Dust-busting, Lunar Style – Interview with Daniel Winterhalter
As NASA makes plans to send humans back to the moon, this time to live and work there for extended periods of time, one of the most vexing problems they may be faced with is dust. Lunar dust is pervasive and nasty stuff, which could pose health problems for astronauts, as well as problems for mechanical and electrical systems. To explore the potential problems, at the end of January the NASA Engineering and Safety Center (NESC) held a three-day Lunar Dust Workshop at NASA Ames Research Center near Mountain View, Calif. NESC, whose members are spread among the various NASA centers, was established by the agency in the aftermath of the Columbia shuttle accident, to serve as an independent technical review board.
The Lunar Dust Workshop was co-chaired by Daniel Winterhalter, NESC’s chief scientist, based at the NASA Jet Propulsion Laboratory in Pasadena, Calif., and Michael Sims, an NESC associate chief scientist, based at Ames. Astrobiology Magazine Field Research Editor Henry Bortman interviewed Dr. Winterhalter after the conclusion of the workshop.
Astrobiology Magazine: How serious an issue is lunar dust for those hoping to live and work on the moon?
Daniel Winterhalter: It’s been recognized since the Apollo days that the dust on the moon is at best a nuisance, at worst a problem. If you want to go back there for a longer period of time, you will have to understand and mitigate some of the effects that the Apollo people felt. On Earth some contaminants of similar size and characteristics to lunar dust are considered serious hazards to human health, for example in some coal mines.
Crews had problems with coughing and with skin and eye irritation from dust in the landers and return vehicles. Some astronauts reported smells of caldron, a gunpowder sort of smell, as soon as they went back into their lunar modules. They unintentionally brought back vast quantities of dust, attached to their suits, stuck in their gloves, in equipment, and so on. Just physically or electrostatically attached to the suit. When it got back into the pressurized module, they started smelling these oxidation type smells.
Some Apollo suits began to show indications of difficulty due to dust contaminants in the joints. The stuff was very difficult to remove from suit fabrics and other materials. There were also difficulties in the seals intended to preserve lunar samples from atmospheric contamination. Dust was such a nuisance that Gene Cernan, the Apollo 17 commander, said, “I think dust is probably one of our greatest inhibitors to a nominal operation on the moon.”
AM: We have dust around us all the time, but it doesn’t generally cause such serious problems. What is it about lunar dust that’s so insidious?
DW: Lunar dust is different, quite different than anything we have here on Earth, and probably different than what we’ll see on Mars. Components of lunar dust are tiny. Some of them are shards, and some of them are probably chemically reactive.
Dust from Earth, and probably Mars, is created by wind and water weathering of surface features. That means that they’re typically roundish and grain-sized. On the moon, you don’t have any weathering going on. What you do have is impacts by solar wind, primarily protons, and micrometeorite impacts. As the surface material is exposed to the bombardment, i.e., as the regolith matures, shards with size on the order of tens of microns and smaller are produced, tiny particles that in the Earth’s atmosphere would either be levitated away by wind, or rounded by wind and water as they collided with other things. But on the moon, dust particles stay sharp-edged.
Since we don’t have anything like this to breathe in on Earth, it is conceivable that it’s bad for our biological systems, our lungs may not have any way to deal with that kind of thing. This is something that the flight surgeons and the toxicologists are trying to understand.
AM: What were you hoping to accomplish by holding this workshop?
DW: We wanted to bring together a diverse group of individuals currently studying lunar dust issues, with the designers and operators of the hardware that will operate on the moon. That’s number one. And number two, to identify the major engineering, the major scientific and the major medical issues relating to lunar dust and to brainstorm and identify potential solutions to these issues.
The mornings were plenary sessions, talks by experts. In the afternoon, people split up into splinter groups. We had a medical/health splinter; a life support systems splinter, to look at how to look at ways to improve space suits; a mechanical systems splinter, to study things like valves, wheels and bearings; and a basic research splinter, to look at what type of laboratory experiments and theoretical analyses we need to do to understand the nature of the beast more precisely.
A lot of times you find different places within NASA that do similar things from a different point of view. Because going back to the moon is a very large undertaking, we thought this would be a good opportunity: bring them all together in the same room for a few days and let’s talk about it, so that, for example, the life-support-systems people understand what the medical people’s concerns are, what the overlaps are, and what may be missing in their deliberations.
Are these really problems? We don’t really know. Some of the astronauts say, “Aw, it was nothing. It was just an irritation. I had to sneeze for awhile.” Then, of course, you have to consider that they were only there for three days maximum. We are thinking about going for a much longer period of time.
