Death Via Stainless Steel Hull.

[Spacescifi]

 

Elon is designing a stainless steel starship. But won't steel react with the cosmic ray particles in space and do damage to the crew? Cancer?

They may be shielded by other materials somewhat, but in general, thicker materials shield better, but space is a limited thing on a spaceship optimized for long range travel.

 

Edited October 3, 2019 by Spacescifi
Words

[ThatGuyWithALongUsername]

Maybe the heat shield could double as a radiation shield? Or is it still better to use the tanks (engine facing sun during cruise?)

Don't think that will really be needed though. Thing is, there IS enough room for extra shielding. It's not technically optimized for mass like you suggest, it's optimized for maximum payload thanks to refueling. Basically, it can take 100 to 150 tons to Mars no problem thanks to refueling. As for volume, the pressurized volume is larger than that of the entire international space station. I think you can fit some shielding in there and still have ample room for several months habitation (not for 100 people, like Musk keeps suggesting, but that's because I don't believe they'd reach that number for anything outside Earth's SOI anyway, that's probably for the even more future 18m version IMO)

[tater]

Galactic Cosmic Rays are isotropic, and don't care about steel or not steel. You either put people inside propellant tanks or you live with minor mitigation (some plastics are pretty good here, actually). Best shielding is to reduce travel time. Basically, take the mission length for ISS that is about the same as your transit, and double the dose to see what the transit dose is (half the sky is shielded by Earth for ISS).

[Nothalogh]

1 hour ago, Spacescifi said:

 

Elon is designing a stainless steel starship. But won't steel react with the cosmic ray particles in space and do damage to the crew? Cancer?

They may be shielded by other materials somewhat, but in general, thicker materials shield better, but space is a limited thing on a spaceship optimized for long range travel.

 

One of the best ways of mitigating radiation is to minimize cumulative exposure, followed by shielding methods.

 

[Spacescifi]

Just now, Nothalogh said:

One of the best ways of mitigating radiation is to minimize cumulative exposure, followed by shielding methods.

 

 

True. Months of spaceflight seem counterproductice to that.

Faster drives would be ideal, but we know project Orion will probably never see the light of day so it is almost pointless for me to suggest it as a possible solution.

[Nothalogh]

Just now, Spacescifi said:

 

True. Months of spaceflight seem counterproductice to that.

Faster drives would be ideal, but we know project Orion will probably never see the light of day so it is almost pointless for me to suggest it as a possible solution.

This is one of the reasons that Musk is pursuing high TWR transfers and aerocapture at destination.

[Spacescifi]

8 minutes ago, Nothalogh said:

This is one of the reasons that Musk is pursuing high TWR transfers and aerocapture at destination.

 

Smart, but we and he will find out if it is fast enough... or not.

Surgery in low or zero g to cut out a tumor would be... interesting.

[tater]

People have already stayed on ISS for time frames that provide comparable GCS exposures.

[kerbiloid]

If they take a library, the 20 cm layer of cellulose will be an additional 20 g/cm² protection.

Do like the books, they're your friends!

P.S.
Also they can be are a hydrogen or water backup source.
(C₆H₁₀O₅)_n, so 550 g of water can be produced from 1 kg of the books.
7 kg of books = 1 human * day of drinking and breathing.

Edited October 3, 2019 by kerbiloid

[Spacescifi]

52 minutes ago, tater said:

People have already stayed on ISS for time frames that provide comparable GCS exposures.

 

Are you aware that Earth's magnstic field shields the ISS?

A stainless steel starship travelinf for months or a year will get more than the ISS.

I may not be an expert on rocketry like some here, but I do know stuff across,a wide array of subjects. As a writer it was required.

[tater]

45 minutes ago, Spacescifi said:

Are you aware that Earth's magnstic field shields the ISS?

The Earth's magnetic field is only an issue for lower energy particles. It does a lot to the solar wind (generally lower energy), for example, but very little to galactic cosmic radiation (a range of energies, including very high energy particles). The primary mitigation for spacecraft in LEO is in fact the large mass shielding them---the Earth.

Quote

A stainless steel starship travelinf for months or a year will get more than the ISS.

Yes, about 2X. Estimates for a 6 month trip to Mars are about 300 mSv, which is about 2 times the same stay on ISS (~160 mSv/6mo).

Quote

I may not be an expert on rocketry like some here, but I do know stuff across,a wide array of subjects. As a writer it was required.

