Mars Colonization Program - Mission 1: Your Comments?

RobertDyck · 2005-06-02 11:36:01

As I said a few times, ferrous metals will always be cheaper from an M-type near Earth asteroid than the Moon, but the Moon is a great source of aluminum and titanium. Spacecraft tend to be built of aluminum and titanium, not steel because steel is heavier. So, yea, lunar materials will be included in a colony transport.

As for fuel, Lunar Prospector found conclusively that there are no large chunks of ice at the poles of the Moon. If there is any ice, it's grains the size of a grain of sand. But the source of that hydrogen is most probably a C-type asteroid that struck. That means much of the hydrogen is clay, gypsum, Epsom salts, and tar; only some is water. Considering how thinly scattered hydrogen is at the lunar poles, I doubt it'll ever be economical to harvest for fuel. If you want fuel from C-type asteroid material, go to a C-type asteroid.

The Moon could use powdered aluminum with liquid oxygen as fuel. The problem is how to feed powdered aluminum into the rocket combustion chamber. You can pre-mix them, but monopropellant is dangerous. You can blow powdered aluminum with nitrogen gas, mixing with liquid oxygen in the combustion chamber. That treats Al/LOX as a bipropellant, but the Moon doesn't have any nitrogen. If you can figure out how to feed powdered aluminum into a rocket engine with all the pressure it has, then you've got in-situ propellant for the Moon. For now, we can transport methane and produce LOX locally on the Moon.

I have gotten through somewhat with GCNRevenger. I argued for DC-X style reusable shuttle for Mars, as well as SCRAM jet powered SSTO RLV for Earth. He's now arguing for them. I think they're invaluable to transport humans and technology. However, bulk fuel would be best manufactured in space.

I'll tell you want. If you don't believe transporting Mars settlers is big business then stay out of it. It's my dream to found and own the company that builds that transport ship, as well as heavy equipment for asteroid and lunar mining. Not to operate the mines, but to manufacture all the equipment for mining. You continue to claim it won't be done, I'll continue to seek start-up capital to make it happen. It's my goal to see Mars colonization within my lifetime. Not just a manned science mission, colonization.

Grypd · 2005-06-02 12:04:51

I have gotten through somewhat with GCNRevenger. I argued for DC-X style reusable shuttle for Mars, as well as SCRAM jet powered SSTO RLV for Earth. He's now arguing for them. I think they're invaluable to transport humans and technology. However, bulk fuel would be best manufactured in space.
I'll tell you want. If you don't believe transporting Mars settlers is big business then stay out of it. It's my dream to found and own the company that builds that transport ship, as well as heavy equipment for asteroid and lunar mining. Not to operate the mines, but to manufacture all the equipment for mining. You continue to claim it won't be done, I'll continue to seek start-up capital to make it happen. It's my goal to see Mars colonization within my lifetime. Not just a manned science mission, colonization.

You are trying to preach to the converted

I have always stated that a 100% reusable and cheap TSTO or SSTO is the most single important device for getting space and colonisation started. Its my belief though that Goverment does not see a need for it and the buisness world would rather sell its expensive single use rockets. But if there is an economic reason then there becomes the imperative to make them.

But for settlement to happen we need to reduce launch costs and SSTO,TSTO can and will do it but the mass fractions these work on makes them poor cargo carriers compared to a rocket. The more economically we can send people up the better the same with the larger craft. If it is cheaper to build the bulk on the Moon and then by use of mass driver send it up to be assembled that is what we will do.

As for asteroid mining if you will read my post in this thread about how to get Hydrocarbons etc out of C class asteroids you will see I agree with that. I do have trouble with how do we mine heavier elements like metals out of asteroids.

SpaceNut · 2005-06-02 12:09:44

Here is the reference I have on lunar soil propellant.
Lunar Soil Propellant or LSP
Web site does not show any recent work thou on this problem.

Martin_Tristar · 2005-06-02 19:54:59

You will require a new approach in creating a stable interplanetary economy to build a successful Mars Colony. When developing the moon or near-earth asteroids or the Asteroid belt past Mars or the outer planets and moons you will need an overall strategy and technology to meet these challenges.

By using all L Points for the interplanetary developments they can increase the movement of personnel, equipment, vessels and material resources into space and from space. Also by using the L Points we can increase the volume of people living and working in space and increasing the economies of scale to a sustainable level. That will push our technology forward.

srmeaney · 2005-06-02 21:46:36

Iran announced Tuesday it had successfully tested a new solid fuel motor for its arsenal of medium-range ballistic missiles, a technological breakthrough that sparked fresh alarm in Israel.

