Well, I've got a big stack of e-papers from a rocketry email list I'm on where the general consensus is that it's been looked at an embarrassingly large number of times, and it's never made sense to date; and some of the papers go back to the 50s, and there's been nothing fundamentally new found at any point since then. Hypersonic aerodynamics work, but they're just inefficient for long distance travel unless you have a high-Isp engine. (Rockets engines are low Isp).

No, that's a basic research problem. Nobody knows how to do that at all, at any scale. Where is the lab version that you can put even 1 newton of load on anywhere in the world with the necessary strength/weight ratio? Never mind the tonne loads you need for a space elevator, and never mind the length.
$10 billion is only a seed cable isn't it? The $10 billion launch loop has an annual launch payload of 40,000 tonnes; and that's the crummy version. The $30 billion version launches 6 million tonnes per year.

Dynosaur was never intended to be a commercial transportation system.

If you know of a paper that says the economics work out for a commercial system, please let us know where it is, so I can learn how to do this; because I don't think that there are any.

I don't know where you got that from, it's nothing to do with the subject in hand.
Look, the basic physics works. It's just technical issues of stability and designs for the cars and power generation etc. The point is, if you like the Space Elevator, this does everything that does, plus more, and doesn't require wishium alloy.
My best guess is that Lofstrom isn't selling it right; didn't have the time I think due to his career, but I don't know enough about what he did or didn't do, but he's getting better at explaining it ;-). The big problem is that everyone kinda looks at it, and instinctively goes 'that will never work'; but when you dig into it there's nothing behind that instinct, it's just such an unfamiliar concept that people don't usually get it, and when they do, then it just seems so massive that it's totally outrageous. But really it's only an odd sort of cable- it's 5cm across. But it acts more like the worlds most powerful fire hose- so it's rigid as all heck. And everyday cables we're familiar with are *much* longer. The cabling in the Golden Gate bridge for example is sufficient to go around the world a few times; by many measures it *dwarfs* even *shames* a Lofstrom loop.
Nobody is saying it's really easy; actually it's at least $10 billion hard.

The difference is that the Lofstrom loop is just an engineering problem which can be expected to produce a working design, whereas the Space Elevator is basic research; which may never produce the goods.

And the figures for the Space Elevator are worse, not better. If the launch loop isn't being used, then it can be temporarily shutdown, and no costs then accrue (other than interest if the initial borrowings haven't been repaid). The startup costs for the elevator are higher by a factor of 2-4 or more, and the payload it can carry is smaller.

The logic behind doing packages is that they may not weigh very much, and don't require life support, so the fact that they cost $10,000/kg to send doesn't matter so much.
That's not the downside. The downside is that a rocket to go antipodal is about the same size as a rocket to go orbital. So the cost of the rocket is about the same. So the passengers would probably pay that bit extra and get 2 weeks of zero-g instead.
I've heard this a lot... but I'm not sure it makes any real sense.

Yes.
Yes.
No. We don't know how to make a cable-scale carbon nanotube tape that is suitable. There is no amount of money to do that right now.

But even if we could, I'm arguing that it's probably more expensive that way. CNT are very expensive compared to normal materials, and the occupancy time on an elevator for a payload is very long. That's really bad because it pushes up the $/kg.
No. A single failure gets easily covered by the stabilisation equipment either side. The loop just doesn't have time to go unstable in the 10+ microseconds it spends at any point of the ring. It takes far more than that.

In fact, it's the other way around, a failure anywhere along the length of a space elevator severs it.
No, actually there's no inherent damping of the fundamental, and you have to deliberately damp some of the higher frequencies as well. It's an upside down pendulum.
Yeah, right. I've seen the simulations, that's just not accurate. Basically a broken elevator tends to litter Earth orbit with lots of fragments.

A launch loop physically can't do that- the perigee of anything that comes from a launch loop is 80km, which is below the stable altitude- anything without a apogee kick motor is going to be reentering quite soon, or is at escape velocity; either aren't too bad.
Know how = technology, by definition. We don't have the space elevator technology yet, and we may never have it, and unless the CNT gets to be stupidly cheap, we may never have it for economic reasons.
I don't think you know enough to make that judgement. The more I look at it, the more practical it looks.

Everything in the world is prone to instabilities and failure though, but most things can be stabilised.
Um, actually the world record for electromagnetic accelerators is 50% faster than this (20km/s), and that's for a projectile, which are much harder to accelerate, because they spend such a short time in your gun.
This is more like a chain though- the particles are not independent.
Actually, no again, he's planning on using iron, because it's ferromagnetic, so he can manipulate it largely with conventional magnets. That way it doesn't necessarily take any current. And he can control the size of the turnaround points based on the capabilities of the magnets and the loop itself (IRC he has an 18km turnaround).

