External Tanks in Orbit

Outfitting an External Tank in Orbit

The space shuttle's External Tank (the LARGE orange fueltank the shuttle is attached to at launch) consists of a hydrogen fueltank and an oxygen tank separated by an "intertank" section. The hydrogen tank is the lower, larger tank measuring 27 ft in diameter by 96 ft long; the intertank section is on top of the hydrogen tank, and measures 27 ft in diameter by 22 ft long; the oxygen tank is mounted to the top of the intertank section, and measures 27 ft in diameter (tapering to its tip) and is 54 ft long. The intertank section separates the two tanks, and distibutes the launch loads, and also serves as the upper mounting points for the space shuttle and solid rocket boosters (which means it's quite strong).

Many space shuttle launches have the capacity to take an ET right into orbit with them (they are currently dumped back into the atmophere after reaching 98 percent of orbital velocity). If we so desired, we could launch an ET and the equipment necessary to outfit it to accomodate 12 people, with just one shuttle launch.

Let me try to walk us through the outfitting of the ET after it reaches orbit:

First the leftover hydrogen and oxygen must be vented from their respective tanks. The easiest and simplist way seems to be to use helium gas, from a tank mounted in the intertank section, to purge the tanks.

After the tanks are purged, an astronaut would open the access hatch on the "bottom" of the hydrogen tank (opening the access hatch and astronauts passing through it in spacesuits has already been demonstrated in NASA's neutral bouyancy facilities). A docking adapter/airlock/propulsion unit would then be attached to the access hatch. All our ET outfitting hardware would be passed through the hatch into the ET's interior (all this would be done while the space shuttle is still attached, for support) and then we would seal it up and fill it with a breathable atmosphere.

Let's go inside and take off our spacesuits.

Once inside we can look down the length of the hydrogen tank. The other end is 96 ft away. Just inside the access hatch a few feet (I don't have the exact measurements right now but I can get them if there's interest) is the tank's main ringframe, which is more or less a circular girder. This main ringframe carries the lower attachments for the shuttle and solid rocket boosters, and the tanks walls are welded to it (and the others). We see this main ringframe protruding into the interior "above" the tank walls about 4 inches, all the way around the 27 ft diameter of the tank, and as you look farther into the tank you see that there are other ringframes at intervals (about 20 ft apart) all the way to the other end of the tank.

Now, we take a 20-ft-long girder (part of our outfitting hardware) and we attach it so it spans the distance between the main ringframe and the next ringframe into the tank. We then take another girder and attach it to the same two ringframes, 180 degrees from the first girder. Both of these girders can be attached to the ringframes without pentrating the outer wall of the tank.

We then take our 27-ft-long, 3-ft-wide flooring material (something similar to Skylab's "grate" flooring) and use it to span the distance between the two girders attached to the ringframes. The flooring attaches to the girders.

Once this is done, the length of the hydrogen tank, we now have a floor 27 ft wide and 90 ft long, right down the middle of the tank (which I like to call the Main Deck), with a "ceiling" 13 ft above the main deck's "floor." You could play basketball or tennis on a floor this size. I once painted a fullscale model of this "Main Deck" on a school playground, and we had all 780 people at the school "inside" the ET at the same time! It's BIG! (The picture is in one of SSI's newsletters. I'll put it on my new website, if I ever get it built:)

This whole process could be duplicated and another "floor" could be installed 8 ft "below" the Main Deck, and "above" for that matter, but my preference would be for a 13 ft "ceiling." And the oxygen tank can be similarly outfitted.

Now how hard would it be to put these basic floors together? Not very. It's just like tinkertoys. A couple of people could do it in a few weeks, especially since they will be working in shirtsleeves and have plenty of room to move around in. And how hard would it be to bolt all your other equipment to this basic deck arrangement. Like the astronaut said, All we have to do is tie our feet down and we can do anything in space.

With two decks in an ET, it would have about three times more laboratory floor space than the international space station.