[AR] Re: Falcon 9 flight today
- From: "Michael S. Kelly" <mskellyrlv@xxxxxxxxxxxxx>
- To: "arocket@xxxxxxxxxxxxx" <arocket@xxxxxxxxxxxxx>
- Date: Tue, 1 Oct 2013 15:54:40 -0400
If the LOX is not depleted, and the relied valves don't work, the stage can
eventually burst by overpressure.
Sent from my iPhone
On Oct 1, 2013, at 12:37 PM, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
> 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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