42 thoughts on “The Absurdity Of NASA’s Lunar Plans”
Season 2 of Snoopy In Space just came out on Apple+ TV, with Charlie Brown, Lucy, Linus, and the rest. It was made in close co-operation with NASA, and I suspect it might present more realistic mission profiles than SLS/Orion.
Much I love SpaceX/Starship and detest SLS/Orion, this video is a good example of why SpaceX supported get called “fanbois.” Fully refueled in LEO, Starship doesn’t have the delta-V to carry out the mission described (LEO to lunar surface to LEO). At a minimum, it would have to be fully refueled on the surface of the Moon. Since that’s out of the question until after a large moonbase is set up, it would have to be topped off in high earth orbit, then refueled again in lunar orbit post landing by tankers that would themselves have to be refueled in LEO. Some guesses are 15 to 20 Earth launches. Then the video trots out the dumb idea of laying down Starships to make moonbase parts. That this is a widespread meme doesn’t make it less dumb. It’s just a variant of the wet lab idea and the “let’s save up external tanks in orbit” idea. All of this gets in the way of one idea that would work: refueling and resupplying lunar Starship in NRHO for subsequent missions of NRHO-lunar surface-NRHO. Ten reuses would probably be fine. (And somewhere, someone is preparing ti rebut the video by trotting out the Aldrin Cycler dumb idea.)
If a spacecraft is refueled in Earth orbit, that spacecraft can go to the Moon, land, take off, and head back to Earth orbit. On that same tank of fuel. That same spacecraft, if refueled in Earth orbit, could go to a near Earth asteroid, land, and then head back to Earth orbit. With the same amount of fuel, as it would take to go to the Moon. Even if the NEA is 10 million miles away.
G. Harry Stine mentioned that in a book called Halfway to Anywhere. The book was about the Delta Clipper program.
One you reach LEO, you are halfway to anywhere. That includes the Moon, the NEA, and Mars two moons.
You can land on Mars, but you will have to refuel before coming back. On the Moon, the gravity is 1/6 that of Earth. So it would require less energy to take off, or to land.
These things are all what I call “trivially true” in that they’re not ruled out by physics and have too few details to be tested. I liked Harry, back in the day, but he oversold stuff, as most writers do at the behest of editors who a) don’t know much, and b) get paid to sell publications.
Anyways, we’re not talking about “a spaceship” here, but the evolving SpaceX Starship and it’s lunar HLS derivitive. This is a vehicle with an 80% mass ratio and already existing Raptor engines, that has a fixed and known delta-V budget which is wholly inadequate for the described LEO-Moon-LEO mission, by about half. Look at it this way:
The standar Starship that will be used for dear.Moon has enough delta-V to liftoff from Earth and, without refueling, push itself through TLI, follow a free return trajectory, aerobrake through Earth’s atmosphere, and land using the fuel in its header tanks.
When fully refueled in LEO, that same Starship could push itself through trans-Mars injection, aerobrake through Mar’s atmosphere, and land using the fuel in its header tanks. It cannot return to Earth without being fully refueled on the surface of Mars using fuel manufactured on Mars, That’s the actual plan.
That Starship, fully refuelled in LEO, cannot fly to the Moon, land, and take off again. To do so, it has to be refueled a second time in a highly eliptical high Earth orbit. Then it can land, takeoff, go through trans-Earth injection, aerobrake through the Earth’s atmosphere, and land using the fuel in its header tanks.
The HLS Starship cannot aerobrake, because it’s heat shield and aerosurfaces have been deleted. Fully fuelled in LEO, it can fly to the Moon, land, then take off and put itself in orbit around the Moon, where it can offload its crew to an Orion. That’s the actual plan. Secondarily, it can drop off payload on the Moon and then reach Gateway in near-rectilear halo orbit. That’s also the plan. This version can be refueled and resupplied in cislunar space, and reused some number of times. That’s not the plan yet.
These facts are easily looked up, and the math is not too difficult. Start by looking up “delta-v budget.”
Musk has hinted that HLS may be able to get buy with only 600 tons of fuel in LEO and still do the described mission. That would mean shrinking it to about half size of course, by making it 25 meters tall instead of 50 (but still 9 meters in diameter). What does that say? NASA has specified 4 crew, permanently. A half-size HLS Starship is still more than big enough.
I crunched lots of numbers on a lunar Starship a year or so ago. Refueling in GTO lets it get to the moon with lots of payload, but a refueling Starship can’t deliver a significant amount of fuel to a GTO orbit. It arrives in LEO with such a low fuel fraction that it can barely get to GTO and back to Earth with no payload at all.
My conclusion for the transportation pipeline problem was that Starship is doing too much of the work of getting to LEO compared to Super Heavy Booster 1A ver1.0 tranche 1. It needs a bigger booster that supplies more of the launch’s delta V, but a RTLS flight profile, plus higher re-entry heating, may preclude the operational feasibility of such a booster.
Going to three stages adds complexity, especially to operations, and still leaves the problem of a 2nd stage that faces high re-entry heating and distant landing zones, or the expense of throwing away an expendable second stage.
It may make more sense to use a lot of launches with an extremely cheap launch system than use fewer launches with a more efficient but expensive system.
However, given the speed at which SpaceX can design and build boosters, right-sizing things based on operational experience should be quite easy for them. If they need a bigger booster they’ll just build one.
The main argument against all that is, Starship is squarely aimed at Mars and optimized for it. The Moon is in some sense a distraction, though I’m happy to watch the iterations of lunar Starship. It’ll be interesting if there winds up being a Stubby Starship for it.
Secondarily, a HyperHeavy booster with a fully reusable second stage would just be a SuperStarship with a cargo hold big enough to carry Starship Original Edition.
I don’t think any of that’s necessary or likely. I still expect an oversized NautilusX-like interplanetary cruiser that uses a Starship-like landing craft to emerge ca. 2040.
Lunar Starship, from what I can be see, is mass-optimized via deletion of the aerosurfaces, drive mechanisms thereof, and the heat shield. I’ll also further speculate that it’ll save some mass via having a far smaller solar array and radiator array than the Mars version. One way it’ll have extra mass is the landing thrusters.
So, if Lunar Starship is lighter, it should have more delta/v potential than the Mars version. The big question is, how much? Per Musk, the Mars version, fully loaded, should have a 6.9 KPS delta/v.
