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Notes -
Contra sapce colonization
A couple arguments against space colonization, in order of how convincing they are to me. A lot of arguments in favor of space colonization like to make specious arguments based on the proposed similarity between the colonization of the Americas and Mars/Venus/Moons of Jupiter. While potentially highlighting psychologically similar explorer mindsets, I think these arguments completely miss the physical realities of space.
1. Ecology and Biology
The newest Tom Murphy post from DoTheMath has clarified what I believe to be a huge blindspot in the space colonization narrative that many on this forum: Ecology! Murphy's argument is that we've never successfully created a sealed, self-sustaining ecology that lasts for even anything close to a human lifespan. Biosphere 2 lasted for approximately 16 months, and the EcoSphere that Murphy uses as an example in this article lasts for about 10 years, but ultimately collapses because the shrimp fail to reproduce. Both of these "sealed" examples occur on Earth, shielded from radiation, and in moderate ambient temperatures. This will not be the case on Mars, nor on the 9 month journey to the Red Planet.
Even outside of sealed environments, island ecologies on Earth are notoriously unstable because of population bottlenecks that eliminate genetic diversity and make key species vulnerable to freak viruses or environmental disruption.
Of course a Mars colony won't be an ecological island, at least at first, because of constant shipments from Earth of supplies and genetic material (humans, bacteria, crops, etc.). But unless the colony can eventually become self-sustaining, I'm not sure what the point of "colonization" actually is. It's not clear that mammals can even reproduce in low gravity environments, and barring a large scale terraforming effort that would likely take millennia, any Mars colony will be a extraterrestrial version of Biosphere 2 without the built in radiation shielding and pleasant ambient temperature.
Constant immigration and resupply missions will also be incredibly challenging. 9 months in radiation-rich deep space in cramped, near solitary confinement is not something that is necessarily possible to endure for many humans. Every simulated Mars mission has ended with the participants at each others throats before arrival to the planet. Astronauts on the ISS, who receive relatively small doses of radiation compared to deep space, experience cancers at much higher rates, and probably damage their reproductive genetics significantly.
Contrast this to the colonization of the Americas. The initial colonists of both Massachusetts and Virginia were terribly unprepared for what was, at least compared to space, a relatively benign ecological context. There was clean air, water, shielding from radiation, and relatively plentiful food. Yet these colonies nearly died out in their first winter because of poor planning, and were only saved by the help of Native Americans. There are not Native Americans on Mars, no deer or wild berries to hunt in the woods if farming fails, or a supply ship is missed. Mars colonists won't be rugged frontiersmen, but extremely fragile dependents of techno-industrial society.
I'm not saying it's impossible to overcome these challenges, but it does seem irresponsible to waste trillions of dollars and thousands of lives on something we are pretty sure won't work.
2. Motivation
The primary initial motivation for New World colonization was $$$. The voyages of discovery were looking for trade routes to India to undercut the Muslim stranglehold on the spice trade. Initial Spanish colonization was focused on exploiting the mineral wealth of Mexico and Peru, French colonization on the fur trade, and English colonization on cash crops like tobacco.
In space, there is almost 0 monetary incentive for colonization. Satellites and telecommunications operate fine without any human astronauts, and even asteroid mining, which is a dubious economic proposition in the first place, doesn't really benefit from humans being in space. Everything kind of resource extraction that we might want to do in space is just better accomplished by robots for orders of magnitude less money.
What about Lebensraum? If that's really the issue, why don't we see the development of seasteds or self-sufficient cities in otherwise inhospitable regions of earth (the top of Everest for example).
3. Cost
Keeping an astronaut on the ISS costs about $1M/astronaut per day. And this is a space station that is relatively close to earth. Of course low earth orbit (LEO) where the ISS is, is halfway to most places in the inner solar system in terms of Delta V, so we're probably not talking about more than $10M/day per person for a Mars mission. For a colony on Mars with 100 people, that's close to a billion dollars a day. There is no national government, or corporation on earth that could support that.
Even if technology development by industry leaders such as SpaceX lowers launch costs by 1,000x, which I find to be an absurd proposition, that's still $1 million/day with no return on investment.
Even though SpaceX has improved the economics of launching to LEO and other near Earth orbits, our space capabilities seem to be degrading in most other areas. The promised Artemis moon missions are continually delayed by frankly embarrassing engineering oversights, and companies like Boeing, Lockheed Martin, and Northrup Grumman that were essential in the first space race can't seem to produce components without running over cost and under quality.
4. Narrative
This one is a little bit more speculative. The West, and much of the West of the world is entering a demographic spiral, with birth rates falling ever lower below replacement. This relieves a lot of the "population pressure" to colonize space, but also indicates a collapse in the narrative of progress that underpins the whole rationale that would lead us to even want to do such an absurd thing. If our leadership and population doesn't want to build the physical infrastructure and human capital necessary to embark on this kind of megaproject, doesn't this suggest that this dream is no longer appealing to the collective psyche? My read on the ground is that the general population is sick of the narrative of progress: we were promised flying cars and backyard nuclear power plants, but we instead got new financial instruments, addictive technology, and insurance.
