Further thoughts on the space hab.
Considering that risks are taken in human spaceflight, would it not be out of the question to seek reductions in mass if such can give an advantage?
Look at the ISS. It doesn't have 93% shielding against gamma radiation. Half of the sky is taken up by the Earth, but the other half has to be shielded, but is not being shielded. The crew members aren't harmed too much by it.
Now, with that in mind, the "coffin" arrangement is revisited. As written earlier:
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
That's 7 square meters of surface area to be protected. If lead is used instead of iron, and only 1 cm of protection is used, the mass would be 7 times .01* 1 million cc in a cubic meter * 11.34 g cc lead equals 794 kg ( 1746. lbs ) lead for 50% shielding. As much shielding as the ISS gets from the Earth.
Now, using a very thin layer of reinforced aluminum for the sphere as was used for the sail itself, you could have a pressurized habitation with 50 % shielding that mass out at a much lower rate. The graphene reinforcement could boost confidence in the strength of the aluminum. Bulk graphene isn't available now, but could be soon. The nearly half inch thick aluminum is also thicker than what the ISS gets, so that means more protection.
The aluminum would weigh in at 5940 lbs per cubic meter. To use all 11 meters as calculated before in the last post would give a 4 inch shell. Not so much thickness this time, so 1/10th of that would be 1 cm. So, a sphere could be constructed at that thickness for 594 *1.1 equals 653 lbs .
The sphere could be spun up for artificial gravity. But that would not be anywhere near 1 g. At 6 RPM, you could get about 0.12 g. For long duration missions, this may be a problem. That's the reason for the minimizing of mass, to keep the mission as short as practical.
Now, for 2 "coffins" and a spherical aluminum habitat, we need only 653 plus 2* 1746 lbs or 4146 lbs for our habitat. For comparison, the lunar ascent module in the Apollo Era massed out at about 5k pounds unfueled. Now, this hab so far doesn't include everything of course. But you can get an idea of how little weight would be necessary for some basic protection.
You may want some meteorite shielding. But that isn't massive. It just needs to be of such nature as to slow down the speed of a meteorite as it strikes the hab. Finally, you need to outfit the hab with equipment.
The goal would be to get the weight down to a minimum for a fast sailing ship. A ship of 17 tons mass can get to Venus in 200 days. Again, for comparison, the total weight at the launch pad for the lunar module in the Apollo Era was about 35 k pounds, or 17 tons. We won't need rocket engines nor fuel for the asteroid mission, as the gravity well of the asteroid is practically nil. The fuel and rockets could be replaced by equipment. Now, the asteroid 3354 Amun ranges between Venus and Earth, so it shouldn't take any longer than a Venus trip, I would guess. Our hab has to be good enough for a couple years at most.
These calculations leaves ample room for equipment and gets us to our destination in a minimized amount of time. We want to be able to mine platinum and bring it back for profit. We don't want to get killed in the process.
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