[AR] Re: AMOS-6 RUD
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 12 Sep 2016 00:12:04 -0400 (EDT)
On Sun, 11 Sep 2016, Henry Vanderbilt wrote:
...The majority of the fuel and LOX seemed to go up in a mere
deflagration, however. Only an "explosion" in Hollywood.
Or in real life. :-) Boom plus blast wave plus flying debris is an
explosion, however caused. "Explosion" is a much more generic term than
"detonation" -- it covers deflagrations, detonations, and things which are
neither (like transformer explosions and BLEVEs). And this is good -- we
need a generic term -- and it should stay that way.
I find it more interesting that Musk said the Crew Dragon escape would
have had time to work. This may imply that the apparent several seconds
of noisy lead-in to the visible initial explosion actually does
represent things going visibly wrong in the telemetry.
Assuming that he really does mean "with realistic actuation based on the
telemetry values we plan to monitor", and not "with magical actuation just
as things started to go wrong in hindsight" -- with SpaceX one has to
attend to exact wording -- then yes, it pretty much has to mean that there
was some fairly convincing advance notice somewhere.
Even fully automatic abort actuation is likely to need a second or two to
get things going. And I don't know if NASA would consider fully automatic
abort acceptable for crew flights -- they've traditionally had a low
opinion of it, after having a lot of grief with development and debugging
of the Mercury abort system. Gemini aborts were all manual, Apollo
reluctantly accepted automatic aborts for two or three cases (*not*
including on-pad malfunctions) but kept the rest manual, and of course the
shuttle's limited abort options were all-manual. Maybe memories have
faded enough for them to be more accepting, but this is exactly the sort
of thing that gets hardened into "best practices" dogma.
(Which is not to say that I disagree with them on this. Aviation long ago
decided that leaving the choice to the crew was preferable, to reduce
problems with false alarms, even if it did occasionally mean inadequately
rapid response. "If the fire light comes on, and the aircraft has not
already exploded, eject immediately.")
Henry
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