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Space travel question
Can anyone help?
I'm working on a story in which an alien ship is entering the solar system. The crew have been in relativistic flight from a plant at a convenient plot distance (close to us, but not next door). The ship is now decelerating (and may have been for a long time).
It can have any drive system that anyone cares to propose as long as it is reasonably plausible.
How far out is it likely to be spotted? (Consistent with your proposed drive mechanism)
How long would it take to reach Earth orbit from the point where it is spotted?
(For some strange reason, being ill seems to have released the writer's block that I've been plagued with for ages. Maybe it's because my brain knows it's not quite well enough to work on anything serious - though I do seem to be gaining ground on the email now - and thus it's freed me to write)
I'm working on a story in which an alien ship is entering the solar system. The crew have been in relativistic flight from a plant at a convenient plot distance (close to us, but not next door). The ship is now decelerating (and may have been for a long time).
It can have any drive system that anyone cares to propose as long as it is reasonably plausible.
How far out is it likely to be spotted? (Consistent with your proposed drive mechanism)
How long would it take to reach Earth orbit from the point where it is spotted?
(For some strange reason, being ill seems to have released the writer's block that I've been plagued with for ages. Maybe it's because my brain knows it's not quite well enough to work on anything serious - though I do seem to be gaining ground on the email now - and thus it's freed me to write)
no subject
See: http://www.neofuel.com/optimum/
Where Anthony Zuppero claims that a specific impulse of 160 is optimum.
But he was analysing it in terms of a much lower delta-v for a Mars mission.
In any case the difference between SI of 200 and 800 isn't enough to make an appreciable difference to the order of magnitude of the fuel requirement. I think you need an exhaust velocity several orders of magnitude higher, well beyond even what an ion drive produces. Ideally, the exhaust velocity should be roughly equal to the total delta-v, i.e 1/1000 c.