ET tank, #11

Earlier, I said that it will take 4 ET's to spin up to Martian artificial gravity levels.  There was a discussion in the pdf file that I've been referring to that mentions 6 ET's.

Can we find a way to use the 2 others? I think I know one.  Put one on each side of the center of gravity.

One side could be used for propulsion, the other side for docking.  It could be set up so that it doesn't have friction so that it won't slow down the spin of the station.  Use magnetic field to push it away from the station while it rotates.  You could also use this magnetic field to spin it up and to slow it back down again if you don't want to spin all the time.  The propulsion can be provided by the tank, engine assembly as is.

In order to avoid boil off, keep the propulsion part in a permanent shade.  This should simplify keeping it cold enough so that it won't boil off.

There's another idea that I had.  Use magnetic fields to provide shielding from ionizing radiation in space.  Perhaps spacesuits could be fitted with such devices.  The Earth's magnetic fields provide such shielding on the surface.  Use that principle to make a wearable shield for astronauts.

Update:

If the spacesuits mentioned above can split carbon dioxide into carbon monoxide and oxygen, it could enable longer spacewalks and such.  The oxygen can be recycled continously while collecting and storing the carbon monoxide which can be used later as a fuel.

In the above mention of the permanent shading for the ET, plenty of material can be found inside the tanks which can be used for that purpose.  Thousands of pounds of metals can be recycled for purposes such as this as well as other purposes.  This is "in situ" resource utilization applied to our own spacecraft.  It is the same principle that got Apollo 13 astronauts safely home.  They scavenged materials in order to make a carbon dioxide scrubber.  Without this improvisation, they would have died.