Interesting topic, Zorgon, thanks!
There appears to be a bit of concern with the effects of lunar dust kicked up by the exhaust gases of chemically propelled lunar spacecraft, according
to the following, somewhat "fluffy" article:
Source | MoonDaily | Watch Out For Flying Moondust
Here on Earth, no one pays much heed to dust or sand blasted out by a rocket launch because "atmospheric drag rapidly slows the lightweight
particles so they fall harmlessly to the ground a few meters from the blast," he explains. But on the Moon? "There is no atmosphere to slow tiny
particles." Small grit can travel enormous distances at high speeds, scouring everything in its path.
This isn't just theory. In November 1969, the Apollo 12 Lunar Module (LM, pronounced "lem") landed about 200 meters from Surveyor 3, a robotic
probe that had landed on the Moon in April 1967. The Apollo 12 astronauts walked over to Surveyor 3 to photograph it and to retrieve some pieces for
return to Earth. Right away, they noticed that most of Surveyor 3, which at launch was pristine white, had darkened to brown--a result of
two-and-a-half years' exposure to extreme lunar conditions.
But the side of Surveyor 3 facing the LM had been sandblasted back to white. In fact, "every bolt, cable, or bracket blocking the spray of fine grit
from Apollo 12 left permanent shadows etched onto Surveyor," Metzger says. From examining the returned artifacts, scientists later calculated the
sandblasting resulted primarily from finest dust particles only 1 to 10 micrometers (0.00004 to 0.0004 inch) across.
The scoured surfaces were also pocked with hundreds of microscopic impact craters ranging from 30 to 60 micrometers (0.001 to 0.002 inch) across
caused by particles of about the same size traveling at high speeds. Moreover, fine grit had been driven into tiny cracks and crevices, including
inside Surveyor's camera.
This evidence concerns Metzger because in a future lunar outpost, high-speed fine grit could scour the reflective coating off thermal control
blankets, roughen the surfaces of windows and other optics, compromise the surfaces of solar panels, and penetrate connectors or other mechanisms on
digging machines or spacesuits, causing friction and even mechanical failure. Well, why not just land far enough away that speeding sand and dust
ceases to be a problem?
Answer: You can run, but you can't hide. Dust particles accelerated by a rocket's exhaust could theoretically travel all the way around the Moon!
Metzger's team has analyzed how the impact craters formed on Surveyor 3 and finds that the particles must have been traveling at least 400 to 1,000
meters per second. "In fact, they may have been traveling as fast as the exhaust gases of the lunar lander-that is, at 1 or 2 kilometers per
Particles speeding horizontally at 1.7 kilometers per second will travel literally halfway around the Moon. Boost that speed to 2 kilometers per
second, and the projectiles can completely circle the Moon. If no mountains got in the way, grit accelerated by a rocket landing could zip entirely
around the Moon "and land back at the rocket's feet," says
I mentioned the above article as being "fluffy" due to a couple of issues.
First, according to a short article from the Lunar and Planetary
the distance from the lunar module to Surveyor III was more along the lines of 160 meters, (actually it was ~163 meters) still a good
distance, but certainly less than the "about 200" meters as stated in the article.
Second, the article simply states, "There is no atmosphere to slow tiny particles."
Which isn't quite
true, since it's been established that there is an atmosphere of a tenuous nature, at the very least:
A Design Study | APPENDIX J | IMPACT UPON LUNAR ATMOSPHERE
The present lunar atmosphere, arising from natural sources with a total rate less than 0.010 kg/s, has a mass of less than 10^4 kg and surface
number densities less than 10^7 /cm^3.
Nevertheless, and the "fluffiness" of the article aside, perhaps this "scouring" effect of high velocity dust could be
a valid concern for
operations on the moon, which was
the main point of this post.
Heck, even the abrasive effect of the dust held aloft by an electrostatic effect should be of concern for any lunar operations.
Warning: Begging your indulgence, the following will digress progressively further off-topic, proceed at your own risk.
Having read the article, my interest piqued, I did a search for more info and images of the event described and came up with the following pics and a
couple of further points of interest.
Source | Johnson Space Center | Experiment Operations
During Apollo EVAs | Experiment: Surveyor 3 retrieval
Possible allusion to atmospheric oxygen(?):
Source | Johnson Space Center
| Experiment Operations During Apollo EVAs | Experiment: Surveyor 3 retrieval
After a 30 month exposure of Surveyor 3 on the surface, the A-12 crew inspected the spacecraft and retrieved key parts from it for further
analysis on Earth...sort of an LDEF of the Moon. The effects of the A-12 LM blast ejecta, micrometeroid effects on electronics (TV camera), cables,
metal structure, mirrors, etc., analysis of the sampler scoop, effect of a low temperature oxygen plasma on the coatings, induced
radioactivity, and microbe survival in the lunar environment, were a few of the studies conducted.
I'm just an artist, does anyone know where the "low temperature oxygen plasma" effects were generated, or indeed what this even means?
Does this have something to do with the lunar atmosphere?
Source | Lunar and Planetary Institute | Apollo 12 Mission |
Science Experiments - Surveyor III Analysis
Concerning life surviving the harsh conditions of space:
Source | Lunar and Planetary Institute |
Apollo 12 Mission | Science Experiments - Surveyor III Analysis
A particularly important aspect of the Surveyor 3 analysis was the search for living material on the spacecraft. Surveyor was not sterilized prior
to launch, and scientists wanted to know if terrestrial microorganisms had survived for two and a half years in space. One research group found a
small amount of the bacteria Streptococcus mitis in a piece of foam from inside the TV camera. They believed that these bacteria had survived in
this location since before launch.
A fascinating design study of Space Settlements held at Stanford University and Ames Research Center in the summer of 1975:
Table of contents: Space Settlements: A Design
An entire page of links to sites concerned with space settlement issues:
Space Settlements: Spreading life throughout the solar system
We now return you to your regularly scheduled topic:
"NASA Admits to Storms and Dust Clouds on the Moon"
[edit on 9-12-2007 by goosdawg]