Not apparently on this subject.

The trick with this subject is that even small amounts of shielding (like the skin of a spacecraft) deal with low energy solar radiation pretty well. The particles we care about are the big, really fast ones. These are not deflected much by magnetic fields, and when they hit something, they basically explode into a shower of daughter particles. This happens with dense spacecraft skins (metals), so that every GCR event on the skin is multiplied... it's like breaking in the game of pool. The rack is part of the skin of the spacecraft, and the cue ball is the GCR. Starts out in space (rack intact), hits the skin, then everything is downrange in a shower. That's why shielding is difficult, generally it has to be thick, generally, so that the spalled daughter particles can lose energy and not shower the interior. In the case of Earth, it's the atmosphere that does the heavy lifting vs GCR for those of us on the ground.

The real problem with a Mars mission is that you get the dose for the duration of travel at 2X LEO levels, then you get slightly worse than LEO forever once at Mars, since Mars has no magnetic field to even deflect solar protons, and the atmosphere is pretty useless at mitigating GCR. So on the surface you are back to 300+ mSv/yr unless you live under ground. Reasonable strategies seem to be to shorten the trip to and fro, and to bury the habitats on the surface.

Edited October 3, 2019 by tater

[Spacescifi]

4 minutes ago, tater said:

The Earth's magnetic field is only an issue for lower energy particles. It does a lot to the solar wind (generally lower energy), for example, but very little to galactic cosmic radiation (a range of energies, including very high energy particles). The primary mitigation for spacecraft in LEO is in fact the large mass shielding them---the Earth.

Yes, about 2X. Estimates for a 6 month trip to Mars are about 300 mSv, which is about 2 times the same stay on ISS (~160 mSv/6mo).

Not apparently on this subject.

The trick with this subject is that even small amounts of shielding (like the skin of a spacecraft) deal with low energy solar radiation pretty well. The particles we care about are the big, really fast ones. These are not deflected much by magnetic fields, and when they hit something, they basically explode into a shower of daughter particles. This happens with dense spacecraft skins (metals), so that every GCR event on the skin is multiplied... it's like breaking in the game of pool. The rack is part of the skin of the spacecraft, and the cue ball is the GCR. Starts out in space (rack intact), hits the skin, then everything is downrange in a shower. That's why shielding is difficult, generally it has to be thick, generally, so that the spalled daughter particles can lose energy and not shower the interior. In the case of Earth, it's the atmosphere that does the heavy lifting vs GCR for those of us on the ground.

 

Not really sure what you mean by earth being a shield.

For those living on it yeah, the sheer mass of air and the magnetic field do wonders.

But the ISS is in virtually vacuum, with only the magnetic field around it.

 

As for the thick shielding, the material used effects what kind of radiation is absorbed.

 

At any rate, if the crew encounter any of these rays that pass through the ship, it won't do them any favors.

I read somewhere that six feet thick of concrete would block all those cosmic rays... but trying to launch that would require a bunch of cosmic rays... hello project Orion again .

[kerbiloid]

5 minutes ago, Spacescifi said:

earth being a shield.

It absorbs exactly one half of the rays. Because ISS is crawling right above its surface, and the Earth occupies a whole hemisphere.

5 minutes ago, Spacescifi said:

six feet thick of concrete would block all those cosmic rays... but trying to launch that

means that the simple hull architecture is useless.
Human modules of the ship should be surrounded by unhuman modules and modules rarely visited. A bunch of cylinders, or/and coaxial cylinders.

Edited October 3, 2019 by kerbiloid

[Shpaget]

1 hour ago, kerbiloid said:

If they take a library, the 20 cm layer of cellulose will be an additional 20 g/cm² protection.

Do like the books, they're your friends!

Do the books come with a label "Warning! Reading this book may expose you to Cosmic Radiation, which is known to the State of California to cause cancer, birth defects and other reproductive harm."

You know, because you removed part of the shielding.

[YNM]

4 hours ago, Spacescifi said:

But won't steel react with the cosmic ray particles in space and do damage to the crew?

Won't any material do that ?

[kerbiloid]

6 minutes ago, Shpaget said:

Do the books come with a label "Warning! Reading this book may expose you to Cosmic Radiation, which is known to the State of California to cause cancer, birth defects and other reproductive harm."

You know, because you removed part of the shielding.

