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General Discussion => Q&A Section => Topic started by: oxford750 on 03/27/2009 05:47 am

Title: Space Shuttle main Engines
Post by: oxford750 on 03/27/2009 05:47 am

To whom it may concern,

How can the main engines go through such a range of temperature changes at ignition (from super cold to super hot) without exploding and what role does the hydrogen flowing around the bells play in preventing cryo shock?  What is cryo shock any way.

Explain as simply as you can please.

Thanks
Oxford750

Title: Re: Space Shuttle main Engines
Post by: Jim on 03/27/2009 06:12 am

Quote from: oxford750 on 03/27/2009 05:47 am

To whom it may concern,

How can the main engines go through such a range of temperature changes at ignition (from super cold to super hot) without exploding and what role does the hydrogen flowing around the bells play in preventing cryo shock?  What is cryo shock any way.

Explain as simply as you can please.

cryo shock is going from room temps to cryp temps quickly.  It can cause uneven contraction of materials

The engines are conditioned before launch to take the temp differences.  Liquid hydrogen and Liquid Oxygen is recirculated to condition those area that will see those temps. 

hydrogen flowing around the bells is for cooling and not for preventing cryoshock

Also areas that see super cold do not see super hot.  The nozzle is not at the same temps as the pumps

Title: Re: Space Shuttle main Engines
Post by: oxford750 on 03/27/2009 04:53 pm

Thanks for the answers Jim. I just assumed that since th exhast comes out of the "bells", it would be the same temprature as what is inside the engine?

Oxford750

Title: Re: Space Shuttle main Engines
Post by: Martin FL on 03/27/2009 04:55 pm

If it's SSME fun you seek, here's a good thread:
http://forum.nasaspaceflight.com/index.php?topic=15312.0

Title: Re: Space Shuttle main Engines
Post by: Jim on 03/27/2009 05:05 pm

Quote from: oxford750 on 03/27/2009 04:53 pm

Thanks for the answers Jim. I just assumed that since th exhast comes out of the "bells", it would be the same temprature as what is inside the engine?

There would be a slight gradient as the gases leave the combustion chamber and travels out the nozzle

Title: Re: Space Shuttle main Engines
Post by: brad2007a on 08/30/2013 02:00 am

I have a question about the SSMEs from STS-1. I saw a chart posted here once, showing the flight history of the SSMEs, but I've wondered, after the ones that flew on Columbia STS-1 to STS-5 were removed, they were never used again (unless I missed something). Were they given to museums? Scrapped? Modified, given new numbers and used again?

Just wondering...

If this question HAS been answered, please point me to the correct thread. Thanks.

Title: Re: Space Shuttle main Engines
Post by: Jim on 08/30/2013 08:42 am

There were more than 40 SSME's built.  Many of the early ones went to museums, even before the end of the shuttle program.  There was one in the NASM, at the LC-39 observation tower, at MSFC, etc.

Title: Re: Space Shuttle main Engines
Post by: 93143 on 08/30/2013 08:49 am

Quote from: Jim on 03/27/2009 05:05 pm

There would be a slight gradient as the gases leave the combustion chamber and travels out the nozzle

Slight?  Isn't the whole point of the nozzle to convert thermal energy into kinetic energy?

Last I checked, the SSME's nozzle converted something like 2/3 of the heat in the combustion products into ordered motion.  The exhaust is still hot, but nowhere near the temperature of the combustion chamber.

Have I missed the essence of this conversation or something?