Lunar Shipyards - Interplanetary Shipbuilding Bonanza

kbd512 · 2023-04-09 16:36:34

Recon flights over the lunar surface seem to indicate that it contains far more Titanium and Iron than we once thought. It also has plenty of Aluminum, Calcium, Chromium, Magnesium, and Manganese, Molybdenum, and Silicon. Aluminum + Magnesium = 6061. Iron + Chromium + Manganese + Manganese = 4140 and 4340 (gun barrel / "ordnance" steel and crankshaft and aircraft tubing steel, respectively). There are Titanium concentrations as high as 10% in some places on the moon, and Iron concentrations as high as 25%. The desire exists to transport vast quantities of metals mined from Earth to fabricate ships in Low Earth Orbit, but then serious challenges await prospective Mars-bound pioneers in the form of Earth's deep gravity well and Van Allen Belt radiation. This seems to impose a practical limit on both the number of ships we can assemble and their tonnage, before the propellant requirements to depart for Mars and the radiation protection problem compound to create unsustainable launch services and propellant costs. Propellant transport costs immediately (as in, first flight to Mars) gobble up any cost savings by making the metal on Earth.

The ability to make 6061 Aluminum, 4140 and 4340 steel (some of the toughest steels in existence), plus HSLA (High Strength Low Alloy) steels like HY-80 and HY-100 (also incredibly tough), as well as maraging steels for applications requiring extreme toughness / hardness / yield strength, and Titanium for bolts / pins / engine mounts, makes the moon a ready-made shipyard. EBW (Electron Beam Welding), which would be difficult to impossible on Earth without a vacuum chamber, is easily accomplished in lunar orbit (a vacuum chamber of unlimited size), which is almost entirely free of contaminant gases like Oxygen and Nitrogen present in LEO. Laser welding is another possibility for thinner sheet steels, where the HAZ (Heat-Affected Zone) can be minimized. That said, the EBW process is spelled-out in detail that accounts for all factors affecting weld quality, whereas laser welding is not a process with the level of control associated with aerospace manufacturing.

Maraging Steel is two times harder than stainless steel and 85% harder than pure titanium. Maraging steel alloys are twice as hard as stainless steel and 35% stronger than the hardest titanium alloy. On the Rockwell Scale of Hardness, stainless steel is 23-26, titanium alloys 28-41 and Maraging Steel 52-55.

If we can commission a small mining operation on the surface of the moon, which produces Titanium and Iron metals for ship building, along with a mass driver to deliver those metals into orbit, then a significantly reduced propellant supply would be required. Presuming NASA's contractors can deliver reliable nuclear thermal rocket engines, then the propellant tonnage is cut in half again, when compared to what LOX/LH2 or LOX/LCH4 can provide. There should be no objections to lighting off a NTR from lunar orbit. NTR testing can be conducted on the lunar surface without environmental objections.

Perhaps we should also construct one-way ships that serve as the surface habitation modules on Mars. The colonists need places to live, but there are none on Mars at the present time. The upper stage of a rocket is also a poor substitute for a permanent habitation module. Dr. Zubrin's original spam can concept might be the correct type for colonization efforts, where the goal is not to return to Earth. That concept means we don't need to bring a ship back to Earth, which means no refueling.

Mars_B4_Moon · 2023-04-09 17:40:12

I think if they put large scale transport on the Moon perhaps the Shipyard and Train Station might be one large inter connected facility / company. It will be interesting how much technology like Nuclear power or 3d printing and artificial intelligence will add to a Moon base, I think a mass driver on the Moon is a great idea, using an already existing tunnel on the Moon would help with radiation shielding from Solar Flare when getting ready transport product to Mars and to begin shipping from inside a tunnel and manufacture and delivery a Lava Tube abnd then shoot the product to orbit would be a safer place to work, away from micrometeorite it would also regulate the environment for people or Robots and save from those extreme swings in the Moon's temperature.

