Not really. There's little evidence of that. Low cost access to space is to do with using less people per kilogram.

That's pretty arguable. The figures I saw were nearer twice that.

Sea Dragon was LOX/Kero though. Also, note that they minimised launch pad costs/salaries by launching from the sea. And there are difficulties with very large launch vehicles like Sea Dragon- the bigger engines tend to be prone to combustion instability due to the lower acoustic modes you get and injector issues. Development issues tend to raise the launch price because it pushes up the development cost.

SeaLaunch uses LOX/Kero, and that's fairly cheap. And there's reasonable evidence that the Russians (that mostly use denser propellents not particularly hydrogen) are sandbagging with their prices right now- they are probably down to around $500/kg with their costs on say, Protons. But with the rest of the world expensive and not making much profit- what would you do in their place? Me I'd raise my prices and make profit.

Apart from physical damage to one cable, I think you're right. But don't underestimate the vibrations that can be set up- and no two cables are ever going to be 100% the same.

Hopefully.

The main problem in general would be transverse waves; or even worse, helical/skipping rope oscillations- they give the cable a constant length and so may not show much damping at all- the cable may be engineered to damp fairly strongly longitudinally, but transverse/helical/skipping rope I have no idea about- although giving the elevator 'thickness' by having multiple cables is probably a good strategy.

Current flowing along both/all the cables will cause them to pinch together. That's one potential problem. Putting a small current along each cable in opposite directions could be good, since it increases separation. Also, putting a small static charge on the cables could help.

But ultimately, damping needs to be in the system somehow, otherwise all we've done is generate the worlds biggest double bass.

Yes, but the cranes cables are probably very heavy, short(ish), very strong and not particularly high friction.

The space elevator is literally thousands of times as long and incredibly flimsy. Any rubbing contact can cause friction, and it wouldn't surprise me in the slightest if that small friction, acting over the length of the cable didn't preclude rotation for loads that the cable can actually handle.

But I'm probably being paranoid; it's probably fine, but my deployment doesn't in any way depend on friction being negligable, except at the pulleys, where it must be entirely non negligable :-)

I thought about that, but tangling is probably too great an issue- I think that it would just twist up during deployment, and then you'd *never* get the loops to move.

You might be able to do that, the pulley would need to be able to deal with different diameters of nanotubes, which makes them more difficult to build, and they would be initially heavier, since they have to be able to deal with the later heavier weight of the cables.

Ok, new deployment scenario:

a) deploy the exponentially tapered seed elevator using a rocket.

b) from the ground attach a pull-down ratchet climber

c) take a spool and feed it through a 'slack' device, through the climber, through a powered pulley and then through another 'slack' device and then feed it onto another empty spool.

(A 'slack' device is just a way of keeping *up to* a few hundred yards of slack length of cable, it has got pulleys and weights and stuff- you need two one on the down, one on the up, so you can briefly stop the cable to change the spools or join ends.)

d) turn on the powered pulley- the climber will climb dragging the fresh cable with it.

when the climber reaches high enough (a few thousand kilometers :-) ):

e) grab the end after it comes through the slack device, feed the end through another climber, and then join the two ends together so you now have a spinning loop through both climbers a few thousand kilometers long.

f) Remove the slack device from the first climber's cable

repeat steps c-e on the second climber (climbers will be climbing at the same speed up the cable with the loop in between.)

do it again with a third climber etc.

lather, rinse, repeat

Once you have the loops in place you can carry more nanotubes up the elevator to strengthen the seed cable. Take the thickening spool to above where you  are going to install it, clamp one end at the top, slide it down with the spool, clamp at the other end and adjust the tension so it is taking the correct proportion of the load.

Changing the mass of the loops/pulley can be done by sliding them all along one- adding another climber at the top or bottom and decommisioning the one one the end.

The problem with heavy lift is that you end up using it for everything, and that means you don't launch very often.

If you don't launch very often- it costs a lot- all of the standing armies' wages eat your lunch.

I'm interested in low cost access to space, so heavy lift, and particularly hydrogen fuel, doesn't do it for me. Each makes it expensive- and both together- more so.

It's like the SSMEs. It's not that it couldn't be done- it's more that it shouldn't have been done.

I just think that if you could launch small/medium payloads for very little, then the costs of constructing something in space goes way down. And where that really is uneconomic, then there's always some mug who'se fallen for the HLLV myth you can buy a one-off ride from :-)

The above calculation seems to be slightly pessimistic BTW- it neglects the reduction in potential energy caused by the rotation of the earth. (i.e. the weight of the object goes down faster as radius increases due to centrifugal force.)

It goes something like:

E = rotationalEnergyAtGeo - 0.5 m r^2 w^2

Where rotationEnergyAtGeo is such that E=0 there. w is the angular velocity of the earth in radians/sec.

But it's only a few percent I think so I haven't bothered to work it through.

We're currently a further 6x below even that. You could hope for a miracle, but I don't think you're allowed more than one miracle per project; we have to save that for the nanotubes.

The really sad thing is that rocket fuel is about the same cost. :-(

No.

If you have *specific* issues with the idea, then please outline them, otherwise, there are other threads you might be better contributing to.

Careful here.

A single fixed-width loop is weakest at GEO, quite a bit of the lift capacity is taken by the weight of the cable below GEO. This weak point limits the payload.

The staged loop elevator is an approximation to the exponentially tapered elevator, which is equally strong at all points; and for the same total cable mass can carry rather more payload- up to the weight of all of the carbon nanotubes over and above an exponential tapered cable.

