The space island group

[Bill Phil]

1 minute ago, Nibb31 said:

You wouldn't outfit the tank. You would need to design a whole new stage. As mentioned, it would need internal insulation, or several tons of coating on the outside to prevent shedding foam. On the inside, you would need airlocks between the tanks, and some sort of docking device. It would need station-keeping if you want to dock to it, which means power (solar panels), avionics, RCS, navigation, comms...  You probably wouldn't want live directly inside a tank that has been filled with H2, LOX and helium, and the coatings on the inside of the tank wouldn't be very pleasant, so you would probably need some sort of inflatable bladder to fill the tank with a breathable atmosphere and serve as liner/padding. Then you would need to install the wiring, fluid loops, air ducts, assemble walls and floors and install the equipment...

The whole outfitting job would probably take months or years of EVA and IVA assembly, and many delivery flights to bring up the equipment.

Having a large empty volume isn't nearly as valuable as some people think. It's what you put inside that volume that matters. In the end, it's much cheaper to build your habitat on the ground and have it operational immediately for orbital work.

Unless we're using the tank to store more propellant. 

[Nibb31]

1 minute ago, Bill Phil said:

Unless we're using the tank to store more propellant. 

Assuming there is a need to store propellant in anything else than whatever it came up in...  In most cases, there isn't. You would send up "tankers" as needed and dispose of them when empty. Or you could just deliver disposable tanks with a reusable tug. Or if you have a big large ship that needs multiple tankers, then it would simply be its own propellant depot.

It will be a long time before there is a need for a multi-purpose propellant depot.

[Emperor of the Titan Squid]

1 hour ago, Nibb31 said:

You wouldn't outfit the tank. You would need to design a whole new stage. As mentioned, it would need internal insulation, or several tons of coating on the outside to prevent shedding foam. On the inside, you would need airlocks between the tanks, and some sort of docking device. It would need station-keeping if you want to dock to it, which means power (solar panels), avionics, RCS, navigation, comms...  You probably wouldn't want live directly inside a tank that has been filled with H2, LOX and helium, and the coatings on the inside of the tank wouldn't be very pleasant, so you would probably need some sort of inflatable bladder to fill the tank with a breathable atmosphere and serve as liner/padding. Then you would need to install the wiring, fluid loops, air ducts, assemble walls and floors and install the equipment...

The whole outfitting job would probably take months or years of EVA and IVA assembly, and many delivery flights to bring up the equipment.

Having a large empty volume isn't nearly as valuable as some people think. It's what you put inside that volume that matters. In the end, it's much cheaper to build your habitat on the ground and have it operational immediately for orbital work.

This makes it seem very impractical. Is there anything we can do to solve these problems?

[Nibb31]

40 minutes ago, Emperor of the Titan Squid said:

This makes it seem very impractical. Is there anything we can do to solve these problems?

Yes, abandon the idea. Which is exactly what NASA did with Skylab.

[Bill Phil]

3 hours ago, Nibb31 said:

Assuming there is a need to store propellant in anything else than whatever it came up in...  In most cases, there isn't. You would send up "tankers" as needed and dispose of them when empty. Or you could just deliver disposable tanks with a reusable tug. Or if you have a big large ship that needs multiple tankers, then it would simply be its own propellant depot.

It will be a long time before there is a need for a multi-purpose propellant depot.

There are some very obvious benefits to having propellant depots, and there are more subtle issues that crop up when you scrutinize them closely. 

Why dispose of the tankers? You spent the money putting the mass there, why waste it? 

Propellant depots allow you to get away with larger missions when you have a much smaller spacecraft/mass ratio. Of course, tankers would be useful as well, but it takes more energy to send out a propellant tank than to rendezvous with one (if they were ubiquitous). And if you're low on Dv, it'd still make more sense in some cases to send out a "tow truck," and a tanker in other cases. In all likelihood both will eventually be fairly ubiquitous.

As a very imperfect analogy: Would you rather have gas stations or on call gas delivery vehicles? With cars, transporting gas is easy, so having on call gas trucks would be doable(with its own caveats), however, spacecraft aren't so lucky in that regard.

1 hour ago, Nibb31 said:

Yes, abandon the idea. Which is exactly what NASA did with Skylab.

The motivation behind the dry workshop version of Skylab was the freeing up of various Saturn Vs as the result of cancelled Apollo missions, since there weren't going to be any new runs of Saturns.

