If NASA is to be the first customer the concept is dead in the waterspace. It would introduce decades of delay as you yourself state. It is not going to happen.
Quote from: Impaler on 10/24/2015 05:50 am It is also unfeasible on technical grounds but no one seems willing to admit this.How do you come to that conclusion?
It is also unfeasible on technical grounds but no one seems willing to admit this.
The system must be viable at a lower initial volume so it can survive to ramp up over decades.
No that is not at all reasonable, they will put money generated in other areas into development but they would not RUN the whole system at a loss for decades waiting for volume to grow. That would suck up all their surplus from other activities leaving nothing for continued development and upgrading the system, you make a profitable system and then make it more profitable with your profits. This is completely counter to the entire history of careful and financially cautious development done by SpaceX up till now.Like the old adage "Every complex program that has ever worked has evolved from a simple program that worked, not a complex program that didn't work".
Will BFR/MCT do a full mission - to Mars - refuel - back to Earth unmanned before the first crew? Elon has mentioned Droids and automation as being essential elements.
BTW I was surprised that Elon Musk mentioned they would land humans only when the return fuel is waiting for them. I would have expected to land the equipment but set it up for fuel production only after the human landing.
Quote from: guckyfan on 10/26/2015 04:13 pmBTW I was surprised that Elon Musk mentioned they would land humans only when the return fuel is waiting for them. I would have expected to land the equipment but set it up for fuel production only after the human landing.It makes perfect sense, otherwise you could literally doom/maroon the first crew. Remember that the MCT architecture (as we know it) is completely dependent on manufacturing ALL propellant for the journey home.The first people to land are not going to be permanent colonist.
Quote from: Lars-J on 10/26/2015 04:26 pmQuote from: guckyfan on 10/26/2015 04:13 pmBTW I was surprised that Elon Musk mentioned they would land humans only when the return fuel is waiting for them. I would have expected to land the equipment but set it up for fuel production only after the human landing.It makes perfect sense, otherwise you could literally doom/maroon the first crew. Remember that the MCT architecture (as we know it) is completely dependent on manufacturing ALL propellant for the journey home.The first people to land are not going to be permanent colonist.Not doom. They would not be colonists but they will IMO likely stay for a full synod until a replacement crew arrives. Probably a few stay on to extend their experience to the next crew. Worst case something goes wrong and they stay two synods. On the next synod they would receive spare parts to get fuel ISRU going.
Quote from: guckyfan on 10/26/2015 04:58 pmQuote from: Lars-J on 10/26/2015 04:26 pmQuote from: guckyfan on 10/26/2015 04:13 pmBTW I was surprised that Elon Musk mentioned they would land humans only when the return fuel is waiting for them. I would have expected to land the equipment but set it up for fuel production only after the human landing.It makes perfect sense, otherwise you could literally doom/maroon the first crew. Remember that the MCT architecture (as we know it) is completely dependent on manufacturing ALL propellant for the journey home.The first people to land are not going to be permanent colonist.Not doom. They would not be colonists but they will IMO likely stay for a full synod until a replacement crew arrives. Probably a few stay on to extend their experience to the next crew. Worst case something goes wrong and they stay two synods. On the next synod they would receive spare parts to get fuel ISRU going.Mostly Irrelevant, because they are not going to risk crews on the first mission and landing anyway. And the first unmanned missions need to provide a proof of concept that the ISRU equipment functions. So since they will already have hardware on the ground, making it an all-up test that produces propellant makes the most sense.
Propellant mass fractions that are on par with SSTO vehicles
combined with re-entry conditions that make lunar return look mild.
Quote from: Impaler on 10/26/2015 05:27 amPropellant mass fractions that are on par with SSTO vehicles Not really, there's a huge difference between what's needed for 6.5-8 km/s vs. 9.5 km/s. (I get a mass ratio of about 5.75 for 6.5 km/s, 8.6 for 8 km/s, 12.8 for 9.5 km/s).
