Moonbase and Mass drivers etc etc

Tom Kalbfus · 2006-12-12 09:49:38

Oh, and tugs using electric fields to push off the Earth's? Uh, the Earth doesn't have an electric field. Try a MagSail instead.
The Earth does have a magnetic field it is this that is used to repel a tug from LEO to higher altitudes and it can then attract itself back down to LEO.
Electrodynamic Tethers: Getting into the Swing
It is not a fast system but it does benefit from simplicity.
-On the equator of the Moon, you only get about one week out of the month of peak solar power when the Sun is overhead. Maybe stretch it to 10-11 days with gimbaled panels, but thats extra trouble. Since a railgun will be power hungry, this is the worst-case time you would have to operate the thing.
The solution is simple using our plans to create automated solar cell production we then build solar cell farms to the west and east and connect by buried cables then keep going to increase power supply to the point we actually are working. At the lunar poles it makes sense with the horizon being so close and that we then we will have almost constant power supply. The lifeblood of our space exploration. And when we move to another point we simply connect into what will be a quazi lunar power grid. When we leave the poles to go to the equator we do the same there and connect to the poles.

I think we should at least give the idea of O'Neill type space colonies a thorough study. How close are we those capacities, and how much closer are we than the 1970s when they were proposed. the Ability to build an Island One or a Stanford Torus is the first step in the construction of manned Starships, we should try to develop a space construction capacity for that reason. Presurvation of the Human Race is another reason. Humanity remains vulnerable if it is stuck on one or two planets. Mars colonies ought to be easier to get started as they can start small, but we shouldn't stop there. Inhabiting space ought to reduce our concern with the global environment, since we won't be living on a globe. This greap leap into space has been tougher than anticipated, but I still think we should make the attempt.

Grypd · 2006-12-12 10:32:22

I think we should at least give the idea of O'Neill type space colonies a thorough study. How close are we those capacities, and how much closer are we than the 1970s when they were proposed. the Ability to build an Island One or a Stanford Torus is the first step in the construction of manned Starships, we should try to develop a space construction capacity for that reason. Presurvation of the Human Race is another reason. Humanity remains vulnerable if it is stuck on one or two planets. Mars colonies ought to be easier to get started as they can start small, but we shouldn't stop there. Inhabiting space ought to reduce our concern with the global environment, since we won't be living on a globe. This greap leap into space has been tougher than anticipated, but I still think we should make the attempt.

How much closer are we to the capacity to build O'Neill type space colonies. Easy to answer that we are not much further than the 1970s. We have gone forward in some cases but the true technology needed to make it happen is cheap relaible space flight and that is not present and is nowhere in sight.

We have gone forward in some ways like the improvement in Robotics and the ability to automate solar cell production but not much further than that.

Dayton Kitchens · 2006-12-12 10:47:26

How would it effect mission mass requirements if you reduced the crews to only three astronauts?

GCNRevenger · 2006-12-12 11:03:04

I think that there is a fundamental disconnect between whats reasonable and what you want to see happen Tom

The O'Neill space colony was conceived back when Shuttle was promised to be this all-singing/all-dancing super-cheap space truck, and back when building big space stations from little parts seemed like a good idea. Neither of these is the case.

To paraphrase my saying that some have adopted as their signature, you have a problem with really grasping decimal places I think. An O'Neill colony is estimated to require three million tonnes of Lunar aluminum, glass, etc and ten thousand tonnes of materials from Earth that can't be fabricated elsewhere. And thats only got room for 10,000 people. If you are talking about moving significant portions of people off the Earth, 10,000 at a time out of seven billion isn't going to get you anywhere.

GCNRevenger · 2006-12-12 11:04:13

How would it effect mission mass requirements if you reduced the crews to only three astronauts?

Not much I bet

C M Edwards · 2006-12-12 11:46:54

Then this business about asteroid mining:
-As said by others, the lack of suitable launch windows and longish travel times means that only a big expensive hauler could move enough mass to be worthwhile, reducing efficiency, increasing risk, and basically making the whole operation harder.
-No gravity, which makes digging basically impossible. Without down force there is no good way to dig a hole or pull off good looking rocks from the surface. This also makes metal smelting essentially impractical and is hard on even medium-duration crews.
-Spinning, most rocks have multi-axis spins, which means you can't orbit, hover, or deploy a tether from the surface without continuously burning rocket fuel to compensate. This make solar power pretty precarious too. Theres that physics thing again.
-Overall, asteroid mining is overrated. The only real selling point they have is low Delta-V to get there and back compared to having to land on the Moon. But, if 85%+ of your descent/ascent propellant comes from the Moon (native oxygen) then this isn't such a big deal. The Moon is the place to be for digging materials in space.

These are not insurmountable problems, GCNRevenger.

- I conceed that big expensive haulers of some sort or another will be necessary. But if you want quick travel times for anything in space travel, all haulers are going to be big and/or expensive no matter what you're doing. Asteroid mining is not special in this regard.

