Potential of slight artificial gravity to mitigate space travel issues

[Shavano]

When I say impossible here's what I mean: it's impossible on time scales that humans care about. It defies human psychology, which overwhelmingly weights short term benefits and costs more than long term benefits and overwhelmingly more than benefits that might hypothetically acrue to someone you will never know, never see, and never have any idea whether you helped or hurt. As much as there are a lot of people enthusiastic about space travel they're not actually enthusiastic about any kind of interstellar travel that might be physically possible. They're only enthusiastic about fictional faster than light travel because that's the only kind where you don't have to permanently give up any chance of going home while subjecting yourself to privations that would seem extreme compared to literally everywhere on Earth or even Mars.

People don't organize trips that expend unfathomably large amounts of resources to permanently leave a place that's pretty nice to live in for the chance to almost certainly die on the way to someplace that will be worse than all the places in easy reach, nor do they organize such trips for their offspring unless they are sociopaths, and sociopaths wouldn't do it either because there's nothing in it for them.

 

[Chuckles]

You seem very emphatic about it. Why can space travel NEVER be as cheap or as safe as air travel? SpaceX is certainly doing a lot of work towards getting costs down, and you didn't specify which particular cost metric you're using? If it's $ per passenger-mile, I think a crew dragon going to ISS can get pretty close to early air travel costs, if you allow the costs to put up ISS to be sunk. (And overhead associated with keeping ISS livable is also much lower using commercial space launches that it was under the Space Shuttle.) And modern airports aren't exactly cheap...

There's a couple of big reasons.

1. Space is really hostile to life. I mean really fucking absurdly hostile. There's no oxygen (3 min) and it's kinda hard to get rid of your carbon dioxide. There's no water (3 days). If you are operating, it's hard to get rid of your waste heat. If the power isn't running, things will get a wee bit chilly. There are periodic bouts of absurd amounts of radiation. There's no easily accessible source of food or supplies once you leave Earth (3 weeks). And to boot, getting to the one known safe place involves extreme temperatures on the outside of the spacecraft that is protecting you. The times in parentheses are about how long you have to solve the problem before you die.

You're going from an environment where you have oxygen within 3 minutes, water within 5-10 minutes, and food within 4-5 hours, to one where where all of these things are (at current technologies) hours (LEO), days (cis-lunar), and months (cis-martian).

Here's an example:
One of the challenges that is an unaddressed known risk for a trip to Mars is that a coronal mass ejection will generate lethal amounts of radiation over a large swath of space. If you're downrange, you've got just a few hours to get clear, and a whole lot of distance to get clear of. The plans for mitigation I've read about are: carry a bunch of water (mass) and have everyone hide behind it.

Look at the critical things above: food, water, air. Any system associated with those is fault critical. Likewise anything that deals with navigation, thrust, or thermal conditioning is fault critical. OK, now any system that supports the things above is fault critical. As in it fails, you die.

To mitigate (not eliminate) the risks, it means that the equipment has to be designed to be very reliable in very extreme environments, and you need to carry multiple redundant sets of equipment and spare supplies. And then you get to do a lot of praying that you don't have common mode failures.


2. At the beginning of the last century, a notable science fiction author determined the equation of state for reaction engines (any and all). This is known as the Tsiolkovsky rocket equation.

M_i/M_f=e^deltaV/Ve

M_i is how much mass your rocket has to start.
M_f is the amount of mass to deliver to your destination.
deltaV is how much you need to change your velocity. For low earth orbit, this is about 9 km/s.
Ve is the exhaust velocity, i.e. how fast you can throw mass out of the back of your rocket.

The current engine technologies give us a Ve of about 3.2 km/s.

Plugging that in gives that our initial mass needs to be about 11X what we deliver. Or, for every kg we deliver (spacecraft and cargo) we need 10 kg of fuel and oxidizer.

That's a lot of fuel and oxidizer, compared to the structure of the spacecraft. And since you have both is close proximity, there's really not much separating you from a wanton orgy of devastation.