China of course is held up as a positive example where the dream of the "engineering state" is kept alive, but I think this is misleading. China has potentially even worse of a demographic crisis than we do, and most of its smartest people (at least those I see in American academia) are desperate to leave.
Without a compelling narrative, the challenges facing potential space colonization become even more stark and difficult to overcome.
I think the idea of biological humans colonizing Mars is silly. It's very likely easier to make a strong AI than colonize Mars, certainly more profitable. Send robots and develop Mars. Or move inwards, there is lots of solar power closer to the Sun.
Likewise I've always been suspicious of chemical rockets. If it's not nuclear, why bother leaving Earth's gravity well? Chemical rockets are just too wimpy for serious space travel. Develop fusion first, then move out.
Chemical rockets do a lot better in the worst case scenario for a rocket launch.
I agree that they’re too weak for the real extrasolar timelines.
If there was a bunch of fissile material sitting around in the asteroid belt, maybe that would be a good reason to get up there. Unfortunately, a cursory search tells me that it only got concentrated on Earth by some sort of geological distillation. Probably not available outside of gravity wells.
I don't see why we should be worried about a little fallout in the atmosphere, we detonated thousands of H-bombs and there were no significant radiological consequences. Millions of people die every year from air pollution already.
Wait for fusion IMO.
The risk isn't from a nuclear explosion, it's from an explosion that scatters nuclear material which is way more likely in a rocket than a bomb.
Er, yes, that's what "fallout" means. You missed @RandomRanger's point. One rocket's worth of nuclear material in the atmosphere is barely a blip. Note that even a normal rocket is chock-full of toxic chemicals, which is why we don't launch near population centers. Most normies tend to be off by many orders of magnitude when they intuit how dangerous "nucular" things are.
I'm not convinced. One NERVA style nuclear thermal rocket engine contains hundreds of kilos of uranium. Put one as an upper stage engine on a SpaceX booster and you can lift another 100 tons of cargo to orbit - which quite frequently will be 100 tons of U-235 (or 233, since we'd probably quickly get into thorium breeding if we'd consider such a project). We want to fuel an economy the size of a solar system, after all, and earth is the only place in this economy where it would be economical to mine Uranium.
Compare this to the ~4 kg of an H-bomb primer, and vaporizing a nuke fuel truck sounds a whole lot more catastrophic that an atmospheric test.
The interesting part is the "vaporizing" here. I'm pretty sure that most failure modes of such a launch would not vaporize a significant fraction of the payload or even the engine cores. The "fallout" would quite literally be tens of thousands of 1-kg pits (and a few fuel pellets) raining down from the explosion. Compared with the alternative, that contaminates a much smaller area. Manual clean-up would be possible, economical and necessary from a proliferation (and ecological, of course) perspective.
Hmm, I think you're talking about two different things. One is the launch, from Earth, of a nuclear-powered rocket (e.g. NERVA). Even if it contains hundreds of kilos of uranium, it's a lot fairer to compare that to an A-bomb like Little Boy (64kg) rather than just the primer of an H-bomb. And, like you said, in an accident a lot less of it is going to vaporize than it would in a proper nuclear bomb.
But I wasn't talking about the payload at all. I guess you're thinking that you'd want to lift 100 tons of U-235 to orbit for space-based nuclear rockets? I agree that's a different kind of risk. And I'm not even sure how valuable nuclear rockets would be for long space trips (there are lots of options once you're up there).
"Current" designs (well, currently available 1960's designs) of nuclear powered rockets aren't useful for launching from the surface. While they have by far the best efficiency/specific impulse of all engines available today, they have catastrophically terrible thrust to weight ratios. Absolutely useless engines for first stage and even most second stage applications. You'd only want to use them in space - then their low thrust doesn't matter, and they use their high fuel efficiency to cut down time of a Mars transfer by a factor of
3.The vast majority of atmospheric tests where tactical warheads with a boosted fission core. Those - just like H-bomb primers - always contain subcritical amounts of plutonium (4kg) for efficiency and safety (they can only fission if explosively collapsed correctly into a critical mass) reasons. Pretty much the only devices with larger amounts of fissile material are H-bombs with second stages and tampers. But even those are much, much lighter than Little Boy, and they weren't tested all that much.
Extremely valuable! Even the most primitive and conservative designs outperform chemical rockets by several hundred percent (again, in specific impulse). More batshit designs (nuclear pulse propulsion and nuclear salt water rockets) are probably technically doable today, and offer orders of magnitude more specific impulse. Those would actually unlock the outer planets and the asteroid belt, and maybe Alpha Centauri.
Sustained fusion is already difficult enough in containment, actual fusion propulsion is probably orders of magnitude more complex than that. I have no hopes to still be alive when it arrives.
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