- I conceed that there will be essentially no gravity to speak of, especially if we're trying to mine an asteroid small enough to actually work with. (Not every asteroid is the size of Vesta; nor do we want them to be.) However, that only makes it harder if you're intending to scale it like Edmund Hillary. Out of necessity, asteroid miners will hold the asteroid to them, not the other way around.

- Asteroids already spin, God bless 'em. That means we needn't expend as much fuel to finish spinning them up. Eliminating the last vestiges of all that pesky gravity with a little centrifugal force will doubtless assist with the necessary disassembly.

- Low Delta-v is a selling point, but it's not the only one. Another is their energy of position. Asteroids can also be a ready and rich source of volatiles and other materials expected to be buried deep on the moon. They're also potential sources of unprocessed rubble and tailings for bulk radiation shielding. All available at a fuel and power expenditure equivalent to launching from the moon with a much smaller payload.

Tom Kalbfus · 2006-12-12 11:57:16

I think that there is a fundamental disconnect between whats reasonable and what you want to see happen Tom
The O'Neill space colony was conceived back when Shuttle was promised to be this all-singing/all-dancing super-cheap space truck, and back when building big space stations from little parts seemed like a good idea. Neither of these is the case.
To paraphrase my saying that some have adopted as their signature, you have a problem with really grasping decimal places I think. An O'Neill colony is estimated to require three million tonnes of Lunar aluminum, glass, etc and ten thousand tonnes of materials from Earth that can't be fabricated elsewhere. And thats only got room for 10,000 people. If you are talking about moving significant portions of people off the Earth, 10,000 at a time out of seven billion isn't going to get you anywhere.

Yes, those are large numbers, and it tells you how far we still have to go, but I think we shouldn't shrink those challenges. We should have realistic expectations for the immediate future, but we should also try to push the envelope as well. If we want to settle the Solar System, I mean really settle it, we need something like an O'Neill colony. If we just live in tin cans launched from Earth, our ability to live in the Solar System as a society is going to be very limited. Having a handful of people living on the Moon and Mars is a start, but we should not stop there.

I have no expectation of building an O'Neill Colony instead of going to Mars. I believe Mars is a step along the way, not directly of course, but we do have to improve our capacity to get into space to get to Mars and the Moon.

A Moonbase at the Pole could be very much like an O'Neill colony eventually, if we keep on expanding it, then eventually it could house 10,000 people just like an Island One Colony, it would not rotate for gravity of course, but we could build a dome in a crater with an equal land area to one. We'd start out by placing modules on the Moons surface and gradually as the population increased, we'd be able to specialize more and do some construction out of native materials - one of the requirements for building an O'Neill Space Colony. Being sited on the Pole, such a colony would not have to deal with a month long day/night cycle, it could sit in the shadow of a dark crated protected by the Moon's surface from Solar flares and partially from cosmic rays. Mirrors could then reflect the horizontal sunlight straight down into the colony provising light for agriculture. I suppose the mirror or mirrors would have to be light weight and mounted on a turntable so as to track the Sun. A lot of little mirrors would probably be easier.

A polar Moon colony can just as legitimately be called a space colony as would an O'Neill settlement. One possible use for moon rocks, would be as a radiation shield for a cycling spaceships between Earth and Mars. If you pile enough moon rocks around an space ship, you will have an effective radiation shield.

GCNRevenger · 2006-12-12 13:28:09

We should have realistic expectations for the immediate future, but we should also try to push the envelope as well

Three million tonnes of Lunar aluminum and glass are "not realistic" and are so far beyond "the envelope" that even talking about it with expectation of it coming about is crazy. You would have to able to mine, launch, capture, and mill 1000MT Al/SiO2 per day to build even this small O'Neill colony in eight years.

Its not okay to start talking about this scale of a project yet, nor any time soon.

A Lunar colony is not a good idea, despite putting it in a crater you are still vulnerable to 1/2-1/3 of the cosmic rays that come from every direction in space. Mirrors would be no good either, that the total brightness they could reflect is limited by the brightness they receive, and placing a small area of them on the rim of the crater will make it awfully dark in the colony. A large dome capable of housing 10,000 people would also be quite huge and difficult to construct from Lunar glass. The gravity is also perhaps too low for humans to have and raise children, if these children ever wanted to return home to Earth (which many of them undoubtedly would), even Mars is iffy in this respect.

Another thing that you don't understand is that the total population of humanity is not going to increase forever at a very rapid pace, and will in fact probably level off at around 9Bn. We don't need the extra elbow room of a space colony any time soon, and maybe even never.

Random space dirt for ship radiation shielding is an awful idea because if your ship is too heavy, it takes too much rocket fuel to get anywhere.

RedStreak · 2006-12-12 16:15:24

I think we should at least give the idea of O'Neill type space colonies a thorough study. How close are we those capacities, and how much closer are we than the 1970s when they were proposed.

