Space Taxi

[grooble]

Purpose - ferry human and cargo modules to and from the moon and earth. <br /><br />Specs -<br /><br />- Autopilot, no life support required.<br />- Autodocking of modules<br />- Huge power reserve to allow journey to earth and back to the moon where it can recharge / refuel<br /><br />What you have then is the first export from the moon, a taxi service. <br /><br />Listen to this, for the mere price of a Falcon-5 launch, i can get you or your cargo to the moon, + a small fee toward recouping my operating costs on the lunar surface.<br /><br />Over time, and as i make my money back and generate profit and expand my lunar facilities, i'll be able to increase the flight rate of the taxi and reduce the price, to increase my sales and expand further. <br /><br />P.S it'll be called "The spirit of new york" or the "The spirit of London" depending whether i paint it Black or Yellow.<br /> <br />I may paint it the colours of the UK flag.<br /><br />I'd charge say $1-2 million a trip, so 1000 trips i've made $1 billion of the investment back.<br /><br />

 

[tap_sa]

<font color="yellow">"Autopilot, no life support required."</font><br /><br />What, can't I hop in and say 'Driver, follow that CEV!' ? <img src="/images/icons/frown.gif" />

 

[grooble]

Well i could put a robot one in. Ideally there would be the teleoperator at the moon base to reassure the passengers. They could have live video of his face or somethin. <br /><br />I think i finally found my lifes purpose!<br /><br />Hell, a further 30 years down the line i could have the space cruiser to ferry people to mars and back.<br /><br />I'm 22, i think i can do it before i'm 80<br /><br />I will put a website together for this idea.

 

[grooble]

Imagine how awesome it would be if JPaerospace's balloon ship got a cargo container to orbit, which then docked with my taxi, getting it to the moon?

 

[tap_sa]

Will you buy lunar propellants from me if I set up a plant on the Moon. I'd haul my equipment in your taxi. Just imagine how much lunar oxygen alone would save your freight costs!

 

[grooble]

Sure dude, you can fuel my entire fleet. Morris can provide luxury crew modules, launched on the latest Falcon rocket. Bigelow could build the hotel.<br /><br />You can build a mining / energy business, with me as one of your main customers.<br /><br />I'm sure that guy, Kraken i think, has plenty more business ideas, but i'd love to do the taxi fleet.

 

[grooble]

Unlike the space cannon, which i was very intrigued with but i do not believe is feasible by a civilian / private individual such as my self, due to its weapon capability and enourmity of the project, I actually believe this space taxi / tug, is well within the realm of possibility.<br /><br />I think the tech needed wouldn't be too much further than DART. No life support is needed, the crew modules launched from earth are someone elses job.<br /> <br />I'd make it integratable with the CEV.

 

[tap_sa]

Post deleted by Tap_Sa

 

[tap_sa]

<font color="yellow">"You can build a mining / energy business, with me as one of your main customers."</font><br /><br />Behold, LuMet inc. , purveyor of finest lunar metals. Aluminium, Steel, Titanium, all in stock (really soon now). Hmm www.lumet.com appears to be taken, forsale for $470 .. bummer. Maybe I'll register the company in UK, www.lumet.co.uk how does that sound? We'd have a machine shop too, lathes, mills etc. to satisfy your manufacturing needs.<br /><br />Btw does your ferry trip include shuttling customers to moon surface or just to LMO?

 

[grooble]

Surface, Cargo too. <br /><br />By taking advantage of the latest advances, such as 27% solar efficiency: http://www.renewableenergyaccess.com/rea/news/story?id=25166, we can generate a good amount of energy for the total system.<br /><br />Just think of the advances they'll be when 2015 comes along!

 

[ve7rkt]

You'd need refuelling stops at both ends. At Earth, you'd take on enough propellant to make a round trip, and you'd have enough oxidizer for one way. At the Moon, you'd load up on enough oxidizer for a round trip, and you'd still have enough propellant to get back to Earth. Now, that's a LOT better than lifting propellant and oxidizer both from Earth, but unless there's a lot of water on the Moon -- and who knows, there could be -- the propellant still comes from Earth.<br /><br />Lifting that propellant off Earth costs around $4m/ton with Falcon V. Lift ready-to-install tanks, no messing around with transfer hoses, just pull off the empties and hook up a six-pack. Buy 4 tons of LH2, get a free tank of helium for tank pressurization!<br /><br />(not responsible for propellant loss through boiloff/venting after delivery, some conditions apply, void in orbits inclined above 52 degrees)

 

[grooble]

Is it possible to get the entire fuel from the moon?

