Asteroid Mining and Space Elevators (split from Are billionaires rich enough yet?)

[Canard DuJour]

Whether or not humanity can build a space elevetor, "the market" cannot build enough space elevators so that there will be anything but an oligopoly or an outright monopoly.

Ditto rockets.

It makes sense for the state to some things.

 

[Loren Pechtel]

A lunar elevator would be more feasible if you wanted to go that route. Think about it: the moon always has the same face toward Earth. If we could establish a line between the surface of the moon and a station set up in a low orbit in the atmosphere of Earth (maybe using solar powered propulsion to hold it in its proper orbit), then it would be reasonable enough to design a cargo plane that could travel between the station and the planet's surface.

Can't be done--look at the actual orbit of the moon.

A cable like you envision could actually be done off Phobos for getting to Mars. (It can't throw to Martian escape, but it can throw to another cable on Deimos--and that one can throw to Earth.)

You could do it (assuming miracle fiber) above the equator at >geostationary distances but you’d have to continue to add energy to the high end or the orbit would decay under weight. So ultimately you wouldn’t get rid of, or significantly reduce the absolute energy needed to lift to LEO, except the air resistance.
And you could use a tethered lighter than air launch platform to counter most of that …

Assuming a miracle fiber you tether it to the Earth and put enough mass above geosync that it's always under tension. Now it only costs electricity, nothing needs to be done to keep it in orbit.

 

[Elixir]

A lunar elevator would be more feasible if you wanted to go that route. Think about it: the moon always has the same face toward Earth. If we could establish a line between the surface of the moon and a station set up in a low orbit in the atmosphere of Earth (maybe using solar powered propulsion to hold it in its proper orbit), then it would be reasonable enough to design a cargo plane that could travel between the station and the planet's surface.

Can't be done--look at the actual orbit of the moon.

A cable like you envision could actually be done off Phobos for getting to Mars. (It can't throw to Martian escape, but it can throw to another cable on Deimos--and that one can throw to Earth.)

You could do it (assuming miracle fiber) above the equator at >geostationary distances but you’d have to continue to add energy to the high end or the orbit would decay under weight. So ultimately you wouldn’t get rid of, or significantly reduce the absolute energy needed to lift to LEO, except the air resistance.
And you could use a tethered lighter than air launch platform to counter most of that …

Assuming a miracle fiber you tether it to the Earth and put enough mass above geosync that it's always under tension. Now it only costs electricity, nothing needs to be done to keep it in orbit.

I was thinking about that … keyword miracle. If it’s strong enough and long enough, like halfway to the moon, a ten pound weight at the end would be sufficient to haul tons … but adding weight would still degrade the orbit (unless I’m missing something).

 

[bilby]

A lunar elevator would be more feasible if you wanted to go that route. Think about it: the moon always has the same face toward Earth. If we could establish a line between the surface of the moon and a station set up in a low orbit in the atmosphere of Earth (maybe using solar powered propulsion to hold it in its proper orbit), then it would be reasonable enough to design a cargo plane that could travel between the station and the planet's surface.

Can't be done--look at the actual orbit of the moon.

A cable like you envision could actually be done off Phobos for getting to Mars. (It can't throw to Martian escape, but it can throw to another cable on Deimos--and that one can throw to Earth.)

You could do it (assuming miracle fiber) above the equator at >geostationary distances but you’d have to continue to add energy to the high end or the orbit would decay under weight. So ultimately you wouldn’t get rid of, or significantly reduce the absolute energy needed to lift to LEO, except the air resistance.
And you could use a tethered lighter than air launch platform to counter most of that …

Assuming a miracle fiber you tether it to the Earth and put enough mass above geosync that it's always under tension. Now it only costs electricity, nothing needs to be done to keep it in orbit.

I was thinking about that … keyword miracle. If it’s strong enough and long enough, like halfway to the moon, a ten pound weight at the end would be sufficient to haul tons … but adding weight would still degrade the orbit (unless I’m missing something).

As long as the centre of mass of the entire system, including counterweight, is beyond geostationary orbit, the whole thing is always in tension. Breaking the cable would cause the part above the break to fly off into space, not fall back to Earth.

