Quote from: oldAtlas_Eguy on 06/18/2015 02:39 pmFrom Statements made by SpaceX representatives:- 100mt payload delivery to Mars- 1/4 payload SSTO return to Earth from mars surface- prop density 1m^3 for 1mt (LOX and CH4)- 15m diameter vehicle (this was hited at not actually specified by SpaceX- Raptor engines 380-385 vacuum ISP 500klbfA vehicle like this results:- Vehicle structure+engines+ shield =40mt- Max propellant load 900mt- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capabilityIn order to get to Mars 6-9 tankers docking in LEO-MEO are required Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOW15m diameter and other such details have not been mentioned. Please cite your sources and put the source quote in the MCT source thread so we know exactly what was said: http://forum.nasaspaceflight.com/index.php?topic=37839.0
From Statements made by SpaceX representatives:- 100mt payload delivery to Mars- 1/4 payload SSTO return to Earth from mars surface- prop density 1m^3 for 1mt (LOX and CH4)- 15m diameter vehicle (this was hited at not actually specified by SpaceX- Raptor engines 380-385 vacuum ISP 500klbfA vehicle like this results:- Vehicle structure+engines+ shield =40mt- Max propellant load 900mt- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capabilityIn order to get to Mars 6-9 tankers docking in LEO-MEO are required Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOW
Except the Vac-optimized Raptors may not have enough thrust to get it off the ground nor the Isp to get to orbit. Just because it might conceivably get 9km/s in free space doesn't mean it is a SSTO.
Quote from: oldAtlas_Eguy on 06/18/2015 03:05 pmThe MCT is not a small vehicle. It could conceivably reach Earth orbit as an SSTO with a little payload about 20mt.20 tonnes to LEO is not a little payload.If the MCT could really achieve a dry mass of 40 tonnes it would make a very useful reusable SSTO.
The MCT is not a small vehicle. It could conceivably reach Earth orbit as an SSTO with a little payload about 20mt.
15m diameter vehicle (this was hited at not actually specified by SpaceX
Now this is an interesting bit, if accurate. For those looking at commonality with MCT to replace Falcon, here you have it. Not a new Raptor powered SFR. The MCT spacecraft acting as a SSTO LV.Of course, most unmanned paylaods are not just going to LEO, so a kick stage or something would need to be used for BLEO trajectories. And that kick stage would need to be significantly cheaper than F9US to make any economic advantage over F9R or FHR.But interesting, nontheless.
Quote from: lamontagne on 06/18/2015 03:00 pmQuote from: oldAtlas_Eguy on 06/18/2015 02:39 pmFrom Statements made by SpaceX representatives:- 100mt payload delivery to Mars- 1/4 payload SSTO return to Earth from mars surface- prop density 1m^3 for 1mt (LOX and CH4)- 15m diameter vehicle (this was hited at not actually specified by SpaceX- Raptor engines 380-385 vacuum ISP 500klbfA vehicle like this results:- Vehicle structure+engines+ shield =40mt- Max propellant load 900mt- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capabilityIn order to get to Mars 6-9 tankers docking in LEO-MEO are required Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOWThanks, this is a great summary. I guess this means not much water based radiation shielding? And if as Guckyfan proposes there is no final injection burn, not much fuel at the end for radiation protection either?One item I forgot to mention was the number of Raptors on MCT would be 5 to give a 3g liftoff at Mars with immediate 1 engine out continue mission capability. Later in Mars launch even 2 engines out would still enable continue mission. A very low risk value for mission success results from this.Edit added: GLOW at Mars liftoff would be 965mt or 2.135Mlb more than 2x the GLOW of the F9v1.0. (65mt dry weight [40mt vehicle 25mt payload]). The MCT is not a small vehicle. It could conceivably reach Earth orbit as an SSTO witha little payload about 20mt.