Also, when you light off the engines and start chucking mass out the back at high speed, you get a lot of vibration, and there's really nowhere for it to go, so vibration loads are very high and thus fatigue damage is also high.

Point 1 means you need to take a lot of stuff with you to make sure that you can continue operating after one or more failures in a given system. Point 2 means you don't have a lot of mass budget with which to do it in. So, that means that everything has to be heavily engineered to shave off weight which means high cost, and also means staring hard at the safety margins and trying to trim as much fat off of them as possible, which means a lot less margin for error.

Years ago, when I first became really into space, the thought was that $1000/kg to LEO was about the limit of what we could do. SpaceX is currently at ~$2700/kg. At $1000/kg, you're looking at a minimum cost of about $100,000/seat.

Let's put it this way, right now, there are no flying rockets that can fly and safely recover after critical engine out at launch. Astra barely avoided a RUD on pad when they lost one. Every commercial aircraft on the market today has this capability proven.

 

[Quarthinos]

Let's put it this way, right now, there are no flying rockets that can fly and safely recover after critical engine out at launch. Astra barely avoided a RUD on pad when they lost one. Every commercial aircraft on the market today has this capability proven.

Space Shuttle did this on at least one occasion. STS-51-F had an entire SSME shut down during launch. The Shuttle continued the mission at a lower then planned orbit.

Also, I'm pretty sure that NO aircraft can actually get airborne if an engine fails during the rollout. And aircraft can continue to its destination if an engine fails AFTER takeoff and climb out, but that's not the same as failing during launch.

I dimly remember that perhaps a B-52 can suffer an engine out during takeoff/ascent and not immediately crash, but only if the pilot realizes what's happening and immediately dumps most of the fuel and drops ALL the cargo to lose weight, at which point they turn around and immediately land, which is what escape towers are for.

Also, I am aware of the Rocket Equation, and have enough hours of KSP (and way too many credit hours of mathematics) to prove it.


As far as the "space is hostile" argument.. Yes. Sea travel also used to kill people in job lots because scurvy and all the other logistic problems. Now it's routine.

 

[Quarthinos]

When I say impossible here's what I mean: it's impossible on time scales that humans care about. It defies human psychology, which overwhelmingly weights short term benefits and costs more than long term benefits and overwhelmingly more than benefits that might hypothetically acrue to someone you will never know, never see, and never have any idea whether you helped or hurt. As much as there are a lot of people enthusiastic about space travel they're not actually enthusiastic about any kind of interstellar travel that might be physically possible. They're only enthusiastic about fictional faster than light travel because that's the only kind where you don't have to permanently give up any chance of going home while subjecting yourself to privations that would seem extreme compared to literally everywhere on Earth or even Mars.

People don't organize trips that expend unfathomably large amounts of resources to permanently leave a place that's pretty nice to live in for the chance to almost certainly die on the way to someplace that will be worse than all the places in easy reach, nor do they organize such trips for their offspring unless they are sociopaths, and sociopaths wouldn't do it either because there's nothing in it for them.

You're now saying interstellar (or possibly interplanetary) space flight will never be done because of psychology. That's not the point I was trying to refute. You said space flight can never be as cheap or safe as air travel, which is not the same, and I showed several possible counterexamples.

 

[Shavano]

You're now saying interstellar (or possibly interplanetary) space flight will never be done because of psychology. That's not the point I was trying to refute. You said space flight can never be as cheap or safe as air travel, which is not the same, and I showed several possible counterexamples.

That's fair enough, but I'll let Chuckles' response deal with why it can't be as cheap or safe.

 

[Chuckles]

Space Shuttle did this on at least one occasion. STS-51-F had an entire SSME shut down during launch. The Shuttle continued the mission at a lower then planned orbit.

Also, I'm pretty sure that NO aircraft can actually get airborne if an engine fails during the rollout. And aircraft can continue to its destination if an engine fails AFTER takeoff and climb out, but that's not the same as failing during launch.

