Representatives from SpaceX, Blue Origin, and United Launch Alliance participated in a forum last week held by NASA to determine the future of humans on the moon. This isn’t just how they will live, how long they will stay, or what they will do; no, this is far more interesting: this was how humans will travel from lunar orbit from the surface of the moon. The future of the next generation of lunar lander is being determined right now.
The plan right now is entirely unlike Apollo, which sent a pair of spaceships in orbit around the moon, sent one to the surface, then returned to the mother ship for the trip back to Earth. Instead of something somewhat simple, the next era of lunar exploration will happen from a gateway orbiting in cis-lunar space. What makes this so amazing is how weird the orbit is, and the reasons behind it.
It’s The Orbit That’s Special
By now, most of us should know how the Apollo missions went. The Saturn V took off from the cape, went around the Earth for an orbit or so, and then re-lit its engine to send it off to the moon. After a three-day journey, the Apollo command module entered a nearly equatorial orbit, sent the lunar lander on its way, waited a day or two or three, docked, and then sped back to Earth. The equator is the easiest place to land on the moon, and the first three Apollo missions to do so — Apollo 11, 12, and 14 — all landed within a few degrees of the lunar equator. Later missions ventured farther north, but only so far: Apollo 15 landed at 26° North latitude. Sure, we’ve explored the moon, but it’s like saying you’ve explored the Earth if you’ve only been as far North as Florida. There’s interesting stuff in more temperate climes, and on the moon especially so: there is water ice underneath craters on the lunar poles.
Part of this was due to the technology at the time. Apollo could, theoretically, land at the poles. It could also land on the equator. Mid-latitudes were challenging; to get to these latitudes, the command module would have to orbit at an inclination that’s equally far away from 0 as it is from 90. Sure, you could take an Apollo lunar lander down to the moon at 45° North, with the Earth low on the horizon, but to get back, you’d have to rendezvous with the command module. That too could happen, but then you’d be stuck. Apollo simply wasn’t built for landing at mid-latitudes with the Earth low on the horizon.
Sure, it’s rocket science, but so is playing Kerbal Space Program. With Kerbal space center on the equator, and the Mun in a zero degree inclination orbit, you don’t need to think too hard about getting to the Mun. If you want to go to latitudes other than the Armstrong memorial or the munar arch just north of East crater, it takes a bit more work.
Note the same also applies to past, potential landing sites of Apollo missions. When Harrison Schmitt suggested landing on the far side of the moon using a relay satellite to send transmissions around several thousand miles of rock, he suggested landing near the equator. It never happened, but the possible landing sites of the Apollo missions was based on the capabilities of the Apollo spacecraft.
A New Orbit, And A Gateway
NASA’s new plan for future trips to the moon don’t go directly to the moon. Instead, future moonwalkers will first visit a ‘lunar gateway’ in a Near-Rectilinear Halo Orbit. What’s a Near-Rectilinear Halo Orbit (NRHO)? That’s takes a little bit to unpack, but the benefits are worth it.
There are stable co-orbits in any three body system, and already there are a hundreds of objects in the solar system in such a configuration. As a thought experiment, imagine yourself on the surface of the sun. Directly above you, about five AU away, is Jupiter. If you were to draw an equilateral triangle with legs five AU long, you’d find a group of asteroids trailing and leading Jupiter. These are the Trojan asteroids, and thanks to Jupiter’s enormous mass, these asteroids are in an extremely stable orbit. They’re also orbiting a Lagrange point, in this case L4 (orbiting before Jupiter) and L5 (after Jupiter). There are three more points that are stable in any orbit, but the important ones are L1 and L2. In the Sun-Earth system, these points are for solar monitoring satellites, and eventually the James Webb Space telescope will be hanging around Earth-Sun L2, or in Earth’s shadow, about a million miles away.
While there is a mathematical reality of Lagrange points, in practice it’s much easier to orbit these points. That’s exactly what the lunar gateway will do. The Near-Rectilinear Halo Orbit is a special case of the Earth-Moon L2 orbit that at first appears to be a strange polar orbit of the moon, with one orbit taking between 6 and 8 days.
