Obayashi To Build Space Elevator By 2050

mattr writes "Japan's Obayashi Corp. has announced plans to build a space elevator by 2050. They are famous for wrecking skylines with the over-sized bullet train station in Kyoto, the world's tallest self-supporting tower Tokyo Sky Tree and just recently, the beginnings of the Taipei Dome. It will take a week at 200 kph for your party of 30 to reach the 36,000-km-high terminal station, while the counterweight [swings along at] 96 km high, a quarter of the way to the Moon."

Comments

Does anyone feel that this is a good concept?

[ShooterNeo]

Look, ultimately you can't know if a technology is a good idea without actually building the tech, full scale, and spending the time and money to create revised versions to fix the major problems.

After you do that, some technologies are still a dog, no matter how you try to hide it. Nuclear power is an instance of that : sure it works, but the risk of catastrophe overshadows everything, and means that if you try to build and run a reactor everything costs too much because of the dangers. In the long run, nuclear is not feasible because other technologies will keep getting cheaper.

I feel a space elevator is a dog for a similar fundamental reason : there's one 36,000 km high structure.

Any serious failure to a manufacturing defect along 36,000 km of cable, and you lose every last dime invested in the project. (not to mention the falling cable might cause some nasty problems). If someone ever wants to attack a space elevator, it's a perfect terrorism target. One homemade cruise missile (in 2050, I suspect making a cruise missile won't be much harder than RC airplanes are today. Heck, some garage tinkerers already have done similar projects) and the ENTIRE elevator falls.

Not to mention laser fire, railgun fire, bad weather, etc etc. There's a lot of things and it only has to fail at one point.

Furthermore, you have to complete the elevator project before it is worth anything. Invest all that money to FINISH the cable, you can't get incremental results. And this multi-billion dollar structure (realistically probably hundreds of billions) has a rather limited cargo capacity : one load of passengers a week is NOT a rapid movement to space.

So, no. It's an idea that has somehow gained traction, but it is most likely a non-starter.

I propose a much simpler idea : rather than use lasers on the ground to transmit power to the elevator climber car, scale up those laser arrays a few orders of magnitude to the point that they can vaporize propellant off the bottom of the spacecraft. Pulse the beams right, and planar shockwaves will be created, giving net thrust without any kind of nozzle.

Advantages :
1. Ablative Laser propulsion doesn't require anything in the spacecraft in the way of aerospace hardware but a small instrument package to report attitude and accelerations back to the ground. Gyroscopes for stabilization would be nice, but not essential.
2. If a laser module on the ground fails or wears out, the launch continues..10 or 50% redundancy is entirely feasible.
3. You can do one launch every few minutes, assuming you use LED diode pumped fiber optic lasers, and have sufficient cooling capacity to remove the waste heat and sufficient power generation. That could be a metric ton or so to orbit every 15 minutes, 24/7, 7 days a week.
4. You do 1000 or 10,000 unmanned cargo launches before you send the first man up in a spacecraft identical to the one used for cargo (well, with life support inside, but identical flight hardware). This kind of sampling size allows you to honestly evaluate the safety of the system. In the event of a problem, you turn the beam off instantly and deploy parachutes. (such as beam heating of the side walls or something). No rocket to explode.
5. Each spacecraft will be extremely cheap, just a block of an inert solid bolted to the bottom, and a small instrument package (an iphone has all the circuitry needed, although of course you would use more sensitive accelerometers) and a radio. Obviously, some kind of orbital maneuvering system is also needed, but you can get to orbit without it.

Disadvantages :

1. Reflected beams from the lasers might cause problems for observers on the ground. Might have to create a large exclusion zone around the launch site, with air travel forbidden in a large radius. Not a big deal, tons of places in the Arizona desert. Still, with so many people involved, it seems likely a few people would be blinded if the lasers used were visible light.
2. It would r

Re:Does anyone feel that this is a good concept?

[Anonymous Coward]

A few corrections.

1. The cable is permanently stretched by a counterweight at the 96000 km altitude. If you sever the cable 1 km from the surface, the bottom 1 km falls to the ground, the top 95999 km fly away and settle in an orbit around the Earth.

2. If you can manage to build a 96000 km cable, it should be trivial in comparison to build a protective sheath in the form of a 10-foot-thick concrete chimney surrounding the base of the cable up to the elevation of 5 km or so. That takes care of R/C helicopters, cruise missiles and 20mm rifle rounds.

3. With the first space elevator in place, it is relatively straightforward to use it to build the second elevator next to it. You hang a horizontal platform at 36000 km, you start hauling up sections of the cable, and you grow the second elevator in place in both directions at once, until one end reaches the surface. Assuming that you can produce the cable cheaply enough and that you know how to weld sections of the cable without jeopardizing tensile strength, soon you will have two cables, then five, then twenty ... The hard part is to get the first one up there.

Bring it on

[arcite]

I'll be in my early 70's, hopefully still alive...

Where will they build it?

[Chrisq]

My understanding is that it will have to be the equator, which gives them a choice of Ecuador, Colombia, Brazil, Sao Tome & Principe, Gabon, Republic of the Congo, Democratic Republic of the Congo, Uganda, Kenya, Somalia, Maldives, Indonesia and Kiribati. Or maybe they're going to build an artificial island and port, I would imagine that's child's play compared to the elevator itself.

"Running costs are negligible"

[Kupfernigk]

I would really want evidence for that. The power demand is not stupendous - though the electrical losses in a 96000km cable are not going to be that small - but the cable itself is going to be subject to what can best be described as interesting stresses and environmental conditions, especially up to the end of the stratosphere. Then there is the consideration of how easy it would be to destroy with even quite a low tech missile, which means that protection could be very, very expensive. Getting investors to sink huge amounts of upfront money into something that may have an unexpectedly short and fatal lifespan is going to be a challenge; nowadays even the US military budget would be stretched.

Vandalism, terrorist or not, and theft are probably the biggest issues. Carbon fibre hasn't taken over for the cables of suspension footbridges for just that reason.