Author Topic: Expandable rocket tankage  (Read 2143 times)

Online yokem55

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Expandable rocket tankage
« on: 04/04/2016 12:06 AM »
Has anyone ever looked at whether expandable tankage could ever be a thing similar in concept to inflatable space modules?

The general idea is that shipping anything wider than 3.7m gets expensive, but if the rocket body could be made  out of something stretchable, it could be shipped in a contracted state within the 3.7m limit and then inflated or expanded once it got to the launch site to 5m or more. The big issue doing this that I can see is that there likely would need to be some internal structure in the tankage to keep it strong enough for flight which might kill the mass fraction of the vehicle.

Any other problems with this hair-brained concept?

Online Gliderflyer

Re: Expandable rocket tankage
« Reply #1 on: 04/04/2016 12:29 AM »
It isn't that crazy. The original Atlas was essentially a stainless steel balloon and would collapse unless it was kept pressurized. The big issue is that on most rockets one or more of the propellants is cryogenic. There are not a lot of materials that are flexible at cryogenic temperatures and the non-cryo propellant combinations, with a few exceptions, are poisonous and/or corrosive.
I tried it at home

Offline MIKKELH

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Re: Expandable rocket tankage
« Reply #2 on: 04/04/2016 09:44 AM »
Something that I just discovered in researching containment stresses is that for any given material used to contain any given pressurisation, the amount of mass of the material required to contain the pressurised load will be a constant. The only factor changing that constant is shape of the container, with a sphere providing the best performance. Since you have to use a booster to transport the propellant load to space anyway, there is no reason not to simply use a collection of the booster tanks. At most, the best benefit you could get would be to design the booster so that you could detach any structural reinforcement required for launch stresses.

Offline Jim

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Re: Expandable rocket tankage
« Reply #3 on: 04/04/2016 02:19 PM »
Has anyone ever looked at whether expandable tankage could ever be a thing similar in concept to inflatable space modules?

The general idea is that shipping anything wider than 3.7m gets expensive, but if the rocket body could be made  out of something stretchable, it could be shipped in a contracted state within the 3.7m limit and then inflated or expanded once it got to the launch site to 5m or more. The big issue doing this that I can see is that there likely would need to be some internal structure in the tankage to keep it strong enough for flight which might kill the mass fraction of the vehicle.

Any other problems with this hair-brained concept?

Inflatables space modules don't see flight loads, cryogenic properties, fluid loads, etc that are experienced on launch vehicle.
« Last Edit: 04/04/2016 02:19 PM by Jim »

Offline Jim

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Re: Expandable rocket tankage
« Reply #4 on: 04/04/2016 02:21 PM »
It isn't that crazy. The original Atlas was essentially a stainless steel balloon and would collapse unless it was kept pressurized.

No, Atlas did not expand or contract.  It was the same size.  Big difference

Offline sevenperforce

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Re: Expandable rocket tankage
« Reply #5 on: 04/04/2016 03:21 PM »
It isn't that crazy. The original Atlas was essentially a stainless steel balloon and would collapse unless it was kept pressurized.

No, Atlas did not expand or contract.  It was the same size.  Big difference
I think Gliderflyer's point was that it's not too hairbrained to have a tank which derives its support from being under pressure.

Online QuantumG

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Re: Expandable rocket tankage
« Reply #6 on: 04/04/2016 10:46 PM »
I honestly can't remember where I read about "inflatable tanks" as you've described, but the assumption was that you'd be making them in space and filling them with propellant there. The g-forces of the burn would indeed crush the tank, but the idea is that these are "drop" tanks.



I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline RanulfC

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Re: Expandable rocket tankage
« Reply #7 on: 04/05/2016 09:49 PM »
I honestly can't remember where I read about "inflatable tanks" as you've described, but the assumption was that you'd be making them in space and filling them with propellant there. The g-forces of the burn would indeed crush the tank, but the idea is that these are "drop" tanks.

