Happy Birthday: Alyiania, BiffyBuffy, Dirty Socks, Kalika, and Mr. EverDawn!YAY fenric!
(of the Big List!)ChristopherMarlowe
I totally agree. The Demon Nazis were terrible!wolfguard,Christopher Marlowe
The Shkadov Thruster is actually something I hadn't heard of before, so I had to look it up. The article in Wikipedia is incomplete (missing a lot), but it's actually very simple. The large spherically curved mirror is located at a point far enough from the sun so that the amount of radiation pressure on the mirror exactly equals the gravitational attraction on it from the sun. Because of this, the mirror will be stationary relative to the sun in space, and doesn't orbit the sun. The light emitted from the sun that strikes the mirror will be reflected back to the sun, creating an imbalance in the solar output in the direction of the mirror. Since light has momentum, that momentum will be transferred back to the sun, and there will be a thrust (force) in the direction of the mirror from the sun. That is, more light will leave the sun opposite the mirror than will leave the sun in the direction of the mirror. This will create a force on the sun. Since force equals mass times acceleration (F=m*a), the sun will accelerate in the direction of the mirror. Anything gravitationally bound to the sun will also feel the same acceleration, including all the solar system and also the mirror since the light pressure balances the sun's gravitational attraction on the mirror at it's location. The amount of thrust will depend on three things, the output of the sun, and the location and size of the mirror.
Interestingly, you could use a parabolic mirror that would reflect all the light over a given region of space in the same direction instead of radially back toward the sun.
"For a star such as the Sun, with luminosity 3.85x10^26 W and mass 1.99x10^30 kg, the total thrust produced by reflecting half of the solar output would be 1.28x10^18 N. After a period of one million years this would yield an imparted speed of 20 m/s, with a displacement from the original position of 0.03 light-years."1
The acceleration of the sun in this example is 6.4x10^-13 m/s2
, which is extremely small, so it's real slow process. For example, using the same acceleration to accelerate a 1.0 kg. ball so it traveled one meter across a small table would take 1,250,000 seconds or 347.22 hrs or 14.4 days. Just think of waiting 2 weeks for the ball to move across a small table. :)
PS: the physics of this is really simple. :)1 Shakdov Thruster