SpaceX and cis-lunar Space Tourism

[RanulfC]

It will be optimized for Mars. But again, who cares? Until the day at least when someone comes with a solution that is more cost effective for the moon. I don't see that happen any time soon.

"Technically" it's already "happened" in that more efficent and effective Lunar transport systems have already been considered and designed Like just about every OTHER transport system destination in "space" the main issue has been and remains actually "proving" a market. I've also been pointing out that even "optimized" for Mars doesn't mean it can't be "effective" for the Moon as long as THAT is a consideration during the design process. As an "after-thought" its a serious liability...

I'll repeat what I've said before though; Nothing I've seen has made me think that EM is seriously considering Lunar or even Cis-Lunar "tourism" as part of SpaceX's business. He mentioned having an MCT land on the Moon to "prove-a-point" but that seems to be aimed at achieving a "stunt" not a precident for a business plan. I will admit that EM is giving the appearance of opening consideration for more in depth "infrastructure" but he's been pretty careful to avoid saying that SpaceX will specifically develop any of it.

At this point EM seems to have SpaceX set on course for providing for a "high-traffic" business model for LEO as the "near-term" goal. Following this he plans on moving to the methane powered Raptor engines and designs derived from that which will culminate in a BFR and/or MCT design built for going directly to Mars. Everything points to him leaving "development" of Cis-Lunar space to someone else, and if no one does then he will not care since it is not a factor in his planning.

Yes, propellant is a problem assuming ISRU on Mars and no ISRU on the moon. One way around that is launch two vehicles on a moon trajectory. One being a tanker. Transfer fuel from the tanker after TLI and let the tanker return on a free or nearly free return trajectory. More expensive than Mars maybe, but maybe not because the MCT will be back much sooner for reuse. But try to beat the per ton price to the moon with any other archictecture.

I got "dissed" in the MCT thread for suggesting the use of tankers as you recall I'd say rather than launching them together the Tanker will be launched and landed on the Moon first and refueling will take place there. Everything is much simpler that way. But in any case I don't see the MCT being "effective" in a Lunar mission role, not if it's "optimized" as much as has been discussed for Mars. I'm still hoping to be pleasntly surprised when actual details emerge

Randy

[sheltonjr]

I have developed a notional MCT to go to Mars that has the following characteristics that can be launched with  2 250 MT Fully reusable SpaceX BFRs. The first one is the MCT and the second one tops off the fuel.

13m diameter base, 15 Degree side walls, 20m tall (Big Dragon shaped capsule)
30 MT MCT Empty weight, 70 MT Cargo, 228 MT of Fuel (CH4/LOX), 700 m3 of cargo/crew/systems volume
It has 5.325 km/s delta velocity capability to Mars and 7.173 km/s back to Earth.

As a thought experiment for this thread I wondered if it would be capable for a Moon mission. The resulting capability was:

Reduce MCT empty weight to 28 MT (Which is just a wild guess anyway, Smaller Launch Engines)
14 MT Cargo to the Moon, and 2 MT returning to Earth.
1-? MT of the Cargo may be batteries/Fuel cell to survive the Lunar night if the mission is more than two weeks. These would stay on the Moon to reduce return mass.
It has 6.1 km/s delta velocity capability to the Moon and 2.8 km/s back to Earth.


Summary:
* Big loss of cargo capability due to no aerocapture and refueling capability on the Moon.
* Added battery/fuel cell system to last the Lunar night would be required.
* MCT Main engine would have to be reduced to a Super Draco equivalent. MCT Mars Launch engine would be too much thrust.

* Still, 14 MT to the Moon and 2 MT returning would be much better than anything done previously.
* 2/3 MCT and 1/3 cargo is not very efficient, but if everything is reusable it only cost fuel and reprocessing.
* 700 m3 of space for 14 MT of cargo. Lots of room for crew, supplies, scientific equipment and rovers.

* I think it would be worth the minor mods.

Apollo Lunar Module Stats:
6.7 m3 volume
4.2 MT Mass Dry, 14.7 MT Wet

Edit: formatting, clarity and added summary items.