From a simplistic point of view, the NRHO looks like a highly eccentric polar orbit around the moon, with a periapsis of about 2,000 miles, and an apoapsis of about ten times that. This orbit isn’t a lunar orbit, though. Mathematically, it’s still an orbit around the Earth-Moon L2 point. It takes a bit more energy to get to than a lunar orbit, but it provides some fantastic benefits. It’s easy to access with launch vehicles either currently flying, or in testing, it’s in a favorable location for Earth, sun, and deep-space observations and communicating with Earth, and NRHO orbits can be used as relay stations for operations on the moon’s far side.
Since this is an orbit around Earth-Moon L2, it is inherently unstable, and will require a bit of fuel to maintain the orbit. That’s a problem, but as the Apollo science packages found, nearly all orbits around the moon are unstable and would require fuel to maintain orbit.
Soon, there will be a space station orbiting somewhere around the moon. It’s not actually in lunar orbit, although if you looked at it long enough it might seem like it. This is the orbit that will be the first stopping point on the way to the moon, and unlike the Apollo missions, this lunar gateway will be able to take us anywhere, whether it’s to the water ice trapped under the poles, to the far side of the moon, or to revisit the historic landmarks of the Apollo and Surveyor landing sites.
Tempted to fire up Universe Sandbox² and simulate that.
Checked with the US² guys and due to certain limitations, no it can’t. Now Kerbal Space Program unmodified can’t, but possibly with a mod (change the physics engine) it can.
“…travel from lunar orbit from the surface of the moon …”?
Apparently the engine on the “to” rocket failed to ignite.
Those are made by the lowest bidder and that sometimes happens. It is part of the acceptable risk.
what does bidding have to do with this article
Here is another take on the Gateway:
https://arstechnica.com/science/2018/09/nasa-says-its-building-a-gateway-to-the-moon-critics-say-its-just-a-gate/
I feel the salient point is buried way down in the article. The choice of orbit and hardware stem from the conclusion at NASA and the government that need to have the SLS have a purpose:
“But the original Gateway concept was conceived to give SLS and Orion a mission, not develop technologies we need for Moon or Mars exploration. The current concept of operations for Gateway will make getting to the lunar surface more expensive without furthering critical exploration technologies, all while consuming the vast majority of the human exploration budget.”
“The choice of orbit and hardware stem from the conclusion at NASA and the government that need to have the SLS have a purpose:”
That’s really not the right way to think about it. Orion/SLS had been in development for a long time. So now you’re in the situation of “given that Orion/SLS exist, what can we do with them?” Orion/SLS aren’t ideal moon transport vehicles, since once in-flight, they don’t have a lot of delta-V. So how do you leverage that to do low-cost stuff at the moon? You have a permanent station that has low delta-V transitions between an Orion/SLS orbit and a lunar orbit.
The criticisms of the Gateway really are misunderstanding the current political realities. You’ve got an executive branch in the US that tries to entirely change direction every few years. Would it be smarter to have a cohesive, multidecade plan for space exploration? Duh. Good luck fixing that problem. You deal with the reality that you have.
Also the idea that the Gateway will actually make it more expensive aren’t really correct – they’re missing the reality that individual rocket flights themselves are becoming significantly cheaper, so the idea of sending everything in one giant launch is probably outdated. If you send everything in one launch, going through Gateway’s more expensive. If you send things in multiple launches with only the crew needing to go fast, the delta-V becomes identical because transitioning to the halo orbit from a ballistic transfer is essentially free, just slow. And it becomes *way* cheaper long term if you keep a stage at Gateway that can be reused.
It’s really not a terrible plan. Its biggest problem is that it’s essentially acknowledging political and logistical realities, which always leave you with compromises that look goofy.
Covered pretty well.
https://space.stackexchange.com/questions/23992/why-is-a-near-rectilinear-halo-orbit-proposed-for-lop-g-formerly-known-as-deep/24018
“So now you’re in the situation of ‘given that Orion/SLS exist, what can we do with them?'”