WVB used them in the Mars Project among others :) Literally bags inflated with propellant in them, but they needed external supports to keep them from shifting/bursting under acceleration. It was all lighter than actual pressure tanks but not as much as you might think. (And funny enough he was one of the people who doubted that "pressure supported" tankage like the Atlas or "balloon-tanks" like the Centaur were workable. Once he was convinced no one else could "dent" his enthusiasm for the concept but it also wasn't the direction his own work was going)

It isn't that crazy. The original Atlas was essentially a stainless steel balloon and would collapse unless it was kept pressurized.

No, Atlas did not expand or contract.  It was the same size.  Big difference

Not a "balloon" no, but lose pressure and it collapsed like a house of cards, (or a crushed soda can) we have pictures around here someplace of one that did so :)

Pressure supported rather than a balloon is probably more accurate.

Any other problems with this hair-brained concept?

Not really hair-brained as much as not required I'd think. If you really need to move something big there are ways and its only expensive if you don't do it a lot. Cost comes down with use it always does.

I've always wondered if you could use "inflatable" material in a deflated state as insulation on the exterior of a propellant tank. Once on orbit you inflate it and use the empty propellant tank as the 'strongback' system for the module. I can think of around a half dozen "issues" with the idea off the top of my head but none of em seem to be showstoppers... Other than why anyone would want to do so that is :)

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Offline Asteroza

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Re: Expandable rocket tankage
« Reply #8 on: 04/06/2016 12:11 AM »
I suppose a distinction might be necessary for low thrust and high thrust scenarios. Low thrust could potentially have a tractor thrustor system with a tensegrity structure spine, with propellant bags anchored in all directions but primarily expecting a hanging mode like a waterballoon dangling from the fill neck.


There is the interesting sub-issue of how to properly fold insulation for a collapsible propellant bag. Could one do some sort of dewar style multi-bag setup where the inner bag is held in place by cables/nets like a tensegrity structure, to reduce thermal paths? Though to keep the gap space in vacuum, one would need to build up the outer bag more like the Michellin Man using a fabric of hoop tubes that are lightly pressurized/rigidized.

Offline MIKKELH

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Re: Expandable rocket tankage
« Reply #9 on: 04/06/2016 05:19 PM »
I honestly can't remember where I read about "inflatable tanks" as you've described, but the assumption was that you'd be making them in space and filling them with propellant there. The g-forces of the burn would indeed crush the tank, but the idea is that these are "drop" tanks.
Okay... The big question is, why?
Inflatable tanks are not going to save mass. The mass will be dependent upon the material strength... An inflatable material is not necessarily going to have a lower mass.
A collapsed inflatable tank will save space, but, again, why? I can see filling the tanks in space, but watever you put in those tanks will have to be transported there first anyway. You are not going to save space if you need that space to transport the substance in the first place. So, perhaps the idea is that you want to transfer the sibstance (propellant or otherwise) from the launchworthy tank to one that would not survive launch stresses. Okay, but your inflatable tank is probably going to be quite expensive to build. It would be cheaper to design propellant tanks and bulk transport tanks with an outer shell meant to absorb all the flight stresses, and an internal pressure sleeve that can be simply pulled out of the flight sleeve. The pressure sleeve will only be strong enough to contain the pressure. It will be inserted at assembly, filled prior to launch, removed in orbit, and the structural support sleeve will be returned to Earth for the next mission. They pressure sleeve would be easily adaptable to any kind of exterior sleeve to suit specific needs, such as operations from the moon or from Mars.

Online docmordrid

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Re: Expandable rocket tankage
« Reply #10 on: 04/10/2016 04:37 AM »
Thin Red Line Aerospace, who built restraint layers for Bigelow, has listed as one of their projects the Lightweight Inflatable Cryogenic Tank,

http://www.thin-red-line.com/projects.html

Quote
NASA Kennedy Space Center

Teamed with Technology Applications Inc., Thin Red Lines inflatable UHPV technology is investigated as powerful alternative to cryogenic COPVs. UHPVs extreme simplicity permits incorporation of a much broader spectrum of corrosive content (LOX, LH2, LCH4, etc.) compatible liner materials. For propellant depots UHPV can be packaged for launch, filled in-situ, and repeatedly depleted to almost zero residual.
« Last Edit: 04/10/2016 04:38 AM by docmordrid »
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