Author Topic: MCT Speculation and Discussion Thread 4  (Read 610787 times)

Offline JamesH

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Re: MCT Speculation and Discussion Thread 4
« Reply #400 on: 08/18/2015 03:46 PM »
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.

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.

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.

Online guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #401 on: 08/18/2015 03:59 PM »
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.

Actually performance data for MCT have been very consistent over time. Data on Raptor have changed but they said, less thrust of a single Raptor, more Raptors, total thrust and performance a constant.

Offline sghill

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Re: MCT Speculation and Discussion Thread 4
« Reply #402 on: 08/18/2015 04:06 PM »
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!?!

« Last Edit: 08/18/2015 04:24 PM by sghill »
Bring the thunder Elon!

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #403 on: 08/18/2015 04:27 PM »
New info from Musk about the Raptor and MCT(and sorry about the crossposting):

Quote from: Elon Musk
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!

Looks like the Raptor will run oxidizer rich. That puts its niche even closer to the BE-4.

No 3.8 O/F is fuel rich, 16 units of mass of CH4 combines with 64 units of mass of O2 for a stoichiometric reaction which would be a ratio of 4.0 - this makes 3.8 slightly fuel rich but not by much.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #404 on: 08/18/2015 05:15 PM »
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. 

True, but as is pointed out, the design isn't finalized yet and lots can change. And while many here might disagree with me, I think even the target payload could change if a bunch of good engineering shows a "sweet" spot of overall design that makes a different payload range than 100t have a higher overall system performance.

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.

While I have no proof to the contrary for BFR, 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). As for the pace of the Dragon 2, it does have a customer and that customer is as much setting the pace as SpaceX cash flow is. Neither Dragon were built for SpaceX internal projects, they were developed for a client with a schedule worked out mutually. The fact that there were slips in that schedule can be attributed to both sides, but there was no motivation to move either faster than the pace needed to meet the client schedule so, any delay on the client side or the SpaceX side pushed that schedule further to the right.  If SpaceX never had a client for a Dragon the design and the crafts life cycle would have been completely different, the first version would probably have been designed for passengers, and it would have launched much later than it did, but they might have flown a manned one by now.  The way things are happening however they are getting to do all the engineering they need to develop a passenger carrying spacecraft paid for, and they get a craft that, hopefully is a superset of their requirements and NASA's requirement.

For BFR and MCT it is believable to me that SpaceX will spend several billion of money raised from: investors, cash flow from their cash flow positive activities, possibly even debt as SpaceX matures its other businesses. In fact it seems far more believable than a company with less a little over $100M in cash and only the almost empty pockets of a dot com boom instant millionaire wiz kid for more capital making a brand new rocket using two new liquid fuel engines, their own avionics, tanks etc.  SpaceX has far more wherewithal and potential funding sources proportionally to attack this problem than it did when it was founded.


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.
Actually that would be very inconsistent with everything that Elon Musk has done to date. From the start hyperloop was an Elon concept looking for a non Elon home. He introduced it that way and described his process for arriving at the idea publicly. He has been as open about his intent to colonize Mars. His first plan was to inspire people to want it by sending a greenhouse experiment to Mars. He even tried to make that work, and I suspect somewhere early on, he will pay homage to that original idea in some early launch of an unmanned craft to Mars, but if he does it will be as significant as the wheel of cheese on the first Dragon flight. He publicly explained each of the step changes in his rational towards getting people on Mars, and has all along since starting to build rockets said that he is building towards creating the infrastructure needed to settle Mars. If you consider his actions with Tesla and Solar City in the way he announces business development, everything he has done suggests that what he is doing right now with SpaceX includes several money making adjuncts that also carry it towards its ultimate goal. SpaceX also exists to help Tesla and Solar city if you haven't noticed, and if needed they will help SpaceX.

