Uses of Bulk Nano Materials (was beanstalks)

wrote:


Purchase price of the immediate consumable? Hydroelectric, wind, or solar is cheaper. Purchase price with the capital and infrastructure costs properly amortized? Who knows? The "correct" answer is strongly correlated with political opinion.

Nuclear is not of itself evil. However, there is a history of stupidity and greed among those who seek to practice the nuclear cult for profit.
My proposal to improve nuclear safety is to operate the reactors the same way the US Navy nuclear sub force does: The operators have to sleep in the reactor building for six months at a time.
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I just noticed I accidentally snipped too much, the product in question is hydrogen, not LOX as may have been implied by my snippage.
The correct answer in this context is almost certainly not hydro/wind/solar generation of hydrogen by electrolysis. hydro/wind/solar are only debatably competitive with other methods of electricity production. Once you add the extra factor of several of efficiancy from generating the hydrogen from natural gas directly without going to electricity then it just doesn't compete economically.
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Certainly, since air and energy are the two main inputs, and air is available for the taking(*). The energy cost isn't high, especially since sizable LOX plants work quite hard at reducing it, but that and the costs of equipment (capital and maintenance) are the big expenses.
(* In fact, a lot of commercial LOX has traces of hydrocarbons in it, simply because air in industrial areas tends to contain them. )

Most unpleasantly large amounts of energy, alas. Water electrolysis tends to require about 10kW-hr/kg, and of course only 11% of the output is H2. That's a net requirement of 90kW-hr/kg, which is really quite a lot, and thoroughly uncompetitive with making it from natural gas.
(And then you have to liquefy it, of course, but you'd have to do that no matter how it was made.)
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yeah, it makes aluminium smelting completely pale in comparison.

--
Sander

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Around 40% efficiency?
I was under the impression that somewhere around 60% was available OTS, with 90% possible with more expensive systems. I could check...
Pete.
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If you get the chance, I'd be curious -- my numbers are somewhat old.
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wrote:

After a quick Google search...
It seems large commercial alkaline hydrolysis units are around 65-70% efficient. Electricity costs seem to be about 70-80% of the hydrogen production cost.
Commercial PEM electrolysers are apparently slightly less efficient at the moment but are promising to soon reach 80-90% at pressures in the 10-50 bar range. PEM fuel cell research has been aiding development.
Norsk Hydro seem to be one of the main leaders in the industry.
Pete.
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This is a bit fast and loose...
I assume that is $1/kg, not $0.1/kg, ideally, LEO takes about 10kWhrs/kg, inferring 10 cents per kWhr at the climber. Though elevators are more suited to GEO and need help in getting to LEO.
For an optimistic hydrocarbon SSTO with a 2% payload fraction I get less than $5/kg base fuel cost to LEO, (should be easy with CNT :-). Methane/coal might enable something a bit cheaper, as would rotovator augmentation.
When we consider the comparative structure/payload fractions, (payload over elevator weight vs. payload over rocket drymass weight), then the capital cost of the rocket is around an order of magnitude less than that of the elevator. (I am assuming here that the CNT elevator will cost a similar amount on a per kilogram basis as rocket drymass, you may question this). And further, say a two week climber turn around time compared to a two hour rocket turnaround time, (assuming LEO).
In summary, assuming development cost is covered, the elevator will have something like a thousand times the dry mass, (and hence capital cost), for a given mass flow rate to LEO. I would think that straight rocket approaches might ultimately achieve costs in the $10/kg range. Until then fuel/energy costs are in the noise and I do not see that an elevator is justified.
Depending on capital cost, an elevator may eventually be cheaper for bulk transport, though it only goes to one place and it takes a week to get there, very inconvenient. Hopefully there will be significant technological progress, (like high speed climbers), but this is also true of rockets.
Pete.
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You are forgetting that empty elevators going down for another load can help to lift the full elevators going up.
Too bad you can't pull off that trick with rockets.
Your calculation needs to count the elevators as part of the fixed mass of the beanstalk - a capital cost, not as an operating cost, unlike the cost of lifting and then lowering rocket shells.
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Actually I was interpreting payload in the strict sense, so no. Also, I do not think this is even practically possible in the short term, too heavy.
I should make the point that beanstalk mass is highly dependent on specific strength, which is still very uncertain, so for the sake of argument, within an order of magnitude is fine. :-)

That is what rotovators are for, much cheaper and easier.

