...but again this doesn't 'feel' minimalistic.
We refer to this architecture as minimal because it would minimize large new development efforts and rely largely on elements currently being developed or planned by NASA, such as SLS, Orion, a deep space habitat, and a 100-kWe-class SEP tug.
I like the idea of using hypergolics for the lander/ascent vehicle but for two things. Firstly it does push the mass a lot relative to methalox. And using SEP all the way to Mars.
Ok just so I can get my head around it. My understanding is that their lander is 23 tonne total landed mass. That includes the ascent vehicle as only a portion of that 23 tonnes?Also, what Isp were you counting on for the hypergolics, and do you know what figure they were working on?
This seems very realistic to me, with the lander stages being the only scratch development (the use of hypergolics in everything would require new EUS development as well, but I don't see why already in-dev or extant upper stages couldn't be used).
I doubt this would actually save money in the long run over development of additional assets, especially prop depots and ISRU, and I'd be tempted to see about resizing some of the payloads to fit on Falcon Heavies rather requiring SLS for everything, but this plan seems very practical in catering to existing projects, and may therefore be more likely to find congressional support.
Thirdly I do not agree with exposing crew who have been in weightlessness for 6-8 months to a nominal 6.4g on reentry.
That suggested to me that what actually lands on mars is 23 tonnes. Yet the lander is quoted as 56 tonnes.If so what they are saying is that they hope to land a 56 tonne mass on Mars with a 75 tonne entry mass. That's a 75% ratio of landed mass to entry mass. That's so high that I assumed I was reading it wrongly.How much is a 12 metre heat shield and backshell going to mass? They said it was a scaled up version of the MSL heat shield but its nearly 3 times larger. Possibly 7 times more massive. Then how much landing propellant do they need? Edit: If you assume that the lander has to brake from Mach 2 and then have a tiny bit left for maneuvering then you figure it needs 0.7Km/s worth of thrust. With the Isp of 340 that means a mass ration of 1.23. So the 56 tonne landed mass (dry) equates to 68 tonnes with fuel. That leaves 7 tonnes for absolutely everything else. And no margins.With 4.1Km/s the 23 tonne ascent vehicle would have a mass of 6.8 tonnes dry (why so high?).
Quote from: redliox on 06/30/2015 08:01 am...but again this doesn't 'feel' minimalistic.You must have missed that part: Quote We refer to this architecture as minimal because it would minimize large new development efforts and rely largely on elements currently being developed or planned by NASA, such as SLS, Orion, a deep space habitat, and a 100-kWe-class SEP tug.By that definition it certainly is a minimalist architecture. No inflatable heat shield, no ISRU for ascent fuel, no methalox propulsion/storage (all hypergolics), 100kw SEP.At least the most minimalist architecture I've ever come across.
Quote from: Oli on 06/30/2015 11:25 amQuote from: redliox on 06/30/2015 08:01 am...but again this doesn't 'feel' minimalistic.You must have missed that part: Quote We refer to this architecture as minimal because it would minimize large new development efforts and rely largely on elements currently being developed or planned by NASA, such as SLS, Orion, a deep space habitat, and a 100-kWe-class SEP tug.By that definition it certainly is a minimalist architecture. No inflatable heat shield, no ISRU for ascent fuel, no methalox propulsion/storage (all hypergolics), 100kw SEP.At least the most minimalist architecture I've ever come across.True regarding technology, but I also look at the chart itself. Any 7 year old space camper would be able to say "It looks complicated." Apollo required one launch per mission, Mars Direct two, Mars Semi-Direct three; this "simple" setup wants six. In back of my mind when I figure the amount of SLS launches and Congressional patience together...you'll hear a long riiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiight. Also, presuming Trumph becomes president, I picture him pointing a finger at the NASA administrator (Bolden or otherwise) and delivering his classic "You're fired!" with extreme prejudice.
NASA's Mars DRA 5.0 from 2009 had eight launches, seven Ares V and one Ares I.Boeing's "Mission to Mars in Six (not so easy) Pieces" study presented in 2014 has five SLS launches. It uses an EML-2 gateway station.So six SLS launches isn't bad, especially since it doesn't require a gateway station.Mars Direct and Semi-Direct are too minimalist.