My predictions are still going against the grain, I think we will see mostly BFR details with only modest information on the actual mars transit and landing and what ever details are revealed of that phase of the mission will be subject to change as SpaceX actually gets landing experience on Mars, it's too soon to completely commit to the mode or design of the mars landing vehicles at this time.
BFR will be narrower then the 15m diameter many have speculated, I think closer to 12m diameter as the thrust density of the Raptor engine will be high and a narrower vehicle makes for a lighter more efficient thrust structure to transmit the thrust of many engines to the tank side walls and makes for lower air resistance on assent as well. The first stage will be recovered right from the first orbital flight and will be well tested on it's own in sub-orbital flights with a mass-simulating 2nd stage used for testing.
A recoverable second stage with vacuum raptor engines, probably 6 so it has engine out capability, will be used along with a conventional payload fairing to launch large payloads of high volume and make the BFR a direct competitor to SLS. This 2nd stage will also act as the LEO propellant tanker with just the attachment of a minimal nosecone. Recovery of the 2nd stage still be slightly experimental at the time the first orbital launches and the fist few launches will be refine the recovery process for the 2nd stage and several may be lost in the process. The 2nd stage will orbit the Earth one or more times before recovery and might not land at the launch site.
Overall vehicle height is be over 200 ft at the top of the 2nd stage, with payload fairing around 300 ft. Any mars bound spacecraft will be introduced several years after BFR itself is flying and will not fly the super-direct flight plan of departing from LEO directly to mars surface and then from Mars surface directly back to Earth surface, this requires too much delta-V and propellant production on Mars, rather their will be a refueling step somewhere between likely in a high Earth orbit and/or high Mars orbit.
Agree completely. MCT/BFS will be more conceptual and under development than big 1st stage....Anyone else have predictions/updates?
How short could you plausibly make the full-diameter BFR? Im just thinking a lot shorter and symmetrically remove some engines.
Quote from: philw1776 on 09/11/2016 03:18 pmAgree completely. MCT/BFS will be more conceptual and under development than big 1st stage....Anyone else have predictions/updates?My totally uninformed and unsubstantiated pet hope is a sudden plan for a falcon heavy replacement:Quote from: KelvinZero on 07/29/2016 10:45 amHow short could you plausibly make the full-diameter BFR? Im just thinking a lot shorter and symmetrically remove some engines.If it is only needs 12 meter diameter instead of 15 that is great. However dumb my idea was at 15m, it is probably a bit less dumb at 12m
Thx 4 reply philw1776 I have a few counter and clarifying points.Lastly I believe it may be possible to send tankers from Earth to a high mars orbit, have them offload propellants and still return to Earth orbit either via chemical propulsion or SEP so all vehicles are recovered. This would allow the Mars landing and relaunch vehicles to be much lighter at liftoff from Mars, using something like 1/3rd as much propellant, then refill in orbit and make a fast return to Earth. The exact details of how and where refueling occurs aren't clear yet but what I'm sure of is that the direct return approach is not viable, the fixation many have with it is analogous to the fixation on direct earth return in the early days of Apollo, it's attractive for it's simplicity but it a bridge too far in a lot of engineering areas.
Thx 4 reply philw1776 I have a few counter and clarifying points.Planning for future upgrades to BFR is interesting, but I'm doubtful that a vehicles diameter is made larger then necessary to allow for the insertion of extra engines at a later date. First the extra engines and thrust would require a complete redesign of the plumbing structures and thrust structures which is a significant part of the first stages total design.
As the Big Reveal is nearly upon us (hopefully!), I think that someone (not me) should generate an official Mars MCT Architecture Prediction contest. This would be composed of a list of questions with multiple choice answers, with a fixed value for each question. Prizes TBD.One problem is that L2 members may have 'insider information' on this topic. So I guess they will have to be just guided by their own conscience as to their level of participation.Anyway, I'll kick it off with a few suggested questions (but will be happy for someone else to officially take this over and come up with the canonical list, as well as being judge, jury, etc.)1) Overall Launch Architecture a) MCT is composed simply of a BFR 1st stage and BFS 2nd stage/spacecraft b) Boost phase consists of 2 stages, which put the BFS into orbit c) Other: 3rd stage, 'half' stages, drop tanks, etc.2) Number of Raptor Engines on BFR (1st stage)3) Diameter of BFR (1st stage)4) Total Raptor 1st stage thrust (sl)5) LAS Architecture a) No LAS - BFS is the escape mechanism b) Traditional LAS - above BFS and is nominally jettisoned during launch phase c) BFS contains smaller 'ejection pod' where humans reside during launch d) Other, non-traditional LAS design6) Shape and Landing Mode of BFS a) Capsule (perhaps elongated), w/ TPS on base b) Cylindrical or biconic - horizontal landing c) Cylindrical or biconic - vertical landing d) Other7) Mars and Earth return a) BFS does direct entry into Mars and Earth atmosphere b) BFS does orbital capture before performing entry burn and landing c) Same as b, but upon Earth return, stays in orbit for next synod Use of non-chemical thrust a) Not part of the plan b) Will use SEP for some/all of the big transits c) All chemical for now, but plans to incorporate SEP down the roadCan anyone think of more/better questions?
