By Tim Ventura | 3 February 2020
NASA wants explorers on the Moon by 2024 and they’re preparing for Mars after that. We’re joined by Dennis Bushnell, Chief Scientist at the NASA Langley Research Center to discuss the Lunar Gateway, interplanetary travel, and NASA’s plan to enable the human exploration of Mars without risking the health or safety of explorers.
Dennis, there’s been a lot of change since we last spoke, the biggest is SpaceX’s goal of putting humans on Mars. Is the media publicity and Musk’s ambitious goal putting pressure on NASA?
Well, SpaceX rockets are avowedly cheaper than the Space Launch System, but the Falcon Heavy, which is currently their largest rocket, lacks the payload size we need. So there’s no pressure yet. Once their Starship flies then it might be a different story, but right now, no.
They’re on a pretty tight timeline. Elon Musk has said he wants to reach Mars by 2025, and they’re planning a Starship launch before Spring. Do you have any thoughts on that?
Musk has big goals, and you know, in the end he’s almost always successful, but his projection dates are often not the actual ones. You know, he encounters problems & setbacks like we all do. That’s expected.
Let’s talk about the Moon To Mars initiative and NASA’s preparation for missions to the Red Planet. In “Maintaining Human Health for Humans-Mars”, you’ve written about using cislunar space as a Mars-analog training ground to prepare crews for future missions to Mars. Is that a big part of the reason we’re going back to the moon?
For Mars, we need to certify equipage at Martian conditions, and we don’t have good experimental capabilities to do that here. We need to understand the safety aspects of exposure to dust, vacuum, temperature swings, radiation and timeframes that simulate Martian conditions.
The Moon gives us the opportunity to certify our equipage under conditions that are similar to what we’ll experience on Mars. The lunar dust is a bit different, the vacuum is harder, and it doesn’t have as much temperature swing, but it does have the radiation — a bit more radiation than Mars, in fact.
So the Moon gives us an environment to check out equipment and the human interactions with the equipment in realistic conditions, and that’s something we simply can’t do on Earth. People have tried simulating these environments down in Antarctica, but it’s not the same at all.
#NASA #NASAHEO Current thinking on #Gateway, first component set for launch in 2022. Can utilize Gateway in 2024 ( as soon as EM-3) Logistics module will be delivering supplies to Gateway, reusable architecture, a reusable module that can be put in different orbits pic.twitter.com/sdlPKiCqMm
— Gene J. Mikulka (@genejm29) August 27, 2018
In terms of the Moon, NASA is starting with the Lunar Gateway, which will be a module that’s going to be in lunar orbit. You’re talking about health & safety for manned missions to the surface after that, right?
We’re gonna put boots on the ground on the Moon. Actually having people on the lunar surface is necessary for what I just described. We need to see how the people and equipment interact under actual conditions, and on the Moon, we can get them home on a few days if something goes wrong. The Moon is a good proving & training ground, which is what we’ve been calling it.
It sounds like this creates collaborative opportunities between NASA & SpaceX — where they could use NASA’s lunar presence as a stepping stone to Mars. Is that a possibility?
Musk is certainly on the forefront of private commercial interests in manned Mars missions. He’s stated that he wants to send humans to Mars to hedge the bets for our species against asteroid impacts & planetary disasters — and you know, that actually makes sense. I can’t speak to long-term collaboration — our initial goal is putting people on the Moon to check things out for Mars. That’s the plan.
Now in terms health & safety for Mars missions, you’ve written that right now, “spending more 200 days in deep space is considered an unsafe lifetime radiation dose.” This is a big concern, but you’ve proposed adjusting transit times & adding Galactic Cosmic Radiation (GCR) shielding overcoats for spacecraft to keep these levels down for explorers. Can you explain this a bit for us?
Yeah. Galactic cosmic rays aren’t photons— we’re talking about fully ionized particle radiation between 30 to 50 giga-electron volts of iron nuclei and other species. This particle radiation literally bores holes in you, and it impacts nearly all human physiology adversely.
These GCRs affect your central nervous system, your cardiovascular system, your immune system, and they’re carcinogenic. Now in terms of exposure limits, we’ve got experience on-station at about six months, and people can tolerate that — they’re typically OK once they come back to Earth. There were one or two people who have gone out to a year and the comments were, “Oh, this is worse”. Well, that’s only one year — the trip to Mars is nearly three.
You get the worst of it during transit. When you’re on Mars you don’t have four pi’s to radiant, and there’s a little bit of atmosphere. This makes the Martian radiation more like what you’d get on ISS, within the van Allen belt and with some protection by the Earth’s magnetic field. You only get about 40 to 45% of the full GCR that you get while you’re in transit.
