Space Taxi

[tap_sa]

I like the water-storage-and-electrolysis idea but IMHO it's a bit too complex for moontaxi <b>v1.0</b>. The taxi itself needs LOX/H2 so much and so fast that it cannot do the process itself, therefore to succesfully use it a fueldepot on LEO is needed. I'm certain that there will be those eventually but in 2015, doubtful. So taxi v1.0 would probably be fueled by medium or heavylift ELVs. LH2 is excellent in the combustion chamber but difficult in the tank, especially in moontaxi where your trip takes days, boiling off return-propellant while enroute is bad for the business. It appears that LH2 can be stored with very little boil-off in space but it requires very good tank insulation and I'm not sure if the taxi v1.0 weight budget can afford that.<br /><br />I did ran the numbers anyway with LOX/LH2, assuming 460s I_sp and 6:1 mixture ratio. Same flight pattern as before, fly to moon, land, ascend and aerobrake back to earth. If all propellant is loaded from LEO 17.7 tonnes is required. Get return-LOX from moon and 12.6 tonnes is required from LEO. Total tank size grows from 35.1m³ to 49.3m³<br /><br />Lunar LOX/Al monopropellant might be interesting option in the future. At least they claim it's not shock sensitive and have fired a test engine. I guess it's the aluminium's habit of forming protective oxide layer that keeps it insensitive even in LOX.

 

[grooble]

Yes, we can put together a design utilising todays tech, and then revisit it as new technology is made available.<br /><br />Like Morris did with the Gemini.<br /><br />I say it would be post 2015 for the following reason, let us say the space exploration vision is successful, NASA lands on the moon, and builds a small base. That would invigorate the interest and belief that we can do things on the moon. <br /><br />A private mission could be launched to build an initial infrastructure, probably not too far from the nasa base, and its use could be shared and certain co-operative arrangements made. <br /><br />I don't know how difficult it is to create fuel on the moon, but that is what the private mission would be tasked with. <br /><br />Once it is ready, the taxi can refuel as much as needed and perform a round trip, bringing more supplies, expanding, bringing costs down, new models will be built, new improved fuel methods found, and you'll have good moon growth.<br /><br />Governments will always be able to go to the moon if they choose, but my wish is for it to be made within the realm of possibility for medium to large businesses, universities and moderatly rich people. <br /><br />

 

[scottb50]

The taxi itself needs LOX/H2 so much and so fast that it cannot do the process itself, therefore to succesfully use it a fueldepot on LEO is needed.....<br /><br />Perhaps I wasn't overly clear. What I was proposing was doing electrolysis in LEO and Lunar orbit at dedicated stations the cycling vehicle would dock to. The vehicle would transport water to the Lunar station, but the conversion would be done leasurely in orbit, not frantically enroute.<br /><br />The exception would be a Mars mission, then it would make sense to produce the propellant enroute needed to esptablish orbit, other wise a station in orbit would provide for return propellant. Additionally a Lunar or Martian lander/return vehicle would load propellant in orbit rather than on the surface to allow greater payloads.<br /><br />...boiling off return-propellant while enroute is bad for the business. It appears that LH2 can be stored with very little boil-off in space but it requires very good tank insulation and I'm not sure if the taxi v1.0 weight budget can afford that.....<br /><br />I would think boil-off could be easily recycled rather than lost, especially if gaseous Hydrogen and Oxygen are used to power fuel cells. Another advantage of using fuel cells as primary power sources would be simpler voltage regulation, which would be harder using solar power, something electronics would appreciate.<br /><br />If done this way I would think the tank size would be very comparable, if not smaller.<br /> <div class="Discussion_UserSignature"> </div>

 

[erikm]

Post deleted by erikm

 

[taolung]

This may not be what you're looking for, but it may be possible to get all your propellant from the lunar soil. I believe that deuterium and helium-3 can be extracted there, manufactured into pellets, and then detonated by laser beams to produce thrust. Look up "Project Daedalus."

 

[R1]

well I hope you get started real soon<br /> I hope somebody does something , decades passed and we don't even have<br />a real permanent solar sail, just the little 30 day inflatable thing that Russia has been<br />trying to do.<br /><br />if someone brought back cans of moondust are they legal to be sold? if they are<br />would it be alright if its a fundraiser for the moonbase?<br /><br />Nasa or someone, maybe wealthy people could<br />have built an unmanned probe by now, and brought back a ton of lunar soil by now,<br />made their money back, and earthling industries would by now have mastered many uses of<br />the lunar soil (for use by future moon bases, of course)<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[grooble]

bump<br /><br />The dream lives on. I am planning for a 2050 launch.

 

[nacnud]

Ten to nine? Will we get back for last orders?

 

[nexium]

Please explain,"Ten to nine? will we get back for last orders? Neil

 

[nacnud]

2050 -> 20:50 -> 8:50pm -> ten to nine<br /><br />The pubs round here ask for last (drinks) orders 10 minutes before they shut, normaly about 11:00pm, hence: <br /><br />If we leave at ten to nine on the space taxi will we be back in time to go to the pub.<br /><br />It's not such a good joke now <img src="/images/icons/frown.gif" />

 

[spacefire]

I'm planning for a 2020 launch sao I ebat you by 30 years already!!! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[erikm]

(note after posting) Hmm. I'm following up my own post. Baaaaad Erik. <img src="/images/icons/tongue.gif" /><br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>How about going in a different direction with respect to fuel in taxi v1.0? Could, for instance, methane be used as fuel? As a molecule it is bigger (and heavier) than hydrogen and as a liquid it's far easier to handle. IIRC freezing and boiling points aren't that different from oxygen. This alone should solve quite a number of boil-off insulation problems. <p><hr /></p></p></blockquote><br /><br />Methane and Lox are good, but they're still cryogenic liquids, with (reduced) boil-off problems. It might be worth it in terms of ease of engineering to go entirely to storable liquids. This will lower Isp but eliminates many fuel-related problems, including storage issues. <br /><br />As fuel you could also consider using propane or butane. They're both short-chain hydrocarbons, commonly available and dense. They also have nice high boiling temperatures (propane has a boiling point of -40C, butane -0.5C) so tank pressurization can be done without helium. Maybe you can make do with a simple heating element integrated in the tank wall.<br /><br />As oxidizer you could go with high test (95-98%) (hydrogen) peroxide. It melts at -11C and boils at 141C, so a tank will probably have to be insulated against the cold and (maybe) have a heating element as well. Initial pressurization might be done with oxygen. Repressurization could be done by catalytically decomposing some peroxide into Oxygen and steam. For example, a silver needle (silver is a catalyst) could be driven into the tank through a sealing grommet.<br /><br />Other people might suggest using MMH/UDMH/aerozine-50 and tetroxide. I'm not a fan of those because of the handling issues.<br /><br />In Taxi v1.0 the fuel and oxidiser would be sent up in plug-in bottles, essentially balloon tanks with sealing grommets. Initially these would be single-use, but later Taxi ver