any way to fix wrong manuver node times?

[robopilot99]

When I create a new maneuver node the estimated burn times are always completely wrong. Job just got killed because I started a suicide burn to late. Does anyone know of a mod or something that fixes this?

Edited May 17, 2014 by robopilot99

[TechnicalK3rbal]

Fire the rocket in a quick brst, it should reset it.

[SRV Ron]

Fire the rocket in a quick burst, it should reset it.

Sometimes that works, other times it doesn't.

Do a quick save before planning a maneuver that you are unsure of. That way, if it fails, you will have a better picture of when to start your burn for the planned maneuver.

[Dave Kerbin]

It would be easier if you figured out why they where wrong instead of assuming there was a bug. The burn times are based on the engines last recorded performance and as long as your ship doesn't change the burn time will be accurate. There are several things that could change or distort the original estimate:

If you use staging or otherwise detach parts of the spacecraft during a burn then the mass of the ship changes and the burn time won't match the estimate which was based on the original mass plus the fuel that would be burned.

If you add or remove engines during the burn (for example half of your engines have less fuel and will flame out) then it changes how quickly the ship can accelerate which again invalidates the original estimate.

You can also throw off the estimate if the starting information is not correct. If you where previously burning the engine at half throttle, or you staged after ending your last burn, then the information about how much thrust and isp your ship has will be not be correct.

Those figures can also be thrown off by a ship design that flexes while under burn. You might wonder why the game doesn't simply take the engines thrust stat directly and use it - that's because the textbook thrust of the engine is not always what you'll get in a given design. For example if you angle your engines slightly outward then not all of the thrust is being directed in the direction you want to go and so the real thrust is lower. The same happens if your ship flexes or twists while under thrust, the engines won't be perfectly aligned and the true thrust contributing to the maneuver can be variable.

Because you said the burn times are 'completely wrong' rather then just off by a small amount, and because you say this is happening when you are burning for a landing I suspect that you have decoupled some engines or fuel tanks that you used to get into orbit but have not fired your engines since. This means the games information about your engines is out of date - it has no way of knowing correctly predicting the performance of your 'new' ship until you fire the engines with the new load and structural design.

[juanml82]

When I create a new maneuver node the estimated burn times are always completely wrong. Job just got killed because I started a suicide burn to late. Does anyone know of a mod or something that fixes this?

Mechjeb has an option to show the actual burn time, but it's not shown by default, so you'll need to customize one of the windows. Really handy.

[robopilot99]

I'll try some of your suggestions. It definitely isn't the ship flexing (its a very simple moon lander) thanks for the advice

[Xavven]

You wouldn't happen to be using a joystick and throttle to control your game, would you? I'm using the Thrustmaster T.Flight Hotas X and the burn time estimates are always completely wrong. This is because cutting the throttle isn't done with a keypress, it's done by rapidly moving the joystick throttle back to the off position. Technically, since it's analog, it reduces the thrust from 100% to 99% to 98% ... to 1% to 0%, and this somehow confuses the heck out of KSP's estimation calculations.

[robopilot99]

That must be exactly what it is thanks for the tip