Except that the question isn’t “What can we do with Orion/SLS?” but “What can we do with Orion/SLS that can’t be done with Falcon Heavy or other commercial rockets because having alternatives would make the spectacular waste of SLS obvious and derail Richard Shelby’s pork train?”
The foundational objective of this mission architecture is to prevent launch from getting cheaper. The actual mission is to funnel tens of billions of dollars to specific companies in specific districts, and buying launch services on the open market for a tenth the cost doesn’t achieve that. So Congress (with Boeing/NGIS/Lockheed doing the math) engineered spacecraft and a flight profile that can only fit on SLS to make sure that the decreasing cost of every other rocket doesn’t threaten the real mission.
“Except that the question isn’t “What can we do with Orion/SLS?” but “What can we do with Orion/SLS that can’t be done with Falcon Heavy or other commercial rockets because having alternatives would make the spectacular waste of SLS obvious and derail Richard Shelby’s pork train?””
This actually *minimizes* the use of Orion/SLS. Buildup to a crewed return to the Moon (with a demonstration flight) would require 3 Orion/SLS launches, and *6* commercial launches. And once that’s complete, if you have a crew-capable spacecraft and launch vehicle that can reach the halo orbit (which is *less* than reaching the Moon) you don’t need SLS anymore, and the whole thing can be done with commercial rockets, and cheaper than a direct-to-Moon mission.
If they wanted to keep Orion/SLS forever, they would’ve just found a way to argue for the 2-component lander module, because only the SLS could do that. They didn’t. The whole setup actually creates the infrastructure needed to get you to virtually *anywhere* on the Moon’s surface using commercial rockets.
Yes, of course, you’re trying to find a use for SLS. Duh. Welcome to politics. But the entire setup is actually a really reasonable compromise if you consider the political reality. I really don’t understand the vitriol against it, other than the fact that people hate the SLS (and don’t get me wrong, I’m not a fan either!). Once you accept that immediately getting rid of the SLS isn’t politically feasible, having a space station in orbit of a Lagrange point is pretty damn awesome. Lagrange-halo space stations have been talked about for almost 20 years. They’re fantastic. I mean, you can literally think about CubeSats to practically anyplace in the Solar System for less than 50 m/s, piggybacking on supply rockets.
“They’re fantastic. I mean, you can literally think about CubeSats to practically anyplace in the Solar System for less than 50 m/s, piggybacking on supply rockets.”
This ad brought to you by AmazonSpace, for all your shipping needs. :-D
The problem is it cost $25.4 billion to put the first man on the moon and school kids were saving their money to give to NASA. How many years did it take to originally get there?
Then we had Skylab that NASA let burn up on re-entry instead of saving.
Then we had the Space Shuttle and a host of plans with it that never came into fruition and now we don’t have any more Space Shuttles.
Then NASA is doing other projects like Hubble and other space probes that went to MARS and other regions of space.
The problem is any expensive plan is subject to the fiscal realities on earth and budget cuts and dependent upon who is in charge or who is in office at the time so your long term plans change like the wind. Unless man finds resources on the moon, there is little economic benefit from going there other than the inventions that you make along the way.
Unless there is an economic or military benefit from going there, it will not necessarily be sustainable.
It is not astronauts can go to the local supermarket, department store or hardware store for supplies. And you will have to haul habitable structures to the moon to survive. You still have to deal with radiation, meteorites and severe temperatures to survive.
And it can all be cancelled by another congress because it is 50 years later and no one has stayed the course which keeps changing.
“The problem is any expensive plan is subject to the fiscal realities on earth and budget cuts and dependent upon who is in charge or who is in office at the time so your long term plans change like the wind.”
Yes. Exactly. Which is why this *isn’t a bad plan*. Why isn’t this clear? SLS/Orion aren’t going away, they’ve got too much political pull. That money’s just gone. And administrations have flipped back and forth between the Moon and Mars now so many times that NASA’s got to be dizzy.
