Submitted via IRC for takyon
An article at SpaceNews.com asks Is the Gateway the right way to the moon? — the "Gateway" is The Lunar Orbital Platform-Gateway.
This article originally appeared in the Dec. 17, 2018 issue of SpaceNews magazine.
Sometime in 2028, competing for attention alongside a presidential election and the return of the Summer Olympics to Los Angeles, NASA will return humans to the surface of the moon.
A lunar lander will depart the cluster of modules in an elliptical orbit around the moon, called Gateway, and descend. One stage will take the lander to a low lunar orbit and then separate, after which the descent module will handle the rest of the journey to the lunar surface. A crew of up to four will spend days — perhaps up to two weeks — on the surface before boarding the ascent module, which will take them back to the Gateway.
At least that’s NASA’s plan for now. A year after President Donald Trump formally directed NASA to return humans to the moon in Space Policy Directive (SPD) 1, the agency has developed the outlines of a plan to carry that out, while emphasizing the language in the policy to do so in a “sustainable” manner and with international and commercial partners. But as the agency describes two of the biggest elements of the plan, the Gateway and a “human-class” lunar lander, it’s still struggling to sell the proposal to its various stakeholders, including its own advisers.
[The somewhat long article is well worth a read. Notable members of NASA as well as former astronauts weigh in on their views of the pros and cons of such an approach as opposed to direct flights to and from the moon. To my eye, NASA was instructed to make the Deep Space Gateway happen so there was a destination for the Space Launch System (SLS) which currently costs something like $2 billion per year in launch and development costs. By comparison, I recall reading that SpaceX anticipates it can develop its next-generation Big 'Falcon' Rocket (BFR) and Big 'Falcon' spaceship (BFS) — now called "Super Heavy" and "Starship", respectively — for about $2 billion total. --martyb]
Related Stories
Gateway Moon station: Canada joins Nasa space project
Canada will contribute US$1.4bn to a proposed Nasa space station that will orbit the Moon and act as a base to land astronauts on its surface.
Prime Minister Justin Trudeau said the step would "push the boundaries of innovation".
The space station, called Gateway, is a key element in Nasa's plan to return to the Moon with humans in the 2020s.
As part of the 24-year commitment, Canada will build a next-generation robotic arm for the new lunar outpost.
"Canada is going to the Moon," Mr Trudeau told a news conference at Canadian Space Agency's headquarters near Montreal, according to AFP.
*Canada is going near the Moon.
Also at CBC and Popular Mechanics.
Previously: Russia Assembles Engineering Group for Lunar Activities and the Deep Space Gateway
China Will Focus on a Lunar Surface Station Rather than a Lunar Orbiting Station
SpaceX's Falcon Heavy Could Launch Japanese and European Payloads to Lunar Orbital Platform-Gateway
Head of Russian Space Agency Roscosmos Wavers on Lunar Orbital Platform-Gateway
Is the Lunar Orbital Platform-Gateway the Right Way to the Moon?
Related: Future of U.S.-Russian Space Cooperation in Doubt
ESA Plans to Send Mining Equipment to the Moon
Lockheed Martin offers architecture for 2024 human lunar landing
Lockheed Martin says it has developed an approach to achieving the goal of landing humans on the south pole of the moon by 2024, but warns that construction of essential hardware would have to start soon to meet that deadline.
In a briefing at the 35th Space Symposium here April 10, company officials said they can make extensive use of existing hardware to develop components like a scaled-down version of the lunar Gateway and a two-stage lunar lander on an accelerated schedule.
While many details have yet to be worked out, the basic elements of the plan, Lockheed argues, demonstrates that the ability to meet the 2024 deadline established March 26 by Vice President Mike Pence in a National Space Council speech is at least technically feasible, if challenging.
[...] Lockheed's plan would diverge from NASA's old approach after Exploration Mission (EM) 1, an uncrewed test of the Orion spacecraft launched by the Space Launch System in 2020. The company proposes launching a "Phase 1" Gateway in 2022 consisting of just the Power and Propulsion Element (PPE) and a small habitation module with docking ports. NASA expects to issue awards for the PPE in May, while the habitation module could be adapted from ongoing studies that are part of NASA's Next Space Technologies for Exploration Partnerships, or NextSTEP, program.
Also at Space.com.
