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A comment on SpaceshipTwo crashes shortly after Mojave test flight. Parent comment

Re:SpaceshipTwo crashes shortly after Mojave test flight by seanflyon on Friday October 31, 2014 @04:00PM (#8540802)
> Seeing only the first paragraph, I already know that some rubber in the hybrid engine detached blocking the nozzle and causing the whole engine to explode.

Does this same concern apply to plastic-based fuel? It does seem like a terrible idea to have people in the rocket the first time you try a new fuel mixture.

"During the nine months since the previous rocket-powered test in January, Virgin Galactic switched SpaceShipTwo's fuel mixture from a rubber-based compound to a plastic-based mix — in hopes that the new formulation would boost the hybrid rocket engine's performance."

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Re:SpaceshipTwo crashes shortly after Mojave test flight by Florin_Andrei on Friday October 31, 2014 @08:12PM (#8541736)
A hybrid has a few other failure modes too. One is called hard start:

http://en.wikipedia.org/wiki/Hard_start

Another - nitrous oxide can become explosive in gaseous phase. If enough of it became gas, the oxidizer tank may have exploded.

There are also inherent instabilities of hybrids - higher pressure accelerates the burn, which increases pressure, which...

We'll know more after they finish the investigation.

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Re:SpaceshipTwo crashes shortly after Mojave test flight by TrevorJ on Saturday November 01, 2014 @12:08AM (#8542158)
Based on eye witness accounts saying that the engine appeared to fire once more after a flameout, the hard start scenario may indeed be at play here.
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Re:SpaceshipTwo crashes shortly after Mojave test flight by termain on Friday October 31, 2014 @05:00PM (#8541107)
They tested the polyamide/nitrous engine back in May, I believe.
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