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We have mentioned a reusable Lander much but we haven’t really discussed it thoroughly. I find it hard to see why a reusable Lander should be that different then the disposable one. All that will be required is the replacement of the methane engines by reusable ones. I would think the development cost should be quite minimal. Think about it. The moon has no atmosphere so there is know heat shield to worry about ware. The number of mechanical parts is minimal (the landing legs) and doesn’t go though that many mechanical cycles each launch. In my opinion as soon as there is a methane factory on the moon a reusable lunar Lander will be ready to go shortly after. The only question remaining is what to do with the extra payload capacity that is now available because the Lander no longer needs to be hauled to the moon.
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Design a cargo carrier that has the docking ring, release it from the manned crew CEV to allow them to dock with the LM on steriods and then release the CEV so that it can dock with the cargo container for refueling for landing and to brings its cargo to the surface.
Most engines can be used more than once if time on the engine and power output levels are kept reasonable.
Probably the descent stage of the LM on steriods is surficient to be coupled with the cargo also as another option if it had the electronics computer to control relaunch and rendevers as well.
So I sort of wonder why Nasa is going with a TSTO LM on steriods all over again.
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First off, why bother with a reuseable lander? The lander itself will only weigh probobly 5-6 tonnes with its fuel tanks empty, so of the entire 78MT (aprox) of payload placed in Lunar orbit by the current NASA plan, you save maybe 6-7%. Not much of a mass saver. The engines will probobly be RL-10 derived, since they have already been tested with Methane, and are pretty cheap (a million or two a pop). The landers' structure and fuel tanks won't be that expensive either, some millions of dollars. No heat shield, and probobly no solar panels/batteries either (burns Me/O2 boiloff). Stock CEV-derived guidence and attitude control... Overall, I can't see the lander costing more then $50-60M a pop or so.
As far as returning to orbit from the Lunar surface, a seperate and lighter acent vehicle has an obvious advantage over trying to return the entire vehicle to orbit. This is a big deal, since trying to return the whole vehicle to Lunar orbit will severely cut into the payload the astronauts can carry down with them. This payload is special, nessesarry, even precious because it dictates what you can and can't accomplish efficiently. Maximizing it makes all the difference between repeating Apollo, and actually getting things done.
It gets better...
You still have to bring the fuel for the lander all the way from Earth, so you will have to develop a means for transferring cryogenic fuel in zero gravity, something that hasn't ever been done before.
But the real biggie though is the duplication of hardware: in order to get the fuel to land/launch your reuseable Lunar lander to the Moon, you are going to have to send it up on the big SDV, right? But you can't just launch it "dumb," the EDS stage with the Lunar lander fuel and payload has to have tug functionality in order to get to the Moon! Power supplies, thrusters, computers, gyros, telemetry & command link to Earth, docking transponders, the whole nine yards!
The cost of this "tug" attachment for the EDS in order to carry the fuel and payload for the Lunar lander costs about as much as the Lunar lander does! And then you have to consider the development cost for TWO independant automated vehicles instead of one.
A reuseable lander that doesn't have access to Lunar LOX makes no sense.
Edit: Oh yeah, and the reuseable lander will need to be more complex to accomdate solar power and carry pretty big supplies of station-keeping fuel for extended storage in Lunar orbit.
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It is sort of funny to find a topic that goes with the current gateway station which toys with the idea....
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My prediction: Space X will beat Artemis to the Moon.
It is sort of funny to find a topic that goes with the current gateway station which toys with the idea....
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The blue lander does have a tight timeline for Nasa's landing on 2024 but its not without possibility.
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To the topic of reuseability for the moon we need to make fuel and contain the hydrogen of water to be ablke to do so. The traces of water at the solr pole in the deep crators need follow up by a mission to prove what content and where. Volatiles Investigating Polar Exploration Rover or VIPER,
NASA's VIPER rover will look for water ice on the Moon
It could land on the lunar south pole a couple of years before the 2024 crewed Artemis mission does.
The rover will roam several miles to find wet areas below the surface using an instrument called Neutron Spectrometer System. VIPER will be equipped with four science instruments to sample various soil environments, including a meter-long drill to be able to collect specimen from underneath the surface. Its other two instrument -- the Mass Spectrometer Observing Lunar Operations or MSolo and the Near InfraRed Volatiles Spectrometer System -- will then analyze the samples to figure out their composition and concentration of water ice or other resources we can potentially harness.
What, just a single meter....
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How difficult this is depends upon what you are trying to accomplish, and how complicated you intend the flights to be. Here's a bounding analysis.
Lunar circular orbit speed is about 1.68 km/s at low orbit altitudes, and surface lunar escape is about 2.38 km/s. The worst-case delta-vee to and from an Earth-moon transfer trajectory is about 0.8 km/s. There is no air drag loss, and the lunar gravity loss is crudely 0.165*5% = 0.83%. It takes worst case 3.29 km/s to depart LEO for the moon by that transfer trajectory.