I suppose that explains what Iran is doing with the six nukes it pulled from the soviet cruise missiles it bought through the Black market a while back. I guess 3000 km is better than 300km. I suppose if they second stage their midrange balistic missile, they might even become a real threat to the continental USA ...years from now when the USA is bogged down in North Korea because some fool decided to go North Korea with Stealths and the Subsequent Atomic fall out over the USA resulted in Economic ruin and collapse of the rule of law.

My dear srmeaney,allow me to introduce you to a very useful word. . . quadrillion. "Two hundred million billion" is another way of saying 200 quadrillion. Trillion is a thousand billion; quadrillion, by the way, is a thousand trillion. (At least, in American English; in British English billion, trillion, and quadrillion are I believe a thousand times bigger.)
Where do you get this figure of 200 quadrillion dollars? If you think that's how much it will cost to put a colony of 10 million on Mars, think again; you just spent 200 billion dollars per person!
The Earth's current gross planetary product is 32.3 trillion, of which the United States produces 10 trillion. If you assume this will increase a lot over a century and multiply by 1000 (instead of by 100) then perhaps the twentieth century will see a total economic output of 32.3 quadrillion dollars. That's only 15% of the amount you want to spend on Mars!
Perhaps you should try a different formula for calculating the cost.
-- RobS

Robs, What is the point of going to Mars only to rebuild industry from the Stone Age? Colonization of Mars requires the ability provide the entire populace with Medicines, equipment and those important little things we all appreciate. Conceivably we could just build ten cities for a million humans each in earth orbit and with a full population land on Mars with a ready to go City. The point is that the Commonwealth of Mars will be able to achieve its own Colonization and define it's own future. By providing its citizens with the advances available Mars begins as an advanced civilization of very smart, very healthy people who are free of the despotism that plagues even Democracy.

RobertDyck · 2005-06-02 22:53:40

Iran announced Tuesday it had successfully tested a new solid fuel motor for its arsenal of medium-range ballistic missiles, a technological breakthrough that sparked fresh alarm in Israel.
I suppose that explains what Iran is doing with the six nukes it pulled from the soviet cruise missiles it bought through the Black market a while back. I guess 3000 km is better than 300km. I suppose if they second stage their midrange balistic missile, they might even become a real threat to the continental USA.

I doubt it. There's a big difference between a theater ballistic missile and an intercontinental ballistic missile. To go intercontinental you have to leave the atmosphere; it's suborbital. That means you need an entry vehicle for the warhead. The steaper the entry angle the more accurate it is, but the hotter the heat shield gets and more G forces. Targetting gets very difficult. It's more likely they want to threaten a target within range of the new missile. The Shehab-3 missile only has a range of 2,000 km. That can reach Pakistan, India, all of the Arab world including Egypt, Isreal, Turkey, Eastern Europe, Kazakhstan, and southern Russia but not Moscow. I suspect their nuclear capable neighbours are targets, not the US.

And where did you hear about Iran having six nukes? According to http://www.globalsecurity.org/wmd/world … htm]Global Security Iran purchased 12 cruise missiles with a 3000 km range. That could reach Moscow, all of Eastern Europe and Italy, but not the US. Most importantly, the Global Security web page states the cruise missiles were not sold with their nuclear warheads.

RobS · 2005-06-02 23:08:20

Robs, What is the point of going to Mars only to rebuild industry from the Stone Age? Colonization of Mars requires the ability provide the entire populace with Medicines, equipment and those important little things we all appreciate. Conceivably we could just build ten cities for a million humans each in earth orbit and with a full population land on Mars with a ready to go City. The point is that the Commonwealth of Mars will be able to achieve its own Colonization and define it's own future. By providing its citizens with the advances available Mars begins as an advanced civilization of very smart, very healthy people who are free of the despotism that plagues even Democracy.

I apologize, but I have absolutely no idea what you mean.

-- RobS

srmeaney · 2005-06-03 04:48:53

I apologize, but I have absolutely no idea what you mean.
-- RobS

I too apologize also for not making myself clearer.

