For this month, I've prepared a Kerbal Space Program- based demonstration on how to stay in space. Even though the game has good physics in place, I'm going to step it up a little. I'll be using a mod called Realism Overhaul. This mod replaces the Kerbal solar system with our Solar System. This makes things a great deal more challenging, and more realistic. With the intro out of the way, let's get started! As you can tell by the title, this post is about staying in space. Let's first define "space." Where does the atmosphere end and space begin? In real life, the atmosphere doesn't really end. It just gets thinner and thinner, until it is undetectable. That line can't be defined absolutely, though. For the sake of the lesson, however, the atmosphere gets thinner as you go higher until you get to 140 kilometers, where it ends. So once you get above 140 kilometers, you are in space and begin to float... right? Rather than answering this question with math, let's just launch a rocket and find out for ourselves! Those were some screenshots of the launch itself, from Cape Canaveral, Florida. The launch put us in space, and the accelerometer reads 0g (we're floating!) Our Kerbals are enjoying their view of Earth from 650 kilometers above the ground, and they can see the Great Lakes! There is something funny going on, though. The space ship is still continuing upward at the ridiculous speed of one mile per second (3600 mph!), even though we turned our engine off. It is starting to look like our Kerbals will drift away from Earth forever, floating aimlessly in the void of space until life support fails. The ship's altitude keeps climbing until 980 kilometers above the ground, where the Kerbals get some crazy views of the entire United States, along with the northern portions of South America. After 980 kilometers, however, the altitude begins to decrease, indicating that the space ship is now falling back to Earth! The Kerbals are still feeling weightless. Their speed begins to increase as the relentless -9.8 m/s^2 of gravity from the Earth pulls them down. The space ship enters the atmosphere at a bit more than 2 miles per second. As the atmosphere thickens, the Kerbals begin feeling the tiniest amount of gravity again, and it grows stronger as the air gets a more firm grip on the space ship. The ship tumbles and spins at a rapid rate as it gets heated up by the atmosphere, and parts start melting and breaking off into a cloud of burning debris outside the Kerbals' window. The G-force continues to build to incredible amounts. Eventually, the G-force becomes so great that the Kerbals inside die as their hearts fail to pump blood upward into their brains. The ship ends up exploding entirely at about 10 kilometers above the surface. According to the flight logs, the G-force climbed to a peak of 54.2G. The flight only lasted 21 minutes and 24 seconds, in which the ship traveled about 2,000 miles through space. So what went wrong here? Our Kerbals made it to space, and they stayed there for a long while.
As it turns out, there is no "cut-off line" for gravity. Earth's gravity continues outward and gradually fades away the further you get from it. If gravity worked how lots of people seem to think it does, then the Moon has no reason to orbit Earth. Our space ship was not anywhere near being far enough away for Earth to not affect it. So now we know that being in space isn't the same as being in orbit. We know the Moon is in orbit of the Earth, that's why it doesn't crash down like our rocket did. So what is an orbit? How does one stay in space like the ISS does? Find out in next month's post, "Using Orbits to Stay in Space!"
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Jacob mitchellI like to play computer games, program, and try my hand at 3D printing. Archives
February 2017
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