The idea that Musk will only develop BFR/MCT if he can sell it to a public funded agency is not consistent with what he has done to date. However, if he can get that funding or more likely he makes a change to the way this sort of project interacts with goverments and NGO's and gets a new model of corporate and philanthropic exploration to come about, he will. His is probably the only person who can make that change work even. However, if he does make it work many will say that it only worked because he conned others into following his flawed vision, rather than acknowledging that while many elements of his vision are arbitrary rather than optimum, it is his ability to create the organization that transforms his vision into reality that is making it happen rather than flaws and disingenuity.

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.

So does the Raptor count as a "part"?

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.

As could I, but I would bet on several elements of my views on this and it is the SpaceX track record to date, and Elon's consistent communications style about what he does, that make me feel as I do about it.

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 hope it doesn't come to that. 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).
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline enzo

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Re: MCT Speculation and Discussion Thread 4
« Reply #405 on: 08/18/2015 10:27 PM »
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).
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.

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.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #406 on: 08/18/2015 11:08 PM »
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).
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.

Dangerous as in has a high risk of failing? Well not doing it that way gives it a 100% chance of failing. Or do you do you mean dangerous to bystanders somehow?

I certainly think Musk has plans to raise more equity in all of his companies. My third post on NSF outlines one possibility of how he uses an IPO of SpaceX to both increase the value of SpaceX and create the funding for another private venture (possibly even a not for profit) to hire SpaceX to colonize Mars: http://forum.nasaspaceflight.com/index.php?topic=35529.msg1250251#msg1250251
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 really don't want respond to the religion part but it really offends me that someone can imagine that those actions (and plenty of others) did not help keep it from being for all mankind.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline JamesH

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Re: MCT Speculation and Discussion Thread 4
« Reply #407 on: 08/19/2015 10:33 AM »
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).
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.

Not as dangerous as the time when he needed to fund both SpaceX and Tesla at the last minute....

Although I would comment that what you say above is pretty much how many big companies work...they sell stuff to keep going. They invest money so that can make stuff they can sell.  SpaceX and Tesla are investing a lot, but the payoffs could be massive (esp. Tesla and the next couple of models). That should encourage investors should they need them.

Offline Bynaus

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Re: MCT Speculation and Discussion Thread 4
« Reply #408 on: 08/19/2015 02:00 PM »
Has anyone here considered to take Tim Urban's drawings of the MCT a bit more serious as a possible sneak peak from Musk's side regarding the final design? After all, the publication of the article was delayed because of something that was outside of Tim's control - but the cause for the delay was never really identified. In the "waiting" post, the stick figure is shown drawing an MCT fleet approaching Mars... Was Tim perhaps waiting for a rendering of the planed look of the MCT? If you look at the drawn MCTs, they look very detailed for being purely generic, e.g., look at this angled, extensible (?) solar panel on the "thick" left part of the MCT. And could the dark end (right part) be a heat shield? If we take this speculation serious for a moment - can we make sense of this design?

See: http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-content/uploads/2015/08/SpaceX-F-782x530.jpg

Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #409 on: 08/19/2015 03:37 PM »
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?
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Online guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #410 on: 08/19/2015 03:47 PM »
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?

Recently he was very clear on this. It is 100t pure payload, to be unloaded and left on Mars while the whole vehicle flies back. Earlier statements were less clear and one could think it includes the empty vehicle but no longer.

Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #411 on: 08/19/2015 04:06 PM »
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?

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).
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline su27k

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Re: MCT Speculation and Discussion Thread 4
« Reply #412 on: 08/19/2015 04:47 PM »
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.

They don't have enough money for Dragon 2 because Falcon 9 (and Dragon 1) has a low launch rate, and their engineering resources are focused on Falcon 9, Falcon Heavy and Dragon 2. If they can get their launch rate up, their cash flow situation would improve. And after F9/FH/DV2 are completed, they would have the engineering resources for BFR and MCT.