So, what’s the actual Delta/V budget for a Lunar Starship mission from LEO? I’ll do this by steps. LEO to Geosynchronous Transfer Orbit(GTO being a high energy elliptical orbit) 2.5 KPS. The mass-optimized way to do that is refuel both Lunar Starship and a tanker version in LEO (so you’re not pushing so many Starship dry masses though 2.5 KPS) and refuel the Lunar Starship, once, in GTO (The remaining prop after the GTO burn in both Lunar Starship and the tanker would be enough to fully fuel Lunar Starship in GTO). So, start out with a fully fueled Lunar Starship in GTO. To get to Low Lunar Orbit, you need 4kps. From there, it’s 1.6 kps to the lunar surface (for touchdown; lithobraking would be easier on the delta/v budget, but hard on the astronauts and cargo). So, you’ve used up 4.6 KPS of your fully-fueled 6.9 KPS (Which is for the Mars Starship, the Lunar Starship should have more than that.) That leaves
2.3 KPS remaining on the lunar surface. To get back to LLO, you use 1.6 of that, leaving .7 KPS.
Can you get back to low earth orbit from low lunar orbit with .7KPS in the tank? Well, yes, theoretically; you do a .7 KPs burn for the Earth C3 point. From there, you are on essentially an almost free-fall trajectory towards Earth – roughly an eliptical orbit, with LEO at one end, and almost lunar distance at the other end.
Then, to circularize in LEO, you aerobrake. Several of our Mars probes used this method to enter circular Martian orbit, and they had deployed solar arrays and no heat shield. A Lunar Starship would be a little more capable than that, though you’d still need multiple passes to circularize in LEO.
Did I include any margins (for safety, inefficiencies, prop outgassing, etc etc) at all? No, because I don’t know the actual Delta/v capacity of a fully fueled lunar Starship, so I’m using what the Mars version needs, and Musk says it will have. However, even moderate mass savings should supply that margin.
Did I get something wrong?
Yes, the problem is LSS can’t aerobrake because the heat shield was deleted, so you need to brun fuel to brake propulsively into LEO. Aerocapture? In theory, but then you’re making multiple passes through the Van Allen’s. Also, the GTO tanker will not be able to fully refuel LSS in GTO. On the other hand, the process you desribe is how a pre-NASA standard Starship lunar landing mission would go. The top off in GTO to allow trans-Earth injection, and then aerobraking to the surface of the Earth with full header tanks for landing. I think the current LSS is optimized to go from LEO to NRHO to lunar surface and then back to NRHO per NASA requirements. And they did win the contract, after all.
One other thing about aerobraking: the scale height of Mars atmosphere is considerably higher than Earths, so it;s much better for aerocapture and the orbit changes with saw with Mars orbiters. Musk has lately been hinting that Starship will need one aerocapture pass before full Earth reentry on return from Mars. But that’s with a heat shield, so only limited by deceleration force and heating.
Yeah.
Lunar surface with rocket fuel is like LEO with rocket fuel- but better.
Always mentioned is LEO to Mars or whatever in terms of delta-v – generally assumes it’s half empty.
And also with vehicles which have get thru hell, going thru earth’s atmosphere.
With lunar surface, the structure could withstand less than 1 gee.
1/2 gee rocket acceleration has insignificant gravity loss {around 100 m/s} -also similar from Mars surface low acceleration and about 500 m/s of gravity loss. And can lower it by doubling lunar acceleration.
Anyhow, tend to think, from lunar surface one swings by Earth, but what about just going from lunar surface to anywhere?
And from Mars surface to lunar surface. Or high Mars orbit to lunar surface, same as Lunar surface to Mars high orbit. It seems same trajectory in which low impact space rocks hit the lunar surface.
Or with lunar surface to high Venus orbit- would you go to Venus from New Moon and Full Moon to Mars. Or from High Earth [or any earth/moon orbit] use lunar gravity in same way?
Also one use first stages which are lunar reusable from lunar surface, takeoff at 1 gee, and second stage is 1/4 gee max thrust.
Same with Mars.
Much I love SpaceX/Starship and detest SLS/Orion, this video is a good example of why SpaceX supported get called “fanbois.”
I’m sort of in this camp: SLS is a bureaucratic black-hole that will produce a barely functional rocket. I’ll give it even odds for blowing up on the pad.
But that doesn’t mean that their competition gets to magically violate the rocket equation. I actually love SpaceX for running an actual rocket program. Their program of trial and error is a far better way of developing actual hardware by building actual hardware than having it spring straight out of platonic space like Athena from the brows of Zeuss, only in a billion gigabyte powerpoint deck.
But they still don’t get to violate the rocket equation. Space travel is hard. I wonder how they’ll manage refueling on the lunar surface: Lunar dust is a nightmare to work wtih mechanically as any kind of raw material. And the ice in the south poles is still tenuously established, and might not be plentiful enough to be blowing away as reaction mass.
You misunderstood. No one is planning to refuel Starship on the lunar surface. It will refuel in cislunar space from Earth-launched tankers and freighters. So each lunar landing will require the launch of two lunar cargo ships (one freighter and one tanker) plus some number of LEO tankers (probably eight). That’s ten launches for each landing, but at a total cost only a fraction of SLS.
Fine metal mesh with Teflon coating??
Kind of like air bags but designed for a lunar for launch pad.
Or carbon fiber, but maybe any kind oxygen rich fuel would incinerate it.
Spray paint?
Hot Liquid Aluminum spray “paint”
Lots gallons fast.
How about adding rocket fuel additive?
I’m trying to distil your comments.
Your issue is that a lunar starship needs to be refueled and that if it isn’t refueled, that it is pointless to do anything with the spent lunar Starship?
Not sure who this is directed at, but if me, no. The point is, refueling and reusing it leverages more lunar exploration than using it as a hab on the lunar surface, other than maybe the first few missions. I am opposed to the idea of tipping the landers over to use as habs. It will just at marginally useful complexity at considerable expense. Some of the cargo starships will be abandoned on Mars to, in the early days, mainly used as holding tanks for ISRU-produced methalox, and as housings for ISRU equipment that doesn’t need to be deployed to the surface.
One of the ideas I favor for lunar exploration, as an alternative to a static “moonbase” is what I’ve sometimes called Lunar Surface Rendezvous. You send a cargo ship to the Moon that deploys a large rover. Then a crewed ship comes down and drops off the rover crew. Then the rover drives off, and some time later (months) a second crew lander comes down and swaps in a replacement crew, alongs with some more supplies. You could do that several times before the rover would wear out, and explore huge amounts of Moon. If need be, you could follow the terminator, and not have to overnight.
More proof that Spacex is running a rocket program, and Blue Origin and NASA are running a P.R. program.
Scott Adam would say that Musk doing a much cheaper PR program
for everything he does, and that Elon is a friggin genius.
Huge amount PR, just doing PR the right way.
Something NASA has failed miserably at for decades, according to Keith Cowing.
And amounts to having crown jewels, but it is a perfect secret, due to the endlessly overpaid morons.
What’s the deal with that image of a tall lunar landing craft touching down on those bitty legs? Wasn’t that the “knock” on the original Direct Ascent versions of Apollo, the technical difficulty of landing something the size and shape of an Atlas stage without having it tip?
Is the assumption that there is some manner of a landing pad prepared ahead of time on the Moon?
The Moon doesn’t have crosswinds, but unimproved lunar surface can have considerable slope to it?
The video is a collection of iobsolete images. The current HLS is the one with the big, triangular, permanently deployed (“fixed”) landing gear. That’s part of my problem with it.
Hmm, I wonder if the engineers at SpaceX have given any thought to those issues.