AM: How did the workshop go?
DW: Better than I expected. What came out of the workshop was a delineation by each splinter group of what they saw as their major concerns. What we didn’t get to was to identify potential solutions. We just didn’t have time. So we decided to reconvene in five to six months. In the meanwhile, we will put out a white paper that outlines the issues that we found. And at the next meeting we will attempt to point toward solutions.
AM: How do you address issues that people have strong opinions about when there isn’t any clear scientific evidence on either side? For example, when people stay on the moon for longer times than they ever have before, dust is going to have cumulative effects that have never been seen before. How do you extrapolate?
DW: You do research. This is where the NESC is such a great resource. Say, for example, we have the issue that dust builds up in your lungs over a long period of time. Is that a problem or isn’t that a problem? There are two approaches to this.
The first one is the easier one: you don’t really worry about whether dust is good or bad; you know it’s at least a nuisance, so you engineer correctly to keep the dust to a minimum. Let’s not bring the suits into the habitats or into the space vehicle. Let’s leave them outside. Or you bring them into a sort of a mud room, and you wear a mask while you clean them. But you don’t have to live with it, especially in zero G, where the stuff floats around to the point where you have to put the suits back on, because you can’t breathe or see.
In addition though, I think it behooves us to understand to what extent the dust is dangerous. And there what you do is two things. First you do analytical experiments under the microscope to understand the chemical and physical structure of the dust. Then, possibly, you do experiments on lab animals. And you go from there.
You do those experiments with simulants. We have tons and tons of simulants that are supposed to be like lunar dust, although it’s very difficult to reproduce. You can only get some of the physical and chemical characteristics, but evidently not all of them. And, by the way, that was a big part of the discussion, how to make better simulants of lunar dust.
We also have quite a bit of lunar dust left over from the Apollo missions. Quite a few samples have been brought back, and they are kept in a modern facility at the Johnson Space Center. So the curator of the Apollo samples came to tell us what shape they are in.
As it turns out there are some problems with many of the samples brought back, and little or none is available in a pristine (original vacuum) state. Some of the samples were exposed to, and have reacted with, air and humidity during the transport back to Earth, or during early storage. Others, in containers with intact vacuum seals, suffered contamination from polishing compounds that were applied to the interior surfaces of the metal containers. It should be stressed that for many applications these samples are still of great usefulness.
Depending on what property of lunar dust is to be investigated, it may be sufficient to have samples that were kept in nitrogen, and some of these have been, and are, being used. There are still other investigations where preservation is not much of an issue. In any case, investigators who need lunar dust make an application to NASA, and a review board judges as to whether or not the request for the precious material will be granted.
AM: How do you go about creating simulated lunar dust?
DW: To show my ignorance about this, I think it is a black art. I’m not an expert in this. The mineral grains found on the moon consist of feldspars, pyroxines, olivines, metallic iron, glasses, etc. Geologists go out and find areas in the ground here on Earth that are similar to lunar dust in terms of chemical makeup. For a simulant called JSC-1, they used an area – I think it’s in New Mexico – that’s essentially a volcanic cinder cone. And they found that it’s fresh enough that it hasn’t weathered much yet. They put that through machines to produce the right particle size distribution: so many percent on the order of 500 microns, another percentage at 50 microns, down to a micron. But it has to be understood that no one simulant has all the properties of lunar dust. Some were made to resemble a certain mineralogy composition, others a particle-size distribution, and other chemical and physical characteristics.
AM: So how long do you expect this process to take? Are you looking at a couple of years, a couple of decades?
DW: Oh, a couple of hundred years. No, actually, I like how quickly we made progress, by just getting people to talk to each other. There were a lot of raised eyebrows, and, “Oh, I didn’t realize that” between experts, and that’s a good thing. Because the lunar architecture design and building is starting soon. So by the end of this summer, we should have a document out. We’re not trying to make requirements here. We want to make sure we understand what the issues are, and how we can forestall problems. And we need to make sure we have ways to add mitigation technologies into the process later on.
In the Apollo days, they were concerned about getting there. That was primarily it. Everything else took a back seat to that. Now we know we can get there, so we need to worry about the fine points, because we want to actually go live there. It’s on quite a different scale now. The last exploration event of this significance was probably the human settlement of Australia 40,000 years ago. And then the human settlement of the Americas 20,000 years ago. And now we’re doing something that is on the same scale, on the moon. And perhaps on Mars. But it’s going to go a lot faster than it happened back then.