How ridiculous would it be to launch a Spacecraft from a Train? The zero-length launch system or zero-length take-off system ZLL, ZLTO, ZEL, ZELLa method whereby jet fighters and attack aircraft could be near-vertically launched using rocket motors to rapidly gain speed and altitude.
'Different technologies to push a spacecraft down a long rail have been tested in several settings, including this Magnetic Levitation (MagLev) System evaluated at NASA's Marshall Space Flight Center.'
https://www.universetoday.com/73536/nas … the-stars/

NASA Considering Rail Gun Launch System to the Stars

Different to a catapult aircraft merchant ship, on Mars you might have a spacecraft launched from a merchant train?

and

A funny twiiter clip
'¡Compadre!'
https://twitter.com/GuillermoBGR/status … 6546281477

Kbd512,
Here were some recent ish articles which might be on interest

'NASA Seeks Student Ideas for Extracting, Forging Metal on the Moon'
https://www.nasa.gov/feature/nasa-seeks … n-the-moon
China Plans to Build Nuclear-Powered Moon Base Within Six Years (paywall)
https://www.bloomberg.com/news/articles … -six-years
Here’s how we could mine the moon for rocket fuel
https://www.technologyreview.com/2020/0 … ocket-fuel
Observations of Titanium, Aluminum and Magnesium in the Lunar Exosphere by LADEE UVS
https://ntrs.nasa.gov/citations/20160003680

The Jules Verne 'space-gun' seems a little fictional?
a space gun has never been successfully used to launch an object into orbit or out of Earth's gravitational pull, Space tethers on the Moon would be different to Space Elevators long cables which can be used for propulsion, momentum exchange, stabilization and attitude control, rocket sled launch would be an eastward pointing rail or track that goes up the side of a mountain for single stage to orbit, StarTram is a proposed space launch system and SpinLaunch is a current spaceflight technology development company working on mass accelerator.

https://web.archive.org/web/20110409183 … PUR-19.pdf

https://web.archive.org/web/20040227183 … well_2.pdf

Almost all of the technology components needed for StarTram
now exist in commercial form, including Maglev superconductors, tethers, cryogenic insulation and refrigerators,
vacuum systems, etc

There has also been discussion of when you build material or manufacture vehicles it will lead to electric rails launching product into orbit, acceleration would need to be controlled as it would pulverize most manufactured objects and certainly people but it could launch hard durable product and lead to development of the Lunar economy, you might have Moonbase and Mass drivers or the Moon / Mars circular accelerator concept. I think one of the big events and issues will be what kind of nuclear power or manufacturing will be available on the Moon, the Low lunar orbit (LLO) are orbits below 100 km (62 mi) altitude yet suffer from gravitational perturbation effects that make most unstable. The Moon could be far more difficult than Mars but maybe it can be a stepping stone. It does however make sense that if mankind is going out to Cislunar space and beyond and manufactured material and product is going first launched from the Lunar facility not Earth, Low tech products to be delivered to Mars that it would be launched from the Moon instead of Earth, perhaps a payload would need its small ion engines to adjust its trajectory, a linear motor idea might work better a type of maglev train, but without a speed limit, perhaps the bulk of a station could be built on the Moon maybe on Mars a Ground effect train. On Earth Japan, France, China and South Korea have already set impressive speed records for passenger trains, the Lunar surface perhaps a Launch loop would be a maglev system for launching to orbit or escape velocity, Elon Musk's vision of a modern Hyperloop is project based on the vactrain concept first appearance in 1799 I think a large part of the ships could be produced on the Moon and then launched by rail into space, it also does not need to be on the surface and could exit a tunnel shooting off into orbit at the last moment while make use of already existing long Caves or Lava Tubes on the Moon.

