A more plausible scale-up would use a 12 m diameter landing capsule, which could be sent to Mars by a single launch of a 200-300 ton-to-LEO rocket. Trans-Mars mass would be around 60-90 t (to stay in the 0.8t/m^2 range that is talked about), and the surface payload about half that. This would align with Zubrin's suggestion that the initial trans-Mars habitat should stay on Mars as crew housing. This also allows stockpiling supplies on Mars prior to crew arrival, to make the Mars base the "second safest place in the solar system" (to quote an old Zubrin statement). A crew capsule also allows implementation of a launch escape system.
A crew capsule also allows implementation of a launch escape system.
With the upcoming debut of the Falcon Heavy, there is also a chance that SpaceX will start with a smaller 3-core ITS variant, to allow a set of 9.5 m diameter cores to loft the same 300 tons-LEO (90-100t to Mars). This suggestion would make Zubrin happier
I would add 1 more required technology improvement to the list.5) Long term storage of deep cryogenic propellants1) Full and rapid reuse2) orbital refueling3) Mars ISRU for methalox4) lifting entry and hypersonic retropropulsionSent from my XT1565 using Tapatalk
Is LOX? Kinda need some of that too.Cislunar shouldn't be defficult, but Mars would be more demanding.Shading, and insulation are part of the answer.Sent from my XT1565 using Tapatalk
Storing a small amount of methalox in what are basically Dewars inside the main tanks should be pretty straightforward.If SpaceX were trying to store methalox in the main tanks, I would say that's pretty low TRL. But storage in small vacuum lined tanks has been proven in operational flight systems.Both Shuttle and Apollo demonstrated LOX storage for weeks on orbit. Shuttle even demonstrated cryo LH2 storage for up to about a month at -420 degrees F for the fuel cells.
Quote from: envy887 on 05/29/2017 08:45 pmStoring a small amount of methalox in what are basically Dewars inside the main tanks should be pretty straightforward.If SpaceX were trying to store methalox in the main tanks, I would say that's pretty low TRL. But storage in small vacuum lined tanks has been proven in operational flight systems.Both Shuttle and Apollo demonstrated LOX storage for weeks on orbit. Shuttle even demonstrated cryo LH2 storage for up to about a month at -420 degrees F for the fuel cells.Interesting how rarely TRL* comes up in SpaceX discussions... What TRL was supersonic retro-propulsion when they did it?3D printed engines and engine parts?Red Dragon's EDL profile?Pusher abort system?Landing legs on an orbital-class booster?ASDS?Full flow staged combustion engines? ...using methlox?Refueling cryogens on orbit?Landing the whole thing?ISRU... on Mars?Don't see much in the way of entire phases being devoted to 'risk reduction' during their development cycle either.They aren't afraid to do new things if they need to be done -- maybe ignoring TRL is their key to success. Kinda OT for this discussion, but IAC v0.1 didn't dwell on low TRL as a barrier and expect neither will v0.2.* Has Elon Musk ever actually said 'technology readiness level' in public? (He'd not say TRL because he hates acronyms.)
I don't expect development of long term on orbit main tank cryo storage because it's not critical to ITS.
Quote from: envy887 on 05/29/2017 11:31 pmI don't expect development of long term on orbit main tank cryo storage because it's not critical to ITS.It is though, for varying definitions of long term. ITS will need to be refueled over a handful of tanker flights which could take a bit of time