Author Topic: Lunar Gateway Debate  (Read 138629 times)

Offline Archibald

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Re: Lunar Gateway Debate
« Reply #60 on: 07/30/2018 07:57 am »
Warning: what follows are random musings, extrapolating ISS current crew and cargo vehicles to LOP-G.

Let's suppose that ISS operations stops in 2024. What will happen to the varied cargo / crew vehicles developed since COTS, in 2006 ?

- Cygnus
It's a cargo vehicle. Switching from LEO to cislunar space is a bit less difficult than for a crewed vehicle. I think Orbital ATK could launch upgraded Cygnus on Atlas 551 or Vulcan, to LOP-G, with few modifications.

- Dragon and Dragon 2
SpaceX case is very interesting. Dragon can certainly ride to LOP-G, it is just a matter of picking the "right" Falcon to send it high there. While "classic Falcon 9" is not powerful enough, the Heavy can certainly do the job (hint: the now cancelled circumlunar mission: delta-V is quite close to DRO)

As for Dragon 2 - we know it was build right from the start for interplanetary reentries. Then again, even if Dragon 2 does not survives ISS demise... SpaceX does not give a damn about it.
 Because BFS/BFR is coming, and Dragon 2 looks more and more as a a "ploy" to learn the intricacies of manned space vehicles, with financial help from NASA.

So how about Boeing CST-100 ? at first glance it was build for LEO and LEO only. Then again, so was Block I Apollo. I really think that, if the end of ISS in 2024 is confirmed (perhaps in 2020 or 2021) then Boeing will lose no time building a Block II CST-100 with a thicker heatshield and redundant systems for BLEO.

So at the end of the day: if ISS really stops in 2024 and is replace by LOP-G
- Orbital ATK can do it
- SpaceX does not really care
- but Boeing might be a little embarassed.

So I think an interesting question (and perhaps a seprate thread) might be: how can CTS-100 be adapted to LOP-G and cislunar space environment ?

Side note: the fourth man in the room, DreamChaser, might be even more embarassed. Lifting bodies and more generally, winged shapes, do not like very much reentries from interplanetary speed. It can be make to work, but it will be far, far trickier than a plain old capsule.

One can also wonder about Japan HTV. Once again, H2 can't lift it to DRO. Maybe this will encourage Japan to build a more powerful variant of the H3 that could reach DRO carrying an upgraded HTV ?

As for Russia, they have some interesting possibilities. While Federatsiya on Angara is the favored option, Proton and Soyuz could do the job, too. Another alternative is Constellation services "Soyuz to the Moon" plan, where the Soyuz meets a Briz or Block D on ISS orbit.

I bet you that, once Federatsiya in service, Russia will pass the old Soyuz to a private company and start selling LOP-G tourist flights.
Three options
- Soyuz on Angara
- Soyuz on Proton
- Soyuz meets a Block D or Briz in LEO (dual launch)
« Last Edit: 07/30/2018 08:07 am by Archibald »
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Offline A_M_Swallow

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Re: Lunar Gateway Debate
« Reply #61 on: 07/30/2018 08:51 am »
Warning: what follows are random musings, extrapolating ISS current crew and cargo vehicles to LOP-G.

Let's suppose that ISS operations stops in 2024. What will happen to the varied cargo / crew vehicles developed since COTS, in 2006 ?

{snip}

IMHO There will be strong competition to take cargo and people to a LEO Bigelow spacestation.
« Last Edit: 07/30/2018 08:51 am by A_M_Swallow »

Offline A_M_Swallow

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Re: Lunar Gateway Debate
« Reply #62 on: 07/30/2018 08:53 am »
In engineering form follows function. The prime mission of the spacestation in lunar orbit needs agreeing. Then we can write the requirements.

Offline TripleSeven

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Re: Lunar Gateway Debate
« Reply #63 on: 07/30/2018 09:29 am »
if one looks very carefully at the Lunar "thing" its clear, to me anyway that NASA is setting it up to "need" only the cargo resupply of the Cygnus. 

the crewing "duties" for intermittent stays will be done (in theory at least) with only the Orion module...but resupply and probably some kind of propulsion module would come from OSC. 

they have no real need for a Dragon or Starliner...because there are no perm crews.  what NASA is trying to do with the "gateway" is recreate Apollo, ie intermittent missions just going to a place near the moon not actually on it once or so a year.