See also: Falcon Heavy's first commercial flight is 'huge' as 'an inflection point' for SpaceX, banker says
Previously: Is the Lunar Orbital Platform-Gateway the Right Way to the Moon?
Canada Will Contribute to the Lunar Orbital Platform-Gateway
Here's Why NASA's Audacious Return to the Moon Just Might Work
(Score: 2) by MostCynical on Friday December 28 2018, @07:31AM (3 children)
"No"
for want of a nail [wikipedia.org], but in reverse.
"I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
(Score: 2) by FatPhil on Saturday December 29 2018, @01:32AM (2 children)
If your solution does not contain setting up camps, for example, one at distance <=X/2 km, then you don't have a solution.
If you can't connect the dots, I apologise for the woooooshing sound, that's the fuel delivery rockets rushing past.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by MostCynical on Saturday December 29 2018, @06:11AM (1 child)
Step one isn't "build a complete refuelling pipeline"
"I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
(Score: 2) by FatPhil on Saturday December 29 2018, @04:22PM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Interesting) by aim on Friday December 28 2018, @07:46AM (7 children)
What is the point of an orbital station above the Moon? What could we learn that would be different from the Mir or ISS stations (other than more lag time and pork for the contractors)?
Getting to Moon orbit from the Moon surface is not very hard (look at the Apollo infrastructure! The gravity well is comparatively tiny.).
I certainly see the point of a Moon base on the surface (it needn't be called Alpha, but...) - as a learning experience, for access to local resources etc. But why insert a Moon orbital station in between?
If you want to fiddle around in space, at least go to an asteroid, learn to turn it into a space station, to move it around.
(Score: 2) by Runaway1956 on Friday December 28 2018, @08:00AM (3 children)
I rather like your idea of using an asteroid. But, I don't think there are a lot of asteroids in orbits convenient to the moon, are there? It may be cost effective to find an asteroid and bring it to lunar orbit, but probably not yet.
(Score: 2) by Immerman on Friday December 28 2018, @05:26PM (2 children)
Unfortunately stable lunar orbits don't really exist - the combination of much stronger gravitational (lunar density) anomalies than on Earth, and the pull of Earth's own gravity, pretty much mean that anything in lunar orbit rapidly escapes without continuous station-keeping, which gets expensive for even a very small mountain.
So long as you target Earth orbit up front though, there's actually a probably very large (though mostly still unidentified) number of near-earth asteroids trapped around in Earths L4 and L5 points, much as the "Greek" and "Trojan" asteroid clouds are trapped around Jupiter's. We've already identified several such asteroids that wander back and forth between our L-points and near-Earth space. It would take a relatively small amount of propulsion to deflect one of those so that it was captured by Earth - especially with the moon right there to provide a handy momentum-sinking gravitational slingshot. Just don't screw up and hit Earth.
(Score: 2) by dry on Saturday December 29 2018, @06:17AM (1 child)
I thought there was something like 3 stable moon orbits. Hmm, Wiki says four, https://en.wikipedia.org/wiki/Frozen_orbit#Lunar_frozen_orbits [wikipedia.org]
(Score: 2) by Immerman on Saturday December 29 2018, @03:52PM
I suspect those are only stable compared to the alternatives - e.g. the Apollo 13 sub-satellite they mention as *almost* aligned with an optimal path lasted less than two years before electronics failure, and was believed to have crashed into the surface some time later. If you're talking about a mountain instead of a little metal box, you really want an orbit that will be stable for the long term, as corrections will be expensive. Then again it only mentions low orbits - so perhaps I misunderstood, and many stable high orbits exist.
You also can't use a lunar slingshot to rob an incoming asteroid of much of its momentum if you're targeting lunar orbit - you pretty much need a gravity well already orbiting within your target gravity well to be able to pull that off. Without that you have to rely on rockets to neutralize the immense acceleration it gets from entering Earth space, though you could probably at least use the moon to get it into a high Earth orbit, and only use rockets for the lunar capture.
(Score: 1, Insightful) by Anonymous Coward on Friday December 28 2018, @11:23AM (1 child)
The point is that the SLS, NASA's "rocket to nowhere," has no other mission. Much like the ISS was created so the Space Shuttle would have a place to go, and the Space Shuttle was kept in service so it could service the ISS, NASA needs a destination that the SLS, and only the SLS, can reach. The fact that there is exactly no reason to have a station in lunar orbit is irrelevant.
