Author Topic: The no-compromise methalox solar storm shelter  (Read 3336 times)

Offline Burninate

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The no-compromise methalox solar storm shelter
« on: 08/27/2015 12:01 am »
Radiation shielding is heavy.  It blocks lower-energy particles, like the ones emitted from the Sun in great quantities when there's a solar particle event, much better than the steady background of high-energy galactic cosmic rays.  Blocking GCRs is nearly pointless, because you need kg/cm of shielding (tens of meters of solid material) to block out most of the incident energy.  Blocking solar particle event radiation is much easier, both because tens of grams per square centimeter is sufficient, and because generally you have some warning (20-60 minutes) of an event, which occurs only for hours or days;  Tight spaces are permissible.

Even so, tens of grams per square centimeter multiplies vehicle mass by a large factor.  Workable solar storm shelters rely on several tons of ECLSS water supply shunted into plastic bags, and only seal off a small closet-sized compartment within the habitat rather than trying to cover the whole thing.  That extra mass is still painful enough that lots of designs skip the whole matter and call solar particle events a known risk that can't be mitigated.

I got to thinking, though - on interplanetary spacecraft like MCT we already have lots of mass available to act as shielding;  It's already serving duty as propellant.  Methane and LOX need to spend most of their time in a thermally privileged position at 90K for zero-boiloff, well away from the 300K human accommodations, but twelve hours of boiloff is easy to accommodate in the grand scheme of things.  Slotting the habitat, or a small part of the habitat, into an array of propellant tanks (or an internal tank), and putting on some extra clothing and turning on some extra heaters, seems like a way to have your cake and eat it too.

So this thread is about designs that do that.

A few possibilities:
A) 6 to 18 long tanks, stacked hexagonally, with a center tank missing.  Slot in a tank-sized habitat in the center spot when it's time to shelter.  Bring water curtains in the walls full of liquid water, and you might not even have to heat the thing actively due to 273K freezing buffer.
B) One large tank, with an internal bulb welded in. Keep at 90K until need arises, then heat internal bulb to 270K and dock to hab.  Possibly use for food cold storage.
C) One large tank, with a narrow unpressurized internal passageway welded in, making the tank roughly toroidal.  Move skinny heated hab in on rails when needed.  Possibly use as navigable passageway to module on other side of tank.

Edit:
D) Small empty tanks surround the hab at all times, and are filled using a pump from the propellant tanks during a  storm
« Last Edit: 08/27/2015 03:03 pm by Burninate »

Offline nadreck

Re: The no-compromise methalox solar storm shelter
« Reply #1 on: 08/27/2015 12:13 am »
Since all these particles are coming from the same direction (while in interplanetary flight) why not just point the craft so that the fuel tank is between the crewed space and the sun?
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline Burninate

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Re: The no-compromise methalox solar storm shelter
« Reply #2 on: 08/27/2015 12:55 am »
Since all these particles are coming from the same direction (while in interplanetary flight) why not just point the craft so that the fuel tank is between the crewed space and the sun?
A friend with some knowledge of the area says that the normal solar particle radiation is effectively isotropic to a target, bouncing back and forth, albeit with some average bias outwards away from the Sun.  Solar particle events have much greater bias, and are travelling outwards rapidly, but upon further reading, they are apparently still erratic enough that a point target can expect incoming radiation from all sides.

Quote
The design is flawed, however, in that it assumes that the incoming protons in an SPE are highly directional and so really provides only a sector-type shield configuration. In fact, the energetic protons that arrive initially are highly directional, but the spectrum quickly becomes isotropic before any significant dose is received. Hence, assuming that one can point a sector shield in some particular direction and effectively shield from SPE protons arriving from all directions is just not a valid assumption.
- http://engineering.dartmouth.edu/~d76205x/research/Shielding/docs/Townsend_05.pdf
« Last Edit: 08/27/2015 12:56 am by Burninate »

Offline Stormbringer

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Re: The no-compromise methalox solar storm shelter
« Reply #3 on: 08/27/2015 09:05 am »
There was a recent article on CERN (I think it was) developing a SC magnetic shield for radiation.