As for ISS being over in 2024.
in my view if ISS is "over by 2024" and I dont for a moment think it will...the entire "Mo" for the private human presence in space grinds quickly to a halt

Bigelow or any one else has near zero change of orbiting and sustaining anything in orbit like a private space station without at least "federal anchoring" (ie the federal government sustaining the bulk of the operations cost).  None of these companies have "real" customers...none of them have real price points, and none of them have any real product to market, other then "just being in space" (ie what are you going to do on these modules?) .  None of them are even close to launch, but if they were to launch they are the crewed equivalent of Iridium, ie bankruptcy is just a short step away.

BFR I dont think has any chance of flying  by 2024 and even if it was...1) there is no hint as to what its actual cost will be "per seat" and 2) without a cost or a product to "go to" there is no real customer base for it.

Aside from the historical lack of any evidence of being able to make a technological leap like from dragon 2 to BFR:   there is no history in technology of a "transportation" node going from single digit number of customers per flight to larger than a B737 numbers in a single leap...particularly when the transportation "node" has to provide more than transportation.  I just got back from flying a total of nearly 600 people in two sectors...and at each end of the line my companies involvement with the passengers ended with the cabin chief saying "bye".  what they did at the "end of the line" is why they bought the ticket...not something the airline has to worry about.  If you loaded BFR up and took it to orbit, what would the people do there that was worth the cost of the ticket?

Without ISS, Dragon 2 and CST will have no reason to fly...and will be very expensive to maintain without a customer guaranteed customer base and will end.

ISS is the key to our next step in space, which really is privatizing ISS operations and expansion.  We need to create a destination worth having a transportation node to go to, and then the transportation node needs to evolve in way where each step is self sustaining.

having said that, if the lunar gateway needed "private crew lift and return" both Starliner and Dragon 2 would/could be modified to do the job.  I think that "both" could also form the basis for a lunar lander as well...as could OSC's system

But I really think that the next step is at some point moving the money being spent on things useless to subsidizing private industry creating new infrastructure on ISS, and using the excess capability of that infrastructure to make money ...

if we are lucky



« Last Edit: 07/30/2018 09:39 am by TripleSeven »

Offline speedevil

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Re: Lunar Gateway Debate
« Reply #64 on: 07/30/2018 12:27 pm »
BFR I dont think has any chance of flying  by 2024 and even if it was...1) there is no hint as to what its actual cost will be "per seat" and
'Less than a long distance economy ticket'. (of the order of $1000/pax, $1m per flight)

Admittedly, this is long term.
If BFS can hit its cost goal of $5M/flight, and be certified to fly people, it can make lots of money.
$15M per flight, with 100 people equals around $150K/ticket.
A third of that goes into incremental costs, a third into paying off the airframe, and a third is profit.
At around 30-60 flights, you're in profit.

Add an initial ten flights during qualification that launch re-purposed cryogenic tanks outfitted for comfort, and you can do a week in a small hotel room with windows on the earth, with almost no development. (said tanks are $2m or so for 400m^3, leak negligible heat either way even in atmosphere, have double skins, both quite capable of supporting pressure loads with a large margin.)

You could even do a similar facility in NRHO, though the fuel cost to get there is rather higher.

If you are doing similar with launchers that can't be fully reused, and are not as capable, it gets considerably harder and more expensive.
You absolutely can't afford to spend twenty tons of launch capability on facilities for one passenger.
(Note, these are assuming SpaceX was intending to do it themselves, hence do not include launch vendor profits).

Is it reasonable to cancel LOPG now, because of BFR/NA - no.
Is it reasonable to pencil it in as a 'risk' with a specified plan to pivot over to it, and terminate all of the contracts, yes.


Offline ncb1397

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Re: Lunar Gateway Debate
« Reply #65 on: 07/30/2018 01:02 pm »

One can also wonder about Japan HTV. Once again, H2 can't lift it to DRO. Maybe this will encourage Japan to build a more powerful variant of the H3 that could reach DRO carrying an upgraded HTV ?


See slide 5 and 6: https://www.nasa.gov/sites/default/files/files/04-Ueno_Lunar_Access_Architecture.pdf

If Japan doesn't have the rocket, we could provide that and they get credit based on the cargo vehicle contribution towards their share of operating costs.

