Dave-Platt%LADC@CISL-SERVICE-MULTICS.ARPA (Dave Platt) (01/29/86)
Only Steve's first question is answerable in a certain, and objective way... here's my understanding of the situation... Challenger's "escape mechanism" is basically this: if something goes wrong during launch, and the pilot has time to detect it, Challenger can detach itself from the external fuel tank and SRBs and glide back (dead-stick) to a landing strip near the launch site. I believe that there are alternate emergency-landing sites downrange (Africa?). I also recall hearing that the orbiter could (in theory) survive a water landing, and would float for quite some time. Neither of these escape scenarios has ever been tested in practice. There are no ejection seats on Challenger... Columbia (I think) had them for the first few flights, but it was decided that they wouldn't do much if any good during a flight with a full crew. There are evacuation procedures that can be used to get the crew out of the orbiter once it has landed (I saw a videoclip of Challenger's final crew practicing these procedures). The existing escape procedures provide no protection if: 1- Trouble occurs during the first seconds of a liftoff. If Challenger doesn't have enough airspeed to manage a dead-stick landing, it will crash. 2- Trouble occurs so rapidly that the pilot doesn't have the necessary few seconds to detect the situation, make a decision to abort the launch, and detach from the tank & SRBs before they explode (either due to an accident, or due to an arm&destruct signal from the Range Safety Officer if the shuttle launch goes badly off-course). The latter situation appears to be what happened yesterday... even if the shuttle had instrumentation on-board that could have detected the first traces of the apparent burn-through or fuel-leakage (or whatever), the pilot could not possibly have hit the "detach" button (or whatever it is) and pulled the orbiter far enough away from the main tank before the explosion... it was all over within a second or so. In re the range-safety-officer's self-destruct capability... there's an excellent discussion of this system in the most recent Risks digest, posted by someone who did a lot of the software design for that system. He asked that his message not be redistributed without his written permission, so I will not discuss it here... save to say that it looks to me as if he did a very responsible job of ensuring that his part of this system was as proof against failure or subversion as could be managed. Other questions: setback, and/or greater support, and/or alternates? It will certainly be a short-term setback; I wouldn't be surprised if most of this year's planned launches never take place. Figuring out the exact cause of the disaster (if possible) will take months, and correcting any physical defects that led to the explosion will take months more. Clearly, the shuttle mission that would have observed Halley's will never take place, and there's probably no unmanned mission or probe that can take its place (BLAST! It was humiliating enough that the USA didn't send a probe of its own... and now our participation will probably be limited to the American instruments on the Russian probes. What do they say about all the eggs in one basket??). Similarly, the launch of the Hubble Space Telescope will be seriously delayed. In the long term, it could be either a setback or a boost. I imagine that the shuttle program itself has taken some serious damage, and I would not be too surprised if the final decision is "Don't build a replacement for Challenger". The loss of Challenger, and the certain slippage in the shuttle program will probably act as a major boost to the European space program... Ariane (sp?) was pretty fierce competition for the shuttle on a cost/launch basis, and now it's going to be the only game in town for a lot of people who want packages put into orbit during the next year or so. It's quite possible that the loss of Challenger will put some pressure on NASA to go to a more diverse launch-vehicle program... perhaps a combination of disposable multistage launch vehicles for satellites, and a truly reusable hybrid (air-breathing/tanked Scramjet) for manned launches. A lot will depend on how the American people feel about space... most of the public figures who I've seen speak in the last day or so have been quite firm about "pioneering spirit" and don't-let-this-stop-us (I personally agree whole-heartedly), but we'll have to see how many people of the "Space isn't worth the risk of life and $$" ilk begin speaking up once the numbness fades. Although this event is a terrible tragedy, we should remember to keep it in perspective (and urge others to do likewise). There are more people in the USA killed by drunk drivers on any average day than died in the Challenger... and drunk drivers don't usually ask for volunteers. I imagine that the total monetary loss from this disaster is less than the population of the U.S.A. spend on beer in a month... or on the interest to the national debt in a week (I'm just tossing figures around, so no flames please... you get the idea). I just wish that there were something more that we could do for the families and friends of the Challenger crew...