HELLO...we're having trouble building a space station not even the length of a football field, give or take, and it is one that has been met with natorious cost overruns.

Add to that, everything is still being sent up from Earth. We don't have true space production capabilities. At best, we have a shot with VSE to start the seed, but not the fruit-producing tree, of what you're talking about with constructing an O'Neil space colony. Even talk of constructing things out of lunar rock is experimental unto itself.

Any talk about space colonies right now is literally up in the air, and personally I think most of what was envisioned in the 1970s was a tad overrated, i.e. STS and ISS...and worse still has proven to be overrated. For all the tons of material STS has sent up...not one of it related to manned exploration has ventured beyond 500 miles above Earth.

Redesign it for sure - I wouldn't want anything with that much glass. I remember a psychological study cartoon of these things showed a man holding a rock above one of those giant mirrors yelling "Declare me king or I break the window!"

GCNRevenger · 2006-12-12 17:10:52

The glass isn't a problem, make it thick enough and its actually a pretty decent material. Coat it with a little advanced polymer, and you could take a sledge hammer to it without a big leak forming. Or even an Aluminum safety mesh on the outer face. Not that a single pane being knocked out would cause an O'Neill sized pressure vessel to lose pressure within days or weeks.

That said, three million tonnes of it and Aluminum... THAT is a problem.

Tom Kalbfus · 2006-12-13 01:13:11

We should have realistic expectations for the immediate future, but we should also try to push the envelope as well
Three million tonnes of Lunar aluminum and glass are "not realistic" and are so far beyond "the envelope" that even talking about it with expectation of it coming about is crazy. You would have to able to mine, launch, capture, and mill 1000MT Al/SiO2 per day to build even this small O'Neill colony in eight years.

In the book Island One was compared to the Queen Elizabeth II with the point being made that it would have a similar mass to that ocean liner. So we do make objects with a mass of 3 million tons. And why not talk about it, don't they say that talk is cheap? As for the production capability, well we must build our way up to it of course and before that happens we build smaller things.

Its not okay to start talking about this scale of a project yet, nor any time soon.

And I say again, why not, talk is cheap and people talk about starships, which are surely much harder to build than these O'Neill colonies. People also talk about stockpiling and storing antimatter to be used for propulsion and that's way harder than an O'Neill colony, there is talk of building giant lasers to propell laser sails to the stars, all these things are further away than O'Neill colonies which are simply large structures in space.

A Lunar colony is not a good idea, despite putting it in a crater you are still vulnerable to 1/2-1/3 of the cosmic rays that come from every direction in space.

The Earth receives cosmic rays that come from all directions of space too. How many cosmic rays that are received by the colony would depend on how recessed the colony is into the Moons surface, it is is recessed enough, then the cosmic rays can only come from one direction, directly above the colony.

Mirrors would be no good either, that the total brightness they could reflect is limited by the brightness they receive, and placing a small area of them on the rim of the crater will make it awfully dark in the colony.

So? I didn't include the condition that the area of mirrors be small, and mirrors don't need to be of glass either, a shiny reflective sheet of aluminum would do just fine. The mirror would of course be flat, and it would be in the shape of an oval. The oval shaped mirror would be held above the colony dome by a light weight tower with spindly legs mounted on a circular track surrounding the dome. The oval shaped mirror is held above the dome at a 45 degree angle so that it catches the horizontal sun rays and reflects them downward, the circular track allows the mirror to track the Sun as the moon rotates. The mirror always faces the sun and reflects the sunlight downwards into the dark crater where the dome is situated. If "night" is desired then individual segments of the oval shaped mirror are rotated 45 degrees so that their edges are oriented towards the colony dome, such that each segment reflects the light back at the Sun instead of down on the colony. When the mirror is looked up at from directly underneath it appears circular due to its 45 degree tilt. When the mirror segments are oriented edge on toward the colony, the onlooker would see the mirror framework and the stars shining through the individual mirror panel frames. Unlike on Earth when you build tall towers, on the moon you don't have to worry about windloads on the cross section of the tower or the mirror. The tower can be made light weight and just strong enough to support its own weight and the weight of the aluminum mirror it holds directly above.

A large dome capable of housing 10,000 people would also be quite huge and difficult to construct from Lunar glass. The gravity is also perhaps too low for humans to have and raise children, if these children ever wanted to return home to Earth (which many of them undoubtedly would), even Mars is iffy in this respect.

The population of a Lunar colony would likely be transient, people would tend to come and go, and what you said about Lunar gravity is also a good argument for O'Neill colonies since those can be made to provide Earth level gravity environments.

Another thing that you don't understand is that the total population of humanity is not going to increase forever at a very rapid pace, and will in fact probably level off at around 9Bn. We don't need the extra elbow room of a space colony any time soon, and maybe even never.

You can't predict at what level the population will level off at, that is a result of individual decisions about whether to have children. Humans have historically always filled in their living space, if more living space is provided, they are likely to have additional children to fill that in as well. If you are so down on space colonization, then why bother to talk about manned space travel at all, you could live in a world where everybody stares down at their feet all the time. The whole point of space travel is to expand the range of habitats humanity can inhabit, I really don't see any other reason for people to travel in space.