I always hark back to the many people who asserted Falcon 9 would not work because, “Musk will find out that Merlin will not work when there are 9 engines pluming.” These are the same people who later claimed the price of Falcon would have to go up, or else Musk must be “dumping.” Which wound up with the EU making that legal claim, only to be shown the secret facts, and back down at once. If Musk said he had a working FTL drive, I’d recall he already told us he was a shipwrecked alien advancing Earth’s technology so he could get home.
…And you wonder why SpaceX has fanbois?
More like I’m wondering why there aren’t more of them. If Musk had come along when I was a teen, I’d’ve been trying to convince my sisters to have his children…
But what would the reaction be, if Spacex lands a civilian on the Moon, before NASA sends any astronauts to the Moon. Say Musk sends 11 people to the Moon. A billionaire, and 10 of his friends. Or maybe company employees for a mining company. What would be the reaction from congress be? What would the reaction from NASA be?
How much coverage would this be for the news media? Would we see several hours of news broadcast from the Moon, like the Apollo 11 Moon landing? And what will tax payers say about spending $ billions on a rocket, when a private company is doing it cheaper?
This might be a great science fiction story. Say a short story for Analog, or Asimov’s.
Or maybe company employees for a mining company. What would be the reaction from congress be?
A man with no ethics who’s attempting to spread Global Warming on the Moon.
How Dare You!
I’d’ve been trying to convince my sisters to have his children…
Yes, then we’d have kids named F101Voodoo, F4GWildWeasel, A10Warthog and of course C97JSuperGuppy!
In order for SpaceX to land people on the Moon before NASA, it would have to have an FAA launch license. If Musk did it without the license, he’d go to prison. If he did it from another country, he’d wind up in Guantanamo.
Some people take more convincing than others.
“Let’s be very honest. We don’t have a commercially available heavy-lift vehicle. The Falcon 9 Heavy may some day come about. It’s on the drawing board right now. SLS is real.” — Charles Bolden, 2014
“SLS will go away. It could go away during a Biden administration or a next Trump administration… because at some point commercial entities are going to catch up. They are really going to build a heavy lift launch vehicle sort of like SLS that they will be able to fly for a much cheaper price than NASA can do SLS. That’s just the way it works.” — Charles Bolden, 2019
The genius of Starship is in its simplicity and flexibility. The definition of Starship is, a stainless steel tube with three bulkheads and a nosecone. The tube is made from a stack of standardized rings. Everything else (heat shield, engines, flaperons, etc.) is fitments. SuperHeavy is a Starship with the nosecone left off and more rings on the stack. In theory, you could build a space tugboat with four rings and three bulkheads, outfitted with some plumbing, an engine, hot gas thrusters, a battery, and some electronics.
It’s like he’s built a shipyard that can weld-up pretty much anything he thinks up in six or so months, perhaps less. They’ve got the engines pretty much nailed down, along with almost all the critical systems. He can change the diameter just by using different rings and building a different launch base. He’s already brought up the idea of doubling the rocket’s diameter, which if you count the upper-stage mass, would be like launching two-ISS stations per launch.
If NASA was on the ball, they’d be making all future plans based on the new capabilities Starship and its offspring bring to the table, in terms of a one-hundred fold reduction in cost to orbit, a massive increase in payload size and weight, and extremely high flight rates. At the very least, they should be dreaming up a LEO space station for the Starship era, with artificial gravity and some areas with radiation shielding.
Regarding cislunar refueling, I’ve seen calculations that suggest the fuel cost for landing landing from Gateway is approximately the same as a one way trip from Gateway to LEO. Gateway’s location is to accommodate the limitations of SLS and Orion, so without those, LLO is not out of the question (though this has its own issues). I think would be just as easy to do the refit in cislunar space as in LEO, so there’s no special reason to bring LSS home between landings. On the other hand, a Starship based translunar shuttle would be cheaper to build than LSS and could also be based in LEO. This starts to add up to a translunar ecology similar to what was orginally called the Space Transportation System (ground to LEO Shuttle, LEO to LLO nuclear shuttle, LLO to Lunar Surface Shuttle, all servicing a moonbase and molabs on the Moon). I’d’ve liked to see it in the 1970s, but will be happy to see it now.
Hmm. I can’t help but think that for a LLO to Surface Shuttle why not base it on GH2 and GOX? Could you super-compress and densify as gases w/o the need to liquefy? Then you could at least take advantage of any electrolytic-ally separated water found on the moon for the moon closest operations and not have to ship propellant all the way from Earth. A radical departure from Starship in the propulsion area, maybe not so much in others? A hand-wave I know. For me to work the math would take 10x longer than the other folks here.
Even easier I just realized. Use nuclear thermal for LLO/Lunar Surface shuttle and possibly LLO to LEO stages. Then you don’t even need to separate the liquid water. Wonder what it’d take to get Elon to consider a NTR?
NTR has the same problem as anything else nuclear. You think FAA is a pain, try the the DoE and the NRC.
SpaceX makes engines fueled by hydrazine, kerosene, and methane. It seems likely if Musk put through a work order for a hydrogen engines tonight, the prototype would be on a test stand in Macgregor in just a few months.
Moon Fact Sheet
Escape velocity (km/s) 2.38 km/sec vs Earth’s 11.2 km/sec https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
2.38 km/sec = 5,312 mph and 11.2 = 24,998 mph
The moon has very little gravity loss in terms of the Moon’s
mass {the Sun’s gravity loss is difference matter or at Earth’s orbital
distance the Sun’s escape velocity is 42.1 km/sec. Or wiki:
“On Earth; Earth’s gravity 11.186 km/sec
At Earth The Sun’s gravity 42.1 km/sec to escape solar system: 16.6 ”
[[“In this table, the left-hand half gives the escape velocity from the visible surface (which may be gaseous as with Jupiter for example), relative to the centre of the planet or moon (that is, not relative to its moving surface). In the right-hand half, Ve refers to the speed relative to the central body (for example the sun), whereas Vte is the speed (at the visible surface of the smaller body) relative to the smaller body (planet or moon).”]] https://en.wikipedia.org/wiki/Escape_velocity
Right-hand:
At the Moon: The Earth’s gravity 1.4 km {{leaving earth gravity well] and 2.42 km {{ escaping Moon relative to earth/moon gravity- I would say such as going to opposite side from Earth/Moon to L-3 not vaguely effected by Moon’s gravity- but not escaping the sun’s gravity well. Though since going about 30 km/sec at 1 AU orbit around Sun, with hohmann one can add about 12.1 km to 30 km velocity to get solar escape of 42.1 km/sec.
Of course using gravity assists one can leave solar system with less
delta-v. And delta-v given by chemical rocket {or any rocket} is improved by Oberth effect. Or if chemical rocket would give a total 12 km/sec, it gives more if rocket engine is traveling at faster velocity. Or these numbers are related sudden acceleration [cannon] or sudden deceleration {hitting a wall, atmosphere or rocky surface}.
