On 9/11/2016 9:12 PM, Henry Spencer wrote:
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.
"detonation" -- it covers deflagrations, detonations, and things which
are neither (like transformer explosions and BLEVEs).
-- 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