Random space dirt for ship radiation shielding is an awful idea because if your ship is too heavy, it takes too much rocket fuel to get anywhere.

Do you know what a cycling orbit is?
It is an orbit that takes the ship from the vicintity of Earth to the vicintity of Mars, and the gravity of Mars bends the orbit path just enough to send the ship back to Earth, whose gravity bends it juist enough to send in back to Mars again and this cycle is repeated over and over again with very little or no propellent expended. A cycling spaceship doesn't require much in the way of rocket engines to maintain its cycling orbit. You could have lunar rock placed around the cycling ship as it cycles around in its orbit, more and more lunar rock can be added with each passage close to Earth, until the cycling spaceship has a thick coating of rock that can block just about any type of radiation due to its sheer bulk, even secondary particles caused by cosmic rays hitting rock can be blocked if there is enough rock underneath it, and since rock is plentiful on the Moon and water is scarce, you use the rock. The rock needn't be processed overly much, a simple net can hold the stuff onto the spaceship, passage ways can protrude outside the layers of rock so that other ships can dock with the cycler.

GCNRevenger · 2006-12-13 06:43:39

These are not insurmountable problems, GCNRevenger.
- I conceed that big expensive haulers of some sort or another will be necessary. But if you want quick travel times for anything in space travel, all haulers are going to be big and/or expensive no matter what you're doing. Asteroid mining is not special in this regard.
- I conceed that there will be essentially no gravity to speak of, especially if we're trying to mine an asteroid small enough to actually work with. (Not every asteroid is the size of Vesta; nor do we want them to be.) However, that only makes it harder if you're intending to scale it like Edmund Hillary. Out of necessity, asteroid miners will hold the asteroid to them, not the other way around.
- Asteroids already spin, God bless 'em. That means we needn't expend as much fuel to finish spinning them up. Eliminating the last vestiges of all that pesky gravity with a little centrifugal force will doubtless assist with the necessary disassembly.
- Low Delta-v is a selling point, but it's not the only one. Another is their energy of position. Asteroids can also be a ready and rich source of volatiles and other materials expected to be buried deep on the moon. They're also potential sources of unprocessed rubble and tailings for bulk radiation shielding. All available at a fuel and power expenditure equivalent to launching from the moon with a much smaller payload.

Yes they are:

-Just writing off the fact that you will have to use large vehicles for practical transit to/from the rock is senseless, you don't need a big ship for travel to/from the Moon. But I digress, many of the things that kill asteroid mining dead are huge inefficiencies that are a consequence of unchanging physical problems, and this is one of them.

If a cargo ship takes too long to transit to/from its destination, then it has to be an unreasonable size to be effective. If we are mining base materials, then a few-times-annually is not going to cut it. For instance if we want 1000MT of Aluminum a year from a 3mo distant asteroid, you'd need a ship capable of carrying 500MT. The Moon with a 1wk turn around only needs 19MT, twenty five times smaller. Who cares if it consumes more fuel? Most of the fuel is free from the Moon anyway, and this is assuming you use a rocket at all to launch instead of a railgun or a space elevator (which are plenty strong on the Moon already).

Its also a problem if you need to ship time sensitive cargoes (emergency spare parts) and prevents changing crews often for the sake of zero-gravity/radiation exposure. Don't brush this off, ISS astronauts do well enough after 6mo but they don't have to do any heavy labor to speak of. Plus, if the rock is 3mo away, then your miners will spend 6mo in zero-gravity just getting there and back. Unless you have a behemoth spinning crew ship too.

Out of necessity, asteroid miners will hold the asteroid to them, not the other way around

What the heck is that supposed to mean? You can't move a multi-million-tonne mountain of nickel & iron! Even an arsenal of atomic bombs could hardly nudge such a thing! That means you are going to have to go to the rock, since you can't bring the rock to you. Thats just ridiculous! And there is no good way to do this!

Spinning is a BAD BAD thing! What you don't realize is that the spin of most smaller rocks is multi-axis, which means that there is no point over the rock which you can orbit continuously, only a carefully guided powered hover burning relatively large quantities of rocket fuel. It also means no tethers, no elevators. Also, unless you are on one of those rocks like Vesta that are spherical, the slight gravity will be different depending on where you are on the rock.

This also means that you aren't going to be "taking apart" a rock, because your ability to pull ore from the surface is limited by your ability to dig down and grab the ore in the first place. Since you have near-zero gravity, you have no down force to do this digging. And since you have no stable orbital axis, you will have to burn quite a bit of fuel to get the ore back to the space refinery.

This also wrecks the use of solar power on the surface, the panels just don't face the sun, and the spinning of the rock will ensure that no practical gimbals system or panel density will be practical.