I dimly remember that perhaps a B-52 can suffer an engine out during takeoff/ascent and not immediately crash, but only if the pilot realizes what's happening and immediately dumps most of the fuel and drops ALL the cargo to lose weight, at which point they turn around and immediately land, which is what escape towers are for.

The SSME was later in flight. The absolute worst time to lose an engine is at T+0.1s. You’re just off the pad, but are at 99% of launch mass.

A LES is the equivalent of an ejection seat. It will get you clear of the unfolding disaster, but it’s a high g sleigh ride. An average passenger is going be only mostly alive. Heck, fit astronauts and fighter pilots come out looking like they lost a fight with a meat tenderizer.

Military tends to be more sporty on safety, especially older military. Every part 25 aircraft, from a HondaJet, or Gulfstream to a 737, A330, or 777 can get off the ground and safely fly and land when an engine fails at V1 or beyond. V1 being the speed at which the aircraft is committed to take off.

 

[Quarthinos]

Every part 25 aircraft, from a HondaJet, or Gulfstream to a 737, A330, or 777 can get off the ground and safely fly and land when an engine fails at V1 or beyond. V1 being the speed at which the aircraft is committed to take off.

I guess that's why runway lengths are such an important metric. I was not aware that the requirements were that strict. (And I'd think that if you lost an engine that early, you're required to land the aircraft as soon as possible?)

But to go back to the original point, the Wright Flyer and Sopwith Camel probably didn't have such restrictions. And flying boats were so popular in ye olden days of flight for a reason. Rockets aren't up to those kinds of restraints yet, but they could be. In theory, a Falcon 9 could just decrease MTOW by 11% (or maybe 1/8, rather than 1/9?) and suddenly you can lose an engine at T+0.0001s and still get to something approaching orbit. Progress isn't used for crew launches for a reason..

 

[Chuckles]

I guess that's why runway lengths are such an important metric. I was not aware that the requirements were that strict. (And I'd think that if you lost an engine that early, you're required to land the aircraft as soon as possible?)

But to go back to the original point, the Wright Flyer and Sopwith Camel probably didn't have such restrictions. And flying boats were so popular in ye olden days of flight for a reason. Rockets aren't up to those kinds of restraints yet, but they could be. In theory, a Falcon 9 could just decrease MTOW by 11% (or maybe 1/8, rather than 1/9?) and suddenly you can lose an engine at T+0.0001s and still get to something approaching orbit. Progress isn't used for crew launches for a reason.

Flying boats were popular mostly because anything “long range” required a long runway, which were scarce, and because their range was still fairly short, required fuel stops in inconvenient places.

Even then, the reliability of the systems at the time meant that finishing a flight with one or more engines inoperative was quite likely.

Further, air travel in the 1930s was still both quite dangerous and expensive.

 

[Megalodon]

I guess that's why runway lengths are such an important metric. I was not aware that the requirements were that strict. (And I'd think that if you lost an engine that early, you're required to land the aircraft as soon as possible?)

You think you get to zero fatal accidents in a year for a gigantic global industry doing safety on a best effort basis?

And yes, you would typically dump fuel (to get to an acceptable landing weight) and land ASAP.

 

[Bezoar]

A human wearing a bodysuit/embedded with microprocessor controlled vectorable electromagnets in a constant magnetic field could experience forces with safety monitoring by the microprocessor to prevent high energy collisions.

Large scale magnetic fields can also be used to deflect charged particles away from habitation areas and utilized in a magnetic sail.

 

[rain shadow]

A human wearing a bodysuit/embedded with microprocessor controlled vectorable electromagnets in a constant magnetic field could experience forces with safety monitoring by the microprocessor to prevent high energy collisions.

A variation that comes to mind is a one-way flow of air that just gently pushes you towards the floor. A spacecraft in microgravity has to have strong air circulation anyway, might as well use it to get some free partial gravity. Use baggy clothes and you can probably get over 0.1g without even trying.

 

[Bezoar]

Airflow is something that humans innately understand, the comm earbuds/headset should take care of most of the noise and a permeability controlled and turbulence enhancing suit can increase the downforce and control windchill.

