Kicking up Moon dust

This article makes a passing comment about Moon dust staying in the air long than could be explained by the Moon’s gravity, but if it went into any detail on it, I missed it.

My understanding: If you kick up Moon dust, in the absence of any significant atmosphere, it’s going to fall back to the Moon at the same rate as a rock or a feather—and not just float around and waft to the ground as it would on Earth.

So. . . what was the deal with Moon dust? Or is this another piece of evidence in that Moon landings having been faked? OK, just kidding on that last one

I’m no moon geologist, but I’ve never heard about moon dust floating weirdly outside of the claims of moon landing hoaxists, and the explanation seems wrong to me.

Dust which is kicked up on the moon falls at the exact same rate as any other object on the moon, as there is no atmosphere to suspend dust particles. This is clearly visible on the Apollo movies. This would be impossible to fake, as there is no vacuum chamber in the world large enough to film some of the Apollo sequences in. This is yet another piece of evidence that the Apollo missions were not faked.

Sorry I am confused,
A researcher using a new device examines 40 year old Moon dust and explains why it does something we didn’t understand, is evidence that the Moon landing was faked? Please explain.

CAPT

Some Moon dust may be so fine it remains suspended because of electrostatic repulsion.
see


but it seems to be a very small effect.

Yeah, that was the part I missed. Thanks.

Plus the movies from the moon show dust flying in parabolic arcs which I do not blelieve can happen in air.

That assumes that gravity is the only force acting on it. Static electricity also affects dust, though, be it moon dust or regular old Earth dust.

The Moon would be a favorable environment for static electricity, since it’s very dry there.

The deniers look at the footage of dust kicked up on the Moon, and notice that it looks really weird. They say to themselves “Wow, that’s really weird; it must be fake”. But what they should say to themselves is “Wow, that’s really weird; it must be real”. The reason it looks weird is because it occurred under conditions so unlike those we’re familiar with, because they really were on the Moon. If it had been filmed on a soundstage, the dust would have behaved like dust anywhere else on Earth, and looked normal.

Not to mention being bombarded with Protons from the Sun all the time…

Before the Apollo 11 landing, I was specifically looking forward to watching the dust being kicked up to see it arc back down and I wasn’t disappointed.

Even without taking static charge into effect, there are a couple of other things that make the dust streams look weird. One is the 1/6th gravity. So they fall rather slowly. One could be fooled into thinking they were sort of floating.

Secondly, the particles in the stream are bouncing off each other. This creates a dispersive effect that spreads things out a little. Some particles might take a bit longer to drop since they got bounced a little more by other, larger particles. So it won’t be a uniform arc.

There might even be enough tiny (nano?) particles that a sort of flow occurs, and then things get complicated.

Being dry, of course, makes it easy for dust of the Lunar regolith to retain electrostatic charge, but lacking an atmosphere to intercept the incoming solar wind also means that the surface is constantly bombarded by charged particles. The result is a highly charged environment, which causes the dust to be easily disturbed, and incidentally, to stick to any body that is differentially charged. Note, also, that the low gravity of the Moon not only causes the dust to return more slowly, but also allows it to be kicked up in a higher and wider arc than would be the case in a terrestrial environment. Even a cursory search on “Moon dust” will turn up a number of NASA and academic research papers on the behavior of lunar dust and the hazard it presents to equipment and (potentially) the health of astronauts.

The “it looks weird, therefore it must be fake,” is a standard meme in both Moon landing deniers and other space conspiracy arguments. There was a previous thread on the Chinese manned space launch and how it must have been faked because (based upon a poorly made YouTube.com video narrated by Hugo the Abominable Snowman) the movements of the taikonaut and his support equipment looked “weird” and artificial. As Chronos notes, to any skeptical observer, this should be considered an argument for the positive, as we should expect the mechanics of objects and people in freefall and vacuum to be very different from what we see in terrestrial conditions.

As for “…another piece of evidence in that Moon landings having been faked?”, I’ll have to point out that faking the Moon landings would require a conspiracy involving tens of thousands of engineers, technicians, and scientists to create a technically realistic effort to develop a super heavy launch vehicle and spacecraft. It would have been logistically more difficult to fake a Lunar landing than to actually just go there.

Stranger

Thanks for the responses, all. I’m a little surprised that there’s been so much discussion on Moon landing hoaxery, based on a little aside I tossed in at the end for a little levity (see note immediately following), but it answers the question all the same.

Is the lack of an atmosphere the main reason the launches from the moon (for the return “up” to the CM) – filmed by remote-link videocameras placed on the moon before takeoff – look so odd? That is, they look so different than the Saturn V launches on Earth a few days earlier. No dramatic buildup of billowing smoke, just a quick spray of glittering debris and the craft is up and gone.

I guess the other factors are: 1. Much lighter payload (hence, much less thrust); 2. Less gravity to work against; and 3. No need to build up to such a great final speed, hence the initial liftoff can actually be faster (I hope that makes sense – does it?).

Still, even given all these factors, I’m surprised at how dinky (and quick) the liftoff looks. Like a child’s popgun, if the Saturn V liftoff were a giant cannon.

I had never considered the issue of static electricity on the moon. If it is indeed a highly charged environment, did NASA people ever worry about the LEM’s electronics being shorted out by a huge lighting bolt as it approached the lunar surface?

Partly - the exhaust of the lunar ascent stage was clear, so there was nothing to see except debris blasted away by its force. With the Saturn V, the exhaust was water vapor, which quickly condensed to cloud droplets.

I believe the Saturn V was just a hydrogen-oxygen reaction, and didn’t have any solid rockets. The space shuttle’s two big boosters are solid fuel, so the exhaust from them is some kind of aluminum salt IIRC.

The first stage of Saturn V was liquid oxygen and kerosene. That is why it is so spectacular. Oxygen Hydrogen is essentially colourless - the shuttle’s main engines have little more than the blue Mach cones visible. Other oxygen hydrogen motors are similarly colourless.

The LEM ascent stage was nitrogen tetroxide and hydrazine. There are some very interesting aspects to this engine. Because the fuel is hypergolic - reacts upon mixing, there is no need to provide an ignition system. The pressure to feed the motor was supplied by tanks of helium carried in the LEM. So no pumps. There was simply a combustion chamber (no moving parts) the bell was ablatively cooled (no active cooling system needed) and a dual redundant valve that once opened allowed the fuel to flow into the combustion chamber. It was designed to be as simple as humanly possible to engineer. Interestingly the ascent engine was still more efficient than the F1 engine on the Saturn first stage. 311s versus 305s, in vacuum. Operating in a vacuum helps a lot, the F1 at launch and operating at sea level only had a specific impulse of 260s.

There was essentially no pre engine ignition sequence, just arm the system, open the valves and away you go. Apparently there was some gentle ribbing in the Apollo program about the asymmetry of the two launches.

You can’t have sparks in a vacuum.

Thanks, Francis and Curt. That makes sense.

I don’t mean to hijack, but maybe someone could briefly address the other aspect of my question…the relative quickness of the lunar ascent launch. By this I mean, besides the lack of immediate pre-launch “buildup” (which you explained well), the first minute of the launch itself is so much quicker than the Saturn V. Maybe this is just due to the differences in weight of the two craft? That is, it’s always best to accelerate to “crusing speed” as fast as you can, but with the Saturn V you have to build up slowly just because the darned thing is so heavy that anything faster in the first minute would require a nuclear-sized explosion?

It’s also that the moon’s gravity is much lower, which means it didn’t need to build up that much speed to reach escape velocity. The “cruising speed” was significantly slower.