Clark Lindsey points to a study (with which new NASA administrator Mike Griffin was heavily involved) that’s been kicking around for about a year now, apparently popular with some in the astronaut office, proposing an SRB-based crew launch system. Clark notes that “The reasoning is that this system could be developed more quickly than a CEV on a Delta IV or Atlas V since the SRBs are already ‘human-rated.'”
Well, not exactly. At least, they (correctly) don’t say that. As I’ve noted many times in the past, the phrase “human rated” is a very misleading one. What they actually say is that “…the SRM has proven to be the most reliable launch vehicle in the history of manned space flight, with no failures in 176 flights following the modifications implemented in the aftermath of the Challenger accident.”
The reality is that the SRB is not “human rated.” In fact (surprising to many) the Shuttle itself is not. “Human rated” or “man rated” is a phrase that so many misuse that I’d just like to purge it from our vocabulary, because as I’ve explained, it’s really a relic of the sixties. All we can say about the SRB is that it has flown reliably (at least after the O-ring problem was resolved) on our only vehicle that carries crew. As such, it may be the basis of a relatively (as expendable launchers go) safe ride for astronauts.
One thing that I never see mentioned in this concept, though, is how they propose to do roll control. The current SRB has none, because it is part of a larger vehicle, which rolls by gimbaling its nozzles. As a stand-alone system, it would have no roll authority at all, without adding fins or a reaction control system. Is that what those little appendages down at the bottom of the figure in Clark’s post are meant to represent?
In any event, such a vehicle will in fact be a new launch system (and one with a pretty rough ride and probably pretty high accelerations toward the end of the burn)–no one will be able to simply stick a capsule on top of an SRB.
[Update about noon eastern]
I just noticed another depressing little statement in the report: “During the time frame addressed by this report