Precise landings

[Lunar Sea]

Is there a way (mod) that can show you the impending point of impact/landing in the normal view? It would be *so* much easier to keep my landing profile on point if I could actually see where the spacecraft is going to end up. 

[Chakat Firepaw]

The Trajectories mod will do what you want.

 

[Jarin]

1 hour ago, Chakat Firepaw said:

The Trajectories mod will do what you want.

 

"in normal view", Trajectories is wonderfully useful for re-entry on Kerbin, but doesn't help aiming landings elsewhere and only works in map view, so no local precision. @Lunar Sea, I go the other way. Rather than showing my descent to a particular point, I use Throttle Controlled Avionics' landing calculator to set where I want to land, and it handles the braking and landing. It's a bit complicated to learn though, so might not be your best choice.

Edited February 9, 2017 by Jarin

[Wadusher0]

Better Burn Time gives you a time to impact as well as a countdown to start a suicide burn. It's also a lot more out of the way and convenient than something like Throttle Controlled Avionics.

I still find it tricky to land in precise locations, but maybe that's just my piloting. Either way, its a lot easier than without it.

[Superfluous J]

NavHud is great for this. It puts a prograde and target (if you targeted the landed base) right on the screen and you can make sure the former is going EXACTLY at the latter. It's not exactly what you want but it does make it a lot easier once you're used to the interface.

[HebaruSan]

I like NavHud for this. It doesn't quite predict where you'll land, but it does show your velocity vector in relation to the terrain, so if you zero out your horizontal speed, you can see exactly where you'll touch down.

 

[Lunar Sea]

5 hours ago, 5thHorseman said:

NavHud is great for this. It puts a prograde and target (if you targeted the landed base) right on the screen and you can make sure the former is going EXACTLY at the latter. It's not exactly what you want but it does make it a lot easier once you're used to the interface.

Oh cool, actually that is almost exactly what I had in mind I just didn't articulate it well. 

[Lunar Sea]

5 hours ago, 5thHorseman said:

NavHud is great for this. It puts a prograde and target (if you targeted the landed base) right on the screen and you can make sure the former is going EXACTLY at the latter. It's not exactly what you want but it does make it a lot easier once you're used to the interface.

Damn bruh this is exactly what I needed - I just pulled off my closest landing yet, within 20m of the base! On a more or less direct descent path too because usually I wind up coming down in the general vicinity of the target at best, then hold radial out while basically hovering and flying over it. Well those days are over now! Thanks! 

[Snark]

7 hours ago, Lunar Sea said:

Damn bruh this is exactly what I needed - I just pulled off my closest landing yet, within 20m of the base!

Glad it worked out for you! 

Sounds like NavHud is a better fit for your use case and play style than BetterBurnTime is.

However, just for anyone else who's reading this for precision-landing advice, here's how to use BetterBurnTime for precision landings:

1. Put your ship on a suborbital trajectory with the projected surface impact located slightly eastward of the desired landing point, i.e. so you're on track to overshoot the target somewhat.
2. When you're a couple of minutes out from surface impact, the BetterBurnTime "time to impact" display will pop up next to your nav ball, in the same spot that the "time until maneuver" is usually displayed.
   • Caveat #1, this is the time until impact assuming you just free-fall all the way down (which of course you won't be doing).  Just something to be aware of.
   • Caveat #2, BBT currently uses a simplistic model that just looks at the terrain elevation directly under your current position.  This works great if you're flying over fairly level terrain, but if the ground is sloping steeply upwards or downwards under you as you fly above it, this will cause the projected time to change.  TL;DR:  if you're flying over upward-sloping ground, the actual time to impact is sooner than BBT says it is.
3. Now put your navball into "surface" mode, if it isn't already.
4. Pitch/yaw your ship so it's pointing in preparation for landing.  Roll the ship until the horizon on the navball is, well, horizontal.
5. Look at where the marker is, relative to the target marker.  The should be directly below the (i.e. not to the left, not to the right).  If it's not directly below, you need to correct your aim a bit.  Thrust or as needed to slide the left or right so that it's lined up directly below the .
6. Okay, now you're correctly aimed left/right.  You only need to worry about undershooting/overshooting the target.  Set your SAS to "hold retrograde" and proceed as described below.
   • Watch how the and markers move (i.e. slide along the surface of the navball) to tell how you're doing, as described below.
   • In general, what you will see is that your will slide closer and closer to the zenith (as your trajectory gradually curves towards the vertical).
   • The will generally slide toward the zenith if you've done it right.
   • What you want is for the and to both reach the zenith at the same time.  Until that happens, the should stay below (i.e. farther from the zenith than) the all the way down.
7. How to tell if you're overshooting:  You see the marker moving too fast towards the zenith, so that it's clear it will reach (and pass) the zenith before the gets there.
   • If this happens, fix it by starting your burn early.  This will cause the to move more more quickly towards the zenith.  Burn enough that it "catches up" and looks like it will be hitting the zenith at the same time as the .
8. How to tell if you're undershooting:  If the is actually sliding down (away from the zenith), or else your is moving up towards the zenith too quickly, so that it looks like it will pass and end up above it rather than below it.
   • If this happens, fix it by briefly switching your SAS to hold instead of .  With your SAS in "surface" mode, this will cause your ship to rotate so it's pointing straight up at the zenith.  Fire your engines, which will cause your to slide downwards, away from the zenith and towards the horizon.  Do this enough that you seem back on track again, then switch SAS back to hold .
   • If you're only slightly under-shooting, you don't need to rotate all the way to the zenith.  Just put SAS into "hold current" mode, rotate the ship so it's pointing slightly zenithwards of , and thrust that way to adjust.
9. To do the actual landing:  make sure SAS is in "hold " mode, wait until the estimated time to impact is ~70% of the estimated burn time, then max your throttle.  As you approach the surface, adjust the throttle a bit to fine-tune your drop velocity so that you land as desired.
   • The one tricky bit is that you may be needing to do the undershoot/overshoot corrections (for #8 and #9) as you're doing this.  You can just leave SAS in hold-retrograde, and manually steer towards/away from the zenith to adjust as needed.
   • This is the part that gets better with practice.

Note that all of the above will work fine even in stock, without BBT... it just means that you'll need to visually estimate when to start your burn in step 9, instead of letting BBT tell you.  There are games you can play with maneuver nodes to take some of the guesswork out of that for you.

[Lunar Sea]

Well right now NavHud is definitely the "where have you been all my life" mod for me

but I did actually just install BBT last week and it is a very useful mod too as it allowed me to realize my dream of doing the final landing burn exclusively with separatrons. It is quite the hoot to peel off that last 300m/s in 5 seconds. One time I got it so close the spacecraft didn't even have time to pitch over before it hit the ground (at like, 0.2m/s).