Makes more sense than my idea.

A tank-condom?!?

You remind me of a story I heard once about SpaceLab, in which serious thought was given to launching the station flooded with Liquid oxygen and then refitting the empty “tank” in orbit as a station. SpaceLab was just a big aluminum can, after all.

I wonder if a scheme like this would work to lift sections of a large station or vehicle, where the “launch vehicle” sacrifices all payload to internal bulkheads and airlocks. The soap, spam, and toilet paper get sent up on separate cargo vehicles before or after. This gives you an easy way to deliver engines to orbit, too. Just put them to work on the way up and switch nozzles for vacuum work.

Useful for really big habitats in deep space, but not for an early orbital station. Never mind.

This is really very simple, it’s the principle of not leaving your crap in orbit. You put a satellite in space, you leave enough deltav in the tank to move it out of the road.

Some people are seriously worried about loose insulation, which makes it a problem of potential liability even if it is a non-problem problem. At orbital velocities a gram of foam can have the impact energy of a 50 caliber bullet. Somebody loses a solar array and blames it on our carelessness, it could be a legal problem even with no proof at all.

I seem to recall that the water drop inflation was in the Echo program. While used tank modules or upper stages may not be good for reuse as depots or living quarters, solving individual problems can change the usefulness and value of various commodities.

Thanks for the welcome back everybody. My circumstances are actually better than a few months ago.

Micro meteoroid holes might be an issue with regards inflation, though it would add significant extra shielding. One possibility is to leave the front fully open – like a big bag, and use ram air inflation to keep it inflated – have that drag work for you.

I wonder at what orbital height it would become viable to also use this for atmosphere skimming – vacuum pump plus high ISP drive to keep it in orbit.

I’ve actually been thinking along these lines, though not of shuttle-ET tankage but the concept of “modular” tankage that can be “re-purposed” on-orbit.

I began thinking even more seriously about it once I read Jon’s posting on his thoughts on RLVs. I finally realized there seems to be a slight ‘disconnect’ in the thinking that an RLV has to be COMPLETLY reusable and by that it is meant that everything HAS to come back “home” to be refurbished and readied for the next flight.

“Anything” else is considered an “ELV” with an RLV component and therefor NOT a “real” RLV. If your don’t bring it “home” then the part is “expended” and useless. But that’s a PERCEPTION problem associated with the (sometimes seemingly eternal ) argument between ELV and RLV concepts.

Jon himself commented that he could see “very few” situations where a seperate “compartment” for payload would be economical on an RLV. Specifically he was thinking of a fully self-capable reentry and landing vehicle attached to an RLV orbiter/lander.
I got and still have the “feeling” that Jon neglected one very important “P” in his listing of “people, propellant, and provisions” because I suppose I’m of the firm belief that “place” is going to be a major factor in orbital travel.

Jon and Rodrick Reilly discussed the concept of “drop-tanks” and I’ll take a second here to relay that “dropping” things off your vehicle during take off (or anywhere in flight short of orbit) tends to reduce be seen as reducing your E-sub-C due to the assumption that the items you dropped will fall willy-nilly along your flight path.

Speaking as a 15 year verteran of building, storing, assembling, and using guided munitions if various types I’m quite confident that the technology is well in hand to have any “dropped” objects guided quite accuratly to a designated landing zone with extremly high realiabilabilty for recovery and re-use. There are off-the-shelf RC airplanes that can be programed to fly to specified points using an on-board GPS system for crying out loud!

Back to my original subject: The concept of using “drop-tanks” has appeared numerous times for RLV launch concepts usually to allow ‘fudging’ of the vehicle mass-ratio to allow it to achieve orbit. Some of the concepts dropped the tank(s) as early as possible once they became empty, but a majority seem to have kept the tanks almost till they reached orbit to allow maximum payload to orbit. Dropping the tanks short of orbit achieves two tasks; one it achieves a higher payload to orbit since the orbital vehicle only has to use a small amount of propellant to ‘finish’ reaching orbit without the drag of the tank mass, two it ensures the dropped tank is destroyed so as not to add orbital debris.

The idea of taking the tanks all the way to orbit to be ‘re-used’ though it has come up again and again runs into several “real-world” problems though. For one thing it reduces the payload to orbit of your launch vehicle concept and while the penalty may not be ‘much’ on larger vehicles such as the Shuttle the effect hurts a lot more on smaller vehicles. You also run into the issue that a “good” fuel tank does not usually translate well into even an ‘adequate’ habitat or laboratory module on-orbit unless one can do a lot of on-orbit labor to re-purpose the module. Lack of adequate space suits designed to actually be used for labor in space make this a daunting if not impossible task. I’ll finish with a most major issue; there is no demand or need for on-orbit modular tankage that is going to take effort and probably expense to convert to usable storage, habitat, vehicles, etc.

All of these ‘problems’ are solvable, and with proper design of the tank ‘modules’ I believe that a launch program that includes such designs will have huge advantages in flexability and economics. But then again, I could be all wet and having a fever dream )

(As a note, my “insperation” for this combines the original InterOrbital Systems 1.5 stage to orbit launch vehicle/space station, a now non-op website on modular construction which had paper .pdfs that you could build of the various modular pieces {http://www.geocities.com/codex34/paper/pdf2/pdf.html and if anyone can get me the name of the author of those pages I’d appreciate giving credit where credit is due} and many suggestions and ideas from folks that frequent this and other blogs and cyber space. Thanks )

Randy