Will MCT use methalox for all parts of its Earth-Mars trip? If so, then is that volatile methalox supposed to last all the way until the Mars EDL burn? Or will hypergolics be used for the ending burn instead?Likewise, what about for return trip back to Earth? There likely won't be a way to manufacture traditional hypergolics on Mars for the return trip, so it sounds like Methalox will need to survive from Mars all the way to Earth.How will that methalox be preserved across the entire journey?Will MCT use the same very-low-temperature cryo approach as Falcon FT?
Quote from: cscott on 05/05/2016 02:02 amThere is speculation that MCT might be built/tested/flown all at the Cape. There is no way SpaceX would do that unless the range is ready to support daily flights.
There is speculation that MCT might be built/tested/flown all at the Cape.
I think this counts as MCT speculation:While reading this:Quote from: guckyfan on 05/05/2016 04:59 amQuote from: cscott on 05/05/2016 02:02 amThere is speculation that MCT might be built/tested/flown all at the Cape. There is no way SpaceX would do that unless the range is ready to support daily flights.It occurred to me that it's *technically feasible* to build BFR and BFS at the cape and have them both self-ferry to Brownsville... in fact this is feasible from any eastern-seaboard location.Perhaps this side-steps the problem of needing a large skilled workforce in an out-of-the-way place like Brownsville.
Quote from: Space OurSoul on 05/05/2016 05:07 pmI think this counts as MCT speculation:While reading this:Quote from: guckyfan on 05/05/2016 04:59 amQuote from: cscott on 05/05/2016 02:02 amThere is speculation that MCT might be built/tested/flown all at the Cape. There is no way SpaceX would do that unless the range is ready to support daily flights.It occurred to me that it's *technically feasible* to build BFR and BFS at the cape and have them both self-ferry to Brownsville... in fact this is feasible from any eastern-seaboard location.Perhaps this side-steps the problem of needing a large skilled workforce in an out-of-the-way place like Brownsville.Shipping large rockets by sea is a problem that has been solved many times. It's not only *technically feasible* but SOP.
(Note that all Musk has ever said about the Moon is, paraphrasing, "it's on the way, I guess we should look at how to get there, but it's not anything like a goal of the architecture to be able to go to the Moon".)I, for one, would like to see a new interplanetary transportation architecture be designed to support more than one possible destination, I guess...
Regarding the BFS TPS, I always thought the best place to put it was on the bottom.[...] and it would enable [the] simplist cargo/passenger stowage.
If we put the TPS on top,
I think it could even be inflatable.
(or make a big slow target for a helicopter mid air grab.)
Quote from: CyclerPilot on 05/06/2016 03:28 amI think it could even be inflatable.Doubtful. It would need to be repacked on Mars to allow for the Earth-return EDL. Or you'd need to carry two expendable inflatable heat-shields (one for Mars, one for return to Earth.)(It just doesn't fit the typical SpaceX architecture.)
Quote from: CyclerPilot on 05/06/2016 03:28 amRegarding the BFS TPS, I always thought the best place to put it was on the bottom.[...] and it would enable [the] simplist cargo/passenger stowage.What's the reasoning for that?
I've assumed if the TPS isn't at the bottom, it'll be down the ventral side. With a biconic or lifting-body forward shape, allowing lift/drag type EDL, extending the deceleration, reducing the amount of supersonic retropropulsion required, and lowering the final speed before the landing burn, both reducing fuel demand.It also allows a longer glide, improving safety for suboptimal entry timing. (For eg, uneven upper atmosphere means the BFS decelerates earlier than expected, losing speed before reaching the intended landing area. BFS lands short, necessitating a rescue scenario. With a longer glide, you can stretch the descent.)
Doubtful. It would need to be repacked on Mars to allow for the Earth-return EDL. Or you'd need to carry two expendable inflatable heat-shields (one for Mars, one for return to Earth.)...(It just doesn't fit the typical SpaceX architecture.)...Errr, no. IMO, ULA's engine pod for Vulcan will end up being be too large for helicopter aerial recovery, the BFS would be too large for capture even by a giant transport plane.
what do you think about tripropellant engine for long duration missions?i know that lox+RP+H2 gives some good results but could lox+methane+H2 do that?for example (engine is the same): for BFR first stage: start on methane 66-75% + 33-25% H2 for best thrust, then high isp flight on pure H2 and landing on pure methane (no need for high insulation for H2)for MCT: start to mars on pure H2 and landing on mars on pure methane. start from mars on methane or mix if it possible to produce H2. landing on earth on pure methane.
Matt, that's exactly what a common bulkhead propellent tank design does. Look up the Saturn V second stage tank common bulkhead. http://www.alternatewars.com/Games/KSP/Tut2/KSP_Tutorial_2-6.htm