Dodging debris in the Clarke Belt.
In last week’sGreen Arrow #30, DC Comics gave readers what they’d been waiting for: the first Rebirth glimpse into the complicated friendship between the titular hero and his similarly hued counterpart, the Green Lantern.
Writer Benjamin Percy did a fine job of contrasting the grounded Oliver Queen with the space-faring Hal Jordan, as the high-flying space cop brought the emerald archer into a geostationary orbit to find the satellite of an evil banking conglomerate.
Or did they only make it to low Earth orbit? Percy has the pair take a scientific interlude once they slip the surly bonds, as Lantern educates Arrow on the Clarke Belt. It’s a neat effort, but not all the numbers add up.
Closer to Home
Well, there are about 1,400 satellites currently in operation, plus another 2,600 or so that don’t work anymore (almost twice that number have been launched since Sputnik, the first artificial satellite, but the rest have fallen back to Earth by now). So Hal is technically right here.
Barber seems to have gotten the “500,000 pieces of debris” figure from a 2013 NASA article, but it’s unclear where the space agency itself came up with that. The U.S. Strategic Command (a division of the Department of Defense) estimates there are less than 18,000 artificial objects orbiting the Earth, but that number only counts things actually big enough to be tracked. The European Space Agency says there’s probably another 700,000 good-sized chunks up there, plus 170 million bits a half inch in length or less.
But while that stuff does move fast enough to do serious damage, not all of it is traveling at 17,500 mph. Orbital velocity is a straightforward calculation — the farther away something is from the Earth, the slower it goes. The quoted speed puts things in what’s called “low Earth orbit,” somewhere around 1,200 miles above the surface. Objects in low Earth orbit are close enough to still be subjected to drag forces from the atmosphere.
Not So Fast
AS OPPOSED TO objects in a geostationary orbit, where the duo ends up. That’s more than 22,000 miles (or 36,000 km — Hal’s right!) above the Earth’s surface, where objects have an orbital velocity that just matches the speed of Earth’s rotation, so a satellite can always remain in the same location, relative to the ground. It only traces the orbit directly over the equator, though (whoops, Hal), so a geostationary object can never be “directly above Seattle.”
Objects in the Clarke Orbit — yes, it is sometimes called this after the science fiction author who first popularized (but didn’t create) the idea of putting communications satellites there — “only” travel at 7,200 mph.
At Least it Sounds Cool
Still, that’s not so bad for comic book dialogue. It gets a little weirder, though.
Let’s ignore that, technically and theoretically, there is no distance limit to the Earth’s gravitational influence, and that the Moon is more than 10 times farther from the Earth than the Clarke Belt is (not just “over there,” as Green Arrow #30 seems to portray) — what the hell good is it to put a satellite on the far side of the Moon, where much of the radio and microwave signals coming from it will be blocked from reaching the Earth?
I guess even in a somewhat smartly-written comic, supervillains will always be dumb.