 

[Megalodon]

Gotta say, we're drifting back into profoundly unrealistic concepts here.

A human wearing a bodysuit/embedded with microprocessor controlled vectorable electromagnets in a constant magnetic field could experience forces with safety monitoring by the microprocessor to prevent high energy collisions.

Large scale magnetic fields can also be used to deflect charged particles away from habitation areas and utilized in a magnetic sail.

I think getting macroscopic forces this way would be very difficult, you'd need fields comparable to an MRI machine, and a notable issue with MRI machines is that they're very cramped and require liquid helium coolant.

A variation that comes to mind is a one-way flow of air that just gently pushes you towards the floor. A spacecraft in microgravity has to have strong air circulation anyway, might as well use it to get some free partial gravity. Use baggy clothes and you can probably get over 0.1g without even trying.

Sorry but what? This would be like living in a wind tunnel. You wouldn't be able to work with anything delicate and you'd be so sick of it you'd be ready to pop the airlock after an hour.

 

[Megalodon]

Airflow is something that humans innately understand, the comm earbuds/headset should take care of most of the noise and a permeability controlled and turbulence enhancing suit can increase the downforce and control windchill.

Come on, it would be like skydiving full time. No one can get used to that.

 

[Shavano]

A human wearing a bodysuit/embedded with microprocessor controlled vectorable electromagnets in a constant magnetic field could experience forces with safety monitoring by the microprocessor to prevent high energy collisions.

Large scale magnetic fields can also be used to deflect charged particles away from habitation areas and utilized in a magnetic sail.

Oh heck just put a few megavolts on them and put a plate below the (nonconducting of course) deck with an opposite charge. What could go wrong?

 

[Bezoar]

Come on, it would be like skydiving full time. No one can get used to that.

You might be surprised at what humans can acclimatize to.

Oh heck just put a few megavolts on them and put a plate below the (nonconducting of course) deck with an opposite charge. What could go wrong?

Starting with the fundamental forces of nature, that was my first thought - but then immediately ran into the dielectric breakdown of gases and the problems associated with moisture contamination of those gases in the presence of humans.

Haven't done any testing or calculations but some first order testing on the magnet concept could give some preliminary feedback, likely want to avoid conductors passing through a strong magnetic field, have to be careful with jewelry, tools, pacemakers, and other embedded metals.

Remember an MRI a few years back, I had small burns in a number of places, many easily identified as metal bits and pieces from technician supplied gear, others from metal slivers and other embedded conductive residue scattered across my body.
_____

In summary, our current understanding of gravity limits us to classical mechanical acceleration.

We can manipulate the electromagnetic force through various schemes to generate forces.

The strong and weak forces have unusable distance scales for this application.

 

[Shavano]

summary, our current understanding of gravity limits us to classical mechanical acceleration.

Saying "our current understanding of gravity" unnecessarily and misleadingly suggests that there might be some end run around how gravity and acceleration work. If there is, it's at energies that couldn't be realized on a planet, much less a space ship.

The original question IMO is still a good one. There might be some utility in producing artificial gravity (using mechanical acceleration) on a ship in flight between planets. There are definitely some advantages, but the utility might not outweigh the operational difficulties it would create, or be worth the extra fuel it would take to have tethers and a counterweight.

 

[Megalodon]

You might be surprised at what humans can acclimatize to.

Fair enough, has there been a study of people spending long periods of time in one of those vertical wind tunnels that I haven't heard of?

Haven't done any testing or calculations but some first order testing on the magnet concept could give some preliminary feedback, likely want to avoid conductors passing through a strong magnetic field, have to be careful with jewelry, tools, pacemakers, and other embedded metals.

Remember an MRI a few years back, I had small burns in a number of places, many easily identified as metal bits and pieces from technician supplied gear, others from metal slivers and other embedded conductive residue scattered across my body.

It's not the magnetic field that's responsible for the heating in an MRI, it's the RF emissions.