(Score: 2) by takyon on Friday December 28 2018, @01:22PM
It's worse. Not only could SpaceX's upcoming BFR/Starship reach LOP-G, but it could be constructed using Falcon Heavy:
NASA's Chief of Human Spaceflight Rules Out Use of Falcon Heavy for Lunar Station [soylentnews.org]
SpaceX's Falcon Heavy Could Launch Japanese and European Payloads to Lunar Orbital Platform-Gateway [soylentnews.org]
The modules for LOP-G are about 8-10 ton payloads when I last checked. Nothing an unmanned Falcon Heavy can't deliver.
The cost of an SLS launch is sometimes pegged as low as $500 million, but the real cost is about $3 billion, and could end up being more (or a divide by zero error) if the program is cancelled. Fully expendable Falcon Heavy is about $150 million.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by Immerman on Friday December 28 2018, @05:11PM
A lunar-orbit fuel depot would make sense AFTER we're producing and using enough lunar-made fuel to justify more than transferring fuel directly from a lunar-to-orbit tanker vehicle. And there's not necessarily any reason for it to be manned.
The only advantage I can see of an manned orbital lunar station (at least without already having a thriving moonbase) is to build a space station outside the Earth's magnetosphere. Can we handle the full force of the solar wind on a regular basis?
But that hardly seems worth the effort given the current costs. Especially since the answer would seem to be trivially "Yes, but we need more radiation shielding".
A lunar base though - *that* has potential. It is essentially a giant asteroid with the benefit/penalty of a useful amount of gravity. Excellent source for radiation shielding (aka rock) for orbital habitats, if nothing else. Potentially a decent source of rocket fuel, water, etc. as well, as well as He3 for fusion once that nut is cracked.
Not quite the concentrated ore source of a rich metallic, organic, or icy asteroid, but still a great place to start developing vacuum-industrial practices that would be mostly applicable to asteroid mining, without having to simultaneously wrestle with the difficulties of micro-gravity.
The moon is also an excellent place for research into how well life can handle non-Earth gravity. Right now we know that several plants and animals that do fine on Earth have real survival and reproductive problems in space. But we only have two data points: Earth, and the heavily irradiated micro-gravity environment of the ISS. A third data point at 1/6th gravity with excellent radiation shielding would go a long way towards telling us if space colonization will be as promising as portrayed in science fiction, or if Earth life depends on a narrow range of gravity to thrive. Heck, if life has trouble on the moon, we can build a long-term experimental centrifuge there to help narrow down exactly how wide the gravitational "sweet spot" is - something we can't do on Earth, nor easily in orbit.
A manned lunar orbital base doesn't seem to make a whole lot of sense unless/until we're in the situation of wanting to transfer cargo between dedicated lunar landers and trans-Earth orbital vehicles. If for example Starship could get to the orbital base and back without refueling, but would need to refuel to land on the surface, it *might* make more sense to transfer cargo to a moon-optimized lander rather than just refueling at the orbital station. But that seems unlikely, at least until such time as we build a lunar space elevator through the Earth-moon L1 point.
(Score: 3, Insightful) by Runaway1956 on Friday December 28 2018, @07:57AM (9 children)
But, they may not be taking the best approach to it.
It makes sense to have an orbital base of operations. It can fill many roles, starting with communications, rescue missions, detailed mapping, fuel station, command platform, repair facility, research facility - and more. But, the manner in which they are approaching this thing seems kinda wasteful. NASA should probably forget about building the gateway, and let the competitors do it. Musk, among others, has already demonstrated that he can perform these kind of tasks at far lower prices than NASA.
Ideally, the various space agencies and companies around the world would collaborate on this gateway, write standards for everyone to follow, and make the gateway big enough to fill all the roles that it might be called on to perform. Following this route, they could probably build a mega-station for less than NASA can build a tiny, cramped POS that no one wants to spend any time on.
(Score: 1, Informative) by Anonymous Coward on Friday December 28 2018, @11:47AM (8 children)
Communications: You can send radio transmission from Earth to the Moon without a station. If you want a relay to the far side of the Moon, the proposed station is in the wrong place (and doesn't need to be manned).
Rescue: Astronauts are more likely to need to be rescued from the gateway than to rescue anyone using it. Remember when the Soyuz rocket failed in October and they almost had to abandon the ISS? Meanwhile, Moon flights traveling from Earth don't need rescue even if they have a problem, because the trajectory takes them right back to Earth (remember Apollo 13). Stopping at the gateway just creates more opportunities for things to go wrong.
