Quote from: nadreck on 08/18/2015 02:36 pmThe one alternative I can see is if we do ISRU on Phobos or Deimos and supply many manned sorties to the surface of Mars before building the first settlements. This would still involve a permanent presence and the one reason I don't really elaborate on it here is the idea that it doesn't work all that well with the MCT model driving Mars settlement.This may or may not warrant an extended discussion. I do like that idea as I was always thinking of fuel ISRU at Phobos or Deimos. Do we know if MCT would be able to land with enough fuel to lift off again? It probably should not be much heavier than on a normal landing with 100t supplies. So with minimal life support for a small crew and very little cargo to maximise fuel. Still seems not enough with less than 100t to lift off and reach Phobos. Maybe entry from orbit at lower speed allows for some more payload.
The one alternative I can see is if we do ISRU on Phobos or Deimos and supply many manned sorties to the surface of Mars before building the first settlements. This would still involve a permanent presence and the one reason I don't really elaborate on it here is the idea that it doesn't work all that well with the MCT model driving Mars settlement.
Known 'facts' about MCT you can fit on the back of a stamp. A small one, that already has writing on the back.Even things Musk has already said (which is practically nothing anyway) are liable to significant change. Just like most other things SpaceX have done. They are happy to change as they go along, as they discover more stuff.
New info from Musk about the Raptor and MCT(and sorry about the crossposting):Quote from: Elon MuskYeah, these are seemingly absurd percentage improvements, however not impossible. The critical elements of the solution are rocket reusability and low cost propellant (CH4 and O2 at an O/F ratio of ~3.8 ). And, of course, making the return propellant on Mars, which has a handy CO2 atmosphere and lots of H2O frozen in the soil.The design goal is technically 100+ metric tons of useful cargo per flight, so maybe more than 100 people can be taken. Depends on how much support mass is needed per person and the luggage allowable.Avionics, sensors, communications, aspects of vehicle structure, landing pads and a few other things get better with scale, plus it is more fun to be on a cruise ship than a bus, so I suspect that the 100 people per flight number grows a lot over time, maybe to several hundred. Also, we could subsidize the equivalent of economy by charging a lot more for first class.Factor in all of the above and getting below $100k/ton or person eventually is conceivable, as the trip cost is then dominated by propellant, which is mostly liquid oxygen at a mere $40/ton (although a lot of it is needed per useful ton of cargo). That would be really awesome!Looks like the Raptor will run oxidizer rich. That puts its niche even closer to the BE-4.
Yeah, these are seemingly absurd percentage improvements, however not impossible. The critical elements of the solution are rocket reusability and low cost propellant (CH4 and O2 at an O/F ratio of ~3.8 ). And, of course, making the return propellant on Mars, which has a handy CO2 atmosphere and lots of H2O frozen in the soil.The design goal is technically 100+ metric tons of useful cargo per flight, so maybe more than 100 people can be taken. Depends on how much support mass is needed per person and the luggage allowable.Avionics, sensors, communications, aspects of vehicle structure, landing pads and a few other things get better with scale, plus it is more fun to be on a cruise ship than a bus, so I suspect that the 100 people per flight number grows a lot over time, maybe to several hundred. Also, we could subsidize the equivalent of economy by charging a lot more for first class.Factor in all of the above and getting below $100k/ton or person eventually is conceivable, as the trip cost is then dominated by propellant, which is mostly liquid oxygen at a mere $40/ton (although a lot of it is needed per useful ton of cargo). That would be really awesome!
IMHO, a reality check on MCT has been long overdue as this thread wanders all over the place because there are no facts to pin us down.
SpaceX can't even build Dragon 2 without public support, and it's been delayed for years because of a lack of internal funding to make up for shortfalls in public funding measured in millions of dollars. Yet somehow SpaceX is going to commit to actually building and flying BFR and MCT with billions of their own dollars and no contracted return on the investment? I don't think so. Not a snowball's chance in Hades.
More likely IMHO is that we'll see a fleshed-out paper concept similar to Hyperloop. Then they will go fishing for governments to pony up the development costs in order to be occupants on the actual spacecraft.
