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> The NASA rules for human-rating its own internal-designed craft are way looser than the rules for human-rating commercial craft. SpaceX and Boeing had to jump

by kiratp 4y ago

> The NASA rules for human-rating its own internal-designed craft are way looser than the rules for human-rating commercial craft. SpaceX and Boeing had to jump through way more hoops to get their platforms human-rated by NASA. Can you share a couple of examples of this? Curious...

adastra22 4y ago
The most obvious and glaring example is odds of loss of crew. NASA mandated that SpaceX and Boeing achieve an odds of loss-of-crew no higher than 1-in-270. Except no launch system in the history of NASA has ever had odds these good. The best was the Shuttle with on-paper odds of 1-in-100, but with two failures in 135 flown missions the actual odds were 1-in-67. The Apollo program lost one crew on Apollo 1, and very nearly lost Apollo 13. Gemini 8 also very nearly ended in loss of crew. 1-in-270 is an insanely high bar! I cannot find numbers for SLS, but I also cannot believe that it would be as good as SLS uses a fundamentally less safe rocket design than Falcon 9 or Atlas V. Which is actually a rather on-point observation: NASA human-rating certification is a lot of do-as-I-say,not-as-I-do hypocrisy. The commercial crew contractors had to actually demonstrate safety. NASA, on the other hand, asked Boeing, the prime contractor, to estimate odds of failure for various subsystems of SLS. Boeing wrote many reports explaining in detail why the odds of failure were within acceptable limits. NASA read these documents and said "okay, I believe you." And that is why the SLS is human-rated. This Quora answer does a decently good job of explaining the absurdity of the situation: https://www.quora.com/Why-will-SLS-be-man-rated-after-a-single-flight-whereas-SpaceX-and-ULA-had-to-go-through-so-many-qualifying-rocket-and-capsule-tests-It-doesnt-make-sense https://www.quora.com/Why-will-SLS-be-man-rated-after-a-sing... But also, let me introduce you to the magical concept of a 'waiver'. NASA has very strict rules for what are allowable risks in human spaceflight. If anything exceeds acceptable risk tolerances, the countdown stops or the mission aborts. UNLESS, you can get a 'waiver.' A waiver is a piece of paper that says NASA is free to ignore the identified problem! Cold Florida mornings leads to ice build up on the Shuttle overnight? Waiver! No need to wait until external temperatures are back within design limits. Foam insulation strike on the leading edge of the wing? Waiver! No need to image the impact point with ground-based radar. NASA, quite famously, gives out wavers like candy for its own launch systems. When I was at NASA (admittedly not on the human spaceflight side), whenever we encountered a problem the first question was always "alright, can we get a waiver?" The answer was usually yes for things in-house. But a commercial spaceflight provider? Good luck convincing NASA to give you a waiver for anything that isn't well and truly, quite obviously a procedural hiccup only.

by kiratp 4y ago

adastra22 4y ago

The most obvious and glaring example is odds of loss of crew. NASA mandated that SpaceX and Boeing achieve an odds of loss-of-crew no higher than 1-in-270. Except no launch system in the history of NASA has ever had odds these good. The best was the Shuttle with on-paper odds of 1-in-100, but with two failures in 135 flown missions the actual odds were 1-in-67. The Apollo program lost one crew on Apollo 1, and very nearly lost Apollo 13. Gemini 8 also very nearly ended in loss of crew. 1-in-270 is an insanely high bar! I cannot find numbers for SLS, but I also cannot believe that it would be as good as SLS uses a fundamentally less safe rocket design than Falcon 9 or Atlas V. Which is actually a rather on-point observation: NASA human-rating certification is a lot of do-as-I-say,not-as-I-do hypocrisy. The commercial crew contractors had to actually demonstrate safety. NASA, on the other hand, asked Boeing, the prime contractor, to estimate odds of failure for various subsystems of SLS. Boeing wrote many reports explaining in detail why the odds of failure were within acceptable limits. NASA read these documents and said "okay, I believe you." And that is why the SLS is human-rated. This Quora answer does a decently good job of explaining the absurdity of the situation: https://www.quora.com/Why-will-SLS-be-man-rated-after-a-single-flight-whereas-SpaceX-and-ULA-had-to-go-through-so-many-qualifying-rocket-and-capsule-tests-It-doesnt-make-sense https://www.quora.com/Why-will-SLS-be-man-rated-after-a-sing... But also, let me introduce you to the magical concept of a 'waiver'. NASA has very strict rules for what are allowable risks in human spaceflight. If anything exceeds acceptable risk tolerances, the countdown stops or the mission aborts. UNLESS, you can get a 'waiver.' A waiver is a piece of paper that says NASA is free to ignore the identified problem! Cold Florida mornings leads to ice build up on the Shuttle overnight? Waiver! No need to wait until external temperatures are back within design limits. Foam insulation strike on the leading edge of the wing? Waiver! No need to image the impact point with ground-based radar. NASA, quite famously, gives out wavers like candy for its own launch systems. When I was at NASA (admittedly not on the human spaceflight side), whenever we encountered a problem the first question was always "alright, can we get a waiver?" The answer was usually yes for things in-house. But a commercial spaceflight provider? Good luck convincing NASA to give you a waiver for anything that isn't well and truly, quite obviously a procedural hiccup only.