Offline TripleSeven

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Re: Lunar Gateway Debate
« Reply #66 on: 07/30/2018 01:06 pm »
BFR I dont think has any chance of flying  by 2024 and even if it was...1) there is no hint as to what its actual cost will be "per seat" and
'Less than a long distance economy ticket'. (of the order of $1000/pax, $1m per flight)

Admittedly, this is long term.
If BFS can hit its cost goal of $5M/flight, and be certified to fly people, it can make lots of money.
$15M per flight, with 100 people equals around $150K/ticket.
A third of that goes into incremental costs, a third into paying off the airframe, and a third is profit.
At around 30-60 flights, you're in profit.

Add an initial ten flights during qualification that launch re-purposed cryogenic tanks outfitted for comfort, and you can do a week in a small hotel room with windows on the earth, with almost no development. (said tanks are $2m or so for 400m^3, leak negligible heat either way even in atmosphere, have double skins, both quite capable of supporting pressure loads with a large margin.)



OK a few points.

Long term?  how do you define "Long term" ? 

"If BFS can hit its cost goal of $5M/flight, and be certified to fly people, it can make lots of money."

and with wings on Titan I can fly...but you tell me...what gives you confidence that a company that has never flown people in space, that is struggling to do that right now...and at a cost per seat about 10 times what you think that the entire flight can go for....can do that

where do you find this faith.   I am all ears.  Faith to me is the evidence of things hoped for the evidenceof things unseen...

You are going to a 5M flight ...when well has Elon flown anyone?

I dont think you and Elon are going to change technological history 

Offline speedevil

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Re: Lunar Gateway Debate
« Reply #67 on: 07/30/2018 03:25 pm »
where do you find this faith.   I am all ears.  Faith to me is the evidence of things hoped for the evidenceof things unseen...

You are going to a 5M flight ...when well has Elon flown anyone?

I dont think you and Elon are going to change technological history

Any discussion of future plans has to rely to some degree on what vendors or proposers claim about their systems.
It is certainly stronger than 'no hints of' costs, when we have actual stated prices and costs.

It's at least a starting point to consider that they are correct, in the absence of either actual knowledge of the future, or carefully reasoned informed debate, which we certainly don't have enough data for for SpaceX, and only barely for SLS.

We will know a bit more about how plausible this is in the next year with B5 more rapid reuse, which alone could significantly help with costs for lunar gateway commercial launches.
And 2020 will tell us lots more - both on the SLS and BFS tests, as well as more reuse of B5 to nail down plausibility of rapid operational costs.

Is it reasonable to bet the farm on either SLS or BFS - IMO - no.
« Last Edit: 07/30/2018 03:29 pm by speedevil »

Online envy887

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Re: Lunar Gateway Debate
« Reply #68 on: 07/30/2018 05:43 pm »
Orion/SLS (Block 1B) is supposed to have a 'surplus', co-manifested payload ability of about 10 metric tons. Perhaps the Orion could bring a tanker module with it each time to refuel a reusable Lander? Just an idea...

Hmmm.....  The Apollo LM's total propellant load (ascent and descent stages together) was about 11 tonnes.  An Apollo-style lander today could no doubt get away with less propellant by saving weight and burning, say, lox/methane or maybe even lox/hydrogen rather than NTO/Aerozine 50.  But the dry weight of the LM's ascent stage was less than a quarter that of the descent stage.  If you want a reusable lander, you're going to have to haul something roughly equivalent to the descent stage all the way from the surface back to the staging point, and that means burning a lot more propellant.  That propellant itself needs to be landed on the moon in the first place, so we're talking about a much larger vehicle.

Then there's the fact that, delta-V-wise, LOP-G is about 700 m/s further (one way) from the lunar surface than was the Apollo LM when it began its descent from LLO.

So I don't think Orion/SLS's 10-tonne co-manifested payload capability helps much for fueling a crewed lander.

It's around 5,000 m/s from EML-1 to the surface and back. That means storables need a mass ratio of about 5, methalox about 4, and hydrolox about 3.

So a hydrolox lander would have 10 t of prop, about 1 t of tanks, and 4 t for all other dry mass (assuming everything that goes down also goes up). Since the whole LEM, including both stages, was only ~4300 kg dry, that seems entirely feasible.

A methalox lander would be 10 t of prop, 0.5 t of tanks, and 2.8 t for everything else. The LEM ascent stage was ~2150 kg dry, so that would be tight but perhaps possible.