The idea of such an amount ($200 Million Billion Dollars over one hundred years for the financing of Colonization by ten million people and their Move into Space) allows for equipment that will be used by the decendents of the Mars colonists to be sent to Mars. It allows for the free space travel from Earth to the Moon and Mars that will ultimately be enjoyed by both colonists and tourists for all time. It finances replacement systems and mass food shipments. It pays for the Maintenance and operation of Space Transports with a capacity of Ten Thousand people beyond their use for Colonization. It pays for the Education, training, provisioning, housing, and of every single colonist and potential colonist. It pays for The infrastructure and territory needed on Earth to do every thing that is required to achieve those goals including the research which will be the intellectual property of the Commonwealth of Mars.

Because the Commonwealth of Mars will and must Become the Single Nation that Governs all space beyond Earth and it's petty little Warlords. You can't achieve that without creating permanent and self sustaining infrastructure in Space.

clark · 2005-06-03 08:54:11

I know I will regret this, but why should the CommonWealth of Mars be the sole governor of all space beyond Earth?

By what right does their authority extend beyond Mars? If it is all space, then shouldn't it be called the Commonwealth of Space?

GCNRevenger · 2005-06-03 09:09:31

A truely efficent way to launch materials from Earth is a precondition for any Martian colonization or any Lunar industrial exploitation beyond a little Platinum mining. Efficency in this case can only be achieved by abandoning expendable means for the vast majority of payloads of all kinds, from fuel to bulldozers. In this case, the only vehicle that could reasonably accomplish this task is probobly an SSTO spaceplane, since reintegrating/seperating a TSTO vehicle would likly prevent it from being inexpensive enough for a vehicle of reasonable size. Combine this with a reuseable GCNR or other high-Isp cycler and a Methane-fueled DC-X on Mars, and that is probobly the only way barring a space elevator on either end.

That said, and where Robert misconstrues my argument, is that we SHOULD NOT start with such vehicles from the beginning. Should NOT! Colonization will require a "foothold" base for fuel & industrial support, which would be built by expendable or semi-expendable means like NASA DRM or semi-reuseable equivilent.

Next off, building any major cycler or colonization hardware on the Moon is a non-starter, period. Building such things is very difficult here on Earth, where reasources and construction facilities are easy, and since each cycler or piece of Mars machinery isn't going to be THAT big, its all going to be sent up via SSTO. It would be FAR, FAR easier then trying to build anything on the Moon, there just isn't any reason to put that kind of industrial capacity there if you have easy Earth launch, especially given the radical lack of Carbon, Nitrogen, and other elements.

I also still maintain that asteroid mining isn't worth it. The amount of hardware needed just for simple H2O/volitiles extraction will be so expensive to launch, send, and operate that it won't be able to compete with a private commertial spaceline with a 25MT SSTO flying often.

Finally, I want to remind srmeaney and the rest of us that the majority of materials needed for colonization by mass WON'T be made on Earth, since the cost of that would be prohibitive, most of the bulk items and materials will have to be made on Mars. Bulk plastics, base metals, glasses, food, water, Oxygen and so on can be made on Mars in quantity if you simply give the factories time to operate. A polymer processing plant could be automated to make fabrics, furnature, and so on using only Martian air and water for instance... dishes made from Martian glass, cutlery from Martian plasma steel, so on and so forth... only things that are difficult to produce or procure will be sent from Earth, like computer hardware, turbopumps, and nuclear reactor componets.
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In WMD news... North Korea could very well copy the Russian SS-18 perhaps that could reach America, and who says that Iran's purchased superlong range missiles have to be fired from their country? Put a CW tip on a few of them and fire them from a ship at America.

RobS · 2005-06-03 10:14:06

Srmeany, my friend, you still have not addressed the fact that you are proposing to spend far more on Mars colonization than the Earth's entire economic output. Saying "this is needed" does not help. The U.S. currently spends 15 billion dollars a year out of a 10 trillion (10,000 billion) dollar economy. In other words, somewhat more than 1/1000th of its total economic output. IT IS A FANTASY to say that we can increase that fraction significantly. It would be a miracle to push government expenditures on space (NOT just on Mars) to 20 billion. With proper tax incentives and involvement of private industry, it is highly unlikely you could push total space expenditures above, say, 30 billion per year. What is the point of talking about "million billion dollar" budgets in such circumstances? Why should we take such discussion seriously? I think there are some on the board that are simply ignoring your postings for this reason.

-- RobS

BWhite · 2005-06-03 11:14:49

As I have posted elsewhere, nickel vapor deposition is a marvelous early method of space manufacturing.

Find an asteroid with metallic nickel (not oxides) and you can fabricate almost anything at moderate temperatures. Here on Earth, nickel vapor deposition is tricky because Ni(CO)4 is highly toxic, yet working in space will be hazardous enough to begin with.