Mapping: We already have pretty good maps. Need better? Send a robot. They're doing a great job on Mars.
Fuel station: Stopping at the gateway uses more fuel, not less, compared to going directly from Earth.
Command Platform: Mission Control is in Houston.
Repair facility: Repair of what? The ISS needs to be repaired regularly, but nothing has ever been repaired there. And there's a lot more stuff orbiting Earth that might benefit from being repaired. Even during the post-Columbia period, where the ISS was available to service a damaged shuttle, the only intention was to provide a place for the shuttle to wait for rescue. Actually doing repairs was never seriously considered - even though the shuttles were far more valuable than any conceived lunar vehicle.
Research: There's nothing to research in lunar orbit. Any samples collected from the Moon need to be sent back to Earth. The only thing that needs a research station in space is medical data on living in low gravity. You can do that on the ISS. Or you could have, if NASA had bothered to launch the ISS module they built for that instead of leaving it outside to rust.
Musk wouldn't waste his time with such a useless concept. The Starship will probably be taking tourists around the Moon before the SLS has even launched, and landing there (if there's any reason to) long before this has had a chance to be canceled.
(Score: 1, Insightful) by Anonymous Coward on Friday December 28 2018, @12:10PM (7 children)
You're thinking short term, not to mention small scale.
communications: the proposed station need not be in the currently planned orbit
rescue: several missions going at once on the moon, and one of them gets in trouble, the gateway could be in the best position to assist
mapping: we have pretty good maps of the earth already, but Google Earth and others continue to scan
fuel station: it all depends on the mission, the equipment, etc. Any mission to the moon has to insert itself into some kind of orbit around the moon anyway - why not choose a common orbit, where excess fuel can be stored, for possible future use on a mission that runs short? Stockpiling fuel can never hurt, and you'll be really glad you did if you ever spring a leak!
repair facility: you're still thinking short term.
research: a central facility with several research instruments shared among several agencies, countries, companies wouldn't be a better use, than each of those agencies shipping duplicate instruments to the surface of the moon? Or, you're suggesting that we've done all possible research, and we can't possibly learn anything new while in orbit around the moon (or the earth, for that matter)?
Again, I'll say a central, shared resource facility in orbit around the moon can benefit everyone.
But, allowing NASA to blow billions on the project isn't the best way to achieve any of the goals I've pointed out.
(Score: 2) by takyon on Friday December 28 2018, @01:13PM (4 children)
LOP-G will never be used as a fuel depot.
The only thing LOP-G would be good for in my opinion? It could be used to allow humans to assemble and service a giant space telescope. And that could be done more easily at the ISS.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by HiThere on Friday December 28 2018, @05:29PM (3 children)
Sorry, but ISS is the wrong place to build a space telescope. Orbiting the moon has some advantages, particularly if the orbit puts it over the far side of the moon part of the time. That could screen out a lot of the radio noise.
I really think the far side of the moon is generally a better location, but an orbital position gives you more flexibility over just where you point the thing. Of course, the best position would require a pair of observatories...at opposite ends of Neptune's orbit. But that's not going to happen anytime soon. Still, it would give you a great parallax for most of the sky. (All the sky would require a third observatory well out of the plane of the solar system.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 3, Interesting) by takyon on Friday December 28 2018, @07:22PM (2 children)
You can send bigger payloads to ISS since it takes less energy to reach that orbit.
Lunar orbit is not where you want a radio telescope. You want a much larger radio telescope on the lunar surface on the far side. Another acceptable ground telescope would be a zenith telescope [nasa.gov].
The ISS is a great place to put a telescope. You could have it onboard, nearby, tethered or untethered. Or you could just use the ISS as the construction site. With spacewalks, you can assemble a much larger telescope than would be possible to fit into a rocket's payload fairing, and without the risk of rocket vibrations breaking the telescope. Then you can use the telescope's on-board propellant or ion engines to move it away from the ISS if you wish.