A storable lander would be 10 t of prop, 0.5 t of tanks, and 2 t for everything else. That's cutting it mighty close, but might be possible with balloon tank construction.

Offline jongoff

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Re: Lunar Gateway Debate
« Reply #69 on: 07/31/2018 05:50 am »
I wanted to share a few thoughts, though I'll admit that I haven't had the time to read everyone else's comments in detail (though I did read a few). I should also mention up-front that my startup is involved in supporting at least one of the NextSTEP habitat teams, so I can't claim to be unbiased.

I'm a bit torn on LOP-G. I think a platonically ideal Gateway could be really enabling for lunar missions, but I'm also concerned that political pressures are unlikely to let Gateway be implemented in a very useful way, but I'm also concerned that canceling LOP-G (without also canceling SLS and/or Orion) is unlikely to yield the benefits that critics assume.

To me, a platonically ideal gateway would be one that was cost-capped (say the maximum NASA contribution would be $500M), done via a PPP, and not constrained in how it was implemented (ie not required to use SLS/Orion for assembly). It would probably be in a low-ish polar lunar orbit (I think Wingo suggested 500-1000km altitude), to make it maximally useful for supporting lander missions, would incorporate propellant depot and lander servicing capabilities, and would try to keep non-logistics science capabilities to the lowest of low-hanging fruit. Keep enough docking ports available that if international partners really want to contribute a module, they can, but keep it something off the critical path for logistics support. The cost cap keeps NASA from sucking the air out of the room. The PPP part keeps it to private companies that are actually serious about trying to turn it into something useful. The orbit is selected to optimize for lower-cost lunar landers, and eventual ISRU handling. The depot/logistics focus is where the Gateway would be most useful.

I just worry that politics is pushing LOP-G in a direction far from that platonic ideal, but canceling it is likely just going to lead to another HSF program of record that is an SLS/Orion make-work project that also doesn't really enable affordable lunar exploration/development either. I know Jason Crusan, and he's doing all he can to find creative ways to do this that try to avoid some of the pitfalls of NASA business-as-usual programs, but he's got his work cut out for him.

Sorry, I'm tired enough that I think that's all I can coherently say tonight,

~Jon

Offline Archibald

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Re: Lunar Gateway Debate
« Reply #70 on: 07/31/2018 11:03 am »
Orion/SLS (Block 1B) is supposed to have a 'surplus', co-manifested payload ability of about 10 metric tons. Perhaps the Orion could bring a tanker module with it each time to refuel a reusable Lander? Just an idea...

Hmmm.....  The Apollo LM's total propellant load (ascent and descent stages together) was about 11 tonnes.  An Apollo-style lander today could no doubt get away with less propellant by saving weight and burning, say, lox/methane or maybe even lox/hydrogen rather than NTO/Aerozine 50.  But the dry weight of the LM's ascent stage was less than a quarter that of the descent stage.  If you want a reusable lander, you're going to have to haul something roughly equivalent to the descent stage all the way from the surface back to the staging point, and that means burning a lot more propellant.  That propellant itself needs to be landed on the moon in the first place, so we're talking about a much larger vehicle.

Then there's the fact that, delta-V-wise, LOP-G is about 700 m/s further (one way) from the lunar surface than was the Apollo LM when it began its descent from LLO.

So I don't think Orion/SLS's 10-tonne co-manifested payload capability helps much for fueling a crewed lander.

It's around 5,000 m/s from EML-1 to the surface and back. That means storables need a mass ratio of about 5, methalox about 4, and hydrolox about 3.

So a hydrolox lander would have 10 t of prop, about 1 t of tanks, and 4 t for all other dry mass (assuming everything that goes down also goes up). Since the whole LEM, including both stages, was only ~4300 kg dry, that seems entirely feasible.

A methalox lander would be 10 t of prop, 0.5 t of tanks, and 2.8 t for everything else. The LEM ascent stage was ~2150 kg dry, so that would be tight but perhaps possible.

A storable lander would be 10 t of prop, 0.5 t of tanks, and 2 t for everything else. That's cutting it mighty close, but might be possible with balloon tank construction.

Dang. So much for such a large and powerful rocket as SLS. Is Orion SO heavy that it let only 10 mt to a lander ? Oh boy... :( 
Han shot first and Gwynne Shotwell !

