Quote from: J-V on 11/30/2016 12:24 pmWhat would the numbers look like, if assuming ISRU LOX from lunar surface? Somewhat better I assume, but how much?I think in this case the numbers are easy. Every kg of propellant you transfer aboard while on the lunar surface is a kg of propellant you didn't have to bring down to the lunar surface. So it frees up a kg of down-mass payload capability. Yes?

What would the numbers look like, if assuming ISRU LOX from lunar surface? Somewhat better I assume, but how much?

sdsds: You have 100 m/s margin for lunar landing and another 100 m/s margin for earth... are those additive at all? If you don't use all the margin at luna, do you leave that propellant in lunar orbit? Or do you take it back to earth, increasing the margin there but also impacting everything else (because you have a bit more mass to take)?

Second: his proposal allows each mission to target a different lunar surface location, so long as each ascending ship can make rendezvous with the incoming ship.

Quote from: sdsds on 12/02/2016 02:10 amQuote from: J-V on 11/30/2016 12:24 pmWhat would the numbers look like, if assuming ISRU LOX from lunar surface? Somewhat better I assume, but how much?I think in this case the numbers are easy. Every kg of propellant you transfer aboard while on the lunar surface is a kg of propellant you didn't have to bring down to the lunar surface. So it frees up a kg of down-mass payload capability. Yes?Its a bit more complicated than that. Assuming a 3.5 to 1 oxidiser to fuel mixture ratio, the saved 97.0*3.5/4.5 = 75.4 t of oxidiser mass increases payload mass by 75.4 t to 107.2+75.4 = 182.6 t. This also means that there is 75.4 t of extra propellant mass to bring extra payload down to the Lunar surface. Would have to crunch through the numbers to work out what that would be. A smaller increase could be further made by bringing some coal from Earth and combining that with hydrogen from Lunar water to make methane.

What if you also transfer lunalox to the landing ITS on the orbit from the ascending ITS?

Quote from: J-V on 12/02/2016 07:17 amWhat if you also transfer lunalox to the landing ITS on the orbit from the ascending ITS? You're trading extra methalox required to lift the LOX with the LOX that is brought up. I'd need to crunch the numbers but there might be a benefit. With hydrolox I know there is a benefit as I've studied this before (see my Lunar orbit propellant transfer paper on the first page). The lower Isp and mixture ratio of methalox might not have that advantage.

Waiting to see the numbers. Thank you!

IAC 2017 conference Ran some numbers for the new version of BFS for Lunar landing using Steven's method. Looks like it can deliver about 20 t cargo to the Lunar surface. However I did not include boil off.Any idea what the boil off rate would be? In LEO, LLO, Lunar surface, on way to and from moon. If anyone would like to run their own calculations that would be great.

Quote from: RocketmanUS on 10/04/2017 05:51 amIAC 2017 conference Ran some numbers for the new version of BFS for Lunar landing using Steven's method. Looks like it can deliver about 20 t cargo to the Lunar surface. However I did not include boil off.Any idea what the boil off rate would be? In LEO, LLO, Lunar surface, on way to and from moon. If anyone would like to run their own calculations that would be great.Is that with propellants fill up to full from a tanker after the Moon bound BFS departed LEO?

Quote from: Zed_Noir on 10/04/2017 09:22 amQuote from: RocketmanUS on 10/04/2017 05:51 amIAC 2017 conference Ran some numbers for the new version of BFS for Lunar landing using Steven's method. Looks like it can deliver about 20 t cargo to the Lunar surface. However I did not include boil off.Any idea what the boil off rate would be? In LEO, LLO, Lunar surface, on way to and from moon. If anyone would like to run their own calculations that would be great.Is that with propellants fill up to full from a tanker after the Moon bound BFS departed LEO?Fully fuel in LEO by tankers before TLI burn.

Quote from: RocketmanUS on 10/04/2017 11:32 pmQuote from: Zed_Noir on 10/04/2017 09:22 amQuote from: RocketmanUS on 10/04/2017 05:51 amIAC 2017 conference Ran some numbers for the new version of BFS for Lunar landing using Steven's method. Looks like it can deliver about 20 t cargo to the Lunar surface. However I did not include boil off.Any idea what the boil off rate would be? In LEO, LLO, Lunar surface, on way to and from moon. If anyone would like to run their own calculations that would be great.Is that with propellants fill up to full from a tanker after the Moon bound BFS departed LEO?Fully fuel in LEO by tankers before TLI burn.Ah! But Musk said they'd refuel in high, elliptical orbit for lunar missions. (I actually mentioned this possibility many months ago.)