Ideally, we could assemble modular telescopes in orbit using remote control. But as long as we insist on sending humans to an orbiting space station, we should have them assemble or repair gigantic space telescopes. It's more important than anything else they would be doing there.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by fyngyrz on Saturday December 29 2018, @01:44AM (1 child)
It really isn't. From time to time, the ISS is forced to maneuver abruptly to avoid orbital space debris. A telescope nearby would have to do the same, which would interfere with long exposures and consume maneuvering fuel at a higher rate than one would really want (because ion thrusters would be too weak to impart the required delta-v, so solar power won't cut it.)
Another issue is that the ISS's earth orbit is pretty fast, so not a very stable observational point. That means (at a minimum) relatively high-rate gyroscopic correction. An ideal space telescope would be able to remain in a relatively fixed location for long exposures, expending as little energy as possible to track whatever it is looking at.
--
If ignorance is bliss, why aren't more people happy?
(Score: 2) by takyon on Saturday December 29 2018, @02:26AM
Like I said, they can move the telescope somewhere else after it is built there.
But the ability to easily service a telescope (since humans are right there) is incredibly valuable. There has never been an attempt to robotically service a telescope, and there might not be for years to come since it is still considered to be cheaper to just launch a brand new telescope.
Hubble got a lot of lifespan and improvements out of its servicing missions. Not to mention the crucial early fix of its incorrect optics.
As for keeping a telescope at ISS, you trade an ideal orbit for lower costs, more payload mass, and easy assembly and ongoing repair and servicing. Humans are committed to the ISS until 2028. If there was a large telescope there, that's 10 years of time in which it could be serviced or even enlarged. You wouldn't need the Space Shuttle or anything special to service the telescope, just the Soyuz, or soon Falcon 9 Crew Dragon 2 or CST-100 Starliner, in order to get astronauts to the station.
If the orbit isn't ideal, you will still have a sizable fraction of the universe that you can observe. You could also detach a telescope when the ISS is at peak altitude and rejoin it later (both will descend at different rates, and the ISS has flexibility in when it can be reboosted). The ISS orbit has peaked around 435 km. Hubble orbits at around 540 km and its orbit will eventually decay down to where ISS has been, unless it is boosted by something like Dream Chaser [wikipedia.org]. Either way, a space telescope operating at a lower orbit would observe a target in its field of view and potentially spend multiple orbits viewing the target each time. Even if it is not as optimal as a higher orbit would be, the lower costs could be a bigger factor. Send two, three, or twenty space telescopes to the ISS or other space station if you want.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 4, Insightful) by Immerman on Friday December 28 2018, @06:21PM
Well, we'd be mostly building and paying for it short-term, with technology that will be mostly obsolete in the long term, so it seems reasonable to ask what the short-term benefits are. Once the moon becomes a thriving resource source *then* an orbital space station probably makes sense.
There's also no need to stop in orbit to land on the moon, that just provides a convenient last-minute abort opportunity for landers that are either not reliable enough to neglect it, or which have an orbital propulsion module that can't land - as was the case for the manned lunar landers so far. As with Mars, there are considerably more efficient trajectories that go directly from Earth orbit to the lunar surface.
And, once the moon is a thriving resource source, then the cost of building a lunar space station will drop considerably. So, what's the point of building a lunar-orbit space station today?
As for rescue - the only way that an orbital space station would be in a position to assist is if they have a rocket on standby - a rocket that could just as easily be on standby at one (or more) of the lunar bases - in which case they can help each other out with only a slightly longer delay.
Research - what exactly are you going to be researching in Lunar orbit, that you couldn't research just as well in Earth orbit? The only difference is the lack of magnetosphere and correspondingly higher radiation levels. Orbital study of the moon itself can be better done by satellites - as witnessed by the massive amount of Earth research done by satellites instead of the ISS.
Also consider that the SpaceX Starship is likely to be in regular operation long before the LOP-G gets off the drawing board. And that means provide more pressurized volume than the ISS, easily deliverable to either Lunar orbit, *or* the lunar surface in short order. If SpaceX makes them available for long-term lease/purchase then they will make for a far cheaper and more reliable basis for early lunar surface and orbital space stations than anything else available - with the added benefit of full-station emergency abort
The only reason I can think of for a lunar "gateway" early on is emergency medical and resupply services available to multiple surface bases. However, I'm dubious as to how many medical conditions are severe enough to not be more cost-effectively handled in place, time-critical enough to not be able to afford another few hours of transit to a "primary" lunar base, and tidy enough to be able to handle in free-fall. That last one probably rules out most surgeries or anything else that involves a lot of fluids.
