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Ssme Vs RS-68 Exhaust Color  
User currently offlineSCAT15F From United States of America, joined Feb 2007, 318 posts, RR: 0
Posted (3 years 6 months 1 week 5 days 10 hours ago) and read 3139 times:

Does anyone know why the exhaust color of the Space Shuttle's SSME is blue-white (as seen in launches and static testing) and why the Delta IV's RS-68 has a clearly orange-yellow exhaust(as seen in launches and static testing)?

The engine architecture is very similar and they both run LOX/LH2. Shouldn't they be the same color?

2 replies: All unread, jump to last
 
User currently offlineDfwRevolution From United States of America, joined Jan 2010, 755 posts, RR: 54
Reply 1, posted (3 years 6 months 1 week 5 days 8 hours ago) and read 3110 times:

Mostly due to the fact that the RS-68 has an ablative nozzle so it is literally flaking and burning-off to dissipate heat. The SSME is regenerative, so there are no other combustion byproducts other than steam.

There's probably a bit more unburned hydrogen/oxygen escaping and burning at lower temperature (and thus, longer wavelength) than in the SSME, but it's mostly the nozzle.

Quoting SCAT15F (Thread starter):
The engine architecture is very similar and they both run LOX/LH2. Shouldn't they be the same color?

Actually, they are totally different engine cycles. The SSME is a staged-combustion engine while the RS-68 is a gas-generator cycle

[Edited 2008-11-14 14:39:38]

User currently offlineSCAT15F From United States of America, joined Feb 2007, 318 posts, RR: 0
Reply 2, posted (3 years 6 months 1 week 5 days 8 hours ago) and read 3099 times:



Quoting DfwRevolution (Reply 1):
Actually, they are totally different engine cycles. The SSME is a staged-combustion engine while the RS-68 is a gas-generator cycle

O.K. Thanks!
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