Thursday, May 08, 2008

Jim Oberg's article on the recent Soyuz re-entry anomalies

Spaceflight is dangerous. It won't be anything routine and safe like air travel for a long time to come. The forces involved in launch and landing of a spacecraft are enormous and the vehicles us feeble humans have ingeniously designed and built are just barely in control of those forces.

The recent Soyuz re-entry that brought the Expedition 16 crew back to Earth is a prime example and reminder of that. One failure can spell doom for a ship and her crew as we are from time to time reminded so horribly by accidents like that of Columbia most recently and of Challenger, Soyuz 1 and Apollo 1. Happily, in this case, the failure appears to have been overcome by a design improvement after a similar re-entry glitch in early 1969 that nearly claimed the life of a Soviet Cosmonaut. It appears likely that the service module that supports the Soyuz spacecraft in orbit with rocket engines, supply tanks, and solar panels failed to separate from the re-entry module. And like a paper airplane, the combined vehicle began re-entry nose forward with the heat shield still nuzzled between the entry module and the service module. The front of the entry module is not designed to withstand the temperatures the heatshield is there for and not only contains a fragile hatch, but the parachutes that are needed to safely land the crew on the ground at the end of the flight. The new design which Oberg believes had been untested to this point allows the service module to break free during re-entry as the temperatures and atmospheric stresses build up on the vehicle even if the separation bolts fail to fire.

For more details, read Oberg's article here.

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