Uses of Bulk Nano Materials (was beanstalks)

jbuch :

Funny, I am sure you said that before.

Earl Colby Pottinger

jbuch :

Good God man!! If you think it is crud why are you wasting your time posting?

Earl Colby Pottinger

Not everyone understands that you are talking about a gun projectile filled with rocket propellant. The projectile rendezvous with the rocket, docks with it above the atmosphere, and provides its propellant for the rocket. Solid propellant is not good because it would crack under the stress. Liquid propellant is better but the bottom of the projectile must be strong and massive to survive the enormous pressure of the gas gun. I imagine some kind of reusable sabot having massive bottom.

Orbital sling is easier to make than the long gun and its centrifugal acceleration is smaller than acceleration produced by the gun.

Last, but not least, a reusable, pressure-fed first stage of a rocket launcher looks pretty good. It is simple, cheap, and sturdy enough to survive splashdown.

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.

Granted, you technically can say what you will (related to Mat. Sci.) on this news group. However, can you please try to respond to discussions with some small bit of respect/inteligence?

Seth

p.s. If you do as recommended by me, I'm sure that some lengthy, scientific and productive discussion (right or wrong on anyone's part) will ensue.

Wouldn't magnetic storms induce strong currents along the whole length of the cable? You may need a few meters of kevlar every kilometer, all the way up.

I'd think the main cost is energy. That's why it's profitable to recycle alumimun, even though it's one of the commonest elements on our planet: Refining new aluminum takes lots of energy.

The raw material is (or could be) water. Just add energy.

But, liquefying LOX does not. All you need is the energy to cool it down to the boiling point, then to liquefy it. This is relatively small. Very large condensation plants can probably approach this.

Energy is not free. The cheapest way currently AIUI is to make it from natural gas.

That depends on what you mean by "cheapest".

Economically cheapest to purchase.

IMO, we should go to nuclear for electricity generation, and hydrogen would be produced that way. But some believe that nuclear is evil.

They might. I don't think this has been explored in detail.

Possibly, depending on how conductive our hypothetical nanotube-based material is. (It might not be very conductive; a good composite doesn't have the fibers themselves in contact with each other much.) I would hope it wouldn't have to be several meters every kilometer, because that might add quite noticeably to the cable mass. In general, doing *something* to the cable at intervals isn't a problem, provided the intervals are wide and the something isn't too massive.

And many believe that it is not economically cheapest to purchase.

For what? Assuming a conducting cable, what circuit will the current take? And remember that although individual carbon nanotubes of some types are good conductors, they are not necessarily in good electrical contact. The elevator will not be a very good conductor, it's resistance over significant distances will be quite high.

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.

"Perplexed in Peoria" :

Have you considered appling this idea to a non-tapered Rotator? It should help in using Rotators to move cargo to low orbits.

Earl Colby Pottinger

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.

Rotators strike me as a better idea than beanstalks. However, they may not be the best case for my pulley idea. Unlike a beanstalk which is lifting small masses up and down in the fashion of a continuous pipeline, rotators need to catch and throw fairly large masses at a time, with consequent big changes in tether tension. I'm not sure that pulleys are right for this regime. Furthermore, rotators can be used without much "elevating" at all. Catch at one angular position, release at another. Fine tune by shifting mass near the "hub". No need to shift mass near the tips.

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.)

yeah, it makes aluminium smelting completely pale in comparison.