Multiple-Vehicles Scenario
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SSTO Staging Options

Adam London

In the orginal scenario, the mass landed on the moon was the entire dry mass of the vehicle plus passengers and other payload and external tanks. It turns out that it is not feasible to bring the tanks and engines required for the Earth-to-low-Earth orbit (LEO) trip along for the ride. Some kind of staging in LEO is necessary.

The mission scenario I envision is as follows:

Option 1: One Single Stage to Orbit Vehicle (SSTO)

A very large SSTO launches to LEO and rendezvouses with a tank farm. Once there, its payload (a fueled LEO-lunar surface [LS] vehicle) separates and mates with required oxygen (O2) tanks. It performs TLI (trans-lunar injection, to approach the Moon), and then lands on the Moon. Passengers disembark (or stay on board, if it's nice enough and a Lunar Hotel doesn't exist yet). Eventually it refuels and lifts off, performs TEI (trans-Earth injection, to head back to Earth), and then performs EOI (Earth orbit insertion, to orbit Earth), where it drops off O2 for the next mission at the tank farm, and re-mates with its massive SSTO tanks and engines and reenters and lands.

Option 2: Two (or n) SSTOs:

The SSTO is basically a Earth LEO workhorse. It can either launch the LEO-LS vehicle with some fuel, or just fuel. Hydrogen (H2) is stockpiled with the O2 at the LEO tank farm, and whenever a LEO-LS vehicle comes up, it grabs fuel it needs and heads for the moon. When it returns to the tank farm, it drops off O2 tanks, and gets back into its (or a waiting) big SSTO shell and reenters and lands.

The SSTO in option 1 would be about 2 (or n) times as big as that in option 2. However, in option 1, you could put most to all brains, power, etc., in the LEO-LS vehicle, so what was left in LEO was really a big shell. It could perhaps get whatever residual power to keep itself warm, etc., while it waited from solar arrays on the tank farm, or from within itself. Eventually, with once-per-day operations, the big beast that went up in the morning could bring back the LEO-LS vehicle that was coming back that afternoon, and you could actually reduce the number of really big SSTOs you have to build, as the turn-around time wouldn't be the 4-5 days or round trip to the moon, but one day of round trip to LEO. Conceivably you would only need a fleet of a few big SSTOs, albeit with more, smaller LEO-LS vehicles.

Are you designing two vehicles? Yes, which is certainly a problem (= expense), but at least the space model comes back to Earth each time for maintenance. I think the integration issues are easier than a two-stage-to-orbit vehicle, since separation while in orbit is simpler than while in the atmosphere.

Also, you get a big LEO booster for free. You can put pretty large things into LEO with such a beast.

Imagine the passenger experience:

You get into this cylinder thing in Australia. Lots of shaking, a bit of extra gravity, then none. A few hours later you rendezvous with the tank farm. You watch out the window (perhaps from a lounge on the farm) [Yeah, I know I just threw another space station into the picture... but maybe it's the LEO staging base that we were talking about on art-list expanded somewhat, and you can look at pictures of the contruction of the original Artemis vehicle while your personal moon vehicle is being mated to its tanks.] You reboard (or maybe you never left) and move slowly away from the tank farm, dwarfed by the huge hulk of a ship you just came up from Earth on. A bit of acceleration and you're on your way to the moon. A couple weeks later, you're back, and again watch your little LEO-LS cruiser being docked to a waiting big ol' thing to transport you back to Earth.

I think that would work on the "looks neat" criteria...

Content by Adam London <>

Multiple-Vehicles Scenario

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