NASA scramjet probe hots up

Booster rocket to blame for destruction?

On June 2 NASA's experimental scramjet - the X-43A - was completely destroyed during a test flight, as we previously reported.

To recap, the X-43A is a prototype hypersonic aircraft, powered by a 'scramjet'. This ducts air directly from the atmosphere, mixing it with hydrogen before combustion. The forward speed of the vehicle provides compression, thereby eliminating the need for conventional jet engine turbines. The speed of the airflow through the engine remains supersonic throughout.

The X-43A was powered by a Pegasus booster rocket, intended to accelerate the vehicle to a sufficient speed for the scramjet to kick in.

About five seconds after the vehicle was dropped from a B-52, there was a malfunction which caused the X-43A and booster to "depart from controlled flight". Ground controllers destroyed the vehicle, the remains of which came down in the Pacific.

Almost two months on, NASA is none the wiser as to the reason for the failure. Robert W. Hughes, chairman of the investigation board admitted as much, adding that the team "was working to fully understand the causal relationship and emphasized that the solution might involve several contributing causes rather than a single cause". He was, however, optimistic that the boffins would eventually get to the bottom of it.

Hughes went on to say that the team has "established a fault tree of several hundred possible or contributing causes that are being systematically investigated. Approximately 70 percent of these faults have been eliminated from consideration. The majority of the remaining faults are in the [Pegasus] booster vehicle control arena".

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