There may also be some hybird system a Rocket or Ship launched from a Moon-Train, what type of Train could Mars have? In 1960s the New York Central Railroad (NYCR) used a jet on a train, RT-23 Molodets NATO reporting name: SS-24 Scalpel were nuclear missiles hidden inside rail cars, it was a cold-launched, three-stage, solid-fueled intercontinental ballistic missile, also similar to the NYCR jet on a train researchers in the USSR developed the High-speed Laboratory Railcar (SVL) turbojet train, Armed Forces of Ukraine inherited some of this tech after the fall of the USSR but I believe it was broken up and most was put into a museum none existed before the current Russia invasion, in the 1980s the USA had the Peacekeeper Rail Garrison was a railcar-launched ICBM that was developed by the United States Air Force. For shipping of civilian commercial product from the Moon and Mars maybe a mix of different systems will be used and maybe even the Train itself would not need to be launched to orbit, it would be a rocket/spaceship/station carrier just as Aircraft on Earth are launched from Ships in the Sea or Carriers.

Last edited by Mars_B4_Moon (2023-04-09 18:20:56)

RobertDyck · 2023-04-10 12:53:06

Interesting idea. I had posted the idea of mining metal asteroids for iron, nickel, and precious metals. Transport precious metals to Earth for profit, keep iron and nickel in space for construction. The best way to process a metal asteroid is with the Mond process, which uses carbon monoxide. There is no carbon on a metal asteroid, that will have to be transported from somewhere else. Initially from Earth, but eventually a carbonaceous chondrite asteroid ('C' type) will be harvested for water ice, carbon dioxide ice, tar and other volatiles. The issue was chrome. The best way to transport precious metals down to Earth is an aeroshell made at the asteroid with material from the asteroid itself. So the aeroshell never returns to space, it's one-way. The best alloy for an aeroshell is Inconel 617, identified by NASA many years ago. That's primarily nickel-chrome with a little cobalt, molybdenum, aluminum, and carbon. Cobalt is the third most abundant metal on a metal asteroid, and carbon is required to process. Aluminum is a tiny quantity, enough that it should be present in sufficient quantity on a metal asteroid. That leaves chromium and molybdenum. There is some molybdenum on a metal asteroid, hopefully enough, but chrome is an issue. Could we get chromium from the Moon?

This 2-page PDF document by NASA lists Significant Lunar Minerals. Here's the table from that...

So chromium is available as mineral chromite in a group of minerals called spinel. The table says abundance is "minor". Is chromite concentrated enough on the Moon to be worth mining?

RobertDyck · 2023-04-10 12:56:40

kbd512 wrote:

EBW (Electron Beam Welding), which would be difficult to impossible on Earth without a vacuum chamber, is easily accomplished in lunar orbit (a vacuum chamber of unlimited size), which is almost entirely free of contaminant gases like Oxygen and Nitrogen present in LEO. Laser welding is another possibility for thinner sheet steels, where the HAZ (Heat-Affected Zone) can be minimized. That said, the EBW process is spelled-out in detail that accounts for all factors affecting weld quality, whereas laser welding is not a process with the level of control associated with aerospace manufacturing.

I also posted about this. Electron Beam Welding was used to weld the body of F/A-18 Hornet fighter aircraft.

However, this is what the plasma window was invented for. Invented at the Brookhaven National Laboratory in 1995, a small vacuum chamber with an electron gun can create an electron beam. The issue is how to get the electron beam out without melting the wall of the vacuum chamber. Solution is a plasma window. It is made of plasma at least 1200°K which forms a viscous plasma able to hold up to 1.5 atmospheres of pressure against hard vacuum. The hotter the plasma gets, the better it works. So the e-beam shines through a small plasma window, allowing the e-beam to be held by a welder or arm of a robot. The work piece does not have to be in vacuum.

kbd512 · 2023-04-10 16:23:11

RobertDyck,

If the asteroids were very close to Earth, then going after them would be less of a problem. As for using a plasma window with EBW, if we weld in space then no such complications are present. A very hot plasma window very close to the work pieces means a larger HAZ with attendant weakening of the base metal and joint (loss of tempering).

