Slow down with engine

[Ecdarksky]

Hi guys i would like to find a way to calculate how much time my rocket gonna need to stop. We are going to say that the horizontal speed is 0.

Thanks for helping me out.

Edited August 28, 2016 by Ecdarksky

[Sonny_Jim]

Although I'm not 100% sure what you are asking, you can always use a maneuver node to show you how long a burn time is.  There's a few caveats, mind.  The node time doesn't take into account multi-stage burns and also sometimes you'll need to throttle up for a short while to get the burn time.

 

EDIT:  Or are you asking how long a suicide burn will take?

Edited August 28, 2016 by Sonny_Jim

[DD_bwest]

in map view there is an icon you can hover your mouse over thatll show you your current max accelleration.   divide your current velocity by that lol

or get a mod to do it lol 

[dire]

Your suicide burn always takes about 3 seconds and 20% more dV than you think it will

[Warzouz]

13 hours ago, dire said:

Your suicide burn always takes about 3 seconds and 20% more dV than you think it will

"than you planned"

 

Seriously, the OP question is not that precise : do you have difficulties to land ?

To learn landing (awfully unefficient but good to learn slowing down) :

- Set your orbital speed to "Surface"

- Target retrograde (SAS)

- Stop your horizontal speed (yes I know that's ugly...)

- Let you fall down, control your speed so it doesn't go over 100m/s

- when you see scatters, reduce to 50m/s

- when you see your shadow, reduce to 20m/s

- Try to touch down around 1m/s

It's best to practice on Minmus, then on Mun

 

Now, an efficient suicide burn

- Do a light deorbit burn so you touchdown point would be between 90 and 180° (I usually set around 120°). Check that your projected orbit don't cross cliffs or mountains.

- At the location of the touchdown point, set a node and pull the retrogade handle until it flips

- The total burn duration is a good approximation of your suicide burn starting time.

- So timewarp, then start burning when your are at the duration of the burn. Discard the node, it's not useful any more. Just follow retrograde.

- This technique has reasonable margin (depending on your ship TWR), so don't hesitate to stop burning if you feel you're too high.

- Again, control you speed to be around 50m/s when you see scatters. As you go mostly horizontal, the ground will arrive much slower than with the previous technique. Land around 1m/s if you can.

 

You'll see that you can start burning safely even you passed the burning duration : it's an optimistic approximation. When you are easy with this technique, you can learn precise landing which is much much easier with this technique than with the previous one.

To do a precise landing : your touchdown location should be few degrees farther than your target location, but must pass above it. After de orbiting, adjust your normal so you still fly above your location. Don't forget the body also rotates. Orbit that matches may not do so in few minutes. So do slight correction burns before the real suicide burn.

Decelerate on map view and check your projected landing point and real location converges. If it don't converge fast enough, burn downward (radial-in). I you're too short burn upward (radial-out). The farther you adjust the cheapest it is.

With little practice, you should be able to select one crater on the Mun (even the smallest ones) and land into it (that means around 1km range).