So what are we going to do about it? First of all, when you’re on Mars if you ditch and bury — cover yourself with about four meters of regolith, you’ll be okay. So this business of people wandering around Mars, like you typically see in the space illustrations out there — that’s a no-no.
— SPACE.com (@SPACEdotcom) August 8, 2019
OK, so you’re saying you can find protection on Mars itself, but how do you keep your astronauts safe during transit?
There are several ways to reduce radiation in transit, and the biggest is by reducing the transit time. We have a plan for this & Musk has one as well — both shorten transit time to 200 day round trips instead of three years, which puts back into the six month exposure timeframe.
We have been testing the VASIMR, which is a high-thrust MHD engine at 6,000 seconds of ISP instead of 453.35 that you get with hydrogen oxygen. If we with a nuclear battery producing 25 kW/kg that we’ve invented here at Langley, then we think we can do 200 day Mars round trips.
Musk’s plan is to use ultra cheap space access to put fuel in orbit — and after his rocket gets up there, he’s going to retank. With all of that cheap fuel he thinks he can do around a 200 day Mars round trip, brute force chemical.
So that’s transit times — but we’re also thinking about AI-ISRU production of a spacecraft overcoat made in space out of lunar regolith, about 3 to 4 meters thick. The idea is that before you go to Mars, you would wrap this overcoat around your spacecraft to protect you from GCR — and when you come back, you leave it in orbit for the next trip. Plus, on the spacecraft itself, you arrange materials, particularly water and fuel and other things to protect people as much as you possibly can.
Finally, we’re looking at biological counter measures. CRISPR, genomics and other technologies have been able to create biologics that reduce the effects of the radiation for cancer patients very considerably. We’re making some progress with biological countermeasures to help all this.
"…modern science can offer by way of genetic editing, screening for individuals who may be genetically predisposed to radioprotection, gene therapy, & even cryopreservation and biobanking; astronauts of the future could be equipped with radioresistance" https://t.co/Gc6Ghd2OTB
— Mitchell Kutney (@MKutney) April 4, 2020
Now last time we talked, one concern you’d mentioned was health concerns from the hexavalent chromium & caustic chemistry of the Martian dust. You’ve written in the past about going “dust free” down to parts per billion or less. Can you tell me where NASA is at with this?
Hexavalent chromium is a very well known carcinogen, and parts per billion is what’s been observed for carcinogenesis with it. There was a study in the early ’00s by the National Academy called “Safe on Mars” that talks about it.
Since that time, we haven’t seen much of it, so it may be not as important as we initially thought from the National Academy study, but if it’s there, we’re gonna treat it just like we have to do the rest of the Martian dust, which isn’t quite as nasty. Moon dust is sharper and nastier, but Martian dust is not good.
Our solution is designing equipment with good seals, and if you carefully look at our designs for space suits, habitats, rovers and the rest, you’ll find these kinds of design details are at the forefront.
So Martian Dust is caustic, but perhaps the lack of hexavalent chromium means it’s not as toxic as you’d thought in the past. Does that mean you don’t need the same level of tolerance in the seals & equipment?
What’s interesting about the dust is that the wizards at JPL have had rovers wandering around Mars now for a very long time, exposed to dust storms and everything else. And these were rovers have performed far, far greater than their expected lifetime. So the Martian dust operationally is evidently, you know, from the JPL work in the Martian had boots on the ground in terms of the rovers you know, we can work that. It’s the people, you know, keeping humans pink, warm & healthy on Mars is not easy.
Speaking of life on Mars, do you have any predictions as to whether we’ll find any sort of life when we get there? We’ve found water & organic compounds on Mars already, I can’t help but wonder if we might find more once we arrive.
I double if we’ll find life in craters, unless it’s very well shielded. The radiation on the surface is not particularly good for life to exist there, but some think there could be underground life on Mars given the huge amounts of underground water & ice available.
In terms of manned missions — humans carry some 10,000 plus bugs inside them, so once you put a human on Mars, it’s all over. Also, there’s always the possibility of bugs hitching a ride on the Landers. We do the best we can in the clean rooms and so do other space agencies, but that’s about all you can do.
Up until this point, looking at Mars every way we possibly can, the only thing we found that might indicate life is methane — and there are geological reasons for it to exist that have nothing to do with life. So, ultimately, this is one of the big questions to answer and one of the main reasons we’re going.
About Our Guest
Dennis Bushnell is the Chief Scientist at NASA Langley Research Center, and is responsible for technical oversight & advanced program formulation. Bushnell obtained his M.E. from the University of Connecticut in 1963 and his M.S. from the University of Virginia in 1967, both in Mechanical Engineering.
Reprinted with permission from the author.
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