Space Elevators Could Be Lethal

Maggie McKee writes, "A new study reports that passengers on space elevators of current design could be killed by radiation. Even traveling at 200 kilometers per hour, passengers would spend several days in the Van Allen radiation belts, long enough to kill them." Looks like the elevator scientists will get this one solved before liftoff.

Comments

The two rubs

[LotsOfPhil]

This hasn't been an issue before because most astronauts don't get in the way of the van Allen belts. The Apollo astronauts went through super fast (escape velocity is 40,000 km/hr).

"For a space elevator travelling at the current proposed speed of 200 kilometres per hour, however, passengers might spend half a week in the belts. That would hit them with 200 times the radiation experienced by the Apollo astronauts."

The article says that you may not want to add shielding because of the added mass. Wikipedia says that "an object satellite shielded by 3 mm of aluminum will receive about 2500 rem (25 Sv) per year." I don't know how this would translate for people going through the area, but 3 mm of aluminum doesn't weigh much.

Re:Aqua viva

[maxume]

Radiation does bad things to dna. It mostly just heats water. Ooooh, scary, somewhat warmer water.

Re:Oh, the horror!

[A beautiful mind]

Well contrary to the popular opinion, scientists aren't idiots, so they thought about the Van Allen radiation belts long before any sensationalist headline came up with it.

Hybrid solution

[Fonce]

Given that gravity won't be nearly as much of an issue at that altitude, a combination of shielding including water or metal (likely both) and increased speed seems to me to be the simplest route. All things being equal, that's probably the better solution.

We've made it through the Van Allens before, we'll figure out how to do it again.

And, anything can kill you, really, so long as it's an action. Space elevators aren't lethal in and of themselves. Organ failure due to blunt trauma, rapid depressurization, radiation poisoning; these can kill you. An elevator cannot. It's an inanimate object. Well, unless you're on acid. Then you're on your own, kid.

Re:C'mon, COMMON SENSE!

[Jeremi]

Stuff had damn well better come down the cable, or the thing will deorbit itself.

I don't think you've thought it through. Of course angular momentum isn't free, but that doesn't mean that you have to send things down the cable to keep the elevator from deorbiting. Once a unit of payload mass is lifted past the center of gravity of the cable, it effectively becomes part of the counterweight, increasing the amount of mass the space elevator is capable of lifting from then on (up to the point where the increased tension would cause the cable to snap, anyway).

So where does the "non-free" angular momentum come from? From the angular momentum of the Earth, of course... every time something goes up the elevator, the Earth spins a tiny bit slower -- similar to how an ice skater spins more slowly after she extends her arms. Fortunately, the Earth is massive enough compared to us humans that we'd never conceivably make a noticeable dent in Earth's momentum reserves (famous last words? ;^))

That said, a second parallel "down" elevator near the "up" elevator might be useful at some point, for more efficient round trips. But that's for later, the first task is to get a one-way elevator working.

Re:Math error?

[Cecil]

Actually, the giant counterweight at the top of it would be actually beyond geosynchronous orbit, and the center of mass of the cable would be in geosynchronous orbit, but the cable itself would not be in any kind of orbit.

Saying the cable is in geosynchronous orbit is analogous to saying that the cables on a suspension bridge are "flying".