RobertDyck · 2023-04-11 13:15:45

kbd512,
There are many Near Earth Asteroids (NEAs) in orbit about the Sun that are closer to Earth than Mars or Venus. Propellant to reach them is less than propellant required to land on the Moon and take off again. The reason is gravity; asteroids have such weak gravity than landing on one takes negligible propellant, and lifting off also takes negligible propellant. Remote mining technology already exists. After a mine cave-in, a number of companies developed remote mining. Vehicles with drills to place explosives, and loaders to "muck" the rubble after explosion are operated remotely from the surface. Video cameras on the vehicles, and radio control. A nickel mining company called Inco was developing a fully automated loader that did not require an operator. However, all those Canadian companies that worked on remote mining technology were bought by foreign interests. This automated mining technology can be adapted for asteroids. The Moon is 384,399 km from Earth (semi-major axis), and the speed of light in vacuum is 299,792.458 km/s so a radio signal takes 1.28 second to reach the Moon, and an equal time to return. A radio signal to an NEA could take 1 to 20 minutes each way, depending on it's position in orbit about the Sun. But with automated mining, that is practical.

Smelting is very much easier on a metal asteroid. All you need is 200°C at 1 atmosphere pressure with pure carbon monoxide to convert nickel into a vapour. Draw that vapour into a second chamber, heat is slightly more and the vapour decomposes into nickel metal and carbon monoxide gas. This is the Mond process. It also work with iron, but at higher temperatures. And with cobalt at still higher temperatures. These temperatures can be achieved with a parabolic mirror to concentrate sunlight. The ease of smelting is what makes them so attractive. Smelting an oxide ore requires much higher temperatures, a blast furnace has exit temperature of 1,510°C. A Bessemer operates at 1,700°C. This is the attraction of metal asteroids.

kbd512 · 2023-04-11 17:25:19

RobertDyck,

How difficult is it to go grab material from an asteroid vs grabbing it from the moon?

Also, nobody is talking about using much propellant to get back into orbit. We're talking about using a rail gun to launch metal and volatiles into orbit. Furthermore, people need to be present at any mine, regardless of any assertion to the contrary. How many people would be needed for this asteroid mine? Don't say "nobody", because no such "remotely operated" mines actually exist. All actual mining operations involve people, so how many?

You have a lot of Iron and Nickel on asteroids, but what about others metals?

To make HSLA steel, you also need Chromium, Manganese, and Molybdenum.

Where are those metals coming from?

RobertDyck · 2023-04-11 18:03:29

We've gone over this again and again. I posted composition of metal meteorites and claimed these are reasonable samples of Near Earth Objects. Lack of chromium is why we had a discussion of steels that don't include that.

Most importantly, yes I said autonomous operation. Expect a human would only be required in an emergency to repair something. Maintenance and simple repairs would be done autonomously. So zero people normally on the asteroid. I also said the steel rolling mill would be in Earth orbit, not the asteroid. Harvest material, do minimum processing, bring it back without hauling waste or slag.

Metal asteroids are made of the same material as metal meteorites. They're almost entirely solid metal, possibly with some small inclusions of rock. Most importantly, they aren't oxide ores, they're actually metal.

You didn't answer the key question about the Moon: how are you going to smelt ores? What's your heat source?

RobertDyck · 2023-04-11 18:52:19

Cigar Lake and McArthur River are uranium mines with 18% and 11% respectively. The mines are so rich that they form natural nuclear reactors. No miner can enter the mine due to high radiation. They couldn't be mined until remote mining was invented. No human enters the mine... ever.

kbd512 · 2023-04-11 18:56:05

RobertDyck,

The very first infographic on the page you provided a link to indicates that the Orano Uranium Mining Company has 470 employees.

What do all of those people do?

RobertDyck · 2023-04-11 21:07:03

kbd512 wrote:

RobertDyck,
The very first infographic on the page you provided a link to indicates that the Orano Uranium Mining Company has 470 employees.
What do all of those people do?

