Obayashi To Build Space Elevator By 2050

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 require tens of thousands of dollars of electric power for every launch. Meaning, a ticket to space would still cost tens of thousands of dollars just to launch the capsule + life support for yourself, plus supply capsules. Even though this technology would make it orders of magnitude cheaper than anything we have now, it would still be too expensive for a member of the middle class to routinely go to space.
3. If the laser array fails or has to be shut down RIGHT after lift off, the capsule will be moving too slowly for parachutes to work, and so it would plummet to the ground and kill passengers. One proposal is to use a simple steam catapault to launch the capsule vertically at a high enough velocity that parachutes can be used. Then, if anything goes wrong, you turn off the lasers and deploy chutes.
4. A cost effective system won't launch more than 1000 or so kilograms of payload per launch. You get the volume by doing many launches. This means that astronauts have to be launched one at a time in separate spacecraft that rendevouz in orbit. Large satellites have to be sent as several separate modules. In a few cases, this could pose a problem that cannot be easily solved, for instance spy satellites need a single mirror that may weigh more than 1000 kg alone.

With that said, the cost estimates I have seen say that for a mere 200 billion or so, at current prices, enough lasers could be bought to launch a space-shuttle load every launch.

Anyways, space elevators aren't ever going to be built, if a superior alternative like this is feasible.

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/zleGfkZGv_w/obayashi-to-build-space-elevator-by-2050

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