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NASA Shuttle Specific Sections => Atlantis (Post STS-135, T&R) => Topic started by: TyMoore on 08/25/2006 03:21 pm

Title: Hydrogen Burnoff Waiver for Space Shuttle Atlantis
Post by: TyMoore on 08/25/2006 03:21 pm

I noticed in an article on this site that engineers were seeking a safety waiver for unburned hydrogen in the event of a pad abort.  They site that the reason for the waiver is that in the event of a pad abort where the SSMEs are shut down before SRB ignition, then the 3 or 4 pyrotechnic burnoff igniters may have already burned out before igniting post shutdown hydrogen plumes coming from the engine bells.

Why not simply install a second or third set of igniters to provide exended burnoff coverage. If they burn for 8 seconds each, then simply installing two more sets of three and igniting them in sequence will give a much longer coverage time. Surely they are far, far cheaper and safer than pad fire and explosion?

Title: Re: Hydrogen Burnoff Waiver for Space Shuttle Atlantis
Post by: MKremer on 08/25/2006 03:32 pm

IIRC the waiver is only for this flight. There may be a change to the igniter system already in work for future flights.

Title: Re: Hydrogen Burnoff Waiver for Space Shuttle Atlantis
Post by: Mark Dave on 08/25/2006 06:18 pm

What do they use to make the sparks?

Title: Re: Hydrogen Burnoff Waiver for Space Shuttle Atlantis
Post by: Jim on 08/25/2006 06:21 pm

A pyrotechnic device

Title: Re: Hydrogen Burnoff Waiver for Space Shuttle Atlantis
Post by: Mark Dave on 08/25/2006 06:24 pm

I see. It reminds me though of the sparklers you get in a fireworks shop. Is that what is used, but in a larger scale, I mean the same material?

Title: RE: Hydrogen Burnoff Waiver for Space Shuttle Atlantis
Post by: Chris Bergin on 08/26/2006 02:44 am

There's a thread on this already, so I'll copy the URL here and lock this one :)

http://forum.nasaspaceflight.com/index.php?topic=4012.msg60391#msg60391