Jonathan_S wrote:Though all the 4(+) stage designs seem to run into the light-speed issue.

Normally your descriptions of the missile acceleration, terminal velocity, and powered range seem to ignore relativistic effect (which does keep the math tractable). But if you apply the same calculations that say from rest 540 seconds at 46,000 gees gives you the canonical 0.812c at 65,726,640 km and add a 4th drive the 720 seconds at that accel would give you 1.083 c -- Oops.

Switching to relativistic equations now, in additional to being more of a pain to calculate, would conflict with existing statements about MDM performance.

(My guess was that you'd just declare a fiat 0.9c or so "top speed" with the missile either being incapable of accelerating past that, or automatically destroyed in the attempt, which still allows the final stage(s) to be used for lateral deflections of the missile's course without letting impeller driven objects exceed the local speed of light)

Bill Woods wrote:The problem with that is, 0.9c with respect to what? If a ship going 0.3c one way (relative to some bystander) fires a Mk23 at a ship going 0.3c the other way, at what point does the missile hit 0.9c?

Joat42 wrote:It must first de-accelerate to a stand still before gaining ground on the target, given the acceleration profile set on the missile it is quite easy to calculate the extra time it takes to do that (somewhat accurately if you ignore all the niggly wiggly stuff that starts to happen at relativistic speeds).

I was thinking of two ships heading towards each other, so deceleration isn't an issue.

According to Newton, the launching ship sees the

missile accelerate from zero to 0.81c.

But the 'stationary' observer sees the

missile go from 0.30c to ...

1.1c,

while the target ship sees the

missile go from 0.60c to 1.41c.

Obviously, there's a problem: does or doesn't the

missile exceed 0.9c (or worse, 1.0c)?

According to Einstein, the launching ship sees the

missile go from zero to 0.67c.

The 'stationary' observer sees the

missile go from 0.30c to 0.81c,

while the target ship sees the

missile go from 0.55c to 0.89c.