 

[ve7rkt]

IF there is water on the moon, then yes, you can get all your fuel at the Moon. Big honkin' solar power array providing electricity to an electrolysis plant, gives you hydrogen in one tank and oxygen in another. Perfect.<br /><br />If there is no water on the moon, you can still get oxygen by extracting it from the lunar rock. You can breathe for a long time, but you're missing the other half of your rocket fuel.<br /><br />Maybe there's water-ice in a few dark craters near the poles. Maybe there isn't. Clementine and Lunar Prospector seemed to indicate there was, but when they smacked Lunar Prospector into the surface near the south pole, one of the most promising locations, and looked at what got kicked up, there was no ice.<br /><br />In summary, you can count on oxygen for sure, but until we know for sure, you can only hope for hydrogen (and don't get me wrong, I really do hope!)

 

[tap_sa]

Depends what you want to burn. Hydrogen, probably available from lunar poles. Methane, difficult, Moon has so little carbon that initially it all would be needed in the bases to boost carbon cycle (CO2->plant->food->human->CO2). Aluminium, that would be good. Making solid might be too difficult, requiring other complex materials, but as a powder, mixed with hydrogen. You could also burn something like sulphur.

 

[mental_avenger]

<font color="yellow"> Autopilot, no life support required. </font><br /><br />I can just hear the announcement to the passengers shortly after takeoff. "Ladies and gentlemen. Welcome aboard the first fully automated space taxi. This taxi includes the latest equipment available. It is the safest transportation on or off the Earth. Every precaution has been taken to ensure that nothing will go wrong…………… go wrong…………. <font size="-2">go wrong………..</font> <font size="-3">go wrong………..</font><br /> <div class="Discussion_UserSignature"> <p style="margin-top:0in;margin-left:0in;margin-right:0in" class="MsoNormal"><font face="Times New Roman" size="2" color="#ff0000"><strong>Our Solar System must be passing through a Non Sequitur area of space.</strong></font></p> </div>

 

[jimglenn]

Put some people on it, what a neat job! Make it look like the ship in 2001, the Jupiter something or another. <div class="Discussion_UserSignature"> </div>

 

[grooble]

The taxi will have Aluminum-Beryllium Alloys for the hull. Not sure how big it should be. It'll pretty much be one brilliant engine and fuel storage tank. <br /><br />It would need an engine and fuel capacity to break earth orbit and get to the moon.

 

[grooble]

Yes, the power requirements could be met. It would mean a 2nd generation Space Taxi could do an Moon to Mars run.

 

[tap_sa]

Ion engines have too abysmal T/W for short trips, breaking LEO would take eternity (or at least a year, like Smart-1).<br /><br />grooble, does the whole ferry land on the Moon or are there separate shuttles for LLO <- /> Moon surface trips? And do you plan to aerobrake back to LEO?

 

[grooble]

It'd land on a moon pad. It'll have all round thrusters and accurate positioning. The onboard computer would handle the calculations and adjustments at a lightning fast pace, we're talking cutting edge computer power, post 2015. Probably some kind of Quantum computer.<br /><br />I'm wondering how big the taxi should be, whether the modules sent up from earth should attach externally, or be loaded into a large cargo bay.<br /><br />Not sure about aerobraking.

 

[grooble]

It would land on a special pad, there wouldn't be much dust to kick up. <br /><br />ISS style modules is what the folks on earth would develop. All i do is hook up to their module and land them on the moon. It is upto the buyer to ensure their module meets the life support needs of its crew.<br /><br />Just think, by the end of the century there could be Asteroid tugs.<br /><br />In essence, the taxi is a powerful, fast, highly manouverable, highly accurate and autonomous tug + lander. <br /><br />I think it could fly 1000s of missions over a multi decade life span. It could always bring resources and crews back from the moon too.

 

[grooble]

Here is a picture, version 0.001, i know it is bad, i have minimal technical drawing skills.<br /><br />The thrusters on the bottom would lift the taxi, whilst the rear thruster creaters forward momentum. I don't know how the module would get down from the taxi yet.

