BFS without refueling should able to a free return circumlunar mission with a small payload. No need for a tanker version or even a second spacecraft for that.I think BFS will only have a payload adapter (passenger hab or cargo hold integrated as needed), so a tanker would only differ in tank size and might not be necessary at all.
Quote from: envy887 on 06/11/2016 03:33 amBFS without refueling should able to a free return circumlunar mission with a small payload. No need for a tanker version or even a second spacecraft for that.I think BFS will only have a payload adapter (passenger hab or cargo hold integrated as needed), so a tanker would only differ in tank size and might not be necessary at all.BFS is likely designed to reach LEO with little fuel remaining. Refueling is essential.This is not one-shot rocketry.
Quote from: AncientU on 06/11/2016 01:06 pmQuote from: envy887 on 06/11/2016 03:33 amBFS without refueling should able to a free return circumlunar mission with a small payload. No need for a tanker version or even a second spacecraft for that.I think BFS will only have a payload adapter (passenger hab or cargo hold integrated as needed), so a tanker would only differ in tank size and might not be necessary at all.BFS is likely designed to reach LEO with little fuel remaining. Refueling is essential.This is not one-shot rocketry.BFS would necessarily be able to reach LEO with lots of fuel, just not also with a maximum payload. So the point stands.But refueling will be needed early on.
Dry mass likely to be much less than the payload. ...
As large as its likely to be, and with baked in habitation, could a BFS be considered a lunar "base" if left in place? Guessing it depends on ease of egress/ingress, crew rotation landers and power generation, but still.
Quote from: docmordrid on 06/11/2016 04:32 pmAs large as its likely to be, and with baked in habitation, could a BFS be considered a lunar "base" if left in place? Guessing it depends on ease of egress/ingress, crew rotation landers and power generation, but still.If Tiangong can be considered a space station, then sure, why the heck not?
Quote from: Robotbeat on 06/11/2016 05:40 pmQuote from: docmordrid on 06/11/2016 04:32 pmAs large as its likely to be, and with baked in habitation, could a BFS be considered a lunar "base" if left in place? Guessing it depends on ease of egress/ingress, crew rotation landers and power generation, but still.If Tiangong can be considered a space station, then sure, why the heck not?I doubt the hab will be baked in, which probably helps. Thermal control during the month long day/night cycle is an issue though.
Musk quoted in the Washington Times article:"Being a product scheduling professional, my mind started backing off that date all of the physical tasks that needed to happen in just 6 short years. …...And if we're talking MCT, we have to assume the BFR will also be under development. That is a lot. I would imagine we'll get a sense of the schedule of events when Musk unveils more details in September, and as he says in the article:
Break ground on launch site by 2018/2019.
I think that lots of guys have shared your skepticism about the timeline. But do you think that slippage of one synod would not be OK for this grand plan? Meaning, that he's shooting for the 2022 synod but expects the next one to be achievable.
From a leadership standpoint, it seems that this plan might be very effective to motivate the "true believers" to put in their 100%. He's got a real strong cadre with world-class skills, but they need a clear goal. If he sets a goal for 2022, they'll bust their a**es to make it happen. If that comes to pass, GREAT, but if it slips for whatever technical reasons, won't this still be a winning situation? All of them will understand why thy didn't *quite* make it for that synod, and they'll be stoked to make it happen for the next one.
Newer refined model for BFR/BFS. Spreadsheet attached. BFR & BFS MODELS: MCT as 2nd Stage with 100 Metric Tons CARGO BLUE: Enter parameter variableS1 Avg ISP Sea L to MECO 335 S2 vac ISP 380 Raptor sea level thrust KLB & mT 518 235Rvac thrust KLB & mT 559 254S1 Dry Wt % 4.5% BFR 1 BFR DIA 15.0 mMCT BFS Dry Wt & Cargo 225 mTS2 Dry Mass 125 mTPropellant for S2 BFS Landing 30 mTTotal Mass to LEO 255 mT1st Stage Propellant Tank Length 18.0 mS1 Propellant Volume 3179 m3Propellant Mass 3371 mTS1 Dry Wt % 4.5% S1 DRY Weight 159 mTS1 Total Weight mT 3529 mTS! Dry Wt Delta V (No 2nd stage) 10.2 Km/sec Rocket EquationStage One Full Load Delta V 3.35 Km/sec Rocket EquationRTxx Propellant 70 mTRTxx Delta V @Minimum Load 1.20 Km/sec Rocket EquationEst S1 Gravity Loss 0.9 Km/secEst S1 Velocity @ Burnout 2.45 Km/sec2nd Stage Propellant Tank Length 7.5 mPropellant Volume 1,325 m3Propellant Mass 1,404 mTS2 Mass w/MCT 1,629 mTS2 Mass w/MCT 3.6 Million LBSCalc # Rvac Raptor Eng 5.01 0.78Stage 2 Thrust mT 1271 Stage 2 Thrust 2.8 Million LBSStage 2 Km/sec 6.91 Km/sec Rocket EquationStage 2 Wet to Dry Mass Ratio 12.2 S1 + S2 Total Delta V 9.4 Km/secTOTAL WT mT 5,159 mTTOTAL WT LBS 11.4 Million LBSTHRUST Needed LBS 14.0 Million LBSTHRUST Needed mT 6345 THRUST Needed MegaNewtons 62 1st Stage T/W @ Takeoff 1.23 1st STAGE # ENG 27 LEO Mass Fract 4.4% %LEO Wet to Dry Mass Ratio 23 F9 v1.1 25/1 MuskMCT Cargo Hold length 10 mMCT Cargo Vol m3 1766 m3 Eng 16+8+3=27 Outer Ring, Inner Ring, Central Engs NOTE 1: S1 Km/sec + S2 Km/sec must ~9Km/sec for LEO with grav losses NOTE 2: Rocket Equation