Online envy887

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Re: Lunar Gateway Debate
« Reply #71 on: 07/31/2018 03:31 pm »
Orion/SLS (Block 1B) is supposed to have a 'surplus', co-manifested payload ability of about 10 metric tons. Perhaps the Orion could bring a tanker module with it each time to refuel a reusable Lander? Just an idea...

Hmmm.....  The Apollo LM's total propellant load (ascent and descent stages together) was about 11 tonnes.  An Apollo-style lander today could no doubt get away with less propellant by saving weight and burning, say, lox/methane or maybe even lox/hydrogen rather than NTO/Aerozine 50.  But the dry weight of the LM's ascent stage was less than a quarter that of the descent stage.  If you want a reusable lander, you're going to have to haul something roughly equivalent to the descent stage all the way from the surface back to the staging point, and that means burning a lot more propellant.  That propellant itself needs to be landed on the moon in the first place, so we're talking about a much larger vehicle.

Then there's the fact that, delta-V-wise, LOP-G is about 700 m/s further (one way) from the lunar surface than was the Apollo LM when it began its descent from LLO.

So I don't think Orion/SLS's 10-tonne co-manifested payload capability helps much for fueling a crewed lander.

It's around 5,000 m/s from EML-1 to the surface and back. That means storables need a mass ratio of about 5, methalox about 4, and hydrolox about 3.

So a hydrolox lander would have 10 t of prop, about 1 t of tanks, and 4 t for all other dry mass (assuming everything that goes down also goes up). Since the whole LEM, including both stages, was only ~4300 kg dry, that seems entirely feasible.

A methalox lander would be 10 t of prop, 0.5 t of tanks, and 2.8 t for everything else. The LEM ascent stage was ~2150 kg dry, so that would be tight but perhaps possible.

A storable lander would be 10 t of prop, 0.5 t of tanks, and 2 t for everything else. That's cutting it mighty close, but might be possible with balloon tank construction.

Dang. So much for such a large and powerful rocket as SLS. Is Orion SO heavy that it let only 10 mt to a lander ? Oh boy... :(

That's for SLS Block 1B, which won't be available before 2024. Block 1 can only send Orion with no co-manifested payload, so if you want a lander before then it will need dedicated launches. Falcon Heavy is the only available vehicle that can send much more than 10 t to TLI, it could be used to send tanks of storable propellants to the Gateway.

Offline DreamyPickle

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Re: Lunar Gateway Debate
« Reply #72 on: 07/31/2018 04:24 pm »
The "Gateway as Depot" doesn't sound very convincing. If you want to do ISRU on the moon and produce propellant it why not just keep the fuel on the moon in a permanently shadowed area?

A depot allows smaller intermediate craft but with fuel production on the moon you could build a hydrolox lander sized to go from the Moon's surface to Earth in a single reusable stage.

And even if you want to do refueling in a lunar orbit it would be better to do that away from any habitats for safety reasons.

Offline ncb1397

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Re: Lunar Gateway Debate
« Reply #73 on: 07/31/2018 04:37 pm »

And even if you want to do refueling in a lunar orbit it would be better to do that away from any habitats for safety reasons.

When Soyuz needs to relocate to a different docking port, they undock and fly to the new docking port. You could always use a similar procedure to get a few kilometers out during fueling ops. The contention that humans can't be connected to a fuel tank is just not realistic. Even with an escape system, you need a sizable amount of fuel for that.  Regardless, LOP-G is optionally manned so it can provide both roles as crewed habitat and uncrewed gas station with the added benefit that any required maintenance by crew can be done periodically as it is a crew waypoint.
« Last Edit: 07/31/2018 04:40 pm by ncb1397 »

Offline spacenut

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Re: Lunar Gateway Debate
« Reply #74 on: 07/31/2018 04:41 pm »
A fuel depot would be better at one of the "L" points.  A large "in space only" mother ship or craft could refuel on it's way to Mars.  It could also help refuel either methane or hydrogen from earth with moon LOX for the reusable lander.  Even spacecraft (capsules) that could barely make it to the L point could refuel for a return trip to earth.  This would allow more companies and people to get there. 

BFR could have a 6 person capsule in the nose capable of ejection in an emergency (which NASA likes) and still have 100 tons of cargo that could be delivered to an L point or even a LOP-G point, even if it is 2026 or later, it would be able to deliver more with refueling than SLS with one shot launches. 

