They're the ones thinking outside the space capsule.
- By James Oberg
- Air & Space magazine, November 2003
NASA Langley Research Center
(Page 4 of 5)
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.
But as days passed without an actual recovery, Russian launch officials were forced to fess up: The 540-pound probe was lost. Accident investigators later determined that Demonstrator 2 had detached from its rocket too early, at around the time Volna’s second stage separated. “Because of the uncontrolled detachment,” their report concluded, “no conclusions can be drawn on its further behavior and on any performance aspects.”
That leaves the IRDT hardware still unvalidated after three tests. Project engineers have made a few minor fixes to their design and plan to try again next spring. So far, they’ve seen nothing that tells them the basic concept won’t work. Astrium (now part of European aerospace giant EADS) and Babakin have even formed a joint stock company, Return and Rescue Space Systems, to produce and sell inflatable reentry systems. But after the loss of Demonstrator 2, Helmut Hoffman, head of the company’s Russian office, told the Russian magazine ITOGI: “The question of the project’s future financing will depend on the test results.”