 

[steve_bank]

I do not see it becoming economically feasible considering the total cost of ground support, launch and travel, vehicle, mining, and returning useful quantities of minerals.

Dollars/kilogram of a mineral on the ground ready for preocessing.

In Heinlein's Moon Is A Harsh Mistress lunar colonists send materials to Earth using magnetic rail launch as I rember. The containers splash down in the ocean.

Eco wise we need to learn to live within limits. The next area for mining is the deep ocean floor. There is no legal claim, Russia dropped Russian flags on the sea floor where there are resources.

As to a teher, I would think rotation would be needed to keep the cable taught.

 

[Bomb#20]

I do not see it becoming economically feasible considering the total cost of ground support, launch and travel, vehicle, mining, and returning useful quantities of minerals.

^^^^ This ^^^^

Going out to space to mine is something you do if you're running out of minerals on your home planet. We aren't. In constant dollars, earth-mined minerals just keep getting cheaper and cheaper.

 

[Loren Pechtel]

I was thinking about that … keyword miracle. If it’s strong enough and long enough, like halfway to the moon, a ten pound weight at the end would be sufficient to haul tons … but adding weight would still degrade the orbit (unless I’m missing something).

You're missing something--all mass beyond geosync is moving faster than orbital velocity, it pulls outward. So long as you don't hang too much stuff on it it's going to go round and round, tossing packages on transfer orbits to the closer planets. (This is paid for with Earth's rotation.) IIRC without weights it's something like 170K km long assuming a cable tapered so as to experience equal strain across it's entire length.

There are two big problems:

1) We don't have strong enough stuff. Note that there are three places we can build a cable with current tech: Luna, Phobos, and Deimos. Luna is limited to a single cable pointing Earthward.

2) Debris impacts.

 

[steve_bank]

I woud think those pesky satelites and the ISS could get in the way of an Earth tether beyond LEO.

In the 90s I went to a local Mars Society presentaion on the space elevator project. It never happened. In following years it was said all NASA was really interested in was the carbon fiber technology. Nano tubes.

In any case the teher material mayerial and a demonstration cable has yet to be made AFAIK.

 

[Elixir]

I was thinking about that … keyword miracle. If it’s strong enough and long enough, like halfway to the moon, a ten pound weight at the end would be sufficient to haul tons … but adding weight would still degrade the orbit (unless I’m missing something).

You're missing something--all mass beyond geosync is moving faster than orbital velocity, it pulls outward. So long as you don't hang too much stuff on it it's going to go round and round, tossing packages on transfer orbits to the closer planets. (This is paid for with Earth's rotation.) IIRC without weights it's something like 170K km long assuming a cable tapered so as to experience equal strain across it's entire length.

There are two big problems:

1) We don't have strong enough stuff. Note that there are three places we can build a cable with current tech: Luna, Phobos, and Deimos. Luna is limited to a single cable pointing Earthward.

2) Debris impacts.

Im not missing that. If you add “enough weight” it will come crashing down instantly as soon as the c.o.g. of the whole system lies inside geosynchronous height. Before that though, you have to accelerate the counterweight to several times Leo orbital velocity, if it’s goin to remain geosynchronous at say 40,000 miles away.
When you add weight, the drag will slightly (or greatly if it’s enough weight) alter its orbit. The effect will compound until the orbit decays and its orbital period is less than 24 hrs … it wraps around the earth and slices it in half like a melon.
Okay I made up that last part.

 

[skepticalbip]

I was thinking about that … keyword miracle. If it’s strong enough and long enough, like halfway to the moon, a ten pound weight at the end would be sufficient to haul tons … but adding weight would still degrade the orbit (unless I’m missing something).

You're missing something--all mass beyond geosync is moving faster than orbital velocity, it pulls outward. So long as you don't hang too much stuff on it it's going to go round and round, tossing packages on transfer orbits to the closer planets. (This is paid for with Earth's rotation.) IIRC without weights it's something like 170K km long assuming a cable tapered so as to experience equal strain across it's entire length.

There are two big problems:

1) We don't have strong enough stuff. Note that there are three places we can build a cable with current tech: Luna, Phobos, and Deimos. Luna is limited to a single cable pointing Earthward.