 

[Bezoar]

Long duration spaceflight will likely have HVAC and radiation shielding components, engineered appropriately these components can provide various forces on a human in a bodysuit.

Food systems will require other engineering, can't imagine fitting a herd of cows or a flock of chickens with bodysuits. Lower trophic scale organisms will be more efficient and many probably don't need gravity.

 

[Shavano]

taking a herd of cows extraplanetary seems like a solution problem looking for a problem.

 

[Bezoar]

Aye, but if it is solved imagine all the other problems that are solved along with it.

 

[Megalodon]

Long duration spaceflight will likely have HVAC and radiation shielding components, engineered appropriately these components can provide various forces on a human in a bodysuit.

Okay, but given both have been raised already and serious barriers for artificial gravity have been pointed out, have you developed this idea further? Or is it just going to be repeating the thesis statement?

Seems like the exoskeletons designed for industrial use (lifting etc) might be a more useful model here. These would be able to impart the desired forces without requiring untenable environmental conditions or engineering challenges. Exoskeletons would be able to attach to the ceiling to provide down-force.

There'd still be other problems though. Problems like deterioration of eyesight in weightlessness would still happen.

 

[Bezoar]

Problems like deterioration of eyesight in weightlessness would still happen.

That's caused by fluid shifts associated with general dysregulation of homeostasis, just the act of working against any forces on an ongoing basis will modify these fluid flows, and no I haven't done a double-blind placebo-controlled study.

I googled the concepts being objected to from my posts, there is NASA literature related to said concepts.

 

[Shavano]

It would be really unfortunate (and I think it must be unknown) if the gravity on Mars or the Moon fell into a bad band where the stresses weren't enough to promote enough muscle and ligament strengthening to prevent injury. I don't see how we can find that out without people actually living in those situations long term. It's another reason going to Mars before we've had a few years of a lunar space colony is a bad idea.

 

[deadman12-4]

A human wearing a bodysuit/embedded with microprocessor controlled vectorable electromagnets in a constant magnetic field could experience forces with safety monitoring by the microprocessor to prevent high energy collisions.

Large scale magnetic fields can also be used to deflect charged particles away from habitation areas and utilized in a magnetic sail.

you GREATLY underestimate the force needed to prevent cosmic ray strikes. A couple double AAs in your pockets are very much not enough energy for that, much less your magic suit that leaves your most important bits (like your head) uncovered.
PopSci greatly misunderstands how radiation works.

Beyond that, NASA has been finding alot of issues that are not as well known about life in space, heart damage due to radiation, all sorts of things.

 

[Shavano]

I read that as your whole ship is surrounded by a big magnetic field that maybe has some chance of deflecting some cosmic rays and the little magnets on your suit are to orient yourself and give an illusion of gravity to astronauts inside the larger field.

But likely what you say is true of the big magnetic field too. We're talking about particles with a lot of momentum.

 

[deadman12-4]

I read that as your whole ship is surrounded by a big magnetic field that maybe has some chance of deflecting some cosmic rays and the little magnets on your suit are to orient yourself and give an illusion of gravity to astronauts inside the larger field.

But likely what you say is true of the big magnetic field too. We're talking about particles with a lot of momentum.

plus gigantic high powered magnets have effects on electronics too

 

[Shavano]

plus gigantic high powered magnets have effects on electronics too

Not that big a deal for a static field.

 

[deadman12-4]

Not that big a deal for a static field.

if only the world was made of gigantic spherical cows that all lived in a vacuum...

 

[Shavano]

if only the world was made of gigantic spherical cows that all lived in a vacuum...

We are literally talking about living in a vacuum, but great points for condescension.

 

[dmsilev]

Not that big a deal for a static field.

When talking about magnetic fields that are Sufficiently Strong to deflect cosmic rays? Obvious effects: any inductor or ferrite filter in your circuit is going to be very unhappy. The combination of magnetoresistance and possible Hall voltages might result in voltages that you’re not expecting. Better hope that the band structures of all of your transistors aren’t too field-dependent or exhibit any significant spin polarization, otherwise things really are going to go to hell in a handbasket.

