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.
Even that number is rather too high; it would be more like $0.02/kg if you were using it in sufficient bulk to justify your own LOX plant. The raw material, after all, is air...
Yes, liquid hydrogen is fairly costly, not least because it's made from petroleum... (And the manufacturing process releases quite a bit of CO2 into the air, too.)
Yes, that makes a big difference.
Even with hydrocarbons, the fuel pretty much dominates the cost. LOX in bulk is almost free by comparison.
Dear Henry Spencer:
Sprites have been seen to 60 miles in altitude, and that is without a "lightning rod". Other than not having any one carbon fiber contacting any other, there isn't much you *can* do. Then there goes your strength.
David A. Smith
No, it's made from natural gas, mostly.
Paul
Oh dear. Sorry all, typo. I meant $10. Should not post when tired.
There's lots you can do. Failing all else, you can probably just switch to Kevlar for the bottom 100km. It's only carrying its own weight, plus dynamic loads and cable tension -- it doesn't *need* that much strength.
Making the bottom 100 miles out of kevlar, or whatever is not a big problem. The only reason that nanofiber materials are needed is the huge taper implied if you tried to use conventional ones. For example, making the bottom 100 miles out of kevlar would only (about) double the total mass. If you tried to do it along the whole length, you'r looking at billions of times.
Noodling around, it looks like a guesstimate of $0.20/litre isn't too far off and with a density about 0.7x water, that makes it very roughly $0.30 per kg.
ISP of about 300, so m/r to orbit is about 14, so for C12H26 + 12.5 O2, the C12H26/O2 ratio is about 17/20 but since this is strictly BOTEC, we'll call it 1:1. Each kg of dry mass in orbit had 7 kg of C12H26 @ $0.30 and 7 kg of LOX @ $0.02 for a total of about $2.24/kg of dry mass. Say the equilibrium price for Ultimate Rockets is x5 the price of the fuel (planes are x3, I think) and that each kg of payload is but 1/10th of the dry mass and so each kg of payload is priced at $122/kg. Not bad: my massive ass could be put in orbit for about $8,500.00 or slightly more if I wanted to breathe while I was up there.
Earth-Mars, call it 15 km/s delta vee, add in 10 kg/day of supplies to be pessimistic, for six months, for a m/r of 150, and a payload of 1870 kg, or about $300K if I have not multiplied incorrectly. The price goes up a bit if I demand frills like a re-entry vehicle, of course. And I have not budgeted for supplies to be used -on- Mars, possibly a problem. Like Franklin, I will have to rise to the occasion.
No, I think you've forgotten that O2 is 32, not 16. C12H26 + 12.5O2 is a mass mixture ratio (oxidizer/fuel) of 2.35, which is around optimal for LOX/kerosene (depends somewhat on engine details).
If you've got a variable-expansion-ratio engine, you may want to go rather leaner -- most of the ascent is in vacuum, and for the high expansion ratio that you want to use there, mixture ratios around 2.9 are better. Higher mixture ratios are also denser, which reduces structural mass, so you may want to bias the mixture in that direction even at the expense of a bit of engine performance. The Ultimate Rocket might end up around 3.0.
As above, it's about 10kg of LOX plus 4kg of kerosene, $1.46/kgdry. At a ratio of 3.0, it's $1.22/kgdry.
Airline numbers depend on exactly *when* your data comes from; x3 is commonly quoted but may be a little optimistic. However, rockets ought to be better, not worse! Most of the costs aren't proportional to fuel -- magically tripling the fuel capacity of an airliner would not triple its operating costs -- and rockets are far more fuel-intensive than airliners. Max Hunter thought 1.2x ought to be feasible, long term, for reusable chemical rockets.
That you can undoubtedly double, at least. If memory serves, payload was about 1/6 for the DC-Y design, *with* the dry-mass overheads of LH2 and
*without* nanotube-material structures. I'd say the Ultimate Rocket is going to be at least half payload.With my somewhat-more-Ultimate numbers :-), it's $2.93/kg.
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.
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
Whoops.
Uh, I was just making sure everyone was reading carefully (That's gotta work some time).
clip bad assumptions.
Cool. So sending me to the antipodes would cost less than a hundred bucks (Much less, because delta vee is much less than to orbit)? I see a beautiful future for tourism.
Kevlar is not impervious to ozone, gets screwed up by UV, loses some of its desirable properties in the cold, shrinks and expands with temperature (a lot more than nano-tubes). Kevlar is not a solution, but an extension of the problem. It is at least, non-conductive, and the ozone and UV can chew on a coating for a while.
David A. Smith
Natural gas is just very light petroleum, light enough to be a gas at normal temperature and pressure.
Marc
Kevlar was just an example, picked out of the air, of a current material that would be suitable from a strength point of view. There are quite a few others that may be suitable, if the conductivity of nanotube stuff is found to be a problem.
This is the key.
So much of this argument on Beanstalks is "Picked Out Of The Air".
We have had functining free electron lasers to push the cargo up the stalk and other fantastic things "Picked Out Of The Air"
We need to hold these discussions in :
Sci.Fiction.Materials and Sci.Fiction.Space.Policy or Sci.Fiction.Astro
wrote:
The issues of zero thermal expansion, non conductivity, resistance to ozone (and monatomic oxygen), and light is a null set of members. Purportedly carbon nanotubes can be made non-conductive. Whether this can be done in bulk...
Personally, I'd like to see a magnetically-powered cannon stretch west-to-east across the USA, and launch payload into space from an end elevated 4km into the air. Evacuate the tube, and "blow" compressed gas in the direction the payload would head... but no 3g limit upon striking the atmosphere I'm afraid.
David A. Smith
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.)
Why zero thermal expansion? And the bottom 100Km/miles could be almost trivially replaced anyway, it's of negligable mass compared to the rest, and one car could easily take it up, lower a new one, and unhook the old one.
VH> I have been wondering for a while why nobody 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,
The best newsgroup to discuss such ideas is sci.space.tech.
The 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.
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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:
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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