Therefore a staged loop elevator can handle considerably more payload for the same total mass of cable as a single loop; however a single loop has easier and probably somewhat faster ramp up than the staged loop (unless I've missed a trick somewhere); so is better during construction.


There could well be a trick that makes it fairly easy. So far as I know nobody has ever tried to build something like this, so it's not a well explored issue.

Um, no. The electrical power necessary to lift something to GEO is 14kWh/kg. Let's say ~$0.1/kWh (fairly expensive by domestic standards, but you're probably going to have to build a special generator for the Space Elevator.)

Then, factor in the losses in the laser system: a factor of 50-200.

So, we're talking $50-200/kg cost in just electricity. That doesn't include the depreciation on the elevator or anything else.

So, if a person weighs as little as 100kg, that's $5000-$20,000 just for the electricity. In practice, you'd also have to ship life support and such like, so 200kg might be more realistic.

Then the Van Allen belts mean you have to add a load of shielding weight many tonnes per person. If the shielding is useful equipment that you need upstairs anyway, then there's no extra charge though.

Oh yeah, and that 14kWh is the theoretical minimum. In practice you have to add on friction and whatnot. So multiply by some number.

You can certainly do it, it's just fiddly. The few hundred kg limit really only applies to ground level, by the time you get up near GEO the weight limit is higher, and the g-force is much lower anyway. So you just ferry equipment up in few hundred kg batches to altitude and then assemble them up there using remote manipulators.

Actually, I thought about it some more last night. The single loop design is good at deployment, but has reduced payload capacity (or needs lasers), whereas the multi-loop design has better *payload* capacity and although it is certainly self-constructable it is rather harder to build.

So, combine the two: my latest/greatest plan involves starting using a single loop deployment. Then once you've reached the target mass you stop the deployment loop spinning, and use that to form the fixed cable down the center.

The multi-loop pulleys and loops can be deployed from the ground end near the end of the ramp-up of the main cable. There's still some awkward bits to work through but the overall concept seems workable.

I haven't worked out the optimum placing yet. A pulley near the ground has to be able to carry the payload you apply to it, and so itself has a mass attributeable to that, and the further away from GEO the more cable you have to install above *it* to hold *it* up. And then you add on top the mass attributeable to the cable. My gut feel says that more like 3000km or so might be a better compromise, but there could be reasons for putting it at as low as 300km- like tourism.

Probably the LEO-MEO is the worst part- very small space junk (flecks of paint for example) and micrometeorites cannot be mapped and will damage the SE.

Losing the low end of a beanstalk isn't any big issue anyway; you just catch the end and reconnect it. It's the best case failure.

It was a bit of a botch to be honest. One of the highly talented germans said: 'They've reinvented the wheel! And it's square!'. The cost of the Shuttle has never gone below the Saturn V cost. :-(

No. That actually should be 20:1 fuel mass:dry mass :-)

8:1 is suborbital.


Ah! An argument from incredulity!

An aluminum drink can has 20:1 payload to metal ratio, contains high-pressure liquid and costs pence. You can drop it, and it will experience 10s of gs, far higher than a rocket experiences, and typically without bursting.


"technology" is a very nebulous concept that really only applies to export regulations.

All I will say is that reliable rocketry has been demonstrated (tens of thousands of starts with no explosions), lightweight, robust tankage has been demonstrated. It's really just a question of lining up the existing stuff and finance and running a test program and doing it. The perceived risk is higher than the actual risk, which makes financing very difficult.

From the cost modelling I have done, the costs are probably roughly proportional to delta-v in this case. If it costs $200,000 for suborbital, $600,000 is about doable for orbital.


Who knows?
   

We don't know what would have happened since it never did. Quite a bit of fundamental research is done by rich amateurs, rather than governments, since they have money and time.


All that says is that defense budgets are big.

Its market was undercut by subsonic jets. The difference with orbital launch vehicles is that they are the only game in town.

Yeah, but the elevator cannot lift humans due to the Van Allen belts, and without lifting humans the orbital market is small, and growing smaller (note that fiberoptics is gradually replacing geosats for telecommunications). Right now it looks like the elevator needs space tourism, and that means rockets.

I would argue that the aerial tram case is more complex since the propulsion forces are at right angles to the suspension forces. You therefore have to deal with issues like the propulsion pulling the whole lot over, this can't really happen with a space elevator.


In what way? I tend to find that as the forces are aligned things are more efficient if anything.


In principle it is as simple as wrapping them around the same pulley, with grooves to prevent the cables snagging on each other. More complex designs can be envisaged, and the speed can be varied if the diameters are different, should this be desirable (it might be desirable to go more slowly lower down as this minimises pulley size for example; and faster through the Van Allen belts...).


Not directly accessible, but they are certainly indirectly accessible.


I see absolutely no show stoppers to doing so in fact. The system would need to be designed for building, but I certainly believe that it can be exponentially grown from the ground end.


Yes, so single loop elevators can be expected to have higher cost/payload ratios. That pushes up the price.

It's important to separate elegance and cost. Elegance is often not cheap. Single loop elevators are elegant, but other designs are probably cheaper. Cost is an important consideration- money is often the resource in shortest supply; although risk is often the property that curtails the supply.

You don't *need* a pulley at GEO, but my POV is that not having one is probably suboptimal- you're trading off expensive nanotubes for cheap counterweight and pulley.


It's a fun idea, but I can't see it working- it's extremely expensive on cable.


Yes, perhaps, depending on how heavy the pulleys actually are, compared to the untapered loop.

There's very probably no need for a laser to deploy the looped system. The initial rocket-launched mass is possibly higher, but the overall costs would still be much reduced, as would the long term costs.

My best guess is that this would be financially less efficient.