RobertDyck · 2005-06-03 11:45:40

GCNRevenger, I submitted abstracts for papers for this year's Mars Society conference in Boulder. You should go. One paper is my idea of a mission plan for the first science mission. I talked about it a few times on this board, the result is a semi-reusable ITV that goes from Earth orbit to Mars orbit and back. If that's what you mean by a cycler, then that's it. It can be made fully reusable by replacing the expendable propulsion stage with a high Isp reusable one once it's available. This doesn't require any infrastructure other than an HLLV and crew space taxi. Actually, you could build it with EELV but that would require a lot of launches; Shuttle-C would be better. The space taxi I mentioned so many times it's probably old already is a small semi-reusable TSTO. The space taxi could be replaced by a SSTO hypersonic spaceplane once it's available.

No need to go to the Moon or asteroids. That's only required to reduce the cost of a colonist transport ship to something passengers could afford, paid by ticket price alone. Platinum mining and satellite refuelling are just to pay for establishing space mining infrastructure.

Notice I'm saying a science mission to Mars doesn't require going to the Moon at all. Repeated science missions to Mars don't require the Moon at all. However, George W. said "Moon" so NASA has to go to the Moon. Besides, NASA is very cautious. Have a look at space mission success and you'll see why. NASA will want to test all equipment on the ground, then in LEO, then on the Moon before going to Mars.

Another objective is integrating the space advocacy community. We need to stick together if we are to get any humans beyond LEO. The Moon guys want to build a permanent base on the Moon. I don't think that's a good destination, the Moon isn't good for much other than space telescopes, but let's work together. Giving them a market for mined lunar materials will unite them in our cause for Mars. There's the question of lower propellant cost for an S-type asteroid vs. easier operation in lunar gravity, is an aluminum mine more cost effective on a NEA or the Moon? But you already argued for the Moon so let's stick with that just to unify the Moon guys into our cause. Besides, I really don't think building a large colonist cycler with material lifted from Earth, even by a SCRAM jet SSTO, could be cost effective enough to be profitable by ticket price alone.

RobertDyck · 2005-06-03 11:57:10

As I have posted elsewhere, nickel vapor deposition is a marvelous early method of space manufacturing.
Find an asteroid with metallic nickel (not oxides) and you can fabricate almost anything at moderate temperatures. Here on Earth, nickel vapor deposition is tricky because Ni(CO)4 is highly toxic, yet working in space will be hazardous enough to begin with.

That is the Mond process that I talked about for M-type asteroids.

reddragon · 2005-06-03 15:26:06

It may be better to concentrate on building a space elevator than trying to develop ssto or other launch vehicles, since the elevator would render these other systems obsolete. An elevator can allow cargoes to go from Earth to orbit essentially on a train, much cheaper than any rocket-powered vehicles will ever be. Once one cable is built it will be relatively easy to build several more and greatly increase the amount of cargo that can be hauled up and down on a regular basis. More than anything else a space elevator can open up space. It can be used to transport the machinery needed for asteroid mining or interplanetary spaceships which can then be assembled in space and can bring asteroid metals, especially the valuable PGMs, and space-manufactured materials down to Earth. In addition it can carry people: tourists, workers, and Mars settlers. The ticket price will be fairly cheap as will be the cost of transporting cargo. The cars that move up and down the elevator can be powered by electricity generated either by a plant at the bottom or a solar array at the top and carried to the car through the cables rather than by expensive rocket fuels. The cars will be ready to go back up pretty much as soon as they get down, eliminating the long waits between flights of a vehicle. The space elevator will open up space to business and to average people and both will come. The initial cost of building the elevator would be high, but it could almost certainly be made up for once the elevator was in service, especially in the years while the original owner has a monopoly.

RobertDyck · 2005-06-03 16:41:30

A space elevator has its own problems. First it's slow; 300km/h is very fast for a vehicle rolling along a cable. At that speed it would take 5 days to reach GSO. Not practical for human travel. It would orbit once per day (along with the rest of the Earth) so LEO would be too slow to detach from the cable.

Second, the only material strong enough is carbon nanofibre. Carbon burns and an electrical conductor to space becomes the world's largest lightning rod. It would require at least an electrical insulator that protects carbon from oxygen and rain, as well as fire proof. Still, would lightning burn through the insulator? It may have to be non-conductive to prevent lightning.

Third, it would be a hazard for satellite orbits. Equatorial orbits at any altitude other than GSO would hit it. How many inclined orbits cross the elevator cable, potentially colliding with it?

