Quote from: philw1776 on 10/23/2015 02:13 pmMusk has worked out just enough about potential "MCT" approaches that he has a generic requirement for his BFR launcher. I am certain that he has explored the solution space for Mars transport and wants a launch capability that can support solutions from all chemical solution to SEP/chemical hybrid transport and other possible more exotic solutions. Technology over a >10 year timeframe does not stay still. The 1st and 2nd stage need only be able to get the 100mT cargo plus MCT dry weight into appropriate LEO. If all his broad brush Mars transport solution space fits within these parameters and their evolutionary improvements (e.g.Merlin to Merlin FT), he's good to go.But why build BFR first? BFR has the most infrastructure requirements. Additionally, you're making the implicit assumption that MCT isn't essentially BFR's second stage. I really, REALLY don't expect SpaceX to make the same mistake NASA is currently making by building a super-expensive-to-develop-and-maintain launch vehicle without really anything to launch.
Musk has worked out just enough about potential "MCT" approaches that he has a generic requirement for his BFR launcher. I am certain that he has explored the solution space for Mars transport and wants a launch capability that can support solutions from all chemical solution to SEP/chemical hybrid transport and other possible more exotic solutions. Technology over a >10 year timeframe does not stay still. The 1st and 2nd stage need only be able to get the 100mT cargo plus MCT dry weight into appropriate LEO. If all his broad brush Mars transport solution space fits within these parameters and their evolutionary improvements (e.g.Merlin to Merlin FT), he's good to go.
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.
... It is also unfeasible on technical grounds but no one seems willing to admit this.
You can't have it both ways, either SpaceX is a lean and efficient vertically integrated company that's vastly more efficient then 'Old-Space' capable of making a rocket without a huge standing army or they aren't. If BFR takes huge infrastructure to build and maintain like SLS dose then the prospect of getting to mars is already busted.
I've said a dozen times I expect SpaceX to sell normal commercial flights on BFR for a good long time before it is use for mars, that will build precious flight history before people fly on it. Two or three large com satellites at a time, Bigelow type space stations, the LEO satellite swarms, and any NASA missions that would have flown on SLS are all potential things to fill the rocket with. And because these things require a normal 2nd stage that is the configuration that makes sense, it allows a product that can fend for itself in the marketplace and pay for it's own infrastructure without putting that whole cost onto the back of the mars ticket. Also it doesn't risk completely bankrupting the company in getting to mars turns out to be harder then expected to develop or customers are not ready to buy when the ride is offered.
As NASA is the only conceivable customer for a first mission they need to be courted to create a mission utilizing SpaceX as the primary contractor. But NASA will need a decade or more to develop and ready the ground systems. But to fund that SLS needs to be canceled first and that not going to come until a proven alternative has been fully demonstrated to be reliable.
Were already seeing spiral development from SpaceX when they layed down considerable time and money for Raptor development which was clearly started without the full mars architecture in place, and probably no more then a vague sense of how large BFR would be either. They just set out to the make the best engine possible and then build the best launch vehicle with and around it.
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.
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.
People have been collectively running math here for years and there's nothing theoretically showstopping about it. Yes, it's tricky engineering, but it's not physics violating engineering. This isn't so much of a quantum leap as the R7 was from the V2.
Quote from: The Amazing Catstronaut on 10/24/2015 04:53 pmPeople have been collectively running math here for years and there's nothing theoretically showstopping about it. Yes, it's tricky engineering, but it's not physics violating engineering. This isn't so much of a quantum leap as the R7 was from the V2.Designing MCT for Mars EDL will be tricky and in the end they may fail on that. Success is not guaranteed. But I am optimistic about it. As you said, there are years of engineering behind it by top designers. It is not like Elon Musk was on it alone and it is all pipe dreams.
Quote from: Robotbeat on 10/23/2015 11:37 pmQuote from: philw1776 on 10/23/2015 02:13 pmMusk has worked out just enough about potential "MCT" approaches that he has a generic requirement for his BFR launcher. I am certain that he has explored the solution space for Mars transport and wants a launch capability that can support solutions from all chemical solution to SEP/chemical hybrid transport and other possible more exotic solutions. Technology over a >10 year timeframe does not stay still. The 1st and 2nd stage need only be able to get the 100mT cargo plus MCT dry weight into appropriate LEO. If all his broad brush Mars transport solution space fits within these parameters and their evolutionary improvements (e.g.Merlin to Merlin FT), he's good to go.But why build BFR first? BFR has the most infrastructure requirements. Additionally, you're making the implicit assumption that MCT isn't essentially BFR's second stage. I really, REALLY don't expect SpaceX to make the same mistake NASA is currently making by building a super-expensive-to-develop-and-maintain launch vehicle without really anything to launch.You can't have it both ways, either SpaceX is a lean and efficient vertically integrated company that's vastly more efficient then 'Old-Space' capable of making a rocket without a huge standing army or they aren't. If BFR takes huge infrastructure to build and maintain like SLS dose then the prospect of getting to mars is already busted.
First the idea of a high maintenance cost is inconsistent with SpaceX operations, they shown the ability to build and launch with much less manpower. It also ignores the intended re-usable nature of BFR, they do not need to manufacture them at a rate of one a month like Falcon, though they will likely make Raptor engines at a few a week with a comparable labor input and assembly-line like production like Merlin manufacturing.
RB is arguing that the whole top to bottom mars transportation system has to come into being simultaneously.
...The safe strategy ...
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.)
This is my guess at a MCT plan. Note I've separated out the tanker, cargo and crew variants of MCT although they are all based on the same design.
Musk mentioned like 80,000 people per year. He didn't specify synod. So that's almost another whole order of magnitude.
Millions of people needed for Mars colony, so 80k+ would just be the number moving to Mars per year
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.)
https://twitter.com/elonmusk/status/273483420468932608Quote from: @elonmuskMillions of people needed for Mars colony, so 80k+ would just be the number moving to Mars per year