Gateway can be sold to an administration that wants to see NASA get to Mars, and it can be sold to an administration that wants to see NASA get to the Moon, and it can be sold to an administration that wants to see space commercialized, and it can be sold to the people who want SLS/Orion funded. Is it the *best* plan for any option? No, of course not! But it’s not a “useless” option, and it’s absolutely not a “toll road” like Zubrin is claiming. It’s an option that uses SLS for as short a time as possible, long enough for the fatcats to say “how bout that Orion, huh?”, and then it leaves something *useful* in its wake.
It’s politics. It’s not worth dreaming about what might’ve been and asking where your rocket cars are. You do the best with what you’ve got.
I used to think ‘clickbait’ was a clickbait word. But once I realized clickbait was just something you didn’t like, the word ‘clickbait’ wasn’t clickbait at all.
‘clickbait’ is compositionally understood: you need a context. There is nothing ‘weird’ about the orbit. It fully obeys the physics of orbital mechanics.
But calling it a “weird orbit” will get you lots more clicks if it appears in Google News; and ‘weird orbit’ is novel enough to tickle Google/Alphabet’s algorithm fancy.
Once Brian catches you with his “bait”, I think you should be released into a separate pond. So you can no longer defecate where the rest of us play.
Thank you. Akismet may look into your use of the second person pronoun + ‘defecate’ implicature.
“Weird” as some use it is shorthand for “non-traditional” or “non-standard” and if the link Ben brought up is the case then it’s “weird” from the “this is what we’d do if it was us doing science, or furthering human progress”. Not that bringing home the pork isn’t weird or anything.
” There is nothing ‘weird’ about the orbit. It fully obeys the physics of orbital mechanics.”
It’s weird because it’s a 3-body orbit, and it’s a *very* 3-body orbit. Most people are used to seeing flat, 2D orbits. This is literally an orbit that you have to see in 3D, because it’s not flat at all. It’s hard to imagine how an orbit like that can always have line-of-sight to Earth, but it always does.
Looks like China is putting some pressure.
Lets spend xBillion again for yet another pointless thing to do. While our blue planet rots away with no renewable energy lets spend money we don’t have on playing in the sandbox on some other rock which has nothing to offer to fix things here.
No renewable energy? You might want to look around.
I don’t mind spending xBillions in exploration. It beats stagnation and it forces new technology to meet the challenge which can benefit us here on Earth. I am all in. It is much better than inventing new ways of killing each other…
As for renewable energy … when it can compete with standard oil/gas/coal/nuclear on its own (no government subsidies) then go for it… As long as there are standard steady sources of energy available to back it up. People don’t seem to realize that you can’t rely on Wind/Solar. Plus you do know it takes ‘energy’ out of the air and of course solar takes the rays from from the sun which would normally be reflected/absorbed by the Earth below the panels? …. Talk about possible climate change if you get enough of this technology going…. Not to mention the eye-sores of large solar farms and wind mills all over…. Anyway, A couple of the coldest couple of days of the year up here and there was 0 wind and 0 solar across the state of MT (I work in a utility). If that was all we had we would be all be in the dark at the worst time. Thank goodness for the hydro/coal/gas facilities that keep our lights on and keep the system stable.
“when it can compete with standard oil/gas/coal/nuclear on its own (no government subsidies) then go for it”
You need to rid yourself of the delusion that oil/gas/coal/nuclear receive no government subsidies.
Fossil fuels have a huge subsidy in that they don’t have to pay for the damage they do to the environment. So let’s eliminate that with a carbon tax and see how things work out…
My foot went right though the crust and into the mantle on the way to the lab today!
You’re the kind of person who would piss out a caveman’s fire.
He3 would like to have a word with you.
That’s what I was going to say. The benefits of going to the moon FAR outweigh the costs, just for the Helium 3 alone. Here’s a 15 year old article that explains how He3 could power the world. https://www.popularmechanics.com/space/moon-mars/a235/1283056/
He3 fusion is much more difficult than D-T fusion. I suggest to first master this one. Then we can go further.
The planet does not rot away. That’s only what some kind of people want to believe us. At least in western countries traditional religions loose importance, so they need new methods of inducing feelings of eternal guilt in the population. The climate alarmists and greenis do come just right for this purpose.
