Orbital Gas Stations

[keermalec]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;I would think low orbits for a fixed Platform in both lunar and Martian orbit makes more sense. It has to be cheaper to carry propellant rather then the whole assembly every trip. Once going to far-flung orbits is established the moon, Mars, asteroids or Comets are just further flung orbits. I would have dedicated lander/ascender vehicles that just went down and back up, refueling in orbit and going back down. Propellant on the surface could also be used, but water will probably be needed in large quantities anyway, just for protection and life support. &nbsp; <br />Posted by scottb50</DIV><br /><br />Absolutely right: landers have a higher inert mass fraction (ie non-propellant) than regular space vehicles (landing gear, extra structure). Therefore one should strive to reduce their delta-v budget by as much as possible, and refuelling in low orbit makes absolute sense. Now the technical issue of how to take off without a flame pit poses itself: the Apollo landers used their landing stage as take-off platforms. A fully re-usable lander/launcher will have to be one-piece. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[scottb50]

<p>&nbsp;A fully re-usable lander/launcher will have to be one-piece. <br /> Posted by keermalec</p><p>&nbsp;</p><p>I was thinking a prepared landing area and engines mounted fairly high on the side of the Modules. A skid type landing gear would be all you need.</p> <div class="Discussion_UserSignature"> </div>

 

[wtrix]

Old subject revialized.

As the refueling is on the table again (mentioned some times in Augustine commission report), I found myself wondering what are the options. AFAIK there are 2 of them:
1. Pump station in orbit
2. Spare tanks for assembly in orbit

I personally like more the later option because managing solid objects in zero g is far easier than pumping liquids.

For me it seems tha launching more and smaller vehicles (with space assembly and refueling) makes more sense than launching some seldom super-duper heavy lifters like Ares V (188 ton behemoth). This way the rockets can be assembled on assembly line (like russians do) and launch pads get better utilized. Thus the capital costs would be a lot smaller. Remember that everything that you make in series production gets cheap.

 

[tanstaafl76]

Semi-permanent orbiting refueling stations seem like an overly complex and problematic design. I would think modular fuel pods would be more effective. Here is my thinking:

1) Semi-permanent orbital refueling depot.
So in order for this to work, you have to first launch the depot into orbit, potentially in pieces, and potentially having to do orbital construction to complete it. Sounds expensive and difficult. Then when it's complete, you have to fill it up with fuel, requiring you to launch spacecraft full of extra fuel that have the capability to successfully rendezvous with it and have fuel transfer capability to put the fuel in. Then when you launch a vehicle that needs to use the depot for refueling, it has to pump it back out. The whole thing seems very complicated. Then what if something goes wrong with your refueling rig when it's full of propellant? You just spent lots of money filling it up with extra propellant, and now you can't even get to it. You may even have to expel it all in order to perform repairs. Talk about all your eggs in one basket...

2) Modular fuel pods.
What if we deposited a series of modular fuel pods into orbit, potentially using a series of inflatable Bigelow-style designs. Instead of being filled with air, they would be filled with fuel. Then your follow up spacecraft that needs refueling meets up with the pod, and utilizes vacuum pressure to suck the fuel out of the pod, which would then deflate.

It seems like the simplicity of option 2 would result in a much less costly and straightforward process. If anything goes wrong with an orbital fuel pod, instead of being forced to conduct costly orbital repairs you always have the option of just launching another one instead.

 

[wtrix]

I imagine it to be more like a station that aquires filled fuel tanks launched from earth, stores them and attatches them later to the departing space vessel. Many small rockets is cheaper than few big ones if the productionis changed accordingly.

This needs:
1. A storage rack
2. Orientation system
3. Some limited ability to change orbits
4. Robotic hand specialized for managing heavy fuel tanks
5. Some way to cath tumbling and spinning fuel tanks

Plus solar batteries, cpu-s, heaters, coolers, communication and other usual stuff

The functioning would look like that:
1. Before the mission a necessary amount of fuel tanks is slowly gathered at the orbit with separate launches of heavy class rockets (12-25 tons)
2. Refueling depot slowly gathers the tanks and stores them
3. Mission spacecraft is launched and docked with refueling deopt
4. New tansk are added to spacecraft with the help of fuel deopt's robotic hand
5. Mission spacecraft leaves the refueling station and prepares for first burn

 

[mainmind]

Another user, docm, just posted links to ULA's design studies in another thread, found here:

http://www.space.com/common/forums/viewtopic.php?f=15&t=19951#p384469

They are much more informative than brief online articles. They make a strong case for the depot-based architecture because it allows for commoditized launch systems to LEO that can be provided by a variety of suppliers currently. Plus, their architecture has a single propellant pair for all engine systems, simplifying the architecture. Without the need for large ultra-heavy lift vehicles like the Ares V, development dollars can be spread over a shorter period on smaller pieces and launches can start earlier.

They make a very compelling argument. Plus, with the current problems of the Constellation program, any ideas that would close the flight gap after Shuttle are incredibly welcome.

Definitely give the architecture paper (in the link above) a read. The dual-thrust axis lunar lander paper is also a really interesting read.

 

[aaron38]

If orbital gas stations were to be the prefered mission profile, meaning that every mission to the moon or mars is going to dock at a transfer base and we're going to get a lot of use out of the thing...
Then given water's high density, would it make sense to launch the fuel as water, store it as water, then use solar power to split it when a refueling job was needed?

 

[scottb50]

If orbital gas stations were to be the prefered mission profile, meaning that every mission to the moon or mars is going to dock at a transfer base and we're going to get a lot of use out of the thing...
Then given water's high density, would it make sense to launch the fuel as water, store it as water, then use solar power to split it when a refueling job was needed?

That has been my thinking for the last ten years, especially of this particular forum. It only makes sense and not just for large scale propellant. My idea has always been using water and Solar power the provide Oxygen and Hydrogen, in a continuous system Oxygen and Hydrogen could power fuel cells and Solar powered hydrolizers would provide the Oxygen and Hydrogen. A system could provide electrical power for normal uses as well as propellant and as a bonus hydrolysis could purify and recycle waste water for other uses.

Add the protection water can provide from Solar and other Space events and it is a no brainer. Water is the key to the Universe, we have an abundance of water and it's going to take a lot of energy to get off this planet. The only resource that can provide it, in the amount that will be needed is water. Solar power is available all the time and requires a lot less effort to harness then Nuclear of other power sources.

The real focus should be getting water to LEO.

 

[docm]

It's one thing to dissociate the water using solar (heat or electricity) but quite another to liquefy hydrogen and oxygen where lots of things can go to hell real fast, and besides it adds complexity and you need big tanks to store the gases before they're liquefied. KISS, and cheap.

 

[scottb50]

It's one thing to dissociate the water using solar (heat or electricity) but quite another to liquefy hydrogen and oxygen where lots of things can go to hell real fast, and besides it adds complexity and you need big tanks to store the gases before they're liquefied. KISS, and cheap.

The best possible resource we have is the Sun. Hydrolizing water simply requires more electrical power. Storage is another problem, but if you store only what you need and insulate it to prolong loss as well as recycle it too re-cool it as needed it can be highly efficient. That's the ideas of using water throughout the system, you can remove contaminates and use the same water over and over indefinitely. Add more water to that initial volume and it becomes simpler.

For extended missions it would be a matter of how much water that is needed to sustain the crew, provide the propellant needed for the mission and protect the crew throughout the mission. Most of the water will remain at the end of a mission. This leads to recyclers that independently operate from one orbit to another, braking into Earth, Lunar or Mars orbit as needed and departing back to another orbit.