[CuddlyRocket]

The problem with making "Mars" the driver behind design for HSF is that a "dedicated" Mars vehicle and transport system (such as being discussed here for the MCT) has very little utility or ability to do transportation missions to other destinations such as the Moon or an asteroid without serious redesign or large "wasted" capacity per flight. So while MCT COULD land on the Moon to "prove-a-point" it won't be as capable of efficent as a vehicle DESIGNED to do so.

Who cares? As long as it's not more expensive than any alternative (if there is one) and it can do the mission what's it matter if there's spare capacity or it's not optimally designed for that mission scenario?

"Who cares" is a good question actually If the MCT is designed as is being discussed in that specific thread then landing it on the Moon, while possible to "prove-a-point" (funny but no one has commented on how ominus that sounds rather than reassuring ) would only be a "stunt" and prove that it would NEVER be "less expensive" than an alternate. If it has to carry all the "gear" for the entire trip that it would normally carry and USE on Mars but has no use on the Lunar mission, there is going to have to be extra propellant carried to deal with a fully propulsive mission profile.

But propellant is dirt cheap (relatively speaking, in this context). It's less than $250,000 for a F9. You can get an awful lot of 'extra-propellant' missions for the costs of developing an entirely separate lunar vehicle and transport system.

SpaceX optimises for cost, not performance. A Mars-optimised vehicle and transport system that can also work for the Moon may well be cheaper doing so than a separate Moon-optimised one through economies of scale.

Now of course there are ways to help make such an architecture work at least "well" for both (or more) destinations, but you are going to run into "costs" if the vehicle is heavily "optimized" for delivery costs to any specific destination. If one only "cares" for Mars as a destination and optimizes "costs" for that particualr destination then the "cost" of going anywhere else is going to be that much higher.

People have been "assuming" that MCT will be highly optimized towards Mars which would make it far less optimum for Lunar operations, in many cases to the point where it would not be cost effective to use to transport people/cargo anywhere BUT Mars

Not necessarily. There are costs incurred (and savings foregone) in having two separate vehicles and transport systems. These may well outweigh the additional costs due to a sub-optimal design for a lunar mission; especially if your reusable MCT is sat around doing nothing in the 15-20 months between its return to Earth and the next Mars launch window!

The question as to whether it is more economical to have multiple vehicle types optimised for various routes or a single one that is therefore sub-optimal for some routes is well understood in the airline industry; and the conclusion is that it is often the latter that is more profitable. And the difference usually comes down to the amortisation of fixed costs. In fact, it could well be more profitable overall for SpaceX to use the MCT to run lunar missions at a loss!

"I" care because I'd really like to see SpaceX (and EM) avoid the "obvious" conclusion that being a "mutli-planet" species means "Earth-and-Mars" when it could mean so much more so easily

Randy

I don't think SpaceX or Elon have drawn that conclusion. But they may well have drawn the conclusion that a Mars-optimised transport system is overall the most cost efficient way to go!

[JohnFornaro]

Mars is dry, but the Moon is drier, and that matters.  Mars has little atmosphere, but the Moon has far less, and that matters.  Methane can be produced fairly easily on Mars.  Try that on the Moon.  Mars also has more gravity.  We don't really know the long-term health effects of either Mars' or the Moon's gravity, but Mars gravity is closer to Earth's, so it may well be that Mars is significantly better for your health.  Mars has a day-night cycle similar to Earth's.  The Moon doesn't, and it is hard to bake in the direct sun for two weeks, then shiver through a two-week night.

I don't think any of those issues matter in the near term, since proximity rules. 

From the department of clinical interest, while you point out that Mars' gravity is twice that of the Moon's, remember that many Mars first advocates argue that landing in the Moon's gravity well is a major showstopper.  Go figger.

In the near term, lunar flybys sound like quite the adventure for well heeled tourists.  Still, they're not going to want to orbit the Moon for four weeks; spend a couple of days up there, conceive, and then come home.

The moon is closer from a travel time, and communication perspective but it's not that much closer from a deltaV perspective, as upthread analysis shows.

The deltav argument fails because it is not the pertinant human statistic; time is.

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

... the requirements of a lunar lander/ascent vehicle are so vastly different from the requirements of a Mars lander/ascent vehicle that its counterproductive to try to combine them or use one to develop the other.

It's like trying to develop a combination screwdriver and hammer, or trying to develop a screwdriver that will lead to a hammer. ...

