Re: OT Space Shuttle question

SteveB wrote:
"cavelamb himself" <cavelamb@xxxxxxxxxxxxxx> wrote in message news:M6Gdnfu73MpagPTVnZ2dnUVZ_v_inZ2d@xxxxxxxxxxxxxxxx
SteveB wrote:
<etpm@xxxxxxxxxxx> wrote in message news:4868ecfc.1638074887@xxxxxxxxxxxxxxxxxxx

On Sun, 29 Jun 2008 17:47:58 -0400, Stuart Wheaton
<sdwheaton@xxxxxxxx> wrote:


etpm@xxxxxxxxxxx wrote:

Whenever the launch is shown there is a shot of the exhaust coming out
of the rockets. And there is always in the shot a device that shoots
out sparks horizontally. What is the spark shower for?
Eric
Those are Hydrogen Burn Off Initiators.

They are meant to keep leaking or unburned hydrogen fuel from a failed
engine start from accumulating to explosive levels.

Good Video:

http://www.youtube.com/watch?v=IFXVxc6ms1U

Stuart
Thanks Stuart. I always figured that they couldn't possibly be for
lighting the engines. If they were, then they would need to be
blasting off with the shuttle. Either that, or some astronaut would
need to go on an EVA with a striker. I can just see this poor
spacesuited figure holding a striker around the edge of a rocket
nozzle.
Eric

I'm late on this, but I saw a program a long long time ago that said they were to ignite gases around the base. I thought that plausible, but then looking at that huge friggin solid propellant blowtorch going off, I wondered what extra gas could be hanging around and not ignited. I guess that's why they're sitting there in Mission Control and I'm sitting here in Buck Snort.

As an aside, I nominate Cliff Culprick (sp?) for the job.

Steve

The solid boosters don't ignite until AFTER the main engines are running.

Don't know what starts when, or the exact sequence, but in every launch I have seen, I cannot imagine anything burnable under that rocket not finding an ignition source.

Steve


That's actually the reason they are there. If the SSME's don't fire properly, there's a bunch of hydrogen pouring out of them, the initiators will ignite it before it has a chance to accumulate to dangerous levels and blow the ass end off the spacecraft. They only burn a few seconds until the engines are running full on. Those SSME's get to 90% or better thrust in about 4 seconds, which is the trigger that fires the solids.

Remember this is NASA, suspenders and belt. Especially when you think about the fact that they don't add weight to the ship.

Stuart
.

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