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Skyhook Robot Passes 1000 Foot Mark
JhohannaVH writes "MSNBC.com is running a story about yesterday's successful test of the Space Elevator!! Maybe it will become a reality after all." From the article: "This week's testing involved a 12-foot (4-meter) diameter balloon. Safety lines held by team members kept the balloon from floating away. The ribbon dangling from the balloon was made of composite fiberglass, with the robot lifter running up and down the tether ... During the day, the highest altitude reached by the balloon/ribbon/robot combination was 1,000 feet (305 meters). 'It gives us complete confidence that the mile goal is well within reach,' Laine said. Laine said that the Federal Aviation Administration has been very supportive and helpful in orchestrating their test flights. "
I've always wondered what keeps the orbiting counterweight of a space elevator in orbit. If I start to climb the elevator, don't I pull it down? Does it need some sort of thruster to keep it up? How come pulling myself up and counter-thrusting at the top uses significantly less power than just thrusting up from the bottom?
I mean, it's all very well and good that CNT's may be able to THEORETICALLY provide the strength necessary for the cable, but you know there's always this annoying discrepancy between theory and practice. Afaik, they still haven't achieved the necessary strengths in lab tests.
File under 'M' for 'Manic ranting'
The climber is trivial, compared to the cable. Wake me up when they have a cable that can hold 100 GPa and is longer than a millimeter.
Human genome = 3 billion base pairs = 6 GBit. Windows + Office = 20 Gbit. Which is more impressive?
Well, it's hugely less expensive on a $/lb-to-orbit basis to hook your payload to a reusable electrically-powered lifter that crawls steadily to GEO over a week or two than to put it on top of a high-performance, high-stress, complicated, disposable rocket filled with highly volatile fuels that is prone to catastrophic failure. The only rocket technology that could compete would be a fully-reusable SSTO, or maybe a ground-based-laser launch system.
Hmmm. I wonder about the "reusable" part. You'd need a "down" ribbon too, or some way for the lifters to pass each other on a single ribbon; otherwise the lifters would be one-way-to-orbit (where they would be raw material for other uses, of course...)
Uh yeah. There are existing buildings with elevators that go further, so I don't understand what the big deal is about this thing.
If you want to be rational about space elevators you have to face the fact that nanotube ribbons don't yet exist but ribbons made of materials like Dyneema or Spectra do. So what? Here's what.
Seastead this.
Hell, the Feds burnt though more than 20 million in Iraq this weekend.
Well, launch costs to GEO are $10,000+ per Kg. If you could move up a couple of tons at a time while saving two orders of magnitude on cost, that's economic viability.
From my limited understanding, the problem with a space elevator is essentially that the ribbon is kept tight (and under massive strain) due to it's length and the mass located out in space. So why not have a sequence of ballon mounted elevators (ie. one at 1000 feet, another from 1000 to 2000 feet, etc) allowing some slack in the ribbon? Once we get to a point where balloons are no longer feasible we can start using a real space elevator. The final "real space elevator" would no longer extend so far into the Earth's gravity-well and so is more easily built.
Create a SPACE PULLEY instead of Space Elevator. We can have a pulley hanging form space just above the atmosphere. The pulley hangs from a geo-stationary Space Taxi Station. A small Space Taxi is released up using a very very large helium balloons. A platform can be made that has large number of huge helium balloons below it. The Space Taxi is stationed on this platform before the whole platform is released. When the platform reaches to the limit that it rise up in the atmosphere, Space Taxi takes off form the platform using jets propulsion and quickly reaches to the hook of the Space pulley which is just above the atmosphere and hooks itself to it. After this the Space Taxi station just pulls up the Space Taxi. Note : All this is done with minimum fuel requirements compared to the other technologies, so what say ? Space travel cheaper than land travel say from India to USA ? PS. A compressor can be used to bring the balloon Platform back on earth.
Actually there is a project to use large balloons as heavy slow lifters. 1st stage balloon lifts the orbit balloon which uses an ion engine to get into orbit. It will take weeks to lift anything into space but it would be cheap and repeatable. http://www.msnbc.msn.com/id/5025388/
I would be curious to know how a power cable on a space elevator would interact with the Earth's magnetic field. Would it impart a significant force on the cable? Would the cable need to be shielded?
Indeed there would be interactions, there have even been plans, and some developments, in deploying long conductive wires ('tethers') from the shuttle to study this (and possibly generate energy from the tether crossing mag field lines). Up to now actual tests were not very successful I think (the last tether I heard about, a Nasa/Esa/italian development, catched fire during deployment)
But even more than this, I think adding to the wire the need to feed electrical kilowatts upwards and downwards would mean yet another constraining specification to a system that is already quite intensely constrained by the pure weight issue, and just this may be a show stopper.
I for one would confirm the 'laser feed' choice as the best one, even if this means a bit of pointing / tracking from ground.
Herve S.
The battery won't and can't "hold out". The thing is, current day rockets consist basically of 90% fuel-tanks and fuel, along with maybe 5% engines and 5% cargo. That's how much energy is required to get to orbit. Offcourse most of that energy goes into lifting fuel.
Batteries are atleast 2 orders of magnitude worse in energy/mass than rocket-fuel, and it gets significantly worse by the fact that batteries don't weigth less as they become decharged (a empty fuel-tank is ligther than a full one, nevertheless rockets jettison the empty ones and are multi-stage)
rocket-fuel could do it, with amounts of fuel similar to those consumed by a rocket, but then you hadn't really won much, had you ?
Current plans call for the climbers to be externally powered, perhaps by microwave or laser aimed at them from the ground. The energy delivered will go down as they get higher, but gravity decreases with the square of the distance to the center of earth too, so that works out ok.