Flight Question Delta V vs Time and Distance

[othoudt]

I ran across an equation in a How to Land on the Moon tutorial video (which I since lost) that would calculate how far prior to the base you should apply retro thrust at a known velocity for a known -acceleration. The result was that your ship would arrive over the base with a velocity of 0 mps. It was a fairly simple equation but I didn't write it down. Does anybody know it? Thanks

 

[TSPenguin]

There is actually a replay in orbiter called "Lunar Transfer". It contains those equations too.
In the corresponding .atc file lines 436 and 437 contain the useful information

349990 NOTE When to start decelerating? Let's try a bit of mental arithmetic: The current ground speed is about v = 1200m/s. Our main engines now produce an acceleration of about a = 20m/s²...
350010 NOTE This means that it will take t = v/a = 60s to kill the ground speed at full main thrust. In that time we will cover a distance of x = vt - ½at² = 40km. We must start the deceleration burn before getting closer than that to the base (or correspondingly earlier if you want to use the less powerful retros for braking).

You might also want to look into EquationMFD.

Happy Orbiting

 

[othoudt]

That's the one Penguin! Thanks a bunch.