(Score: 2) by c0lo on Friday December 28 2018, @11:13PM
Excuse me, but on long term, nothing less than Deep Space 9 makes sense. Not even Babylon 5.
(grin)
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by isostatic on Friday December 28 2018, @11:56AM
NASA will return humans to the surface of the moon.
No it won't.
(Score: 3, Interesting) by JoeMerchant on Friday December 28 2018, @12:21PM (10 children)
When I was 2 years old, Neil Armstrong took one small step.
When I was 5 years old, Eugene Cernan became the last man to walk on the moon.
The last 46 years feel like paralysis by analysis. Fund a mission, choose a course and follow it, figure out the "best way" by doing something sub-optimal that gives real data to make future decisions on.
If we can afford $5B for a wall, we can afford a sub-optimal lunar program.
🌻🌻 [google.com]
(Score: 3, Interesting) by Immerman on Friday December 28 2018, @07:39PM (9 children)
Quite.
And in a relatively few years SpaceX Starship will likely be a game-changing well-tested, reliable, and cheap vehicle capable of landing on the Moon's surface and returning, while providing more pressurized volume than the ISS - an excellent basis for short-term mission-specific lunar outposts, as well as massive cargo deliveries from Earth for the construction of more permanent lunar facilities.
Seems to me that that should be the foundation of a near-optimal lunar supply line and initial build-out. Funding for space development is so hard to come by, and a lunar base likely to be so expensive, that not incorporating such a massive strategic advantage into the plan seems like a good way to ensure we continue to accomplish nothing much.
As does wasting precious resources recreating the ISS around the moon. If we're going to the moon, let's do it properly and go all the way. Want to scout the surface in person first? Fine, spend a month or three hopping a Starship with an exploration team and equipment around the surface, with possible orbital refueling trips, then back to Earth for refurbishing, leaving a large cache of supplies and equipment behind for future teams. Do that a few times, guided by in-depth orbital maps of promising resources, and we'll have gotten a good idea of the challenges of operating on the Lunar surface for extended periods, as well as having almost certainly identified at least one site that would make an excellent location for a more permanent outpost, and leaving behind a bounty of equipment and supplies accessible by a quick sub-orbital hop to get them started.
(Score: 2) by JoeMerchant on Saturday December 29 2018, @03:19PM (8 children)
The elephant outside the ionosphere (as opposed to in the room) is radiation.
Those 3 years of lunar missions got lucky by not having a crew cooked alive by a solar flare. Worse still, they likely wouldn't have died before getting home, but instead presented on the ground like Nagasaki bombing victims with horrible symptoms for a short time before they finally died.
The last 46 years of tech development means that the bulk of lunar development work can be carried on robotically, and should be so that human crews can dash across the danger zone to well shielded bunkers on the other side.
"Moon" presently streaming on Netflix
I'm still not sure what we could possibly do to ensure a safe journey to Mars, and I'm surprised there's not a public discussion of the probability of missing/surviving solar flare exposure on a typical trip there. I wouldn't be surprised if the first attempted manned trips to Mars do coincide with the predicted solar minimums, nor would I be surprised if they don't make a big deal about that timing in the discussion of why it's a good time to go.
🌻🌻 [google.com]
(Score: 2) by Immerman on Sunday December 30 2018, @05:21PM (7 children)
Quite - though I'd say the magnetosphere rather than ionosphere, though I suppose the ISS lies well within the ionosphere as well.
And yeah, the radiation is one of the big reasons I think it makes a lot more sense to aim straight for the moon's surface - land in a small steep-walled valley or crater and the geology (lunology?) could easily and immediately shield you from a good 75% or more of incoming solar and cosmic radiation, as well as similarly reducing your chances of getting hit by a solar flare. If we can find some conveniently located exposed lava tubes to use as an emergency bunker when needed that would make things even easier.