Bulk radiation shielding is worthless, its too much trouble to haul it from anywhere that requires rocket fuel for transit. Boron-doped or Hydrogen-impregnated polyethylene from Earth or Mars will be the obvious choice for space ship radiation armor.

And who cares about asteroid volatiles? Those volatiles are so far away on a rock that you can't effectively dig on nor regularly receive shipments from. The Earth with a true "no kidding" RLV fleet and the Moon's unlimited supply of Oxygen will do just fine, especially since we'll already be there anyway.

Tom Kalbfus · 2006-12-13 09:56:40

Spinning is a BAD BAD thing! What you don't realize is that the spin of most smaller rocks is multi-axis, which means that there is no point over the rock which you can orbit continuously, only a carefully guided powered hover burning relatively large quantities of rocket fuel. It also means no tethers, no elevators. Also, unless you are on one of those rocks like Vesta that are spherical, the slight gravity will be different depending on where you are on the rock.

How can you spin in more than one direction at a time? If you spin any object you are going to have a single axis of spin. If you add some spin in a different direction you are going to change the axis of spin but you are still going to have only one spin axis. Have you ever heard of a planet with two Geographic North Poles? Suppose we added a second spin to the Earth so that the second North Pole was in Miami, Florida, Could the Earth retain its first North Pole and also have a second? I don't think this is possible.

Also asteroids come in a variety of sizes and are in a variety of orbits around the Sun. One can "cherry pick" the asteroids, find an Earth Orbit crosser, one that only needs a slight nudge to end up in a more convenient orbit, ideally to orbit the Earth where it can be worked on continously. You don't need bombs to mudge an asteroid, a mass driver will do. You can exert a steady and gradual push on the asteroid, cange the orbit just enough so that the asteroid intercepts the Moon. The Lunar gravity can act as a break on the asteroid causing it to drop into an orbit around the Earth. If the orbit is set right, it will be some time before the Moon intercepts the asteroid again at its furthest point and it will give plenty of time to mine the asteroid while it is in Earth Orbit. Further nudgeing will bring the asteroid out of the Moon's reach. The Moon can serve another purpose besides as a source of materials.

This also means that you aren't going to be "taking apart" a rock, because your ability to pull ore from the surface is limited by your ability to dig down and grab the ore in the first place. Since you have near-zero gravity, you have no down force to do this digging. And since you have no stable orbital axis, you will have to burn quite a bit of fuel to get the ore back to the space refinery.
This also wrecks the use of solar power on the surface, the panels just don't face the sun, and the spinning of the rock will ensure that no practical gimbals system or panel density will be practical.
Bulk radiation shielding is worthless, its too much trouble to haul it from anywhere that requires rocket fuel for transit. Boron-doped or Hydrogen-impregnated polyethylene from Earth or Mars will be the obvious choice for space ship radiation armor.

In a cycling orbit spaceship, you only have to place the shielding their once, and the cycling spaceship simply follows its orbit from Earth to Mars and Mars to Earth, it doesn't not accelerate under its own power, so the mass of the shielding once its brought there is irrelevant.

And who cares about asteroid volatiles? Those volatiles are so far away on a rock that you can't effectively dig on nor regularly receive shipments from. The Earth with a true "no kidding" RLV fleet and the Moon's unlimited supply of Oxygen will do just fine, especially since we'll already be there anyway.

Not all asteroids are far away, and not all asteroids are in the asteroid belt. Through orbital interactions with the planets, some asteroids are in more convenient orbits for us to exploit. Some asteroids coorbit the Sun in approximately the same orbit that the Earth follows, and there is always the possibility that Earth Trojans may exist.

C M Edwards · 2006-12-13 13:19:43

I can’t (believably) downplay the difficulties inherent in asteroid mining, but I think you’re understating the relative problems of obtaining material from the lunar surface. They are such that obtaining the same material from asteroids is at least a competitive proposition.

Your own “who cares if it consumes more fuel if the fuel is free?” argument could be applied to any trip you like - from Earth, from the moon, or from an asteroid - so long as fuel is available at the point of departure. Getting to an asteroid in the first place need not require any more (or less) fuel than getting to the moon – it all depends on the target. So, comparing outbound delta-v lends no obvious advantage to either method. And, while the rockets required for either approach will be large (I’ve never seen a sounding rocket with a 19+ MT payload), the vehicles required to reach and mine an asteroid need be no larger than those needed to reach and mine the moon if you send both in the same quantity.

So, yes, if you can write off the fact that large vehicles are needed for travel to/from the moon, then I can write off the fact that the same size vehicle will be needed for asteroid mining, too.

I also take issue with your assertion that we can’t move an asteroid.

Oh, we can’t move Vesta, or even Eros. But we could come home with something the size of 2002 AA29.