The two landers are different.  But your analogy fails, in that a lunar lander is more like a VW bug, and the martian lander more like a Tesla.  There is a conceptual path evolving from the more primitive one to the more advanced one.

Possibly another analogy would be a quarter inch drill compared with a one inch magnetic drill.

[guckyfan]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

[RanulfC]

But propellant is dirt cheap (relatively speaking, in this context). It's less than $250,000 for a F9. You can get an awful lot of 'extra-propellant' missions for the costs of developing an entirely separate lunar vehicle and transport system.

"Depends" really because we don't KNOW what MCT is going to be like, it's mission mode, design, etc. Propellant is "realtivly" cheap, but not if it ends up "costing" you somewhere else.

Not necessarily. There are costs incurred (and savings foregone) in having two separate vehicles and transport systems. These may well outweigh the additional costs due to a sub-optimal design for a lunar mission; especially if your reusable MCT is sat around doing nothing in the 15-20 months between its return to Earth and the next Mars launch window!

True, but then again WHY is your MCT sitting around in the first place "Down-time" is the bane of any transportation system and I'm sorry if I've given the impression that I somehow don't SEE the logic of using a "sub-optimal" system IF you've got it, but MY point was and remains that "supposing" using MCT for Lunar missions somehow assumes MCT's facing "sitting-around" somewhere instead of doing their "job" which is flying to Mars. Couple it with the fact that any "optimized" transport system is going to eat the lunch of a sub-optimum system and I really don't see MCT managing a Lunar role UNLESS, (key point since the begining) its not soley dedicated to Mars as has been discussed

The question as to whether it is more economical to have multiple vehicle types optimised for various routes or a single one that is therefore sub-optimal for some routes is well understood in the airline industry; and the conclusion is that it is often the latter that is more profitable. And the difference usually comes down to the amortisation of fixed costs. In fact, it could well be more profitable overall for SpaceX to use the MCT to run lunar missions at a loss!

I hope you weren't expecting me to disagree here I fully understand the line of reasoning, however, (to continue the analogy hopefully not far enough to shatter ) the main reason why airlines don't run 747s on "feeder" air-routes is far to much "capacity" than is needed. By the same token though airlines have been really wanting to increase the range and avialability of smaller airliners to longer routes but have never found the "incentive" to take that as far as specialty built aircraft or "non-standard" operations. (Till I looked at the subject I never really KNEW just how far the airlines had taken the idea of adapting air-to-air refueling but they have actually spent serious time and money into checking the feasabilty of making it a 'routine' airline operation

If SpaceX has MCT's "sitting-around" for months on end then, yes it would make sense to use them for things like Lunar runs. So far I've not seen anything like that much "time" between runs mentioned, in which case taking an MCT out of service to run to Luna doesn't make enough sense to justify

"I" care because I'd really like to see SpaceX (and EM) avoid the "obvious" conclusion that being a "mutli-planet" species means "Earth-and-Mars" when it could mean so much more so easily

I don't think SpaceX or Elon have drawn that conclusion. But they may well have drawn the conclusion that a Mars-optimised transport system is overall the most cost efficient way to go!

I don't think they have either, (but you can't tell that from the "speculation" thread and I don't DISAGREE that a "Mars" optimised system might be the way to go for a general "Interplanetary" transport system. But I also know that it is very often easier to "tweek" a general system for an optimum solution than to try and tweek an optimum solution to a general situation.

Randy

[oldAtlas_Eguy]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

Right next to these cold traps on the moon are continuous sunlight peaks for 24/365 operations support.

[RanulfC]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

As John says and I'll point out the fact that LUNAR ISRU was proposed and studied long before Mars ISRU so there's no way to make a case of one having and the other not having local resources!

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

Far, oh so far from the case I'm afraid. You can "disagree" all you want but you should keep in mind that "water" isn't the only possible source of ISRU and never has been. The "fact" that water on Mars is probably more prevelant doesn't negate the fact that the Moon has had extensive and indepth study done on how to and what local resources are available.

Mars, despite the best efforts of some does not get any "freebies" as a destination simply because some "wish" it were so. It has advantages, yes, so does the Moon and the biggest remains proximity which despite all the rhetoric to the contrary is STILL a major factor.

Even more so since this thread is "SpaceX and CIS-LUNAR Space Tourism" lets back off the versus fight and get back on track shall we?