Remote mining means they operate the vehicles by remote control. The vehicles are not autonomous. Inco developed an autonomous loader. Many of the employees work in the ore processing facility. None actually enter the mine itself, because radiation is far too dangerous.

kbd512 · 2023-04-12 15:42:56

RobertDyck,

What's the signal lag time between where their employees are located and where the mine is located?

We don't send EOD to detonate bombs that a robot can disarm, either, but our EOD bubbas are only located a couple hundred yards away. This is a far-cry from someone on Earth trying to control a mining tool that could be on the other side of the Sun, relative to Earth.

RobertDyck · 2023-04-12 19:22:02

We need fully autonomous equipment on the asteroid. Like Spirit, Opportunity, Curiosity, and Perseverance. As I said, Inco was developing a fully autonomous loader for mining on Earth. Considering advances with Chat GPT, I don't see this as major problem. And remember, other side of the Sun is just 16 to 20 signal delay each way. Making decisions forajor issues shouldn't be a problem.

kbd512 · 2023-04-13 01:19:45

RobertDyck,

You're going to need people onsite to oversee the mining activities. There might not be anyone inside the mine itself, but someone will need to be nearby. That means they have to live out there, at the mining site, tens of millions of miles away from Earth. The reliability of all involved systems must be sufficient to live there, which is no different than living on Mars. At that point, why not simply go to Mars and start your mining operations there?

The entire reason for going to the moon is that it's very close to Earth relative to any other planetary body, it can teach us how to live and work on another planet, and the technology development has direct application to living on Mars.

RobertDyck · 2023-04-14 04:17:59

Nope. Those supervising can use video and high resolution images. Perhaps a drone with thrusters; it won't take much to lift off from an asteroid.

A mine on the Moon could be operated real time from Earth. Communication delay is less than 2 seconds each way. They would mine anorthite for aluminum, ilmenite for titanium, and chromite for chrome.

A mine on Mercury will require workers onsite. I'm hoping to find concentrated minerals in veins since that planet is so close to the Sun and experiences 88 days of sunlight followed by 88 days of night. The hot/cold cycles will hopefully have produced veins. At least from materials with mild melting points like gallium and indium.

kbd512 · 2023-04-14 05:38:21

RobertDyck,

When I see a solution wherein not one single person is onsite for a year or more, then remote mining is ready for prime time.

Calliban · 2023-04-14 09:12:53

A rocket sled is a viable option for launching raw materials from the lunar surface. The world speed record is 6400mph, which is somewhat higher than lunar escape velocity of 5300mph.
https://en.m.wikipedia.org/wiki/Rocket_sled

Low lunar orbit implies an orbital speed of ~1.5km/s, or 3360mph. So a lunar rocket sled capable of launching packages of mined ores into lunar orbit, does not stretch the state of the art. However, for this to work, the packages would need to carry a small rocket motor sufficient to lift their perogee above the lunar surface. They can then be collected in lunar orbit and transported to a refining facility at L5 or L4. The delta-V needed to do this is on the order of a few hundred m/s. So cold gas thrusters using stored liquid oxygen are a simple option for providing the thrust needed at apogee. The sleds would remain on the track and would rapidly decelerate after launching the package. Maybe we can propel them electromagnetically, or perhaps using a native propellant like LOX/Aluminium.

Even if mining is mostly automated or teleoperated, a human presence will definitely be needed on the surface. Equipment will need to be maintained and breakdowns will be common. Lunar dust is highly abrasive and electrostatic charge makes it sticky. So expect maintenance periods on anything with moving parts to be short. Vehicle wheels will need regular changes. This sort of maintenance needs to be carried out in pressurised garages, where people don't have to work through space suit gloves and they are protected from cosmic rays, temperature extremes and micrometeorites. I don't think we will be colonising the moon in the way we envisage colonising Mars. It is just too harsh. There is very little water, carbon, nitrogen, phosphorus, etc. It will never be a place where large numbers of people want to live. But it is very valuable as a mining colony.