Anyhow. So the 2.42 km/sec number is related to about slowest impact velocity space rock could have on lunar surface. Add a bit and space rock could come Mars distance- so like, about 3 km/sec
though a space rock {coming from anywhere can also be less impact than 2.42 km/sec. Or something like, 1.4 km/sec is lowest possible lunar impact velocity from a space rock.
–William Barton
November 14, 2021 At 7:11 AM
In order for SpaceX to land people on the Moon before NASA, it would have to have an FAA launch license. If Musk did it without the license, he’d go to prison. If he did it from another country, he’d wind up in Guantanamo.–
Maybe he could sell starship to the Space Force.
Or maybe the Canadian and/or UK space agency wants to go to the Moon.
But that’s a bit silly. He should instead but artificial gravity station in LEO using Falcon 9.
Be first to make an artificial gravity station.
This largely about PR, btw.
Sure it’s practical or needed to have human settlements on Mars.
But it’s cheap and it’s fast- but it’s important now, because it’s low cost PR thing.
I keep saying, an artifial gravity station won’t be cheap. It will cost more than setting up a permanent base on Mars. And what PR? No one cares except a very few enthusiasts, or will even know what you’re talking about. Mars looms somewhat large in the public imagination. “Space wheels” don’t.
“I keep saying, an artificial gravity station won’t be cheap.”
That because you talk of wheels, and not of sticks.
If artificial gravity is done with stick {a tall cylinder}
it’s a lot cheaper.
So, put 20 meter high cylinder on top of falcon 9 stage [which
less than 20 meter in length] and 20 meter is same diameter {12 feet] as falcon 9 stage is.
There are details. But basically you have 20 meter radius to spin and/or one attach with cable/rope a dragon to it {giving a larger radius].
20 meter radius might be too short of radius. But see if it is too short, if too short, use rope and dragon capsule to find the right radius.
NASA trying to see if one can adjust to very short radius- and this is much larger radius.
In one sense, you’re completely wrong about this. Cost correlates with size, not architecture, so a “stick” that can host hundreds or thousands of people for long periods of time is going to cost in the same ballpark as a wheel or cylinder the same size. A rope with two Dragons on the end isn’t an artificial gravity “space station,” it’s a waste of money joke.
Another point, often overlooked is, free axis spinning objects other than spheres are unstable. So sticks, wheels, and cylinder are going to wobble, only adding to things like docking problems for visitors. O’Neill knew this, which is why his space colonies were counter rotating cycliders connected by bearings at the ends. A practical AG space station would essentially be a 3-axis stabilized core with counter-rotating AG habitats (wheels or cylinder, doesn’t matter, but wheels more likely) mounted on bearings. The technology for such bearings was mastered in the 20th century (e.g. the Galileo probe). Cost? Scaled to size. The original NautilusX design was expected to cost $3.8bln 15+ years ago. Now? Probably twice that. Scaling it up a thousand times (for 6,000 crew instead of 6) would not cost a thousand times as much, but maybe a hundred times (so $380bln at a guess)?
There are no “cheap” AG space stations, andf two cans on the ends of a cable has long ago been tested (Gemini + Agena) in the 1960s. Even if your Venus space station was the right idea, how small could it be? For a few hundred crew waiting for a ride? If it’s for 6 or 12, you’re not building a space faring civilization.
“In one sense, you’re completely wrong about this. Cost correlates with size, not architecture, so a “stick” that can host hundreds or thousands of people for long periods of time is going to cost in the same ballpark as a wheel or cylinder the same size.”
First, I am talking about testing. Testing in sense of, is some radius distance and say 1/3rd of artificial gravity making you dizzy. And if spend hour or so, can your brain “manage it”.
So the stick has floors, floors have different levels of artificial gravity. So, you on top floor, and 5 mins of dizzy
you don’t think it’s getting “better”. Meanwhile other are 3 floors down, and how they feeling after 5 mins. And what about the people on the lowest floor after 5 mins.
And way designed it, one could move water mass, from top floor to basement, this acts like brake or accelerator to spin. Or could start pretty slow with the rate of spin, pump water from top floor to basement {bring arms in to increase spin} and one test the effect, and crew instead leaving station, could go to lower floors {if that helps make them less dizzy]. If station can only make you too dizzy and can’t get use to it. Have long rope, attach to end, start at furthest distance, does it make crew in dragon capsule too dizzy and can’t get use to it?
After do this, you have some clues about how to make better artificial gravity space stations. And have not wasted a lot money making an expensive wheel.
“can host hundreds or thousands of people for long periods of time is going to cost in the same ballpark as a wheel or cylinder the same size.”
Well, with stick, but not this spend falcon second stage plus 20 meter cylinder, you can live at both ends.
And one made a stick have low mass structures, the structural strength depends gee load out at furthest radius.
So with falcon 9 + cylinder and dragon capsule with total mass of 9 tons, if capsule is given 1/3 of gee, the rope needs to strong enough for 3 tons. If rope attached to a starship which is 120 gross mass, rope attached to it need to be strong enough for 40 tons {though less because one having crew part at the top of starship getting the 1/3 gees]. With stick one could large mass in middle of it, which not get much gee, and not need much structural strength. So with wheel one is having a lot mass which is
at highest levels of gee load {require lots of structural strength from the spokes and also have lateral load of wheel itself. This can quickly get very massive.
So, rather than wheel holding 100,000 people, have 100 sticks with 1000 people. It should less mass of structure and in terms water [shielding and thermal control] one stick station could hold more water mass then 100,000 people wheel. Or a big sphere with ends of sticks going thru it and out north and south poles. People could spend
most of time in higher artificial gravity but spend say 1/8th of time in parts of stick with less gravity [or microgravity}. Most time being mostly sleeping and working. and shopping or entertainment could have less time in which one spends time- swimming, playing sports, watching sports, and whatever don’t have to be at the ends of stick.
As far as testing goes, it’s a proven concept using old techology. Even the Von Braun AG space station, at 250 meters diameter, is equivalent to a small suspension bridge. There’s simply no profound reason to build a small AG station in LEO anymore.
That said, I’ve always regretted the missed opportunities of this past generation, starting with the cancellation of the Centrifuge Accomodation Module in 2005. There it sits in Japan, gone to waste. Part of the run-up for the NautilusX project would have been an ISS centrifuge habitat test module. It would have been berthed to the forward end of ISS (so with PMA-2 moved to the foreward end of its non-rotating hub) to test deploymend, and functionality of its bearing structure. Suggested uses were crew quarters, but also it could have had a gravity-dependent hygiene facility (a camp toilet and shower, for instance) and a gravity dependent kitched (e.g., with a convection oven). It would have been too small for 1g, but one-third or one-sixth it could handle, so a living on the Moon or Mars simulator. But it didn’t happen. You’ll notice the above discussed AG facilities enhance the functionality of ISS, as well as test concepts and materials.
Maybe something like that can be added ti the Axiom Station, or a larger one for Orbital Reef. I do think Axiom will be the next US LEO station, though I have a hard time believing in anything involving Blue Origin after this year’s shenanigans.
