[AR] Re: SpaceShipTwo crashes shortly after Mojave test flight
- From: Anthony Cesaroni <acesaroni@xxxxxxxxxxx>
- To: "arocket@xxxxxxxxxxxxx" <arocket@xxxxxxxxxxxxx>
- Date: Sat, 1 Nov 2014 19:00:42 -0400
It's analogous to try curing diarrhea by changing the plumbing around in the
toilet.
Anthony
Sent from my iPhone
> On Nov 1, 2014, at 6:52 PM, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
> wrote:
>
>> On 11/1/2014 10:19 AM, David Weinshenker wrote:
>> Henry Vanderbilt wrote:
>>> The white cloud was almost certainly the nitrous supply venting.
>>>
>>> Ken Brown's photos can be seen at http://i.imgur.com/bfGB0da.png.
>>>
>>> All what follows caveat "as best I can tell."
>>>
>>> The first shot shows what looks like a clean burn just after dropoff and
>>> start. (Hard to say for sure from a still; rocket motors can look just
>>> fine in stills when a vid might show significant pressure variations.)
>>
>> Hmmm... comparing the photos at this link with the nydailynews.com link
>> below... that has what looks like a post-drop photo a little earlier in
>> the burn sequence, with SS2 slightly behind the carrier plane - vs. the
>> first image in the link you posted which shows it having pulled about
>> even (as seen from the camera angle): the exhaust plume appears very
>> different in the first and second images (presumably from the same
>> camera, closely spaced in time, so the photographic transfer function
>> should be consistent...): the first one has a very luminous plume,
>> to the point of apparent probable saturation of the color rendition.
>> The second image shows a much paler plume with visible "shock diamonds",
>> almost transparent. I don't know how they light that thing - it could be
>> that the first image represents part of the ignition sequence, with the
>> output of a solid-propellant igniter charge contributing to the visible
>> plume - but if both images represent "mainstage" hybrid combustion, it
>> looks like there might have been a -major- combustion mixture ratio shift...
>
> From watching previous flight test vids, they seem to flight-start their SS2
> hybrid with some sort of igniter charge that vaporizes then lights the fuel
> grain. (The sequence in the past has looked as if it almost went out before
> the main burn stabilizes - this may be an artifact of partially-burnt fuel
> smoke hiding the flame late in the igniter burn and early in the main burn.)
>
> The sharp square end to the whiter portion of the plume in that post-drop
> first photo at your dailynews URL
> http://www.nydailynews.com/news/national/virgin-galactic-spaceship-crashes-test-flight-article-1.1994672
> is very likely where the igniter first lit.
>
> Note the thinner vapor plume extending farther aft beyond that, at a slight
> angle to the WK2 engine plume. They started injecting something else before
> they lit the igniter. I wouldn't think they'd start nitrous flow before
> lighting the igniter; that would seem begging for a hard start, but perhaps
> our hybrid experts might clarify this point. (Methane injection, maybe? See
> below.)
>
> The bright orange exhaust flame is likely a combination of the igniter plume
> plus the main burn just starting up and possibly still somewhat fuel-rich.
> (Methane? I've seen somewhere that this latest RM2 version injects both
> helium and methane into the motor at various points, and methane burned
> fuel-rich gives a reddish flame. That's speculative though, as I haven't
> seen their actual motor operating sequence described anywhere.)
>
> Henry
>
>
>
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