Methods to Lunar Orbit

Austin Stanley · 2006-08-15 00:48:31

With lots of talk about a possible resuable lunar surface assent module (LSAM), I thought it might be worth some time to identify the various methods we might use to get to lunar orbit.

#1. Conventional Rockets
The obvious plan, and the method NASA currently plans on using for their (no-reusable) LSAM. It's also the method used in Apollo, so it has relability and simplicty going for it.

The problem of course is that it isn't very reusable. Rocket fuel (no matter the type) must be exported to the moon, where it can be leveraged with lunar produced oxygen. Since great quantities of fuel are still needed, the savings here are sub-optimal.

#2. NTR
Nuclear Thermal Rockets are probably not pratical for lift-off from earth, they don't have the necessary thrust/weight ratio. However, the moon gravity is much lighter so it is probably practicle for a NTR to take off from there. Hydrogen would still have to be imported, but the advantage in ISP puts it ahead of chemical rockets. Lunar Oxygen might also be added during the early stages to increase thrust at the price of ISP.

#3. Lunar Dust Rockets
Most metals will burn/combust in the presence of pure oxygen in the right conditions. The classic example of this is the thermite reaction many of you may be familar with, but virtualy all pure metals will burn (oxidise really) in the right conditions with oxygen.

This fuel has the advantage of being virtualy free on the Lunar surface. Any extration operation that removes oxygen from the soil will leave behind pure metal which can be used along with that oxygen as a fuel source for the rocket. So if we mine oxygen in the rocks, we are bound to get lots of metal as well.

The problem is that while these reactions are very energetic, they are not very energetic per unit of mass, especialy when compared to conventional propellents. So the ISP sucks. This is less important if the fuel is free, but there is another big problem, it is unkown if an engine with a sufficent thrust/weight ratio could be constructed to lift off from the lunar surface. They won't work on earth certianly. In addition new engines would have to be designed to deal with this kind of fuel, which do not currently exist.

#4. Oxygen Fueled NTR of some sort.
Again, assuming oxygen can be obtained for virtualy free on the lunar surface, it might be used for fuel in a NTR. Again, oxygen is much heavier then hydrogen so the ISP will take a large hit (worse then conventional rockets), but again if the fuel is free this is less important. The big issue remains if a rocket with a practical thrust/weight ratio could be designed for moon-lift-of.

#5. Solar Thermal Rocket
The moon, lacking an atmosphere, gets much more solar energy then the earth, for much longer periods of time. This combined with it's light gravity might make it possible for a rocket powered by reflected light heating a gass to lift off. A Solar Thermal Rocket. It might be hydrogen or oxygen fueled, and might combust oxygen at the early stages for added thrust. This sort of rocket is similar to a NTR, but might offer improved thrust/weight ratios since it doesn't have to carry a heavy nuclear pile and shielding.

The problem is mainly in engineering. Creating an array of mirrors/lasers/whatever to focus light energy on the rocket during it's assent would be very difficult and would entail a fairly large ground presence. In addition after the rocket passed over the horizon they could no longer beam it energy, so there would have to be multiple stations, or it would only be good for a first stage.

#6. Rail gun
A rail gun is a difficult concept on earth, since you have that nasty thick atmosphere to deal with. On the moon it is no problem, a rail gun could easily hurl objects into orbit. Some orbital correction would be needed, but this is a minor issue. The big issue is the length of the rail-gun necessary to keep acceleration down to acceptable amounts. Several km probably, which requires intensive infastructure. Ultimatly it is the obvious answer to our problem.

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My solution:
I'm not sure that the most promising options (oxygen fuled rockets) will ever become possible on their own, but staging these rockets could provide some of the answer to our problem. For example, a rail-road track could be laid out for a lunar dust fired rocket which would thunder across the lunar plains at unheard of speeds (upwards of 1km/s maybe), then towards the end it would angle it up where it would be launched into space with considerable horizontal velocity and a secound stage could finish the job. This eleminates the thrust/weight problem for the first stage and makes it entirely recoverable.

cjchandler · 2006-08-15 04:48:58

How about a rotovator? (correct term?) With the lower gravity, orbit height, nd vacumn I read somewhere that it could be built using current materials like some sort of kelvlar rope. This has the added bonus if I understand it right of being able to throw things out at escape velocity from lunar orbit. It's basically a twirling rope or cable that is turning in the opposite direction that the middle of it is orbiting. It's also as long as orbital height so that for brief periods it appears to be stopped at the surface. Of course it will need to have a center base station and some sort of engine to make up for flinging cargo into orbit, but if the middle mass is large enough this could be a relitivy low thrust engine that runs continiously, like solar thermal.