Quote from: Robotbeat on 10/05/2017 12:31 amQuote from: RocketmanUS on 10/04/2017 11:32 pmQuote from: Zed_Noir on 10/04/2017 09:22 amQuote from: RocketmanUS on 10/04/2017 05:51 amIAC 2017 conference Ran some numbers for the new version of BFS for Lunar landing using Steven's method. Looks like it can deliver about 20 t cargo to the Lunar surface. However I did not include boil off.Any idea what the boil off rate would be? In LEO, LLO, Lunar surface, on way to and from moon. If anyone would like to run their own calculations that would be great.Is that with propellants fill up to full from a tanker after the Moon bound BFS departed LEO?Fully fuel in LEO by tankers before TLI burn.Ah! But Musk said they'd refuel in high, elliptical orbit for lunar missions. (I actually mentioned this possibility many months ago.)Robobeat, I know what he said, but that is not the concept of Steven's for this thread. Could you please run the numbers to see if this new version can bring cargo to the Lunar surface per this concept and if so how much?

@ ciscosdadNot having crew spending unneeded time in the Van Allen belts is why I was looking at Steven's concept for this new BFS.@envy887Thanks, what I needed was the number of payload mass using Steven's concept. So what you got was 23 t payload.Any ides on how much unused propellant mass there would be? That is the unused in the engines and that used to pressurize the tanks.

Quote from: RocketmanUS on 10/05/2017 04:11 am@ ciscosdadNot having crew spending unneeded time in the Van Allen belts is why I was looking at Steven's concept for this new BFS.@envy887Thanks, what I needed was the number of payload mass using Steven's concept. So what you got was 23 t payload.Any ides on how much unused propellant mass there would be? That is the unused in the engines and that used to pressurize the tanks.Steven's OP had two concepts, you'll have to clarify which you meant:1) Refuel in LEO, direct lunar landing and return to Earth surface (this had negative payload), and 2) Refuel in LEO, land on lunar surface, ascend to LLO rendezvous for return fuel, then direct return and landing on Earth (105 t payload landed).I slightly modified these concepts to:3) Refuel in LEO, direct landing and return to LEO with aerobraking, refuel in LEO before landing on Earth surface (10 t payload for full round trip), and4) Refuel in LEO, boost to EEO, top off before TLI, descent to LLO and lunar landing, drop off 150 t payload, return to LLO empty, pick up fuel for TEI, aerobrake into LEO, pick up fuel for Earth landing.My mission profiles trade some operational complexity for a lot more payload; I get 43% more payload to the lunar surface despite 38% less IMLEO, by having 10 rendezvous instead of 7. One additional rendezvous is in LEO, and the other 2 in low elliptical Earth orbit, apogee ~3500 km.

Quote from: envy887 on 10/05/2017 03:30 pmQuote from: RocketmanUS on 10/05/2017 04:11 am@ ciscosdadNot having crew spending unneeded time in the Van Allen belts is why I was looking at Steven's concept for this new BFS.@envy887Thanks, what I needed was the number of payload mass using Steven's concept. So what you got was 23 t payload.Any ides on how much unused propellant mass there would be? That is the unused in the engines and that used to pressurize the tanks.Steven's OP had two concepts, you'll have to clarify which you meant:1) Refuel in LEO, direct lunar landing and return to Earth surface (this had negative payload), and 2) Refuel in LEO, land on lunar surface, ascend to LLO rendezvous for return fuel, then direct return and landing on Earth (105 t payload landed).I slightly modified these concepts to:3) Refuel in LEO, direct landing and return to LEO with aerobraking, refuel in LEO before landing on Earth surface (10 t payload for full round trip), and4) Refuel in LEO, boost to EEO, top off before TLI, descent to LLO and lunar landing, drop off 150 t payload, return to LLO empty, pick up fuel for TEI, aerobrake into LEO, pick up fuel for Earth landing.My mission profiles trade some operational complexity for a lot more payload; I get 43% more payload to the lunar surface despite 38% less IMLEO, by having 10 rendezvous instead of 7. One additional rendezvous is in LEO, and the other 2 in low elliptical Earth orbit, apogee ~3500 km.Option #2 please for the 2017 version of BFR/BFS.