Hovering - how?

[uncle_jew]

Hello,

I am a beginner trying out the demo. I built a small lander with landing legs, fuel tanks, a liquid engine and RCS thrusters and am trying to learn to hover at the spaceport (like landing on the VAB roof). I understand hovering on the Mun is easier, but getting a new lander there after each crash simply takes too ling

I find hovering _very_ difficult, so I wonder if anyone has good tips on making it easier.

First of all, it is quite overwhelming to just keep track of the position, speed and acceleration at the same time. The spacecraft is at the center of the window, the vertical speed is displayed at the very top, and the current acceleration at the very bottom. The digital speed indicator near the navball is useless, because it displays only the total speed, not the vertical (or horizontal) speed.

Then it's counter-intuitive to steer the lander with W/A/S/D keys, because the horizontal axis is not aligned with the view angle. E.g when controlling an astronaut with a jetpack, 'W' always accelerates away from the viewpoint, and 'S' accelerates towards the viewpoint. But it is not the case with spacecraft. I ended up adding an extra RCS thruster on one side of the spacecraft simply to visually mark its orientation, so when I turn it so that the thruster faces the viewpoint, the 'W' key accelerates away from me. I wish I could paint one side of the lander red and the other side white, so that I could always easily tell which direction the lander is facing.

It's also difficult to arrest the horizontal movement. I can of course accelerate upwards for a few seconds, and when the lander begins descending again, put the SAS into the prograde orientation and fire the engine until the speed becomes zero. But due to the "jump" necessary, this makes precise targeting impossible. Also, if I put SAS into the prograde orientation too soon (before the lander starts descending), the lander tips over and crashes, because the SAS is unable to rotate it back upright quickly enough.

The best method I could find is to put the SAS into radial orientation (this eliminates any horizontal acceleration), carefully control the horizontal speed by tipping the lander with W/A/S/D keys for a second or so, and spend the most of my attention maintaining the vertical speed of 0. But it's still not easy at all

Are there any tips/tricks on how to make hovering easier?

Anyway, I am now amazed that Apollo astronauts only crashed 3 LLRVs during training

Edited October 19, 2015 by uncle_jew

[The_Rocketeer]

It's much easier to make a controlled descent and land than to make a static hover - in fact without pilot aid mods I don't think a truly static hover is possible.

In a rocket-style lander (i.e. not a VTOL plane), it's best to find your retrograde marker on the navball and thrust towards it until your speed approaches zero. In the full game you can set the SAS to track the retrograde marker which makes this much easier. Of course, if you're actually ascending, your retrograde direction will be downwards, so it's important to keep your spatial awareness and not thrust unnecessarily.

Personally, landing a lander on the Mun is very, VERY much easier than flying a VTOL craft of any kind on Kerbin, since all you need to do is control your speed and aim backwards, gravity's lower, and there's no aero drag to tip you over.

Actually hovering at a fixed altitude probably can be done with autopilot mods, but in full-manual mode I generally try to keep the plane moving slowly in the direction I want it to rather than trying to stop and ending up moving in the wrong direction. Check out this video of me flying a VTOL for a forum challenge - I was going for speed, so naturally a full hover wasn't convenient, but to touch down safely I still had to almost kill my horizontal speed.

[Red Iron Crown]

It gets better with practice, like anything.

I found it useful to use the H/N keys to fine tune the vertical speed with puffs of RCS, and I also use the trick you've discovered of mounting a part to tell which rotation is which. You might find it better to press V to cycle to "Locked" camera mode, too.

You're attempting it in the most demanding of conditions, a high gravity world, which makes everything happen faster. You really should try on the Mun, it is much easier with its lower gravity. I haven't played the demo in a while, if it permits it you might try bringing a stack of landers so you don't have to start from scratch each time.

[Snark]

+1 to earlier posters' advice about hovering being Really Hard.

Just out of curiosity, why do you want to hover? Is it just for the challenge of hovering itself, or is it as a means to some end?

Reason I ask: if all you want to do is to land on the Mun, you don't need to hover. Here's the trick: just set your SAS to "hold retrograde", and make sure that your navball is in Surface (not Orbit) mode as you approach your landing.

Your ship will automatically ease into a straight vertical descent as you thrust. Makes your job much easier, since all you need to control is your engine throttle. Don't even need any RCS at all.

Edited October 12, 2015 by Snark

[uncle_jew]

Just out of curiosity, why do you want to hover? Is it just for the challenge of hovering itself, or is it as a means to some end?

1) To land at a precise location (e. g. next to another lander).

2) To find a suitable (horizontal) surface to land (the Mun has some interesting canyons, for example, with not a lot of horizontal surfaces)

3) Just for the fun of it - fly around, look around The jetpack range is too limited.

Also, while we discuss the Mun, how do you "hop" from one location on the Mun to another (specific) location, if the distance is too far for a short hover? The map doesn't seem to let me plan a "launch" maneuver while sitting on the surface.

Currently I just launch at a 45 degree angle in some arbitrary direction, and once the expected flight path appears on the map, fire in the normal/anti-normal direction until the flight path points towards the next landing site, then fire prograde to make the flight path come back to the surface a little past the next landing site.

