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Lunar Tourism

Posted by: campbelp2002 - Fri Feb 11, 2005 9:36 pm
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Post    Posted on: Mon Mar 14, 2005 8:37 am
campbelp2002 wrote:
Note that I have no reserve propellant at all, beyond what the LM had. Also, the 9,500 kg empty mass would include all other vehicle consumables, such as RCS propellant. I'll assume consumables for the passengers is included in the payload.


I dont think you can run a successful ferry service for passengers without having at least some spare propellant, if nothing else it would give some piece of mind to the passengers (No one is comfortable using a vehicle with an empty tank). This is irrespective of how much of a safety net this represents, its people's perception.

campbelp2002 wrote:
So, it is not so easy after all. The biggest surprise to me was the high penalty for bringing all the LH2 rom Earth. It would really help a lot if it could be gotten on the Moon.


I think there is a fair chance of finding ice on the lunar surface that the Hydrogen could be extracted from.

I like the idea of optimising the vehicle for its environment so that it doesnt have to land on the moon and Earth. IMO the use of separate components to do each phase is the most sensible approach. The use of a Bigelow space yacht design for the main ferry craft would give extra space that could be used to store additional supplies/oxygen should it become necessary for passengers to remain in orbit longer than planned.

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Post    Posted on: Mon Mar 14, 2005 2:38 pm
When I said no reserve I didn’t mean that I was literally planning a no reserve scenario. I was just pointing out that my 9,500 kg empty mass guess was not a fully detailed list of all mass needed.

I have been doing more calculations (again, all based on a guess of how much the empty vehicle mass would be), and discovered that the use of LH2/LOX really makes a difference. If Apollo had used all LH2/LOX instead of the hypergolic storable propellants it really used, then no separate LM would have been needed. They could have easily landed the entire space craft on the Moon and returned the whole thing to Earth with fuel to spare!

So, here are my new numbers, if LOX only is available on the Moon:
Moon to LEO
Payload 2,230 kg
Dry mass 15,000 kg
LOX 65,638 kg
LH2 5,618 kg (All from Earth)
total 88,486 kg
mass ratio 5.14
DeltaV 2.55 km/s (assuming aerobraking into LEO)
mass to LEO 50,208 kg
Propellant used 38,278 kg
LOX used 32,810 kg
LOX remaining 32,828 kg
LH2 used 5,468 kg
LH2 remaining 150 kg
LH2 reserve 1.00%

Note that I went back to a smaller deltaV for lunar ascent. This was based on a calculation I did showing lower gravity loss with a higher acceleration than the real LM used.

And the return trip:

LEO to Moon
Payload 2,230 kg
Dry mass 15,000 kg
LOX 56,948 kg (including 24,120 kg from Earth)
LH2 15,000 kg (all from Earth)
total 89,178 kg
mass ratio 5.18
DeltaV 6.0 km/s
mass to Moon 23,507 kg
Propellant used 65,671 kg
LOX used 56,290 kg
LOX remaining 659 kg
LH2 used 9,382 kg
LH2 remaining 5,618 kg
LOX reserve 1.00%

Again, I used a smaller deltaV for lunar landing based on higher acceleration of my vehicle compared to the LM.

Total mass needed to be brought up to LEO from Earth is 41,350 kg. More than half of that is LOX. I played with the numbers a lot and decided that is was more efficient to bring some LOX from Earth rather than bring it all from the Moon. This is still a much smaller mass to LEO than Apollo needed, and the lunar vehicle is much bigger. (15,000 kg now, up from 9,500. But it is still just a guess for planning purposes). Also I have a propellant reserve where it belongs, in the fuel tank and not lumped in with the dry mass.

If both LOX and LH2 are available on the Moon, then only the 2,230 kg payload needs to be brought to LEO.

If no LOX or LH2 is available on the moon, then 107,230 kg needs to be brought up to LEO. That is about the same as Apollo. But note that because of the higher energy LH2/LOX engines I get a much larger vehicle to the Moon, almost 4 times the 4,178 kg empty mass of the real LM.

All these calculations are based on an assumed exhaust velocity of 4.5 km/s and the deltaVs I looked up for various segments of the trip. Then I use the rocket equation to calculate the total mass of propellant needed and assume a 6:1 LOX:LH2 ratio in calculating the required masses of each fuel.

The dry mass is a guess based on weights of the real LM, shuttle external tank and shuttle main engine, scaled for a smaller vehicle.


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Post    Posted on: Thu Mar 24, 2005 9:53 pm
An HLLV can play multiple roles in this. As it stands, an HLLV could put 100 ton equipment filled stations in LEO--or wet-stage stations (capable of carrying fuels--unlike inflatable structures) that can be refilled--with 20 ton manned-only portions at the far end--rather like the POLYUS--only with a TKS type segment attached to an 80 ton TLI stage that can be a wet stage station or be filled with propellant, etc.

All the more reason to support HLLV.


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Post    Posted on: Thu Jun 23, 2005 3:44 pm
Here is my lunar tour. At least as much of a tour as I am likely to get in my lifetime!

http://home.austin.rr.com/campbelp/astro/scroll.html


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