And so what about the downsides? The ultimate target for terrorists. If that comes down and it wraps itself around the Earth, it'll be devastating.
I'm sure you could build it in a way that it would break apart into lots of smaller pieces, but even then it seems like it could be dangerous.
Plus accidents are more likely than you think. A rocket just exploded this morning, and read up on rates of railroad or shipping screwups. A train full of apples and pallets of kleenex going over ain't a big deal but the same containers falling out of the sky will certainly cause more damage.
Also it would not be an "Ultimate target" for "terrorists". Terrorists are violent political activists, not super villains that want to destroy the world. I doubt, for example, that the new-IRA would get a united Ireland by destroying orbital infrastructure.
The most effective way for the new-IRA to unite Ireland would be to help the UK keep shooting itself in the foot, so that the Northern Ireland citizens get sick of regular Ireland being better off economically, and vote to join it.
You're forgetting religious extremists and countless suicide bombers.
You break a space elevator at the ground, it floats upwards.
You break it at 30,000 foot then everything above the break floats away upwards, everything below "crashes" down, at a relatively low terminal velocity and thus with pretty low amounts of energy.
An elevator isn't a tower, it's a rope handing from a counterweight in orbit which is kept taut by a centrifugal force. It's anchored at the ground to stop the rock floating away, but if you break that anchor everything above will swing away from Earth
If you have the ability to break the cable at say 100km above the ground, you have the ability to drop objects from that height anyway, don't have to deal with no-fly-zones, and can target somewhere not on the equator.
Want to cause chaos? Get a bunch of heavy dense cheap bits of metal, put them in a high altitude balloon, then drop them over a city. You'll cause more damage to the people on the ground than anything you could do to a space elevator (short of the financial impact of having to resplice it)
If you can damage the elevator at the counterweight end, then you have the ability to drop a "rod from god" and cause more damage that way.
I would like to see an analysis. 100’s of tons of string falling and accelerating the surrounding sheath of air (acts absolutely nothing like a meteorite). A good physics question!
Space elevators are inherently create a new safety risk as cutting them at geosynchronous orbit only takes compromising some security and building a modest bomb. Both of which are achievable by terrorist organizations.
PS: 911 didn’t happen because terrorists suddenly figured out how to build giant aircraft to douse buildings in tons of jet fuel they subverted an existing system that solved 99.9% of the technical problems. Thus by getting a few violent individuals on board with simple weapons simplified things to only needed to fly an aircraft that someone else built, got into the air, and filled with fuel.
It's negligible when it's that diffuse. Even if it didn't burn up, it's mostly lost to air resistance, with everything over a few hundred meters being limited to about terminal velocity.
And that size ring, is pretty useful.
Also, ring != elevator.
Probably still want to engineer it such that destruction is controlled rather than uncontrollable, but the biggest issue with it being destroyed would be no longer having it; the damage would be mostly within a meter or so of where it lands, which isn't great but it's also not devastating unless you happen to be that close.
Think a very long I-beam falling off a skyscraper during construction, not an asteroid.