Lastly, trains have been replaced by aircraft due to their higher speed and absence of rails. Rails cost money to maintain and consume land that can be used for other things. The elevator cable would be the equivalent of rails. Would a SCRAM jet SSTO make a space elevator obsolete like airplanes made rail roads obsolete?

Commodore · 2005-06-03 17:45:07

Lastly, trains have been replaced by aircraft due to their higher speed and absence of rails. Rails cost money to maintain and consume land that can be used for other things. The elevator cable would be the equivalent of rails. Would a SCRAM jet SSTO make a space elevator obsolete like airplanes made rail roads obsolete?

We still have trains to haul heavy cargo, and that will be the elevators primary purpose.

GCNRevenger · 2005-06-04 10:01:39

No no, no ITV and OSP 2.0!

The bennefits of reuseability just don't make any sense, we won't be flying CEV often enough to justify a fully reuseable system, maybe just three flights a year for a sustained Lunar and Martian presence. The ITV is a terrible idea because its wildly overkill, you don't need that much room for a three day Lunar hop, and a capsule has the option of emergency return at any time directly to Earth's surface which neither vehicle could provide. And for Mars, since early missions should be 100% expendable until REAL Martian propellant is available (not the piddly little amount for a MAV with imported H2), then you'll need a capsule for Earth reentry anyway. No OSP redux

The hypersonic SSTO is NOT a near or even mid term solution, basic materials science must advance signifigantly before ceramics and composits can withstand the fantastic temperature deltas over and over again without signifigant risk. The other options, a space elevator, is much more practical then you think Robert...
-As long as you can move two climbers at once you can send multiple payloads up at a time, one side going up and one back down.
-The lack of access to LEO isn't a problem, since colonization payloads don't need to go there.
-The elevator is plenty fast enough for people, provided the car has radiation shielding.
-The material you'd make the cable with isn't pure CNT fiber, its fiber composit, the conductivity of which will not be a problem as the binder is an insulator. We're talking currents in the milliamps.
-An aluminum or nickel vapor-deposited sheath will be needed to protect against atomic oxygen, but that only needs to be a few atoms thick.
-Earth orbit is a very big place, and there aren't all that many satelites in LEO to dodge as most are in GEO. The cable could even be preturbed slightly as needed.
-CNT composites are now ~60% of the strength required, and the threshold is not far out of reach. This is a young technology.
-Comparisons between the space elevator and rail lines are a silly straw-man and you know it.

"No need to go to the Moon or asteroids. That's only required to reduce the cost of a colonist transport ship to something passengers could afford"

No way, I take issue with this. Its never going to be easy enough to fabricate large, delicate vehicles in zero-g cheaply enough out of ideal materials to compete with truely efficent Earth-launch. Not ever. Going to the asteroids or the Moon to build ships is a fools' errand of a side-trip. As far as mining goes, I still maintain that the Moon's gravity and accessability easily breeze past any meager advantages of rocket fuel savings for asteroid mining. The only Lunar materials worth going to get are Platinum and He3. They just don't weigh that much.

"Besides, I really don't think building a large colonist cycler with material lifted from Earth, even by a SCRAM jet SSTO, could be cost effective enough to be profitable by ticket price alone."

And I think you are flat wrong. The TransHAB module that NASA played with could comfortably house six people, and weighed about eight tonnes. Now, factoring in cube/square bennefits, a 25MT TransHAB could probobly hold the 25 people that a colony cycler would be sized for. If an SSTO can carry 25MT in a single flight, then you could assemble, fuel, and man the vehicle in half a dozen flights. At around $10M each, thats only about $50M of launch costs with ~$25M reccuring per sortie. At a million dollars a head, the "Martian Commonwealth Foundation" chipping in using the interest off its Earth assets, and you could reach a cost low enough for moderatly wealthy families to afford.

reddragon · 2005-06-04 15:19:40

LEO would be too slow to detach from the cable.

Why would you need to detach from the cable? If the trip to GSO takes too long, you could have a space station along the cable somewhere in LEO where you can stop the cars to unload and reload them and then send them back down. Space ships can leave from and dock with this station and can be used to travel to the Moon, other space station, the planets, asteroids, or pretty much anywhere.

Second, the only material strong enough is carbon nanofibre. Carbon burns and an electrical conductor to space becomes the world's largest lightning rod. It would require at least an electrical insulator that protects carbon from oxygen and rain, as well as fire proof. Still, would lightning burn through the insulator? It may have to be non-conductive to prevent lightning.

