This one is in response to an ongoing discussion about the pressurized volume in the various deep space exploration architectures. Apparently an Orion will provideÂ sufficient crew volume for extended missions while a Dragon will not in many peoples minds. The suggested often remedy is a Bigalow inflatable module for the extended missions.
Henry Cate has a cheaper and faster solution. The trans-Lunar/Mars/asteroid injection stage has a large hydrogen tank. Add a small header tank to the vehicle to store the residual hydrogen in the main tank and vent that main tank to vacuum. Fill the tank back up with breathable air and dock the Dragon to it as in Apollo/LEM. Requires compatible hatches designed into the tank.
The living volume gained will necessarily be Spartan for the same reasons that Wet Skylab was rejected. It does however provide at least 14 cubic meters of volume for each ton of hydrogen that was carried in the original tank. This in addition to the usable Dragon volume would quickly dwarf that of Orion without the launch or purchase expenseÂ of the inflatable module.
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The people will need cupboard space. Food, water and clothes do not like being stored at cryogenic temperatures.
I’m thinking that in the proposal food, water, etc. would not be stored in the tank while it is carrying liquid hydrogen.
> Iâ€™m thinking that in the proposal food, water, etc. would not be stored in the tank while it is carrying liquid hydrogen.
Although, I suppose, some dense material like that could be packed in the bottom of a purpose-built tank. Might be an interesting exercise to figure that out. Mostly hydrogen, but a layer of beans, tofu, etc. in a compartment at the bottom.
Living space is not storage space. The interesting aspect of this idea is that it adds volume without adding weight (except for 1 kg of air for each extra cubic meter of space, but even that is just air in the space rather than air in a tank). Other than this space, any mission with the same number of crew will require the same amount of consumables, presumably stored in a slightly cramped Dragon capsule.
Plus decorating and setting up quarters in the tank will give the crew something to do during the long trip to Mars!
Neither Dragon or Orion is suitable for a long duration missions (6 to 9 mo.) with a half dozen crew. Bigelow is correct that the BA330 makes the Orion unnecessary. Although the 180m3 Sundancer is closer to the same mass.
The mission profile is integrate a complete vehicle on the ground. Put it in orbit in a single launch. Follow with multiple fuel launches (hydrogen not an option. It is simply a bad choice.) The last launch puts crew on the vehicle. If they are going to land anywhere you send that lander (Dragon) ahead and meet it.
The BA330 provide 55m3 per crew. The Sundancer (assuming it had the same life support for six) would provide a reasonable 30m3 for each. They will each need at least 5m3 for supplies.
Existing launchers could handle this. The Orion is already obsolete.
The emptied tank may provide space, but it would need to be outfitted with lights, fans to move air, electronics, etc. You also need power, cooling/heating, etc. Tanks like this make more sense for space stations.
In this context, the tank is already on its’ way to the same destination as the spacecraft. A few accessories on extension cords to make it useful would seem to be a bargain compared to hauling more dedicated volume.
One of the problems that tanks always encountered as space stations is the drag and reboost requirements on a large empty volume in LEO. YMMV of course. Tanks as space station modules in most cases seem to come off second best to purpose built modules IF there is a requirement for extensive outfitting. Part of the value in the exploration volume concept is that it wouldn’t require many fixtures to be a welcome addition to the living quarters. Think residential living room instead of industrial lab.
The nice thing about a hydrogen tank is venting it would leave no residue (I really have no clue about carbon based fuels but suspect them of leaving some coating even in vacuum?) I also don’t know how long contact with hydrogen takes to make the tank brittle.
The thing that strikes me is this idea is independent of the capsule. You could easily switch out a better choice of vehicle and still use this idea for more volume.
How about one billion in less than ten years to send twelve to mars?
It’s not just SLS we need to cancel. Orion is actually about a third of the entire cost, isn’t it?