One way of dealing with the problem of traversing Van Allen belts is to establish Earth-Lunar cyclers with eliptical orbits with perogee perhaps 500km above Earth atmosphere, and apogee just within or even past lunar orbit. These space stations could provide a way of traversing the distance between Earth and Moon in comfort, with good shielding against cosmic rays and Van Allen radiation. The expense of building them is mitigated by the fact that once established on their orbits, no additional propellant is needed.

In many ways, High Earth Orbit (HEO) is a more advantageous launch point for an interplanetary journey to Mars. An interplanetary spacecraft entering Earth orbit at lunar distance would be entering a weak gravity well, which reduces the propulsive effort needed to enter Earth orbit. A Starship could leave Mars with enough methane for high Earth orbit insertion and a return journey to Mars. Lunar derived oxygen could be provided in HEO and this represents the bulk of propellant mass. So lunar mining could ultimately eliminate the fuel needed from Earth to allow interplanetary transfers.

Last edited by Calliban (2023-04-14 09:28:22)

RobertDyck · 2023-04-14 12:28:54

kbd512 wrote:

RobertDyck,
When I see a solution wherein not one single person is onsite for a year or more, then remote mining is ready for prime time.

Everything in space requires new technology that has not been built before. Often it's technology that has been developed, but not implemented because there are other ways that can be done on Earth. Working in space requires completing technologies that have been left on a shelf for decades, or even a century. If you're not willing to develop anything new, then you don't have the right stuff for space.

kbd512 · 2023-04-14 15:36:51

Calliban,

I was thinking that we'd turn the area surrounding the rail gun battery into glass, and that most of what we're launching into orbit is metal and water. The US Navy's rail gun program can already launch an artillery shell into lunar orbit. We would need a nuclear reactor to supply the input power, and the barrel life is rather short- only 400 shots, but that's still 20t of steel at 50kg per projectile. We reduce the acceleration rate by doubling the length of the barrel (from 32ft to 64ft) and reduce the muzzle velocity (by about 500m/s), to achieve greater barrel life. This was not an option for the US Navy, but should have no ill-effects on a lunar rail gun.

The projectiles would use a base-bleed rocket motor for circularizing their orbits. After firing is complete, a tug would retrieve the metal, tow it to a smelter, melt it down into sheet or plate, and then we can begin using the materials for ship construction in a higher orbit than that used by the rail guns for materials delivery. This requires some electronics, but this is standard fare for artillery shells, to include the artillery shells experimented with in the rail gun, which included guided / steered projectiles.

We need HSLAs (HY-80 or HY-100), maraging steels (C250 / C300 / C350), Grade 5 Titanium alloys for bolts / pins / engine mounts, 6061-T6 and 7075-T6 Aluminum. I can't think of any hard requirement for 2024 off the top of my head, which requires Copper, but maybe we need some of that as well. We need CO2 for fire extinguishers, O2 for breathing, and H2O for drinking / cooking / cleaning / radiation shielding. That could be supplied as elemental Carbon and water for ease of transport (artillery shells loaded with powdered Carbon or liquid water). I think the N2 probably has to come from Earth, but maybe there's a source on the moon.

That means the only stuff coming from Earth is people and their personal effects, food, and LN2. RobertDyck also has a plan for making food aboard the ship, but maybe the chemical constituents for the food could also come from the moon. The solar wind does carry Nitrogen to the moon, so if we can devise a large enough collector, perhaps we can tap into the solar wind as our Nitrogen source. If we can do all of that, then very little is coming from Earth, perhaps only electronics and other high-technology items like nuclear reactors.

If people and technology items are the only things we need to source from Earth, then this entire endeavor becomes far more practical, and more resistant to prevailing economic forces on Earth. Establishing multiple almost-independent economies is how we're going to weather the crapstorm of idiotic economic ideas, energy / resource depletion, and military entanglements. I think the combination of those factors killed the Apollo Program. In the same way that the ISS has been a near-immortal program, a lunar base would be our first true "foothold" in space, and also a near-immortal program. A Mars settlement would be an application of the technology developed for the lunar mining colony. All the huffing and puffing from NASA about retiring risk would subside if we proved we could live and work on the moon for a few years. 10 years after the first successful Mars settlement, we could establish colonies anywhere in the solar system that our ships can take us. The idea will have been planted that we can go to live pretty much anywhere our technology allows. That means we will also have colonies on the moons of Jupiter, along with floating colonies on Venus, Saturn, Uranus, and Neptune. Neptune and Uranus can supply almost unlimited energy in the form of Hydrogen / Deuterium / Helium for fusion.

