Nice perpetual motion machine they have there! Are they actually serious?
I would expect that any tidal effects in a 40,000km long ring would rip it all apart. It would also be inherently unstable - any slight deviation from perfect will cause thing to do downhill very quickly.
How do people get the money and time to propose such things?It's not perpetual, it requires energy to keep the inner ring spinning. This is not about cheap, it's about what's possible with today's materials and known physics. Launch costs aside, it is still easier than a space elevator which needs a material longer than the distance to geostationary orbit with a cable with the tensile strength to make it that far.
This is why a space elevator is so appealing if some way can be thought of to make it a reality, the cost suddenly becomes affordable.
Of course it's appealing, but... the laws of physics are against it. It's not just finding a material that can hold up its own weight, how would you install it. You can't start at the ground and work upwards and you can't start in space and work downwards.
(maybe they can start from the top of a really tall mountain)
A rail gun in a really deep shaft might be a better idea for launching heavy stuff. With a rail gun a rocket could be moving at several times the speed of sound before it even needs to fire its engine. It's like taking away a whole booster stage from a conventional rocket.
But don't you think its a bit like not building steam technology because someone thought direct combustion technology was possible?
I would think all the knowledge accumulated of space logistics, control systems and materials would still be useful if fusion power was developed for space propulsion uses.
Quick back-of-the-head calculations, ignoring that the whole thing would be dynamically unstable...
- Carbon fiber density is about 2 grams per cm^3
- A 1m x 1m box section, with paper-thin (0.1mm) walls is about 5cm^2 in cross sectional area, so would be about 0.8 kg per linear meter. Call it 1kg per meter, or 1 ton per km.
- The earth's equator is 40,075 km - 40,075,000 m.
- The weight of a paper-thin 1m x 1m box section to go around the world is 40,075,000 kg.
- Falcon 9 can lift 22,000 kg to LEO, at a cost of $50M per launch. Assume that all of this payload can be used to build the ring.
- It will take ~1,800 launches, at a cost of $90 billion, to get the raw material for a 1m square paper-thin orbital ring into Low earth orbit.
Once it is built and you have 40,000 tons in orbit. You want to speed it up to support any wright that may be 'hung' from it.
Because centripetal acceleration is f=v^2/r, you have to move something 1.4x as fast to speed to double the acceleration/force. Low earth orbit is ~8 km/s, so this 40,000 ton paper-thin structure would need to be accelerated to ~11 km/s.
After all this work, each meter of of ring would only be able to generate 1 kg of 'lifting' force. It it is at altitude similar to the ISS, the lifting force from 400km of ring would be needed to support the weight of a 400km box section that touches the ground.
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Quick back-of-the-head calculations, ignoring that the whole thing would be dynamically unstable...
Quick back-of-the-head calculations, ignoring that the whole thing would be dynamically unstable...
- Carbon fiber density is about 2 grams per cm^3
- A 1m x 1m box section, with paper-thin (0.1mm) walls is about 5cm^2 in cross sectional area, so would be about 0.8 kg per linear meter. Call it 1kg per meter, or 1 ton per km.
- The earth's equator is 40,075 km - 40,075,000 m.
- The weight of a paper-thin 1m x 1m box section to go around the world is 40,075,000 kg.
- Falcon 9 can lift 22,000 kg to LEO, at a cost of $50M per launch. Assume that all of this payload can be used to build the ring.
- It will take ~1,800 launches, at a cost of $90 billion, to get the raw material for a 1m square paper-thin orbital ring into Low earth orbit.
Once it is built and you have 40,000 tons in orbit. You want to speed it up to support any wright that may be 'hung' from it.
Because centripetal acceleration is f=v^2/r, you have to move something 1.4x as fast to speed to double the acceleration/force. Low earth orbit is ~8 km/s, so this 40,000 ton paper-thin structure would need to be accelerated to ~11 km/s.
After all this work, each meter of of ring would only be able to generate 1 kg of 'lifting' force. It it is at altitude similar to the ISS, the lifting force from 400km of ring would be needed to support the weight of a 400km box section that touches the ground.
