Build a 1 Million Tonne Cargo Net: Tech & Materials Needed

  • Thread starter Thread starter chasrob
  • Start date Start date
  • Tags Tags
    Net
Click For Summary

Discussion Overview

The discussion revolves around the feasibility of constructing a cargo net capable of supporting 1 million tonnes of iron chunks using current technology and materials. The context includes theoretical considerations, material properties, and the implications of lifting such a massive weight, particularly in a sci-fi scenario involving a superhero capable of extraordinary feats.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that lifting 1 million tonnes at 1g is equivalent to the weight of the Golden Gate Bridge, indicating that current crane technology, which can lift about 20,000 tonnes, is insufficient for such a task.
  • Another participant calculates the required number of ropes made from materials like Spectra and Vectran, estimating that approximately 400,000 ropes would be needed to handle the force generated by lifting 1 million tonnes at 2g, factoring in a safety margin.
  • There is a proposal to arrange the ropes in an interconnected matrix to potentially increase lifting capacity, with questions raised about the suitability of different materials such as Kevlar or carbon fiber.
  • A participant mentions the possibility of using a large concrete column to distribute the force, discussing the compressive strength of various materials and the challenges of applying pressure without causing damage.
  • One participant humorously suggests that the superhero could throw the iron blocks one at a time instead of using a net, while another emphasizes the urgency of transferring large quantities of material from low Earth orbit to Earth quickly.
  • There is a discussion about the implications of adjusting the orbit of the iron blocks instead of lifting them, with concerns raised about the potential loss of material during atmospheric entry.
  • Another participant highlights the value of iron in orbit and suggests that it would be more beneficial to process the material in space rather than transporting it to Earth.

Areas of Agreement / Disagreement

Participants express various viewpoints on the feasibility of the proposed cargo net and the methods of lifting or transferring the iron blocks. There is no consensus on the best approach, and multiple competing ideas remain throughout the discussion.

Contextual Notes

Participants rely on assumptions about material properties and the capabilities of the superhero, which are not universally agreed upon. The discussion also involves speculative scenarios about lifting techniques and the implications of orbital mechanics.

Who May Find This Useful

Readers interested in theoretical engineering challenges, material science, and speculative fiction may find the discussion relevant and engaging.

chasrob
Gold Member
Messages
185
Reaction score
58
I'm writing a sci-fi story. Is it possible, using today's tech and materials, to make a net that will support 1 million tonnes of one tonne iron chunks? It must be one-point lift and withstand a couple gees acceleration/de-acceleration.
Thanks for your help.
 
Physics news on Phys.org
One million tons is about the weight of the Golden Gate Bridge at 1g. Twice that at 2g.

The largest crane can lift about 20000 tons.

A single point lift needs a shackle and a cable strong enough for the load, so it is more than the net.

I think the answer is no.
 
anorlunda said:
One million tons is about the weight of the Golden Gate Bridge at 1g. Twice that at 2g.

The largest crane can lift about 20000 tons.

A single point lift needs a shackle and a cable strong enough for the load, so it is more than the net.

I think the answer is no.
The lift is made by superhero, who can easily bench gigatonnes :). So I suppose the net must be designed to be thin enough to be gathered together and slung over his shoulder, heh.
XPft7kZ.png

The iron chunks could be assumed to form a rough sphere 60-70 meters in diameter, if my calculator hasn't let me down.
 

Attachments

  • XPft7kZ.png
    XPft7kZ.png
    4.7 KB · Views: 555
Last edited:
This calls for a calculation. McMaster-Carr lists ropes made of Spectra and Vectran. Both of these materials list a breaking strength of 20,000 lbs in a 1/2" diameter rope. Your superhero wants to pull 1,000,000 tons X 2 G's = 4,000,000,000 lbs force. Assume a safety factor of 2, then 4,000,000,000 / 10,000 = 400,000 ropes. Each rope has cross sectional area of 0.196 square inches, so the total cross sectional area is 78,500 square inches. If the superhero squeezes the bundle of ropes until each rope is in fully contact with the adjoining ropes, then the rope bundle will be 316 inches (26.4 feet, 8.0 meters) diameter. The superhero will need big hands, will need to squeeze hard enough to pull 4,000,000,000 lbs without slipping, and will need to pull in such a way that the force is distributed equally between each and every rope.
 
