SpaceX Ultra Heavy Starship Version 2 Could Launch Satellite Version of Project Orion

Last year, Elon Musk tweeted that Starship Version 2.0 will be 18 meters in diameter instead of 9 meters. Nextbigfuture wrote about this conceptual plan last year. The upgraded for the Ultra Heavy Starship 2.0 might be able to launch over 1000 tons per launch.

The smallest project Orion design was about 17 meters in diameter and weighed 300 tons. This was called satellite Orion.

This means a Ultra Heavy Starship version 2 would have the payload diameter and cargo capacity to launch a complete satellite Orion. The parts for 4000 ton interplanetary Orion could be placed into Orbit with about four launches.

The massive payload of a future generation 2 SpaceX Ultra Heavy Starship could also launch factories and advanced production systems to the moon. Creating the production systems for nuclear pulse propulsion on the moon would remove concerns about nuclear radiation from a ground launched Project Orion. Creating nuclear pulse propulsion capability would enable manned interplanetary, manned gravitational lens range missions and manned interstellar missions.

Orion leaving Earth orbit, bound for Mars. Artwork credit and ©: Adrian Mann.

Freeman Dyson considered an alternative momentum limited pusher plate design where an ablation coating of the exposed surface is substituted to get rid of the excess heat. The limitation is then set by the capacity of shock absorbers to transfer momentum from the impulsively accelerated pusher plate to the smoothly accelerated vehicle. Dyson calculated that the properties of available materials limited the velocity transferred by each explosion to ~30 meters per second independent of the size and nature of the explosion. If the vehicle is to be accelerated at 1 Earth gravity (9.81 m/s2) with this velocity transfer, then the pulse rate is one explosion every three seconds.

Modern improved materials might be able to increase the upper range of the momentum limited pusher plate design of a nuclear pulse propulsion Orion. The top cruise velocity that can theoretically be achieved are a few percent of the speed of light (0.08–0.1c).

SOURCES – Wikipedia, SpaceX
Written By Brian Wang,

78 thoughts on “SpaceX Ultra Heavy Starship Version 2 Could Launch Satellite Version of Project Orion”

  1. China and Russia don't have an Elon Musk.
    You would need Starship 2.0 to get an Orion built in orbit.

    I'm assuming you'd want an extra Starship to tow it away from Earth a bit before you start setting off those nukes.

    I'm still not too hyped about using Orion to go to other stars. If it's going 0.1c that's still 40 years to go 4 ly away. By then we might have something faster. That's right on the verge of being useless. What might be useful though would be to see how electronics and other important things hold up at relativistic speeds. What if matter decomposes at 0.05c? We're pretty sure it decomposes at 1c but where's the cutoff? That's something we'd need to know before sending people anywhere.

  2. Thanx for the thinking, *we* overall have clearly not figured out what to do yet, certainly not in detail. Other than the Orion use, you are largely describing bigger version of the current NASA plan, after Mr. B jumped at the chance to return to the Moon only a few years ago. Whew! It also reminds me of plan to use one regular thermal nuke rocket to go to lunar poles and ferry water to build orbital ice habs.

    Now, there is a trap in thinking that big rockets are *the* solution to Space infrastructure. They are certainly helpful, but ISM/ISRU are the solution, period. This should/could have been started upon O'Neill publication, if big ideas were not so slow. Just think of how quickly Earth resources would be exhausted if we had to launch what we need in Space to Space. Even with free huge rockets. The task is independent of the rocket size, don't wait!

    Curiously, there was a similar situation with *water on the Moon*. This has been touted as a game changer, and clearly is, but it is like big rockets, not relevant to the overall decision of whether to wait. Before lunar water was considered even possible, the plan was to get O, glass and metal slag from equatorial lunar rego. O is most of water mass, etc. The biggie may be the C so Musk can use it! And, we need to put Earth sea water in O'Neill Settlements so the level goes down to ice age levels after the ice melts under normal long term cycle.

  3. It's got a half-life of 79 SECONDS. If you had 10g of Americium 232 in one place it would be a glowing plasma it would be so hot from decay heat! But how would you accumulate that much when half of it was decaying away in a little over a minute?

    Even the Pu 239 has a high enough activity that the bomb "pits" are, I've heard, noticeably warm. And that's, what, a 24,000 year half life?