That tactic may work, but SpaceX doesn't have that many supporters in Congress as a consequence of making everything under one roof. Even if money does come in from a government source, which won't be possible to even have allocated until 2017 at the extreme earliest, we won't see parts manufactured for the spacecraft until sometime in the mid to late 2020's.
Now, could I be entirely wrong? Sure I could, I'd love to be wrong on this! But the Dragon2 development experience is telling me I'm not.
On the gripping hand, a large well-funded religious group could put up a few billion to have a planet all their own for their more fervent adherents with no problem at all. It worked for the Pilgrims, why not Scientologists!?!
I rush to point out how much SpaceX has funded from their own pocket so far, and shown that they can continue to raise equity to fund their portion of developments (they just raised $1B).
I personally would like to see only humanist motivations organizing off Earth communities and their rules and customs (and on Earth communities for that matter). Let us please avoid bringing prejudice and hate into space (eliminating nationalism as well as religion).
Quote from: nadreck on 08/18/2015 05:15 pmI rush to point out how much SpaceX has funded from their own pocket so far, and shown that they can continue to raise equity to fund their portion of developments (they just raised $1B).Like Tesla, SpaceX's 'pocket' is rapidly running out. The $1B was allocated to general funds, not just the satellite venture where it is much needed, which speaks to the shallow depth of the general funds. It is clear that the larger SpaceX plan depends on satellite income, much like Tesla's larger plan depends on model X, and then the model after that. And like Tesla, raising funds by diluting ownership is not sustainable at the level needed to compensate for foundering profits. I do think both companies can stay afloat, but this dangerous game was Musk's plan all along, and we should recognize how dangerous it is.
Quote from: nadreck on 08/18/2015 05:15 pm I personally would like to see only humanist motivations organizing off Earth communities and their rules and customs (and on Earth communities for that matter). Let us please avoid bringing prejudice and hate into space (eliminating nationalism as well as religion).Aldrin took communion on the moon, read the words of Jesus, and planted the American flag. This did not preclude the trip from being for all mankind. We should let our rules and customs be what they are, wherever we are, in the spirit of individual freedom.
I'm confused again. Do folks here believe that Musk has said the MCT is 200mT to LEO (then refueled and onto Mars' surface) with 100mT useful payload? Or is it 100mT useful payload with X mT more being the Dry Mass of what it takes to carry that payload...airframe, empty fuel tanks, re-entry shield, engine tonnage?
IMHO, a reality check on MCT has been long overdue as this thread wanders all over the place because there are no facts to pin us down. SpaceX can't even build Dragon 2 without public support, and it's been delayed for years because of a lack of internal funding to make up for shortfalls in public funding measured in millions of dollars. Yet somehow SpaceX is going to commit to actually building and flying BFR and MCT with billions of their own dollars and no contracted return on the investment? I don't think so. Not a snowball's chance in Hades.
Quote from: philw1776 on 08/19/2015 03:37 pmI'm confused again. Do folks here believe that Musk has said the MCT is 200mT to LEO (then refueled and onto Mars' surface) with 100mT useful payload? Or is it 100mT useful payload with X mT more being the Dry Mass of what it takes to carry that payload...airframe, empty fuel tanks, re-entry shield, engine tonnage?I think that Musk has said that the MCT will deliver 100t to Mars via a trip to Earth orbit for refueling. How much it can put into LEO was not a matter of record from Elon and speculation here has been anything from 70t to LEO to 200t to LEO.My personal expectation is that MCT will have an dry weight around 50t, carry 100t of payload, 670t of propellant and that a tanker version that is reusable to LEO has a dry weight of 30t, carries virtually no payload but 800t of propellant at launch and can nominally deliver 130t of that to a depot. Thus 5 to 6 tanker flights per MCT launch to Mars (note that I am presuming a ΔV budget of 6km/s).
You seem to be throwing your lot in with Vultur and the MarsOne nonsense of immediate colonization from the first footprint. This is not going to happen, it's like saying that Neil Armstrong should have colonized the moon rather then coming back.
Your delta V budget seems a little low from LEO.Figures I've seen for reaching Mars surface from LEO run higher...aerobraking away a Km/sec or two?http://www.lr.tudelft.nl/index.php?id=29335&L=1