AstroGrav iconAstroGrav Help /Sample Simulations /Abstract Systems /ProjectileVersion 3.4

Projectile

Introduction

This simulation shows the Earth together with a single projectile. Two view windows have been provided - a high magnification view showing the projectile's orbit with the Earth so much magnified that its surface appears flat, and a low magnification view showing the entire Earth with the projectile's orbit too small to be visible. Because the Sun is not present in the simulation, the Earth has been made luminous so that you can see what's going on.

What you can do with it

If you set the system running, you can watch how it evolves, and see how the projectile follows its orbit until it collides with the Earth. You can then File / Revert to Saved, move the Low Magnification view window to the front, edit the Earth to have a much smaller radius (such as 1 km), and then see how the near-parabolic path of the projectile is really just the more distant end of a highly eccentric elliptical orbit. If you set this alternative system running, you can watch how it evolves, and see how long it takes the projectile to fall to the modified Earth.

Ideas for further investigation

You can also try editing the projectile's properties - particularly its absolute velocity - to see how it affects the projectile's path. You will find that if you change the z-component of the absolute velocity to 0, and the y-component of the absolute velocity to about 7.91 km/s, the projectile will travel fast enough to orbit the Earth in a circular orbit. Making the y-component of the absolute velocity larger still produces more and more eccentric orbits, until at a value of 11.19 km/s the orbit becomes hyperbolic. 11.19 km/s is the Earth's escape velocity.



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