To get to orbit, you need to go sideways very, very fast. I fail to see how a 100km tall building would help you do that. This structure is 2000km long; and that's just to permit a long acceleration path for the launch vehicles. Also the cost of building goes up exponentially with height, so while in principle it could be done, in practice, economically a building that tall is very probably out of the question, and one 2000km wide is unbelievably so.

Trouble? Yes. Even skyscrapers are trouble. Everything in life is trouble.

But nobody has ever tried to build a dynamic structure so far as I know; but it seems possible right now given a normal amount of development.

At the moment, it's infinitely easier than a geostationary space elevator though, because mankind definitely doesn't know how to do that.

OK, here's a challenging idea.

Perhaps even if we had carbon nanotubes, an elegant design like the space elevator still wouldn't be the best system to build.

Consider- a CNT space elevator requires a long, long ribbon, and when a payload is climbing it, it prevents a second climber from following, for fear of snapping the cable.

Now, you can build the elevator stronger to compensate, but the cost/kg doesn't go down since you've doubled your payload and doubled your elevator; the CNT cable is likely to be expensive whichever way you cut it.

So that implies you need a system where the payload only occupies the system for short periods, which implies high acceleration. And that in turn means much shorter lengths are needed; but if you need a space elevator-like system to reach space, so there's a minimum of about 80-100km or so.

So.. launch loops. It's a magnetically suspended iron ribbon moving in a cable-like vacuum tube at above orbital speed which is projected in an arch up to 80km altitude, and you ride a maglev vehicle sitting on it and you're pretty much there really (a tiny rocket is needed to circularise your orbit).

It only takes a few minutes per launch, and then you can launch again, and that does wonderful things to the economics. The acceleration is 3g, which anyone can withstand, and it's below the Van Allen belts, so no radiation issues.

And it looks like they can be built today, the calculated cost/kg seems to be as low as $3/kg for the bigger systems, and the bigger system estimate (admittedly not an independent estimate) is for a total price cheaper than most of the independent estimates I've seen for even basic CNT space elevators.

So, maybe the elegant geostationary tether way isn't the best way?

Comments?

It's actually possible to use this effect with multiply looped elevator cables. Basically, a suitable pulley can redirect a moving cable back down towards the ground again.

Doing this gains thrust on the cable, and this can help offset the weight of the payload.

In effect the cable can "push-off" the ground-normally cables only hang down from GEO.

I did a bit more digging, and it's become a bit clearer.

To get from HEO (actually just barely earth escape orbit) to Mars requires a burn to put the vehicle onto a Hohmann transfer orbit. That's a burn of roughly ~2.5km/s. (Of course you don't need that if you get a tow from a beanstalk).

At mars, you enter the system at about the same velocity, and a burn of ~2.5km/s is needed to cancel than speed and enter HMO (High Mars Orbit). That's one way to do it.

The other way to do it, is to arrange to enter the Martian system so that you just skim the martian atmosphere. If you do it just right (and it's quite a narrow corridor) then you can burn off that excess 2.5km/s and enter Mars orbit. But if you miss, you go plowing into Mars, or back out into Solar orbit- where you'll stay for a *long* time- years.

Of course, as you fall towards Mars you'll gain quite a bit of speed, and you'll enter the Martian atmosphere going at about 6+ km/s. If that's what you meant by 'entering the martian system' then yes. But when you're up nearer Phobos and Deimos you'll be going much slower that that.

No, that's quite wrong. *Way*, way, way too high.

See:
http://www.angelfire.com/md/dmdventures/orbitalmech/DeltaV.htm

They don't actually list HEO to phobos, but check out the Phobos-earth return, just 2.88 km/s. That's actually nearer the speed that the vehicle approaches phobos from HEO.

I mean escape velocity for Mars is 5.5km/s- the transfer orbit from earth doesn't give you much extra delta-v relative to Mars, and you're only going to get 0.89 km/s falling down to phobos's orbit.

Incidentally, moving around the Mars system needs very little delta-v (phobos/deimos/martian elevator). I think a Martian elevator and quite modest rockets are all you'll need for quite a while.

Talking of conferences; is there a Space Elevator conference scheduled for this year?

Slight exageration, but yes.

That's not what I find. Whilst tensegrity certainly can make a structure more rigid, it does this at the expense of weight.

That kind of structure certainly would be very rigid. But, to the extent that the aerogel structural 'beams' aren't aligned with the force of gravity, it is wasted mass, and hence reducing the ultimate strength/weight ratio.