  • Like
Likes   Reactions: chasrob
26 feet? Whoa, the superguy is human sized and not Mr. Elastic :). Know nothing about Spectra or Vectran, but I wonder if the ropes were arranged in a interconnected matrix, like nets, would it would increase lifting capacity over simply roping them together? (if I understand you correctly) When I was in the USN they had steel ropes. How about Kevlar or carbon fiber (if that's available these days)?
 
Last edited:
I searched MacWhyte wire rope, and found a 1" diameter rope with rated breaking strength 151,000 lbs. You can do the math from there. Spoiler: The superhero still needs big hands.
 
  • Like
Likes   Reactions: chasrob
He could stand spread eagle and press his cape against a block/wedge. So long as he is not sinking into the surface he should be able to spread the force out. That might give him 2 m2. A 2 meter concrete column can hold up about 40 to 80 million Newtons of force. So at 1g concrete is limited to less than 8,000 1 ton blocks. Porcelain has compressive strength closer to 500 MPa so maybe 100,000 tons.

chasrob said:
..The lift is made by superhero, who can easily bench gigatonnes :)...
Try picking up a block of margarine using a toothpick. The problem is a palm smooshing into the steel block. The hydraulic press channel has lots of demonstrations of what happens when you apply too much pressure. Here they do a ball bearing. Here is diamond.

chasrob said:
... So I suppose the net must be designed to be thin enough to be gathered together and slung over his shoulder, heh.
...image...
The iron chunks could be assumed to form a rough sphere 60-70 meters in diameter, if my calculator hasn't let me down.

If the net is long and stretchy he could accelerate the cables at several g. If the net has similar mass to the iron payload it could lift it a short distance before falling back down. That would not look very heroic.

Why not throw the iron blocks 1 at a time?
 
stefan r said:
[...]
Why not throw the iron blocks 1 at a time?
There are many trillions of tons of blocks gathered together in low Earth orbit (long story) and he wants to transfer the lot Earth'side as fast as possible; a net seemed obvious, heroic or not. Therefore, million ton parcels. Matter of fact, larger than that would be even better but he has to employ current tech/materials.
 
chasrob said:
There are many trillions of tons of blocks gathered together in low Earth orbit (long story) and he wants to transfer the lot Earth'side as fast as possible; a net seemed obvious, heroic or not. Therefore, million ton parcels. Matter of fact, larger than that would be even better but he has to employ current tech/materials.

If they are in low Earth orbit the net does not need to accelerate at 1g. He just needs to adjust the orbit so that it intersects the atmosphere.

If you have a trillion tons of iron in orbit you should build an orbital ring system. Here is a paper by Paul Birch published in the 1980s (part 1, part2, part3) and a youtube video by Isaac Arthur.
 
  • Like
Likes   Reactions: chasrob
  • #10
stefan r said:
If they are in low Earth orbit the net does not need to accelerate at 1g. He just needs to adjust the orbit so that it intersects the atmosphere.
Wouldn't that burn up valuable tons of iron? He planned on dropping the net and its load manually :) to a soft landing Earth'side, taking less than 5 minutes, and continuing until all the iron is landed. That's when the inertia safety factor comes in (the gees). He would like a billion ton capacity net even more, heh.
Orbital ring system... looks interesting.
 
Last edited:
  • #11
chasrob said:
Wouldn't that burn up valuable tons of iron?...

Is far more valuable in orbit. It costs $millions to launch a ton into orbit. If you have feedstock you just need a small processing plant. A few rollers would be enough to make a lot of structures. Electron beam welders and plasma cutters are much lighter than the rollers.
 

Similar threads

Replies
3
Views
2K
  • · Replies 10 ·
Replies
10
Views
5K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 96 ·
4
Replies
96
Views
12K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 30 ·
2
Replies
30
Views
5K
Replies
7
Views
2K
Replies
12
Views
6K
Replies
8
Views
5K
Replies
13
Views
6K