Online guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #413 on: 08/19/2015 04:53 PM »
Someone from SpaceX, not sure who, said the design of MCT is changing because they learn so much from Dragon 2. Everything they do is part of the learning curve.


Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #414 on: 08/20/2015 01:48 AM »
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?

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).

Appreciate the response.  Makes sense.  Agree with the tanker #s.
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

Then the return trip to Earth from Mars' surface runs almost up to 8Km/sec.  Of course the returning MCT will only have the 50mT dry weight plus say just 10-20mT "payload resulting in "only" a mass of 60-70mT.  Using the rocket equation, that MCT won't even need a full load of ISRU propellant to meet delta V return needs from Mars to Earth.
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Offline Vultur

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Re: MCT Speculation and Discussion Thread 4
« Reply #415 on: 08/20/2015 04:22 AM »
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.

Apollo was designed for brief forays, MCT will presumably be designed for colonization. It's not comparable.

EDIT: Also, a Mars mission is going to be 2-3 years anyway so you need long term life support even for "flags and footprints". So the difficulty gap between "flags and footprints" and colonization is much smaller for Mars than the Moon.
« Last Edit: 08/20/2015 04:25 AM by Vultur »

Online guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #416 on: 08/20/2015 06:16 AM »
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

Your link gives 5,7km/s for LEO to LMO. Landing should require less. That's assuming the LMO figure is with propulsive braking. Not going into LMO saves a lot and much of the braking for landing is done with aerobraking. If I remember correctly usually 1km/s propulsive braking was usually assumed for Mars landing.

Offline MikeAtkinson

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Re: MCT Speculation and Discussion Thread 4
« Reply #417 on: 08/20/2015 09:31 AM »
[Here is an update of a post of mine from 4th April on thread 3]

Lets sum up what  know (or at least reasonably can expect) of MCT.

Payload to Mars surface 100 tonnes - initial flights are likely to have lower payload mass, perhaps as low as 50 tonnes.

Up to 100 passengers and crew - initial flights are likely to carry far less, perhaps around 10, later flights perhaps a few more.

100 SUV volume - it is unclear if this is external volume which could be 2000m3 or internal volume perhaps 700m3. It is also unclear if this refers to total MCT volume or usable cargo volume or pressurized volume.

Something like 2-10 cargo flights to each crew flight - cargo flights are the major cost driver. Elon says 10 cargo flights, but that seems more than is needed.

Launched on a 100-150 tonne BFR (fully reusable) - equivalent to 200-300 tonnes expendable rocket. It is probably possible to go as low as 50 or as high as 600 tonnes (reusable) and still make the architecture work, but these seem to go away from the optimum. A fully reusable BFR with return to launch site (RTLS) would place 190-280 tonnes into LEO. So that with the MCT as its own second stage, MCT+payload is a bit less than BFR expendable payload.

MCT is its own second stage. This seems to be confirmed by WaitButWhy blog.

There is also a tanker second stage.

Cargo and crew flights will use a similar MCT configuration - technologies that are only useful for crew flights are unlikely.

MCTs to be returned to Earth so that they can be reused within 1 synod. This might not apply to early flights, some might be left on Mars, others might be returned later. WaitButWhy blog says 2 synod reflight.

Reflight within 1 synod implies fast cargo flights. Most architectures employ low energy cargo flights which save on IMLEO.

Crew accommodations are just cargo. It seems likely that crew and cargo MCT are almost identical with all additions for crew being treated as cargo.

Methane/Oxygen main fuel and lots of it.

Main engine is raptor. Used for TMI, Mars ascent, TEI, also probably used for Mars landing.

Raptor size is in the range 500-1500klb. Optimisation still probably taking place, but 500-700klb seems most likely. Landings on Mars using Raptor at higher thrusts would be 'sporty', but not impossible given the range of potential MCT masses and throttling levels.

Fully reusable - both MCT and BFR. This has implications for Mars and Earth entry descent and landing.

