"on a trip to Mars, it’s distance from Earth, not duration of spaceflight, that becomes the bigger enemy. The ISS orbits about 200 miles away, just within Earth’s protective magnetic field. There, astronauts receive 10 times the usual amount of radiation, high-speed particles from the sun or other parts of the galaxy that tear through DNA molecules, that increase their risk of dying from cancer. Farther out, the exposure would get much worse."
Lead is a poor source of shielding in space as it's useless for anything but shielding, and you don't need high density. A much better option is to use fuel tanks and oxygen tanks.
Basically, in an emergency if you need more fuel or oxygen you need to have extra. However, trading off some shielding can defiantly be worthwhile in exchange for some extra fuel and or oxygen.
It's worse than that. Lead will actually make high energy charged particle radiation WORSE because it produces a whole bunch of secondary radiation. High atomic mass elements (metals) are the worst, and lead is very high atomic mass. For instance, check out this figure which looks at Tantalum and Tungsten (both similar to lead), which is actually higher than no shielding at all (the graph on the right):
https://www.researchgate.net/profile/Steve_Blattnig/publicat...
What you want is low atomic mass elements for galactic cosmic rays. Hydrogen is best, so you want fuel or plastic (polyethylene/polypropylene is the best plastic for radiation shielding). Water is also pretty good. As a zeroth order estimate, you look at the average atomic mass of the material to determine how well it shields galactic cosmic rays. So composites work better than aluminum.
Maybe the best economic option is to build a huge ship, that could be a captured asteroid, and place it in an permanent elliptic orbit near Earth's orbit in its perihelion and near Mars' orbit in its aphelion.
The best economic option is probably just to go really fast and use on-board supplies for solar flare protection.
If you get to Mars in 3 months versus 9 months, your radiation dose during transit is just a third. And that also means you may be able to reuse the ship every synod (26 months) instead of every 2 synods.
If you get to Mars in 3 months versus 9 months, your radiation dose during transit is just a third.
It seems more like a trade-off. A bulkier slower ship could offer better protection even for longer trips. Also you only need to power an elliptic orbiter once.
Getting radiation dose to just a third is incredibly hard with shielding.
Cyclers need periodic re-alignment and are so slow that you'd need multiples in order to have one for each window. Also, you still have to catch up to one. Overall, not a fantastic trade.
Retric outlined the best economic solution. Mainly it's not anything to worry about. You need some small area with heavy shielding to huddle in during solar flares, but the rest of the trip shielding isn't important. Explorers will happily a small increase in their lifetime cancer risk in exchange for visiting new worlds.
Eventually we'll have faster transits, and Aldrin Cyclers, and the problem will become even more minute.
No and no. Permanent magnets that would be strong enough to be effective would be too heavy. The power system to support effective electromagnets would be too heavy. It goes without saying that a thick lead layer would be too heavy.
One of the actual schemes discussed would be to have a solar flare emergency shelter that the astronauts could go to in case of a solar flare. This would use water as the shielding material, which would save weight, as water would have to be brought along in any case.
Heavy to shove out to sea from shore, but not if you've got a dock!
So you're proposing something like Aldrin's cycler craft. Given our experience on Mir and the ISS, we are going to have to get a whole lot better at environmental engineering to be able to do that for human passengers. I've read that the inside of the ISS smells like some kind of porta potty.
we need to become robots and cut out the malarkey.
I hope we will still have "human fundamentalists." (To use Charles Stross' term)
Electromechanical robotics is but an intermediate step. I can't wait to be an engineered lichen, with self-repair systems lifted from Deinococcus radiodurans.
I'm inclined to think that it's just too soon to go into space. It will truly become practical when biotech allows us to evolve into completely different forms that are more durable.
For protecting from the sun, would it be sufficient to have a separate craft on a parallel trajectory some distance away (let's say a couple miles) with a magnet or weak shield that deflects radiation by a small angle so that it misses the main ship?
Permanent magnets that would be strong enough to be effective would be too heavy.
