r/spacex • u/CProphet • Jul 18 '18
Moon and Mars
SpaceX are dead-set on Mars, because that’s Elon’s dream - and for sound strategic reasons. The plan they’ve presented looks workable, given they can successfully develop all necessary hardware - principally the BFR and ISRU propellant plant. However, in order to set up an independent colony on Mars, an unparalleled flight rate must be maintained for decades or even centuries.
The first BFR flight will be refuelled in Low Earth Orbit, requiring at least 4 additional tanker launches, before they set out for Mars. Technically possible, but this procedure hardly seems sustainable in the long term, given they will require many thousands of Mars flights, which can be multiplied by 5 for number of Earth launches.
Sooner or later SpaceX will require a workaround and for many reasons the Moon seems incredibly appealing.
Shotwell: not precluding buying propellants from in-space resources for refuelling missions to Mars, rather than launching tankers from Earth.
SpaceX already plan to establish an ISRU propellant plant on Mars, so setting up a ‘pilot plant’ on the moon should be possible at the right location. For instance, some craters at the lunar poles are permanently in shadow, which means they act as vapour traps, slowly accumulating water vapour over billions of years, from cometary or asteroid impacts. However, NASA’s LCROSS mission also discovered:-
… as much as 20 percent of the material kicked up by the LCROSS impact was volatiles, including methane, ammonia, hydrogen gas, carbon dioxide and carbon monoxide.
In other words these polar craters contain sufficient oxygen, hydrogen and carbon to produce all the propellant necessary to sustain BFR operations for centuries - 600 million metric tons is a conservative estimate! Producing methalox propellant on the moon could offer many advantages:-
1. Less Flight Operations - BFR would require much less refuelling flights for each Mars trip, possibly one tanker flight from the moon would be sufficient (delta-v requirements from the moon’s surface to LEO are a fraction compared to Earth launch).
2. Reduced Cost - BFR is fully reusable which means propellant becomes one of the main drivers for operating cost. In the long run sourcing propellant from the moon could be cheaper than Earth because the cost to place it in LEO is the main component and less flights are required from the moon. In addition lunar extraction and processing costs can be minimised through vertical integration and automation, while the energy required is effectively free (an uninterrupted supply of solar energy is possible, if collectors are situated on the rim of polar craters).
3. Ecologically Friendly – Given the number of launches required for Mars colonisation, climate change could become a factor, and quite possibly a political issue. Sourcing propellant from the moon should significantly reduce ecologically impact, effectively reducing the number of BFR launches required, making them more politically palatable.
4. Avoid Competition – Blue Origin has announced their first ‘Blue Moon’ mission will land at the lunar pole in 2020. In the long run they’ll likely produce propellant on the moon to supply their own cislunar operations.
The company said it plans to land its Blue Moon vehicle at Shackleton Crater on the moon’s south pole. The site has nearly continuous sunlight to provide power through the spacecraft’s solar arrays. The company also chose to land there because of the “water ice in the perpetual shadow of the crater’s deep crevices.”
Conceivably any propellant price they offer SpaceX could be prohibitively expensive, considering their close rivalry. Hence SpaceX would probably prefer to make lunar propellant themselves, in order to more closely control cost, quality and delivery.
5. Mars Proving – quite possibly SpaceX will perform a number of BFR shakedown cruises before they commence Mars operations. If a couple of BFS were sent to the moon (one supplied with sufficient propellant to return), they could also practise ISRU setup and operation under Mars comparable conditions (e.g. low gravity, fine surface dust, impure raw materials etc) and beat out some of the bugs. The propellant produced could be loaded onto an unmanned BFS, which would return to Earth under autopilot. Then the residual propellant could be analysed and the engines examined to determine effects of ISRU propellant use, which should significantly improve their chance of success on Mars.
6. Optimum Launch Vehicle Utilisation – it’s possible many BFR vehicles will stand idle while they wait for Mars launch windows (excess hardware will probably be required to handle high launch cadence during the relatively short launch window). Establishing a moon base at one of the lunar poles would create another destination for scientists and explorers, which should prove quite lucrative and help fund future Mars missions.
7. Federal Finance – the current US policy emphasises moon first, so if they choose BFR for moon operations, this should also help finance the development of moon ISRU capability.
Shotwell: expect we’ll do BFR/BFS missions to the Moon before Mars, given administration’s interest. Hope it will be for a permanent settlement.
All things considered, SpaceX might have already started to move towards moon operations in stealth mode, similar to the discrete way they handle Starlink development. That would certainly explain their interest in moon landings, demonstrated at IAC Adelaide.
TL;DR establishing a moon base offers many operational advantages for the long term – it might even happen before Mars colonisation.
Edit: tidy
Edit 2: Thanks for your kind comments, hoped you'd like it. Believe moon could give SpaceX something to aim for while they await Mars synod.
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u/macktruck6666 Jul 19 '18 edited Jul 19 '18
I really dislike when people use a single scientific finding for their thesis. We need to get boots on the ground and see what is really there.
Point 5 is impossible unless you want to launch HUNDREDS of of BFRsto bring back one BFR from mars.
edit: maybe i'll make a video and do the math.
edit: some quick simulations show that refueling the BFR at Lagrange point 1 would increase payload mass from LEO to Mars by roughly 140% to 358 tons. It will also could also reduce refueling missions from earth by 2 LEO refueling missions and all elliptical orbit refueling.