If you are going really, really fast, you wouldn't just want gas giant planets. You'd want the outer layers of red giant stars.
Re:Relativistic Spaceship
by PaulDavisThe1st on Monday February 05, 2024 @07:56PM
(#39269389)
the top of this thread is filled with a discussion of the almost unimaginably catastrophic consequences of a ship moving at 0.9C hitting atoms in interstellar space.
trying to decelerate by "braking" anywhere close to a gravitionally significant mass sounds like a guarantee to total destruction from the impact of "stuff" (even individual photons).
Re:Relativistic Spaceship
by JumpCrisscross on Monday February 05, 2024 @08:16PM
(#39269543)
> a ship moving at 0.9C
You decelerate from 0.9C to 50 km/s conventionally, more if you can aerobrake or line up multiple slingshots, and that last 0.00001% with gravity assist.
It saves you more than that in fuel, because the fuel you'd have used on that last bit of deceleration needed to be accelerated and decelerated the entire way from 0 to 0.9C back to close to zero.
It's still a lot of energy you can bleed off, particularly if you're aiming for a system with gas giants. I'm not suggesting one only rely on passive deceleration. But especially given it's fuel saved at the very end of the journey, fuel you no longer need to accelerate and decelerate for the entire duration of the trip, the savings could be sizeable.