Much of the equipment to convert the S-IVB to the workshop could've been launched with the stage as payload. It would've been much less capable than the dry workshop, though. And it would've taken much of the time of the first crew (and likely the second) to set up. But the dry workshop suffered some of that regardless.

They would've done it if they had too. 

If you want to avoid the hassle you'd account for that use from the beginning and make it easier to do. Still not as good as a dry workshop, but with no heavy lifters you'd just have to make do.

[Emperor of the Titan Squid]

1 hour ago, Nibb31 said:

Yes, abandon the idea. Which is exactly what NASA did with Skylab.

This is hypothetical. I want to try to figure out what could be done, we're not trying to do this for real.

[Nibb31]

 

13 hours ago, Bill Phil said:

As a very imperfect analogy: Would you rather have gas stations or on call gas delivery vehicles? With cars, transporting gas is easy, so having on call gas trucks would be doable(with its own caveats), however, spacecraft aren't so lucky in that regard.

Bad analogy, because a single tanker truck can fill up hundreds of cars. It makes sense to build a gas station to service thousands of cars. In space, you need several tankers to fill up your car for each journey. So you might as well just park your car and use it as a fuel depot.

 

[DerekL1963]

On 9/3/2016 at 3:34 PM, magnemoe said:

An vasmir might work well, you don't want to stay to long in the van allen belt so you want decent trust, 

VASMIR doesn't have sufficient thrust to even put itself (let alone it's power supply, fuel, plus any cargo) on a trajectory that won't spends weeks or months in the Van Allen belts.
 

[Bill Phil]

10 hours ago, Nibb31 said:

 

Bad analogy, because a single tanker truck can fill up hundreds of cars. It makes sense to build a gas station to service thousands of cars. In space, you need several tankers to fill up your car for each journey. So you might as well just park your car and use it as a fuel depot.

 

Yeah, that's why I said that spacecraft aren't so lucky in that regard.

A single *tanker* truck. I was not referring to tanker trucks, but smaller trucks with gas tanks. Not a full blown tanker truck.

[magnemoe]

Related to fuel storage in space.
http://www.nextbigfuture.com/2016/09/nasa-niac-cryogenic-surface-materials.html
Looks like this paint would keep an tank with oxygen or methane liquid with no complex shadow shields or cooling. 

[Emperor of the Titan Squid]

On September 7, 2016 at 1:09 PM, magnemoe said:

Related to fuel storage in space.
http://www.nextbigfuture.com/2016/09/nasa-niac-cryogenic-surface-materials.html
Looks like this paint would keep an tank with oxygen or methane liquid with no complex shadow shields or cooling. 

That's interesting. But the thread is supposed to,discuss wet workshops, and how we could build the one.

[magnemoe]

5 minutes ago, Emperor of the Titan Squid said:

That's interesting. But the thread is supposed to,discuss wet workshops, and how we could build the one.

Current discussion is mostly about orbital fuel depots not wet workshop. 

 

On 5.9.2016 at 9:05 PM, Nibb31 said:

Assuming there is a need to store propellant in anything else than whatever it came up in...  In most cases, there isn't. You would send up "tankers" as needed and dispose of them when empty. Or you could just deliver disposable tanks with a reusable tug. Or if you have a big large ship that needs multiple tankers, then it would simply be its own propellant depot.

It will be a long time before there is a need for a multi-purpose propellant depot.

I agree here, Say you want to do an Falcon heavy Moon mission you would then use an extended upper stage and extra launches to fill it. You would want some storage to avoid boiloff because of delays and orbital matching.
For an long term multipurpose depot you would need ISRU from Moon or astroids. 
 

[Emperor of the Titan Squid]

On September 5, 2016 at 3:05 PM, Nibb31 said:

Assuming there is a need to store propellant in anything else than whatever it came up in...  In most cases, there isn't. You would send up "tankers" as needed and dispose of them when empty. Or you could just deliver disposable tanks with a reusable tug. Or if you have a big large ship that needs multiple tankers, then it would simply be its own propellant depot.

It will be a long time before there is a need for a multi-purpose propellant depot.

A propellant depot could be useful at l1 or l2 if we had a lunox setup. However, we won't have that for a while either.

[Emperor of the Titan Squid]

With the unveiling of the spaceX Interplanetary transport system and its booster, I wonder what we could do if we made a wet workshop with the massive booster. Also, what about using the spaceships fuel tanks for habitats on Mars, at 

Least if it's flying one way on that mission.