In the case of Shuttle, the central problem was the lack of true development prototypes. Many design decisions would have been made differently if engineers had hands-on flight experience with the new design concepts before critical decisions were made. This was the motivation behind the technology demonstrator rogram, the X-33, X-34, DC-X and X-37. But the problems that caused the loss of Challenger and Columbia were immediately corrected, and considerable improvements in other systems have been made over the years. The unfolding tragedy is the incipient loss of person-centuries of hands-on experience with reusable spacecraft.

http://www.aero.org/publications/crosslink/winter2001/03.html

This method you describe is not only applied to reliability but to the whole spectrum of engineering. The root cause is the lack of proper funding to perform the necessary job. With “this” amount of money we can do the entire job, with 1/10th (or sometime worse!) this amount we can check who has already done a similar job and “extrapolate”

Oh well…

It’s a basic principle of “real” systems engineering that if you don’t have accurate failure rate data on a system, you cannot establish a requirement for redundancy. If the system is reliable, you don’t need redundancy. If the system is unreliable, but you can identify the failure modes and correct the problem that dcauses the failure, then this is almost always cheaper and more reliable than making the system redundant. Conversely, if the system is not reliable, how do you know if one backup is sufficient? If you cannot identify the failure modes, how do you know the backup will prevent the failure? Nevertheless even today there are engineers happily throwing redundant systems into the Orion with reliability numbers that are pulled from vaguely similar equipment in different industries, or are simply guesswork, under the simplistic and superficial belief that redundancy is equivalent to reliability.

In the case of Shuttle, the figure of 1/100,000 was taken not from testing or systems analysis but from a specification. Yet when NASA management wanted to kill the Shuttle they came up with a failure rate of 1/76, roughly the historical rate, which was also nonsense because of course the only historical failure modes had been eliminated by design changes. And I’ve persoally seen the Constellation availability spec used as an estimate of actual reliability under the assumption that it must be accurate because the contractor would be required to meet it! The discussed requirement for a static load factor of 1.4 (vs the 1.25 that was the DOD spec for the Delta IV) is similarly nonsensical. The 1.4 factor was intended to account for inaccurate calculations in the pre-computer days and wear and tear from 100 mission cycles in the Shuttle.

I would caution against the assumption that NASA has any particular expertise in the subject of reliability.

Here’s a reference with some real data: Space Launch Vehicle Reliability

no problem Max I am “Bi ocular” when it comes to reading.

Robert G. Oler

I think I read somewhere that it was meant to work for both and even be applicable to other launch vehicles.

You mean people who believe in the Constitution, and that maybe we shouldn’t be spending our way into oblivion? Yeah, what a bunch of crazy extremists.

I agree that whoever Bennett’s replacement is will defend ATK, if the program is still politically viable. But he’ll provide much better policy in general.

Ha! I said it!

I know how much that bugs Oler, but I had to write it twice because he only reads the posts here with his LEFT eye.

Jeff, I’m somewhat surprised…no, I’m stunned, that you would delve into Utah Republican politics and get it so wrong so quickly.

Bennett’s troubles reside only within the state GOP. The Tea Party candidates (nuts) are challenging any Republican who does not yield to the Tea Party’s brand of conservatism. And Bennett, though conservative perhaps to many, is not to Utah Republicans.

If Bennett clears the state GOP, he does well in state-wide polls and should win re-election handily. If Bennett looses, the conservative who will win will continue his policies opposing Obama’s space plans for one reason–without Ares I, Northern Utah will loose its largest employer and be hammered economically. Either way, Utah will not be in the President’s space plan corner.