RedStreak · 2006-08-15 20:39:43

Conventional rockets will likely be the only way to get from the Earth's surface to Lunar orbit for quite some time. However, if you're talking about launching from a base on the lunar surface...

Ok, conventional rockets for certain although there's the hydrogen import problem, lunar dust rockets if they can't be made for orbital still have the potential to be effective suborbital rockets for Lunar exploration, and add to that the rail gun launcher and those are the three ideas I see as being simultainioudly practical and foreseeable.

Nuclear propulsion could be applied to the Moon, but I fear finding and refining the uranium fuel rods nessicary will impose engineering, economical, political, and even security risks. Even if oxygen alone is the working propellant I doubt uranium will be easily obtained.

Solar thermal propulsion is only a slightly smaller joke than solar sails. Too much flimbsy hardware that needs to be deployed, angled, and even repaired versus the constant power from either fuel cells, solar cells, or nuclear power that's simply 'turned on'.

The lunar equivellant of a geosyncronus station could be constructed - the trick is the only connecting point would be the L2 Lagrange position since every other Lagrange position is too close to Earth or unstable. It would make an efficent spaceport for craft arriving or departing from Cislunar space, and it'd definetely aid in spreading LOX to the solar system from Luna as opposed to a network of tankers.

cjchandler · 2006-08-16 05:29:09

I mean a twirling cord in low lunar orbit to lift materials up or down to the moon's surface. At 150 km up orbiting and an average orbital speed of 1.022 km/s, then the tip speed of the cord would only have to be 1.022 km/s instead of the 7.8 km/s for earth. For 15 tons of payload and rope the rope would only have to overcome 104448 newtons of force, and that gives us a rope of kelvar with a crosssection of 0.00005 m2. therfore the rope would mass about 11 tons and you would have 4 tons of pay load per half turn.

dicktice · 2006-08-24 08:58:47

Austin Stanley: I especially liked your description: "... a rail-road track could be laid out for a lunar dust fired rocket which would thunder across the lunar plains at unheard of speeds ..." Sorry, it's unforgivable of me, but that got to my funny bone. Good post.

Austin Stanley · 2006-08-24 13:25:00

Austin Stanley: I especially liked your description: "... a rail-road track could be laid out for a lunar dust fired rocket which would thunder across the lunar plains at unheard of speeds ..." Sorry, it's unforgivable of me, but that got to my funny bone. Good post.

Thanks, but I am quite serious with this suggestion. As we all know, it is horizontal velocity which is most critical to a rocket reaching orbital velocity. On Earth is is simply impossible to achive these sorts of velocity in the low atmosphere, which makes the rocket-sled/train stage impossible. The moon obviously has no such limitation, so it may be very possible to launch a vessle via a rocket-sled/train. It could certianly be a first stage.

There are several possible problem I see with this approach, firstly the frictional limits on the speed. The moons escape velocity is some ~2.4km/s, which may be to fast for a rail-track to sustain without damage. In comparision, the fastest bullets travel at ~1.5km/s, though I am not sure if this is the upper limit of possible velocities. Trains and Cars obviously travel much slower. Friction from the track may also create a limit of the velocity the rocket can achive as well.

Another serious issue is the length of track necessary. A metal-oxygen rocket is likely to have a fairly poor thrust/weight ratio and lowsy ISP. In addition friction with the track/ground adds a signifigant amount of drag. All this adds up to the rocket sled stage likely being very large and slow to accelerate. Which means a fairly long, well graded track must be created for it to use. It might even have to be reinforced to handle the weight, though with the moons lower gravity this will be less of an issue then on earth. In any case, while the infastructure requirments are still substantialy less then a rail-gun or similar method of reaching orbit, they are still fairly substaintal.

The last problem I forsee stems from traveling at hyper-sonic velocities (though that term is not realy apt here) on the ground. Keeping control of the vehicle will be absolutly critical. Any disturbance could lead to a terrible accident, and at these velocities I fear that any slight jarring or disturbance could lead to such an accident.

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Nuclear propulsion could be applied to the Moon, but I fear finding and refining the uranium fuel rods nessicary will impose engineering, economical, political, and even security risks. Even if oxygen alone is the working propellant I doubt uranium will be easily obtained.

While Uranium is certianly present in the moon, I doubt we would need to go to the incredible expense of minning or refining it their to use a NTR. Depending upon the design of the NTR its radioactive core could be good for years to decades. A NTR generaly reacts at a higher rate (and uses more enriched fuel as well) then a conventioal reactor, but it is also functional for a DRASTICLY shorter period of time, a matter of hours each month at most. So I think importing the cores from Earth and deploying native fuel could be a praticle approach.