    That's what I meant when I said that low critical mass isotopes tend to be very "hot". That renders them totally unusable for this sort of purpose, they can't be stored in significant amounts, or assembled into bomb pits, and typically if you could somehow do so you'd get a squib reaction because the underlying reaction rate is so high you'd blow the bomb apart before the critical mass was fully assembled.

    Anything with a half life of under a thousand years is probably unusable for bomb purposes because the bomb would melt in storage from decay heat.

    Of the isotopes that are actually usable for this purpose, Pu 239 is probably the best.

  4. Yeah, I know. Even gen1 of Starship makes the idea of an Earth launched Project Orion obsolete. Around the turn of the century, I played around with the idea of using Project Orion to give us more or less instant infrastructure for the Solar System. Use a launch to put a LEO space station, one around the Moon and landing much of a lunar mining facility all in one shot. Complete with LEO to lunar tugs and lunar surface to orbit craft. Not to mention a collection of modular nuclear power generators safed and ready to go when needed. All that would be lacking would be ground to orbit on the Earth side. It would solve the problem of what kind of payload that would use the capacity of a 4k ton Project Orion. Because of the EMP and Van Allen problem, you could only do it once or twice, but…

    Two things are different. One is Starship. That obviates the need for extremely large payloads. Reusability and orbital refueling drastically changes the equations. The second was confirming volatiles on the Moon. Suddenly refueling in space becomes a lot easier when it could be sourced from the Moon. Not to mention, O'Neil-type habitats make better sense when you don't have to lift all of that atmosphere, lakes and what not from Earth. Water as radiation shielding is a lot more practical.

    However, the sight of a 4k ton Project Orion lighting off just beyond the Karman line would be a sight to behold…

  5. No problem in scaling down the power of a nuclear
    device, they also made 10T. They didn't go lower
    because you don't pay millions to get a dirty mortar

  6. My vision is tens of thousand nukes the size of a soft-ball and the cost of less than a hundred thousand each. I am not sure this world would be ready for that.

  7. > But we don't have a hope of detecting even a boulder at 1 AU, let alone a pebble. Remember that such a rock would be near absolute zero, and could well be coated with fluffy carbon or something to produce a vantablack like, radar absorbent, coating.

    You place part of your detection system far in the front of the starship. Could be something as simple as a cloud of droplets or dust. Anything that will go through it will glow brightly (or turn into plasma).

  8. The fission products are iodine 129 and Indium 113.

    Since the indium is stable, you're only worried about the radioactive iodine. But with a half-life of about 16 million years, it really isn't radioactive enough to worry about from a biological standpoint. It's not the isotope you worry about in nuclear reactor accidents.

    So, it's relatively clean, actually, compared to Pu. In fact, the chief radiation hazard would be the Cu that didn't fission.

    Kind of irrelevant, though, because it's hugely more expensive than Pu.

  9. My favourite Orion thought-experiment is the Super-Orion, one of Freeman's little dalliances in the late 50s, at 400m(!?!) in diameter with 3000t 'bombs' of thrust (over 1000) with a huge and dense pusher plate. But isn't the survival of crew, generation ship residents, and such, limited to accelerations of 3g-ish??

  10. BTW, it was a relatively minor space competition that drove the idea for testing the Orion drive concept in the first place. If it was not for the competition between the US and USSR, we would not be chatting about an Orion drive right now.

  11. Sure, kept them from being built yet.
    The burgeoning commercialization of space, falling launch costs and greater national security and economic interests will eventually change that. Just like when Spain, England, the Netherlands and France used to scrap back in the 1600's, it will take a while but odds are that interests in space will eventually clash.
    Moving large mass asteroids doesn't require an Orion drive, as long as your commercial interest has a few decades to wait for it to be moved to where you need it (yeah right!). You can build space shuttle size military craft, and that will be great until someone else (a competitor) pulls up in a Cadillac 50k ton ship and flattens your space time continuum.
    Great Power competition, and the interests that intertwine with it, are a real phenomenon as history shows us. They have driven much of the military and trade advances for the last few centuries and are not likely to go away now.

  12. Current thinking is not a thick shield, but multiple thin shields.

    Something hits the first shield, punches right through it, vaporising in the process. The spray of vapour and debris hits the second shield etc.

    With enough shields they will stop anything coming through and as the front shields turn into swiss cheese the next layers take over their function.

