I was watching YouTube video about gravitational slingshots and conservation of energy was explained as "planet loses its orbital energy around sun while spacecraft gains energy"
In solar system it explained as decreased orbital energy around sun but its supposed that spacecraft approach from front side (their initial velocities are opposite)
What if it approaches from back side, then due to conservation of momentum shouldn't final velocities of both increase? (same direction for initial velocities)
Actually when you think with reference to sun, both cases are ok, they don't violate anything, so it doesn't depend from what direction you approach planet with respect to its velocity. But what if there is no any solar/other systems and orbits and planet is stationary?
What i was thinking for is, lets consider big mass/planet in space but stationary this time, like really absolute stationary. When spacecraft gets near, due to centrifugal force it changes direction of its initial velocity lets say for matter of simplicity by 180 degrees (u shape turn). But due to conservation of momentum, planet accelerates in opposite direction little amount and thats where i got confused. Looks like total energy is increased.
I was thinking maybe it can be explained with the fact that nothing is stationary in space and there is no absolute speed as everything depends on which reference frame you are using, so there definitely should be some orbital path for that 'stationary planet' but then it violates my first assumption 'absolute stationary'.
When you starting do this thought experiment in completely stationary and empty space, things gets weird.