An asteroid of this size, with a minor diameter of less than 60 m and a mass of less than 250000 MT, would have a gravitational acceleration of around 0.000002g (utterly negligible). A minor axis rotation period of less than 7 hours would completely negate this, and anything faster would tend to spin loose regolith off of the asteroid. Lashing to the asteroid with a few hundred meters of spectra line is not an incomprehensible feat (and it can be done without ever needing any other means of latching on), and is all that is necessary to deploy a low thrust engine. The hydrogen/oxygen rocket fuel needed to spin-up the asteroid is determined by the change in angular momentum required. The fuel required is only 300 kg of H2/LOX to crank it up to a 7 hour period from a dead stop. With 10MT fuel or more, you could spin the asteroid clean for prospecting. With a few times more fuel, you could spin it apart and see what’s inside (which is what I recommend for anything larger, BTW). An equally efficient use of the same fuel is to bring the asteroid’s spin to a near stop on all axes so that solar power can be employed.

19 MT of fuel – your suggested lunar supply payload – can eliminate the whole “spin BAD BAD!” objection for asteroids of 300m minor diameter or larger.

Once 24:7 solar is available for months at a time, there’s no reason to remain limited to chemical rocketry for propulsion. Unfortunately, electric rocket propulsion with exotic fuels will not do the trick, either – the fuel needed to bring 2002 AA29 to Earth in less than a year exceeds the GTOW of a Saturn V rocket at the asteroid surface, even using relatively efficient engines. Not that this isn’t equal to the mass you proposed launching from the moon over one year with 250 times the potential payoff, but it does move beyond the “just write off the fuel” regime. You can’t write off the fuel if the fuel is the only thing you’re hauling.

To effectively move the rock, a means must be found to use the asteroid material for fuel, just as you proposed using lunar material for fuel.

This is where one might care about asteroid volatiles. However, that would require actually hauling refining equipment out to the asteroid, and assumes that the asteroid of interest is volatile rich – even if what you’re really after is nickel-iron. There’s a better way.

Time for some vaporware. :twisted:

The weight (gravitational force, not mass) of 1000 MT of asteroid material in the asteroid’s gravitational field is only 20N. If you can get it free, it doesn’t take much to get it clear of the asteroid. And that can be spun, too. Using an electric motor with a reel of rope, you can get that 1000 MT mass whirling at 100 m/s – at stresses within the capability of spectra rope – and throw it off of the asteroid. Releasing that sling at the right angle will impart new rotation and a rearward motion of 40 cm/s. 160 just like it – two thirds of the mass of the entire asteroid – will give you enough velocity to get the lonely remaining chunk of asteroid into earth orbit. But each of those outbound chunks also has double the velocity needed to reach earth orbit. If you send two even larger chunks at a time, themselves connected by a smaller sling capable of 100 m/s, one of the chunks can be thrown off to decelerate the other into earth orbit. In this way, half the mass of the asteroid can be sent to earth orbit 1000 MT at a time, instead of just the last 1000. If the part reaching earth is the part with the sling, a recovery crew can re-orbit it the same way by flinging off another chunk.

As for actually getting purchase on the asteroid in zero-g, if you’ve got the 10 MT of spectra rope necessary for the larger sling, you’ve got enough to wind it around 2002 AA29 approximately 130 times. Just bola the thing and tie yourself on.

The whole process can be accomplished with outbound payloads no greater than 19 MT. I’d guess about three to five per year per 1000 MT payload per year.

RedStreak · 2006-12-13 15:27:08

Do you know what a cycling orbit is?
It is an orbit that takes the ship from the vicintity of Earth to the vicintity of Mars, and the gravity of Mars bends the orbit path just enough to send the ship back to Earth, whose gravity bends it juist enough to send in back to Mars again and this cycle is repeated over and over again with very little or no propellent expended. A cycling spaceship doesn't require much in the way of rocket engines to maintain its cycling orbit. You could have lunar rock placed around the cycling ship as it cycles around in its orbit...

Mars Direct completely nixed that idea. You still have issues with rendevous - AFTER accelerating to the speed these cruisers are already going at. It makes it kinda redundant and we're only sending handfuls of people not shipfuls.

RedStreak · 2006-12-13 15:30:27

Have you ever heard of a planet with two Geographic North Poles? Suppose we added a second spin to the Earth so that the second North Pole was in Miami, Florida, Could the Earth retain its first North Pole and also have a second? I don't think this is possible.

Ooooh...so that's where evil Santa lives. :twisted:

C M Edwards · 2006-12-13 16:02:48

Do you know what a cycling orbit is?
It is an orbit that takes the ship from the vicintity of Earth to the vicintity of Mars, and the gravity of Mars bends the orbit path just enough to send the ship back to Earth, whose gravity bends it juist enough to send in back to Mars again and this cycle is repeated over and over again with very little or no propellent expended. A cycling spaceship doesn't require much in the way of rocket engines to maintain its cycling orbit. You could have lunar rock placed around the cycling ship as it cycles around in its orbit...
Mars Direct completely nixed that idea. You still have issues with rendevous - AFTER accelerating to the speed these cruisers are already going at. It makes it kinda redundant and we're only sending handfuls of people not shipfuls.