Calliban · 2023-04-16 16:52:47

It isn't clear to me exactly what the life limiting problem is with rail gun barrels. A muzzle velocity of 2km/s would be about twice the velocity of a rifle bullet. Is mechanical wear the problem, or is it plasma arc sputtering at the projectile base? Could we deal with the problem by having some sort of replacable insert into the barrel?

The mass driver, otherwise known as the coil gun, works slightly differently to the rail gun. The rail gun takes advantage of Fleming's left hand rule. The coil gun uses magnetic attraction between a projectile and the coil it passes through. The attraction can be electromagnetic, with the projectile containing an energised coil or alternatively, a ferromagnetic projectile can be drawn through coil segments. A plasma arc gun or a gas gun are both potential alternatives.

I agree that our ability to manufacture large ships in high earth orbit, would open the solar system to us. Gerard O'Neill described how mass drivers can be used as impulse engines with ISP up to 1000. I doubt that we will be colonising the Jovian satellites any time soon. The problem isn't so much radiation, but Jupiter's gravity well. Jupiter's escape velocity is almost 60km/s. Climbing down that gravity well and achieving a safe orbit of Ganymede, would take a lot of delta V. I just don't see it as being on the cards for quite a long time to come. The same is true for missions to the surface of Mercury. It is so deep in the sun's gravity that getting there woukd be very costly. But Mars, the Moon and the asteroids, could provide centuries of colonisation potential.

Getting back to the moon. The original O'Neil plan was to place a reciever for prjectiles at L1 or L2. This would essentially be a large bag. Magnetic field would trim the trajectory of projectiles as they exit the mass driver barrel. This would have allowed dumb projectiles to reach the receiver bag with very little residual velocity. The moon's gravity is lumpy. But a gravity map does not change once it is known. So the mass driver aim and muzzle velocity can be adjusted until shells arrive at the receiver with just sufficient speed.

Liquid nitrogen is an efficient means of transporting nitrogen. But given that we need hydrogen, carbon and nitrogen, why not transport urea or some other compound that is easily storable and contains all three elements? The hydrogen can be combined with lunar oxygen to make water. Carbon dioxide can be reduced to CO which provides a reducing agent for iron oxide.

Last edited by Calliban (2023-04-16 17:17:22)

kbd512 · 2023-04-16 18:47:50

Calliban,

The problem is barrel erosion, and muzzle erosion in particular. This is a problem for all hypervelocity cannons. The faster the projectile muzzle velocity, the faster the erosion rate. There's a reason why all artillery barrel life is represented in terms of "EFC", or "Effective Full Charge". Tank cannons have the same problem. Hypervelocity rifles also have this accelerated barrel bore and muzzle erosion rate problem. Any velocity near or over 1.5km/s significantly limits barrel life for all known steels. I'm unaware of any acceptable substitutes for HSLAs and high alloy ordnance steels. We have experimented with high-Cobalt alloys which better withstand elevated temperatures without weakening too greatly, but the hot gas quickly erodes those materials as well. Any steel beyond a HSLA or high-alloy ordnance steel is generally wasteful of alloying metals and any minor improvement in barrel life is greatly overshadowed by egregiously energy-intensive and expensive alloying metals production. The US Army had the opportunity to use high-Cobalt alloys in gun barrels, but elected to keep using 4150 or various stainless alloys like 416R. Too much cost, too little net benefit.

Is there a better way?