Note that the level of problems that you’ll have will depend on just how big Sufficiently Strong ends up being. One Tesla? Yeah, your ferrites and inductor cores will saturate, and thats probably about it. Ten or hundred T? The current paths in your wires and ground planes are going to get weird. Thousands of T? It’s predicted that silicon's band gap will close at around 20 kiloTesla. That’s for pure Si; not sure anyone has tried to do the calculations with dopants added in, but I’d expect the scale to drop significantly.

 

[Shavano]

When talking about magnetic fields that are Sufficiently Strong to deflect cosmic rays? Obvious effects: any inductor or ferrite filter in your circuit is going to be very unhappy. The combination of magnetoresistance and possible Hall voltages might result in voltages that you’re not expecting. Better hope that the band structures of all of your transistors aren’t too field-dependent or exhibit any significant spin polarization, otherwise things really are going to go to hell in a handbasket.

Note that the level of problems that you’ll have will depend on just how big Sufficiently Strong ends up being. One Tesla? Yeah, your ferrites and inductor cores will saturate, and thats probably about it. Ten or hundred T? The current paths in your wires and ground planes are going to get weird. Thousands of T? It’s predicted that silicon's band gap will close at around 20 kiloTesla. That’s for pure Si; not sure anyone has tried to do the calculations with dopants added in, but I’d expect the scale to drop significantly.

Here let me quote myself:

I read that as your whole ship is surrounded by a big magnetic field that maybe has some chance of deflecting some cosmic rays and the little magnets on your suit are to orient yourself and give an illusion of gravity to astronauts inside the larger field.

But likely what you say is true of the big magnetic field too. We're talking about particles with a lot of momentum.

the Earth's magnetic field does provide some protection from cosmic radiation. That's due to a 25-65 micro-Tesla field that extends for tens of thousands of kilometers. I don't know how that kind of effect scales with size. If it's a millionth of the size does it have to be a million times stronger to get the same effect? If so yea, magnetic radiation shielding isn't viable. But manipulation of magnetic objects using magnetic fields is.

 

[dmsilev]

The Earth's field, weak as it is, provides protection because it's huge in spatial extent. You need to curve the cosmic rays away from your target, which can either be done with gentle bending via a small field magnitude over several tens of thousands of kilometers or a much sharper bend on a much smaller length scale. So for a scale length of a few tens of meters, a factor of a million or so smaller than the magnetosphere, field strength is going to have to be a million or so times stronger. So, probably 50-100 T minimum (remember that Earth also has tens of km of atmospheric shielding to back up the magnetic field…).

It should be noted by the way that there are only a handful of magnets worldwide which run in that range, their volume is measured in cubic centimeters not meters, and at the upper end of the range you’re thoroughly in pulse magnet territory, so the field is only on for tens or hundreds of milliseconds at a time. This is way outside anything we’re close to being able to build.

 

[deadman12-4]

We are literally talking about living in a vacuum, but great points for condescension.

Simply pointing out your easy fix is anything but simple or easy once you consider implementing it, as others have explained. Thats how most sci fi/popsci explanations work. Cant you just do "x", when in reality its hideously complicated but all the complications are ignored.

Also, earths atmosphere does ALOT of the protection, not just the magnetic field. The magnetic field doesn't turn away all the iron nuclei, the air molecules collide with them to stop them. Nothing to do with magnetic fields, but internet explanations just say its magnetic fields

 

[Shavano]

Simply pointing out your easy fix is anything but simple or easy once you consider implementing it, as others have explained. Thats how most sci fi/popsci explanations work. Cant you just do "x", when in reality its hideously complicated but all the complications are ignored.

It' wasn't my idea at all. It was Bezoar's and I expressed doubt about that part of it.

I think we're agreed that there are big technical problems with shielding deep space travelers from radiation, and huge unknowns involved in sending them to another planet that make the prospect extremely risky unless we work out a lot of basic science first, and IMO even if we do.