“Rots away” What planet are you living on? The earth is in much better condition pollution wise than it was in the 1960’s. I will also add that many, many wonderful innovations were produced as offshoots from the first manned lunar mission that are still benefiting society to this day so we might see real advances in fuel cell technology as well as solar and who knows what else once this program is operational.
““Rots away” What planet are you living on?”
One built by the lowest bidder. :-D
Touche.
There’s plenty of billions spent on stupider things. And it’s not like, if NASA were suddenly disbanded, it’s budget (actually not a great amount of the US government’s budget altogether) would be spent on improving the environment or ending homelessness. It’d just end up in some other companies’ pockets, something other than aerospace.
What with corporate welfare and subsidies and lobbying and the like, the US government’s budget is fucked anyway. And of course the same appplies to many other countries. Space missions advance humanity’s knowledge, and our imagination’s appetite for, eventually, getting off the planet. It might be possible to travel to the stars and meet aliens, one day. Not necessarily possible with what we have now, but keep up the research and maybe one day.
I wouldn’t say that NASA IS building anything until there is hardware in the sky. Maybe not even then *cough skylab *cough.
I’m sure if I had all my childhood stuff I could find you a magazine article with an interview of someone at NASA stating that we would have boots on Mars by the then future date of 1990!
Older readers could probably come up with even earlier dates I’m sure.
They very well may have the best of intentions but when it comes time to actually pay for these projects they always hit a WALL when our representatives and the dummies that elect them direct all our money at worthless BS instead.
“They very well may have the best of intentions but when it comes time to actually pay for these projects they always hit a WALL when our representatives and the dummies that elect them direct all our money at worthless BS instead.”
Isn’t that the point of the privatization of space? Where the common man can kickstart their way to space, instead of “dummies” investing in “worthless BS”?
That’s actually part of the reason for these orbits as well. With existing/planned rockets, you basically need 3 launches to deliver significant cargo to the moon: otherwise the lander is too heavy . And since you only need to get to the moon quickly with 1 stage (the one carrying people) if you’re doing 2 “slow” stages, you want the lunar orbit that you assemble everything together at to be as cheap as possible to get to from Earth – and an L2 halo orbit is essentially as cheap as you can get.
It’s not crazy to think that having the ability to just buy the rocket capability to transport humans to the Moon could be pretty transformative.
Government should’ve gotten out of the way in space in the late 70’s instead of monopolizing launch capability. If it had retreated to R&D, and having satellites built for public and military use while leaving launches and everything else to private industry while regulating where satellites get to be put in orbit (traffic control) we’d have outer space today looking much like SciFi authors of the 60’s depicted it would be like in the early 21st Century.
What made government’s stranglehold on space stuff especially awful was how little they’d begrudge to spend on it. Government space programs in the USA have always been a low % of the American federal budget. they were cutting NASA’s budget halfway through the Gemini program, forcing cutbacks to Apollo, which reduced the number of Moon landings, eliminated any possibility of a Moonbase and made Skylab a three use throwaway then literally cut holes through the second flight capable Skylab so it couldn’t be used.
Please. Please go away.
As others have mentioned, SLS and Lunar Gateway aren’t the best way to get to the moon or the way that will most likely actually be used to get people there again. Note that a privately-run (with government funding) unmanned mission launched by a privately-built rocket is currently approaching the Moon.
I was surprised to learn that the Saturn V orbited the Earth then left for the moon.
It’s standard procedure for any space vehicle leaving Earth orbit. To get on the right ballistic trajectory to get it to where you want to go, the vehicle must be launched into orbit around Earth far enough ahead of its departure time so it can be checked out before the orbital positions of Earth and the destination are just right.
Ideally the launch should be timed so that the vehicle’s orbit around Earth will have it precisely in position to fire its engine to depart so that no further course correction is needed. That can be adjusted after launch by raising or lowering the Earth orbit to change the orbit period. Or the vehicle can be designed with extra fuel so that it can depart ‘close enough’ then one or more corrections along the way can put the end of the trajectory where it’s desired.
