The real promise of Japan's asteroid mission

The missing ‘space balloon’
Another highly innovative space device with tremendous potential is also struggling both with peripheral technical problems, bare-bones budgets, and a general lack of respect. It’s the decades-old concept of “landing on air” on return from space.

The inflatable descent system replaces a traditional solid heat shield with an insulated heat-shield-shaped balloon, which is not only lighter, but also is smaller until it is deployed for the descent. The balloon can also widen further during final descent to decrease impact speed to a parachute-like touchdown.

Ten years ago, the European Space Agency began funding a Russian project to modify one of its space vehicles to serve as a cargo return vehicle from the international space station. The Russians had developed an inflatable braking device for their Mars probes, and had suggested a beefed-up version could survive entry into Earth’s atmosphere.

The project became known as the “Inflatable Reentry and Descent Technology” (IDRT), or just the “Demonstrator.” One test flight in 1999 was close to perfect — the small payload canister and the larger rocket stage both survived the searing heat of high-speed entry without the weight of traditional metal, ceramic, or tile shielding. Instead, high-temperature fabric pressurized by nitrogen formed a serviceable shield.

European Space Agency This artist's conception shows an inflatable re-entry shield descending to Earth.

But two later tests failed due to booster problems, and a third test two months ago was also frustrated when the descent vehicle could not be located in the recovery zone in eastern Siberia. The region is covered in deep snow currently, so further searches aren’t feasible, but officials believe the mission may have been a partial success.

The probe radioed telemetric data to a ground station both before, and more significantly AFTER, the period of most intense entry heating. During that critical period, however, an ionization barrier interrupted the transmissions. If the probe followed a different path, as hinted at by the data it radioed to Earth, it might still be findable in this new region, come spring.

Success with this project could quickly lead to deploying similar inflatable landing devices to the space station, where they could bring samples back to Earth in the long gaps between Soyuz and shuttle flights. With slight modifications, the device could serve to bring a person back to Earth, perhaps in a medical emergency. And with an expanded version of the device, larger objects — including shuttle payload bay sized modules — could be safely returned even after the shuttle itself ceases operations.

These imaginative projects need encouragement, and they need the respect they have already earned, albeit without wide recognition. As with the other far-reaching projects, they can help make the space future more than merely an extrapolation (and rehash) of the past.

The bold attempts by Hayabusa, Cosmos-1, Demonstrator, and others have underscored what the poet said, that "Man's reach should exceed his grasp, or what's a heaven for?" Today we can modify it, based on these projects: in space, our reach SHOULD exceed our grasp, because that's what the heavens are FOR.

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