Pete.
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Oh dear. Sorry all, typo. I meant $10. Should not post when tired.
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They're of interest because *in the long term*, amortized over very large amounts of traffic, they are the cheapest launch method imaginable, and free of the troublesome environmental issues of really-high-volume traffic using most other methods.
As I've noted elsewhere in the discussion, it is much harder to make an economic case for near-term first-generation versions, especially if you perversely :-) insist on using the same assumptions (e.g., sizable steady flow of small payloads) for the comparison systems, instead of stacking the deck in favor of the beanstalk by comparing it to today's off-the-shelf systems. In the near term, technological coolness factor is the beanstalk's main advantage. :-)
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snipped-for-privacy@spsystems.net (Henry Spencer) wrote in message wrote:

Compared to EM launch guns? I'm not sure I buy that. The capital costs of a beanstalk seem so gigantic I'm not sure if they would ever be recouped if you consider opporunity costs or maintenance costs. Maybe in a couple of centuries...
But it still appears that its second to electromagnetic launch guns; Several hundred miles to a thousand miles of evacuated track, built on earth out of ordinary materials with the main technological obstical being switching speeds... not entirely insurmountable and logistically doable.
Versus tens of thousands of miles of an imaginary engineering material being built in space...

Yah. it sounds 'cool.' But I still dont see it being competitive with other technologies over the long term.
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Dez Akin wrote:

Dale Trynor wrote: Some guesses. Seams reasonable to speculate that while its at least feasible to make and test a beanstalk on the truly cheap that can only lift perhaps a few kg at a time. Mass drivers at near earths surface would require very large masses if you want a reasonable amount of its velocity to remain after air distance dose its work, so cheap experimental prototypes of them are not so likely.

Quite some time ago I did some posts asking for opinions on the idea of a pneumatic tower and or ramps based on the idea of using pressurized tanks as a construction material. A point made was if one used a lighter than air gas to fill the tanks and if they were to match the air density together, one would have no limit on how high such a structure could become as long as one had air to provide this equal buoyancy. Didn't get much feedback as seams typical of most of my posts, but some did mention why not just use balloons. The idea did involve some rather simple questions that should have gotten some more informative answers.
The reason for why this seamed interesting is the possibility of not only energy generation but for use as a launch platform especially where mass drivers were concerned because one has a thinner atmosphere to deal with at much higher altitudes. I think it was that every 3.5 miles up was about 1/2 the atmospheric density. A tower 9 miles high would have about ~1/8 atm, if this was correct and that would be a big help on our mass retaining its escape velocity without the requirement of being gigantic not to mention the increase of efficiency and the slight problems of keeping the system evacuated are probably easier to manage.

Imaginary at this time perhaps, as time will tell.

Time will tell and besides personally I would like to see both closely examined. To email me remove the light element. Dale
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Don't forget that the projectiles are a significant cost, especially the thermal protection needed for emergence into the atmosphere at 8km/s+. (The drag forces involved in that emergence also mean you might as well opt for a shorter, higher-acceleration catapult, because there's no way this puppy is going to be able to carry people anyhow.)
And unless you're launching to escape or nearly so, or catching the projectiles with an orbital electromagnetic accelerator, each one still needs a rocket kick stage to enter orbit, incurring much of the complexity and maintenance penalty of a pure-rocket vehicle.
Finally, don't forget to add a surcharge for environmental impacts of highly-hypersonic flight in the atmosphere. The beanstalk wins big in that department by entirely avoiding combustion and high-speed atmospheric flight, and by being able to send things down as well as up.

