First watch the video if you haven’t seen it yet.
SpaceX had a presentation at the International Aeronautics Conference today about their Mars colonization plans, and specifically about the rocket/spacecraft system they’re using for the transport.
The thing is a beast, and although only marginally larger than the Saturn V in its key dimensions, it can launch over twice as much to Low Earth Orbit… reusably (in non-reusable mode, it’s over 4 times). They achieve this, basically, by use of modern technology: methane propellant, full-flow staged combustion engines (very fuel-efficient) and composite tanks.
It uses SpaceX’s currently-under-development Raptor engine, which looks to be the among the most advanced engines ever produced. Although “only” about half the thrust of the F-1 engine on the Saturn V, the first stage of the ITS will have 42 of the engines, compared to just 5 on the S-V. Getting all of those engines to work reliably will be a challenge, and to a large extent a similar challenge doomed the USSR’s attempts at a moon landing–their rocket required 30 engines, and they never quite worked out the dynamics of the problem. But times have changed so hopefully SpaceX will have greater success.
The booster is of course only part of the system. The booster carries the Mars craft much of the way to orbit, but its fuel is expended getting the rest of the way. So there are several refueling trips with a tanker craft that autonomously docks with the transporter. They aim to have very rapid turnaround, with the tanker landing near the launch pad, and the booster landing directly on top! It would sound ridiculous if it weren’t that SpaceX has already demonstrated landing precision of a couple of meters… and on a moving barge. So maybe this isn’t as absurd as it sounds. The tanker refueling system is the key to having a manageably-sized system that is reused enough times for good amortization. Without it, the rocket would be impossible instead of merely implausible.
After several tanker trips, we now have a fully fueled Mars transport with ~6 km/s of delta V. This is enough to get to Mars and land propulsively, with most of the excess velocity shed via aerobraking at Mars. The craft has heatshields and is largely empty at this point (only cargo left, with very little fuel), so even in the thin Mars atmosphere the aerobraking should be effective.
It’s at this point that the details get a little fuzzy. One major reason for picking methane on Mars is that it can be produced there, by using water ice and the CO2 atmosphere. These chemicals and a lot of electrical input energy is all that’s needed to produce methane and liquid oxygen. Since the vehicle lands with no remaining fuel, it’s critical that it can refuel on the surface to make the return journey (both to reuse the vehicle and bring passengers bath to Earth). “In-Situ Resource Utilization” (ISRU) is the key term here and SpaceX will clearly use it, but there was little more than handwaving toward it.
Although much of the presentation was, well, visionary, SpaceX is actually making concrete progress toward their goals. The Raptor engine was recently tested, at least in some form (probably a subscale prototype). Even more impressive to my mind was their prototype composite fuel tank. That thing is absolutely enormous, and demonstrates some serious capability for manufacturing large composite tanks. It may sound simple but tanks–especially cryogenic composite ones–have killed projects in the past (the X-33 Venturestar comes immediately to mind). So the fact that they have semi-real hardware already is pretty amazing.
Anyway, it’s all exciting stuff. You can watch the full presentation here, and see the technical slides here.
I’ve left out a bunch of stuff, so please ask if you have questions.