For going to the Moon it’s not as critical. The Moon’s always *right there*, not altering its distance or inclination of orbit too quickly (it has an 18 year cycle) so a Moon ship can launch into orbit around Earth then leave for the Moon at pretty much any time it’s at the ideal point in Earth orbit. Miss the window and just wait 90 minutes (or so, depending on altitude) with minor adjustments to trajectory and burn calculations. If a problem crops up and your unmanned Moon craft is delayed in orbit a day, a week, or more, no biggie, the Moon isn’t going anywhere except some farther around its orbit. It won’t become impossible to get there due to not having enough fuel or time.
If you’re flinging a ship to Mars, the changes can be more involved if the departure window is missed. Delay too long and the flight has to be scrubbed because the vehicle won’t have enough fuel or it would take too long to get there.
I’m pretty sure he means that the Saturn V itself, meaning the “launch vehicle”, never orbited the earth or went to the moon. The command module, the service module, and the lunar excursion module, which all combined made up the Apollo spacecraft, did however do both. Once the 3rd stage was jettisoned, the Saturn V ceased to exist.
The third stage of the Saturn V actually did make it into earth orbit, was re-lit for the trans-lunar injection burn, and ultimately crashed into the Lunar surface after being jettisoned.
https://www.space.com/31503-apollo-16-moon-rocket-crash-site-photo.html
Is it not possible to setup an orbit that travels around both earth and the moon, maybe something like a figure-8?
not really…a simple “figure 8” has no way of lasting beyond 1 orbit, you’d be flung into the Moon or into Earth (or into a higher Earth orbit)…
And btw if you look at the NRHO, it kinda’ is a figure 8, just bent in 3D space ;-)
Mostly true – as in, a simple figure 8 can’t be periodic due to the relative masses of the Earth and Moon and distance. But you wouldn’t be flung into the Moon or Earth or anything. A figure 8 (free return trajectory) isn’t periodic because the Moon moves. So after you get back to the Earth, the Moon isn’t there to swing around, and you just end up in a highly elliptical low-Earth orbit. To make it periodic you need an orbit which is the same length as the Moon’s orbital period (or a multiple of it). If you cheat a little and add a loop-de-loop in front (prograde of) the Moon, you can actually make the orbit periodic. It’s still *mostly* a figure 8. There are 3-body situations where a simple figure 8 can be periodic, though – just not the Earth-Moon system.
Yes, but it’s not as simple a figure 8. It’s called a cycler orbit and was originally proposed by Buzz Aldrin.
https://en.wikipedia.org/wiki/Lunar_cycler
Technical issues aside, how much money does NASA want for this to spend on planing and then not send anything there? Every now and then there are cool stories stemming from NASA PR department about various fancy stuff only to keep the public going on paying their salaries.
If the government didn’t change course randomly every 4 years, maybe NASA would be able to achieve something more.
Chinese didn’t build their Great wall in 4 years.
I want to try building this in KSP with realism overhaul.
Though I’ll probably use the Nova rocket or BFR.
Building a space gateway to the moon? Sure, go for it!
Building a rail gateway to New York? Nah, too expensive.
Our government at work.
Putting money into the hands of New York politicians?
That would be a waste of million$, if not billion$…
Why not a continuous orbit tracing something like a figure 8 around Earth and Moon? When close to Earth it could be loaded up with payload/people or repaired. Same when in vicinity of Moon. Trips to and from stations would be shorter at both ends and Earth-Moon transit for passengers would be more comfortable. Astronomy science benefits might be lessened due to less continuous time in deep space. In time maybe have two or more could be put in place …
My only thought on that is that you would need to change acceleration while whipping around Earth – there would have to be fuel usage figured into the “daily operations” of the station. I tried setting the original orbit up in Kerbal last night and could make it easily enough, but anything with enough mass to enter the stable elliptical orbit around Mun took an astronomical amount of fuel to put together in Kerbin orbit and then move into the correct orbit around Mun. Once I had it in the stable orbit, the act of docking and undocking (adding and subtracting mass, not bumping into it) did cause the orbit to waver slightly so I was having to correct every few Munar orbits…
It was fun to do and could have a bit of real-world potential – hitching a ride to get to the Moon would let the tourist and science missions use less resources in transit, but would definitely be a huge resource hog in the beginning.
