We were promised flying cars! We were promised holidays in space! We were promised floating cities! They said we would have evaporator rays! And personal communicators!

Well, one out of five. For futuristic stuff, that's not totally awful.

Flying cars are probably a bad idea, think of the accidents, but a lot of people would still like to go into space one day. Perhaps it's the awe inspiring view, the black inkiness of space, interspersed with unyielding pinpricks of light from stars that are uncountable light years away; the view of the epic wonderland of cosmic snooker balls so beautifully painted by the light of our sun as they pirouette around its nuclear flames.

Or is it possibilities of zero-g sex?

Yes, it's the sex let's be reasonable about this.

But whatever. Right now, all but the obscenely rich are stuck in the mud down here with the rest of us, being rained upon.

We need... to ... get... off ... this... dirt ball.

The only way to do this right now is the rocket. But rockets can barely make it; to reach the rim of the bowl we are in, our rockets must be built incredibly finely; so finely wrought that they often come apart on the journey to the heavens, leaving their final moments as a red smudge on the sky.

We cannot continue this way. We need a better way.

A launch loop would be that way.

How do rockets work anyway?

Normal rockets work by throwing stuff. If you throw stuff out the back of a rocket fast enough you go the opposite way, because when you throw it, it also (from Newton's third law) it throws you.

So, if you throw a lot of stuff sideways, then you end up going fast enough sideways that the horizon curves away from you at the same rate as you're falling and then you keep missing the ground and you're in orbit. That's what a rocket does.

It's that easy!

Unfortunately at the throw speed of any good rocket, the amount of stuff you need to throw is enormous, up to 20 times the amount of stuff you need to put into orbit; and most of that is the rocket, leaving only 2% of the takeoff weight for payload- that means you the guy/gal that paid plus your capsule.

How would a launch loop work?

The launch loop works in the same way; but with a big twist.

A launch loop would throw the whole Earth in one direction and the payload in the other.

Now, before you join the Society for ProtectIon of The Earth from throwing, you need to consider that a) the Earth is very, very, very big; and b) the thrown object is not very. Hence the Earth moves ridiculously little (duh huh- actually the same amount as if you had used a rocket), but the throweee moves a lot.

It turns out that that makes it all more efficient. When you throw rocket exhaust out the back the exhaust takes away energy, the energy flies out the back of the vehicle and is lost. Because the Earth doesn't do 'fly', no how, no way, most of the energy goes into the payload where you want it. With rockets it's the other way around, and ion drives are even worse, but I digress.

So what would it look like?

Basically, the way it works is that it's a long, very, very long (4000km circumference!) iron loop, laid out in a 28 km(!) wide, 2000 km long oval shape, but pinched down to a few inches across in the central portion. The iron loop is called a 'rotor' and it's contained in a thin pipe called a 'sheath' which doesn't move and contains a vacuum to avoid air resistance.

The whole thing looks a bit like a power cable, and would only be about 3 or so inches across. At each end of the loop are big, heavy magnetic bearings arranged in a rough semicircle, and there's lightweight magnetic bearings all along the cable so that the rotor can slide inside the sheath at incredible speed. Magnetic bearings are used because they have no top speed.

Initially it's all lying on the ground stationary, and then the rotor is powered up, and starts to rotate around the loop, and as it does so the cable starts to go taut.

The rotor goes along the 2000km cable, turns around at the bearings and then goes back the other way along a separate 2000 km cable, turns around again at the other bearings; it just goes around and around.

Now, there's a 300 MW power station, and it feeds power into the rotor through a linear electric motor, and as it does so it speeds up, faster and faster.

When the rotor gets to a certain speed, a bearing near the turn around bearings comes into play- it deflects the rotor up in an arc, a bit like the arc a water jet often makes. Because the rotor is going fast it has momentum, and it carries the sheath with it; it goes up, it comes down again a short distance later.

And then they feed in more juice, and as they do so, the arc becomes longer and higher. As it goes higher it is shaped by cables attached to the sheath, and when it reaches, get this, 80km height, then it tops out. As the speed climbs, more of the cable rises up, until eventually the full 2000 km length is up at 80 km, except for a few tens of kilometres of length at the two ends.

Isn't that rather high? What holds it up there?

Yeah it's rather high. ;-) More than 80 times the height of the tallest current buildings.