    Whether ice is the best choice, or something else, is a different question.

  13. The problem with existing micro nukes (OK, the one problem relevant to this discussion) is that they are so much less efficient than the big boys.

    You get a nuke that is say 1/10 the mass. But it costs 1/2 as much to make, and gives 1/1000 the output.

    So if you scale down from 100 kT nukes to 100 T nukes (about the smallest made that I know about), you end up with a spaceship that costs half as much to fuel, but is 1/10 the total mass but only 1/1000 times the impulse available.

    If the first ship can go to 500 km/sec, then the second one only gets to 5 km/sec, which isn't any better than a chemical rocket.

    Scaling UP on the other hand, you get a hydrogen bomb that's 10 times the size, maybe 10 times the price, but 1000 times the energy. Now you're talking.

  14. There is only one thing that will keep these from being built, and that is a drive even more powerful. As the general said back in the 60's, whoever controls this drive controls the world.

    But it's been 60 years since the 1960s, and something HAS kept them from being built.

  15. Maybe you can detect a rock a metre across at 1 AU. But what about 10 cm across? 1 cm? That's still going to blast a hole through steel plate at that speed, and detecting it gets more and more difficult.

    The point isn't (I think) that this is physically impossible. The point is that we, in 2020, have several ideas about how to accelerate a probe to 0.1C (such as the Orion drive ).
    Some of these approaches are straightforward enough that we could probably start a project to do them today, if we had a $Trillion to spend on such a project.
    But we don't have a hope of detecting even a boulder at 1 AU, let alone a pebble. Remember that such a rock would be near absolute zero, and could well be coated with fluffy carbon or something to produce a vantablack like, radar absorbent, coating.

    It's like if Europeans wanted to cross the Atlantic circa 1500… but the ocean was filled with reefs and rocks that could tear out the bottom of any ship. Yes, you could develop underwater sonar systems to detect such rocks, but that is way, WAY more advanced than the original ship building tech.

    Of course we have no evidence that such rocks are common. It's all speculation as this point. No people from the other side of the Atlantic have visited us, therefore there must be something preventing them from crossing.

  16. Would the fallout and general behaviour of the gadget vary much from using Plutonium to using any of those two? It's not like salting, is it? The half life of that Curium made me wonder how much worse it could be…

  17. There is only one thing that will keep these from being built, and that is a drive even more powerful. As the general said back in the 60's, whoever controls this drive controls the world.
    Like it, admit it or not, we are in the beginning stages of another Great Power competition. These usually have ended up in commercial competitions followed by wars in the past, and no country or group of countries can afford to give up the type of advantage that technologies like this can achieve.
    I keep reading in posts here that the "NIMBY's" and public opinion will disallow these from being built, but this is very US centric thinking.
    Do you think China, Russia, or other countries that develop a space program will care about public opinion against it, allow this to stop their plans? I don't.
    Do you believe China or other countries will allow small nuke security concerns stop them from building battleships or develop powerful commercial craft in space if they believe it will give them a qualitative advantage vis a vis other "competitor" countries. I don't.
    Military ships powered like these could make the nuclear ICBM arsenal of the US obsolete. Can you think of a real reason why a Great Power competitor would not want to pursue this? I cannot.
    Right now the US and our allies enjoy an advantage to get there "the firstest with the mostest" in producing and harnessing this technology. The only thing that can stop us is wishy washy squishy thinking which will only hurt us in the long run.

  18. I thought that if you put a thick shield of ice 10 km in front of the
    ship you'd be able to stop incoming sand, and even the occasional
    little rock.

  19. Nah, if there were that much solid matter out there, we'd actually see it. Looking at the stars would be like looking through a fog.

  20. In a word, no. Whatever dark matter is (if it indeed is at all), it most definitely is not made of protons and neutrons. So it is not hydrogen, it is not helium, it is not water, it is not silicates and it is not nickel-iron. Even cold dust interacts with starlight in a particular fashion that makes it straightforward to show that it is there, and we haven't seen any sign of dust or gas in the quantities that would be needed to explain the motion of galaxies, which is why we were forced to postulate dark matter in the first place.

  21. Well, let's hope that Elon Musk can tie the evironment to launching big rockets. You see, if it is for the environment, nobody dears to protest or even utter a logical thought. Since I personaly like mars colonization, I hope that he will bring out the "environmental weapon" to slay the "protect the rocks" cult.