The burn to adjust the flight path direction is obviously a waste of fuel. Is there a way to know the correct heading, so that I could immediately launch into the right direction?

Edited October 12, 2015 by uncle_jew

[Snark]

The problem is that hovering is incredibly expensive and wasteful of fuel. A minute of hovering on the Mun eats up 100 m/s of dV. It's fine if you're doing it just for the fun of it, but hovering is almost never the "best" answer for a problem.

1) To land at a precise location (e. g. next to another lander).

Better answer than hovering: practice precise landing techniques so that you can just fall out of the sky and land right where you want to. Yes, that's challenging and requires practice-- but it's a lot easier to learn that than to learn to hover, not to mention being cheaper and more efficient. It's a whole 'nuther topic so I won't go into it in detail here unless you'd like to.

(Or just land something with wheels on it so that if you're off by a kilometer, you can drive to where you need to be. Not as good as landing-in-the-right-place, but a lot more efficient (not to mention easier) than trying to hover.)

2) To find a suitable (horizontal) surface to land (the Mun has some interesting canyons, for example, with not a lot of horizontal surfaces)

Better answer than hovering:

- Build the lander low and squat, so that it can stand landing on a fairly tilted surface (as long as it's not a sheer cliff face).

- Give the lander a reasonable amount of reaction torque, so that if it lands on something that's too steep, it doesn't topple over.

- Per the above advice, practice precise landing techniques so that you land somewhere level enough in the first place.

3) Just for the fun of it - fly around, look around The jetpack range is too limited.

Except that it's so hellaciously expensive to hover that you'll probably get better range with a jetpack, especially since you can recharge the jetpack for free by going back to your lander.

If you just want to look around, a cheaper option than hovering is to just do little ballistic hops. Blast off at a 45 degree angle with enough speed to take you however far you want to go, and then land with a suicide burn. Lots cheaper than hovering.

Also, while we discuss the Mun, how do you "hop" from one location on the Mun to another (specific) location, if the distance is too far for a short hover? The map doesn't seem to let me plan a "launch" maneuver while sitting on the surface.

Currently I just launch at a 45 degree angle in some arbitrary direction, and once the expected flight path appears on the map, fire in the normal/anti-normal direction until the flight path points towards the next landing site, then fire prograde to make the flight path come back to the surface a little past the next landing site.

The burn to adjust the flight path direction is obviously a waste of fuel. Is there a way to know the correct heading, so that I could immediately launch into the right direction?

Use the map view and the navball. Here's what I do:

1. Go to the map view and eyeball where I want to go.

2. Visually estimate the direction, e.g. "Okay, it's just slightly north of due east from here. North is 0 and east is 90, so I want a heading of around 75."

3. Look at the navball and note where that heading would be. "Okay, I want to tip my craft in that direction." Ignore looking at your actual ship, the camera angle will confuse you. Just look at the navball. "Oh, okay, there's heading-75 on the navball."

4. Quicksave in case I mess this up.

5. Zap throttle to full power and immediately torque the ship to a 45-degree angle pointing in the direction I want to go.

6. Still in map view, watch the trajectory grow until it gets to the approximate place I want to land, then cut throttle.

7. If I need to fine-tune the trajectory, just coast up to apoapsis and do a little burn there to adjust.

8. Land with a suicide burn.

[kerbiloid]

Throttle Controlled Avionics

http://forum.kerbalspaceprogram.com/threads/107802-Throttle-Controlled-Avionics-2-3-0-1-0-4-Continued

Davon Throttle Control systems

http://forum.kerbalspaceprogram.com/threads/38069-1-0-4-Davon-Throttle-Control-systems-mod

MechJeb / "Translatron" / "Keep Vert".

http://forum.kerbalspaceprogram.com/threads/124336-PART-1-0-4-ON-HOLD-Anatid-Robotics-MuMech-MechJeb-Autopilot-v2-5-3-%28July-6th%29

[Rath]

You can Quicksave by pressing F5 and quickload by pressing F9. This will allow you to only transfer to the mun once and try landing a couple times

PS. The little star by the bottom of the post is the rep button.

[Empiro]

The best way is to use the navball all the way (in surface mode) -- point your craft mostly vertical, but tilt it slightly toward the green retrograde marker (or away from the prograde marker if you're ascending slightly). This will kill off horizontal speed over time. Then, try to reduce the overall velocity as displayed on the navball. If you do both, then you'll be at mostly a hover. However, it's hard to be completely stationary, because the throttle isn't that precise, and you're constantly burning fuel so your craft will get lighter.

[FyunchClick]

1) To land at a precise location (e. g. next to another lander).

Put on a set of rover wheels in addition to landing struts. That way you can land a mile away and leisurely drive over. Saves a bunch of fuel you'd spend on hovering.

[Champ]

First of all, it is quite overwhelming to just keep track of the position, speed and acceleration at the same time.

https://en.wikipedia.org/wiki/Uncertainty_principle ^^

[Dafni]

First, get a joystick. The throttle lever and fine input control helps tremendously.

Then, watch a lot of cupcake lander videos. I believe it's almost impossible to get any better than that. Some of the flying/hovering he does (especially in his combat style videos) is off this planet

Third, practice. As cheesy as it may sound, but only practice will make you improve.