Is carbon nanofibre the same as carbon nanotubes. I have read that carbon nanotubes can be made to conduct electricity and I presume they do not burn in doing so. You would of course need an insulator as you suggest.

My idea for a space elevator is to make it work something like a mag-lev train. The basic cable is made of carbon nano-tubes for strength and covered with a protective coating. Coils are attached to the cable that can be turned on and off as electromagnets that are used to pull the cars forward. Electricity is provided either through a wire or through the nanotubes themselves acting as a wire. The cars can be made to fully encircle the cable and be supported by magnetic levitation. Thus there is no friction with the cable.

Fledi · 2005-06-04 18:59:29

Simple tethers are quickly cut by micrometeoroids. The lifetime of a simple, one-strand tether in space is on the order of five hours for a length of ten km.

This is from wikipedia's space tether section. I think it's, if true for all materials, one of the more serious issues to deal with.
For a rotovator, one or two maintenance wagons should be enough to keep up with the exchange of failing tether parts, but for a true space elevator you would need hundreds of intermediate maintenance stations to deal with the problem.
But maybe nanotubes will prove to be more effective against micrometeoroids.

For all tethered concepts you have the advantage of having a big space station with artificial gravity at the far end of the elevator. This could prove very useful for building larger spaceships. I'm thinking about manufacturing the parts here on earth and then sending them up for final assembly at the station.

RobS · 2005-06-05 02:05:39

Reddragon, here's the problem with low earth orbit: At the altitude of a few hundred miles, the cable will be rotating around the earth once every 24 hours, and thus will be moving at about 1,000 miles per hour (1,600 kilometers per hour). Anything in orbit at that altitude is wizzing around the Earth at 17 times that speed (17,500 mph to be exact). If something were to "let go" of the cable at that altitude it would fall straight to Earth; it would hit the Earth in a matter of a few minutes, in fact (based on the formula s = 1/2 a t-squared, s = 200,000 meters and 1/2 a = 5 meters per second per second, so t squared is 40,000 and thus t = 200 seconds or a bit more than three minutes!). A spaceship that "undocked" from the cable would not be in much better of a position than one on the surface of the Earth; it would have to accelerate to a very high velocity very quickly or it would fall to the Earth.

-- RobS

RobertDyck · 2005-06-05 02:34:54

GCNRevenger, you are still falling into the trap of believing the horrible price gouging of large aerospace companies over OSP is the realistic price of an OSP. It isn't. I already gave the justification that says why even at NASA prices the development of OSP is 1/10th of what they were asking. The mini HL-20 space taxi can be built quickly and affordably, you just have to manage the project.

You don't use the ITV to go to the Moon! Don't fall into the same trap that created the Space Shuttle: one vehicle that does everything but nothing well. Rather you need a series of special-purpose vehicles that are all small, simple and inexpensive and each a master at its mission. That means a dedicated unmanned cargo launcher (EELV for medium cargo, SDV for heavy), a small space taxi for crew, a reusable lunar transfer vehicle that goes for LEO directly to the lunar surface and back, and a reusable ITV that goes from LEO to Mars orbit and back. The inflatable surface habitat will be common to both Moon and Mars, although Mars doesn't need a micrometeoroid shield but does need protection from dust storms and dry ice infiltration.

And for Mars, since early missions should be 100% expendable until REAL Martian propellant is available (not the piddly little amount for a MAV with imported H2), then you'll need a capsule for Earth reentry anyway.

What makes you think any mission "should be 100% expendable". You're only supporting the large aerospace contractors who demand the American taxpayer purchase a multi-billion dollar vehicle with every mission only to throw it away after a single use. If you can't make use of modern developments then you don't belong in any mission planning. That's like saying the 80% efficient life support system Robert Zubrin talked about in 1990 should be used for Mars, despite the fact we now have a system that's over 95% efficient. Robert Zubrin said it would be the 21st century before such a life support system is ready, well it is the 21st century and it's here. Likewise, the concept of expendable capsules died with Apollo. Doing it right the first time will not cost a lot now, but will save a lot of money for the second and subsequent missions.

As for lunar mining, you still ignore the fact that any iron-bearing mineral on the Moon is an oxide such as ilmenite wile M-type asteroids are ferrous metal. You have to smelt Moon ore, you don't smelt asteroid ore because it's already metal. That is the huge difference, and much more important than any fuel saving.

