When launching a deep-space craft, how do the rotation and orbit speeds of the Earth and direction (relative to the prior) impact the travel time and actual velocity of the space craft?

Question

To simplify it for my mind, I envision the Earth being a car, and the space craft being something like a bullet. If the car (Earth) is orbiting at 30,000 m/s, and the bullet (spacecraft) is traveling at 17,000 m/s (Voyager 1 speed), the bullet is then traveling at 47km/s, but only at 17km/s relative to the car. But, if the car’s direction changes and goes the opposite way at the same speed (as with orbit), it is actually then going 77km/s. This is confusing me 😩.

In: Physics

Answer 1

Pretty much all spacecraft intended to go into a roughly equatorial orbit launch from West to east to take advantage of the 1500 kmh boost from the Earth’s rotation. The only exception I can think of is Israel, which launches the other way so they can dump their rocket stages in the Mediterranean instead of on the countries east of them.

The interplanetary component is somewhat hard to explain so I recommend trying out games like Kerbal Space Program for PC and console or Spaceflight simulator for your phone. The physics in the two are mostly realistic and trying is the best way of learning.

In short, all the planets’s speed relative to the sun has to be taken into account when performing deep space transfers because it is so significant. Since every planet orbits the same direction, this is made simpler and easier because that reduces the relative speeds between them.