Too heavy for what? Anyway, you took the magnets or lead suggestions too literally. They were in the broad direction of using a material isolation or some kind of electromagnetic shield. Why permanent magnets BTW?
Because you only said "magnets" so I debunked your proposal by subsets of the set "magnets" -- first tackling the permanent kind, then electromagnets.
in the broad direction of using a material isolation or some kind of electromagnetic shield.
Water would work as a shielding material. 6' of lunar or martian regolith would work as well. As for "some kind of electromagnetic shield" note that a huge electric charge would be relatively easy to establish, which would repel particles of like charge. However, this would cause particles of the opposite electric charge to rush towards what you're trying to shield, so that particle flow would have to be managed with a magnetic field. This has been discussed and researched since at least the 60's, actually. Managing such particle flows would involve a whole lot of engineering research and not an insignificant amount of power.
The point I'm trying to make, and it seems I'm failing miserably, is that whatever it needs to be done will be done. Unless astronauts' life is considered expendable.
A lot of engineering research? not an insignificant amount of power? too heavy? Do "cyclers" need realignement? Are they slow?
So what? Should we pack dozens of astronauts and hope at least a handful survive? That's the least realistic option IMO.
Lead isn't very useful for spaceflight. It's heavy, doesn't block radiation well, and doesn't have very many practical uses. Better would be organic compounds (food, fecal waste), or water.
As the article mentions, none of that is good enough to protect you from a solar flare, so for that, you can potentially reorient the ship to have its aft end pointed to the sun to block as much radiation as possible.
It's elevated but within today's (conservative) lifetime exposure limits. A trip to Mars would add a couple percentage points to your odds of getting cancer. Considering the numerous other ways such a trip could kill you, that's really rather in the noise.
Given that most of these cancers are 20-30 years after your trip, and treatments and cure rates improve over time, the risk is likely even lower than our current estimates.
A reciently documented phenomenon that surprised me was the observation that astronauts' core body temp can raise as high as 1°C after a few months in space. Sustaining an elevated CBT can cause both physical and cognitive issues. The human body does some strange things in zero-G.
If you like this article you'll probably also like astronaut Scott Kelly's book Endurance: A Year in Space, a Lifetime of Discovery[1]. My wife got it for me as a christmas present and so far it's really enjoyable.
I really wish we'd invest in developing a centrifugal alternative to gravity in space. It's good to know how the human body is affected by weightlessness but why bother?
The problem with a torus-form habitat is that it fits poorly onto a typical rocket. You can only fit a (long) tube onto a rocket.
This means that a non-trivial building effort is required in space, as opposed to just attaching more cylinders together, ISS-style. Inflated structures have some promise here, but you probably also need something more solid to attach life-critical systems to, and something thicker to serve as a radiation shield, even while below the Van Allen belt.
This is of course doable, but it's a new, untried territory, which means expensive R&D and even more expensive orbital operations. Without a pressing need to keep humans in space for years, it's unlikely to be undertaken. It's cheaper to build more efficient shuttle craft for space stations, and e.g. more efficient engines for a rocket to Mars, to cut the trip time.
The problem with a torus-form habitat is that it fits poorly onto a typical rocket. You can only fit a (long) tube onto a rocket.
No, but a cable fits nicely into a rocket. Dividing up the ship into two pods would get you a nice long radius to minimize Coriolis effects. If one pod contains a nuclear reactor, for which you need separation from the crew compartment, then it's quite convenient.
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[ 3.5 ms ] story [ 98.0 ms ] threadHow much worse does radiation exposure get?
Basically, in an emergency if you need more fuel or oxygen you need to have extra. However, trading off some shielding can defiantly be worthwhile in exchange for some extra fuel and or oxygen.
(from this paper: https://www.researchgate.net/publication/252405981_OLTARIS_A... )
What you want is low atomic mass elements for galactic cosmic rays. Hydrogen is best, so you want fuel or plastic (polyethylene/polypropylene is the best plastic for radiation shielding). Water is also pretty good. As a zeroth order estimate, you look at the average atomic mass of the material to determine how well it shields galactic cosmic rays. So composites work better than aluminum.
