LM Exhaust question

[JayUtah]

Wasn't the venting manually done - some time after landing?

Yes, so I'm skeptical.

[Allan F]

What about outgassing from the ground? There should be a substantial amount of gas forced into the cracks.

[ka9q]

[in conjuction with Aldrin's "413 is in."  The latter operation poked a non-zero value into memory location 0413, which was consulted by programs whose operation depended on knowing whether or not the LM had landed.

This is how it was possible to go to the moon with a computer less powerful than a wristwatch today. No GUIs.

BTW, location 0413 was in the AGS.

[ka9q]

Still, this residual haze, (13 seconds after the main dust blowout had stopped), has me baffled.

Even without an atmosphere it takes some time for the dust that has been raised by the DPS to fall in 1/6 g.

The LRV video of the last three ascents showed quite a fog around the LM for a while afterwards. The APS plume also tore off quite a bit of descent stage insulation, especially visible on Apollo 15 because the camera operator did not try to track the ascent stage.

[Allan F]

About the DPS venting - wasn't it only the helium pressurizing the tanks that was vented? The propellants would contaminate the immediate environment - it was some quite nasty chemicals to have in the vicinity when walking around in a rubber pressure suit.

[ka9q]

Although the vents let out mostly high-pressure helium at first, they were left open so the propellants would all eventually vaporize and vent too. Both N₂O₄ and Aerozine-50 have substantial vapor pressures so they would not remain in their vented tanks for long. They would also not remain in the immediate vicinity of the LM for long, though they'd probably contaminate the lunar atmosphere being monitored by ALSEP equipment.