[AR] Re: Falcon 9 flight today
- From: Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 01 Oct 2013 09:37:04 -0700
On 10/1/2013 8:42 AM, Rand Simberg wrote:
> SpaceX is denying it, claiming that initial tracking data is always a
> little flaky. And what could cause an explosion? It has no hypergolics
> on it, AFAIK.
>
A quick search gives numerous references to the F9 second stage using
four Draco hypergolic engines for reaction control. Said quick search
showed nothing about that having been eliminated for this new version, FWIW.
Regardless, an obvious non-RCS candidate for a second-stage explosion
here would be a severe hard (re)start of the second-stage main engine.
(Purely speculative at this point, but clean restarts of LOX-kero
engines depend considerably on complete purging of kerosene from engine
passages after the first run. There is a strong incentive to minimize
use of purge gas in a flight vehicle in order to minimize the mass of
pressure bottles carried along, and thus to implement the minimum purge
that works reliably on a test stand. But kerosene is in general
difficult to purge, and such purging quite plausibly may not work the
same way in free-fall and vacuum as it does at 1 G on a test stand. As
I said though, purely speculative at this point.)
Another more generic possibility here is damage to the second stage
occurring at payload separation - not of course then an issue for
missions requiring a second burn before payload separation.
I would only conclude at this point that the problem was not a subtle
one, given SpaceX's statement that they already know what it is and
don't expect any trouble fixing it.
In general, I don't at all blame SpaceX for minimizing comment on the
matter till more data is in. Rocket operators in general go a long way
out of their way to avoid ever using the word "explosion" in connection
with their operations, and for good reason. But in this case, between
the new orbital object distribution spotted and the South African
spherical-venting-cloud photos, I'd have to say a stage explosion is a
distinct possibility.
Henry V
On 10/01/2013 07:41 AM, Henry Spencer wrote:
Another little fly in the ointment: <http://www.zarya.info/blog/?p=1595>
reports indications that the Falcon 9 second stage may have exploded in
orbit, although after payload separation. Which is not as bad as having
it happen with payloads still on board, but certainly isn't good news.
Henry Spencer
henry@xxxxxxxxxxxxxxx
(hspencer@xxxxxxxxxxxxx)
(regexpguy@xxxxxxxxx)
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