2) Debris impacts.

And then, lifting a payload from the surface of any body with no atmosphere is much more practically done with a linear accelerator on the surface.

 

[bilby]

When you add weight, the drag will slightly (or greatly if it’s enough weight) alter its orbit.

I assume that by 'weight', you mean 'mass'; But I am completely stumped about what you mean by 'drag'; There's no significant drag outside Low Earth Orbit, and even at LEO, drag is minimal. Drag is a characteristic of intra-atmospheric operations, and doesn't apply to the space end of a space elevator.

 

[steve_bank]

Economics is why I think the probability of being visited by ET is very low.

A space faring civilization as depicted on Star Trek series would be an enormous economic undertaking. Even in a dictatorship like Egyptian Pharaohs builng pyramids involves economics. Labor, food, and materials.

If something is econmcally viable and it results in a cheaper way to aquire something, someone will do it. The new planned commercial spcae staion from what I read will make money in the long run. Companies including NASA are willing to apy for space pon the staion. There are probaly many globally who can affotd a joy ride to a space station.

If there were an economic need fora mineral asteroid ming woud be commercially funded.

The commercialization of LEO and eventually the Moon is what will open up space exploration. The profit motive.

 

[Canard DuJour]

China's economic liberalisation resulted in more billionaires and less dire poverty.

Russia's economic liberalisation resulted in more billionaires and more dire poverty.

Globally, economic liberalisation resulted in more billionaires and slower economic growth.
Slower growth + more inequality = most folks worse off than they'd otherwise have been.

China did its own version of economic liberalisation, which was not western neoliberalism and actually quite authoritarian.

Russia accepted the western neoliberal model which has made most folks in the west worse off, pushed millions of Russians into dire poverty and resulted in an authoritarian/nationalist backlash - AKA Putin.

I won't point out the Western parallels with Trump, Brexit, Le Pen.. oops I have pointed it out.

As others point out, the billionaires are symptom, not disease.

 

[steve_bank]

China's economic liberalisation resulted in more billionaires and less dire poverty.

Russia's economic liberalisation resulted in more billionaires and more dire poverty.

Globally, economic liberalisation resulted in more billionaires and slower economic growth.
Slower growth + more inequality = most folks worse off than they'd otherwise have been.

China did its own version of economic liberalisation, which was not western neoliberalism and actually quite authoritarian.

Russia accepted the western neoliberal model which has made most folks in the west worse off, pushed millions of Russians into dire poverty and resulted in an authoritarian/nationalist backlash - AKA Putin.

I won't point out the Western parallels with Trump, Brexit, Le Pen.. oops I have pointed it out.

As others point out, the billionaires are symptom, not disease.

Off topic. However Russia adopted a mix of Stalinism and the Nazi kleptocracy. AKABoris Yeltsin followed by Vladimir Putin. Liberal democracy lasted a few years after the Soviet collapse.

China while still ruled by the CCP communist in name identifies itself as a socialist state. It makes a point of declaring it is not like the west and liberal democracy which it rejects as a matter of policy.

 

[Loren Pechtel]

I woud think those pesky satelites and the ISS could get in the way of an Earth tether beyond LEO.

In the 90s I went to a local Mars Society presentaion on the space elevator project. It never happened. In following years it was said all NASA was really interested in was the carbon fiber technology. Nano tubes.

In any case the teher material mayerial and a demonstration cable has yet to be made AFAIK.

Yeah, you can have elevators or you can have satellites, doing both is not viable. If you want space-based stuff and elevators you have to go with orbital rings. I question whether satellites are sustainable for the long term anyway, though--Kessler syndrome.

 

[Loren Pechtel]

Im not missing that. If you add “enough weight” it will come crashing down instantly as soon as the c.o.g. of the whole system lies inside geosynchronous height. Before that though, you have to accelerate the counterweight to several times Leo orbital velocity, if it’s goin to remain geosynchronous at say 40,000 miles away.
When you add weight, the drag will slightly (or greatly if it’s enough weight) alter its orbit. The effect will compound until the orbit decays and its orbital period is less than 24 hrs … it wraps around the earth and slices it in half like a melon.
Okay I made up that last part.