Solar thermal propulsion is only a slightly smaller joke than solar sails. Too much flimbsy hardware that needs to be deployed, angled, and even repaired versus the constant power from either fuel cells, solar cells, or nuclear power that's simply 'turned on'.

I certialy don't agree that solar-sails are a joke, they may prove to be an immensily pratical method of moving things about the solar system. They are slow, but they require no fuel (having an infinate) ISP and are reusable. Certianly in the inner system they are pretty much unbeatable.

As for Solar Thermal propulsion, I was refering to a system where the solar energy was "beamed" or reflected to the craft from a ground station, rather than carrying it's own mirrors. Only a secoundary reflector might be required. Alternatively Laser or Microwave power could be used, however these would require eletrical power generation, while reflected light is pretty much free, and mirrors could be light and cheep.

In space the Solar Thermal concept (carrying it's own mirrors this time) is viable, but inferior to NTR.

How about a rotovator? (correct term?) With the lower gravity, orbit height, nd vacumn I read somewhere that it could be built using current materials like some sort of kelvlar rope. This has the added bonus if I understand it right of being able to throw things out at escape velocity from lunar orbit. It's basically a twirling rope or cable that is turning in the opposite direction that the middle of it is orbiting. It's also as long as orbital height so that for brief periods it appears to be stopped at the surface. Of course it will need to have a center base station and some sort of engine to make up for flinging cargo into orbit, but if the middle mass is large enough this could be a relitivy low thrust engine that runs continiously, like solar thermal.

I certianly think a rotovator could work, but the infastructure requirement is again rather large. We could creat a conventional space elevator with modern materials as well (buckytubes not required), but it would be immense. The only issue I see with a rotovator is the problem if one of the cables hits the ground, which could cause a serious issue.

RedStreak · 2006-08-24 14:24:19

Solar thermal propulsion is only a slightly smaller joke than solar sails. Too much flimbsy hardware that needs to be deployed, angled, and even repaired versus the constant power from either fuel cells, solar cells, or nuclear power that's simply 'turned on'.
I certialy don't agree that solar-sails are a joke, they may prove to be an immensily pratical method of moving things about the solar system. They are slow, but they require no fuel (having an infinate) ISP and are reusable. Certianly in the inner system they are pretty much unbeatable.
As for Solar Thermal propulsion, I was refering to a system where the solar energy was "beamed" or reflected to the craft from a ground station, rather than carrying it's own mirrors. Only a secoundary reflector might be required. Alternatively Laser or Microwave power could be used, however these would require eletrical power generation, while reflected light is pretty much free, and mirrors could be light and cheep.
In space the Solar Thermal concept (carrying it's own mirrors this time) is viable, but inferior to NTR issue.

Ok two problems I immediately see with solar sails that would keep me from supporting it: extremely slow thrust - they make ion propulsion look like a Ferrari by comparison; a solar sail a few square kilometers in area makes a pretty fine target to a swarm of micrometeoroids - I don't care if kevlar struts support it I just can't trust a propulsion system thinner than the plastic in my garbage bags. I could see an unmanned interstellar spacecraft making some use of it, but it is, sadly, the epitome of impractical.

NASA or any space agency is not going to contruct ground stations for remote propulsion. Worse still, just like laser pen lights, a beam like that would blind any stray airplane or satellite in its path.

If a propulsion system takes more than 10 days to reach simply the Moon from LEO or vice versa I have to say it is "out of the race" for human passengers.

Grypd · 2006-08-24 14:25:44

There are several possible problem I see with this approach, firstly the frictional limits on the speed. The moons escape velocity is some ~2.4km/s, which may be to fast for a rail-track to sustain without damage. In comparision, the fastest bullets travel at ~1.5km/s, though I am not sure if this is the upper limit of possible velocities. Trains and Cars obviously travel much slower. Friction from the track may also create a limit of the velocity the rocket can achive as well

It is this problem that has more or less meant that the only real effective method would be to create a magnetic levitation system for use on the Moon. The benefits of magnetic levitation are that there is little friction with the ground. Control of the object to be propelled is easier and that the only energy source needed is electricity which with ample sunlight is very available. The creation of such a system uses a very high majority local material so insitu works and there is also the fact that there is little or no working parts so wear and tear are kept to the minimum, which is very useful when considering the enviroment.

Problems are that the system will direct cargo's to only a very limited area and the system will need construction.