Randy

[JohnFornaro]

Going to the moon and back is harder delta-v wise if there is fuel ISRU on Mars and not on Luna.

That difference cannot be granted until the lunar ice craters have been assayed and lunar prop ISRU disproven. 

If there is sufficient water ice on Luna, then the prop factory cannot be unilaterally granted to Mars, but not Luna.

I disagree. Assuming there is water on the moon is a fair assumption. But getting it from those cold traps is hard and requires very advanced technology. Then processing it to fuel and get it where it would be needed for launch is not easy again. Two weeks sun and then two weeks night is very harsh on a station or settlement also.

On Mars water is at the places we would want to go anyway.

So the proof is on those who want to go to the moon.

That the "proof is on those who want to go to the Moon", is certainly true, if your several assumptions are correct:

Assuming there is water on Mars is a fair assumption. Getting that water is easy and does not require very advanced technology. Then processing it to fuel and get it where it would be needed for launch is very easy again. Twelve hours of weak sun and then twelve hours of a very cold night is not at all harsh on a station or settlement.

Are your assumptions as easy as you must be asserting?

[guckyfan]

That the "proof is on those who want to go to the Moon", is certainly true, if your several assumptions are correct:

Assuming there is water on Mars is a fair assumption. Getting that water is easy and does not require very advanced technology. Then processing it to fuel and get it where it would be needed for launch is very easy again. Twelve hours of weak sun and then twelve hours of a very cold night is not at all harsh on a station or settlement.

Are your assumptions as easy as you must be asserting?

Yes certainly.

That weak sunlight near the equator is about as much as Germany gets on average, probably more because of long time of clouds. When a Mars rover can find visible amounts of ice by scratching the surface it cannot be too hard to collect. The methods of transforming water and CO2 to methane and LOX  are very easy, basic chemistry. The amount of energy needed is a lot in total but not that much assuming a two year window for production.

Actually I see one major problem in getting the fuel from the production site a few hundred meters or a km to the launch vehicle while on the moon the distance would be a lot larger, hundreds of km if not more. I don't see a station right beside those cold spots. But that last assumption may be wrong.

[RanulfC]

That the "proof is on those who want to go to the Moon", is certainly true, if your several assumptions are correct:

Assuming there is water on Mars is a fair assumption. Getting that water is easy and does not require very advanced technology. Then processing it to fuel and get it where it would be needed for launch is very easy again. Twelve hours of weak sun and then twelve hours of a very cold night is not at all harsh on a station or settlement.

Are your assumptions as easy as you must be asserting?

Yes certainly.

That weak sunlight near the equator is about as much as Germany gets on average, probably more because of long time of clouds. When a Mars rover can find visible amounts of ice by scratching the surface it cannot be too hard to collect. The methods of transforming water and CO2 to methane and LOX  are very easy, basic chemistry. The amount of energy needed is a lot in total but not that much assuming a two year window for production.

Actually I see one major problem in getting the fuel from the production site a few hundred meters or a km to the launch vehicle while on the moon the distance would be a lot larger, hundreds of km if not more. I don't see a station right beside those cold spots. But that last assumption may be wrong.

Getting into OT-ISRU issues here but...
JF:"Are your assumptions as easy as you must be asserting?
GF:"Yes certainly."

No, certainly Again, your "assuming" from a false basis that "water" is the key to any ISRU... Energy is actually the key and by "giving" yourself a two-year production "window" on Mars your ignoring the fact that much more can be done with a two-WEEK production window on the Moon. The "cold-traps" at the Lunar poles are a "nice-to-have" but they were never the basis of Lunar ISRU planning or study and you're ignoring past work in order to concentrate on a singular NEW Lunar development rather than the full situation.

Don't make assumptions you can't support to support your point

Randy

[guckyfan]

Getting into OT-ISRU issues here but...
JF:"Are your assumptions as easy as you must be asserting?
GF:"Yes certainly."

No, certainly Again, your "assuming" from a false basis that "water" is the key to any ISRU... Energy is actually the key and by "giving" yourself a two-year production "window" on Mars your ignoring the fact that much more can be done with a two-WEEK production window on the Moon. The "cold-traps" at the Lunar poles are a "nice-to-have" but they were never the basis of Lunar ISRU planning or study and you're ignoring past work in order to concentrate on a singular NEW Lunar development rather than the full situation.

