Explosion on a aerospace vehicle

The last flight of the Space Shuttle Challenger ended 73 seconds after the launch in an explosive burn of hydrogen and oxygen propellants that destroyed the External Tank and exposed the Orbiter to severe aerodynamic loads that caused complete structural breakup. All seven crew members perished. The two Solid Rocket Boosters flew out of the fireball and were destroyed by the Air Force range safety officer 110 seconds after launch. According to the NASA version (Rogers President Commission): a steady flame coming (combustion gas leak) from the rocket booster impinged on the external tank which eventually failed, after which liquid hydrogen and liquid oxygen burnt in an explosive combustion. There is another analysis by Chirivella: the ignited liquid hydrogen leaking from the external tank caused its structural deterioration and ignited its contents.

The INITIATING cause of the accident (according to the Rogers Commission)was the failure of the pressure seal in the aft field joint of the right Solid Rocket Booster. The root cause of the failure was a faulty design unacceptably sensitive to a number of factors (effects of temperature, physical dimensions, materials properties, reusability, processing and the reaction of the joint to dynamic loading). According to another version (Chirivella), the external tank experienced small undetected LH2 leakage (< 1.4 kg/s) which was ignited at early stage from the nearby burning rocket boosters.

on-board hydrogen storage, external fuel tanks (liquid and solid fuels)

In the two external tanks there were 1575 m3 of LH2 and 550 m3 of LOX, which was part of the rocket fuel. The actual pressure was about 0.23 MPa. The potential ignition source was adjacent burning solid fuel rocket boosters. According to NASA, O-ring rubber pressure seal at one of the solid rocket boosters eroded by hot gases after approx. 60 s after lift-off. A steady flame developed which was directed towards the External Tank containing the LH2 and LOX.

All shuttle flights were suspended, pending the results of the Rogers Commission investigation, after which NASA implemented investigation recommendations.

Rogers President's Commission issued a series of recommendations to NASA, the first and the most specific one was the redesign and replacement of the Solid Rocket Motor joint and seal. Further, more general recommendations were: 1. The review of the whole Shuttle Program Structure 2. Bringing qualified astronauts into agency management positions 3. To re-design the shuttle safety panel 4. To establish an Office of Safety, Reliability and Quality Assurance 5. To improve communication and break management isolation 6. To improve the landing safety 7. To provide a crew escape system for use during controlled gliding flight 8. To establish a flight rate consistent with NASA resources, and to avoid commercial pressure. 9. To review and improve installation, test, inspection and maintenance procedures rigorous