  22. Pick a mesa in Southern Arizona. The launch pad can be an arm extending over the edge. Granted, a really strong arm. Maybe make it a rotating arm, two ended, so you can be assembling a rocket on one side over the mesa, while getting ready to launch off the other end, over empty space.

    The arm isn't much more than basic civil engineering, lots of concrete and steel.

  23. The low birthrate probably helps too. If somehow in the modern world England spent their blood conquering France, there wouldn't be enough survivors to fill both countries. And it would just continue to dwindle from there.

    For developed countries, people are now worth more than land.

  24. In such case you simply avoid the collisions. Assuming you are flying at 0.1c and your radar is able to detect the stone from a distance of 1AU, you have about 1.5 hours to descend from the collision trajectory. You do not have to change the direction of flight. All you have to do is slowly move in a direction perpendicular to it.If there are enough such pebbles to be a problem in navigation, you can start collecting them (of course, you'd need to fly much slower than in example above), assuming that gravity has not already done it for you. BTW, if space between stars was densely packed with tiny objects, shouldn't we see that?

  25. In 2016 Musk showed the ITS design (12m diameter, ~10kT launch mass). In 2017 a reduced version was presented, the BFR (9m diameter, 50% of ITS mass). Both versions, 9m and 12m, have the same payload/launch mass ratios. So, there may be some gains in 18m version, but probably not so dramatic as you hope for.I bet that Brian automatically assumed that the height of the rocket will also double (so 8x bigger mass). It's not going to happen, for many reasons.

  26. Treaties don't have to make it impossible if they bring the signatories to the treaties in on the missions, so they will be satisfied to sign off on it.

  27. Aha! Another potential solution to the Fermi Paradox – an interstellar Kessler Syndrome triggered after there got to be too many starships flying around in a distant past stellar empire!

    (If we stretch this theory really hard, we can also make it cover how the dinosaurs got wiped out.)

  28. A thousand tonne Orion has (if I recall correctly) about 500 tonnes of "fuel" on board, which consists of shaped charge nuclear bombs.

    I don't know what fraction of the bombs actually consists of hydrogen, but I would be surprised if it's more than a few %.

    So maybe 10 tonnes of hydrogen? Something like that. Well worth spending for that level of interplanetary capability.

  29. "some of the largest bodies there are big enough for hydrothermal processing to have taken place". The hope is that there were even larger bodies that were then broken up after some processing. Saves digging! We need just a tiny amount to get started, and the quantities are astronomical. *Ore*, it may be that we are processing so much stuff for all reasons, as everything material is useful in Space, that we get enuf from poor concentrations. I would hope that the blast shield is far massier than the fissile material, and not launching the shield is a big advance.

  30. We could build a space elevator for the moon with materials we have available today. Mass drivers to put bulk materials in to LLO too.

  31. Even fresh water isn't good for a super big rocket.

    Frequent reuse with minimal turn around time is what you really want to drive down cost.

    If you must go with some mega launcher then I would go with a raised launch pad, maybe something crazy like a tower raised 500 feet so the engines could fire down in to a freshwater lake. A problem is that the sound reflects off of the lake and comes back up at the rocket. You'd have to work out how to not melt the launch tower.

    It is just a mess, stick to smaller, more readily reusable rockets. Bigger rockets aren't necessarily better.

  32. Depends on the size distribution. A lot of objects 100m across or more does make it easier to diffuse across interstellar distances.

    A lot of objects 1 m across or less just pose a hazard. It's only a couple of tonnes so it isn't worth matching velocity with to get the resources, but if you hit it at interstellar velocities your spaceship just adds to the debris.

  33. You want to see Orion in space, hope for Musk's Mars colony. Fissile elements are concentrated into ore bodies by hydrothermal processes, Mars should have plenty of Uranium and Thorium ore deposits, untapped. The Martians would embrace nuclear power.

    You *might* find some such in the asteroids, some of the largest bodies there are big enough for hydrothermal processing to have taken place.

    But I don't think you'd find Uranium or Thorium ore on the Moon, due to a lack of water to permit hydrothermal processing over a long period.

  34. Right on the treaties. I don't expect Orion to be built until it can be built by people in space, not being micromanaged from Earth.