I'm not sure how big a problem solar flares would actually be for a Mars mission - they're nasty, but the radiation is pretty much all coming from a single direction - point the free-coasting rocket directly away from the sun whenever solar flares are threatening and you'd have the rocket, engines, and all the braking and landing fuel (and the tanks) as shielding. Plus all your supplies, etc stored on the lower levels - my understanding is that both EM and charged particle radiation is rather devastating to living tissue, but generally doesn't cause long-term lingering radioactivity that would contaminate rations and the like. You probably only need a relatively small amount of additional shielding, if any, to bring things down to a safe level - add a bit of a bunker safely sheltered within your water reserves and you'd probably be good to go. Maybe you have to cram in like sardines for a few hours, but that's a small price to pay, and the rest of the time the room would offer the only real privacy available during the journey. Other than spacewalks, which they obviously need to have available at all times because why not? It'd still be a once-in-a-lifetime opportunity (maybe twice, if you ended up returning to Earth)
Obviously, I'd want to see some math on that before I signed up - and ideally a rocket loaded with test animals being exposed to a solar flare for confirmation. Don't see any point in intentionally subjecting people to such a thing by putting them in a long-term station in lunar orbit though.
(Score: 2) by JoeMerchant on Monday December 31 2018, @03:06AM (6 children)
Check on the magnetosphere, though I think the protection doesn't get good until you're pretty deep inside it.
IIRC, they have discovered some probable big-ass lava tubes that are also candidates for significant water-ice deposits. Now, if it's my show to run, I'd demand that the lunar water deposits be used in sustainable fashion, meaning: if there are an estimated X mega-tons of water in a given area, use it by all means, but that estimate had better increase over long time scales and not ever decrease at a rate that could result in total depletion within the next 500 years...
Particle physicists have a fairly good handle on a lot of what goes on between the various charged, uncharged, etc. high energy particles, and they _think_ they have a good idea of what goes on outside the Earth's magnetosphere, but the data is based on a very tiny collection of observations. Think about being deposited in 1000 random locations on Earth and getting to observe what's visible just from the place you appear... after observing 100 locations for 10 years, I don't think you're really prepared to deal with the next 100 locations you'll be placed in - maybe 90 of them, but 10 are going to be some kind of surprise. And, even with 1000 drops onto Earth, what are the odds that one of your observations will tell you about active volcanoes, or strong earthquakes, or extreme lightning or hail or tornadoes, tsunami, mudslide, elephants, copperhead snakes, drop bears, etc.? We think we can see what goes on in space, but compared to the surface of the Earth, space is BIG.
🌻🌻 [google.com]
(Score: 2) by Immerman on Wednesday January 02 2019, @01:26AM (5 children)
Sounds like the magnetopause distance varies between about 3 and 15 Earth-radii, while the moon is ~60 Earth-radii away. Something interesting may happen around every full moon tough, as it travels through the Earth's wake.
I've long been a fan of lava tube construction - particularly if we can find some nice long ones (or better yet, a network) that allow for lots of underground expansion without tunneling. Just keep building a nice big airlock in the back wall of each new expansion and grow as resources allow. Also handy for less ambitious early projects - as long as it's stable enough for the equipment vibrations, just assemble your habitats freestanding within it and don't worry about radiation. You could potentially have whole cities in a truly large lunar tube, with experimental greenhouses and perhaps recreational spaces extending out onto the surface as acceptable radiation risks were established.
I wonder how hard it would be to make a reliably air-and-pressure-tight version of those inflatable concrete-impregnated "tents"?
Early on, depending on the particular tunnel and landscape, you could actually have a fair sized community all having a nice wide view of the surface, just not of the sky. Just be sure to have that cosmic-ray shadow-line clearly marked, and be mindful of how much time you spend outside it.
(Score: 2) by JoeMerchant on Wednesday January 02 2019, @03:15AM (4 children)
I'm guessing that, even if the lava tubes are structurally sound enough to hold air pressure better than 10psi, they probably leak, a lot, and will need some kind of skin sprayed onto their interior if they are to hold a breathable atmosphere.
I'm also guessing that there's a more or less standard maximum size of lava tube due to the physical properties of the lava, though in Lunar gravity that size might be quite large. The tubes formed on the big island of Hawaii when hot lava was running through a cooled shell, then the supply stopped and it just ran out the bottom, so they tend to be sloped floors most of the time.
Definitely easier to use a natural pre-bored tunnel than to dig your own structure. Wonder how long before we run into vacuum tube inhabiting aliens - it's gotta be a common formation throughout the universe, and is quite the natural radiation barrier.
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(Score: 2) by Immerman on Wednesday January 02 2019, @08:07PM (3 children)
They probably do leak on their own, but that's fine.