Quote from: Impaler on 09/11/2016 10:03 pmThx 4 reply philw1776 I have a few counter and clarifying points.Lastly I believe it may be possible to send tankers from Earth to a high mars orbit, have them offload propellants and still return to Earth orbit either via chemical propulsion or SEP so all vehicles are recovered. This would allow the Mars landing and relaunch vehicles to be much lighter at liftoff from Mars, using something like 1/3rd as much propellant, then refill in orbit and make a fast return to Earth. The exact details of how and where refueling occurs aren't clear yet but what I'm sure of is that the direct return approach is not viable, the fixation many have with it is analogous to the fixation on direct earth return in the early days of Apollo, it's attractive for it's simplicity but it a bridge too far in a lot of engineering areas.Gwynne has said, "We're looking at SEP" so this is a possibility.On the downside if it's SEP, it is yet another vehicle to be developed and tested.I haven't looked deeply at delta Vs, masses and run the rocket equation to comment cogently on the feasibility of SEP, etc. tankers to HMO & back. I'm certain that SX has done so in their architectural bakeoffs.
Quote from: GORDAP on 09/12/2016 06:32 pmAs the Big Reveal is nearly upon us (hopefully!), I think that someone (not me) should generate an official Mars MCT Architecture Prediction contest. This would be composed of a list of questions with multiple choice answers, with a fixed value for each question. Prizes TBD.One problem is that L2 members may have 'insider information' on this topic. So I guess they will have to be just guided by their own conscience as to their level of participation.Anyway, I'll kick it off with a few suggested questions (but will be happy for someone else to officially take this over and come up with the canonical list, as well as being judge, jury, etc.)1) Overall Launch Architecture a) MCT is composed simply of a BFR 1st stage and BFS 2nd stage/spacecraft b) Boost phase consists of 2 stages, which put the BFS into orbit c) Other: 3rd stage, 'half' stages, drop tanks, etc.2) Number of Raptor Engines on BFR (1st stage)3) Diameter of BFR (1st stage)4) Total Raptor 1st stage thrust (sl)5) LAS Architecture a) No LAS - BFS is the escape mechanism b) Traditional LAS - above BFS and is nominally jettisoned during launch phase c) BFS contains smaller 'ejection pod' where humans reside during launch d) Other, non-traditional LAS design6) Shape and Landing Mode of BFS a) Capsule (perhaps elongated), w/ TPS on base b) Cylindrical or biconic - horizontal landing c) Cylindrical or biconic - vertical landing d) Other7) Mars and Earth return a) BFS does direct entry into Mars and Earth atmosphere b) BFS does orbital capture before performing entry burn and landing c) Same as b, but upon Earth return, stays in orbit for next synod Use of non-chemical thrust a) Not part of the plan b) Will use SEP for some/all of the big transits c) All chemical for now, but plans to incorporate SEP down the roadCan anyone think of more/better questions?SL thrust of each Raptor on BFR.
First I find focusing on vehicle count as a measure of difficulty is a poor metric which I think has led many people astray, when the mission requires a high performance in a number of conflicting areas trying to achieve all these performance values out of one vehicle is usually far more difficult then breaking up the problem using specialized vehicle. That has been the lesson of all space travel, it's why rockets have stages, it's why the LEM rather then the command module landed on the moon and it's why I consistently foresee more complex mission modalities then the majority.
IMLEO is no longer the primary constraint
Gwynne has said, "We're looking at SEP" so this is a possibility.On the downside if it's SEP, it is yet another vehicle to be developed and tested.
Quote from: philw1776 on 09/12/2016 05:20 pmGwynne has said, "We're looking at SEP" so this is a possibility.On the downside if it's SEP, it is yet another vehicle to be developed and tested.Random thought: What about a vehicle that can do missions with small crews without SEP, but you have a plan to add SEP later (as a stage, cycler or L2 propellant tug, whatever) when you have multiple flights to spread the costs over and want closer to that 500k/passenger goal, and also to achieve that fast return to earth for immediate reuse?
Quote from: KelvinZero on 09/15/2016 09:23 amQuote from: philw1776 on 09/12/2016 05:20 pmGwynne has said, "We're looking at SEP" so this is a possibility.On the downside if it's SEP, it is yet another vehicle to be developed and tested.Random thought: What about a vehicle that can do missions with small crews without SEP, but you have a plan to add SEP later (as a stage, cycler or L2 propellant tug, whatever) when you have multiple flights to spread the costs over and want closer to that 500k/passenger goal, and also to achieve that fast return to earth for immediate reuse?Sure, just change how many tankers are used to refuel (& where) the BFS in orbit. SEP can be to push the fuel to a higher energy orbit before refueling.
Quote from: Robotbeat on 09/15/2016 01:57 pmQuote from: KelvinZero on 09/15/2016 09:23 amQuote from: philw1776 on 09/12/2016 05:20 pmGwynne has said, "We're looking at SEP" so this is a possibility.On the downside if it's SEP, it is yet another vehicle to be developed and tested.Random thought: What about a vehicle that can do missions with small crews without SEP, but you have a plan to add SEP later (as a stage, cycler or L2 propellant tug, whatever) when you have multiple flights to spread the costs over and want closer to that 500k/passenger goal, and also to achieve that fast return to earth for immediate reuse?Sure, just change how many tankers are used to refuel (& where) the BFS in orbit. SEP can be to push the fuel to a higher energy orbit before refueling.Staging fuel at EML1/2 or similar HEO with SEP would cut refueling launches from Earth by about 50% for crewed flights.SEP tugs could also put cargo landers directly into TMI from LEO, and then quickly return to LEO. That would cut refueling Earth launches for cargo flights by 65% to 80%. And there will be a lot more cargo flights than crew flights.
Elon Musk ✔ @elonmuskTurns out MCT can go well beyond Mars, so will need a new name…8:22 PM - 16 Sep 2016