The Moon Society Forum

Seems to me, that we could turn the ISS into an L1 space station. By 2020 it would probably need an overhaul, but that should be doable. Perhaps some inflatable modules could be added and an electric drive for station keeping at L1, along with some extra communications equipment.
Anything would be better than deorbiting it like the MIR.
After giving it some more thought, I think L1 is the best place for an overhauled ISS. If we want to land it on the Moon, we must disassemble it. That would be a big job. Also, we need a system to land it. The trusswork wouldn't have much use on the Moon and the crane/arm might not work in 1/6 G. Solar panel output degrades by 25% after 10 to 15 years. Either we'd need new solar panels or we'd need to heat them with microwaves and anneal them. This was suggested for maintaining SPSs.
One of our M.S.St.L. members has calculated that only about five pounds of constant thrust would be needed to keep the ISS in orbit. Most electric drives have electrodes that will burn out in time, but VASIMR does not. To save the ISS we really need to develope a small VASIMR thruster. As for an LEO way station to the Moon, we won't need one if all the cargo packages launched to LEO have their own electric drive system and manned craft have a hi-thrust chemical trans lunar insertion stage. At L1, humans could transter to landers and descend to the Moon, and vice versa. The L1 station would also be a tracking and communications center for exploration teams on the Moon. To get the ISS to L1 we'd need an electric drive; probably a VASIMR thruster. Work is underway to develop VASIMR for rapid transit to Mars. We could probably develop one for the ISS L1 station in a few years time. Once the station was at L1 it would probably require less propellant for station keeping that it would for orbital reboost.
The problem is, will we have a lunar transportation system for cargo and humans by 2020? How long would we have to keep the ISS mothballed in LEO or at L1? We can be certain that the trusswork and metal modules won't degrade, but what about seals, bearings and such? If we have to overhaul the station and replace everything that wears out, so what? That's gotta be cheaper than building and launching a whole new station!!!
Another thing we could do with a station at L1 is house human crews sent up to service space telescopes in the L1 region or attached to the ISS-L1 station. It would be good to have humans at the L1 station to maintain and repair comm. and tracking equipment for ground crews too. Loss of comm. and navigation links for lunar explorers could be deadly, but if humans are on hand at the L1 station, they could fix things in a pinch.
Another thing we could do with an ISS-L1 station is teleoperate robots anywhere on the nearside paving the way for human workers. Teleoperation from Earth involves a 3 second delay. The only way to deal with it is to go real slow and forget about very fine robotic operations. From L1 the delay is just a fraction of a second. Teleoperation from L1 would be far more effective. It would do away with the cost of landing humans, which means you need propellant for landing and ascent, which means you need more propellant in LEO for rocketing that extra mass to the Moon, which means you have to foot a much higher bill. By just going to L1, costs are slashed and robots could be used for all kinds of preliminary work, including setting up lunar derived propellant production.
Think about this. If we develop reusable spacecraft for landing on and ascending from the Moon to an L1 station, we can cut costs by using electric drives to transport the MMN and N2O4 from LEO to L1 where we fuel the lunar craft-i like to call them Moon Shuttles. Humans would leave LEO in rapidly accelerating chemically propelled craft to minimize VAB exposure time and dock at the ISS-L1 station then descend to the Moon. With humans at the L1 station to maintain and repair refueling equipment we could insure mission success. There could be back up Moon Shuttles at the L1 station in case something goes wrong with the one workers descended in, so they won't be stranded on the Moon.
I think that if an international program to return humans to the Moon and build a permanent base is ever realized, an L1 station and electric drives as well as reusable Moon Shuttles and refueling systems would be the right transportation architecture; not a massive "Apollo on steroids" one-big-rocket-goes-to-the-Moon like the one that's been envisioned for the past few years. It would be safer too.
As for radiation at L1, start on pg 113 of "The Case For Mars"
According the Zubrin, with about 5 grams of mass per square cm in the form of a hull, furnishings, systems, etc. the cosmic ray rad dose in transit and from to Mars, 150 days each way, would be 31.8 REM. With a solar flare shelter, 5.5 REM, from solar flares. A pilot gets about 25 REM during 25 years of flying.
I don't think that cosmic rays are going to be showstoppers for an L1 station outside of Earth's magnetic field. We won't need megatons of shielding either. But this gives us a very good reason for attaching a trans-hab like inflatable module with thick plastic walls, since plastic makes good rad shield because it is hydrogen dense. There could even be water bladders in the walls. An inflatable, or 2 or 3, could serve as solar flare shelters and sleeping quarters while the hard modules are used for work and storage. L1 crews would probably stay up for no more than a year. The cost of shuttling L1 crews from and to Earth will be lower since we don't have to land them. Of course, it depends on how necessary it is to keep crews at L1.
In this early stage we are not talking about settlement or colonization, but mostly about start up. When we reach the settlement stage the ISS will be a museum piece.

Robotic on orbit refueling has been demonstrated along with some parts swapping
http://www.darpa.mil/orbitalexpress/
http://www.space.com/missionlaunches/07 ... eling.html
http://www.spacex.com/falcon9_heavy.php
65,280 lbs to LEO for F9 Heavy, as opposed to 23,050 lbs to LEO for the std. F9 at almost $2000 per pound
The dV to L1 is 3150m/s or 3.15 kps 450 sec Isp LH2/LOX rockets ex. v is 4.41 kps
e^(3.15/4.41) = 2.043 65,280/2.043= 31,953 65,280-31953= 33,327 lbs of propellant
since the rocket upper stage will amass about 15% of propellant mass, that's 4,999 lbs.