There's no question that unless and until the required material becomes non-imaginary, the beanstalk is not a contender at all.
As for construction, almost certainly the cable would be unreeled in space rather than being built there. We've been unreeling multi-thousand-mile cables in hostile environments successfully for over a century. (The North Atlantic is in many ways more hostile than space.)
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Dez Akin wrote:

The payload will achieve orbital speeds in earth's troposphere?
Even if it were heat-indestructible, atmospheric drag would still steal its delta vee.
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Hop David
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Not if it's massive enough.
A gun system for launching people.
Take a 3m diameter gun.
Now, it accellerates the passengers (prone, along the diameter) at 25G, while submerged in water, for around 55 seconds, along some 330Km of barrel. Then over the last second, accelleration reduces to maybe 5G, and the passengers are spun vertically so that they are now facing backwards. Then the capsule exits the gun at some 12Km/s.
I'll guess that they'll have to pass through around 30 tons/m^2 of atmosphere in the first 3 seconds, so to keep decelleration down to 25m/s^2, the mass needs to be some 480 tons/m^2.
Call it a bar 30m*3m of tungsten, with space for 50 people, who want to get into space really, really fast.
On the plus side, there probably isn't much need to keep aircraft out of the flightpath, and you wouln't notice any noise pollution ever again.
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VH> proposes a closed loop as space elevator.
I am not sure what you mean, but similar ideas have been proposed. For example: - orbital ring, http://www.islandone.org/LEOBiblio/SPBI127.HTM - orbital loop, http://www.islandone.org/LEOBiblio/SPBI131.HTM - geomagnetic levitation, http://www.islandone.org/LEOBiblio/SPBI133.HTM (also recent thread in sci.space.tech "Levitating geomagnetic buckytubes")
The best newsgroup to discuss such ideas is sci.space.tech.
The only comprehensive technical reference is my Earth-to-Orbit Transportation Bibliography: http://www.islandone.org/LEOBiblio /
________________________________________________________________________
Uncle Al wrote:
UA> I am utterly amazed at the discourse here. I've seen a week of every UA> git and lout spewing dreams of idiocy based on an infinite supply of UA> zero-cost shitanium and unobtainium FOB geosynchronous orbit. UA> Physical reality doesn't work that way. Larry Niven's "Ringworld" is UA> a pleasant fantasy, though it does come up short when you submit bids UA> for 2.1 x 10^27 kg of scrith and 1.6 x 10^39 J to get it rotating.
I am rooting for you but wonder why you waste your time talking to space cadets about a foolish idea instead of discussing serious ideas in sci.space.tech.
________________________________________________________________________
We can greatly reduce the cost of space transportation without resorting to exotic contraptions. The Space Shuttle Main Engine is very expensive because it has 70,000 parts: http://science.ksc.nasa.gov/shuttle/nexgen/Guide_HRST_Design/gidedf20.htm
In 1968 an Aerospace Corporation engineer Arthur Schnitt and an Air Force colonel Floyd Kniss tried to replace the complex rocket launchers with the so called big dumb boosters. The initial experiments were very promising, but when the big shots learned about it, the program was terminated and both guys were silenced.
Most rocket launchers are made of three stages. Making a reusable first and second stage is easy if both stages are pressure fed rockets. Pressure fed rockets have strong propellant tanks; they are strong enough to survive reentry, splashdown, and handling on a bobbing ship.
Making a reusable third stage is difficult due to high temperature and high heat load on the nose cone and leading edges of the spacecraft's wings during reentry. Some people believe that transpiration cooling may solve these problems, but nobody knows how to fabricate such cooling system. Making a perfectly reusable third stage is not necessary to reduce the cost of space access by an order of magnitude because the last stage is much smaller than the other stages.
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The entire thread is ridiculous. Armchair buckytubes conduct electric current better than copper.
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Which still isn't anywhere near good enough to power a climber, not when the power has to be transmitted tens of thousands of kilometers through a cable with a very small cross-section.
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