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Offline Vultur

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Re: The no-compromise methalox solar storm shelter
« Reply #4 on: 08/30/2015 06:39 am »
That extra mass is still painful enough that lots of designs skip the whole matter and call solar particle events a known risk that can't be mitigated.

BTW, how common are solar events sufficient to cause acute radiation sickness? How common are potentially lethal ones?

Offline Stormbringer

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Re: The no-compromise methalox solar storm shelter
« Reply #5 on: 08/30/2015 12:20 pm »
Also there have been a couple of recent biomedical discoveries about compounds which make radiation more survivable. One protects the gut lining which is one of the short term killers in radiation exposure. Another protects and repairs DNA. esentially it makes 2 times the normal Lethal does survivable.

one was an extract from cruciferous vegetables and I forgot the other but it was a different mechanism.
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Offline philw1776

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Re: The no-compromise methalox solar storm shelter
« Reply #6 on: 09/01/2015 06:02 pm »
Radiation shielding is heavy.  It blocks lower-energy particles, like the ones emitted from the Sun in great quantities when there's a solar particle event, much better than the steady background of high-energy galactic cosmic rays.  Blocking GCRs is nearly pointless, because you need kg/cm of shielding (tens of meters of solid material) to block out most of the incident energy.  Blocking solar particle event radiation is much easier, both because tens of grams per square centimeter is sufficient, and because generally you have some warning (20-60 minutes) of an event, which occurs only for hours or days;  Tight spaces are permissible.

Even so, tens of grams per square centimeter multiplies vehicle mass by a large factor.  Workable solar storm shelters rely on several tons of ECLSS water supply shunted into plastic bags, and only seal off a small closet-sized compartment within the habitat rather than trying to cover the whole thing.  That extra mass is still painful enough that lots of designs skip the whole matter and call solar particle events a known risk that can't be mitigated.

I got to thinking, though - on interplanetary spacecraft like MCT we already have lots of mass available to act as shielding;  It's already serving duty as propellant.  Methane and LOX need to spend most of their time in a thermally privileged position at 90K for zero-boiloff, well away from the 300K human accommodations, but twelve hours of boiloff is easy to accommodate in the grand scheme of things.  Slotting the habitat, or a small part of the habitat, into an array of propellant tanks (or an internal tank), and putting on some extra clothing and turning on some extra heaters, seems like a way to have your cake and eat it too.

So this thread is about designs that do that.

A few possibilities:
A) 6 to 18 long tanks, stacked hexagonally, with a center tank missing.  Slot in a tank-sized habitat in the center spot when it's time to shelter.  Bring water curtains in the walls full of liquid water, and you might not even have to heat the thing actively due to 273K freezing buffer.
B) One large tank, with an internal bulb welded in. Keep at 90K until need arises, then heat internal bulb to 270K and dock to hab.  Possibly use for food cold storage.
C) One large tank, with a narrow unpressurized internal passageway welded in, making the tank roughly toroidal.  Move skinny heated hab in on rails when needed.  Possibly use as navigable passageway to module on other side of tank.

Edit:
D) Small empty tanks surround the hab at all times, and are filled using a pump from the propellant tanks during a  storm

After departure from Earth to Mars or vice versa, what % of the tanks will still house propellant?
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Offline Stormbringer

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Re: The no-compromise methalox solar storm shelter
« Reply #7 on: 09/01/2015 06:24 pm »
What about a refueling tanker? Now i know part of the power of a rocket is that as a rocket uses fuel it gets less massive and can go faster but would a tanker refueling be disasterous to the mass fraction part of the calculation?
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Offline Prober

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Re: The no-compromise methalox solar storm shelter
« Reply #8 on: 09/02/2015 04:55 pm »
There was a recent article on CERN (I think it was) developing a SC magnetic shield for radiation.

You can take the idea and build composite tankage with layer(s) of shielding using Graphene or other materials now available off the shelf.

http://forum.nasaspaceflight.com/index.php?topic=33141.msg1419881#msg1419881
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