Strategy for mining asteroids, part XIII

**Previous post here**
Let's consider a possible new configuration for a space hab that may lead to less mass, but better protection from space hazards.

First, let's consider a sphere for a space hab. It would be made of iron with 10 cm thickness giving 93% protection against cosmic radiation.

The calculations of mass:

Volume of a sphere equals 4/3 pi r cubed

For r=3 meters, or 6 meters in diameter, meaning 6*3.25 feet or almost 20 feet.

4/3* 3.14 * 27= 113 cubic meters.

Now, a 10 cm thick shell would decrease volume by:

6 meters - 20 cm --- 10 cm on each side

This means 5.8 meters diameter or 2.9 meters radius. Calculations give 102, or 11 cubic meters less volume, which is accounting for the shell. Now, to account for its mass:

cubic meter of iron is 7.874 g·cm−3 density * 100*100* 100 equals

7874000 gms or 7874 kg, or 17323 lbs.

For this much mass, you will have 93% protection against cosmic radiation, but you won't have much living space. To expand the living space, include an outer shell of graphene. The graphene shell could be a cube, which could be of arbitrary size because its mass would be so small. Inside the volume, we only have the mass of the air inside. This amount of mass is trivial, but it could render the occupants some wandering about room. Perhaps you could spin up this thing and give some artificial gravity. Crew members could go to the edges and get some exposure to artificial gravity for awhile each day. Then, retreat back into the sphere in order to reduce their expose to cosmic radiation as the graphene would not provide protection from that.

You could have more internal space than a Bigelow space hab, and more cosmic radiation protection, while weighing less.

The less the mass, the better for a low-thrust propulsion method like a solar sail.

As the space sail is constructed in space, so could the proposed space hab. You could use materials from a captured asteroid.

**Update**:

Oops! I forgot to multiply the cubic meter of iron by 11. It does make a difference. Never mind!

Perhaps you shouldn't use iron. Or so much of it.

I considered a "coffin" arrangement. One big enough for one person times the number of people aboard.

Consider a coffin 2 meters long by 1 meter wide by 1/2 meter depth.

It would have 6 sides. 2 sides would be 2 by 1 equal 4 sq m

2 sides would be 1 by 1/2 equal 1 sq m

2 sides would be 2 by 1/2 equal 2 sq m

or a total of 7 sq meter

1/10th of that would add up to .7 cubic meter, or 12126 lbs each

You could spin up the coffins inside the big area enclosed by the graphene.

Not as good as I once thought, but you still get your 93% protection.

**Update**:

Reading some stuff on

radiation protection. Got an idea on using

pykrete, which is sawdust mixed in ice. This creates a very tough material that could be used in more than one way for life support. As a water source and as radiation shielding. Plus an added benefit of structural strength.

You have to keep it frozen though. Then that creates a problem if you want to stay warm. Surround it with thermal protection tiles like the Shuttle, which may do the trick. You keep the heat from it, and the cold inside.

Looks like you have a comparable amount of radiation protection, but you also have the use of the water.

**Update**:

Looking at that chart again... Let's say you make a cube 1000 ft cubed. At that size, the graphene shell would still weigh very little and the amount of air could add the same as 1 half thickness of shielding. In other words, the life support system would also serve as a shield. ( but not all of it ) You'd have to really sure that you have airtight seals for such a large structure.

**Update**:

One more time with this. Using lead, you can make the sphere that I started off with. It would mass at about 25k pounds. Now, if that sphere were to be reinforced with graphene, it would be tough. But tough enough?

Let's say the big cube mentioned above covers up the sphere. The graphene shell would have the Shuttle's tiles all around it if mass limits permitted. The purpose of the tiles would be two fold--- to protect against meteorites and to thermally protect a layer of pycrete, which gives toughness to the shell.

Now, if you can do all that for less than 25k pounds, that gives 50k pounds for the habitat so far. With 75% protection.

Then add the coffins to the sphere to finish off the protection at 93%. The coffins would not have to be as heavy as above. Maybe only 1/5 as heavy. That would be about 5k pounds. Now we are up to 55k pounds.

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