Nice plan but the funding could be challenging .
Why use SEP at all when SLS Block II has the capability to push around 40 to 50 tonnes (or more with advanced LRBs) through TMI.
Quote from: floss on 07/04/2014 09:52 pmNice plan but the funding could be challenging .You should listen to the teleconference:http://spirit.as.utexas.edu/~fiso/telecon/Raftery_5-14-14/Raftery.mp3ISS had many more launches and was a larger scale than a Mars mission would require. The idea of this architecture is that it wouldn't actually need a big increase in funding, just a level of funding growing with inflation and/or the size of the economy.
The challenge though is that NASA will be funding the development of the even-larger SLS during the rest of the 2020's, so not a lot of funding is going to be available from the SLS budget. And considering that NASA has to launch the SLS no-less-than once every 12 months in order to have a safe flight cadence (per NASA), that means a lot of NASA's non-development budget will be going just to building and flying the SLS. And that doesn't even count the budget for the payloads that are supposed to launch no-less-than every 12 months, which likely will include the hugely expensive Orion/MPCV (which ESA is only building one Service Module and the parts for a 2nd).So to do this mission NASA would still need to fund:1. Development, test, and deployment and ongoing support for an EML2 Gateway. If you think supporting the ISS in LEO is expensive, try supporting a crew 1,000X farther away.2. Development, test, and deployment of a Solar Electric Propulsion (SEP) Tug, which likely will have to do some jaunts around local space in order to validate it.3. Development, test, and deployment of a Transit Hab. This can probably be checked out at the ISS, since the EML2 Gateway will have validated any "deep space" technologies by that point.4. Development, test, and deployment of a Mars Lander. This could be done with a precursor robotic rover that is the same size as the anticipated human equipment. Maybe it can pre-deploy some of the needed equipment, but obviously this would be years in advance of need. So throw in some more money for the robotic mission.5. Development, test, and deployment of a Mars Ascent Vehicle. I'm thinking this is going to take some iteration in order to get the hardware right, but even with just a single test that would be years in advance of the human version.6. More Orion/MPCV vehicles.So besides the overhead that such a program would need over a period of well over a decade (my guess), that's a lot of development, especially if it all has to be "man-rated". Within the current budget profile I think it would take multiple decades at the very least, since various experts has stated that prior to this plan that NASA would NEVER make it to Mars within it's current budget profile. And I'm not sure I see anything in this plan that changes that assessment...
Given that this programme requires the establishment of an EML2 gateway and the development and validation of a reusable (!) SEP stage in addition to all the Mars hardware, I don't see how this is more affordable than to use SLS Block II to launch payloads directly to Mars. An ongoing Mars Semi-Direct programme would require three SLS launches per window.
It doesn't /require/ the L2 gateway.