Season 2 of Snoopy In Space just came out on Apple+ TV, with Charlie Brown, Lucy, Linus, and the rest. It was made in close co-operation with NASA, and I suspect it might present more realistic mission profiles than SLS/Orion.
Much I love SpaceX/Starship and detest SLS/Orion, this video is a good example of why SpaceX supported get called “fanbois.” Fully refueled in LEO, Starship doesn’t have the delta-V to carry out the mission described (LEO to lunar surface to LEO). At a minimum, it would have to be fully refueled on the surface of the Moon. Since that’s out of the question until after a large moonbase is set up, it would have to be topped off in high earth orbit, then refueled again in lunar orbit post landing by tankers that would themselves have to be refueled in LEO. Some guesses are 15 to 20 Earth launches. Then the video trots out the dumb idea of laying down Starships to make moonbase parts. That this is a widespread meme doesn’t make it less dumb. It’s just a variant of the wet lab idea and the “let’s save up external tanks in orbit” idea. All of this gets in the way of one idea that would work: refueling and resupplying lunar Starship in NRHO for subsequent missions of NRHO-lunar surface-NRHO. Ten reuses would probably be fine. (And somewhere, someone is preparing ti rebut the video by trotting out the Aldrin Cycler dumb idea.)
If a spacecraft is refueled in Earth orbit, that spacecraft can go to the Moon, land, take off, and head back to Earth orbit. On that same tank of fuel. That same spacecraft, if refueled in Earth orbit, could go to a near Earth asteroid, land, and then head back to Earth orbit. With the same amount of fuel, as it would take to go to the Moon. Even if the NEA is 10 million miles away.
G. Harry Stine mentioned that in a book called Halfway to Anywhere. The book was about the Delta Clipper program.
One you reach LEO, you are halfway to anywhere. That includes the Moon, the NEA, and Mars two moons.
You can land on Mars, but you will have to refuel before coming back. On the Moon, the gravity is 1/6 that of Earth. So it would require less energy to take off, or to land.
These things are all what I call “trivially true” in that they’re not ruled out by physics and have too few details to be tested. I liked Harry, back in the day, but he oversold stuff, as most writers do at the behest of editors who a) don’t know much, and b) get paid to sell publications.
Anyways, we’re not talking about “a spaceship” here, but the evolving SpaceX Starship and it’s lunar HLS derivitive. This is a vehicle with an 80% mass ratio and already existing Raptor engines, that has a fixed and known delta-V budget which is wholly inadequate for the described LEO-Moon-LEO mission, by about half. Look at it this way:
The standar Starship that will be used for dear.Moon has enough delta-V to liftoff from Earth and, without refueling, push itself through TLI, follow a free return trajectory, aerobrake through Earth’s atmosphere, and land using the fuel in its header tanks.
When fully refueled in LEO, that same Starship could push itself through trans-Mars injection, aerobrake through Mar’s atmosphere, and land using the fuel in its header tanks. It cannot return to Earth without being fully refueled on the surface of Mars using fuel manufactured on Mars, That’s the actual plan.
That Starship, fully refuelled in LEO, cannot fly to the Moon, land, and take off again. To do so, it has to be refueled a second time in a highly eliptical high Earth orbit. Then it can land, takeoff, go through trans-Earth injection, aerobrake through the Earth’s atmosphere, and land using the fuel in its header tanks.
The HLS Starship cannot aerobrake, because it’s heat shield and aerosurfaces have been deleted. Fully fuelled in LEO, it can fly to the Moon, land, then take off and put itself in orbit around the Moon, where it can offload its crew to an Orion. That’s the actual plan. Secondarily, it can drop off payload on the Moon and then reach Gateway in near-rectilear halo orbit. That’s also the plan. This version can be refueled and resupplied in cislunar space, and reused some number of times. That’s not the plan yet.
These facts are easily looked up, and the math is not too difficult. Start by looking up “delta-v budget.”
Musk has hinted that HLS may be able to get buy with only 600 tons of fuel in LEO and still do the described mission. That would mean shrinking it to about half size of course, by making it 25 meters tall instead of 50 (but still 9 meters in diameter). What does that say? NASA has specified 4 crew, permanently. A half-size HLS Starship is still more than big enough.
I crunched lots of numbers on a lunar Starship a year or so ago. Refueling in GTO lets it get to the moon with lots of payload, but a refueling Starship can’t deliver a significant amount of fuel to a GTO orbit. It arrives in LEO with such a low fuel fraction that it can barely get to GTO and back to Earth with no payload at all.
My conclusion for the transportation pipeline problem was that Starship is doing too much of the work of getting to LEO compared to Super Heavy Booster 1A ver1.0 tranche 1. It needs a bigger booster that supplies more of the launch’s delta V, but a RTLS flight profile, plus higher re-entry heating, may preclude the operational feasibility of such a booster.
Going to three stages adds complexity, especially to operations, and still leaves the problem of a 2nd stage that faces high re-entry heating and distant landing zones, or the expense of throwing away an expendable second stage.
It may make more sense to use a lot of launches with an extremely cheap launch system than use fewer launches with a more efficient but expensive system.
However, given the speed at which SpaceX can design and build boosters, right-sizing things based on operational experience should be quite easy for them. If they need a bigger booster they’ll just build one.
The main argument against all that is, Starship is squarely aimed at Mars and optimized for it. The Moon is in some sense a distraction, though I’m happy to watch the iterations of lunar Starship. It’ll be interesting if there winds up being a Stubby Starship for it.
Secondarily, a HyperHeavy booster with a fully reusable second stage would just be a SuperStarship with a cargo hold big enough to carry Starship Original Edition.
I don’t think any of that’s necessary or likely. I still expect an oversized NautilusX-like interplanetary cruiser that uses a Starship-like landing craft to emerge ca. 2040.
Lunar Starship, from what I can be see, is mass-optimized via deletion of the aerosurfaces, drive mechanisms thereof, and the heat shield. I’ll also further speculate that it’ll save some mass via having a far smaller solar array and radiator array than the Mars version. One way it’ll have extra mass is the landing thrusters.
So, if Lunar Starship is lighter, it should have more delta/v potential than the Mars version. The big question is, how much? Per Musk, the Mars version, fully loaded, should have a 6.9 KPS delta/v.
So, what’s the actual Delta/V budget for a Lunar Starship mission from LEO? I’ll do this by steps. LEO to Geosynchronous Transfer Orbit(GTO being a high energy elliptical orbit) 2.5 KPS. The mass-optimized way to do that is refuel both Lunar Starship and a tanker version in LEO (so you’re not pushing so many Starship dry masses though 2.5 KPS) and refuel the Lunar Starship, once, in GTO (The remaining prop after the GTO burn in both Lunar Starship and the tanker would be enough to fully fuel Lunar Starship in GTO). So, start out with a fully fueled Lunar Starship in GTO. To get to Low Lunar Orbit, you need 4kps. From there, it’s 1.6 kps to the lunar surface (for touchdown; lithobraking would be easier on the delta/v budget, but hard on the astronauts and cargo). So, you’ve used up 4.6 KPS of your fully-fueled 6.9 KPS (Which is for the Mars Starship, the Lunar Starship should have more than that.) That leaves
2.3 KPS remaining on the lunar surface. To get back to LLO, you use 1.6 of that, leaving .7 KPS.
Can you get back to low earth orbit from low lunar orbit with .7KPS in the tank? Well, yes, theoretically; you do a .7 KPs burn for the Earth C3 point. From there, you are on essentially an almost free-fall trajectory towards Earth – roughly an eliptical orbit, with LEO at one end, and almost lunar distance at the other end.