While Uranium is certianly present in the moon, I doubt we would need to go to the incredible expense of minning or refining it their to use a NTR. Depending upon the design of the NTR its radioactive core could be good for years to decades. A NTR generaly reacts at a higher rate (and uses more enriched fuel as well) then a conventioal reactor, but it is also functional for a DRASTICLY shorter period of time, a matter of hours each month at most. So I think importing the cores from Earth and deploying native fuel could be a praticle approach

It certainly is present, we found that the mineral KReeP contains what we need and it appears to be reasonably common.

Mars_B4_Moon · 2006-08-24 15:29:02

Austin Stanley,
Ion drive is another, NASA has been testing this already and the Dawn mission should soon use this method

Sure it takes a long time, but it saves NASA tonnes of fuel and ion drives have a much higher top-speed
The Euros are currently exploring the Moon with Smart-1 ( ion craft ),
in the long term ion spacecraft could be used to deliver materials or food/supplies to a lunar site
http://www.newmars.com/forums/viewtopic.php?t=1591
ESA and ANU have been working on a DS4G ion thruster
http://www.spacedaily.com/news/ESA_And_ … rough.html
European/Aussie space propulsion

GCNRevenger · 2006-08-24 16:43:01

Ion drive has two main drawbacks for Lunar travel besides the fact that it can't get anywhere in a timely fasion to deliver time sensitive cargo (eg liquid hydrogen).

1-Way too slow to launch, not enough acceleration to even lift its own weight off the gound

2-Where to get the fuel from? There is no Xenon, Argon, Cesium, etc on the Moon to speak of, so it would have to be imported from Earth at substantial penalty

cjchandler · 2006-08-24 17:50:51

A rotovater wouldn't be moving in relation to the surface at it's low point so that's not an issue, but I'll admit it requires quite a bit of infrastructure. Not an unreasonable amount in my opinion, at least for a small one, but I see your point. As far as a track on the ground, which you do realize is quite a bit of infrastructure in and of it's self, might be made fairly economically in two ways. First, in the lunar night the surface temperature is well below 120 K, the temperature required for high temperature superconductors. If some HTS dust/grains could be brought to the moon, they could be sprayed on the ground to make a diamagnetic path. Then with some fairly high power superconducting magnets on the "train" you sort of hover on top of it. Later maybe a reflective sheet could be laid over the track for operation during the day. The main questions here are: How much dust is necessary for a reasonably heavy train and will the train be able to stay on the track without huge amounts of small thruster fuel? The second option would be to fit a lunar rover with a magnetron to produce microwaves and a plow. It could be driven along the surface in a strait line using it's plow to heap dust into two parallel ridges with sharp tops. Then the microwaves could sinter the dust together to make an aluminum/titanium track. This still leaves the question of friction however, if I remember the fastest manned train on earth used a rocket and Teflon runners on the track.

Austin Stanley · 2006-08-24 17:54:48

I certialy don't agree that solar-sails are a joke, they may prove to be an immensily pratical method of moving things about the solar system. They are slow, but they require no fuel (having an infinate) ISP and are reusable. Certianly in the inner system they are pretty much unbeatable.
As for Solar Thermal propulsion, I was refering to a system where the solar energy was "beamed" or reflected to the craft from a ground station, rather than carrying it's own mirrors. Only a secoundary reflector might be required. Alternatively Laser or Microwave power could be used, however these would require eletrical power generation, while reflected light is pretty much free, and mirrors could be light and cheep.
Ok two problems I immediately see with solar sails that would keep me from supporting it: extremely slow thrust - they make ion propulsion look like a Ferrari by comparison; a solar sail a few square kilometers in area makes a pretty fine target to a swarm of micrometeoroids - I don't care if kevlar struts support it I just can't trust a propulsion system thinner than the plastic in my garbage bags. I could see an unmanned interstellar spacecraft making some use of it, but it is, sadly, the epitome of impractical.

Depending upon the size of the sail and the mass of the payload a solar sail may or may perform better than an ion engine in terms of thrust. In terms of specific impulse the solar sail is without equal. As for swarms of micrometeroids damging the sail in some way, this is extreamly unlikely.

Firstly space is mostly empty. Especialy the deep space that a solar sail would spend most of it's time in. Micro-meteriods are few and far bettwen. The odds of the sail hitting a single micro meteroid, even a sail several square kilometer in area, are pretty low, much less a whole swarm of them.

Secound even if the sail did encounter a micrometeroid or worse a whole swarm of them, it is unlikely to have any signifigant effect on it. Solar Sails are huge and the holes created by micrometoids are tiny. As long as an acceptable margine is left in the sails size/weight ratio to compinsate for these microsopic holes, there should be no effect worth mentioning. Indeed, the wholes would be so small that the extra strength margin necessary to compinsate for them is hardly worth mentioning.

Such a tiny whole in the sail is no more likely to cause failure then poking a pin-whole in your garbage bag is likely to make it fail. The big problems with a solar sail lie in stearing it, and deploying the sail.