So now you claim SCRAM jets are far off despite the fact X-43 already flew, and a space elevator is near term despite the fact no one has built a carbon nanofibre longer than a few millimetres. The technical distinction for reddragon is that nanotubes have open ends while carbon nanofibres have sealed ends. Carbon nanofibres (or nanotubes) are the only material with sufficient strength-to-weight ratio to hold itself up. Binding sub-millimetre whiskers in epoxy doesn't get anywhere near the strength of the fibres themselves. That short-cut just doesn't cut it. A space elevator will require individual fibres several metres long; no one has been able to do that.

Aluminum and nickel are electrical conductors. They won't protect the CNT cable from lightning. CNT with carbon atoms arranged along the fibre are 30 times more conductive than copper, while CNT with carbon atoms arranged helically around the fibre are semiconductors. A semiconductor will create resistance to lightning, making heat and vaporize in a fraction of a second. A conductor would do better, but any conductor has a maximum current it can handle before over heating. Lightning is over 100 million volts, often several hundred million volts. Lightning current is usually between 5,000 and 20,000 amps but has been reported over 200,000 amps. That's with a lightning rod on a building; a cable running to space will get much more. Any conductor will attract lightning because of the differential charge; a conductive space elevator will attract lightning like a proverbial magnet.

Thank you Fledi, the statistics about micrometeoroids cutting space tethers is very valid.

The bottom line is a space elevator is farther off than an SCRAM jet, and the cable of a space elevator will get in the way of any satellites or spacecraft in orbit.

Fledi · 2005-06-05 05:39:06

The orbital paths of LEO satellites are known, maybe not that accurately yet but that will change in the near future with all the new GPS measurings becoming aviable.
Now if the path is known, you can have the space elevator swing a bit from side to side or have some of the strings pushed away from the others to evade collision. With a rotating tether there is an additional possibility by changing the rate of rotation by winching in parts of the tether or having a wagon change position along the tether. The latter one also goes for a space elevator, even if not to that extent.

reddragon · 2005-06-05 09:24:04

A spaceship that "undocked" from the cable would not be in much better of a position than one on the surface of the Earth; it would have to accelerate to a very high velocity very quickly or it would fall to the Earth.

There is no need to undock from the cable. A car travelling up the elevator can simply decelerate (along the "up" vector) as it approaches the station. At the station it stops, unloads, and then returns to Earth all without leaving the cable. Of course a station in GSO would probably be optimal. I only suggested the LEO possibility if the trip to GSO is deemed to take to long. However, the 5 days time given by RobertDyck isn't unreasonable at least for cargo which weighs much more than people and is thus much more expensive to transport by rockets, spaceplanes, etc. Also it is probably quite possible to achieve speeds higher than 300km/h.

A space elevator will require individual fibres several metres long; no one has been able to do that.

True, but the technology is young and advancing rapidly. Within a decade or so we will probably have this ability.

Aluminum and nickel are electrical conductors. They won't protect the CNT cable from lightning. CNT with carbon atoms arranged along the fibre are 30 times more conductive than copper, while CNT with carbon atoms arranged helically around the fibre are semiconductors. A semiconductor will create resistance to lightning, making heat and vaporize in a fraction of a second. A conductor would do better, but any conductor has a maximum current it can handle before over heating. Lightning is over 100 million volts, often several hundred million volts. Lightning current is usually between 5,000 and 20,000 amps but has been reported over 200,000 amps. That's with a lightning rod on a building; a cable running to space will get much more. Any conductor will attract lightning because of the differential charge; a conductive space elevator will attract lightning like a proverbial magnet.

Could the elevator cables be made so that they were not grounded? This way lightning wouldn't strike them. Another option is to have a lightning rod running parallel to the elevator cable, a more conductive wire that will take the lightning and that can hold more current.

The bottom line is a space elevator is farther off than an SCRAM jet

I must admit that you're probably right. Development of a SCRAM jet is certainly worthwhile and will be important in opening up space. I just think that a space elevator is not too far in the future technologically and that it would really open up space to everyone.

GCNRevenger · 2005-06-05 15:31:11

Yes yes yes, the "big evil companies jack up the price 1,000% and AltSpace management-magic will fix it" argument... nonsense. Building a baby HL-20 would easily cost several billions of dollars (no real work was ever done on the $5Bn HL-20 except mold lines and cockpit, which you aim to scrap), another nine-to-ten-digit sum for the brand new very light weight high-thrust dual propellant turbopump reuseable rocket engine, another eight or nine for the 747 mods and fuel tank respectively plus eight for each tank copy... I don't think a price lower then ~6-7Bn or so is realistic. Nobody outside the larger aerospace firms have the skills to execute such a vehicle, and their work does not come cheap. I simply don't believe your "justification" or that "supporting their ilk" is somehow a problem... they are, after all, the only game in town.