Quote from: oldAtlas_Eguy on 06/18/2015 02:39 pmFrom Statements made by SpaceX representatives:- 100mt payload delivery to Mars- 1/4 payload SSTO return to Earth from mars surface- prop density 1m^3 for 1mt (LOX and CH4)- 15m diameter vehicle (this was hited at not actually specified by SpaceX- Raptor engines 380-385 vacuum ISP 500klbfA vehicle like this results:- Vehicle structure+engines+ shield =40mt- Max propellant load 900mt- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capabilityIn order to get to Mars 6-9 tankers docking in LEO-MEO are required Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOWThanks, this is a great summary. I guess this means not much water based radiation shielding? And if as Guckyfan proposes there is no final injection burn, not much fuel at the end for radiation protection either?
I have just noticed this year's number for the raptor engine, at 230 tonnes rather than 820 tonnes (Raptor engine Wikipedia article). As this is a direct quote from Musk, it seems cannon. That means something like 28+ engines for the fully fuelled ship on Earth. That probably doesn't fit on a 10m core. So the single core design would have to be larger, leading to a very short rocket, 35 to 40 m high for a 15m core, for example. Is that the present consensus, more or less?
Quote from: oldAtlas_Eguy on 06/18/2015 02:39 pmFrom Statements made by SpaceX representatives:- 100mt payload delivery to Mars- 1/4 payload SSTO return to Earth from mars surface- prop density 1m^3 for 1mt (LOX and CH4)- 15m diameter vehicle (this was hited at not actually specified by SpaceX- Raptor engines 380-385 vacuum ISP 500klbfA vehicle like this results:- Vehicle structure+engines+ shield =40mt- Max propellant load 900mt- propulsion section (engines and tanks) cylindircal or nearly cylindrical section at base 15m diameter and 6m tall- bi-conal payload section (first section 15m to 10m diameter 10m tall) (second section 10m to 0m 10m tall) ~1800m^3 volume-MCT can be its own 2nd stage on the BFR (BFR is basically just the 1st stage) would have ~7.5km/s delta v capability with a 100mt payload+40mt vehicle dry weight +900mt propellant load-An MCT tanker variant would be a Cargo MCT without any cargo which could deliver ~150mt of propellant to LEO would have 6km/s delta v capabilityIn order to get to Mars 6-9 tankers docking in LEO-MEO are required Edit Added: BTW An MCT cargo used as the 2nd stage going just to LEO would be capable of delivering 180mt of payload. Note the 1st stage needs to be capable of ~3km/s delta v with a fully loaded MCT + 180mt of payload on top ~1120mt MCT+payload GLOWThat gives you and MCT with a ΔV of 7.475 km/s (380 isp) I am under the impression that ΔV budget of 4.5km/s worst case for LEO-Mars TMI and that variably we have been discussing needs in the order of 1kms for EDL presuming Aerocapture/braking. That leave us with a need for about 5.5km/s, since making LEO as a 2nd stage for F9 needs about 5.9, I am happy with making 6.2km/s the round number leaving a healthy margin of fuel for Earth EDL. At 6.2km/s and 380isp I see the amount of propellant needed for the dry weight and payload you mentioned being 600t at launch, and 472t leaving LEO. However, personally, even with the smaller propellant load, I would presume MCT's dry weight (which includes potentially some active cooling for propellant and/or sun shades/reflectors, solar power, a higher proportion of RCS than your average US, and several other systems not seen on upper stages) is 60t.I see it launching with less than full cargo though and having a full tank for the TMI burn.Can you tell me where your 7.475km/s came from (or where I might have made an assumption about your vehicle concept that reduces its ΔV)
Quote from: Robotbeat on 06/18/2015 03:56 pmExcept the Vac-optimized Raptors may not have enough thrust to get it off the ground nor the Isp to get to orbit. Just because it might conceivably get 9km/s in free space doesn't mean it is a SSTO.Btw how would MCT land on Earth if it had vac-Raptors?
Mars surface to earth is much less than 9km/s. More like 7-7.5km/s.
The TPS is attached to the tanks and intertank structures through the TPSS. Depending on the tank structural concept and stiffening arrangement, the TPSS may be attached to external stiffeners, such as ring frames and longerons, or to the outer skin of a sandwich tank structure.