this post was submitted on 27 Oct 2024
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What a dumbass. If we send people in the quickest possible way (or any way at all, really) and they all die in the attempt, that will set the whole project back decades.
The answer to the radiation problem is better shielding, not a fundamentally unsafe mission.
btw it is not the nuclear propulsion that I'm calling unsafe. It is the idea that we could do without redundancy. That's just a monumentally stupid idea.
Since the astronauts need water to survive, why not line the spaceship with reservoirs of it to provide the shielding? Or does water not block space radiation well enough?
They did that in the novel "Seveneves", used a massive chunk of ice as the bow of their ship on a one-way, twenty year plus trip. It didn't stop all the radiation, though. Just enough to keep a minimum number of crew alive to complete their mission. They all developed different types of cancers, anyways,but the kinds that could be treated along the way and extend their chances.
But then they’re drinking irradiated water, no?
Unless it’s really easy to remove the radiation safely, this doesn’t seem like the right solution.
Irradiated water is fine.
You're thinking of radioactive water, which is water with radioactive stuff in it.
Subjecting regular water to regular amounts of radiation is fine, even if it's high-energy gamma rays. If there's enough radiation to make water itself radioactive then you have bigger problems than radioactive water.
Ah yes, that’s the difference. Thanks!
You wouldn't want to drink reactor coolant water (mostly because of the chemistry additives) but water in a tank that just stays between the people and the hot stuff would mostly just get warm.
Most of what you'd get at that kind of distance is neutrons, and they are more likely to bounce off the hydrogen than to do something like activate the oxygen into N16 which dies off pretty fast anyway.
"remove" what exactly? water is not alive so it's okay to irradiate it https://en.wikipedia.org/wiki/Food_irradiation
Dude...wut.
Can't tell if you're joking or not.
i don't get what you fail to understand, water doesn't became radioactive or harmful in any other way after irradiation, and irradiation of food is routinely used for extending its shelf life
The basis for what you're saying is that water is some kind of magic shield that reflects radiation, which is not a thing.
At best, if you're talking about lining the hull of a spacecraft and expecting that to work, that's not a thing either because if the water is taking on any extra mass of any kind, it would obviously expand. Water in its purest form would have to take on mass to "absorb" radiation, expanding a hull and destroying it over time. If you left room in there for expansion, you'd die on exit or reentry of atmosphere without freezing it.
The only way you can reflect radiation without absorbing something is by denying it entry. Water doesn't do that.
water does not expand upon irradiation, what the fuck are you talking about. you can't reflect high energy protons (what would be important in radiation in interplanetary travel) you can only either absorb them or let them pass, there's no third option, same for anything above uv and electrons
to a first approximation (rather good one at that) (for gammas) absorption is proportional to how much mass per area unit is used as a barrier. 1 g/cm^2 of water is just as good barrier as 1 g/cm^2 of lead or steel. this means that you can absolutely use completely normal, regular potable water as a radiation shield
i'm not even sure what it's supposed to mean, unless your understanding of ionizing radiation is uncut nonsense
chemically speaking, it's completely fine to irradiate water because whatever is formed as a result of radiolysis would just most of the time form water back, with the rest becoming very weak solution of hydrogen peroxide. this is big part of the reason why water is used as a coolant in nuclear reactors
there are also specific nuances to stopping anything that is not gammas, like secondary x-rays, gammas from neutron absorption etc and this actually favours light element shields, like water or liquid hydrogen, for this kind of radiation shielding
Okay, so where do the neutrons go in your head? Gotta go somewhere.
Re: your point about water in its purest form. It means zero contamination. We aren't even capable of doing that, and the purest we can make would kill humans pretty quickly for the similar amount we ingest.
what neutrons? we're talking about shielding of spacecraft moving out of earth's magnetosphere, not a spacecraft travelling through core of active nuclear reactor
the kind of radiation that is relevant are high energy protons (and alphas and electrons, with a sprinkle of heavier nuclei) from sun, mostly. there's no relevant source of neutrons
(and incidentally water is pretty good at absorbing neutrons too)
I think you are confused about how radiants work on Earth vs Space.
Again, the OP is about water "absorbing" radiation, and then being drinking water. It's not possible once past a certain amount. This is not possible.
I don't think it works that way. The water slows down the neutrons so that when and if they get to you they don't have enough energy to hurt you. The radiation doesn't contaminate the water any more than a microwave oven does.
They used the ice for everything, including cooling and heating the ship as needed. They got the bad effects from the cosmic radiation pinging in from all other directions, not from using the water. The volume of ice was larger than that of the ship, I think it also absorbed physical damage from micrometeorites. Let's hope someone in the Big Green Machine reads the novel.
I mean, they put nuclear waste at the bottom of miles deep water wells, because it absorbs alpha, gamma and beta particles and it's cheap.
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You would need a pretty good thickness of water and it becomes complicated shipping it up into space.
Well, the water is necessary for for life support and needs to be sourced somehow anyway. It kind of sets a minimum crew and passenger capacity if you want to make the most use of your shielding water.
Liquid and rockets is a death sentence.
Liquid and space vessels is worse.
Liquids on reentry is never going to happen.
Water doesn't have to be a liquid, but don't actual spacecraft typically contain liquids during wall of those cases? What do you mean?
You can freeze it before launch, but you'd have to freeze it again before reentry. Not possible, especially if you're talking about lining a craft with it during months of space travel. Water expands when frozen, and contracts when liquid. Metal does the opposite. How would you engineer that?
Why can't it stay liquid?
Didn't think I needed to stoop to that level. Thought I was talking to about obvious things and didn't want to sound patronizing.
Thanks for clearing that up.
Build the hypothetical ship in space and you never have to deal with it except as ice, which is easier to move around and shape into what you need. The ISS has a lot of liquids on board in all sorts of forms, from chicken soup, to ink pens, to the urine inside astronaut bladders. I don't understand what you're trying to say.
Do you even know what question you're responding to anymore? Wtf
Calm down, he was answering "how fast could we get there". It was never meant to be a realistic time frame.
His disdain for NASA's caution is obvious.