended as planned, enduring a maximum of 15 Gs, and landed near Orenburg, about 30 miles past the aim point. The good news was that temperatures inside the capsule had remained normal. The bad news was that the second cascade, designed to cushion the final impact, never opened. The Demonstrator hit the ground at 200 feet per second, essentially a freefall.
For the next test, in August 2001, the project bought a commercial launch piggybacked on a converted Russian missile that also carried a solar sail experiment for the Planetary Society, a U.S. space advocacy group. Both payloads failed to separate from the third stage, and neither had a chance to deploy. The inflatable reentry vehicle never even got an official name, and designers worked on making the separation mechanism more reliable.
The next test, called Demonstrator 2, was launched on the same three-stage Volna booster from a Russian submarine, with a planned landing zone in eastern Siberia’s Kamchatka Peninsula. On July 12, 2002, the Volna rose from the Barents Sea and headed east into the predawn sky. Russian space officials immediately declared the launch a complete success and publicly confirmed the landing.