Does this sound believable for anyone that knows something about the current state of the art in space traveling?
- a propulsion system that can send an habitat and supplies good for, at least, 6 months.
- a separate trip to send the supplies for the return mission and park it in Martian orbit for rendezvous when the manned vehicle arrives
If you also want the crew to land on Mars, you'll need a lander. You may consider doing the surface-to-orbit return mission on a separate vehicle you can land before. You may consider sending supplies and a shielded habitat (Martian surface is about as shielded from cosmic radiation as space itself - not at all) if you want the humans to stay.
20 years is a very hard schedule for that.
You can send the unmanned parts with current technologies, but the manned part depends heavily on the development of adequate shielding and/or adequate NTRs to make effective use of the reaction mass the spacecraft carries.
If shielding is developed before, you could even make the whole thing easier - you put a shielded habitat in an Aldrin cycler orbit and just send crew and supplies (and spares for the habitat) to rendezvous with it when it passes by Earth leave the habitat when it's time to enter Martian orbit. The trip is longer, but it's easier if you don't have to give the whole habitat the required delta-V.
Yes, it would be wisest to send at least two trips, so that equipment can be ready for the crew when they arrive. (Especially if you're making return-trip fuel from local resources.)
Radiation is a problem for a manned mission to Mars, but I understand the numbers work out to less lifetime risk of cancer than smoking. (So send former smokers without any cigs and you've improved their expected lifespan.)
Take a look at http://en.wikipedia.org/wiki/Mars_Direct and its descendants. Many of the problems have been solved, with an expected 10-year timeline.
You would have to send a Mir-sized object (in order to accommodate humans on their way up) on a transfer orbit to Mars, with the required shielding and supplies to keep the crew alive for at least 6 months, plus fuel for braking when they need to inject themselves into Martian orbit (or, at least, to circularize the orbit after atmospheric braking). Doing this with chemical rockets is possible, but operational NTRs would decrease the time for the trip and expose the crew to less radiation.
I am not sure the numbers for radiological risk are that low. Besides, the longer they stay en-route, the higher the risk from a CME catching them. If they are on Mars, at least they have a planet to shield them 50% of the time.
Of course, getting /back/ from Mars is an entirely different proposition altogether. It's pretty likely the first man on Mars will be taking a one-way trip (and there are definitely people willing to do this).
Here's the article: http://buzzaldrin.com/a-one-way-trip-to-mars/
And it's not even that there might never be a chance for return; just that it's not part of any of the current planning. Would be attractive to the same sorts of people who in the 14th and 15th centuries sailed in wooden ships to the "new world"
http://journalofcosmology.com/Contents12.html
Last year the journal of cosmology had an issue devoted to problems related to Mars. There are many people who believe putting people on Mars is completely feasible. The most well known is maybe Robert Zubrin, advisor to NASA, who has a fairly well thought out plan ("Mars Direct") how to establish an outpost on Mars by a series of trips that are all within our current technological abilities, i.e. they don't require experimental propulsion systems. He has also written a very good book on the topic.
> Last year the journal of cosmology had an issue devoted
> to problems related to Mars.
http://www.amazon.com/Case-Mars-Plan-Settle-Planet/dp/068483...
Strongly recommended for all areophiles.