Mostly it's held up by its own shear coolness! But there's no true magic. It turns out that the rotor is faster than orbital speed, but that's not why. The weight of the sheath is held up by the lift bearing as it tosses the rotor upwards in a parabolic trajectory, so the whole of the weight of the rotor and the sheath is sitting on the lift bearing, which in turn rests on the Earth. It's just like a fountain, except the stream here is iron, not water.

But what's it for? And why is it so long?

It's a hypersonic acceleration track, so it needs to be high to avoid atmospheric drag which would tend to melt your spacecraft, and even if it didn't melt, air drag would slow it down tremendously.

To use it, you would get carried up to the track on an elevator, and when you get there you are loaded into a spacecraft.

Then you push a button, and a magnet underneath applies a magnetic field either side of the cable; which squeezes on the fast moving rotor. The rotor emits a magnetic field due to eddy currents, and the eddy currents drag you along the cable at high accelerations (about 3g, which even your granny wouldn't have trouble with, it's just an extended amusement park ride), as well as keeping you floating a cm or so above the cable sheath. It's an entirely passive, powerful, safe levitation and acceleration system all in one.

After about 4 minutes of acceleration, you're 2000km away from where you started, and you're at orbital speed, and the spacecraft releases itself, and you're in orbit! No fuss, no rocket fuel, quick, quiet and fairly smooth.

Or you could just use it as a fast way to get to Australia from America if you wanted to.

Is it safe?

Of course not! Not entirely anyway! Nothing that involves moving, including getting out of bed in the morning, driving, flying or breathing is entirely safe. The rotor would have a very, very large amount of energy in it, about 1.5 petajoules. That's equivalent energy to 350 thousand tonnes of high explosives. That's about the same as a small-medium nuclear bomb(!) But no radiation. Oh, and the explosion would last several minutes, so would be much less devastating, since it would spread out over time.

So if something was to go wrong and the rotor was to escape from its magnetic bearings there would be a big explosion, and you wouldn't want to be nearby at the time. So the intention is that a launch loop would be built at sea, for this reason.

However, apart from the sheath falling from 80km (probably on parachutes), the structure is so unbelievably huge that it very probably wouldn't be very damaged; the owners should be able to replace the damaged sections and just start it back up again. And if you were launching at the time when it exploded, you'd have a fairly good chance of survival; you're in spacecraft that can survive reentry, and you could detach and fly down.

How much, when can I go?

One version would cost about $3/kg. A capsule to hold one person would be about 1000 kg, so we're potentially talking $3000 for a person to get to orbit. Including profit and so forth, the price might go up to $10,000; but it would vary. That's about 1000x cheaper than the current rocket launch price.

The actual construction costs vary between $10 billion and $30 billion. The system can launch many tens of thousands of tonnes into orbit; far more than conventional rockets, and much, much cheaper.

It's all rubbish! It's science fiction!

No, it's possible to do this, modern technology can do this, the problems are persuading people to stump up the money to do it, there's nothing that mankind doesn't know how to do (unlike the Space Elevator.)

I like the space elevator better!

You do? But the space elevator is currently impossible to build, the cable needs to be too strong for the current materials. A launch loop is build-able, is cheaper to construct, launches more often (every few minutes, whereas the space elevator launches every couple of hours or so), has lower payload costs (mainly because it launches more often) and takes far less time to reach orbit.

Also, the space elevator goes right through the Van Allen belts, which are belts of nasty radiation around the Earth, and worse, it goes slowly, just 200km/h. The space elevator would give you a massive dose if you rode it, (even before you had sex on orbit) and you can't get off the elevator in low earth orbit because you would fall down to the ground; the space elevator only reaches orbit at the Clarke orbit at 38000 km. You wouldn't die from the radiation, or get immediately ill (but the dose is close), but your chances of getting cancer would go up considerably and that's why the elevator is intended only for freight.

The launch loop has no such problem, because it reaches orbit at 80 km, it can put you into low Earth orbit, or lunar transfer orbit. You would still go through the belts, but much, much faster, and so the total dose is much lower (similar to a dental or chest X-ray). So the launch loop is much safer!

The space elevator is an elegant system, but not practical for humans until the elevators get to be very big, and they would still be a very slow way to go to space.

So what can it do for me?

You could go into orbit for a holiday, you could go to the moon for not much more. If you have a few years, you could go to Mars, the costs are not outrageous. It's the real deal!

The launch loop could well be the future of space travel- your future holiday destination!