I wasn't aware that there was a limit to the number of people you could put on a cycler.

Grypd · 2006-12-13 16:15:18

Cyclers are for routine deliveries of large numbers of personel and equipment and may be the only way for future colonisation.

Still we could always use NIMF technology to provide the shuttle service

RedStreak · 2006-12-14 21:47:14

The point is cyclers don't stop...ever. To rendevous you have to archieve escape velocity which is what something like Mars Direct would already be doing. Propellant-wise you're talking about wasting more to make an extremely difficult rendevous in interplanetary space.

Its an ellegant idea but problem is when you look at the actual requirements and numbers its not.

Tom Kalbfus · 2006-12-15 03:13:09

The point is cyclers don't stop...ever. To rendevous you have to archieve escape velocity which is what something like Mars Direct would already be doing. Propellant-wise you're talking about wasting more to make an extremely difficult rendevous in interplanetary space.
Its an ellegant idea but problem is when you look at the actual requirements and numbers its not.

A cycling spaceship is actually a misnomer, the proper term would be a cycling space station, as that is what this spaceship is. Now what good is a space station, you might ask? Look at the ISS for example, it has solar panels and equipment for keeping astronauts live for months at a time. The Shuttle can bring astronauts into orbit, but it is no good as a home for months at a time. To reach a Cycling spaceship once its established, you need a rocket such as a Saturn V, or Aries V, and you need a CEV to deliver astronauts there. The CEV probably has life support for 2 weeks, enough time to reach the cycler and dock with it and enough time to get back. The Cycler provides an environment which can support the astronauts for months at a time, if it is large and elaborate enough, it can have a closed cycled life support system, that can generate oxygen, remove carbon dioxide and grow food for the astronauts to eat. The astronauts eat the food that is grown on the station and they contribute waste for use as fertilizer and water to be recycled. Docked with the cycler is a Mars Lander with enough fuel to make a soft landing on Mars. The lander departs the cycler for the surface of Mars while it is inbound toward Mars, and while it is outbound moving away from mars, another lander rises from Mars to meet the cycler so it will be ready for the next group of outbound astronauts, or perhaps carrying astronauts from Mars heading to Earth. Everything the Astronauts need on Mars is brought up from Earth, but everything they need to survive the interplanetary cruise is already established on the cycler.

RedStreak · 2006-12-15 05:31:05

That's what I assumed regarding cyclers. You still have to waste so much propellant and then there's how you handle maintaining something that big.

Personally I'd just make something more like a reuseamble Mars transit vehicle; a craft that waits in high orbit over each planet and then leaves when everything's loaded up. Far easier rendevousing with something in local space than interplanetary space.

Tom Kalbfus · 2006-12-15 10:29:45

That's what I assumed regarding cyclers. You still have to waste so much propellant and then there's how you handle maintaining something that big.
Personally I'd just make something more like a reuseamble Mars transit vehicle; a craft that waits in high orbit over each planet and then leaves when everything's loaded up. Far easier rendevousing with something in local space than interplanetary space.

Doesn't that depend on economies of scale? For ten people it might not make any sense to have a cycler, but what if you plan to send hundreds or thousands of people to Mars in a single launch window? We'll assume also that a Mars colony has already been established and that housing is constructed with native materials, the biggest tast becomes just bringing the people with their luggage to Mars. For that you need an enourmous cycling space station that carries and reuses all the infrastructure needed to support that many people on the outbound and inbound legs of the journey both ways. The Cycling space station basically has a closed recycling life support system, food is grown their, oxygen is regenerated partly with the help of plants, and their are some peopl who actually live on this space station serving the needs of the passengers enroute to Mars, it is basically a space hotel, there are people who work and live here and there are the transients on their way to Mars or back to Earth.

Cyclers can start out small however. It looks like we won't build an Island One for a while yet, I believe someone said it would require 3,000,000 tons of lunar material, but what if we built a one tenth scale Island One, so instead of it being 3,000 feet in diameter it is only 300 feet in diameter? If we kept the rotation rate the same as in the larger model the inhabitants would experience one tenth Earth's gravity at the space station's equator, and the amount of lunar material required to build it would be only 3,000 tons, about the equivalent of 30 payloads of the Aries V rocket delivered to low Earth Orbit. If we could build the ship at L5 or perhaps even L1, then we could use a high efficiency engine to slowly bring it into a Cycler Orbit. Where the Full scale Island One has land area for 10,000 people, the one tenth scale Island One can provide the same amount of living space to 100 people. The mass of the Island one is a cubic function and it gets reduced by a factor of 1,000, but the interior area of the sphere is only a square fucntion of size so the living area only gets reduced by a factor of 100 on a one tenth scale reduction in size.