So the rocket and propellant amass 38,326 lbs. and the payload, in this case a crewed capsule, amasses 26,954 lbs. or about 13.5 tons That's a respectable capsule, Certainly it could carry four humans.
I don't know what the numbers are for braking into L1 and retro-rocketing back from L1 to Earth, but i don't think its more than a few hundred m/s either way, so the 13.5 tons capsule should be able to carry enough propellant for these maneuvers.
For the Moon Shuttles to land they need about 2.4 kps from L1, nearly lunar Vesc. UDMH or MMH and N2O4 are space storable, unlike LH2 and LOX, and they have a lower specific impulse....but to deliver these to L1 we just need some VASIMR thrustered tugs that get there ahead of time, and it's safe to estimate a propellant load only 10% of payload with electric propulsion.
It might be possible to develop a Moon Shuttle that runs on upported UDMH or MMH and LUNOX.
I wonder if we have something here. It would give the ISS a second life and if SpaceX gets all their Falcon versions flying, I don't think we'd need the Ares V monster rocket. We do need more research and development into electric drives large enough for the job, but VASIMR research for missions to Mars is or was ongoing, and if they can develop one that can send a vehicle to Mars certainly it could reboost the ISS, move it to L1 and do station keeping and send Moon Shuttles and tanks of propellant to L1. The tanks would eventually be cannibalized. We'd need R&D for space refueling too.
The shuttle OMEs run MMH and N2O4 at 316 seconds isp
That's 316*0.0098 = 3.097 kps
if a Moon Shuttle requires 2.4 kps to land and 2.4 kps to return to L1 then:
e^(4.8/3.097) = mass ratio of 4.71
That's not a very high MR for a vehicle that only has to endure low Gs compared to an Earth launched vehicle
If the MShuttle amasses 7 tons dry, it would need 26 tons or 52,000 lbs of propellant
A Falcon 9 Heavy could put 65,280 lbs. in LEO, so there would be 13,280 lbs left for the electric drive module, tanks and propellant. Since 15% of 52,000 is 7800 lbs.of tanks, we have 5480 lbs left for electric drive and propellant. This cuts it pretty slim.
if the MShuttle amasses 6 tons dry, it needs 22.26 tons or 44,520 lbs MMH and N2O4 to land and return to L1. This gives us 6670 for tanks and 14,090 for electric drive module and propellant for transfer from LEO to L1. If 10% or 6528 lbs is e drive propellant we have 7562 lbs for the VASIMR thruster and solar panels to energize it. Seems doable.
i calculated that one F9 hvy could send a 13.5 ton capsule to L1
another F9 hvy could send enough propellant for a 6 ton dry mass Moon Shuttle to L1
a third F9 hvy could send several MSs to L1, but more launches would be required to fuel them
from: http://www.astronautix.com/index.html
Apollo LM ascent stage mass wet 10,024 lbs. fuel 5198 lbs. dry mass 4826 lbs.
Apollo LM descent stage wet 22,374 fuel 18,000 dry mass 4374
total dry mass 9200 lbs or 4.6 tons
so maybe we could develop a 6 ton single stage descent/ascent Moon Shuttle that is fully reusable
perhaps it would be open cockpit like the Artemis Project lunar lander
more lunar landers; http://www.astronautix.com/craftfam/lunnders.htm
Apollo CM 12,800 lbs.
Apollo SM wet 54,063 fuel 40,593 dry 13,470
total of CSM 66,863 lbs. or 33.4 tons
This is way over the 13.5 tons for a capsule to L1 by F9 hvy, but a capsule to L1 does not have to brake into LLO with not just its own mass but the mass of a fully fueled LEM too and accelerate out of LLO for return to Earth and aerobraking. Since the CM amassed 6.4 tons it seems to me a 13.5 ton capsule with a smaller SM could reach L1 and return. It would be a single fully reusable unit after heat shield replacement, not a separate CM and SM.
http://www.astronautix.com/craft/soy7kmf6.htm
Soyuz 7K-MF6 mass loaded 14,350 lbs or 7.175 english tons. The Artemis Project was to use a Soyuz capsule, and this comes in well under 13.5 tons
http://en.wikipedia.org/wiki/Orion_(spacecraft)
The Orion CM 8.5 metric tons, 19,000 lbs. so this comes in under 13.5 tons for a F9 hvy
but the Orion SM is 8,000 lbs. dry with 18,000 lbs of fuel total 26,000 lbs and this puts us over, however, as i said before, we don't need to brake the entire system into LLO etc. etc.
http://en.wikipedia.org/wiki/Altair_(spacecraft)
ascent module 23,830 lbs. descent module 77,280 lbs.
This is loaded with fuel and oxidizer....totals 101,110
For the F9 hvy i calculated we could get 44,520 lbs to L1 with electric drive and the lander would amass 12,000 lbs so that's 56,520 lbs loaded with fuel....so the Altair is much heavier than what i propose with the F9 hvy and electric drives...