Igniters

[Nate]

Has anyone ever wondered about the igniters on the Space Shuttle's SRB's? I'm picturing something vaguley shaped (and sized) like a volkswagon bus with two pieces of telephone wire protruding. It's kinda scary when the igniters for their SRB make an "O" motor look wimpy!

 

[tquigg]

I've got a friend who's an aerospace engineer who worked shuttle from STS 9 through 19. The "igniter" on the SRB's is indeed something to behold. He's got a picture of one of the propellant segments taken while assembling the stack. Talk about AP heaven!

Best Regards

 

[Nate]

Originally posted by tquigg
I've got a friend who's an aerospace engineer who worked shuttle from STS 9 through 19. The "igniter" on the SRB's is indeed something to behold. He's got a picture of one of the propellant segments taken while assembling the stack. Talk about AP heaven!

Best Regards

oh lordy, I get excited just thinking about it!

 

[Karl]

Originally posted by tquigg
I've got a friend who's an aerospace engineer who worked shuttle from STS 9 through 19. The "igniter" on the SRB's is indeed something to behold. He's got a picture of one of the propellant segments taken while assembling the stack. Talk about AP heaven!

Best Regards

Now thats a picture I wouldn't mind looking at

AP fuel grains the size of a double decker bus

 

[Nate]

Originally posted by Karl
Now thats a picture I wouldn't mind looking at

AP fuel grains the size of a double decker bus

ok well, I just googled it, and it turns out the srb's are only 12 feet wide. ok well....12 feet is enormous, but not large enough for the ignitors to be super huge. maybe like....a "Q" motor or something?

 

[JDcluster]

The core of the SRB's is about 6 ft in diameter....



JD

 

[Nate]

WOW, that's a web thickness of three feet....no wonder it burns for 70 seconds!

 

[cjl]

70 seconds? Try 2 minutes (123s actually) . As for motor equivalent, the SRB's are 4 segment, with a total impulse of 1300MNs (each). Ths gives 325MNs per segment. By my calculations, each segment is the equivalent of a 98% AB motor (with AA coming after Z). In other words, just a bit* more than a Q motor . Also, with a 6 foot core, and the instant ignition that they have, I'd imagine the igniters would be rather large .

 

[Nate]

Originally posted by cjl
70 seconds? Try 2 minutes (123s actually). As for motor equivalent, the SRB's are 4 segment, with a total impulse of 1300MNs (each). Ths gives 325MNs per segment. By my calculations, each segment is the equivalent of a 98% AB motor (with AA coming after Z). In other words, just a bit* more than a Q motor. Also, with a 6 foot core, and the instant ignition that they have, I'd imagine the igniters would be rather large.

OK. I just made up the 70 part for the sake of fun. as for the "Q" motor thing....I wasn't saying people were launching motors the equivlent of the space shuttle at LDRS, I was saying the IGNITER would be close to a Q.
thanks for the useful information, but a bit snippy.

 

[cjl]

Originally posted by Nate
OK. I just made up the 70 part for the sake of fun. as for the "Q" motor thing....I wasn't saying people were launching motors the equivlent of the space shuttle at LDRS, I was saying the IGNITER would be close to a Q.
thanks for the useful information, but a bit snippy.

Sorry if it came off as snippy - it was meant to be light and joking (not at all snippy). Maybe I should a smiley or two. As for the ignitor being a Q - I'd imagine it'd be entirely possible (if not more). I believe that I read once that it has a "small" (which would be huge to almost anyone here) rocket motor at the top of the grain that fires down the core to light it. Can anyone confirm/deny this?

 

[jerryb]

I found this video on nasa.gov of the SRB's igniting...

one of the segments shows a shot up the nozzle i think...

pretty interesting anyway... looks like the grains are fluted... hmmm..

https://spaceflight.nasa.gov/gallery/video/shuttle/sts-upgrades/mpg/up_srbign.mpg

later
Jerryb

Originally posted by cjl
Sorry if it came off as snippy - it was meant to be light and joking (not at all snippy). Maybe I should a smiley or two. As for the ignitor being a Q - I'd imagine it'd be entirely possible (if not more). I believe that I read once that it has a "small" (which would be huge to almost anyone here) rocket motor at the top of the grain that fires down the core to light it. Can anyone confirm/deny this?

 

[Nate]

Originally posted by jerryb
looks like the grains are fluted... hmmm..

Not fluted, they're cast in an 11-point star configuration. that's a whole lotta surface area!

 

[cjl]

Originally posted by Nate
Not fluted, they're cast in an 11-point star configuration. that's a whole lotta surface area!

Yep. According to a NASA website:

The propellant is an 11-point star- shaped perforation in the forward motor segment and a double- truncated- cone perforation in each of the aft segments and aft closure. This configuration provides high thrust at ignition and then reduces the thrust by approximately a third 50 seconds after lift-off to prevent overstressing the vehicle during maximum dynamic pressure.