Space Shuttle's External Fuel Tank

Factual Questions
1

I heard a proposal about ten years ago that I thought was ingenius. Someone (on a radio show, I think) suggested that instead of ejecting the huge external tank to burn up in the atmosphere, the shuttle should carry it all the way into orbit. From there it could be sent to rendezvous with the site of the future international space station. I guess a guidance system and some retrorockets could guide the tank to its distination while the shuttle went on with its mission.

I seem to remember that Skylab was little more than a couple rocket stages wielded together. Think of how usefull sixty or so interconnected, roomy, airtight tanks would be for storage or living and work space.

It seems that as long as you have the tank most of the way there, you might as well put it in orbit and make use of it. Does anybody know if this proposal was ever considered? If so, what were the objections to such a plan?

2

Just a WAG but I think it’d take quite a bit of finishing work to turn fuel tanks into living spaces (with the need for life support systems and all). It would also be hard to get rid of all traces of fuesl. They can’t just drag it into the back yard and hose it down. It is ungodly hard and expensive to do actual work in space, especially if one has to go “outside”.

3

I thought they recovered and reused the external tank.

4

TNT is correct. The tanks are recovered and reused.

Also it would take a lot more fuel to get them into orbit.

5

Actually it’s the two solid rockets that are recovered. I’m talking about the big brown tank in the middle. As for removing traces of fuel, I thought all that was in it was liguid oxygen and liquid hydrogen. Exposing the interior of the tank to a vacumn before being occupied should vaporize any fuel that is left. Regardless, I don’t think either is toxic.

6

The extra fuel used to get it all the way into orbit would be a fraction of that needed to lift a space station module all the way from the Earth’s surface. I believe the first couple miles of a trip expends a large portion of the total fuel needed.

7

Hey, that’s a great idea, Ursa. A giant pole barn for the space station. And it’ll give us a woodshed to take those Russians to when they misbehave.

8

I’ll admit that I haven’t seen a Space Shuttle lift off for quite a while (it must be shown live on Cable TV somewhere) and that probably answers my question, but why don’t they sell advertising space on the External Fuel tank? I mean, that could bring in some good advertising revenue (ie. Ram Tough, or True-Valu, or Coca-Cola,)…

Maybe they could earmark that revenue for a mission back to the moon…people might go for that…

Even if I had a signature, I doubt I’d have room for it.

9

I’ve seen the advertising thing before. I think NASA has a specific policy against it. (btw, the Russians did have advertising on the side of at least one of their launches; it was for the move The Last Action Hero).

As for the external tank… The tank currently falls into the atmosphere and breaks/burns up. It is the SRBs that are recovered and reused. I have also seen the proposal to send the tank on up into orbit. The article I read indicated that by doing so they would actually increase the cargo capacity of the shuttle. (Apparently they could carry more fuel if they took the tank all the way up.) There was also a proposal in the article that the tank could be extended by adding a “cargo module” to the bottom of the tank, giving even more cargo capacity. Unfortunately I have no idea as to where I read the article; I think it may have been a science article in Analog but can’t remember for sure. I do know it was a while back that I read it though.

“It turns out it isn’t so much a law of physics as it is a local ordinance.”

10

Instant followup… There was an article last year about Pizza Hut wanting to put billboards in orbit. (!) The link to the article was…
http://www.cnn.com/US/9909/30/pizza.in.space.ap/index.html

…but that link seems to be dead now. I did save one quote from the article which had nothing to do with the space billboards but was amusing nevertheless.

The scary part is, I think they were serious!

“It turns out it isn’t so much a law of physics as it is a local ordinance.”

11

It is a great idea, but NASA has rejected it for a number of reasons, only a few of which I now recall.

To briefly summarize until someone who knows the full story comes along, it goes something like this. First, the shuttle could very likely carry the main tank into orbit, but the orbit would have to be lower, or the payload weight would have to be reduced. Neither of these options were deemed acceptable to NASA.

A second proposal involved putting a small, inexpensive solid rocket onto the main tank, designed to fire after separation from the Orbiter. There are several problems with this proposal. Challenger demonstrated what can happen when a defective solid rocket burns into the main tank. At separation, the main tank is almost empty, but nevertheless is capable of exploding. Detonation of the main tank in low earth orbit could spread debris throughout that valuable orbital path, and could even endanger the Orbiter, either by the explosion itself or by passing through the debris on a later orbit.

Another problem with the “booster” proposal is that you can’t simply tack a rocket on and be done with it. Once you’ve gone to that step, you now need telemetry and guidance, possibly maneuvering rockets, a command and control system, and so on. In other words, you’ve just gone from a big dumb fuel tank to a big elaborate dumb fuel tank that has to be parked in a specific place for later retrieval.

