4 ms·
The hydrogen in the Space Shuttle Main Engine creates embrittlement in the alloys of the engine. [1][2] The launch sequence also involved running the engines at
by oroup 11y ago
The hydrogen in the Space Shuttle Main Engine creates embrittlement in the alloys of the engine. [1][2] The launch sequence also involved running the engines at 104.5% of rated capacity. [3] Before Block II of the engines, the turbopumps needed to be disassembled and rebuilt between flights. [4]
I have no real idea how significant coking of the Merlin engine is, but the SSMEs were hardly "clean".
[1] https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement
[2] http://www.tms.org/Superalloys/10.7449/1991/Superalloys_1991_749_760.pdf http://www.tms.org/Superalloys/10.7449/1991/Superalloys_1991...
[3] http://www.interspacenews.com/FeatureArticle/tabid/130/Default.aspx?id=2130 http://www.interspacenews.com/FeatureArticle/tabid/130/Defau...
[4] http://www.nasa.gov/sites/default/files/174534main_ssme.pdf http://www.nasa.gov/sites/default/files/174534main_ssme.pdf
- rtkwe 11y agoIIRC the 104% was additional performance they enabled through upgrades and design improvements beyond the original design not over-driving them.
- mikeash 11y agoThat right. The 100% level was set at some point during the design process. Later they found ways to slightly increase the thrust. Rather than recalibrate all the numbers, they just kept using the original "100%" and called the new level "104%." Basically, it's "104% of what the engineers circa 1975 thought the level would be," not 104% of what the hardware was rated for.