That’s my 2 cents.
Thanks for that!
Actually, you don’t, which is kindof insane. The “figure 8 orbit” you’re thinking of is a free-return trajectory – where you burn such that you’ll whip around the Moon and then come right back to Earth.
But normally that orbit only works *once* – because by the time you’re back at Earth, the Moon has moved, and now your orbit (which would obviously normally repeat completely) won’t work because the Moon’s not in the same place.
But if you tweak the orbit a bit so that the total orbit length is equal to the time it takes the Moon to go around the Earth, it’s a periodic orbit. You end up having to do a loop-de-loop out by the moon to extend the orbit period, but it works (as in, you head out to the moon before the moon gets there, start falling back to Earth, get picked up by the Moon as it comes by and turned back around to the Earth again).
I had noticed something similar to that while futzing with the orbit just around Mun – there is really no mechanism that keeps the Munar orbit Ap always facing Kerbin (I am sure that this is due to my limited knowledge of rocket science). I will work on the periodic orbit and aim for one orbital period of Mun around Kerbin – I imagine that my Pe around Kerbin would be at around 300 or 350KM and then my Pe around Mun would be 180 or 200KM (after returning from Mun for the first time)… Sounds like something fun to learn!
Stock KSP is limited with wacko 3-body orbits because they don’t do N-body physics. To be honest, I don’t know if the periodic free-return trajectory is possible or not. It obviously won’t be the “correct” periodic free-return, but you might be able to do a “Kerbal free return.” My instinct is that you can’t, but I could be wrong.
If you really want to do screwy orbits you definitely need one of the mods that does N-body physics (e.g. Principia).
The concept of a lunar gateway spacestation is fine, if and only if, you also have asteroid capture. But unfortunately NASA decided not to fund the actually useful version of the ARM program to capture asteroids that would allow for de-spinning of them. Instead they funded the minimal version that has no de-spin. This means that literally only ~4 asteroids would be available for capture and processing at such a base. It makes it entirely useless. Lunar resources would not be easily available due to the complex and expensive gravity well entries and EDL without atmosphere requiring entirely propulsive means.
No, the lunar gateway is just another stupid jobs problem now.
Who cares about needing propulsion to get down to the surface? Are you planning on sending missions without a rocket engine?
The only downside to the higher delta-V to get to the Moon is that you need more fuel. But that doesn’t matter if you have a refueling depot, which this is. And if you have a refueling depot, you want it in an orbit you can get to as cheap as possible, which this is: it just costs you the delta-V to get to LEO and TLI, and that’s basically it.
Plus, one of the main innovations in rocket engines in the past 10 years has been extremely high reusability: we now have pretty high confidence that we can build rocket engines which can operate for many hours. Which means not only is the fuel for the extra delta-V at the depot, so is the engine that gets you there, too. The idea that it’s useless is completely crazy.
The thing we really need SLS for, is to launch a complete “tug” to get launches from LEO, to HEO, GEO, and/or a refueling station. SLS has a large enough diameter to lift complete ships, and docking rings that have many connectors.
I am a totally “moon first” guy, because we need to learn how to deal with abrasive dust, temp swings, habitats, food and water cycling, and ground transport before we have a good shot at keeping folks alive at Mars. We also need to learn ISRU, and by learning seperation tech for minerals, we can do mine waste clean-up, and asteroid seperation tech at same time. We also need to work on power supply tech, and it is looking like Helion fusion tech is much simpler than anything else out there. Better thermoelectric conversion is high on the list too.
http://www.helionenergy.com/?page_id=199
And the moon is covered with solid rocket fuel, all you have to do is pack the sifted regolith into a cylinder with a rocket nozzle at one end, and ignite it. There are experiments now at the collegiate level, that are packing aluminum, iron, and ice into solid fuel rockets, and they work fine. So you can get off the moon pretty cheap and easy.
There’s interesting stuff in more temperate climes, and on the moon especially so: there is water ice underneath craters on the lunar poles.