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Post by Nowhere Man on Aug 25, 2010 20:04:13 GMT -4
Looking somewhat charred form the RCS thruster, I think. Maybe. The RCS used MMH and N 2O 4. How hot does that get? The color looks like nitrogen oxides. Fred
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Aug 25, 2010 21:21:16 GMT -4
Looking somewhat charred form the RCS thruster, I think. Maybe. The RCS used MMH and N 2O 4. How hot does that get? The color looks like nitrogen oxides. The CM used MMH but I think the SM used Aerozine 50. Nonetheless, the performance is about the same. The combustion chamber temperature was probably about 3000 K but this drops considerably as the gas expands and the pressure drops. I don't know the thruster specifics, such as chamber pressure and expansion ratio, but I can make some reasonable guesses. I'm ball-parking that the temperature at the nozzle exit was about 900 K. Once the gas hits the vacuum of space, its going to expand and cool rapidly. The temperature might be down to a few hundred degrees by the time it hits the fairing. By the way, the umbilical fairing was offset slightly to the side so it was not directly in line with the RCS thruster. The exhaust would, however, hit the face of the fairing that we see in the photograph. I'm not sure if we're seeing residue deposited on the fairing or discoloration due to heating, but I think it a good bet that the RCS caused it.
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Post by chew on Aug 26, 2010 12:56:45 GMT -4
Some info on the timing of separation from history.nasa.gov/afj/index.htmRendezvous radar tracking is normally done a number of times prior to ascent, when the CSM passes over the landing site. Not only does this verify the operation of the radar and the tracking software, it provides accurate position and velocity data of the Command Module in the event ground updates are not possible. An alignment of the guidance platform is done, using the Moon's gravity as a vertical reference, and a star as its other reference. At the same time, the most up-to-date landing site location data is relayed to the LM's computer by the ground controllers. The Abort Guidance System is initialized, and loaded with the launch parameters. Next, Program 12, Powered Ascent, is started on the guidance computer. The crew provides values for the insertion velocity parameters, and verifies stored attitude parameters. 70 seconds before the launch, the CSM passes over the landing site. At five seconds before ignition, the Commander presses Abort Stage, which detonates explosive bolts holding the two stages together, and fires other charges to propel guillotines that sever wire bundles and plumbing that pass between the stages. At the same time, the Display and Keyboard (DSKY), which has been counting down, blanks and replaces its display with a flashing Verb 99, requesting that the crew authorize ignition. When the LMP presses Pro(ceed) on the keyboard, the normal display returns, and the engine ignites when the count reaches zero.
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Post by Nowhere Man on Aug 26, 2010 19:56:51 GMT -4
The CM used MMH but I think the SM used Aerozine 50. The CM RCS used UDMH/N 2O 4, the SM RCS used MMH/N 2O 4, and the SPS (the big engine) used Aerozine 50/N 2O 4. en.wikipedia.org/wiki/Apollo_CSMEdit to add: Hmph. The infobox in the article says UDMH for the CM RCS, but the CM section of the body says MMH. Fred
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Post by clipperride on Sept 9, 2010 15:30:31 GMT -4
As a sight aside, it is also worth remembering that the LM was designed to be used in various configurations. The Apollo Applications Program, had it gone ahead as originally planned, would have used the decent stage with different upper sections.
One of the planned uses of this module system was to allow for longer duration Lunar exploration. By landing multiple LMs it would have been possible to take more supplies and equipment down to the Lunar suface. Each LM would have had a regular decent stage with different modules added. Only one of the landers would have been needed to return to orbit, so the remaining LMs would not have needed to carry the fuel required for a take-off.
Sadly the cut backs after Apollo 11 meant that the project was cut back and eventually became "Sky Lab".
Regards
Mark
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