And “elaborate” means “expensive.” Besides the Bureau of Indian Affairs, NASA is one of the most underfunded agencies in the U.S. government, considering what they do. They don’t even want to consider it for fear of diverting resources from other more important projects.

All that being said, the fuel tank to orbit proposal is one of the best unused ideas out there. The problems are not insurmountable. Raw material in space will be one of the most valuable commodities of the spacefaring future, and those giant tanks supply them in abundance. Not only could the tanks supply storage space and emergency spare parts, but the residual fuel remaining in the tanks is the most valuable part of the tank. Comprising of hydrogen and oxygen, the cargo that is currently being burned up over the Indian Ocean could supply propulsive fuel, power, breathable air, and water. When you look at it that way, is it really that difficult?

12

Jerry Pournelle has written several articles on this, and Larry Niven did an essay on this as well. Unfortunately, those books are in my storage room so I can’t give you an accurate citation.

“You can be smart or pleasant. For years I was smart.
I recommend pleasant.”
Elwood P. Dowd

13

David Brin has a short story entitled “Tank Farm Dynamo,” with a dozen (I think) tanks in orbit. They strapped them together into two raft-like structures, guyed a ways apart. Tidal force gives a wee bit of pseudogravity on each “raft.”

One reason fuel goes down with the expendable tank is that burning the tank dry would destroy the very expensive engines. Cutting it close to achieve a bit more boost for the big dumb tank makes the NASA guys nervous.

Sure, I’m all for moderation – as long as it’s not excessive.

14

As for advertising on the moon…

Without an atmosphere, it would be relatively easy to ‘spray-paint’ a big symbol on the moon by just putting a computer-controlled sprayer in the middle of a circle and having it direct some sort of colored particulate. By modulating the ejection speed as it rotates, you could precisely control where the stuff lands. I don’t know how much raw material you’d need, but if it’s fine enough and light enough you could perhaps land a probe that would then draw a large image (like, kilometers in size)in that manner.

In Robert Heinlein’s “The Man Who Sold The Moon” he outlined a similar process, and had the protagonist threaten to sell it to a soft-drink company called “Moca-Cola”.

15

Hmm as I recall Heinleins story, he got Moca cola to pay to not allow any advertising on the moon. They did this because it was impractical to put their logo up their, but it would be practical to put their competitor (6 UP if I recall correctly) up their. It was one of Deloss’s best deals to get paid to do nothing.

PUN

16

In the cartoon “The Tick”, one of the super-villians was going to write his name on the moon. He got as far as “Cha”. You’ll see that there in succeeding episodes. :slight_smile:

It is too clear, and so it is hard to see.

17

And for those who read European comics: Once, the evil criminal scientist Zorglub mastered a project to write “Coca-Cola” on the moon.

Unfortunately, his underlings were trained to communicate in “Zor-language”, which simply consists in reversing the letters (Gnol evil Bulgroz!), so when the full moon appeared, it was advertising “Aloc-Acoc”.

Zorglub (Bulgroz) left his secret base on a bicycle, a broken man.

18

Excuse me, but you’ve missed a very important point as to why the shuttle is so versatile! If the fuel tanks did burn up, do you how overly expensive these missions would?

The fuel tanks are jettisoned once the fuel supply has been exhausted. The tanks fall into the Carribean Sea, I believe, and recovered for refueling.

Are you suggesting people live in simply a bunch of bare-bones, unpurged pressure vessels welded together? Why not just weld together some garbage cans, put that in orbit, and call it a “space station”! Even the Mir is better designed for human living than that! I think our astronauts and scientists deserve better than to live in the equivalent of a flea-bag hotel while working “on assignment”.

“They’re coming to take me away ha-ha, ho-ho, hee-hee, to the funny farm where life is beautiful all the time… :)” - Napoleon IV

19

Sorry for some typos and missing words…I haven’t had my coffee yet!

20

Jinx, the external tank is not recovered. It is carried almost all the way up to the orbit and then thrown into the atmosphere to burn up. If it was that easy to recover something from orbit, why would we need the Shuttle in the first place? You are thinking about the solid rocket boosters which are indeed recovered, and some components are used in build new boosters. They are detached at much lower altitude so no heat shields are necessary for recovery.

However, you are right that a tank with a hatch doesn’t make it a space station module. It is a tempting idea - after all, the tanks are built to withstand more than one atmosphere of outward pressure. But the amount of on-orbit work to make it habitable is just too great.