-I don't think the idea is to shoot everything up there from Earth. There's plenty of stuff up there without insane launch costs. Not needing to go through an atmosphere and escape a somewhat deep gravity well makes a huge difference.
This is not restricted to space missions. Looks like nothing much get people excited over great human achievements anymore. Except maybe the FIFA world cup.A lot of the need for fantasy imagination has been removed from the population since the Apollo days. These days people can sit down in front of a 50" screen and see almost anything without the need to fill in any details mentally.
Still doesn't help.
Moving something in orbit uses non-trivial amounts of energy. As an extreme case, something that is in Polar orbit needs all it's momentum moved into a different plane, and that takes more energy than getting something into orbit from a standstill. Likewise dropping something down from a higher orbit needs to have the excess kinetic energy removed.
As an example, once in orbit a 110,00kg Space Shuttle Orbiter with 21,660kg of OMS fuel would use it all (including the stuff it needs to deorbit and come home) to change the orbital inclination by around 3 degrees.
So using space junk is more of a fantasy than actually launching stuff.
Changing inclination is relatively expensive, especially when done at higher speeds. LEO is rather high speed in that regard. Higher orbits are much more efficient. Once you're up there, getting around is much easier.
As an example, once in orbit a 110,00kg Space Shuttle Orbiter with 21,660kg of OMS fuel would use it all (including the stuff it needs to deorbit and come home) to change the orbital inclination by around 3 degrees.
So using space junk is more of a fantasy than actually launching stuff.
Changing inclination is relatively expensive, especially when done at higher speeds. LEO is rather high speed in that regard. Higher orbits are much more efficient. Once you're up there, getting around is much easier.
what if you made a giant reel of the carbon material so it can be pulled up to orbit slowly? is this feasible at all? like unraveled. Then you would not need high peak power, only some thursters to prevent your construction platform from being pulled down?
https://en.wikipedia.org/wiki/StarTramhttps://en.wikipedia.org/wiki/Launch_loopQuoteFor $30 billion, with a larger power generation capacity, the loop would be capable of launching 6 million metric tons per year, and given a five-year payback period, the costs for accessing space with a launch loop could be as low as $3/kg.[5]
The only comparable technical change that has occurred in the fifty years since is the microelectronics revolution. Which when you get right down to it isn't all that exciting. You can replace stop motion animation, be bugged on the phone at all hours, and type your own documents instead of having a professional do it. You can listen to music in your car and watch TV at home in higher and higher resolution so you can see a higher percentage of advertisements done in higher resolution.That's a bit unfair isn't it? People now walk around with super computers in their pockets, wirelessly connected to a global international data network, there are self driving cars around the corner, etc.
Medical science has made lots of breakthroughs, DNA sequencing of the human genome for example, we are beginning to understand how the cells work on a molecular level which opens up the possibility of curing cancer etc.
Maybe not as amazing as it was back then, but some things are pretty exciting now as well.
The vast majority of those pocket supercomputers are running Facebook, Instagram and YouTube, while the two way wrist radio that effectively is transmitting and endless stream of natter.
The global data network has enabled, not quashed the various anti-vaxxers, flat earthers, Holocaust deniers and the like.
Is it really exciting to gossip with people all over the world instead of just those in your neighborhood? Except for weirdos like us who don't find similar interests locally.
As an example, raw natural gas is pumped using pumps that are essentially milled from solid blocks (of about a cubic meter) of monocrystalline aluminium; not cheap. It is reasonably resistant to the corrosion (there's all sort of corrosive gases and gunk in the raw natural gas), and its lightness allows the turbine to rotate at high RPMs without tearing itself apart. Many of the needs for materials used for such turbines are the same as the needs in both fission and fusion reactors. Simply put, if you find a material that works for one, it will almost certainly be useful for the others, too.
Veritas Vacuo, your stupidity and trolling is becoming highly annoying.
Production will be done in space, and on the moon. That's why we need a moon base, it's much easier to operate from the moon.
Production will be done in space, and on the moon. That's why we need a moon base, it's much easier to operate from the moon.Good point.
(although factories to make all the stuff needed will somehow have to be sent to the moon first)