posted 04-13-2013 08:22 PM            

The Apollo lunar module (LM) descended to the lunar surface in the vacuum of outer space. The LM had to emit significant amounts of exhaust during its descent. Where did that exhaust go? Does it just go poof, gone?

I mean exhaust is tangible and there is no wind or other atmospheric condition that could dissipate it yet gravity would cause these molecules to settle on the surface, no? Could there possibly be a cloud of exhaust in the midst of the LM and the moonwalkers?

posted 04-14-2013 09:23 AM            

I know you can see from the videos the effects of the exhaust what with all the dust flying. I think you may have partially answered my question with Neil's comments that the dust and rocks went over the horizon.

But still I'm wondering what happens to the actual gasses that have been emitted from the spacecraft.

Does a molecule of spent aerozine (or whatever fuel it was) cease to exist. It has to go somewhere doesn't it?

Mr. Armstrong said it could have been pushed over the lunar horizon. Are there molecules of aerozine still present on the lunar surface.

posted 04-14-2013 09:45 AM               

When a LM landed, most of its exhaust went off into space and some (between 20% to 30%) became part of this gaseous envelope ... temporarily. Sunlight would break the exhaust molecules down into their lighter components, which would eventually escape the lunar environment.

Also adding to the envelope would be outgassing from the remaining propellant in the tanks of the LM descent stage and the various gases in the tanks of the astronauts PLSSs (when they were using them and when they were discarded on the lunar surface). Also, the ascent engine's exhaust made a smaller contribution.

These "contributions" were measurable by certain ALSEP experiments.

I believe an Apollo 12 ALSEP experiment even detected the exhaust from Apollo 14s Antares LM during its ascent phase (Antares almost passed over the 12 landing site during its ascent). I remember reading an estimate of how much exhaust, in kgs, remained in the lunar environment (temporarily), but do not recall the figure. It might be in one of the Apollo Preliminary Science Reports.

posted 04-14-2013 03:06 PM               

quote:

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Originally posted by Shikedants:
Are there clouds of exhaust gasses in orbit around the Earth, Moon or Mars? If so, would these clouds cause spececrafts' orbits to slowly degrade over time?

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Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum. But no vacuum is truly perfect, not even in interstellar space, where there are still a few hydrogen atoms per cubic meter.

posted 04-14-2013 04:43 PM               

A-50 Aerozine-50 Fuel
50% N2H4 Hydrazine : 50% N2H2(CH3)2 UDMH Unsymmetrical Dimethyl Hydrazine

NTO Nitrogen Tetroxide Oxidiser
N2O4 Dinitrogen Tetraoxide <--> 2 NO2 Nitrogen Dioxide

Boiling Temperature T (Earth)
A-50 76.9 C to 105.9 C
N2H4 113.5 C
UDMH 63.9 C
N2O4 21.1 C
Source

The primary combustion products of Aerozine-50 and Nitrogen Tetroxide consist of H2O (Water Vapour), N2 (Gaseous Nitrogen), CO (Carbon Monoxide), CO2 (Carbon Dioxide), H2 (Gaseous Hydrogen), and OH (Hydroxyl Radical). Over 50 secondary chemical reaction products have been reported and more complete details of the chemistry can be found here.