NASA or any space agency is not going to contruct ground stations for remote propulsion. Worse still, just like laser pen lights, a beam like that would blind any stray airplane or satellite in its path.

I'm not sure we are talking about the same thing, I'm talking about a beam station on the moon to provide for lift to orbit. Blinding airplains and satellites would not be an issue (not that it would be on Earth either).

If a propulsion system takes more than 10 days to reach simply the Moon from LEO or vice versa I have to say it is "out of the race" for human passengers.

Well I mainly advocate solar sails for unmanned cargo transport, but 10 days from Earth to the Moon isn't that bad really. If we start to maintain a long term base on the moon, this should only be a small fraction of the journy.

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It is this problem that has more or less meant that the only real effective method would be to create a magnetic levitation system for use on the Moon. The benefits of magnetic levitation are that there is little friction with the ground. Control of the object to be propelled is easier and that the only energy source needed is electricity which with ample sunlight is very available. The creation of such a system uses a very high majority local material so insitu works and there is also the fact that there is little or no working parts so wear and tear are kept to the minimum, which is very useful when considering the enviroment.
Problems are that the system will direct cargo's to only a very limited area and the system will need construction.

Certianly magnetic levitation could help solve the problem. It's not a perfect solution because it still might be possible for the large craft to get jared and end in diaster. This is no small bullet we are dealing with but a large multi-ton vessle. The energy requirments will likewise be signifigant to levitate such a vehicle. I think magnetic levitation would certianly work, but I think the rocket sled approach would be more ideal if it could work as less infastructure is required.

Austin Stanley,
Ion drive is another, NASA has been testing this already and the Dawn mission should soon use this method.

I think an ion-drived vehcile could make an ideal orbital tug, but they lack the thrust to lift of from the moon surface, which is what I was focusing on here.

RedStreak · 2006-08-24 20:56:04

Magnetic levitaion is not a bad idea, but it sounds borderline to the plain rail-gun proposal. Still no harm in combining a rail-gun with a lunar rocket...

Don't underestimate the threat of meteoroids. Those sails are still supported by struts so a critical hit can bring down a LARGE section which starts affecting your plans...

Yes, cargo obviously if anything. Problem is solar sails need to be very light or else you require obscenely larger sails. You need to slowly deploy those sails...and as Skylab and the ISS have demonstrated the compartely squat solar panels prove unfluring sail like structures won't be 100% perfect 100% of the time. It starts becoming an ineffective balancing act worse than propellant loads on chemical rocket launches.

Again regarding those ground stations, too much stuff here on Earth will be in the way, whether its built by NASA or SpaceX. Giant mirrors or giant laser beams don't come cheap and their beams will be blinding if not occassionally lethal. The Moon would be a better site to use but don't expect immediate contruction. Also what happens if your target is NOT Earth or the Moon? You'll need multiple stations to slow you down, save perhaps Mercury or Venus where the light pressure increases.

cjchandler · 2006-08-25 04:27:28

If you are building a huge mirror/laser a better way to use the power would be with Ablative Laser Propusion. Sure the laser has to be pulsed but aluminum or any other light metal fuel gives ridiciously high isp's and it should be fairly easy to find where ever you happen to be going. If a mirror is to be used then maybe if it has a very sharp focal point and the block of fuel has a large surface area, then the pulsing effect can be achived by moving the focal point around the block. In orbit an inflitable mirror used directly or a solar pumped diode laser could remove the need for a ground station if you weren't in to much of a hurry. Another possibility would be to use a heavey metal an use more of it, with this system the isp can be changed quickly by replaceing the fuel block.
edit: oops here's the link. I'm not making this up http://pakhomov.uah.edu/Minigrant.pdf#s … pulsion%22

Grypd · 2006-08-25 08:46:32

There is one more method of getting objects off the Moon. Tethers.

By having a tether that is long enough it could pick up an object at a reasonable height off the lunar surface (propelled by mechanical spring) and using momentum exchange the cargo is then propelled elsewhere depending on your calculations. Nasa calls this a MXER tether.

It will require a very long cable and a source of fuel to increase the height and keep the spin but it should be a very efficient system to operate.

cjchandler · 2006-08-25 13:12:23

Grypd,
Would the tether be spinning or just grabing the cargo and acellerating it quickly and then hauling it up?

Grypd · 2006-08-25 15:08:24

Grypd,
Would the tether be spinning or just grabing the cargo and acellerating it quickly and then hauling it up?

it would be spinning that way momentum would do the job any other method would rely on the tug to have to lift the whole cable and weight of cargo into space on its own. It would be only as effective as a chemical rocket.