Quotecombined with re-entry conditions that make lunar return look mild.Yeah but they also have a better heat shield material than Apollo.
Quote from: Robotbeat on 10/25/2015 10:48 pmThe only thing that might make sense for an HLV is if you had some good rationale for flying enough payloads per year that you could take FULL advantage of a full manufacturing line (multiple shifts) /and/ full advantage of full reuse (both first and second stages). To keep a production line busy, you probably need at least 10 flights per year. To do that with multiple shifts, probably about 40 first stage cores per year (and more upper stages). To make first stage reuse make sense, you need to reuse the stage at least ten times. To make full reuse make sense, you need to reuse the first stage at least 100 times and the upper stage 10-30 times. That's roughly a thousand launches per year at a minimum. Partial reuse can get by with maybe 100 launches per year, 40 per year if some are expendable. Otherwise, it's not really the economic optimum. Unless you get to 1000 launches per year, though, you probably aren't launching enough to gain anything by using an HLV. (In fact, you'd reduce your economic efficiency since you wouldn't be reusing as much.) We do keep hearing high numbers from SpaceX. Fleets, scouting the globe for launch locations to move a lot of people. But I don't think we think in the right scale yet.
The only thing that might make sense for an HLV is if you had some good rationale for flying enough payloads per year that you could take FULL advantage of a full manufacturing line (multiple shifts) /and/ full advantage of full reuse (both first and second stages). To keep a production line busy, you probably need at least 10 flights per year. To do that with multiple shifts, probably about 40 first stage cores per year (and more upper stages). To make first stage reuse make sense, you need to reuse the stage at least ten times. To make full reuse make sense, you need to reuse the first stage at least 100 times and the upper stage 10-30 times. That's roughly a thousand launches per year at a minimum. Partial reuse can get by with maybe 100 launches per year, 40 per year if some are expendable. Otherwise, it's not really the economic optimum. Unless you get to 1000 launches per year, though, you probably aren't launching enough to gain anything by using an HLV. (In fact, you'd reduce your economic efficiency since you wouldn't be reusing as much.)
Quote from: Robotbeat on 10/25/2015 10:48 pmAlso, you're missing a really important point: There isn't actually a market for HLV launch. Nobody* wants more than about EELV Heavy capability (except for exploration, but even then it's not required). There aren't even commercial or military processing facilities for payloads over 5 meters in diameter. There isn't a commercial launch need for BFR, and NASA doesn't even have any payloads that need an HLV. F9 and Falcon Heavy are MORE than enough for all the commercial, civil, and military payloads. I've held this viewpoint for years, I've been vocal about it, and I haven't actually changed my mind on it. The only thing that might make sense for an HLV is if you had some good rationale for flying enough payloads per year that you could take FULL advantage of a full manufacturing line (multiple shifts) /and/ full advantage of full reuse (both first and second stages). To keep a production line busy, you probably need at least 10 flights per year. To do that with multiple shifts, probably about 40 first stage cores per year (and more upper stages). To make first stage reuse make sense, you need to reuse the stage at least ten times. To make full reuse make sense, you need to reuse the first stage at least 100 times and the upper stage 10-30 times. That's roughly a thousand launches per year at a minimum. Partial reuse can get by with maybe 100 launches per year, 40 per year if some are expendable. Otherwise, it's not really the economic optimum. Unless you get to 1000 launches per year, though, you probably aren't launching enough to gain anything by using an HLV. (In fact, you'd reduce your economic efficiency since you wouldn't be reusing as much.) Customers don't care how big the rocket is they care how much it costs. In order to get anywhere near the cost structure Musk desires the cost to launch the BFR would need to be well in the range where it would be a cost effective commercial launcher. While it may cost more then one sat customer would be willing to pay for we already have a NORMAL practice in the industry of launching multiple satellites simultaneously so it is not at all hard to see a viable commercial sat launch market for BFR if it achieved the full reusability which is it's main goal.