Then, to circularize in LEO, you aerobrake. Several of our Mars probes used this method to enter circular Martian orbit, and they had deployed solar arrays and no heat shield. A Lunar Starship would be a little more capable than that, though you’d still need multiple passes to circularize in LEO.
Did I include any margins (for safety, inefficiencies, prop outgassing, etc etc) at all? No, because I don’t know the actual Delta/v capacity of a fully fueled lunar Starship, so I’m using what the Mars version needs, and Musk says it will have. However, even moderate mass savings should supply that margin.
Did I get something wrong?
Yes, the problem is LSS can’t aerobrake because the heat shield was deleted, so you need to brun fuel to brake propulsively into LEO. Aerocapture? In theory, but then you’re making multiple passes through the Van Allen’s. Also, the GTO tanker will not be able to fully refuel LSS in GTO. On the other hand, the process you desribe is how a pre-NASA standard Starship lunar landing mission would go. The top off in GTO to allow trans-Earth injection, and then aerobraking to the surface of the Earth with full header tanks for landing. I think the current LSS is optimized to go from LEO to NRHO to lunar surface and then back to NRHO per NASA requirements. And they did win the contract, after all.
One other thing about aerobraking: the scale height of Mars atmosphere is considerably higher than Earths, so it;s much better for aerocapture and the orbit changes with saw with Mars orbiters. Musk has lately been hinting that Starship will need one aerocapture pass before full Earth reentry on return from Mars. But that’s with a heat shield, so only limited by deceleration force and heating.
Yeah.
Lunar surface with rocket fuel is like LEO with rocket fuel- but better.
Always mentioned is LEO to Mars or whatever in terms of delta-v – generally assumes it’s half empty.
And also with vehicles which have get thru hell, going thru earth’s atmosphere.
With lunar surface, the structure could withstand less than 1 gee.
1/2 gee rocket acceleration has insignificant gravity loss {around 100 m/s} -also similar from Mars surface low acceleration and about 500 m/s of gravity loss. And can lower it by doubling lunar acceleration.
Anyhow, tend to think, from lunar surface one swings by Earth, but what about just going from lunar surface to anywhere?
And from Mars surface to lunar surface. Or high Mars orbit to lunar surface, same as Lunar surface to Mars high orbit. It seems same trajectory in which low impact space rocks hit the lunar surface.
Or with lunar surface to high Venus orbit- would you go to Venus from New Moon and Full Moon to Mars. Or from High Earth [or any earth/moon orbit] use lunar gravity in same way?
Also one use first stages which are lunar reusable from lunar surface, takeoff at 1 gee, and second stage is 1/4 gee max thrust.
Same with Mars.
Much I love SpaceX/Starship and detest SLS/Orion, this video is a good example of why SpaceX supported get called “fanbois.”
I’m sort of in this camp: SLS is a bureaucratic black-hole that will produce a barely functional rocket. I’ll give it even odds for blowing up on the pad.
But that doesn’t mean that their competition gets to magically violate the rocket equation. I actually love SpaceX for running an actual rocket program. Their program of trial and error is a far better way of developing actual hardware by building actual hardware than having it spring straight out of platonic space like Athena from the brows of Zeuss, only in a billion gigabyte powerpoint deck.
But they still don’t get to violate the rocket equation. Space travel is hard. I wonder how they’ll manage refueling on the lunar surface: Lunar dust is a nightmare to work wtih mechanically as any kind of raw material. And the ice in the south poles is still tenuously established, and might not be plentiful enough to be blowing away as reaction mass.
You misunderstood. No one is planning to refuel Starship on the lunar surface. It will refuel in cislunar space from Earth-launched tankers and freighters. So each lunar landing will require the launch of two lunar cargo ships (one freighter and one tanker) plus some number of LEO tankers (probably eight). That’s ten launches for each landing, but at a total cost only a fraction of SLS.
Fine metal mesh with Teflon coating??
Kind of like air bags but designed for a lunar for launch pad.
Or carbon fiber, but maybe any kind oxygen rich fuel would incinerate it.
Spray paint?
Hot Liquid Aluminum spray “paint”
Lots gallons fast.
How about adding rocket fuel additive?
I’m trying to distil your comments.
Your issue is that a lunar starship needs to be refueled and that if it isn’t refueled, that it is pointless to do anything with the spent lunar Starship?
Not sure who this is directed at, but if me, no. The point is, refueling and reusing it leverages more lunar exploration than using it as a hab on the lunar surface, other than maybe the first few missions. I am opposed to the idea of tipping the landers over to use as habs. It will just at marginally useful complexity at considerable expense. Some of the cargo starships will be abandoned on Mars to, in the early days, mainly used as holding tanks for ISRU-produced methalox, and as housings for ISRU equipment that doesn’t need to be deployed to the surface.
One of the ideas I favor for lunar exploration, as an alternative to a static “moonbase” is what I’ve sometimes called Lunar Surface Rendezvous. You send a cargo ship to the Moon that deploys a large rover. Then a crewed ship comes down and drops off the rover crew. Then the rover drives off, and some time later (months) a second crew lander comes down and swaps in a replacement crew, alongs with some more supplies. You could do that several times before the rover would wear out, and explore huge amounts of Moon. If need be, you could follow the terminator, and not have to overnight.
More proof that Spacex is running a rocket program, and Blue Origin and NASA are running a P.R. program.
Scott Adam would say that Musk doing a much cheaper PR program
for everything he does, and that Elon is a friggin genius.
Huge amount PR, just doing PR the right way.
Something NASA has failed miserably at for decades, according to Keith Cowing.
And amounts to having crown jewels, but it is a perfect secret, due to the endlessly overpaid morons.
What’s the deal with that image of a tall lunar landing craft touching down on those bitty legs? Wasn’t that the “knock” on the original Direct Ascent versions of Apollo, the technical difficulty of landing something the size and shape of an Atlas stage without having it tip?
Is the assumption that there is some manner of a landing pad prepared ahead of time on the Moon?
The Moon doesn’t have crosswinds, but unimproved lunar surface can have considerable slope to it?
The video is a collection of iobsolete images. The current HLS is the one with the big, triangular, permanently deployed (“fixed”) landing gear. That’s part of my problem with it.
Hmm, I wonder if the engineers at SpaceX have given any thought to those issues.