I would imagine that there has to be. We could make a trebuchet (not precisely the same as a pure gravity-powered device, more like a device powered by hydro-pneumatic force to catapult a projectile into orbit) or spin-launched projectiles. We don't need traditional aerodynamic projectile shapes or heat shielding, either. A round cannon ball is fine.

I don't see us going to the outer planets in the immediate future, either. The implication is that we can do that with the right ship / propulsion technology and affordable construction methods that fabricate the ships in micro-gravity environments. If we can perfect all this technology on the moon, then we can make ships elsewhere as well. The moon is a type of nearby proving ground every bit as harsh as any other environment where we could actually live.

Calliban · 2023-04-17 04:15:12

Interesting. A lunar launch gun obviously has different functional requirements to a naval gun. The question is how do we deliver a tonne of metal, ice and assorted oxides from the lunar surface to L5 at minimum cost. What is the cheapest way of doing this, when we account for delivery costs from Earth, power consumption, maintenance, etc. I do not have an answer. The rail gun would certainly work. But how much would it weigh? How much would its power supply weigh? Can we repair it on the moon? Can we make replacement parts on the moon? What are the alternatives to a rail gun? How do they compare in terms of weight and operational cost? All questions that would require a detailed engineering study. Beyond my capability unfortunately.

tahanson43206 · 2023-04-17 06:27:15

For Calliban re #22 and Dr. O'Neill's demonstration of mass driver ...

I was a member of the audience for a demonstration of the mass driver prototype in ca 1975-1985 ....

A Google search delivered a number of snippets about the project, including a picture.

https://www.google.com/search?q=name+of+student+who+helped+gerard+o'neill+demostrate+mass+driver+at+princeton+starts+with+horn&oq=name+of+student+who+helped+gerard+o'neill+demostrate+mass+driver+at+princeton+starts+with+horn&aqs=chrome.0.57.31321j0&sourceid=chrome&ie=UTF-8

What I remember from that long ago is that the bucket to hold ore was inside a spider web of a ring whose outer structure was material capable of being attracted by the magnetic field produced by the ring shaped accelerators.

If your rerun of the search string above is successful, you may be able to see an image of one of the demonstration mass drivers.

Another detail I remember from that long ago was the time taken to explain to the audience how dangerous the high voltage capacitors were. This detail is definitely badly faded with time, but I ** think ** the voltage in play might have been on the order of 6000.

In any case, when the switch was actuated, the bucket assembly moved through the accelerator ring and arrived at the soft catcher device with a satisfying thunk.

A detail of the history that I had forgotten is that O'Neill spent a year at MIT where he worked with Henry Kolm who was working on magnetic transport.

Update:
Here is a link to a paper written by Dr. O'Neill and an associate. The paper includes detail on how the components of the demonstration system became available.

https://arc.aiaa.org/doi/abs/10.2514/6. … nload=true

Update: Here is a paper by Henry Kolm in which he discusses a kilometer long launcher that could potentially achieve 10 km/s velocity for a 20 kg payload.

https://space.nss.org/l5-news-mass-driver-update/

(th)

kbd512 · 2023-04-17 22:57:04

Rheinmetall's 120mm L55 tank cannon fires a 10kg dart / projectile with 13.5MJ / 3.75kWh of muzzle energy, near 1,650m/s. A figure of 200kg of steel per kWh of steel flywheel energy storage is accepted as doable, so 3.75kWh per 10kg of projectile weight implies 750kg of flywheel weight. To launch 1,000kg projectiles, that implies a flywheel mass of 75t (375kWh). A 1,500m^2 solar array could provide the power, at 250W/m^2. I'm sure we'd need more energy and flywheel storage than that since flywheels have about 90% round-trip efficiency, but multiple Starships could deliver the required tonnage of machinery. We'd probably need 4 to 5 landings to deliver the equipment.

Calliban · 2023-04-18 06:19:46

Here is a copy of the Mass Driver 2 status report that isn't behind a paywall. I intend to read it later.
https://www.researchgate.net/publicatio … tus_Report

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