How to find burn time?

[power5000]

I was wondering how you would calculate how long a "burn" would take if you are given dv needed and isp/thrust/fuel rate or whatever else you need? I'm not sure if the thrust is equal to dv in a second so if your thrust is 150 would your delta-v change 150m/s? or some other number?

Edited October 19, 2013 by power5000

[Depth]

I'm sure you can calculate it in some way but a crude method is to quickly put the throttle to max, try mentally noting the burn time it displays, then quickly cut the engines with the X key.

Normally I take notice on how many dV's you burn per second and try to guesstimate other manoeuvres.

Neither method is perfect and I'd love to see if anyone has some math on this

[power5000]

I actually was poking around the tutorials section, and in the drawing board I found this... http://forum.kerbalspaceprogram.com/threads/40053-Estimate-the-duration-of-a-burn

There is lots of math =)

[Depth]

"I'd love to see if anyone has some math on this"

What was I saying. This is the KSP forum, after all

[nhnifong]

The burn time is the ∆v of the burn in m/s divided by the max acceleration in m/s^2. Cancelling units, your answer will be in seconds.

The max acceleration changes linearly over time as fuel is burned and mass decreases, so the answer is the average between the start and end of the burn.

At any instant, the max acceleration is the thrust in kilonewtons (given in the hover dialogue of a thruster) (Mg * m / s^2) divided by the mass of the rocket in metric tons (also, ksp's default unit of mass, Mg)