I always hark back to the many people who asserted Falcon 9 would not work because, “Musk will find out that Merlin will not work when there are 9 engines pluming.” These are the same people who later claimed the price of Falcon would have to go up, or else Musk must be “dumping.” Which wound up with the EU making that legal claim, only to be shown the secret facts, and back down at once. If Musk said he had a working FTL drive, I’d recall he already told us he was a shipwrecked alien advancing Earth’s technology so he could get home.
…And you wonder why SpaceX has fanbois?
More like I’m wondering why there aren’t more of them. If Musk had come along when I was a teen, I’d’ve been trying to convince my sisters to have his children…
But what would the reaction be, if Spacex lands a civilian on the Moon, before NASA sends any astronauts to the Moon. Say Musk sends 11 people to the Moon. A billionaire, and 10 of his friends. Or maybe company employees for a mining company. What would be the reaction from congress be? What would the reaction from NASA be?
How much coverage would this be for the news media? Would we see several hours of news broadcast from the Moon, like the Apollo 11 Moon landing? And what will tax payers say about spending $ billions on a rocket, when a private company is doing it cheaper?
This might be a great science fiction story. Say a short story for Analog, or Asimov’s.
Or maybe company employees for a mining company. What would be the reaction from congress be?
A man with no ethics who’s attempting to spread Global Warming on the Moon.
How Dare You!
I’d’ve been trying to convince my sisters to have his children…
Yes, then we’d have kids named F101Voodoo, F4GWildWeasel, A10Warthog and of course C97JSuperGuppy!
In order for SpaceX to land people on the Moon before NASA, it would have to have an FAA launch license. If Musk did it without the license, he’d go to prison. If he did it from another country, he’d wind up in Guantanamo.
Some people take more convincing than others.
“Let’s be very honest. We don’t have a commercially available heavy-lift vehicle. The Falcon 9 Heavy may some day come about. It’s on the drawing board right now. SLS is real.” — Charles Bolden, 2014
“SLS will go away. It could go away during a Biden administration or a next Trump administration… because at some point commercial entities are going to catch up. They are really going to build a heavy lift launch vehicle sort of like SLS that they will be able to fly for a much cheaper price than NASA can do SLS. That’s just the way it works.” — Charles Bolden, 2019
The genius of Starship is in its simplicity and flexibility. The definition of Starship is, a stainless steel tube with three bulkheads and a nosecone. The tube is made from a stack of standardized rings. Everything else (heat shield, engines, flaperons, etc.) is fitments. SuperHeavy is a Starship with the nosecone left off and more rings on the stack. In theory, you could build a space tugboat with four rings and three bulkheads, outfitted with some plumbing, an engine, hot gas thrusters, a battery, and some electronics.
It’s like he’s built a shipyard that can weld-up pretty much anything he thinks up in six or so months, perhaps less. They’ve got the engines pretty much nailed down, along with almost all the critical systems. He can change the diameter just by using different rings and building a different launch base. He’s already brought up the idea of doubling the rocket’s diameter, which if you count the upper-stage mass, would be like launching two-ISS stations per launch.
If NASA was on the ball, they’d be making all future plans based on the new capabilities Starship and its offspring bring to the table, in terms of a one-hundred fold reduction in cost to orbit, a massive increase in payload size and weight, and extremely high flight rates. At the very least, they should be dreaming up a LEO space station for the Starship era, with artificial gravity and some areas with radiation shielding.
Regarding cislunar refueling, I’ve seen calculations that suggest the fuel cost for landing landing from Gateway is approximately the same as a one way trip from Gateway to LEO. Gateway’s location is to accommodate the limitations of SLS and Orion, so without those, LLO is not out of the question (though this has its own issues). I think would be just as easy to do the refit in cislunar space as in LEO, so there’s no special reason to bring LSS home between landings. On the other hand, a Starship based translunar shuttle would be cheaper to build than LSS and could also be based in LEO. This starts to add up to a translunar ecology similar to what was orginally called the Space Transportation System (ground to LEO Shuttle, LEO to LLO nuclear shuttle, LLO to Lunar Surface Shuttle, all servicing a moonbase and molabs on the Moon). I’d’ve liked to see it in the 1970s, but will be happy to see it now.
Hmm. I can’t help but think that for a LLO to Surface Shuttle why not base it on GH2 and GOX? Could you super-compress and densify as gases w/o the need to liquefy? Then you could at least take advantage of any electrolytic-ally separated water found on the moon for the moon closest operations and not have to ship propellant all the way from Earth. A radical departure from Starship in the propulsion area, maybe not so much in others? A hand-wave I know. For me to work the math would take 10x longer than the other folks here.
Even easier I just realized. Use nuclear thermal for LLO/Lunar Surface shuttle and possibly LLO to LEO stages. Then you don’t even need to separate the liquid water. Wonder what it’d take to get Elon to consider a NTR?
NTR has the same problem as anything else nuclear. You think FAA is a pain, try the the DoE and the NRC.
SpaceX makes engines fueled by hydrazine, kerosene, and methane. It seems likely if Musk put through a work order for a hydrogen engines tonight, the prototype would be on a test stand in Macgregor in just a few months.
Moon Fact Sheet
Escape velocity (km/s) 2.38 km/sec vs Earth’s 11.2 km/sec
https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
2.38 km/sec = 5,312 mph and 11.2 = 24,998 mph
The moon has very little gravity loss in terms of the Moon’s
mass {the Sun’s gravity loss is difference matter or at Earth’s orbital
distance the Sun’s escape velocity is 42.1 km/sec. Or wiki:
“On Earth; Earth’s gravity 11.186 km/sec
At Earth The Sun’s gravity 42.1 km/sec to escape solar system: 16.6 ”
[[“In this table, the left-hand half gives the escape velocity from the visible surface (which may be gaseous as with Jupiter for example), relative to the centre of the planet or moon (that is, not relative to its moving surface). In the right-hand half, Ve refers to the speed relative to the central body (for example the sun), whereas Vte is the speed (at the visible surface of the smaller body) relative to the smaller body (planet or moon).”]]
https://en.wikipedia.org/wiki/Escape_velocity
Right-hand:
At the Moon: The Earth’s gravity 1.4 km {{leaving earth gravity well] and 2.42 km {{ escaping Moon relative to earth/moon gravity- I would say such as going to opposite side from Earth/Moon to L-3 not vaguely effected by Moon’s gravity- but not escaping the sun’s gravity well. Though since going about 30 km/sec at 1 AU orbit around Sun, with hohmann one can add about 12.1 km to 30 km velocity to get solar escape of 42.1 km/sec.
Of course using gravity assists one can leave solar system with less
delta-v. And delta-v given by chemical rocket {or any rocket} is improved by Oberth effect. Or if chemical rocket would give a total 12 km/sec, it gives more if rocket engine is traveling at faster velocity. Or these numbers are related sudden acceleration [cannon] or sudden deceleration {hitting a wall, atmosphere or rocky surface}.
