Quote from: RocketmanUS on 10/05/2017 04:50 pmQuote 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.Using Steven's delta-v figures and the #2 mission profile, I get 57 tonnes for the 2017 BFR vs. 105 tonnes for the 2016 architecture.
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.
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.
@ 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.
Did you off load the return propellant before Lunar descent into another BFS that just came up from moon for return trip back to Earth? The number you have ( 57 t ) would be for the first BFR landing I believe , all the other BFR's would have a lower payload mass. Keep in mind that at around 20 t payload that payload also returns back to Earth ( this assumes crew missions ).
OK, ran my software for the new BFR. First flight payload mass is 90.5 t, with subsequent flights having a payload of 47.6 t. Transfer propellant in LLO is 62.0 t. Would need seven refuelling flights (or eight flights altogether) for each mission! For the first flight we have propellant mass of 7x150 + 150-90.5 = 1109.5 t, just over the 1100 t capability of BFS. Software attached.
Quote from: Steven Pietrobon on 10/08/2017 01:37 amOK, ran my software for the new BFR. First flight payload mass is 90.5 t, with subsequent flights having a payload of 47.6 t. Transfer propellant in LLO is 62.0 t. Would need seven refuelling flights (or eight flights altogether) for each mission! For the first flight we have propellant mass of 7x150 + 150-90.5 = 1109.5 t, just over the 1100 t capability of BFS. Software attached.Thanks.That is with the cargo left on the moon.What I was doing was bringing the cargo back. I did this to see how much return payload mass could be available for a crewed mission. That is the crew mass , their suits, ect.Edit:Ran the numbers for payload round trip from LEO ( refueled ) to Lunar surface and back to Earth. This is with estimated unusable propellant ( 8,000 kg ), Still would need an expert answer for better estimate. Finding was 12 t payload round trip picking up return propellant in LEO from incoming BFS before return trip to Earth.
Quote from: RocketmanUS on 10/09/2017 05:09 amQuote from: Steven Pietrobon on 10/08/2017 01:37 amOK, ran my software for the new BFR. First flight payload mass is 90.5 t, with subsequent flights having a payload of 47.6 t. Transfer propellant in LLO is 62.0 t. Would need seven refuelling flights (or eight flights altogether) for each mission! For the first flight we have propellant mass of 7x150 + 150-90.5 = 1109.5 t, just over the 1100 t capability of BFS. Software attached.Thanks.That is with the cargo left on the moon.What I was doing was bringing the cargo back. I did this to see how much return payload mass could be available for a crewed mission. That is the crew mass , their suits, ect.Edit:Ran the numbers for payload round trip from LEO ( refueled ) to Lunar surface and back to Earth. This is with estimated unusable propellant ( 8,000 kg ), Still would need an expert answer for better estimate. Finding was 12 t payload round trip picking up return propellant in LEO from incoming BFS before return trip to Earth.Picking up return propellant in LLO or LEO? It should be possible to do both, which combined with a tanker top-off in low EEO gives a round-trip payload of over 50 tonnes.
...After TEI how much propellant is needed to brake into EEO?
Quote from: RocketmanUS on 10/12/2017 07:58 pm...After TEI how much propellant is needed to brake into EEO?If you are braking into orbit it makes more sense to go to LEO, not EEO.But it doesn't really matter for this calculation. An aerobrake orbit will dip into the atmosphere with a perigee of around 60-80 km. Pulling the perigee up to ~300 km so you don't reenter on the next orbit takes about 55-65 m/s at apogee.Compare this to landing which takes 500 to 800 m/s, and this fuel has to go at least to LLO and back, and you can see why it helps the payload a lot.
ISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.
Quote from: corneliussulla on 10/18/2017 06:56 amISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.ISRU for LOX only could make a lot of sense. After all LOX is ~80% of propellant mass. There is a concept worked on to produce LOX from SiO2 which is available everywhere on the moon. But worth it probably only when regular large payloads to the moon are needed.
Quote from: guckyfan on 10/18/2017 09:41 amQuote from: corneliussulla on 10/18/2017 06:56 amISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.ISRU for LOX only could make a lot of sense. After all LOX is ~80% of propellant mass. There is a concept worked on to produce LOX from SiO2 which is available everywhere on the moon. But worth it probably only when regular large payloads to the moon are needed.Lunar ISRU trades against 3 or 4 tanker flights to LEO, to land a 150 tonne payload on the Moon and return empty, or landing 50 tonnes and returning 50 tonnes. Tanker flights have to be pretty expensive to make ISRU worthwhile (this is not the case form Mars since Mars is so much more difficult to return from).I haven't worked the numbers for landing 150 tonnes and returning 50 tonnes, but that's the limit of the BFR/BFS architecture unless you go to LEO payload transfer - and even then it's likely volume limited for most payloads. I don't think lunar ISRU fits well with BFS/BFR. But it does make sense to have it for at least an emergency backup O2 and H2O source if you have a lunar base.
Quote from: corneliussulla on 10/18/2017 06:56 amISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.No, it'd make it far more complex. If you need a lot of payload on or off the Moon, it might still make sense cost-wise, but it's FAR simpler without lunar ISRU.
Some dispute about whether the CO results are trustworthy, apparently. We just have to go and look. It is definitely possible though. It is frustrating that such huge HSF architectures are being finalised without this basic information verified. This is not a SpaceX criticism.Jon Goff mentions some Paul Spudis doubt here:https://forum.nasaspaceflight.com/index.php?topic=39559.msg1612453#msg1612453
But primarily any significant source of carbon found would enable the creation of methane when combined with water and other O2 from oxides.