Don't make assumptions you can't support to support your point

Randy

So you assume extracting water from regolith? That's really going into exotic engineering. I am not following you there. And as you are right this is OT on this thread so let us stop.

[RanulfC]

That the "proof is on those who want to go to the Moon", is certainly true...

Just an FYI John but this isn't true and never has been, the "burden-of-proof" has always been on the one making the assertion of "truth" not only to provide proof of the statement but also to provide and/or discuss the basis for assumptions involved

As I pointed out to GF, the "assumption" that Lunar ISRU is predicated on water being available is a RECENT development and as never the actual basis for Lunar ISRU research. Nice-to-have, but not the basis so by using that as the "base" assumption for a "Mars-vs-Moon" argument its up to GF, not the Lunar advocates to provide "proof" of his argument. First he has to rule out all the previous work done on non-water based Lunar ISRU which I believe would be difficult for him to say the least to do

ISRU has always been about using "local" resources to most extent possible and just because Zubrin happened to have an "epiphany" to apply it to Mars doesn't mean much OTHER than how it was applied to Mars. The Moon was planned ISRU territory long before Bob got ahold of the idea and no matter how he and others try to spin it, his "success" at getting folks to listen to the IDEA of Mars ISRU is directly based on peopl pushing LUNAR ISRU for years prior to him rather than it being a "brillant" idea in and of itself

Randy

[RanulfC]

So you assume extracting water from regolith? That's really going into exotic engineering. I am not following you there. And as you are right this is OT on this thread so let us stop.

You're going to throw THAT argument out and then call for stopping??!!??

Let me say it this way: Why do you "assume" that water is REQUIRED for ISRU of ANY type? Lunar propellant ISRU dates from the mid-70s and ASSUMED that no significant water was available from the regolith to work with. Depending on what propellant you wanted to make (start off by NOT assuming that Meth/LOx or LH2/LOX are a "requirement" no matter what RZ says determines your level of engineering needed. None of the studies saw a need for "exotic" engineering though some were a lot more difficult that others.
(Getting actual "water" from normal lunar regolith is actually EASY you just have to process a lot of it to get amounts equal to ice-mining. Water and Oxygen were always outputs of regolith processing)

If, as we're assuming given its a SpaceX thread, that the transport system will use Meth/LOX propulsion then the ISRU issue becomes less about producing ISRU Methane than producing ISRU LOX which was always a Lunar ISRU "staple" for production. Methane is brought in with the transport as part of the payload and ISRU LOX loaded on. Any traffic model has in-place storage building up rapidly from the start, especially if some seed-stock is brought in early and local energy and resources used to jump start production. (The same situaton as proposed on Mars actually)

The main point everyone needs to understand is that there is NO place in space where ISRU is "impossible" to do. Everyplace HAS resources that CAN be used it's just that not all places have the EXACT same resources in the same concentrations so ISRU has to be "adjusted" to fit each place. Different resources may take different methods to extract and it may take more or less of a process TO extract but it can be done.

Randy

[guckyfan]

So you assume extracting water from regolith? That's really going into exotic engineering. I am not following you there. And as you are right this is OT on this thread so let us stop.

You're going to throw THAT argument out and then call for stopping??!!??

Let us look for a proper thread. Not here.

Edt: Actually no. I responded too early. I am not willig to argue on the basis of your assumptions.

[MP99]

I have developed a notional MCT to go to Mars that has the following characteristics that can be launched with  2 250 MT Fully reusable SpaceX BFRs. The first one is the MCT and the second one tops off the fuel.

13m diameter base, 15 Degree side walls, 20m tall (Big Dragon shaped capsule)
30 MT MCT Empty weight, 70 MT Cargo, 228 MT of Fuel (CH4/LOX), 700 m3 of cargo/crew/systems volume
It has 5.325 km/s delta velocity capability to Mars and 7.173 km/s back to Earth.

As a thought experiment for this thread I wondered if it would be capable for a Moon mission.

After fuelling in LEO, MCT with 70 mT cargo can get itself to EML-2 (<4 km/s?), with substantial residuals .

IIRC, the round-trip EML2-surface-EML2, is in the ballpark of your 5.3 km/s capability, so after refuelling MCT can land its 70 mT on the surface then lift something close to that back to EML2 without refuelling on the surface. I'd suggest landing at beginning of Lunar night, and taking off not much after dawn in order not to boiloff the propellants.