Yang Liwei Rocket · 2006-08-26 11:01:36

Ion drive has two main drawbacks for Lunar travel besides the fact that it can't get anywhere in a timely fasion to deliver time sensitive cargo (eg liquid hydrogen).

You're right GCNR,
I for one wouldn't want to be using ion-drive for sensitive cargo, but as other people say rockets have been around for a century or millenium of years if you're counting the Chinese scientific history but our Ion thruster are still in their early stages of development and it still could be used to transport other materials.
There is thought next to no water on our Moon, and almost no atmosphere but like the planet Mercury there is some there on our Moon- some of the deep craters are thought to contain ice and it does have atmospheric components of Na and Argon. The solar wind has been sweeping the small lunar atmosphere away leaving next to nothing there. Yet if the tiny atmosphere of the Moon were 200 times greater it could remain stable for hundreds of years. Larger human activity on the Moon could push the total mass over the limit and create a stable artificial atmosphere. The European Smart-1, Japan's Hayabusa and NASA's new HiPEP are pushing out the boundaries of ion technology. This year the ESA reportedly made a new type of ion propulsion with four times higher exhaust velocity than previously achieved.

Austin Stanley · 2006-08-26 11:35:59

Ion drive has two main drawbacks for Lunar travel besides the fact that it can't get anywhere in a timely fasion to deliver time sensitive cargo (eg liquid hydrogen).
You're right GCNR,
I for one wouldn't want to be using ion-drive for sensitive cargo, but as other people say rockets have been around for a century or millenium of years if you're counting the Chinese scientific history but our Ion thruster are still in their early stages of development and it still could be used to transport other materials.
There is thought next to no water on our Moon, and almost no atmosphere but like the planet Mercury there is some there on our Moon- some of the deep craters are thought to contain ice and it does have atmospheric components of Na and Argon. The solar wind has been sweeping the small lunar atmosphere away leaving next to nothing there. Yet if the tiny atmosphere of the Moon were 200 times greater it could remain stable for hundreds of years. Larger human activity on the Moon could push the total mass over the limit and create a stable artificial atmosphere. The European Smart-1, Japan's Hayabusa and NASA's new HiPEP are pushing out the boundaries of ion technology. This year the ESA reportedly made a new type of ion propulsion with four times higher exhaust velocity than previously achieved.

I'm not sure what your getting at here, but the point remains that Xenon, Argon, and Neon are not present on the moon in economicaly recoverable quantites. There may be some there, but only in trace amounts.

In addition, while advances in technology may increase the ISP of an Ion engine (best measured by it's exahust velocity), they are unlikely to provide dramatic increases in it's thrust/weight ratio. An ion engine will never be practical for lifting off from a planets surface, or even the moon.

That said I don't think they should be ruled out as a method of transporting "sensative" cargo to and from the moon. The moon is close enough that the additional time penalty is not that great. And if our ion-tug was nuclear powered, it might have additional energy left over to recondense hydrogen making it's transport more pratical.

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Magnetic levitaion is not a bad idea, but it sounds borderline to the plain rail-gun proposal. Still no harm in combining a rail-gun with a lunar rocket...

You are correct, magnetic levitation is pretty much the same as a rail-gun. I think the killer problem with this is building the infastructure to support a multi-ton rockets acceleration to such high velocities.

Don't underestimate the threat of meteoroids. Those sails are still supported by struts so a critical hit can bring down a LARGE section which starts affecting your plans...

The struts or ropes connecting the sail to it's cargo are tiny in comparison. While the sail takes multiple sq km, the support structures take um a few square meters at best. So a metroid strike on them is unlikely. Might as well worry about a meteroid drilling through your capsle and hitting a passenger of something, it's as about as likely. In addition some redundency could be built in here as well, though at a more substantial mass penalty.

es, cargo obviously if anything. Problem is solar sails need to be very light or else you require obscenely larger sails. You need to slowly deploy those sails...and as Skylab and the ISS have demonstrated the compartely squat solar panels prove unfluring sail like structures won't be 100% perfect 100% of the time. It starts becoming an ineffective balancing act worse than propellant loads on chemical rocket launches.

I would argue that we have already developed solar sails light enough to do a very effective job. Commonly avaliable films are in the 10g/m^2 range and some new experimental ones are less than 5g/m^2. Deployment still may pose and issue, but most researchers are convinced it is one engineers can solve, not a show stopper.

Again regarding those ground stations, too much stuff here on Earth will be in the way, whether its built by NASA or SpaceX. Giant mirrors or giant laser beams don't come cheap and their beams will be blinding if not occassionally lethal. The Moon would be a better site to use but don't expect immediate contruction. Also what happens if your target is NOT Earth or the Moon? You'll need multiple stations to slow you down, save perhaps Mercury or Venus where the light pressure increases.

