This would be the one of which you took the video. -R
On Monday, September 12, 2016, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
If that's the same instance I'm thinking of, doubly interesting in that
SpaceX may (from the limited public info) have seen something analogous in
their first brief hotfire of a recovered stage.
On 9/12/2016 12:49 PM, Randall Clague wrote:
Henry is not exaggerating here. In the most relevent case, even the
senior (former Air Force, former NASA) AST official who read the
report was impressed.
-R
On Sunday, September 11, 2016, Henry Vanderbilt
<hvanderbilt@xxxxxxxxxxxxxx <mailto:hvanderbilt@xxxxxxxxxxxxxx>> wrote:
Hrrmph. Less than a day in the discussion, and I too have been
sucked into quibbling about side-issues.
Which points out the fundamental problem with this discussion here:
Not enough data to usefully address the core of the matter.
I'd kill to have access to the actual data.
Or even sign NDA's and charge consulting fees... Yo, SpaceX, I have
had notable successes in the past extracting root causes from sparse
data in this sort of thing. Details available upon request.
On 9/11/2016 9:28 PM, Henry Vanderbilt wrote:
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.
Yes, and parts - parts - of the event in question so qualified.
Fortunately, the majority of the propellant involved merely
combusted.
"Explosion" is a much more generic term than
"detonation" -- it covers deflagrations, detonations, and
things which
are neither (like transformer explosions and BLEVEs).
ex·plode/ikˈsplōd/verb
burst or shatter violently and noisily as a result of rapid
combustion,
decomposition, excessive internal pressure, or other process,
typically
scattering fragments widely.
And this is good
-- we need a generic term -- and it should stay that way.
No, that is bad, as we need unambiguous terms for the real
distinction
between "combusted at low velocity more or less in place" and
"propelled
bits at dangerous velocities for significant distances."
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
