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Japan starts space elevator experiments

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Re: Japan starts space elevator experiments

#271

Post by chris_st »

jimmcslim wrote: post #250
djsumdog wrote: post #195

Earlier quoted context omitted.

Also the Mars Trilogy (Red Mars, Green Mars, Blue Mars) by Kim Stanley Robinson. Honestly that's my favorite Sci-Fi novel series of all time. Just give Red Mars a try and I prosome you won't be able to put it down.

Given a major plot arc in the trilogy was... (SPOILER!!!) ... the destruction of the space elevator by a terrorist organisation and the consequent destruction on the surface of Mars as the cable, released from its counterweight, wrapped itself around the planet... I’m not sure it’s a great example :-)

On extraordinarily rare occasions, mankind has been known to learn from cautionary tales.

Re: Japan starts space elevator experiments

#272

Post by leetcrew »

mojomark wrote: post #209
sigmaprimus wrote: post #162

I'm a bit confused the ISS is only 408km from the earth's surface so why would it take 8 days at 200kph? Unless they are including the speed of orbit in which case the earth is already rotating at 1600 kph. What am I missing here?

They said the tetger would be 36,000 km. 36,000/200kph = 180 hrs... 180hrs/24hrs/day = 7.5 days. Why the tether needs to be 36,000km long wasn't mentioned.

it's the height above earth's surface for a geostationary orbit.

Re: Japan starts space elevator experiments

#273

Post by hutzlibu »

jimmcslim wrote: post #250
djsumdog wrote: post #195

Earlier quoted context omitted.

Also the Mars Trilogy (Red Mars, Green Mars, Blue Mars) by Kim Stanley Robinson. Honestly that's my favorite Sci-Fi novel series of all time. Just give Red Mars a try and I prosome you won't be able to put it down.

Given a major plot arc in the trilogy was... (SPOILER!!!) ... the destruction of the space elevator by a terrorist organisation and the consequent destruction on the surface of Mars as the cable, released from its counterweight, wrapped itself around the planet... I’m not sure it’s a great example :-)

To be fair, the "terrorists organisation" was not called like this in the book and was just shown as one party in the war of independency from earth. And the elevator was controlled by earth and brought down earth troops who hunted down the resistance. So you can argue it was a valid military target ... terrorist(in my definition) target civilians. They just acted very rughless.

But I liked in the book, how it did not actually took sides, but just showed the implications of what violent struggle/war for independency on mars means for different sides. And mainly from the perspective of Nadia, the engineer who build things. And she sees everything just gets destroyed and smashed. (I got moved a bit by the memory)

Re: Japan starts space elevator experiments

#274

Post by tomp »

timonoko wrote: post #237

The Giant Space Wheel (of Seveneves) is so much more attractive than space elevator. That is a large mass on geostationary orbit having smaller pods rotating at the end of ropes. Those pods can be lowered to atmosphere and synchronized with earth rotation. Elevator pod comes down and can stay down maybe couple of hours and then jerked back to heavens. All energy comes from the sun - collected at the center station. S…

Another inteersting idea is an orbital ring - basically a rotating cable around Earth in LEO, which is accelerated by a maglev-train-like platform. The platform travels "along" the ring at high speed, but it can be made to stay "at one place" from Earth surface perspective (i.e. geostationary). The cable ring is rotated at orbiting velocity (or higher), so the centrifugal force counteracts gravity, keeping it in place.

Re: Japan starts space elevator experiments

#275

Post by andrewflnr »

zepearl wrote: post #82

Thinking about a "counterweight" orbiting a planet to which it is connected by a cable: as the cable offers resistance to the planet's atmosphere, and as the planet's atmosphere is active/changing, the "thing orbiting" would still have to have an excellent aerodynamic shape to survive the planet's atmospheric effects, right? (as e.g. the lower part of its cable would probably soon or later be "pushed" by winds theref…

Geostationary orbit is really high. To say that it's well above the atmosphere is a huge understatement. If your counterweight gets anywhere near the atmosphere, it's already dead, everyone aboard is dead, the elevator is dead, a fair chunk of the earth's surface is dead, etc.

Re: Japan starts space elevator experiments

#276

Post by yogthos »

snowmaker wrote: post #160

It's unclear to me if this is real or the continuation of a publicity stunt from Obayashi (who has been getting press about their plans to build a space elevator for years). I'm as excited about the theoretical concept of a space elevator as anyone. But the problem remains that no one can produce a cable even close to strong enough. This article has a good description of the material science problem: http://www.space…

A space elevator seems like a much better concept for the Moon. If we could make a permanent Moon base with a space elevator, then it would be possible to use materials from the Moon to assemble things in orbit. Such a base would make it possible to start exploring the rest of the Solar system in earnest.

Re: Japan starts space elevator experiments

#277

Post by twic »

theothermkn wrote: post #117
jandrese wrote: post #110

Earlier quoted context omitted.

The problem is how you keep the tether from dragging behind the orbit when you do that. Space elevators require a fairly delicate balancing act to keep the mass directly over the base of the elevator, otherwise they turn into giant slings.

The center of mass of the cable-counterweight system orbits at geosynchronous height. Also, the gradient of gravity will Stabilize the attitude in the desired orientation. None of this should be construed as an endorsement of space elevators, though. They will never happen on Earth as it exists now. Over and above the material science, you have to clean out LEO of all satellites before you even start construction. It…

Could i interest you in a sling-on-a-ring architecture?

https://arxiv.org/abs/1505.07424

You build an orbital ring above the altitude of the LEO satellites, use non-synchronous skyhooks to pick up payloads from inside the atmosphere at an altitude that can be efficiently served by aeroplanes, and then fling them the rest of the way to geosynchronous or interplanetary transfer orbits by accelerating them along the ring.

Re: Japan starts space elevator experiments

#278

Post by camtarn »

tripzilch wrote: post #264
codethief wrote: post #257

Earlier quoted context omitted.

While total angular momentum is certainly conserved in any rotationally invariant system (read: Earth + space elevator + objects traveling upwards + atmosphere), the situation only for an object traveling to space in the elevator is different: Angular momentum is given by L = I * ω where I is the moment of inertia and ω is the angular velocity. Let's assume that we put the internet ( https://m.youtube.com/watch?v=iDb…

> Let's also say that the internet has a mass m silly, the Internet doesn't weigh anything! ;-)

https://www.telegraph.co.uk/technology/internet/8865093/Inte...

That's from 2011. It probably weighs at least one watermelon by now, given Netflix etc.

Re: Japan starts space elevator experiments

#279

Post by roryisok »

timonoko wrote: post #237

The Giant Space Wheel (of Seveneves) is so much more attractive than space elevator. That is a large mass on geostationary orbit having smaller pods rotating at the end of ropes. Those pods can be lowered to atmosphere and synchronized with earth rotation. Elevator pod comes down and can stay down maybe couple of hours and then jerked back to heavens. All energy comes from the sun - collected at the center station. S…

Seveneves is a great read!

Re: Japan starts space elevator experiments

#280

Post by on_and_off »

breatheoften wrote: post #106

I saw a bunch of people throwing out good sci-fi space elevator examples and had to drop a reference to the space elevator in Neal Stephenson’s Seveneves. The descriptions are epic and do a good job of giving a real sense of placiness to the result of truly enormous engineering.

Then let me drop a reference to Sundiver by David Brin, which is the start of the uplift cycle.

The elevator is by far the least interesting idea of these novels which center about a future where we have uplifted (given sapience) monkeys and dolphins. We are also trying to survive in an unkind universe where Earth is a third world political power that is making religious fanatics angry.

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