h a l f b a k e r y
Bunned. James Bunned.

meta:

account: browse anonymously, or get an account and write.

 user: pass:
register,

# Rubber Space Elevator

Working robotics faster than the speed of sound. Use self-constructing elevator by using the elevator shaft to accelerate payloads forming the extensions of shaft faster than the shaft can transduce the crushing pressure downwards.
 (0) [vote for, against]

The reason we can't build taller buildings, is because the materials at the bottom get crushed by their own weight. However, this crushing transduces at the speed of sound. (i.e., if we push a material, that material will start moving non-uniformly, starting from its first molecules, that will transduce to further molecules at the speed of sound).

The speed of sound in some materials like rubber, for example, can be pretty low, e.g., 40 m/s. It's quite easy to reach the speed faster than the propagation of sound in rubber. So, suppose you start with building an elevator shaft as a thick-walled elevator shaft-like rubber tube, that is short enough for a payload to reach the speed greater than the speed of sound in rubber over that distance by propelling through crawling against the walls of the existing tube with wheels made of material of a higher speed of sound in it.

Suppose that the payload itself is just next section of the rubber-tube, and we have a technique to very precisely and quickly align and attach the payload as a next extension to the tube. (e.g., a tube section to be attached at the top of the tube), thus extending the acceleration track.

The waves of sound created by pushing against the rubber walls won't reach the bottom of the rubber walls for a longer time than it takes to use those walls to accelerate payload with a follow-up extension of the tube

The payloads (each of them), would then extend the tube faster than the speed of sound in the tube in the rapid and precise succession, which would not create the crushing pressure at the bottom, and allow to "climb an accelerating falling ladder" that brings its own matter to push against.

As a result, we don't need chemical rockets anymore. Of course, the whole thing would still be in the gravity field, but the idea is that the inertia could eventually win against gravity.

 — Mindey, Mar 05 2019

Polyethylene robotic snake https://youtu.be/oRjFFgAZQnk?t=60
[Mindey, Mar 06 2019]

Space Hose Space_20Hose
[MaxwellBuchanan, Mar 06 2019]

So, the vehicle is accelerated upwards by pushing downwards on the rubber tube via its wheels. But the downwards force is only on the rubber next to the wheels, since the force does not have time to propagate further down the tube to the ground. Therefore the vehicle is accelerated upwards through the equal and opposite reaction of only the part of the rubber tube in contact with the wheels. This implies that the tube is quite massive compared with the mass of the vehicle. Yet the vehicle's weight being accelerated upwards is largely composed of a payload of enough rubber tubes to stack end to end to reach geostationary orbit height. Therefore at any stage in the ascent, the rubber tube has to have a wall thickness proportional to and comparable to the total volume of rubber in the entire structure above that height. I think that is going to make for a rather conical structure and there might not be enough rubber in the universe to make the lowest few meters of the structure even if you started from the top of a high mountain.
 — pocmloc, Mar 05 2019

What's needed, shirley, is just a hugely long polythene tube that's gradually inflated with hydrogen.
 — MaxwellBuchanan, Mar 05 2019

 [pocmloc] maybe gyros in each of the payloads could keep the tube in alignment, and this we don't need a mountain?

 // What's needed, shirley, is just a hugely long polythene tube that's gradually inflated with hydrogen. //

[Max], that's genius! Reminds me the snake robots. [see link]
 — Mindey, Mar 06 2019

//that's genius!// To give credit where it's due, I think I thought of it because of the Space Hose <link>.
 — MaxwellBuchanan, Mar 06 2019

Ah, gyros! You should have mentioned them before. If you include gyros it will work for sure.
 — pocmloc, Mar 06 2019

?, rubber bullet stunned
 — wjt, Mar 08 2019

Not an idea for a giant rubber band slingshot to launch things into space then?
 — Skewed, Mar 08 2019

Confused. So if a 343m vertically standing stick is being measured on a scale, pressing weight on the top will take 1 second to register a change on the scale? Seems wrong. Shock waves travel faster than sound.
 — wjt, Mar 10 2019

Probably faster, because the speed of sound is higher in a lot of solids than it is in air.
 — notexactly, Mar 10 2019

It would be exponential as well because the weight is increasing therefore the stress density is higher on the lowest components.
 — wjt, Mar 10 2019

 This idea is beautifully half-baked. I don't think it would work at all, but it's still beautifully half-baked.

I like the visual of all the shock waves travelling down the elevator, so that once the payload has reached the top, the combined weight of several miles of rubber tower smashes into the ground and explodes.
 — mitxela, Mar 10 2019

 [annotate]

back: main index