* MCT Main engine would have to be reduced to a Super Draco equivalent. MCT Mars Launch engine would be too much thrust.

MCT landing on the Moon is heavier than MCT landing on Mars (also carries ascent prop), so you can use the same propulsion without T:W issues.

More interestingly, the EML2-surface-TEI dV isn't much more than EML2-surface-EML2, so substantial payload could go back to Earth's surface if you assume no propulsion required for Earth reentry.

Methalox is storable at EML2 - basically same boiloff control technology that will be required for a Mars mission, given quite similar thermal environments. Also, given that trip times for the prop to EML don't matter much (it's the same methalox-is-storable environment), this can get from LEO to EML via a slow-boat trajectory for ~3.2 km/s plus a three-month transit time.



This trades multiple MCT launches (prop delivery to EML) against Mars needing an ISRU plant to enable return, so it could be available sooner without waiting for that tech development. While it's capable of the same 70 mT "biggest smallest" chunks that you have for building the Mars infrastructure, you can trade lower cost by taking on less prop at EML (less tanker flights).

Recovering those tanker stages could be fun, though!

cheers, Martin

[guckyfan]

After fuelling in LEO, MCT with 70 mT cargo can get itself to EML-2 (<4 km/s?), with substantial residuals .

IIRC, the round-trip EML2-surface-EML2, is in the ballpark of your 5.3 km/s capability, so after refuelling MCT can land its 70 mT on the surface then lift something close to that back to EML2 without refuelling on the surface. I'd suggest landing at beginning of Lunar night, and taking off not much after dawn in order not to boiloff the propellants.

..............

MCT landing on the Moon is heavier than MCT landing on Mars (also carries ascent prop), so you can use the same propulsion without T:W issues.

................

Recovering those tanker stages could be fun, though!

cheers, Martin

EML-2 might be an interesting staging point for reusable moonlanders flying between lunar surface and EML-2.

MCT goes back to earth. No point in going through EML-2. My idea about refuelling is send one MCT and one tanker through TLI, refuel MCT in flight and let the tanker RTLS after looping around the moon with very little or no delta-v after TLI except for the landing burn, which is very small.

[sheltonjr]

After fuelling in LEO, MCT with 70 mT cargo can get itself to EML-2 (<4 km/s?), with substantial residuals .

IIRC, the round-trip EML2-surface-EML2, is in the ballpark of your 5.3 km/s capability, so after refuelling MCT can land its 70 mT on the surface then lift something close to that back to EML2 without refuelling on the surface. I'd suggest landing at beginning of Lunar night, and taking off not much after dawn in order not to boiloff the propellants.

..............

MCT landing on the Moon is heavier than MCT landing on Mars (also carries ascent prop), so you can use the same propulsion without T:W issues.

................

Recovering those tanker stages could be fun, though!

cheers, Martin

EML-2 might be an interesting staging point for reusable moonlanders flying between lunar surface and EML-2.

MCT goes back to earth. No point in going through EML-2. My idea about refuelling is send one MCT and one tanker through TLI, refuel MCT in flight and let the tanker RTLS after looping around the moon with very little or no delta-v after TLI except for the landing burn, which is very small.

Yeah, A lot of interesting permutation are possible. I think what I showed was the simplest possible worst case option with refueling only in LEO.  (Actually a High Eccentric Earth orbit).

Analyzing this further is fruitless in my opinion being a largely fictitious though theoretically feasible vehicle if I have the MCT empty mass anywhere close. 

Thanks for reading and responding to my post.

[RanulfC]

Let us look for a proper thread. Not here.

Not sure there CAN be one really, what we're essentially argueing is the question of ISRU viability

Edt: Actually no. I responded too early. I am not willing to argue on the basis of your assumptions.

Saw that coming actually, then again "I" am not willing to let the idea that Mars is the only possible place to do ISRU go un-challenged

Randy

[meekGee]

I say this as the one who started the thread, and who is on the "Mars side" of the ISRU argument.

The words in the title add up to a description of what this thread is about.  There is no "Mars" in "SpaceX and cis-lunar Space Tourism"

Randy - see you on the Mars HSF thread, we can slug it out there.