Jim has shown that a 10m heat shield can be folded in half to fit a 5m EELV.
Quote from: spacenut on 09/26/2011 05:19 pmJim has shown that a 10m heat shield can be folded in half to fit a 5m EELV.Only if it's a disk. The DRM 5.0 aeroshells were biconics and 10 m across.
So air braking might be just as costly as propulsive braking or landing?
IMO, the cheapest and fastest way to Mars would be a simple (as in pretty much fully propulsive), reusable (cheaper since it can be used over and over again), all chemical (faster than SEP), architecture that was evolved from previous spacecraft a la the ULA Lunar plan. Zegler et al. say their DTAL lander could easily be evolved for use on Mars. My own BOTE calculations suggest that a stretched tank DTAL lander (i.e, an ACES-71) equipped with a heat resistant titanium hull (so it could withstand the full 1 W/cm2) could land fully propulsively--no ballutes, parachutes, or heat shields required.Then the ULA MTV has a crew capacity of 16 and a nominal delta v of 11 km/sec. If there was refueling capability in Mars orbit, the ULA MTV could cut the 1-way transit times by over half compared to the Hohman transfer; if refueling was deemed impractical (probably the case for the initial missions), it would have enough delta v to do a round trip taking Hohman transfers. Again, this would all be fully propulsive--no heat shields required. The 7 hundred tonnes of propellant would only cost about $350 million, if refueled at L2 (with Lunar derived LH2/LO2). See, so the whole thing would be faster and cheaper, since it would be a simple evolution from the ULA Lunar architecture, which is itself a simple evolution from the Centaur 3rd-stage architecture.
Personally, I feel like the cheapest and most efficient way to go to mars has to make maximum use of ISRU capabilities.
I am also skeptical of the idea that a mars mission needs to bring much scientific hardware. I am not as enthusiastic about martian life as I am about, say, finding mineral ores or other industrial materials that humans can use.
We must make as our goal the settlement of mars. That is also why I favor a 1-way mission (which would also free up a lot of mass).
Quote from: constantius on 02/17/2012 10:42 pmPersonally, I feel like the cheapest and most efficient way to go to mars has to make maximum use of ISRU capabilities. Are you talking about the Moon or Mars or both?
Without going through the thread, can I just point out that the Apollo spacecraft could have gone to Mars, so any future Lunar hardware can probably be modified to being Mars capable hardware. So who's in in the best position to get men back to the Moon? Probably SpaceX.
Secondly, there is, of necessity, a fundamental difference in design between a Mars lander and a moon lander...
If you want to do ISRU on Mars, you might as well go for highest Isp LH2/LO2. ...
Quote from: Warren Platts on 02/21/2012 12:25 pmIf you want to do ISRU on Mars, you might as well go for highest Isp LH2/LO2. ...Why? CO/O2 is really easy.
1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.
Quote from: Robotbeat on 02/21/2012 04:45 pm1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.C. You need water anyway, so going with CO/O2 isn't going to get you out of that one. Therefore, you are merely adding an extra, unnecessary layer of duplicated effort that vastly complexifies the whole project.