Apollo Discussions > The Reality of Apollo
Back-up plan for Apollo
raven:
Not to mention, if I am reading it right, the SIVb would have to be man rated, even if the first two stages weren't.
Glom:
--- Quote from: raven on April 05, 2012, 09:03:56 PM ---Not to mention, if I am reading it right, the SIVb would have to be man rated, even if the first two stages weren't.
--- End quote ---
Easier to achieve. The Saturn IB was man rated for Apollo 1.
ka9q:
I've heard the expression "man rated" many times but I still don't know what it really means.
Does it mean a probability of mission failure less than some threshold?
Or does it mean a probability of killing its crew that's less than some threshold?
Donnie B.:
--- Quote from: ka9q on April 06, 2012, 06:04:05 AM ---I've heard the expression "man rated" many times but I still don't know what it really means.
Does it mean a probability of mission failure less than some threshold?
Or does it mean a probability of killing its crew that's less than some threshold?
--- End quote ---
Well, there's this: http://nodis3.gsfc.nasa.gov/displayDir.cfm?Internal_ID=N_PR_8705_002B_
ka9q:
--- Quote from: Donnie B. on April 06, 2012, 01:00:55 PM ---Well, there's this: http://nodis3.gsfc.nasa.gov/displayDir.cfm?Internal_ID=N_PR_8705_002B_
--- End quote ---
Typical NASA bureaucratese - awfully verbose for what it actually says.
Most of it is circular and therefore rather meaningless: "human-rating is making a system safe for humans". The one specific requirement I do read into it is for features to protect and recover the crew even after serious failures that otherwise prevent mission completion.
For the Saturn/Apollo system, these would include a) the launch escape tower and b) the Emergency Detection System (EDS) active during first stage flight. It would also include the related operational considerations of flying a trajectory such that survivable abort options always exist were one or more engines to fail or go "hard over" (experience a steering actuator failure).
By this definition, I'd say the Shuttle never achieved a human rating, mainly because it was never designed to have one. Neither would the Aries I have been human-rated, because certain credible failures (notably a SRB breach during first stage flight) would have been unsurvivable even with an escape tower; the parachutes would have been burned up by flaming chunks of propellant.
The Saturn V also had considerably wider operating margins than most launchers. It could (and actually did) lose engines at certain points in flight and still achieve its mission. Few unmanned launchers even come close.
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