 

[scottb50]

Your idea has the same problem that the Shuttle has. You are trying to do too many different things with the same vehicle, like commuting in a Mac Truck because you might want to haul gravel on the weekend. It's a lot easier to hook a trailer to a pickup if you need to haul gravel and use the pickup for everyday commutes.<br /><br />I think the best approach is to have one vehicle that does nothing more than take payloads from the Earths surface to LEO, no 2 week missions, modular research facilities in the payload bay, just put a payload into orbit and come back to do it again, over and over. Since this is the hardest and most expensive part of Space travel it only makes sense to make it as simple and cheap as it can be.<br /><br />The next element is a version of your taxi that picks up the payload and takes it to a LEO Station, at the same time releasing a return payload back to Earth.<br /><br />The third element is a cycler that goes from LEO to Lunar Orbit or Mars Orbit, and back, over and over again. <br /><br />Vehicle based on the Moon or Mars bring Earth return payloads to orbit and take incoming payloads back to the surface. <br /><br />It makes a lot more sense to base them on the surface, from a maintenance point of view, more storage for parts, propellant, bigger facilities, ect. The real advantage is having very specilized vehicles rather than all-in-one vehicles, which means simpler systems, more reliability, lower cost and above all, greater safety.<br /><br />Having payloads and passengers in self contained modules, that attach to the various vehicles, provides a lot more utility than trying to build an all-in-one vehicle. <br /><br /> <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

Interesting link, thanks! Still, the problem isn't the thrust per se, it's the ion engine's (powersource included) weight related to it's thrust, aka thrust to weight ratio, T/W. We have a certain timebudget how fast we want to get to moon and mars. If people are involved then we can't wait year(s), we need faster acceleration.<br /><br />grooble: I ran some numbers regarding the taxi, here some results:<br /><br />No aerobraking, no go. At least not if the taxi itself does all the maneuvers including landing. Needs too much deltaV. I didn't calculate exact orbits and deltavs but estimated based on examples in Sutton's rocket book. It said moon softlanding requires about 15.2km/s dv and if return is included 17.7km/s. If we assume 9km/s dv to get to LEO then non-aerobrake moontrip needs 6.2*2=12.4km/s dv and using aerobrake 8.7km/s<br /><br />If craft itself weighs 2 tonnes, delivers 2 tonne payload, returns empty, gets all propellant from LEO, burns methane (I_sp=370s) then each trip needs 29 tonnes of propellant. If propellants were in a spherical tank it's diameter would be about 4 meters. Or it could be a cylinder 3.2m diameter and 4.4m tall.<br /><br />Many of you may judge the vehicle 2 tonne empty weight way too small but consider this: The roughest part of the journey would be landing to the moon, landing mass would be 6 tonnes. Maximum deceleration during descent would be about 1G, maximum ascent acceleration perhaps a little more but under 2G. Lower accelerations could be possible but if they go much below one gee then gravity losses start to get out of hand.<br /><br />Pressure stabilized tank/hull with 0,02 mass fraction would weigh 600kg. Can Scaled build the tank to this spec with all the composite goodies? Don't know, but AFAIK the 50s Atlas stainless steel balloon tank had 0,01 mass fraction.<br /><br />With modest 50 T/W the engine would weigh 120kg. State of the art hydrocarbon engines have 100+ T/W. Then there is attitude control, heat shield and la

 

[scottb50]

The simplest means is transporting and stockpiling propellant in LEO and Lunar orbit. What's needed on the Moons surface would be transported down. This would require putting the propellant into LEO only and taking it as cargo to Lunar Orbit.<br /><br />Producing LOX on the Moon may or may not be economical, but at any rate would not be feasible from the very beginning anyway. If it pans out putting it into Lunar Orbit would be less demanding than bringing it from Earth. It would also be more economical to transport it as a gas and react it with Hydrogen in orbit so it could be stored as water. Hydrogen would have to be transported, but it's pretty light, especially as a gas.<br /><br />The simplest, safest and most economical way of doing it would be putting liquid water in LEO as cargo and using solar power to break it down. I fail to see the facination with methane, the transportation, storage and maintenance it would require, as well as the safety concerns with launching the amount that would be needed for sustained operations. <br /><br />Maybe you could run numbers on using LH and LOX in the same scenerio, I would be interested in the results. Let's say a lunar based transport departs fully fueled and tops off in lunar orbit for it's return to the surface. The enroute cycler leaves LEO with propellant to reach lunar orbit and enough reserve to do an Apollo 13 emergency return if needed. Propellant would be added in lunar orbit for a normal return. <div class="Discussion_UserSignature"> </div>