This topic was mainly focusing on methods of going from the moons surface to orbit. Persumably once the vessle is in orbit it could use a diffrent method of propultion. As for setting up such stations, a mirror based one could be rather simple to set-up. The moon gets lots of sun and mirrors can be cheap and light. The biggest problem I see is focusing them all on our departing space-craft, which might be tricky.

Yang Liwei Rocket · 2006-08-26 13:32:09

I'm not sure what your getting at here, but the point remains that Xenon, Argon, and Neon are not present on the moon in economicaly recoverable quantites. There may be some there, but only in trace amounts.
In addition, while advances in technology may increase the ISP of an Ion engine (best measured by it's exahust velocity), they are unlikely to provide dramatic increases in it's thrust/weight ratio. An ion engine will never be practical for lifting off from a planets surface, or even the moon.
That said I don't think they should be ruled out as a method of transporting "sensative" cargo to and from the moon. The moon is close enough that the additional time penalty is not that great. And if our ion-tug was nuclear powered, it might have additional energy left over to recondense hydrogen making it's transport more pratical.

I agree that in order to get the craft into orbit we may need an old fashioned rocket booster like a Ariane/Soyuz/Titan, but once the craft is in orbit it could use an ion-drive to make the trip and save tonnes of fuel. A good iondrive spacecraft may be launched by conventional rocket on Earth and then need only a small lunar-railgun for launch on a return trip.
My point was that we still don't know the full potential of ion-drives and even today we probably know more about the Planet Mars than our own Moon, even though the US beat the Russian with Apollo there's still a whole lot of science we don't know about our own Moon, such as our incomplete knowledge of lunar topography, lack of understanding on what is inside those lunar craters ( calcium -phosphates ? water-ice ? , xenon, pyroxene ? neon and argon ? sodium alumino-silicates ? ) and recent discoveries of new chemicals on the Moon. This may be why the Europeans, Japanese, Chinese and Americans are now keen on getting their next robotic craft on the Moon first before somebody else does it.

publiusr · 2006-10-27 11:54:25

I'd keep ion craft for use as probes. A two stage interplanetary probe--with a nuclear thermal stage and an ion drive payload--would achieve very great speeds and get outside the solar system pretty quick.

SpaceNut · 2019-01-01 16:05:16

The current lunar plan from Zubrin is to make use of 3 Falcon 9 heavies to get us jump started with lunar water ice mining for insitu fuels.

Mars_B4_Moon · 2021-07-14 06:00:11

New Plasma Thruster Concept Could Make Space Missions 10x Faster
https://interestingengineering.com/phys … mes-faster

Mars_B4_Moon · 2022-04-19 13:12:04

'Magnetic anomalies' may be protecting the moon's ice from melting
https://www.space.com/moon-ice-magnetic-field

Trying to sound impressive, Putin says Russia will resume lunar program'
https://arstechnica.com/science/2022/04 … r-program/

Anyone remember those motorcycle cage stunts done by gypsy carnie types so why not get a 3-D printer to seal off a big crater build on the crater's rim ...velodrome or well of death but this time rather than a bike stunt with people its a space-train or space-trucker vehicle and it puts cargo into orbit?

maybe have chemical as back up or an ion drive or nuclear charged particle exhaust that will help out?

The control of movement of products, the mining and unmanned construction machines back and forth between the Moon, the Asteroid Belt, Mars and from Earth should reduce costs

A new system it could be used to deliver or Un-manned missions or transport Low-Tech products in high G force, Stage 2 of the launch can be provided by another type of rocket, Cargo staying on the train suffers higher g but they are hard products or robots and not human or animal, there are many funny pics of the motordrome on sites like tumblr.com and flickr, i guess this would be less of a freak show and more 'modern'.

Hyperloop was marketed by Musk but there are problems to fix, it is a proposed high-speed transportation system for both public and goods transport. It would be a more modern open-source project derived from the vactrain concept. The tube could be a thing of the Moon or Mars and is a large sealed, low-pressure system (usually a long tunnel). Trains would go through an alien tunnel, a pod coach pressurized at atmospheric pressure that runs substantially free of air resistance or friction inside this tube, using aerodynamic or magnetic propulsion. Virgin Hyperloop a company once owned by Branson conducted the first human trial in November 2020 at its test site in Las Vegas, reaching a top speed of 172 km/h (108 mph)

The Moon's surface is already charged and people have looked at ways Material and craft might be moved with frictionless levitation,
Moon does not have an atmosphere and magnetic levitation so Lunar Maglev trains...assuming there is a futurist set up with trains and tunnels through mountains they have no friction in their rails or wheels or systems will have less issues to deal with speed, they can go significantly faster than Earth trains. China and Europe and Russia have looked the the Moon's resources, India plans to launch its own manned missions and an unmanned Lunar lander but the War in Ukraine has left complications in political relations, Japan might g alone and test its own cars and robots. High Speed Transrapid Trains are now a regular part of life in Japan, France and China.

