Lot of talk here seem to be about a single vehicle that will launch from earth, land on mars, and then return to earth.
Musk isn't one to waste things, surely he will be using Red Dragon vehicle to handle the Mars orbit to ground bit and the IST will just handle the Earth to Mars bit?
It seems a bit risky to me to design a vehicle capable of being launch from earth with dozens of passengers and all their supplies sent to land to Mars and expect the same vehicle to do the reverse again.
Dragons might make excellent Star Wars style escape pods for the MCT, lifeboats able to save the human cargo...
An affordable, fully reusable HLV changes the rules of the game.
If there was a demand of 100-200mT/yr propellant in LEO, then a very small RLV could be profitable. No sufficiently large markets seem likely for Falcon 9 sized payloads in the near future.
SpaceX may decide to bite the bullet and dev. an F-1 class version of Raptor for BFR to avoid an N-1 type design and to carry over the octaweb design heritage of F9. Raptor is said to be highly scalable so there is no reason whatsoever that several sizes of it for different tasks can be dev. maybe except for dev. cost.EM did say the plan do use only one size of Raptor throughout the BFR/MCT architecture may change during his AMA in January 2015.I am sure EM knows what happening to the N-1 and I can't imagine him being that stupid.We will find out on Tuesday.
http://m.imgur.com/a/87OOT- Was this proposal, by 'Coborop' on Reddit, ever discussed in this thread?
Quote from: DJPledger on 09/25/2016 08:13 amSpaceX may decide to bite the bullet and dev. an F-1 class version of Raptor for BFR to avoid an N-1 type design and to carry over the octaweb design heritage of F9. Raptor is said to be highly scalable so there is no reason whatsoever that several sizes of it for different tasks can be dev. maybe except for dev. cost.EM did say the plan do use only one size of Raptor throughout the BFR/MCT architecture may change during his AMA in January 2015.I am sure EM knows what happening to the N-1 and I can't imagine him being that stupid.We will find out on Tuesday.N-1 failed due to fuel system problems that would not exist under present engineering conventions.Number of engines does not increase risk. Indeed, there's an argument that a high number of engines reduces risk.It's usually safe to assume that SpaceX isn't "stupid", they're better informed and acting under better data.
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.Going with (a)2) Number of Raptor Engines on BFR (1st stage)< 30, my best estimate is 25-27 if thrust stays close to 230 tonnes range3) Diameter of BFR (1st stage)Range 12.5m-15m, best estimate 15m 1st stage4) Total Raptor 1st stage thrust (sl)60 Meganewtons and T/W > 1.35) 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 designBest guess is (a)6) 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) OtherGoing with (c), definitely no horizontal landing7) 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(a) 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 road(c) strongly favorCan anyone think of more/better questions?
Quote from: GORDAP on 09/12/2016 06:32 pm1) 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.Going with (a)2) Number of Raptor Engines on BFR (1st stage)< 30, my best estimate is 25-273) Diameter of BFR (1st stage)Range 12.5m-15m, best estimate 15m 1st stage4) Total Raptor 1st stage thrust (sl)60 Meganewtons and T/W > 1.35) 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 designBest guess is (a)6) 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) OtherGoing with (c), definitely no horizontal landing7) 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(a) 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 road(c) strongly favorCan anyone think of more/better questions?Predict Musk will miss 1st crewed landing by >= 3 synods5-6 Rvacs on BFS stage 2Raptor sea level will have 10s of tonnes thrust more than the 230 tonnes mentioned by ElonEntire BFR/BFS GLOW masses under 5.000 tonnes; my estimate ~4,500Height of BFR/BFS stack under 120m; my estimate <100mCargo version, tanker version, crewed version of BFS1st crewed landing on Mars 8-12 humans plannedJust over 48 hours until Musk makes fools of us
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.Going with (a)2) Number of Raptor Engines on BFR (1st stage)< 30, my best estimate is 25-273) Diameter of BFR (1st stage)Range 12.5m-15m, best estimate 15m 1st stage4) Total Raptor 1st stage thrust (sl)60 Meganewtons and T/W > 1.35) 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 designBest guess is (a)6) 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) OtherGoing with (c), definitely no horizontal landing7) 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(a) 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 road(c) strongly favorCan anyone think of more/better questions?
It only takes one engine to explode out of 30 to bring down an LV. I believe this happened to at least one of the N-1's. Anyone including SpaceX even attempting something like the N-1 beggars belief. The more engines you have the greater the risk of one of them exploding causing catastrophic LV failure. 5-9 engines is the optimum no. on a 1st stage to strike a balance between the risk of engine explosion and good engine out capability for benign engine failures. Lets hope that SpaceX have learned the N-1 lesson and the BFR design we should see on Tuesday will have much less than 30 engines on it.
Up-feed plumbing of propellant to Roc makes this way too complex & heavy. Cosine losses and reduced engine performance by running stage 2 Roc at sea level for Earth launch a bad tradeoff. Just add engines on 1st stage Sling until it's big enough to launch upper stage.