  35. The 9M starship has a wet mass of 5,000 tons. Out of that it can put 100 tons into orbit. 2% of it's wet mass.

    If you took 4 9M starships and bolted them together, you'd have a wet mass of 20,000 tons, and a payload of 400 tons.

    BUT, if the double diameter Starship is structurally more efficient than four single diameter Starships bolted together, you could end up with a wet mass of 20,000 tons, and 1,000 tons of payload. 5% payload, instead of 2%.

    I think that's maybe a little optimistic, but 3-4% payload, 6-800 tons, would not shock me.

  36. Backpack nukes. God. I need an adult lol. All sorts of practical uses for that, some humanitarian, others wholly terrifying.

    "Yooo! Dude, is that a backpack nuke?!"
    "Hell yeah! I thought I'd try molting, today!"
    "Bro, that's legit!"

    I have faith in humanity. 😀

  37. It might certainly be possible that there is some kind of matter out there, rocks or otherwise, that actually acts as a great filter to civilizations going out and spreading across the cosmos. I see no reason why there couldn't be something like that (though, as an eternal optimist [because you get to drink and party harder when you get let down lol], I'd rather that not be the case).

    Particles of pulverized planetary bodies, etc, could perhaps be so prevalent that they really do prevent large-scale colonization.

    I ain't gon' lie, though, dude; if we find out that dark matter– after ALL this time, and ALL this money spent on research and heavy testing– is ROCKS… I'm'a fall out harder than a drunk macaque, because I know a couple folks who would be HARD LIT over that. I might stop laughing after a month.

  38. Yeah, rocks can't be the correct answer. The odds of successfully navigating an asteroid field would be > 3,720:1. Can't have that. Can't have a number of rocks > 9,000. That's illegal.

  39. That's really the way to go about getting things done at a more intensive speed. Production of craft in space would be far superior to having to launch things to Earth escape velocity (which, if I recall, is ~11,000 kilom… alot… *looks again* yes, it's a lot).

    I have the feeling that any spacecraft that can only be half-jokingly be described as "da bomb" probably is worth another whack at the drawing board before we go cruising around in it. We really do have all the resources necessary in space to manufacture craft that would remain in space and are equipped with smaller landers.

  40. Lots of mater between the stars does not explain the Fermi paradox – it amplifies it. An ocean seeded with the islands (even very tiny) is much easier to cross than the empty one.

  41. 1. Orion cannot happen cause the treaties.
    2. Double diameter Starship means 400+ tons of payload, not a thousand.

  42. They will be throwing valuable volatile elements to space with Starship too.

    Which is fine for the first decades, I guess, but longer term the water on the ground will be quite more valuable if it circulates and is not lost to space.

    Happily, the Moon's lack of atmosphere and lower gravity make others options viable.

    Just build some nifty mass drivers and a space elevator, which could then be used to launch people and cargo from the moon without wasting valuable elements.

  43. I'm all in favor of cactus hugging for 'em.

    But yeah. I see them doing that. They already want to restrict human spaceflight to "protect" dead rocks and avoid colonialism. So any other lunacy as excuse isn't off the table.

  44. It would require more infrastructure, that's for sure. I think that you'd have to launch from up a tower, high enough that the exhaust would be diffused before reaching the ground.

    There are plenty of suitable locations *if* we get away from the demand of launching over the ocean. Desert land where there's nobody for miles, except for watermelons attempting to be human shields for cacti.

  45. The only thing that has made us "grow up" is fear of reprisal. Our weapons are so terrible and they are distributed evenly enough to inspire us to be wary of reckless behavior at the international level.

    Self interest also kicked in, when warring became uneconomic because if you destroy a modern country, rebuilding it to working state becomes a net money sink.

    Deep down we still are the same wild savannah apes, with just a coat of culture and civilization.

    Thucydides of Athens is still relevant.

  46. The problem with the low critical mass isotopes is that they tend to be very "hot". The notable exceptions are Curium 247, (half life 15.6MY) and Neptunium 236, (half life 154KY). Both have a critical mass of about 7kg, compared to Plutonium 239, already used in nuclear bombs, which has a half life of 24KY and a critical mass of 10kg.

    So, some improvement is available that way, but I wouldn't say a lot of improvement. Sure, a lot compared to U235, but nobody uses that in small bombs anyway, so that's not a realistic baseline.