Current ideas for sending humans beyond the moon aren't serious, IMO.

 

[demultiplexer]

Can you all just start reading scifi this has been figured out by people like Asimov who was a celebrated biologist besides being a scifi writer.

Forcefields, which is essentially what you all are talking about, don't work. Deflecting charged particles is technically possible, especially if you can put a magnetic field really far outside of your spaceship, but there are also a sufficient number of massive and neutral cosmic rays that won't be (sufficiently) deflected and can cause a lot of wear on relevant timescales. You have to simulate an atmosphere to get sufficient shielding.

And that's not actually that hard. If you're considering a long-stay spaceship anyway, you're going to need a lot of water, so the default option in scifi has been to put a few meters of water around the spaceship. It's stuff you need anyway, and it's good shielding. For larger space habitats like O'Neill cylinders, you typically go and find an asteroid that you hollow out, using the material of the asteroid as shielding alongside a small lake's worth of water.

With about 1 meter of water, you can shield a few sigma of radiation. Not nearly earth's surface levels of radiation, but better than anything we've made so far. At about 10 meters of water, you get shielding on par with Earth's atmosphere (about the equivalent of a ~25km thick atmosphere).

And yes, this is also why I'm always talking about new launch systems. We need to be emptying out lake Baikal and shooting it into space.

 

[Shavano]

As long as the spacecraft doesn't have to go anywhere sure, why NOT increase the amount of fuel you need by a factor of a few thousand and increase the cost of everything by the same factor?

And if you don't need to go anywhere, why go to space at all?

 

[MilleniX]

lake Baikal

Is that also going to supply all of their needs for rare minerals?

 

[Megalodon]

Here let me quote myself:

the Earth's magnetic field does provide some protection from cosmic radiation. That's due to a 25-65 micro-Tesla field that extends for tens of thousands of kilometers. I don't know how that kind of effect scales with size. If it's a millionth of the size does it have to be a million times stronger to get the same effect? If so yea, magnetic radiation shielding isn't viable. But manipulation of magnetic objects using magnetic fields is.

Does Earth's magnetic field do all that much against cosmic rays? Those are quite high energy, hundreds of MeV. My understanding is most of the effect is against solar radiation, which is much lower energy, more like KeV. Solar radiation is important for atmosphere loss because there's so much of it so the magnetic field is important to maintaining Earth's habitability in the very long term, but as far as I understand it most of the protection against cosmic rays is from the atmosphere tanking them. The atmosphere is equivalent to a 34 foot water column, which is a lot as far as shielding goes.

 

[Megalodon]

As long as the spacecraft doesn't have to go anywhere sure, why NOT increase the amount of fuel you need by a factor of a few thousand and increase the cost of everything by the same factor?

And if you don't need to go anywhere, why go to space at all?

It's not the universe's job to supply us with a space environment that we can easily tolerate. Generating a strong enough magnetic field may not be practical, in which case water may well be the most mass-efficient shielding, since water is needed anyway. This is quite scale-dependent, if you have a ship that's even slightly larger, like the inflatable habitat concepts for example, it gets a lot easier to use necessary storage mass and just structure to do more shielding.

The baseline plan should be an inflatable habitat with a water bladder around the outer areas. The water can be delivered in arbitrarily many additional launches, and used for oxygen generation, reaction mass, and other uses en route. This would potentially reduce shielding mass, but you're optimizing for reduced dose over the whole trip so it's possible to design for that target even if shielding is slightly reduced at end of mission. It's also possible to replace water shielding mass with waste (assuming it's bagged up and sealed well, lol) over the course of the mission. I think you'd have a hell of a time outperforming this with any currently available or foreseeable technology.

You can probably contemplate a 1T magnetic field, but I'm not sure that'll be enough. But I don't think you can generate a 10T magnetic field across a large enough area to be useful for space travel. I think if you did do that you'd already have spent enough mass on superconducting coils and cryogenic coolers and the like that you would have come out ahead just using water.