Keeping the center of mass outside geosync is basic elevator design, it's not going to come down.

 

[skepticalbip]

Im not missing that. If you add “enough weight” it will come crashing down instantly as soon as the c.o.g. of the whole system lies inside geosynchronous height. Before that though, you have to accelerate the counterweight to several times Leo orbital velocity, if it’s goin to remain geosynchronous at say 40,000 miles away.
When you add weight, the drag will slightly (or greatly if it’s enough weight) alter its orbit. The effect will compound until the orbit decays and its orbital period is less than 24 hrs … it wraps around the earth and slices it in half like a melon.
Okay I made up that last part.

Keeping the center of mass outside geosync is basic elevator design, it's not going to come down.

Correct. The large mass outside geosynchronous orbit would fly off on a tangent if the tether snapped. The physics is similar to the physics of the Olympics' hammer throw. It is the 'centrifugal force' of that distant mass that keeps the tether taut and it is the Earth rotating faster than the natural orbital speed of a mass that distant that transfers energy to make that mass have a greater angular velocity than orbital speed at that distance.

 

[bilby]

Im not missing that. If you add “enough weight” it will come crashing down instantly as soon as the c.o.g. of the whole system lies inside geosynchronous height. Before that though, you have to accelerate the counterweight to several times Leo orbital velocity, if it’s goin to remain geosynchronous at say 40,000 miles away.
When you add weight, the drag will slightly (or greatly if it’s enough weight) alter its orbit. The effect will compound until the orbit decays and its orbital period is less than 24 hrs … it wraps around the earth and slices it in half like a melon.
Okay I made up that last part.

Keeping the center of mass outside geosync is basic elevator design, it's not going to come down.

Correct. The large mass outside geosynchronous orbit would fly off on a tangent if the tether snapped. The physics is similar to the physics of the Olympics' hammer throw. It is the 'centrifugal force' of that distant mass that keeps the tether taut and it is the Earth rotating faster than the natural orbital speed of a mass that distant that transfers energy to make that mass have a greater angular velocity than orbital speed at that distance.

There's no need for scare quotes.

Centrifugal force is a perfectly good force, and one that is encountered in a wide range of situations (including the one under discussion). Insisting on the nonexistence of the mandatory equal-and-opposite of centripetal force is just silly.

 

[skepticalbip]

Im not missing that. If you add “enough weight” it will come crashing down instantly as soon as the c.o.g. of the whole system lies inside geosynchronous height. Before that though, you have to accelerate the counterweight to several times Leo orbital velocity, if it’s goin to remain geosynchronous at say 40,000 miles away.
When you add weight, the drag will slightly (or greatly if it’s enough weight) alter its orbit. The effect will compound until the orbit decays and its orbital period is less than 24 hrs … it wraps around the earth and slices it in half like a melon.
Okay I made up that last part.

Keeping the center of mass outside geosync is basic elevator design, it's not going to come down.

Correct. The large mass outside geosynchronous orbit would fly off on a tangent if the tether snapped. The physics is similar to the physics of the Olympics' hammer throw. It is the 'centrifugal force' of that distant mass that keeps the tether taut and it is the Earth rotating faster than the natural orbital speed of a mass that distant that transfers energy to make that mass have a greater angular velocity than orbital speed at that distance.

There's no need for scare quotes.

Centrifugal force is a perfectly good force, and one that is encountered in a wide range of situations (including the one under discussion). Insisting on the nonexistence of the mandatory equal-and-opposite of centripetal force is just silly.

The reason for the scare quotes is that, although there is an effect of a force radially out as long as the mass is tethered, the mass would not move away radially if the tether snapped as it should if that was the direction of a real force. A force is defined as a distance times a mass divided by time squared and centrifugal force is mass times angular velocity squared times distance from origin.

It can certainly be treated as if it is a force and it should be for something like calculating the strength needed for the tether but it is really a different animal.

ETA:
Maybe it should be renamed the centrifugal effect.

 

[steve_bank]

If you have a rotating sphere out in space away from gravity and attach a tether to the surfaceI expect the system will rotae about the center of gravity. On an asteroid you may end up with wild uncontrolled behavior.

Planets are 'tethered' to the Sun.