  47. Well, the point was that we don't want to launch it at all. We want to make it in Space, or on the Moon (which I dispute), and use in Space. ALL radiation concerns are then mitigated. If you think of the *thing* being launched as a product, you will be able to launch a factory for that product to Space cheaper than a *bunch* of the products, esp if the factory can make various products. The shields for Orion blast seem an ideal thing to not launch!

  48. Mass drivers could be used to fling material into lunar orbit or earth orbit to make space ships. No atmosphere makes it possible.

  49. Orion doesn't have to be big. There are nuclear isotopes with critical mass that is much less than U235 and Pu239. Which means you can build very small nukes. Which means that Orion can be made much smaller. In fact, it may be possible to make miniature hydrogen bombs, which would make Starships possible.

    Of course, very small nukes and hydrogen bombs do have a serious downside. You can carry one in a backpack.

    It seems if mankind want the stars we will have to grow up.

  50. You don't launch a Project Orion from the ground under nuclear power. Rhys Taylor did a great animation showing a 4000 ton Project Orion being lifted about the Karman Line with shuttle reusable boosters. That would minimize the fallout from irradiated air and assorted ground material. It has been a while, but I ran the numbers and it could work with 20 to 30 SRBs. I don't remember the exact figure, but it was in that range. Now the craft wouldn't be moving all that fast, but if it was tilted over before firing up the nukes, much of the radioactive debris would be shot out of the atmosphere and into solar orbit.

    Of course, you would still be killing a lot of non-military satellites from EMP. And you would be injecting a lot of radioactive material into the Van Allen belts. Still, it would be amazing to watch from the ground when it lit up…

  51. Yup. The infrastructure requirements for the launch pad are correspondingly harder to fulfill. Nevermind developing (and financing) the rocket itself. Every time they created a rocket, it has been a new different problem with a lot of new challenges.

    And the sound a rocket that size would make will be a problem anywhere.

    I take this "Starship 2.0" as a mental exercise for the moment being.

  52. He's not suggesting the rocks are zipping around at high speeds, he's suggesting they're out in the interstellar void, and Fermi Paradox may be explained by high-speed ships running into them if you try to colonize other stars.

  53. You could address the saltwater and wildlife concerns by dredging part of Lake Okechobee in Florida and launching from there. Fresh water, man-made lake, and no species present there that aren’t present elsewhere in the SE U.S. Also largely uninhabited.

  54. It gets difficult to launch such a large rocket. You run in to problems with tearing up the launch pad with tens of millions of pounds of thrust. Concrete doesn't survive that.

    No you can't mimic sea-dragon and launch from in the ocean. First of all dipping the rocket in sea water is bad for reuse. Secondly you kill all the wildlife in the ocean with the sound (which offends the "inner party-decolonize-NASA" crowd who call the shots).

  55. What do you fuel it with? Hydrogen is valuable on the moon and you aren't going to throw 1,000 tons of it out the back of an engine.

  56. Well that's random but the answer is no.

    It would take thousands of 100kt non radioactive explosions to wipe life off of Earth.
    We haven't observed any.

    If the rocks were zipping around they would hit other planets (Jupiter) and be noticeable.
    We haven't observed any.

    So not happening.

  57. Is it possible that dark matter is made of small rocks? Travelling
    at 0.1 c and meeting a 1kg rock would be like meeting a 100kt
    nuclear warhead. If such rocks are abundant enough, that could
    explain at least a part of the Fermi paradox.

  58. Or, launch the factory to make the factory to make the craft, and lots more, from lunar/asteroidal material. Big rockets do not make this a bad plan, rather a faster one.

  59. "generation 2 SpaceX Ultra Heavy Starship could also launch factories and
    advanced production systems to the moon. Creating the production
    systems for nuclear pulse propulsion on the moon would remove concerns
    about nuclear radiation from a ground launched Project Orion." So would doing it in Space, which makes far more sense. Gerard K. O'Neill pointed this out almost 50 years ago. See the exciting new (to most) idea! "The High Frontier" is the book.

  60. I think nuclear propulsion from the moon makes a lot more sense.
    Nuclear elements can be mind on the moon.
    A LOT less problems if things go south during a launch, because there's no atmosphere.
    Launch area can be far away from the moon-base.

    Travel would be Earth –> Moon –> Other area in Solar System

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