Anyhow. So the 2.42 km/sec number is related to about slowest impact velocity space rock could have on lunar surface. Add a bit and space rock could come Mars distance- so like, about 3 km/sec
though a space rock {coming from anywhere can also be less impact than 2.42 km/sec. Or something like, 1.4 km/sec is lowest possible lunar impact velocity from a space rock.
–William Barton
November 14, 2021 At 7:11 AM
In order for SpaceX to land people on the Moon before NASA, it would have to have an FAA launch license. If Musk did it without the license, he’d go to prison. If he did it from another country, he’d wind up in Guantanamo.–
Maybe he could sell starship to the Space Force.
Or maybe the Canadian and/or UK space agency wants to go to the Moon.
But that’s a bit silly. He should instead but artificial gravity station in LEO using Falcon 9.
Be first to make an artificial gravity station.
This largely about PR, btw.
Sure it’s practical or needed to have human settlements on Mars.
But it’s cheap and it’s fast- but it’s important now, because it’s low cost PR thing.
I keep saying, an artifial gravity station won’t be cheap. It will cost more than setting up a permanent base on Mars. And what PR? No one cares except a very few enthusiasts, or will even know what you’re talking about. Mars looms somewhat large in the public imagination. “Space wheels” don’t.
“I keep saying, an artificial gravity station won’t be cheap.”
That because you talk of wheels, and not of sticks.
If artificial gravity is done with stick {a tall cylinder}
it’s a lot cheaper.
So, put 20 meter high cylinder on top of falcon 9 stage [which
less than 20 meter in length] and 20 meter is same diameter {12 feet] as falcon 9 stage is.
There are details. But basically you have 20 meter radius to spin and/or one attach with cable/rope a dragon to it {giving a larger radius].
20 meter radius might be too short of radius. But see if it is too short, if too short, use rope and dragon capsule to find the right radius.
NASA trying to see if one can adjust to very short radius- and this is much larger radius.
In one sense, you’re completely wrong about this. Cost correlates with size, not architecture, so a “stick” that can host hundreds or thousands of people for long periods of time is going to cost in the same ballpark as a wheel or cylinder the same size. A rope with two Dragons on the end isn’t an artificial gravity “space station,” it’s a waste of money joke.
Another point, often overlooked is, free axis spinning objects other than spheres are unstable. So sticks, wheels, and cylinder are going to wobble, only adding to things like docking problems for visitors. O’Neill knew this, which is why his space colonies were counter rotating cycliders connected by bearings at the ends. A practical AG space station would essentially be a 3-axis stabilized core with counter-rotating AG habitats (wheels or cylinder, doesn’t matter, but wheels more likely) mounted on bearings. The technology for such bearings was mastered in the 20th century (e.g. the Galileo probe). Cost? Scaled to size. The original NautilusX design was expected to cost $3.8bln 15+ years ago. Now? Probably twice that. Scaling it up a thousand times (for 6,000 crew instead of 6) would not cost a thousand times as much, but maybe a hundred times (so $380bln at a guess)?
There are no “cheap” AG space stations, andf two cans on the ends of a cable has long ago been tested (Gemini + Agena) in the 1960s. Even if your Venus space station was the right idea, how small could it be? For a few hundred crew waiting for a ride? If it’s for 6 or 12, you’re not building a space faring civilization.
“In one sense, you’re completely wrong about this. Cost correlates with size, not architecture, so a “stick” that can host hundreds or thousands of people for long periods of time is going to cost in the same ballpark as a wheel or cylinder the same size.”
First, I am talking about testing. Testing in sense of, is some radius distance and say 1/3rd of artificial gravity making you dizzy. And if spend hour or so, can your brain “manage it”.
So the stick has floors, floors have different levels of artificial gravity. So, you on top floor, and 5 mins of dizzy
you don’t think it’s getting “better”. Meanwhile other are 3 floors down, and how they feeling after 5 mins. And what about the people on the lowest floor after 5 mins.
And way designed it, one could move water mass, from top floor to basement, this acts like brake or accelerator to spin. Or could start pretty slow with the rate of spin, pump water from top floor to basement {bring arms in to increase spin} and one test the effect, and crew instead leaving station, could go to lower floors {if that helps make them less dizzy]. If station can only make you too dizzy and can’t get use to it. Have long rope, attach to end, start at furthest distance, does it make crew in dragon capsule too dizzy and can’t get use to it?
After do this, you have some clues about how to make better artificial gravity space stations. And have not wasted a lot money making an expensive wheel.
“can host hundreds or thousands of people for long periods of time is going to cost in the same ballpark as a wheel or cylinder the same size.”
Well, with stick, but not this spend falcon second stage plus 20 meter cylinder, you can live at both ends.
And one made a stick have low mass structures, the structural strength depends gee load out at furthest radius.
So with falcon 9 + cylinder and dragon capsule with total mass of 9 tons, if capsule is given 1/3 of gee, the rope needs to strong enough for 3 tons. If rope attached to a starship which is 120 gross mass, rope attached to it need to be strong enough for 40 tons {though less because one having crew part at the top of starship getting the 1/3 gees]. With stick one could large mass in middle of it, which not get much gee, and not need much structural strength. So with wheel one is having a lot mass which is
at highest levels of gee load {require lots of structural strength from the spokes and also have lateral load of wheel itself. This can quickly get very massive.
So, rather than wheel holding 100,000 people, have 100 sticks with 1000 people. It should less mass of structure and in terms water [shielding and thermal control] one stick station could hold more water mass then 100,000 people wheel. Or a big sphere with ends of sticks going thru it and out north and south poles. People could spend
most of time in higher artificial gravity but spend say 1/8th of time in parts of stick with less gravity [or microgravity}. Most time being mostly sleeping and working. and shopping or entertainment could have less time in which one spends time- swimming, playing sports, watching sports, and whatever don’t have to be at the ends of stick.
As far as testing goes, it’s a proven concept using old techology. Even the Von Braun AG space station, at 250 meters diameter, is equivalent to a small suspension bridge. There’s simply no profound reason to build a small AG station in LEO anymore.
That said, I’ve always regretted the missed opportunities of this past generation, starting with the cancellation of the Centrifuge Accomodation Module in 2005. There it sits in Japan, gone to waste. Part of the run-up for the NautilusX project would have been an ISS centrifuge habitat test module. It would have been berthed to the forward end of ISS (so with PMA-2 moved to the foreward end of its non-rotating hub) to test deploymend, and functionality of its bearing structure. Suggested uses were crew quarters, but also it could have had a gravity-dependent hygiene facility (a camp toilet and shower, for instance) and a gravity dependent kitched (e.g., with a convection oven). It would have been too small for 1g, but one-third or one-sixth it could handle, so a living on the Moon or Mars simulator. But it didn’t happen. You’ll notice the above discussed AG facilities enhance the functionality of ISS, as well as test concepts and materials.
Maybe something like that can be added ti the Axiom Station, or a larger one for Orbital Reef. I do think Axiom will be the next US LEO station, though I have a hard time believing in anything involving Blue Origin after this year’s shenanigans.