Early on you probably wouldn't incorporate the tube itself in your structure - especially if it's a big one. That just complicates the construction process, and your crew needs someplace to sleep while they develop vacuum-friendly construction practices. Plus, while lava tubes typically top out at around 50 feet or so wide on Earth, various analysis put the lunar limit at between 1,600ft and several miles before gravitational instability causes them to collapse, and the near absence of moon-quakes and other weathering should help them approach that. A couple hundred feet for a nice solid one is probably not unreasonable, and even 50' would be quite usable. A large tube could potentially swallow entire cities without scraping the edges.
For the early outpost, just drive into the mouth of a modest-sized tunnel and erect your free-standing, pressurized but un-shielded habitats there - heck, sturdy inflated "tents" could get the job done (though I'd want at least a double wall to forestall catastrophic leaks) - except for the floor they're already essentially in a giant insulated vacuum thermos. Sloping cave floors do seem likely, but you're going to want your habitats on a raised or well-insulated platform anyway, to avoid conductive heat loss into the perpetually sub-freezing rock, and leveling the surface of such a platform level is trivial. (Strong vacuum-curing foamed insulation poured into a "sandbag dam" form seems like a quick and easy way to do it). Early expansion is similarly easy, just be sure to leave a wide enough path for additional habitats to be transported further into the tunnel.
When you're ready for a more permanent, less pre-fab habitat, start building a more permanent structure further down the tunnel, making sure to leave lots of unpressurized space near the currently occupied mouth of the tunnel as "garage space" for anything in the future that needs unrestricted access to the surface
For longer-term (and larger scale) construction, incorporating the existing tube walls is almost certainly the way to go. I'd imagine you'd probably want a multi-layered coating - at least a thick layer of insulation to smooth the surfaces, retain heat, and provide level "stepped" floors, followed by with an air-tight surface to reduce leakage, all covered by a layer of reinforced moon-crete to provide bulk pressure containment and protection for the air boundary skin (plus some insulated thermal mass for comfort). Concrete typically needs to breathe atmospheric CO2 for several years to finish curing, but the rate of airflow through it is generally very low, so that might be enough. A coat of non/low-breathing paint would probably go a long way to further reducing leakage.
You also don't need 15 psi, or even 10. 7psi (~1/2 atmosphere) is easily adjusted to by most people, especially if it's more oxygen-rich so that the oxygen partial pressure is still close to an Earth-normal 3psi. And it's mostly the partial pressure that determines the fire hazard, not the amount of other inert gasses, so not much worry there.
(Score: 2) by JoeMerchant on Wednesday January 02 2019, @08:23PM
That sounds like an opportunity for your outer layers to outgas CO2 into the concrete from the other side...
All of this is great, just need to divert the funding from an Aircraft carrier group or two and git'er done.
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(Score: 2) by JoeMerchant on Wednesday January 02 2019, @08:30PM (1 child)
As for 10psi, if I'm reading the charts correctly, that's the pressure at 10,000 feet, and at 10,000+ feet I'm not happy at all doing strenuous activities like snowboarding. Sure, you can increase the oxygen fraction, but I believe that's also increasing the overall flammability. Of course, people can adapt to a lot and you can make 3psi work, though I'd be worried about the boiling point of water getting too close to body temperature...
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(Score: 2) by Immerman on Thursday January 03 2019, @02:03AM
As you say, that's not the lack of pressure that's bothering you, it's the lack of oxygen.
That's where the oxygen partial pressure comes in - it's the pressure the oxygen in the room would be at if you magically removed all the other gasses in the room. Basically it's the total pressure multiplied by the percentage of molecules that are oxygen. So long as that number doesn't change, neither does the amount of oxygen in a breath of air.
Flammability is also tied very closely to partial pressure (all reactivity is, really). Pressure is basically a measure of how many molecules are hitting a surface per second (and how fast, which depends only on temperature). So long as the number of oxygen molecules hitting a surface in a second is constant, so is the number of potential chemical reactions that could contribute more heat to the flame. Inert gasses would alter the thermo-fluid dynamics of the flames themselves to some extent, but I *think* the effect on fire hazards would be relatively minor.
Regardless though, if you want a full 1atm of pressure, it's not *that* much more difficult - you only have to double the tensile strength of your walls.
As for the boiling point of water, no worries. Body temperature is ~40C, if we call 60C a nice wide safety margin, then we can drop the pressure to about 3 psi - or pure oxygen at Earth-normal partial pressure.