Or how about this radical idea. Drop the abort capsule altogether. I've argued this before, but the idea seems to be very ingrained in people, almost like the idea of landing a shuttle with wings "horizontally" on Mars. Both ideas make just as much sense, IMO. (In other words, not much sense)There is no place to abort to when landing on or taking off from Mars. If you find launch abort essential for Earth departure, shuttle people up while the MCT is in LEO being refueled.
That approach doesn't really work to maximize the rest of the vehicle.EITHER:The MCT launches full of fuel and has lots of delta V, which maximizes the payload mass fraction to orbit, but has a TWR too low to use for launch abortOR:[The MCT launches empty of fuel and has high TWR, but with low enough delta V that part or all of the BFR has to come close to, or reach, orbit. This lowers payload mass fraction by a large amount, or for a fixed payload makes the BFR required substantially larger.OR:The MCT launches with an order of magnitude more engine power than it will require for the rest of the mission, which is retained as waste mass throughout the rest of the mission, reducing space for other payload, or increasing launch requirements, by a large factor.
That approach doesn't really work to maximize the rest of the vehicle.
I ran across this MCT speculation/article, from the French chapter of the Mars Society: (my apologies if this has already been discussed)ANALYSIS OF A CONCEPT IN MARCH COLONIZATION TRANSPORTATION (MCT) LAUNCHES TWO [google translation]http://planete-mars.com/analyse-dun-concept-mars-colonization-transport-mct-a-deux-lancements/If you have the chrome browser, it will automatically translate the site for you.Here are some interesting images from the MCT architecture of this article:Image 1: Two MCT's docking in LMO for propellant transferImage 2: Launch abort module interiorImage 3: Launch abort module from behindImage 4: MCT landed horizontally on MarsImage 5: MCT interiorImage 6: BFR baseImage 7: BFR/MCT stackIn is an interesting concept, but I'm not sure that horizontal landing is practical. And their MCT seems to be lacking any kind of engines for propulsion.
BTW, here is a link to the author's (Richard Heidmann) previous articles on the subject: http://planete-mars.com/author/heidmann/He has really gone all in on the horizontal landing idea... Anything else doesn't seem to enter his mind as a possibility.
Quote from: Burninate on 10/02/2015 07:57 amThat approach doesn't really work to maximize the rest of the vehicle.I don't see it that way. I already stated that it will not be able to speed away from an explosion without warning. But it can separate from a failing first stage with shut down engines. Being heavy it would have to burn a lot of fuel before it can land. There is that one point that it will not have enough time to go through a lengthy precooling period. That's why I asked if Raptor can be kept in a state ready for ingnition throughout launch.
Or how about this radical idea. Drop the abort capsule altogether. I've argued this before, but the idea seems to be very ingrained in people, almost like the idea of landing a shuttle with wings "horizontally" on Mars. Both ideas make just as much sense, IMO. (In other words, not much sense)There is no place to abort to when landing on or taking off from Mars. If you find launch abort essential for Earth departure, shuttle people up while the MCT is in LEO being refueled.At some point you've got to put "big boy pants" on if you want to go to Mars. Or roll a hard six. Or name your own analogy.
First crew sizes are likely to be quite small - under 15. So will fit into a couple of Dragon 2.We've been told that payload back is ~ 25% of payload there, so ~ 25 tonnes. It is really hard to fit an abort system (capsule?) + hab for 100 (or even 15) into 25 tonnes - even if they return dry and empty.Later flights might use an optimised crew MCT.
That approach doesn't really work to maximize the rest of the vehicle.EITHER:The MCT launches full of fuel and has lots of delta V, which maximizes the payload mass fraction to orbit, but has a TWR too low to use for launch abortOR:The MCT launches empty of fuel and has high TWR, but with low enough delta V that part or all of the BFR has to come close to, or reach, orbit. This lowers payload mass fraction by a large amount, or for a fixed payload makes the BFR required substantially larger.OR:The MCT launches with an order of magnitude more engine power than it will require for the rest of the mission, which is retained as waste mass throughout the rest of the mission, reducing space for other payload, or increasing launch requirements, by a large factor.
Nice concept. But quite frankly, I like the concept developed in L2 better. Hyperion et al. seem to have a better handle on the subject. Its very interesting to the development though and only good things can come from independent groups tackle the same problem.
A top mounted thruster system like this would be inherrently stable, unlike landing on a tail engine (F9 booster)....like a helicopter is stable with it's thrust up on top and it's mass hanging below it.
Nice concept. But quite frankly, I like the concept developed in L2 better.