Review: Space Cowboys
The Astronomy of Space Cowboys
To be honest, there wasn't a lot of actual astronomy in the movie, but there was a lot of space action. Surprisingly, the physics of space travel was fairly realistic in the movie. They made a lot of the usual mistakes, which I'll mention briefly below. I also have some general comments about the movie, both Good and Bad, which I have added to the end of this page. So on to it!
Bad: The engineer says that IKON, the Russian satellite, is at a height of 1000 miles and losing altitude at 8000 meters per day.
Good: Ignoring the mixed units, these numbers don't really work. A satellite at an altitude of 1000 miles would stay stable in its orbit for centuries. The main reason a satellite's orbit would decay is due to friction with the Earth's atmosphere. Most people think that an object in orbit is above the atmosphere, but in reality there is air up that high, it's just incredibly thin. Over years, drag against the air slows the satellite down, which in turn lowers the orbit. An object at an orbital height of just 500 kilometers or so would be able to stay in orbit for a long time. Look at Hubble; it orbits at roughly 600 kilometers, and has been in orbit since 1990. Granted, it has needed a reboost because its orbit has dropped somewhat, but it was never really in danger of dropping onto the Earth. At an orbit twice that high, the drag is extremely low. For a satellite to drop eight kilometers (5 miles) per day at that height is pretty silly.
Also, the Shuttle cannot get that high. The highest the Shuttle can get is about 900 kilometers (560 miles), but that's a highly elliptical orbit and a tough one to manage. Its usual height off the Earth's surface is about 300 kilometers or a bit more.
(For the next two Bad segments, I am quoting conversations in the movie from memory. The quotations may not be exact, but they capture the intent of the dialogue.)
Bad: During a tour, a kid asks, "What would happen if you jump on a trampoline in space?" The engineer replies, "You'd go up... and up... and up."
Good: Actually, you cannot jump on a trampoline in space! Well, you can, but you need to set things up correctly. On Earth, you stand on a trampoline and jump up gently to get you started. Gravity pulls you back down, and you kick with your legs to get higher on the next bounce. That won't work in space. If you stand on the trampoline and push off it to get yourself started, you'll just keep going away from it. It might as well have been a wall or a floor; without gravity you just keep going in the direction in which you pushed yourself. Parade Magazine columnist Marilyn vos Savant made the same mistake once.
Bad: Another kid asks, "Can you hit a baseball to the Moon in space?" and she says, "Yes; you just need to knock it halfway there, about 100,000 miles, and the Moon's gravity will take it from there."
Good: That's not correct; the Moon's gravity doesn't take over halfway there. The Moon is a lot less massive than the Earth, and so its gravity is correspondingly less. In other words, the weaker gravity of the Moon means you have to be much closer to the Moon than the Earth for the gravity to balance. The Moon has about 1/80 the mass of the Earth. If you go through the math, you'll find that halfway between the Earth and Moon (which she correctly gives as about 100,000 miles away) the Earth's gravity is still 80 times that of the Moon's.
If you calculate where the gravity just balances, you'll find that it goes as the square root of the mass ratio. In other words, you have to be the square root of 80 times closer to the Moon than the Earth, which is equal roughly to 9. That means you need to be about 216,000 miles from the Earth, or about 24,000 miles from the center of the Moon. That's a long way to hit a ball!
Bad: When the astronauts finally get to IKON, everyone is amazed at how big it is.
Good: Now come on! Russia begs the U.S. to fix their satellite, NASA spends about a billion dollars getting a mission up there, man-years are spent training astronauts, and they don't even know what the satellite looks like? That's just silly. Eastwood wanted everyone to be impressed with the IKON, and also wanted an air of secrecy and coverups. It fell pretty flat with me; it was a plot device and detracted from the realism of the movie. Now of course this movie isn't all that realistic, but Eastwood went to a vast amount of effort to make sure the astronaut tech was correct. It would have been nice to see some of the more obvious plot holes plugged.
Good: He goes outside without being tethered! That never happens in space; if he lets go, he'll drift away, and the pilot would have to waste fuel and time retrieving him.
Bad: The Russian says that the missiles in IKON are locked onto American cities. The implication is that those cities will be destroyed if Eastwood screws up.
Good: Actually, since the orbit has decayed from geosynchronous (an altitude of roughly 22,000 miles) to low Earth orbit at 1000 miles, I don't think the missile guidance systems would get a chance to work. If the missiles were launched, they would simply shoot down toward the Earth and blow up wherever they happened to be.
Bad: At one point, the rotating solar power panels on IKON slam into the Shuttle, wrapping around the nose.
Good: That's Bad, for the astronauts! The tiles all over the Shuttle are used to absorb the tremendous heat of reentry. They are also very brittle. An impact like that would have torn them off by the hundreds, making reentry impossible.
Bad: To save the day, Hawk decides to stay with the IKON as he blows it out of harm's way using the onboard rockets.
Bad: Speaking of which, Hawk rides the IKON to the Moon. At the end of the movie, we pan over the Moon's surface and see Hawk's spacesuit on the surface.
Good First, getting IKON to actually impact the Moon would be incredibly difficult, if not impossible. You don't just aim a rocket and touch it off! You have to match orbits with the Moon, and Hawk would have no idea of the exact speed and direction of his boost. Most likely he'd miss the Moon by thousands of kilometers.
But let's say he does hit it. The impact speed would be at least one kilometer per second, which is how fast the gravity of the Moon alone would have accelerated IKON. Add to that the velocity from the rockets needed to break from low orbit and you have an impact speed of something like 10 kilometers per second or more. The energy of the impact would vaporize the IKON and Hawk along with it, yet we see him sitting on the Moon, intact. There's not even a crack in his visor!
Incidentally, in 1999, scientists let the orbiting probe Lunar Prospector impact the Moon's surface in hopes that they could detect water on the Moon. If the water existed at the impact site, the heat of impact would vaporize it and throw it off the surface, where it could be seen by ground based telescopes. To my knowledge, no indications of water were ever found. The point here is that the impact speed was far smaller than what IKON's would have been, but it was enough to destroy the LP probe. After impact, Hawk would have been a greasy smear on the lunar surface.
One more point: Eastwood's wife asks him if Hawk made it to the Moon, and he replies that he doesn't know. Actually, an impact of that magnitude would be visible from the ground, and engineers could estimate pretty well the time of impact. Every telescope on the planet, professional and amateur, would be pointed at the Moon (if it were visible) at the moment of impact.
Bad: After Hawk takes his Final Flight, a controller at Houston says "IKON has left the Earth's gravitational field."
Good: Nothing can ever leave Earth's gravity! Gravity goes on forever. In reality, if you move quickly enough you can get away from a source of gravity faster than it can slow you down. This is called the escape velocity. This is not just a matter of semantics, but a real physical effect. The Earth's gravity doesn't just stop at some distance from the Earth, but actually extends outward forever (neglecting some weird relativistic effects due to the Earth's finite age). Think of it this way: the Earth's gravity is what keeps the Moon in orbit around us, so how could IKON be outside our gravity when it was never farther away than the Moon?
That ends my specific points about the movie. I have a few general comments about it, both Good and Bad.
Again, I liked the movie. There aren't any surprises in it, but it was fun, funny, and depicted NASA and space exploration in a mostly positive light. If you get a chance to see it in the theaters, take it, but it will rent well too.