Also, you're missing a really important point: There isn't actually a market for HLV launch. Nobody* wants more than about EELV Heavy capability (except for exploration, but even then it's not required). There aren't even commercial or military processing facilities for payloads over 5 meters in diameter. There isn't a commercial launch need for BFR, and NASA doesn't even have any payloads that need an HLV. F9 and Falcon Heavy are MORE than enough for all the commercial, civil, and military payloads. I've held this viewpoint for years, I've been vocal about it, and I haven't actually changed my mind on it. The only thing that might make sense for an HLV is if you had some good rationale for flying enough payloads per year that you could take FULL advantage of a full manufacturing line (multiple shifts) /and/ full advantage of full reuse (both first and second stages). To keep a production line busy, you probably need at least 10 flights per year. To do that with multiple shifts, probably about 40 first stage cores per year (and more upper stages). To make first stage reuse make sense, you need to reuse the stage at least ten times. To make full reuse make sense, you need to reuse the first stage at least 100 times and the upper stage 10-30 times. That's roughly a thousand launches per year at a minimum. Partial reuse can get by with maybe 100 launches per year, 40 per year if some are expendable. Otherwise, it's not really the economic optimum. Unless you get to 1000 launches per year, though, you probably aren't launching enough to gain anything by using an HLV. (In fact, you'd reduce your economic efficiency since you wouldn't be reusing as much.)
Quote from: Robotbeat on 10/23/2015 11:37 pmQuote... So, the Block One MCT will likely again be different from the MCT that lands the first crew on Mars June 2033 following the un-crewed MCT bringing the ISRU equipment May 2031.I have no doubt MCT will evolve, but your timeline is not the same as SpaceX's timeline. They expect crewed missions much earlier. Which makes sense, as it doesn't make sense to develop a capability and then essentially just let it languish, sucking up money while nothing is accomplished (another mistake NASA is making, though this is mostly Congress's fault).Which is exactly why an integrated 2nd stage is a bad idea, it makes the launcher too narrow and unable to serve any other role efficiently. It is also unfeasible on technical grounds but no one seems willing to admit this.
Quote... So, the Block One MCT will likely again be different from the MCT that lands the first crew on Mars June 2033 following the un-crewed MCT bringing the ISRU equipment May 2031.I have no doubt MCT will evolve, but your timeline is not the same as SpaceX's timeline. They expect crewed missions much earlier. Which makes sense, as it doesn't make sense to develop a capability and then essentially just let it languish, sucking up money while nothing is accomplished (another mistake NASA is making, though this is mostly Congress's fault).
... So, the Block One MCT will likely again be different from the MCT that lands the first crew on Mars June 2033 following the un-crewed MCT bringing the ISRU equipment May 2031.
Quote from: guckyfan on 10/26/2015 04:58 pmQuote from: Lars-J on 10/26/2015 04:26 pmQuote from: guckyfan on 10/26/2015 04:13 pmBTW I was surprised that Elon Musk mentioned they would land humans only when the return fuel is waiting for them. I would have expected to land the equipment but set it up for fuel production only after the human landing.It makes perfect sense, otherwise you could literally doom/maroon the first crew. Remember that the MCT architecture (as we know it) is completely dependent on manufacturing ALL propellant for the journey home.The first people to land are not going to be permanent colonist.Not doom. They would not be colonists but they will IMO likely stay for a full synod until a replacement crew arrives. Probably a few stay on to extend their experience to the next crew. Worst case something goes wrong and they stay two synods. On the next synod they would receive spare parts to get fuel ISRU going.Musk is borrowing somewhat from Mars Direct (or is it Semi-Direct?) where an already-fueled ascent vehicle is fueled up on the surface. I don't see a good reason not to have a fueled up vehicle ready when they arrive.
It could do a Bigelow module or large space telescope or something too, but those would be pretty rare, more one time events. Big telescopes are expensive and you only need so many big Bigelow modules in orbit.