In fact, the "ISRU dev is pretty far along" comment is possibly the most important single piece of info from the AMA. If ISRU can't be done and done reliably, SpaceX's entire strategy is dead in the water.I badly want to see what exactly is meant by "pretty far", I'd love to see some additional info on their progress Things will certainly start to get interesting if they have had considerable success, as NASA is years away from their first real test of ISRU, to be included on the Mars 2020 rover.
Quote from: vaporcobra on 10/15/2017 10:55 pmIn fact, the "ISRU dev is pretty far along" comment is possibly the most important single piece of info from the AMA. If ISRU can't be done and done reliably, SpaceX's entire strategy is dead in the water.I badly want to see what exactly is meant by "pretty far", I'd love to see some additional info on their progress Things will certainly start to get interesting if they have had considerable success, as NASA is years away from their first real test of ISRU, to be included on the Mars 2020 rover.I would like to see a thread started on this, by someone with the enthusiasm to keep updating the OP with the actual information we have from SpaceX (which would not make a very large post at this point)
Quote from: rsdavis9 on 10/15/2017 08:47 pmI think they plan to leave some of the first BFS's to mars on the surface as part of the station.That seems a waste. It's a pretty expensive piece of kit - why not refuel it and have it return to Earth for reuse?
I think they plan to leave some of the first BFS's to mars on the surface as part of the station.
Quote from: CuddlyRocket on 10/15/2017 11:38 pmQuote from: rsdavis9 on 10/15/2017 08:47 pmI think they plan to leave some of the first BFS's to mars on the surface as part of the station.That seems a waste. It's a pretty expensive piece of kit - why not refuel it and have it return to Earth for reuse?First dwellings with everything they need. Maybe they will get modded too much or too old beyond reflight back. Really just the first few.
Quote from: rsdavis9 on 10/16/2017 12:59 amQuote from: CuddlyRocket on 10/15/2017 11:38 pmQuote from: rsdavis9 on 10/15/2017 08:47 pmI think they plan to leave some of the first BFS's to mars on the surface as part of the station.That seems a waste. It's a pretty expensive piece of kit - why not refuel it and have it return to Earth for reuse?First dwellings with everything they need. Maybe they will get modded too much or too old beyond reflight back. Really just the first few.Take a brand new BFS (ship A) to Mars, in 2022 or 2024. That's what, 150 days travel then it sits while being unloaded, habitats established and proven, after that, it returns to earth. That's what, another 150 days. The ship is now how old? At least a year old assuming establishing habitats is a priority, It could be much older. How far will SpaceX advance the design of the currently new BFS's while ship A is making this round trip? Or another way of looking at it is, "How useful is a year or more old Falcon 9 these days?" Or, "Has SpaceX ever built a rocket that didn't undergo major evolutionary changes over the span of a year's time?"In particular, we are addressing the first BFS's out of the box, not a mature, stable design as planned to exist by 2026.
Quote from: mnelson on 10/15/2017 11:24 pmQuote from: vaporcobra on 10/15/2017 09:43 pmQ: Will the BFS tanker's payload section be empty, or include extra propellant tanks?A (Elon): At first, the tanker will just be a ship with no payload. Down the road, we will build a dedicated tanker that will have an extremely high full to empty mass ratio (warning: it will look kinda weird).Any ideas why the dedicated tanker would "look kinda weird?"My theory is it's because the density of the fuel is low enough that they can strap on nearly double tanks to take up the mass payload capacity.See Airbus Belluga if you want to see what he's talking about.
Quote from: vaporcobra on 10/15/2017 09:43 pmQ: Will the BFS tanker's payload section be empty, or include extra propellant tanks?A (Elon): At first, the tanker will just be a ship with no payload. Down the road, we will build a dedicated tanker that will have an extremely high full to empty mass ratio (warning: it will look kinda weird).Any ideas why the dedicated tanker would "look kinda weird?"
Q: Will the BFS tanker's payload section be empty, or include extra propellant tanks?A (Elon): At first, the tanker will just be a ship with no payload. Down the road, we will build a dedicated tanker that will have an extremely high full to empty mass ratio (warning: it will look kinda weird).