A One tenth scale Island One would require 3,000 tons of building material, while it is possible to bring that material up with multiple expendable rockets, it might be more economic to process lunar material on a small scale. This would be great practise for when we work up to building actually full scale O'Neill colonies. Granted one tenth gravity wouldn't do much to keep the travellers in shape, but it would help them to move around a bit more easily, and eat their meals in a non "zero gee" environment. Perhaps if people's stomachs can tak it, the Mini Island three can be spun a bit faster to provide Mars Level gravity at the equator.

RedStreak · 2006-12-15 16:27:50

Doesn't that depend on economies of scale? For ten people it might not make any sense to have a cycler, but what if you plan to send hundreds or thousands of people to Mars in a single launch window? We'll assume also that a Mars colony has already been established and that housing is constructed with native materials, the biggest tast becomes just bringing the people with their luggage to Mars.

You're thinking well past terms of horse-and-carriage and thinking freight train there Tom.

Firstly, even a few centuries from now, I doubt moving people between planets will be cheap...and I'm talking far more expensive than suborbital jumps being advertised for celebrity gimmicks. You'll be lucky to get a hundred people ala Red Mars in an Underhill-style colony.

Second, Mars won't be an open settlement to anyone. The Moon more likely will before Mars namely b/c we're STILL trying to seek out life on Mars, and opening the planet to settlements on the scales you're talking would massively contaminate that effort. For the first 50 years of exploration Mars will be wilderness with at absolute most 24 people spelunkering around.

Grypd · 2006-12-15 18:02:51

Doesn't that depend on economies of scale? For ten people it might not make any sense to have a cycler, but what if you plan to send hundreds or thousands of people to Mars in a single launch window? We'll assume also that a Mars colony has already been established and that housing is constructed with native materials, the biggest tast becomes just bringing the people with their luggage to Mars.
You're thinking well past terms of horse-and-carriage and thinking freight train there Tom.
Firstly, even a few centuries from now, I doubt moving people between planets will be cheap...and I'm talking far more expensive than suborbital jumps being advertised for celebrity gimmicks. You'll be lucky to get a hundred people ala Red Mars in an Underhill-style colony.

We can only look into our past to see what can happen and why people will move to colonise new lands. Like the first colonies of America. People will move to these new colonies for various reasons but it comes down to cost and it is just how much of a percentage of there wealth it costs. In the first colonies the trip used to cost about 80% of a persons available wealth. There where also state sponsored colonists in this indentured criminals who made a work force for the original colonists. If we can reduce the cost to deliver a person and his family to about this percentage of cost the various reasons will ensure that people will be willing to go.

We cannot do this method of mass personel transport by sending so much from the Earth. So we have to develop the technologies and infrastructure using cheaper places to deliver the majority of what is needed.

Second, Mars won't be an open settlement to anyone. The Moon more likely will before Mars namely b/c we're STILL trying to seek out life on Mars, and opening the planet to settlements on the scales you're talking would massively contaminate that effort. For the first 50 years of exploration Mars will be wilderness with at absolute most 24 people spelunkering around.

If you believe that the Humans races destiny will be held back for microbes im sorry to say you are mistaken. China or Russia will not care and frankly neither does Nasa or Europe. Finding extraterrestial life will be incredible but we will still go to Mars to stay and live and the future is to spread the Human race not to keep it as a pristine science experiment.

Tom Kalbfus · 2006-12-16 11:57:44

Doesn't that depend on economies of scale? For ten people it might not make any sense to have a cycler, but what if you plan to send hundreds or thousands of people to Mars in a single launch window? We'll assume also that a Mars colony has already been established and that housing is constructed with native materials, the biggest tast becomes just bringing the people with their luggage to Mars.
You're thinking well past terms of horse-and-carriage and thinking freight train there Tom.
Firstly, even a few centuries from now, I doubt moving people between planets will be cheap...and I'm talking far more expensive than suborbital jumps being advertised for celebrity gimmicks. You'll be lucky to get a hundred people ala Red Mars in an Underhill-style colony.
Second, Mars won't be an open settlement to anyone. The Moon more likely will before Mars namely b/c we're STILL trying to seek out life on Mars, and opening the planet to settlements on the scales you're talking would massively contaminate that effort. For the first 50 years of exploration Mars will be wilderness with at absolute most 24 people spelunkering around.

Anyone can see Mars is not an abode of life, at most underground bacteria if even that. In any case what's more important, the bacteria we haven't found yet or us? I don't try too hard to look at the Universe through the point of view of hypothetical Martian bacteria. If the life is that hard to find, its not worth worrying about.

I wouldn't be so quick to write off the next 50 years of technological progress. Are we supposed to take stupid pills and go "Duh" for the next 5 decades? We made such marvelous technological progress in the first half of the 20th century and then someone applied the breaks. Some one will step on the gas eventually, I don't think we'll be stuck in the 20th century for that much longer, things are coming to a head, we're running out of petroleum, and somethings going to have to be invented to replace it. Computers are getting ever more sophiticated, so if we humans are too stupid to travel the Solar System, then our mechanical friends will do it fo us, they will figure out a way, even if they have to be 100 times smarter than us to do it.

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