h a l f b a k e r y
Trying to contain nuts.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
or get an account
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.
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
the speed of sound. (i.e., if we push a material, that material will start
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
low, e.g., 40 m/s. It's quite easy to reach the speed faster than the
of sound in rubber. So, suppose you start with building an elevator shaft as
thick-walled elevator shaft-like rubber tube, that is short enough for a
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
have a technique to very precisely and quickly align and attach the payload
a next extension to the tube. (e.g., a tube section to be attached at the top
the tube), thus extending the acceleration track.
The waves of sound created by pushing against the rubber walls won't
the bottom of the rubber walls for a longer time than it takes to use those
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
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.
Polyethylene robotic snake
[Mindey, Mar 06 2019]
[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.
||What's needed, shirley, is just a hugely long polythene tube
that's gradually inflated with hydrogen.
||[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]
||//that's genius!// To give credit where it's due, I think I
thought of it because of the Space Hose <link>.
||Ah, gyros! You should have mentioned them before. If you include gyros it will work for sure.
||Not an idea for a giant rubber band slingshot to launch things
into space then?
||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.
||Probably faster, because the speed of sound is higher in a
lot of solids than it is in air.
||It would be exponential as well because the weight is increasing therefore the stress density is higher on the lowest components.
||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.