Rand Simberg (Transterrestrial Musings)posted a few concepts for mars missions the other day involving refueling at various interplanetary depots with attendant advantages. Unfortunately, I couldn’t quite grasp the advantages compared to other depot scenarios in more conventional orbits. Though I am not a Mars first advocate, a lot of people are, and Mars is certainly going to be a relatively high traffic interplanetary destination for the foreseeable future. So I though I would try to figure out a most bang for the buck concept for a high mass Mars mission. It’s not all my ideas, just the best arrangement I could conceive shooting from the hip.
Rand suggested four Falcon IXH launches for the mission. I think that’s a good start. Four Falcon IX heavy launches totals 212 metric tons in LEO. IMO the challenge is to get as much of that as possible into TMI. Methods of rendezvous with Mars on the other end and the goals of that mission are up to you.
Launch three Falcon IXH into LEO well ahead of the Mars launch window. Use electric propulsion to send all three of them to an eccentric lunar orbit at just under lunar escape velocity with a perelune just high enough to be safe. The fifty three tons each in LEO should result in a total of about a hundred and forty three metric tons in that orbit assuming they expend no more than ten percent of their initial mass for the trip with the high efficiency (Isp) electric propulsion. Dock the three ships together.
Launch the fourth Falcon IXH with crew as the Mars launch window opens. In LEO, detach the five ton inspace crew taxi with ten tons of kero/LOX propellant from the rest of the ship and send it on a normal four day lunar insertion trip. The other thirty eight tons of Falcon IXH payload follows slowly on electric propulsion. The taxi mates with the first three vehicles in eccentric lunar orbit to create a single manned TMI vehicle of a hundred and forty eight tons.
The TMI vehicle makes a few meter per second burn to kick it out of lunar orbit into an Earth grazing trajectory. At peregee the kero/LOX engine fires for a roughly three hundred meter per second Oberth effect burn to put the whole vehicle on a Trans Mars Injection orbit. This should put a manned vehicle of about a hundred and thirty four tons into the TMI. This vehicle has both the kero/LOX high impulse engines from the taxi, and the high efficiency electric propulsion from the first three Falcon IXH vehicles for a mixed propulsion availability considerably better than either alone. When the thirty four tons remaining of the fourth launch catches up, the total vehicle will be one hundred and sixty eight tons heading for Mars.
It will be interesting to see if this is feasible, and how it compares to other scenerios involving four Falcon IXH launches with or without depots.