Land the whole MCT on Mars. The simplest architecture. Given that the MCT will be large and fully reusable and uses Mars derived propellants it is difficult to improve on this.

Propellant transfer in LEO, either from tankers to MCT, or from tankers to propellant depot to MCT.

Multiple tanker flights per MCT. Could be as high has 12 or as low as 3 depending on BFR size, MCT size, etc. perhaps 6 is a reasonable estimate.

Multiple constraints means that the MCT design is hard. All aspects of the flight (Earth launch, TMI/TEI, transit, Mars EDL, Mars surface ops, Earth EDL) put constraints on the MCT, it is a very difficult problem to satisfy them all. Finding it impossible to meet all of them would be the most likely reason to change from a land-it-all, return-it-all in 1 synod using methane architecture.

It is highly probable that Solar power will be used during transit. Lightest and cheapest solution, but it does create difficulties in furling the solar sails for landing.

It is likely that Solar power will be used during surface ops. Cheap and easy to scale.

Electric Propulsion may be used during transit. But probably only as a secondary propulsion system for attitude control, course corrections. Large SEP stages do not fit well with a land-it-all, return-it-all in 1 synod architecture.

There seem to be 3 possible shapes for the MCT:
1. Capsule - similar to Dragon - SpaceX has lots of experience in this, but perhaps not enough lift for Mars to give a reasonable payload fraction landed - scaling Red Dragon would give a heat shield over 20m in diameter.
2. Bullet - similar to fairing - most space efficient, used on DRM 5.0, but perhaps too tail-heavy either during Mars descent or Earth descent. Actual shape may be a biconic/triconic.
3. Semi-lifting - something like ESA's IXV perhaps, gives more lift than capsules.
All three have advantages and disadvantages.

Vertical landing is likely. As this avoids the problems with horizontal landings -  load paths in 2 directions, a separate set of landing engines and does not need raising to the vertical for launch from Mars.

Separate landing engines are possible. Better match to thrust required, could possibly be used for LAS, keeps exhaust well away from martian surface which reduces debris, also might be used as a launch abort system. But add extra mass and complexity.

No Nuclear. There are no suitable reactors off-the-shelf, creating one would be time consuming, very costly and impose great regulatory burdens on the entire architecture.

Initial crews live in the MCT.

Early designs of the MCT are likely to be quite different from those at the colony stage. More experience, better technology, economies of scale and competition will all affect the MCT over several generations. 100 people for $500k each is likely 50 years away, lots can happen in that time.

The MCT and BFR factory will be built near the launch site. If there are more than one launch site, probably near water as well.

The launch site location is unknown. Noise is a major constraint, few if any places on the coast are suitable, perhaps launch from a short distance off-shore.

Two possible configurations of BFR/MCT:
1. MCT is the second stage of the BFR, with mission kits for tanker, propellant depot, crew and cargo roles.
2. MCT is payload on a two stage BFR. It would then probably make sense for the tanker and propellant depot roles to be a stretched upper stage variant, while the MCT takes on other roles.
The first option allows a larger MCT (+payload) for the size of BFR at the expense of even more constraints on the MCT design. The second option is more flexible and probably easier, but at the expense of designing an extra reusable stage.

LEO rendezvous. Use of L1 does not seem to be part of the plan. Putting the mission together at L1 gives the advantage of staging, but it seems unlikely that BFR can get a fully loaded MCT to L1 in a single launch, even with a SEL tug. Assuming BFR launch is cheap, the added complexity of L1 does not seem worth it.

No use of Lunar propellants. Production of lunar propellants and launch are highly likely to be more expensive than using BFR tanker flights. Depending on lunar propellants puts lots of unknowns on the critical path.

Direct return injection. The MCT launches and directly injects into an Earth return orbit. No stops in low Mars orbit, no propellant depot on a Mars moon. A MCT sized to go from LEO to the Mars surface is also sized correctly to go from the Mars surface back to Earth in one go (perhaps with a smaller but still substantial payload). Schemes to refuel in Mars orbit, may save a bit of propellant production on Mars but only at the expense of increased complexity.

