Yesterday was the third anniversary of the loss of Space Shuttle Columbia and its seven crew on re-entry and on 28 January it was twenty years since the Space Shuttle Challenger's ascent disaster in 1986, which killed its seven astronauts. Now the remainingfleet of three Orbiters is expected to be retired by 30 September 2010, 29 years and almost six months after the maiden flight of Shuttle Columbia in April 1981.
The causes of those two accidents have been the subject of weighty investigations but what has been learnt? Challenger had an o-ring failure because it had been exposed to temperatures below its operational limits and Columbia was struck by debris that had been known about since the beginning of the programme. Both of these failures could have been identified. In engineering there is something called Failure Mode Effect Analysis. Whatever name the NASA engineersgive it itsabout brain stormingthings that could go wrong. Studying the system, or system of systems as some like to call it, for potentialproblems.
But already, beforethe final design is frozen,claims are being made about the safety of the Shuttle's replacement, the new Crew Exploration Vehicle and its Shuttle solid rocket booster based launch vehicle (CLV). NASA reassures us that because the CEV will sit atop its launcher it can't be struck by debris. Fine. So they have solved one problem. But we're talking abouta new highly complex launch system, with two stages and a solid rocketlaunch abort system.
Already NASA has admitted that the CLV will not be the four segment SRB that its USmanufacturer Alliant Techsystems was pushing for CLV prior to the official selection of shuttle derived systems for the Shuttle's replacement. Michael Hecker, head of NASA's CEV development programme, Constellation, told Flight International that the agency was reviewing the SRB casing design. Other space programme veterans have told Flight that the propellant type must have to change as well. The reality is that the SRB for the CLV first stage will be substantially different to the original Shuttle booster, that destroyed Challenger.
What failure modes will it have? What o-ring designs will it use? Then there is the second stage. At the moment it will be of aluminium lithium construction and it looks like it will use a modified version of the Saturn rocket's liquid oxygen, liquid hydrogen J-2 engine, the J-2S. Of course this has to separate from the first stage and then be separated from the CEV. What failure modes could the pyrotechnics have? What failure modes could the J-2S have? Admittedly the Saturn had a 100% safety record. But who wants to take the chance? Then there is the launch abort system...
Those fourteen Shuttle astronauts, the three crew of Apollo 1, Edward Chaffee, Roger White and Virgil "Gus" Grissom andthe Russian Cosmonauts that have died on mission won't be the last to perish as humanity pushes back the final frontier. So let's not hear anymore about how safe the new CEV and its CLV are and talk honestly about how dangerous they will be.