Inventions may not cross over there might be no Moon-Mars program, productive enterprises might find one model successful for Mars and useless for the Moon, likewise a business opportunity on the Moon might be very different on Mars.

'NASA appears to have settled on a Near Rectilinear L2 Halo Orbit (NRHO) for its future Deep Space Habitat (DSH) which its now calling, the Lunar Gateway. NRHOs are a subset of of L1 or L2 halo orbits. NRHO's have large amplitudes over either the north or south lunar poles with shorter periods that pass closely to the opposite pole.'
https://www.dailykos.com/stories/2019/1 … alo-Orbits
Station keeping at an NRHO would require a delta-v (change in velocity) of only 5 meters per second (5 m/s) per year. With an impulsive departure from LEO (Low Earth Orbit) at about 3.124 kilometers per second (3.124 km/s). So a crewed spacecraft from Low Earth Orbit would reach an L2 NRHO in approximately 5.33 days. Orbital capture would require an additional delta-v of 0.829 km/s.

Three-maneuver transfers
https://www.sciencedirect.com/science/a … 7721007766
In this paper, a three-maneuver strategy is presented to study the transfer from a cislunar halo orbit to a low lunar orbit (LLO). Both the cislunar point orbits and lunar orbits are generally considered as habitats for space vehicles of various missions, so a transfer strategy between these orbits that combines flexibility with minimal fuel consumption is worth considering for future complex space applications in the Earth-Moon system.

The Moon and NEAs as sources of cislunar propellant; removing some constraints from a recent paper drives down lunar sourced propellant cost
https://www.sciencedirect.com/science/a … 6521005798
' We derive costs for other cislunar locations that are significantly less expensive than NEAs, the most favourable source identified. A 10-year life of mine can deliver two orders of magnitude propellant cost reductions. We believe this demonstrates that these features can be too significant to be ignored, and thus must be included. '

Magnetic Levitation Studied at JPL for Moving Payloads Around the Moon
https://magneticsmag.com/magnetic-levit … -the-moon/

Dust levitation and transport over the surface of the Moon
Science China Earth Sciences volume
https://link.springer.com/article/10.10 … 016-0015-6
Exposed to space plasma and solar radiation, electrostatic potential may build up in the lunar regolith, leading to a wealth of dust phenomena, including levitation, oscillation, and transport over the surface. Based on plasma sheath theory, the global near-surface plasma environment is modeled, and the dynamics of charged dust are investigated.

Nuclear powered Mars cargo transport
https://ntrs.nasa.gov/citations/19870062917

Dr. Robert Zubrin on Nuclear Energy in Space talks about exhaust velocities
https://www.youtube.com/watch?v=Vxn1DOtKwlg

Last edited by Mars_B4_Moon (2022-04-19 13:26:00)

tahanson43206 · 2022-04-19 13:30:44

For Mars_B4_Moon re #24

It is extremely rare for anyone to come with a new idea.

You may be in that rare number with this one:

Anyone remember those motorcycle cage stunts done by gypsy carnie types so why not get a 3-D printer to seal off a big crater build on the crater's rim ...velodrome or well of death but this time rather than a bike stunt with people its a space-train or space-trucker vehicle and it puts cargo into orbit?
maybe have chemical as back up or an ion drive or nuclear charged particle exhaust that will help out?
The control of movement of products, the mining and unmanned construction machines back and forth between the Moon, the Asteroid Belt, Mars and from Earth should reduce costs
A new system it could be used to deliver or Un-manned missions or transport Low-Tech products in high G force, Stage 2 of the launch can be provided by another type of rocket, Cargo staying on the train suffers higher g but they are hard products or robots and not human or animal

Not long ago kbd512 (I think it was ... might have been Calliban) suggested using the Spin Launch system to launch lunar material out of the Lunar gravity well.

Linear accelerators have been proposed for the Moon for many years as (I'm pretty sure) you have noted in earlier posts.

I've seen a ** lot ** of proposals, but yours today is the first time I've seen the rotating-vehicle-inside-a-cylinder idea for lunar launch

SearchTerm:Launch lunar circular accelerator concept

(th)

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Re: Methods to Lunar Orbit

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