If you want a reusable (meaning single-stage) lander to-and-from low lunar orbit, the two way delta-vee is 2(1.68 km/s)(1.0083) when factored for gravity losses. That's 3.388 km/s min delta-vee capability for the vehicle. At 330 sec Isp for vacuum engines operating on storable propellants, Vex ~ 3.236 km/s. Thus the required mass ratio is 2.849. The mass fraction of propellant in such a vehicle (relative to initial ignition mass) is then 0.649.
Now, if you believe that the inert mass fraction of a vehicle that has propellant tankage (1 count) landing legs (1 count), a small pressure cabin (half a count), and sufficient structural robustness to survive a long life (1 count) is 3.5*(.05) = 0.175, then its max payload fraction is 1 - .649 - .175 = .176. While somewhat low, it's not too bad, really. A 10 ton vehicle with 6.49 tons of propellant can fly 1.76 tons of payload two-ways to-and-from lunar orbit, if its dry empty mass is 1.75 tons.
If you are using higher-performing propellant, it gets even better. If there's water ice on the moon, you could be using hydrogen and oxygen as your propellant, with vacuum Isp nearer 460 sec. Vex ~ 4.511 km/s. Required mass ratio 2.119. Fuel fraction 0.528. At inert fraction 0.175, payload fraction is 0.297. In a 10 ton vehicle, that's 5.28 tons of propellant and 2.97 tons of payload, with a 1.75 ton dry unloaded mass.
Now, that orbit transport landing boat idea might serve rendezvousing with ships or a station around the moon. But if your rendezvous point is out at one of the Lagrange points somewhere, your delta vee is closer to lunar escape than orbit velocity. 2*2.38*(1.0083) = 4.513 km/s as factored for gravity loss. To do that single stage with storable propellants, required mass ratio is 4.032, much more challenging. That's a propellant fraction of 0.752, which with .175 inert fraction, leaves only 0.073 as payload fraction. Unattractive. 73 kg payload in a 10 ton vehicle.
If hydrogen-oxygen, this is mass ratio 2.719, propellant fraction 0.632, and for inert 0.175, payload fraction 0.193. Still not very attractive, which is why the Gateway station concept of NASA makes no sense at all for lunar exploration, unless it really is in low orbit about the moon! They don't want it in lunar orbit, because SLS block 1 and block 1B cannot effectively put it there. Block 2 could, but the way things are going, it will not ever be built.
I have not included any maneuver delta-vees for rendezvous in this, but they would hopefully be modest. YES, a two-way reusable single-stage lunar orbit landing boat CAN be built! For low lunar orbit.
GW
Last edited by GW Johnson (2019-10-27 10:17:15)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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with the numbers changing for the fuel engine match. Going with methane Lox and a raptor engine changes the numbers for payload and ship performance dry weight if I am understanding the GW reponse to can we do a reuseable lander with insitu manufacturing of fuels.
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The fuels for moon use are different than that of mars in that for mars we will be able to make methane as there is a source of carbon in the mars atmosphere but for the moon thats not something we can do unless we are counting on enough from crew cabin scrubbing of air over time to do for a source. That said what fuel can we make other than mono propellants from water....
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LOX- LH2 or HTP or some combination of these starting with only water. If there are suitable fuel options using silicon, aluminium or magnesium hydrides we could get much more dense fuel options as these elements are abundant, but I don't know whether they can be used in a hybrid rocket engine and whether scale would build up on the cooled engine surfaces.
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We will not be able to convert the lander for a new fuel type so its got to be what we would send it with in the first place. While Lox LH2 would be plausible its a waste of water that will be needed way more important for our being to be able to stay on the moon.
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Right Spacenut. The lander has to be designed to use the fuel which can be made at its destination, for its approach and landing, or to carry some kind of conversion kit or to carry a separate engine.
In all cases the oxidiser is likely to be LOX which can be extracted from regolith minerals, but could be peroxide which can be made from locally obtained ice.
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If we're using ice, then the fuel is probably going to be hydrogen. H2/H2O2 rockets don't perform very well, and if you're handling cryogens, you might as well use LOX.
Use what is abundant and build to last
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If you do that to many times then you will not have any water to drink....so after just a few then we still need to look at other sources for that water to make fuel with or try a different fuel...
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The underwhelming assumption everyone makes is that lunar water ice can be easily converted to both LOX and H2. This is a very high magnitude, energy intensive prospect. This isn't really a problem for aerospace engineers to tackle, but is a very difficult Chemical Engineering exercise. But--in my PROFESSIONAL, NOT SO HUMBLE OPINION, the difficulty of which is vastly underestimated. So far, we have lots of vaporware about the quantity of ice available, and lots of what GW decries: scientific assumptions.
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About all that we do know about lunar regolith is that we have plenty of oxygen that can be made use of once its liberated from it.
Solar concentrated light in a chamber can be used to free it up...
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A need for a new engine has AFRL And Blue Origin partner on test site for BE-7 lunar lander engine development
Planned work includes adding liquid hydrogen (LH2) and liquid oxygen (LOX) propellant capabilities, along with other facility upgrades.
The BE-7 engine is a new, high performance 10,000 pound-thrust dual-expander cycle engine for in-space applications, including Blue Origin's Blue Moon lunar lander. AFRL's early development of the F-1 engine in the 1950s that ultimately took humans to the moon on the Saturn V.
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