Maybe the best economic option is to build a huge ship, that could be a captured asteroid, and place it in an permanent elliptic orbit near Earth's orbit in its perihelion and near Mars' orbit in its aphelion.
If you get to Mars in 3 months versus 9 months, your radiation dose during transit is just a third. And that also means you may be able to reuse the ship every synod (26 months) instead of every 2 synods.
That's the plan for SpaceX's BFR/ITS.
It seems more like a trade-off. A bulkier slower ship could offer better protection even for longer trips. Also you only need to power an elliptic orbiter once.
Cyclers need periodic re-alignment and are so slow that you'd need multiples in order to have one for each window. Also, you still have to catch up to one. Overall, not a fantastic trade.
Eventually we'll have faster transits, and Aldrin Cyclers, and the problem will become even more minute.
No and no. Permanent magnets that would be strong enough to be effective would be too heavy. The power system to support effective electromagnets would be too heavy. It goes without saying that a thick lead layer would be too heavy.
One of the actual schemes discussed would be to have a solar flare emergency shelter that the astronauts could go to in case of a solar flare. This would use water as the shielding material, which would save weight, as water would have to be brought along in any case.
Heavy to shove out to sea from shore, but not if you've got a dock! (Read: build the craft already in space. And then have some mean engines.)
But this is all untenable; we need to become robots and cut out the malarkey.
So you're proposing something like Aldrin's cycler craft. Given our experience on Mir and the ISS, we are going to have to get a whole lot better at environmental engineering to be able to do that for human passengers. I've read that the inside of the ISS smells like some kind of porta potty.
we need to become robots and cut out the malarkey.
I hope we will still have "human fundamentalists." (To use Charles Stross' term)
Too heavy for what? Anyway, you took the magnets or lead suggestions too literally. They were in the broad direction of using a material isolation or some kind of electromagnetic shield. Why permanent magnets BTW?
in the broad direction of using a material isolation or some kind of electromagnetic shield.
Water would work as a shielding material. 6' of lunar or martian regolith would work as well. As for "some kind of electromagnetic shield" note that a huge electric charge would be relatively easy to establish, which would repel particles of like charge. However, this would cause particles of the opposite electric charge to rush towards what you're trying to shield, so that particle flow would have to be managed with a magnetic field. This has been discussed and researched since at least the 60's, actually. Managing such particle flows would involve a whole lot of engineering research and not an insignificant amount of power.
A lot of engineering research? not an insignificant amount of power? too heavy? Do "cyclers" need realignement? Are they slow?
So what? Should we pack dozens of astronauts and hope at least a handful survive? That's the least realistic option IMO.
One suggestion is to just line a ship with bags of water and then refill them with water recycled from urine and sweat. https://www.newscientist.com/article/dn23230-mars-trip-to-us...
As the article mentions, none of that is good enough to protect you from a solar flare, so for that, you can potentially reorient the ship to have its aft end pointed to the sun to block as much radiation as possible.
https://www.nature.com/articles/s41598-017-15560-w
[1] Amazon: http://a.co/bL0Tavv
This means that a non-trivial building effort is required in space, as opposed to just attaching more cylinders together, ISS-style. Inflated structures have some promise here, but you probably also need something more solid to attach life-critical systems to, and something thicker to serve as a radiation shield, even while below the Van Allen belt.
This is of course doable, but it's a new, untried territory, which means expensive R&D and even more expensive orbital operations. Without a pressing need to keep humans in space for years, it's unlikely to be undertaken. It's cheaper to build more efficient shuttle craft for space stations, and e.g. more efficient engines for a rocket to Mars, to cut the trip time.
No, but a cable fits nicely into a rocket. Dividing up the ship into two pods would get you a nice long radius to minimize Coriolis effects. If one pod contains a nuclear reactor, for which you need separation from the crew compartment, then it's quite convenient.
https://en.wikipedia.org/wiki/Centrifuge_Accommodations_Modu...