Why are the SEP disposable?If they fly back to EML1/2 a second trip should be possible.
Quote from: A_M_Swallow on 09/17/2010 01:56 amWhy are the SEP disposable?If they fly back to EML1/2 a second trip should be possible.Two reasons:1. It's easier. The two rovers are sent on entry trajectories, and the lander very close to one. Therefore, it's going to take a lot of prop to get them back to Earth. The MTV has to head back towards Earth anyways, and is refueled at EML2 before departure, so it's much more justifiable to reuse.2. It's not necessary to reuse them. If you have full recovery, you never need more than the three initial unmanned flights. In reality, you probably end up sending another lander or rover in the future, but the unmanned flight rate after the initial mission will be very low.It's also important not to mentally merge EML1 and EML2, as dynamically, they are very different beasts. EML2 is the easiest place to leave the Earth-Moon system from, and nearly all low-thrust trajectories to escape from EML1 pass through EML2. So, best just to rendezvous at L2 and be done with it.
How about adding some instruments to the SEP stage and have it act as a deep space probe after delivering it's payload.
Quote from: Patchouli on 09/18/2010 06:25 amHow about adding some instruments to the SEP stage and have it act as a deep space probe after delivering it's payload.As I said, they're on entry trajectories, and will enter Mars's atmosphere. Destructively.Also, instruments add cost and remove payload mass; just not worth it.
It's an SEP stage. Doesn't take that much delta-v to avoid hitting Mars. Then, it enters a solar orbit
and could make its way back toward Earth. Kind of like a little cycler.
This is hard. It takes a lot of energy to turn around and head back towards Earth. Especially as the small delta v to avoid Mars means that you're going to get a wicked gravity assist in a direction away from Earth.
On the hab I wonder if ATHLETE could be integrated into the hab as the landing gear.Maybe use the sky crane system from MSL and the mobile hab can start driving after touch down.
The bigger EDL question was how to pull off a single-stage, reusable Mars lander...
Quote from: Patchouli on 09/19/2010 12:19 amOn the hab I wonder if ATHLETE could be integrated into the hab as the landing gear.Maybe use the sky crane system from MSL and the mobile hab can start driving after touch down.ATHLETE would be a good option for the unpressurized rover. The pressurized rover should probably be something more like the JSC LER, but sized for four people. A large skycrane would be useful for landing the rovers, potentially with some type of inflatable heatshield. The bigger EDL question was how to pull off a single-stage, reusable Mars lander...