Magnetically levitated space elevator to low-earth orbit (2001) [pdf] • Hacker News Board

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#51

Post by samstave » Sat, Aug 03, 2024, 1:42 AM UTC

al_borland wrote: post #16

I seem to remember reading about this in Popular Science around that time. Of all the things I saw in that magazine, the space elevator made of carbon nanotubes was always the one that stuck with me. Though I seem to remember PopSci taking about harnessing an asteroid, or something, and putting it geosynchronous orbit, as a means to create the top anchor point. 25 years later, it seems just as far fetched.

What would the mass of said asteroid have to be to accommodate such a design?

Maybe you could have a HALO of THORNS (Telemetry homogeneous orbital restrainer nano-lattice stabilizer) - that have 13 satellite thrusters that can maintain the alignment of the nano-pillars... and have them sectionaly distributed as rings on the Z -- with tethered lattice of tubes tying it all together like a Chinese finger trap.

https://www.youtube.com/watch?v=RnofCyaWhI0 https://i.imgur.com/O9eWZnH.jpeg

and the carbon lattice is also a fuel-capillary system - that feed like a live thing...

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#52

Post by tadfisher » Sat, Aug 03, 2024, 2:03 AM UTC

anytime5704 wrote: post #47

al_borland wrote: post #16

I seem to remember reading about this in Popular Science around that time. Of all the things I saw in that magazine, the space elevator made of carbon nanotubes was always the one that stuck with me. Though I seem to remember PopSci taking about harnessing an asteroid, or something, and putting it geosynchronous orbit, as a means to create the top anchor point. 25 years later, it seems just as far fetched.

This seems like a great way to accidentally cause another global extinction event. I’m probably overestimating the size of the anchor.

The anchor would need to be beyond geostationary orbit to keep the center of mass geostationary, so a broken tether would result in the anchor departing "outward". The reason to use an anchor is to avoid creating a tether that's twice as long as it needs to be.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#53

Post by tadfisher » Sat, Aug 03, 2024, 2:13 AM UTC

la64710 wrote: post #33

What about the birds and the planes flying into the elevator cables? Is any othe thinking about it? Where do these crazy ideas come from? And what happens when they break and the cables fall to the earth? time we start thinking long term impact on the planet and its life for our ideas.

A Starship produces 76,000 metric tons of CO2-equivalent per launch, which is going to be far more dangerous to the birds in the long term.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#54

Post by askvictor » Sat, Aug 03, 2024, 2:56 AM UTC

tadfisher wrote: post #52

anytime5704 wrote: post #47

Earlier quoted context omitted.

This seems like a great way to accidentally cause another global extinction event. I’m probably overestimating the size of the anchor.

The anchor would need to be beyond geostationary orbit to keep the center of mass geostationary, so a broken tether would result in the anchor departing "outward". The reason to use an anchor is to avoid creating a tether that's twice as long as it needs to be.

Depends where the tether breaks. If it's somewhere along the middle, then the Earth-side section would fall to Earth. KSR's Mars trilogy examines the impacts (pun intended) of this.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#55

Post by efitz » Sat, Aug 03, 2024, 3:01 AM UTC

dekhn wrote: post #43

There's a simple point about space elevators that most people ignore. We would only build a space elevator if it made economic sense. Given the reality of construction costs, even if we had the materials, it would like cost many trillions of dollars (at least) so whatever we used it for would have to produce much more value than that. Even more importantly, if we had access to the materials necessary to build space e…

I am willing to bet that Elon Musk and SpaceX are doing the calculations very carefully and will build a space elevator if technology advances make it more cost effective than reusable rockets to get to Mars.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#56

Post by richk449 » Sat, Aug 03, 2024, 3:24 AM UTC

dekhn wrote: post #43

There's a simple point about space elevators that most people ignore. We would only build a space elevator if it made economic sense. Given the reality of construction costs, even if we had the materials, it would like cost many trillions of dollars (at least) so whatever we used it for would have to produce much more value than that. Even more importantly, if we had access to the materials necessary to build space e…

Many technologies are developed long before they are viable because they have military value. Access to space is currently a major national security issue, so a space elevator could be a manhattan project.

Some technologies are developed by the free market before they are economically viable too. LEO constellations for instance (both the original - iridium, and starlink).

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#57

Post by metadat » Sat, Aug 03, 2024, 3:26 AM UTC

monkeyfun wrote: post #38

mikewarot wrote: post #35

If we're pushing "out of the box" ideas, why not just use hydrogen balloons to hold up a railgun for the first 20,000 meters of altitude? The ambient pressure at the end would be about 1/10th of that at sea level. You could have outriggers with a very thin high voltage power line to enable station keeping via thrusters (repurposed quadrotor parts?) I wouldn't be surprised it the ambient electrostatic field from the a…

Relatedly, have you ever heard of skyhook? Not the CIA one but the orbital infrastructure concept -- lets you literally just take a supersonic capable plane with no rocket engines whatsoever into space. Always love that concept with how it's actually engineer-able with current materials and sounds like it shouldn't work until you look closely.

This?

https://en.wikipedia.org/wiki/Skyhook_(structure)

Interesting idea, but if I'm understanding correctly, how do you stop the thing you hooked from swinging around and back down? Would you need to reel in 50 miles or whatever of cable?

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#58

Post by samstave » Sat, Aug 03, 2024, 3:36 AM UTC

pdonis wrote: post #50

s1artibartfast wrote: post #44

Earlier quoted context omitted.

thats what the railgun is for. Altitude is to reduce friction and energy needed.

> thats what the railgun is for A railgun that can provide a delta-v of 8 kilometers per second?

You sent me down a fun rabbit hole for rail-guns, nano-tubes, super conductors, velocity requirements, megajoules required to launch 1,000KG payload into space:

Imagine a U/C channel of carbon nano tube and corresponding super conducting magnets that act as the rail-gun in the same way an aircraft carrier does...

(The maths in this thread are pretty cool):

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#59

Post by more_corn » Sat, Aug 03, 2024, 3:39 AM UTC

tadfisher wrote: post #52

anytime5704 wrote: post #47

Earlier quoted context omitted.

This seems like a great way to accidentally cause another global extinction event. I’m probably overestimating the size of the anchor.

The anchor would need to be beyond geostationary orbit to keep the center of mass geostationary, so a broken tether would result in the anchor departing "outward". The reason to use an anchor is to avoid creating a tether that's twice as long as it needs to be.

But if you break the tether halfway down the bottom half falls at 16,000 mph right? And then it’s burning and then it cracks like a whip. I don’t know about extinction, but not a fun time for anyone.

Re: Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

#60

Post by more_corn » Sat, Aug 03, 2024, 3:40 AM UTC

worldsayshi wrote: post #26

al_borland wrote: post #16

I seem to remember reading about this in Popular Science around that time. Of all the things I saw in that magazine, the space elevator made of carbon nanotubes was always the one that stuck with me. Though I seem to remember PopSci taking about harnessing an asteroid, or something, and putting it geosynchronous orbit, as a means to create the top anchor point. 25 years later, it seems just as far fetched.

Although we have come much further with carbon nanomaterial. I wonder how close we are to achieving continuous fabric.

We’re about 20 years away. Always will be.