Testing. The MCT will be thoroughly tested in LEO before flights are attempted to Mars. Multiple landings on Mars will be made before the first crew landing, multiple return flights will be made before the first crew return.

Early MCT crew may be launched on Dragon. Early crews are likely to be in the order of 10 people, it is likely that it will be cheaper to launch them on Dragon than to man rate the BFR/MCT. The MCT can also be refuelled over months using tankers without needing the crew on board (this stops the propellant depot becoming a gating item).

The cost of moving to Mars will be higher than $500k. Add in necessary equipment and supplies and cost to expand the base/colony to accommodate one more person and the true cost (long term) is probably an order of magnitude higher.

The BFR and MCT may have other uses. Other short term uses might be one way of paying for the development. SpaceX have a record of getting customers to pay for development flights.

Development over the next 5 years will not be payed for from the satellite constellation. It will take at least that long for the satellite business to be profitable, in the mean time that will be a vast capital expense.

Offline Burninate

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Re: MCT Speculation and Discussion Thread 4
« Reply #418 on: 08/20/2015 10:05 AM »
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?

First: "200mT to LEO" is something that probably corresponds to BFR the launch vehicle rather than to MCT the upper stage & lander.  Anything which lands 100mT of useful payload on the Martian surface, will be much higher than 200mT IMLEO, and this implies that one MCT mission will be the culmination of multiple propellant-carrying, and possibly multiple payload-carrying launches.

With that said, there are still big questions.

The core of the capability falls on several questions
1) Is MCT's structural/rocket-stage mass counted within this 100 tons?
2) How many pieces on the board are there: Will non-landed transit habitats be used?
3) Is MCT's human cargo, life support, & food counted within this 100 tons?
3.5) Is MCT's habitat integral to the design?
4) Is MCT's ISRU gear counted within this 100 tons?
4.5) Is MCT's ISRU gear integral to the design?
5) Does MCT need to *return* 100 tons of cargo to Earth orbit?
5.5) Is MCT's ISRU gear returned?

I think we can answer 1) with a definite 'No' based on the repetition of 'useful cargo'.

We have very little idea about how to answer 2), and there are a spectrum of possibilities: In the extreme case, MCT could just be a short-term launcher/lander attached to a very large transit habitat, whether on a cycler trajectory or a semi-cycler which remains in high Mars orbit.

Answering 3) with 'Yes' is less definite, but implied by Musk not knowing how many people could be moved within a 100 ton payload envelope, which is what it sounds like he's saying.

I would probably answer 4.5) with 'No', in the long run, but 'Yes' in the short run - I think they're trying to design a rocket that remains useful over several stages of colonization.  That doesn't provide any insight into how to answer 4) though.

My inclination is that 5.5) should be 'No', because landed ISRU gear can be useful for future missions, even just as spares, and designing a dual deployer / retractor has to be orders of magnitude harder than designing a lightweight deployer.

I really want 4) to be 'No' and 5) to be 'Yes', but a lot of that is aspirational: Apollo-style exploration of multiple locations is something I see as a required capability for a mission ( which sets up a colony initially AND reuses its landers ), and I think if you're going to send hundreds of people to Mars, it's best not to design an entirely separate spacecraft just to venture to the other side of the planet.
« Last Edit: 08/20/2015 11:23 AM by Burninate »

Offline Burninate

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Re: MCT Speculation and Discussion Thread 4
« Reply #419 on: 08/20/2015 10:22 AM »
Excellent post Mike, with a few reservations.

The one I want to tackle first is 1-synod operation.

By what mission plan can an MCT be used once per synod?  Would this be an opposition-class mission that refuels from prelanded ISRU assets?
« Last Edit: 08/20/2015 10:22 AM by Burninate »

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