The simple fact of the matter is that reuseable systems don't make any sense right now. They do not. No reuseable system will be worthwhile unless and until two preconditions are met: the availability of propellant at the destination for the return journy, and a justification that makes a more expensive reuseable system worthwhile versus a cheap expendable. Safety is also a substantial concern.

It is going to take quite a lot of payload, probobly some prospecting, and substantial boots-on-ground manpower to establish a propellant facility on either the Moon or Mars that can make enough fuel to support a mostly/entirely reuseable system to either body. Doing this with reuseable vehicles does not make sense, because the fuel they must carry to return themselves to Earth, the trouble of preparing them for the return trip in space, and the comparitive ease & cheapness of simply building copies of low-cost-development expendables is just plain the better option. Later on, not right now, and not at first, then and only then should you consider reuseability. The inherint efficency advantage of not lugging fuel to return to Earth or even LMO/LLO/L1 simply trumps reuseability.

That said, we can and should make the vehicles that it is convienant with the option for future reuseability, like the Lunar lander and the NASA-DRM style ERV. However, things that are not convienant to make reuseable should simply be left expendable until waaay down the road when the flight rate is high enough to justify a reuseable system. That time is not now and not for the near future. Right now, getting started relativly quickly and on budget is more important then the operating costs being low as possible, and that means expendability to "do it right," not reuseability.

A word about safety and "old versus new" concepts... I think your opinion that capsules are "obsolete" is silly, they most certainly are not obsolete, and are infact the safer option for Lunar travel and a preferred one for early Mars missions (in case Earth aerobrake fails, reduced mission complexity). No manned transfer vehicle of any kind between Earth and Lunar orbit is nessarry as the capsule is big enough, plus it is the only practical option for immediate anytime emergency abort to Earth. An efficent Lunar transfer vehicle could not have this option, and since you won't be flying that much (six times a year for a dozen people w/ 4mo rotations) then a capsule will be the method of choice for the forseeable future. You would need one for an Earth reentry vehicle from trans-martian velocity too.

"As for lunar mining, you still ignore the fact that any iron-bearing mineral on the Moon is an oxide such as ilmenite wile M-type asteroids are ferrous metal. You have to smelt Moon ore, you don't smelt asteroid ore because it's already metal."

And you ignore the fact that there are crashed asteroids on the Moon, and that trying to mine base metals in zero-G is probobly impossible to accomplish economicly, and you would still have to melt down asteroid metal ore for purification anyway... at least on the Moon, the liquid metal in your smelter will stay put and not float all over, and the slag will rise to the surface (albeit slowly).

"So now you claim SCRAM jets are far off despite the fact X-43 already flew"

The X-43 is a pitiful toy, barely capable of accelerating at all and at the verge of melting. A true regenerative Scramjet will be needed to reach high enough speeds to make SSTO practical, and that is distance down the road. No material yet exsists that can withstand the heat and the cold needed to make such a scheme work, which basically limits non-regenerative Scramjets to speeds under Mach 15. You need to hit Mach 20 without rocket boost to enter orbit efficently.

I am not saying that a space elevator is right around the corner, it probobly isn't, but neither is an efficent Scramjet SSTO. Carbon nanotube technology is still advancing fairly quickly, we have managed to come a long way in a pretty short time, and quite likely the pace of development will continue... we're doing some work with CNT composits in the very building I work in. Also, the statistics for cable breakage for a single strand cable are irrelivent since a cable won't be made from a single strand. You would have to have multiple debries strikes in the same meter(s) long stretch of the cable, which just isn't likly to happen. A "ribbon" a meter wide would last a hundred years easily from 1cm on down impacts without avoidance.

Lightning and incliment weather shouldn't be a big problem since the composite isn't conductive (the nanotubes aren't contiguous), it won't "attract lightning" or whatever. The metal coating is only required to protect against atomic oxygen and unfilterd (by ozone) UV light, neither of which are a problem in the lower atmosphere where the weather is. The metal cladding wont' be added to the elevator at lower altitudes at all. And if the cable is fried by lightning in the last few kilometers? Stop climber traffic and just drop another few kilometer segment to the ground and reconnect, no problem. Just don't run the climbers when there is a thunder storm.

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