Quote from: Geron on 10/15/2017 11:34 pmQuote from: mnelson on 10/15/2017 11:24 pmQuote from: vaporcobra on 10/15/2017 09:43 pmQ: Will the BFS tanker's payload section be empty, or include extra propellant tanks?A (Elon): At first, the tanker will just be a ship with no payload. Down the road, we will build a dedicated tanker that will have an extremely high full to empty mass ratio (warning: it will look kinda weird).Any ideas why the dedicated tanker would "look kinda weird?"My theory is it's because the density of the fuel is low enough that they can strap on nearly double tanks to take up the mass payload capacity.See Airbus Belluga if you want to see what he's talking about.Hmmm, that doesn't make sense to me. Wouldn't the density be higher than most payloads so the tanker would be *smaller* than the BFS? 250MT of propellants would be 54MT fuel and 196MT of LOX. If cylindrical tanks with a diameter of 9m are used then the fuel tank would only need to be 56cm tall. The LOX tank 3.5m tall. Why not just replace the whole cargo area with a simple nosecone and stretch the existing tanks by 4m? It could be named "stubby" for short.
Quote from: mnelson on 10/16/2017 02:07 amQuote from: Geron on 10/15/2017 11:34 pmQuote from: mnelson on 10/15/2017 11:24 pmQuote from: vaporcobra on 10/15/2017 09:43 pmQ: Will the BFS tanker's payload section be empty, or include extra propellant tanks?A (Elon): At first, the tanker will just be a ship with no payload. Down the road, we will build a dedicated tanker that will have an extremely high full to empty mass ratio (warning: it will look kinda weird).Any ideas why the dedicated tanker would "look kinda weird?"My theory is it's because the density of the fuel is low enough that they can strap on nearly double tanks to take up the mass payload capacity.See Airbus Belluga if you want to see what he's talking about.Hmmm, that doesn't make sense to me. Wouldn't the density be higher than most payloads so the tanker would be *smaller* than the BFS? 250MT of propellants would be 54MT fuel and 196MT of LOX. If cylindrical tanks with a diameter of 9m are used then the fuel tank would only need to be 56cm tall. The LOX tank 3.5m tall. Why not just replace the whole cargo area with a simple nosecone and stretch the existing tanks by 4m? It could be named "stubby" for short.Yep.Propellant is actually denser than any normal cargo, which is why a Tanker looks just like a dedicated cargo ship with a bit bigger tanks. It’s the same with Air Force Tankers which have fuel tanks in the lower part of the fuselage as well as the wings but are basically empty cargo planes otherwise because the maximum load of fuel they can take off with leaves the entire cargo area of the plane empty.A simple dedicated Tanker version of BFS would just change the OML to leave out the empty cargo hold in the forward Area so it would be like a shortened stubby BFS. I’m probably missing something important because Elon did seem to say a dedicated Tanker was eventually worth doing and in this model not much is gained. I suppose if you are flying them thousands of times a year any gain in efficiency is important so stubby Tanker BFSs are worth it. Until then it’s cool that you really just have to build one kind of BFS to do everything.
You're missing that he didnt say "Simple dedicated tanker version." What he said was "a dedicated tanker that will have an extremely high full to empty mass ratio (warning: it will look kinda weird)."Throw out the current design entirely, optimize entirely for wet to dry mass ratio... I'm thinking something vaguely spherical.Of course, a clean sheet tanker design is expensive and not something needed right away. so, "eventually", even in elon-time.
Yeah, there's still no clear information about the ISRU plan, as noted in the last few posts. It's simply unclear as to whether the first mission will be robotic ISRU, or if ISRU will have to wait for the first crewed mission and that they'll take the risk of a one way trip. That seems unreasonable to me, but the scant amount of information leaves the possibility open that that's the plan: send robots to find the water, but send people to set up the Sabatier reactors and solar panels. The second option is feasible if they send extra fuel once as a bootstrap operation, but that's total supposition. Further supposition rests on the hint that Gwynne dropped about nuclear in SpaceX's future, and the potential that solar won't scale past the beginnings of the project... How I wish we had answers!
