Why does man-rating cost so much?

[ve7rkt]

What is involved in "man-rating" a launch vehicle, and what makes that process so expensive?

 

[vogon13]

Ever watch some of the early rocket launches ? Zzzzzzpppttthhhhfffffss, blammo!<br /><br />Even shuttle isn't really man rated.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[rogers_buck]

Its the life insurance premiums they have to pay. That and all the rubber crash dummies that get burned up.

 

[najab]

'Man rating' is a term that gets thrown around so much that it doesn't really have a strict definition any more. It traces its origin back to the start of the space program, when boosters originally designed for launching warheads were retasked to launch people.<br /><br />People are a lot more fragile than thermonuclear weapons, so the first aspect of man rating is ensuring that the entire flight profile is benign enough to deliver the astronauts into orbit more-or-less intact. This includes the acoustic and vibration environments.<br /><br />The aspect which gets more attention is ensuring reliability. An ICBM might be allowed to have a failure rate as high as 1 in 10 during boost phase, since the concept of MAD meant that <b>huge</b> salvos of missiles would be flying. The Shuttle, OTOH, is considered risky (and derided as a 'death trap') at 1 in 438, and the astronaut office has a stated requirement of 1 in 1000 for the CEV booster. In order to achieve this high a reliability rating manned boosters undergo <b>much</b> more scrutiny to ensure that its failure modes are understood, and to design against them.<br /><br />Using the Shuttle as an example, every system is given a criticallity rating - meaning the number of steps that component is away from loss of the the vehicle. The APUs (as a whole) would be a Crit 3R - it requires 3 failures and there is redundancy, the SRB ignitors would be Crit 1 - 1 failure with no redundancy. Man rating for the Shuttle meant eliminating every single possible Crit 1 system, and providing redundancy when it couldn't be eliminated (for example, all the pyros have multiple paths for the ignition signal to pass through, with current supplied from two power busses).<br /><br />(Okay, I probably just totally screwed up the Crit rating system.)<br /><br />All this takes <b>way</b> longer and is more expensive when applied to an existing non-'man rated' design than it does during the original design phase.

 

[vogon13]

We had 'loss of vehicle' pounded into our heads a Circle S. Nobody wants a failure mode that goes there.<br /><br />To me. one of the scariest aspect of the 2 shuttle losses is that neither was related to a SSME turbopump throwing a blade or SSME shutdown prior to clearing the tower. Seems like the SSME were the 'big scary thing' before Columbia's first launch.<br /><br />Suspect there are several folks like me wondering if the odds are trying to catch up with the SSME or not.<br /><br />In other words, the 2 losses to date, were to relatively unanticipated causes (o-rings and foam) from technologies seemingly mature in their application to STS. The cutting edge technology, the SSME, have worked very very well, is it because we are lucky so far (which is not so good really) or is it because the engines really are very very good engines?<br /><br />Phrased sarcastically, if we can't even get the o-rings and the foam right, what chance is there of doing something that runs at 6000 degrees F, 30,000 rpm, at 3000 psi right?<br /><br />(I am going to be a nervous wreck before the next launch at this rate, no warm fuzzy feeling about anything, anymore)<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[najab]

><i>The cutting edge technology, the SSME, have worked very very well, is it because we are lucky so far (which is not so good really) or is it because the engines really are very very good engines?</i><p>It's because they are really well designed <b>AND TESTED</b> engines. Every time you blew one up on the test stands (and I understand there were quite a few 'uncontained overpressurization events') you made them safer. The O-rings and foam went through no such trial-by-fire process.</p>