With cancellation of SLS and ISS, NASA money could be spent on FH, New Glenn, Vulcan, and other launches to build, supply, and maintain a lunar station. 

Offline Lunadyne

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Re: Lunar Gateway Debate
« Reply #75 on: 07/31/2018 05:47 pm »
Unfortunately, we have to understand a little history to understand where we are now with this whole LOP-G thing.  It boils down to a few main elements:

-NASA Rockets;
-Delta-V and stable Lunar orbits;
-MARS plans

With regards to rockets, the current troubles can be traced back to the early 2000s and Bush's Vision for Spaace Exploration.  It stated that NASA would look to the commercial markets for launch solutions (and have a commercial fly-off in 2008), and not build its own rocket unless it really had to do so based on some exigent requirement.  So NASA figured out that their MARS exploration project needed a 40 metric tonne (mt) capsule to meet its mission requirements.  None of the then EELVs could handle such a payload, as they were targeted to the then market throw-weight of about 20 mt.  NASA later walked that back to 30 mt, but such a massive capsule required a NASA-designed rocket to make it useful.  And so was born ARES (MARS, get it?) and now SLS.

Thing is, at the time, crewed capsules to date had tended to be in the 6-10 mt range, which the EELVs could readily handle (were they "human rated"), and the latest iterations seemed to be in the same mass range.  Why NASA's capsule had to be 3-5x the then market was never really explained other than MARS.  Since NASA's plans were to launch to MARS from LEO, that's where the big rocket they were designing would be delivering its payloads. 

Recall that from LEO you need about 5 mt of mass to put 1 mt of mass on the Lunar surface, or from another perspective, propellant in LEO is going to be 75-80% of the mass package.  Couple this with the oversized mass of Orion, and your payload delivery capabilities Moon-wise are significantly decreased.  Certainly not enough to get Orion to the Moon.  So we go back to the 1960s when the Surveyor probes were being launched and our rockets were still building their throw-weight capabilities, and they could see that the proposed LOP-G orbit could touch an out-of-plane transfer orbit as was studied back in the day to get the Surveyor probes to higher inclination landing sites on the Moon.

The LOP-G NRHO orbit is the result of a lot of work NASA did back during the Asteroid Retrieval Mission days, when they were trying to find stable Lunar orbits that minimized the perturbations from the mascons.  Generally, stay as far away from the Moon as possible (distant retrograde orbit) or spend as little time there as possible (NRHO and other Molniya-type orbits that whip around the Moon and loiter way out (by the way, I don't see how it's a halo orbit if it goes around the Moon)).

So NASA could patch in a solution, basically taking a taxi to the destination from the last stop on the SLS rail line.  A really, really nice taxi.  It could serve as a piece of the MARS architecture, but it's an awkward one, just as it is an awkward solution for the Moon.  But NASA has developed no real strategy regarding the Moon, just a bunch of unrelated tactics, and so is left cobbling together Rube Goldberg solutions to meet Congress' idiot demands.

As other commenters have pointed out, EML-1 is really your best transport nexus solution.  For many reasons:
-It's accessible from all LEO orbital inclinations for about the same delta-V (<4 km/s);
-It's easier to go EML-1 to GEO to EML-1 (<4 km/s) than from LEO to GEO;
-It provides 24/7 access to anywhere on the Moon (<4 km/s);
-It is a clutter-free worksite, as untended items will be perturbed into one or the other gravity wells;
-It's a better place to deploy Solar Sails, away from the weird math of trying to deal with intense Sunlight and intense Earthlight and their constant shifting in relation to one another while the sail deploys.;
-It's an on-ramp to the Inter-Planetary Superhighways, which would allow us to deploy a network of Hubble-like probes around the Solar system for a constant stream of data compared with our current decadal megamissions to one destination or another.
-In conjunction with EML-3 it is a good place to keep an eye on cis-GEO activity;
-You can also go asteroid hunting there.  Picture a lighthouse lain on the line connecting the center-of-mass of the Earth and Moon.  The rotation of the lamp represents the sweeping of the sky by the probe.  Over the course of a month, it will be able to develop a really nice data set of nearby objects, especially the Sunward blindsiders that keep surprising us.
-With propellant depot capabilities in LEO, at EML-1, and on the Moon, you can go to/from anywhere in cislunar space, or at least get to a gas station, for <4 km/s, providing a nice propulsion envelope for engineers to work with.  What's likely going to happen is that given the approximately 80% propellant mass in LEO requirement noted above, and that LOX/LH is approximately 7/8ths LOX by mass, then Lunar oxygen is going to be finding its way to LEO pretty quickly, and you'll see dedicated launches of LH from Earth just-in-time for needs in LEO, and points beyond.