This will teach the people to return the books in time.

[Spacescifi]

6 minutes ago, YNM said:

Won't any material do that ?

 

Some materials (it depends) will lead to more deadly scattering of cosmic rays than others. It's a complex subject.

[kerbiloid]

2 minutes ago, Spacescifi said:

 

Some materials (it depends) will lead to more deadly scattering of cosmic rays than others. It's a complex subject.

A human body doesn't scatter cosmic rays more effectively than the steel hull, but this doesn't make the life easier.

Edited October 3, 2019 by kerbiloid

[tater]

14 minutes ago, Spacescifi said:

 

Not really sure what you mean by earth being a shield.

For those living on it yeah, the sheer mass of air and the magnetic field do wonders.

But the ISS is in virtually vacuum, with only the magnetic field around it.

As @kerbiloid said, when you are on ISS, you are skimming barely above Earth. 50% of the sky is rock (with a thin atmosphere as well, but the diameter of the Earth as solid material, you're protected. The same is true for the Moon, or Mars. Once landed (or in a low orbit), your exposure drops by a factor of ~2.

ISS skims barely above the Earth, the view is much more like being in an aircraft than it is like the view the Apollo astronauts had of the Earth as a ball.

 

Quote

As for the thick shielding, the material used effects what kind of radiation is absorbed.

The radiation we are concerned about is mostly galactic cosmic rays. Generally, it needs to be really thick (lunar or martian soil has to be meters thick), or hydrogen rich.

Quote

At any rate, if the crew encounter any of these rays that pass through the ship, it won't do them any favors.

The particles either hit the hull, spall, and shower the astronauts with nasty daughter particles, or they hit the astronaut. Shielding either needs to literally be meters thick (even if it's tanks filled with water), or it basically does nothing.

Quote

I read somewhere that six feet thick of concrete would block all those cosmic rays... but trying to launch that would require a bunch of cosmic rays... hello project Orion again .

Yeah, concrete is about like soils.

 

[Spacescifi]

4 minutes ago, kerbiloid said:

A human body doesn't scatter cosmic rays more effectively than the steel hull, but this doesn't make the life easier.

 

I was talking about the shield between the cosmic ray and the human body.

I also think you knew that.

Hydrogen I have read tends to absorb/block radiation well.

EDIT:

Ditto what he said.

 

Edited October 3, 2019 by Spacescifi

[tater]

5 minutes ago, Spacescifi said:

Some materials (it depends) will lead to more deadly scattering of cosmic rays than others. It's a complex subject.

Some are better, mostly hydrogen-rich plastics. Still, they need to be thick. One concept is putting the hab inside propellant tanks (or surrounded by them)---and hydrogen is a good propellant (though a PITA to deal with).

Pretty much all the outsides of spacecraft are gonna be not so great. Plastic has other issues.

Also, your hydrogen fuel boils off or gets used as propellant, so eventually you have little left.

[Spacescifi]

3 minutes ago, tater said:

Some are better, mostly hydrogen-rich plastics. Still, they need to be thick. One concept is putting the hab inside propellant tanks (or surrounded by them)---and hydrogen is a good propellant (though a PITA to deal with).

Pretty much all the outsides of spacecraft are gonna be not so great. Plastic has other issues.

 

So if we ever get metallic hydtogen it would make great... if expensive to make shielding?

 

EDIT: Or perhaps not? Metals and cosmic rays tend to scatter well.

Edited October 3, 2019 by Spacescifi

[Scotius]

1 hour ago, tater said:

Some are better, mostly hydrogen-rich plastics. Still, they need to be thick. One concept is putting the hab inside propellant tanks (or surrounded by them)---and hydrogen is a good propellant (though a PITA to deal with).

Pretty much all the outsides of spacecraft are gonna be not so great. Plastic has other issues.

Also, your hydrogen fuel boils off or gets used as propellant, so eventually you have little left.

Dihydrogen monoxide 2\3 of it is hydrogen after all.

[Shpaget]

4 minutes ago, Scotius said:

Dihydrogen monoxide 2\3 of it is hydrogen after all.

It's also one of the best sources of drinkable water we know of. It doubles as decent precursor for exceptional fuel, cleaning agent and plethira of other uses.

[kerbiloid]

C₂H₅OH contains more H per mass than H₂O and is still consumable.

Also we can have a 38% (nominal - 40%) solution of them for better balance.