Quote from: Robotbeat on 10/15/2017 10:27 pmQuote from: Kaputnik on 10/15/2017 09:37 pmDo we actually know whether they are bringing H2, in whatever form, on the first flights? Or are they going straight for water extraction on Mars, and if so how will they do that?Also, how will they transfer propellants between vehicles on Mars- and fundamental to this is another question, how close to each other can they land? Or will the whole ISRU plant be mobile itself, and load directly into the BFS?We KNOW they aren't bringing hydrogen. We KNOW they're going straight to ISRU. This has been the clear plan since the beginning.In fact, the "ISRU dev is pretty far along" comment is possibly the most important single piece of info from the AMA. If ISRU can't be done and done reliably, SpaceX's entire strategy is dead in the water.I badly want to see what exactly is meant by "pretty far", I'd love to see some additional info on their progress Things will certainly start to get interesting if they have had considerable success, as NASA is years away from their first real test of ISRU, to be included on the Mars 2020 rover.
Quote from: Kaputnik on 10/15/2017 09:37 pmDo we actually know whether they are bringing H2, in whatever form, on the first flights? Or are they going straight for water extraction on Mars, and if so how will they do that?Also, how will they transfer propellants between vehicles on Mars- and fundamental to this is another question, how close to each other can they land? Or will the whole ISRU plant be mobile itself, and load directly into the BFS?We KNOW they aren't bringing hydrogen. We KNOW they're going straight to ISRU. This has been the clear plan since the beginning.
Do we actually know whether they are bringing H2, in whatever form, on the first flights? Or are they going straight for water extraction on Mars, and if so how will they do that?Also, how will they transfer propellants between vehicles on Mars- and fundamental to this is another question, how close to each other can they land? Or will the whole ISRU plant be mobile itself, and load directly into the BFS?
The weird tanker might be a big almost empty tanker.More like the nose cone of a Falcon 9 (12-15 meter wide)Without heat shield Without landing legs Without deep space enginesThat has an “extremely high full to empty mass ratio”.
Quote from: Peter.Colin on 10/16/2017 11:10 amThe weird tanker might be a big almost empty tanker.More like the nose cone of a Falcon 9 (12-15 meter wide)Without heat shield Without landing legs Without deep space enginesThat has an “extremely high full to empty mass ratio”.The whole point is re-use. Did I miss something or do you think a tanker without a heat shield and landing legs could return and land?
Quote from: rockets4life97 on 10/16/2017 11:20 amQuote from: Peter.Colin on 10/16/2017 11:10 amThe weird tanker might be a big almost empty tanker.More like the nose cone of a Falcon 9 (12-15 meter wide)Without heat shield Without landing legs Without deep space enginesThat has an “extremely high full to empty mass ratio”.The whole point is re-use. Did I miss something or do you think a tanker without a heat shield and landing legs could return and land?Not in in one piece.It’s a depot-tanker which remains in orbit.That’s the only thing that makes sense, that would have an extremely full to empty mass ratio.The reduction in mass from launching it empty and stripped can be used to make it much bigger.
Quote from: rockets4life97 on 10/16/2017 11:20 amQuote from: Peter.Colin on 10/16/2017 11:10 amThe weird tanker might be a big almost empty tanker.More like the nose cone of a Falcon 9 (12-15 meter wide)Without heat shield Without landing legs Without deep space enginesThat has an “extremely high full to empty mass ratio”.The whole point is re-use. Did I miss something or do you think a tanker without a heat shield and landing legs could return and land?Not in in one piece.It’s a depot-tanker which remains in orbit.That’s the only thing that makes sense, that would have an extremely full to empty mass ratio.The reduction in mass from launching it empty and stripped can be used to make it much bigger.You could use the largest part of the 26 months between departures to launch the depot-tankers, and filling them up with regular tankers.And than launch the spaceships, that are filled up by the depot-tankers.Maybe 10 launches are needed to fill up a depot-tanker, could someone calculate this?The Mars depot-tanker would need a heat shield.But no landing legs.
And what is a "Mars depot-tanker"? How could it possibly need a heat shield but not landing legs (unless it's doing an ocean splash down I suppose)?