The list goes on...

So here's what's going to happen.  This is all strurm und drang, signifying nothing.  Trump's Moon pivot is unstrategic, and serves mainly for drama.  NASA, besotted with MARS!, was caught off guard and is scrambling.  When the presidency changes, NASA will immediately try to pivot back to MARS, and will discard the LOP-G faster than yesterday's fish.  Given the current glacial pace of progress at NASA, this change of administration will occur before any real work beyond PDR will have been done on LOP-G, so any sunk costs shouldn't incur too much in sunk costs.  NASA will again revisit their MARS architecture again, and Bob Zubrin will again publish a more directly MARS version. 

Maybe I'm just cynical and jaded because I've seen too much, but NASA has effectively become a force for stasis, not a force for change.  If they could, they'd still be launching the STS today.  The only real hope is for a substantial rejuvenation at NASA, where those who haven't been able to get anything done (for decades...) finally cede the way for others to give it a go.  There is a fine young generation of space leaders out there, worthy of a shot at making things happen, and the way things are are not the way things must be.  (Except for the physics part) 

What's really weird is that the situation we find ourselves in now, where nigh 50 years after we put people on the Moon we can't put people in orbit, the result of politics and friends working tax-dollar cash flows to their friends and working on projects that will always be finished "Real Soon Now", isn't too different from the result that, say, a nation like China might desire and work towards, that of a country so mired in stasis that its people can't even get to cislunar space while it itself puts assets in cislunar space and on the Moon, delivers crews to orbit, and has probes move from destination to destination in cislunar space.  Like something out of a bad spy novel, but actually happening in real life.  Or bad sci-fi, where the same thing keeps getting done over and over and the time loop keeps repeating the same lack of results.

So I'm having a hard time getting excited about the LOP-G, just like SLS.  They strike me as more like the current crop of STEM stuff in education, craft/make-busy projects with a thin veneer of science/engineering thrown on for legitimacy, rather than real exercises in making progress.  We have the tools at hand to make real progress in spreading human activity into cislunar space and out to translunar space throughout the Solar system.  We're just not using them right.  We could be, but we're not.

Offline ncb1397

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Re: Lunar Gateway Debate
« Reply #76 on: 07/31/2018 06:29 pm »
Quote
Thing is, at the time, crewed capsules to date had tended to be in the 6-10 mt range

???

Mercury -1,360 kg
Gemini - 3,851 kg
Apollo - 28,801 kg

Actually, none of them were in the 6-10 mt range.

edit: I guess we are looking at foreign sources

Soyuz - 7,150 kg
Shenzhou - 7,840 kg
« Last Edit: 07/31/2018 06:37 pm by ncb1397 »

Offline spacenut

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Re: Lunar Gateway Debate
« Reply #77 on: 07/31/2018 07:44 pm »
How much does Dragon 2 weigh?  Isn't it in the 10 mt range? 

Offline Lunadyne

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Re: Lunar Gateway Debate
« Reply #78 on: 08/01/2018 01:25 am »
Actually, I was thinking more along the lines of:

Apollo CM: 5.8 Mt
X-38 CRV: 8.2 Mt
Soyuz TMA: 7.2 Mt
Shenzhou: 7.8 Mt
Dragon: 8 Mt
Dreamchaser: 9 Mt
CST-100: 13 Mt

Various CEV concepts were also in this range; couldn't find a value for the New Glenn capsule. 

All values taken from Encyclopedia Astronautica.

Offline ncb1397

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Re: Lunar Gateway Debate
« Reply #79 on: 08/01/2018 06:38 am »

Apollo CM: 5.8 Mt
X-38 CRV: 8.2 Mt
Soyuz TMA: 7.2 Mt
Shenzhou: 7.8 Mt
Dragon: 8 Mt
Dreamchaser: 9 Mt
CST-100: 13 Mt


Well, if you aren't counting the service module for Apollo, you might as well add Orion at ~10.3 Mt. But your list mixes numbers with service module included and numbers without service module included.
« Last Edit: 08/01/2018 06:39 am by ncb1397 »

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