Lander woes (lack of instrumentation makes me feel like I'm flying blind)

[vger]

I've been playing with trying to land on Kerbal using only a single liquid engine (and separations in place of a parachute to slow the initial rate of descent) and it seems that no matter how patient I am, I get something going wrong. Either my lateral motion is too great resulting in the lander tipping over, or I land too hard and bounce off the surface.

Now, granted this would be far simpler if I also had monopropellant thrusters to adjust for lateral motion, but it seems I 'should' be able to accomplish this with just the one engine. The trouble I have with landing this way (and I noticed this back in the demo even when I WAS using mono thrusters) is that there is no way to keep track of all the vectors. Even my vertical motion relative to the surface (at the top of the navball) doesn't tell me if I'm moving up or down, but the only way to know my lateral motion is by looking from directly above my rocket, which of course makes it impossible to tell if I'm ascending or descending). If I look at the rocket from the side, I lose perspective on lateral motion.

Any workarounds to this, or perhaps a plugin that solves these problems?

Edited February 23, 2014 by vger
Answered

[Red Iron Crown]

MechJeb has a good surface readout, with altitude above ground level, vertical speed and horizontal speed, among other things. May be more mod than you need, I'm not sure if there are other mods that only provide surface info without all of MechJeb's other features.

I've found it useful to put 4 Illuminator Mk 1s mounted radially in 4 way symmetry on the body of a lander. The four spots of light get closer together as you approach the surface, which can be a useful guide.

[Dave Kerbin]

To the right of the altitude readout there is a vertical speed indicator that you can use to determine if you are going up or down.

[MBobrik]

The trouble I have with landing this way (and I noticed this back in the demo even when I WAS using mono thrusters) is that there is no way to keep track of all the vectors. Even my vertical motion relative to the surface (at the top of the navball) doesn't tell me if I'm moving up or down, but the only way to know my lateral motion is by looking from directly above my rocket, which of course makes it impossible to tell if I'm ascending or descending).

You've got navball to see your deviation from vertical ascent/descent, the shape of the yellow marker tells you whether you are ascending/ descending. it shows your velocity (should be switched to surface speed of course ), and one more gauge is up, right to the altitude display, it's the variometer which shows your vertical speed.

The rest is practice. Just keep the yellow marker in the center of the blue navball hemisphere by "pushing it", and maintain your descent rate through increasing and decreasing throttle.

[Nathair]

Kerbal Engineer, don't leave the pad without it.

[MBobrik]

Kerbal Engineer, don't leave the pad without it.

Yeah. in addition to displaying terrain height, sideways velocity, current and max TWR and stuff, it shows time to impact which can be used to very accurately and safely approximate suicide burns.

[Serratus]

Now, granted this would be far simpler if I also had monopropellant thrusters to adjust for lateral motion, but it seems I 'should' be able to accomplish this with just the one engine. The trouble I have with landing this way (and I noticed this back in the demo even when I WAS using mono thrusters) is that there is no way to keep track of all the vectors. Even my vertical motion relative to the surface (at the top of the navball) doesn't tell me if I'm moving up or down, but the only way to know my lateral motion is by looking from directly above my rocket, which of course makes it impossible to tell if I'm ascending or descending). If I look at the rocket from the side, I lose perspective on lateral motion.

All of those statements in bold are wrong. Currently the game even allows You to execute the entire landing from IVA, especially with radar altimeter. Don't go for the easy way out with mods like everyone is telling You. First try to land by yourself using the pointers from MBobrik.

[Wooks]

Have you experimented with the stock pre-assembled ships on the VAB for practice?

There is the Rover + Skycrane combo: http://wiki.kerbalspaceprogram.com/wiki/Rover_%2B_Skycrane

And you can find a Super Heavy Lander

and a Two Stage Lander

First thing you notice is the engines 4 symmetry configuration. This gives your landers better control over the rate of descent of your ship which is vital to perform hovering maneuvers and emergency take off in case your landing is not going the way you want it. Also placing your engines at the side lowers your center of mass, if you stick one large engine under your lander it may be too tall which is a problem because you can tip over after landing. With this simmetry you can place your fuel around your lander providing a mor stable low center of mass.

This is very important because descending on planets or moons with at least 1G or roughly the same gravity of Kerbin requires higher thrust/weight ratio. On lower gravity bodies you can get away using less engines, even only one below your center of mass. More gravity = more engines is a good rule of thumb.

Second, and this one is the trickiest one, you have to learn to chase your retrograde marker while descending. A succesfull landing requires that the retrograde marker stays right under your ship center of mass (the bottom of your ship). If you are descending and the retrograde marker is not there you have to point your engines to that marker and fire until the marker moves right under your ship. Is the only way to arrest your lateral motion without RCS.

Is a very delicate process, remember to have the Capslock button on your keyboard on, it activates a "fine control" mode that allows you to do more precise maneuvers.

Remember: This sucker under your ship, if its not, point engines to it and burn until it gets under your ship.

The rest is adjusting your speed to touch down somewhere below 5 m/s.

Edited February 25, 2014 by Wooks

[Red Iron Crown]

How do you figure that 4 engines gives you better control? IME, one bigger engine vs many smaller ones doesn't make any difference in controllability.

[Wooks]

How do you figure that 4 engines gives you better control? IME, one bigger engine vs many smaller ones doesn't make any difference in controllability.

I believe you haven´t read what I wrote properly, or maybe I was not clear enough. I´m talking about the weight/thrust ratio that more engines provide in bodies with 1G or 1 gravity similar to Kerbin.

Less engines on a high gravity body requires more thrust and more violent maneuvers, that´s not good at all when you are trying to fine tune a powered landing, much less trying to arrest lateral motion; when performing a powered landing you require a ship that can hover with little thrust so you can maneuver, hover and go up again easily. That´s my point.

I´m editing my previous post just to make the point clearer.

Edited February 22, 2014 by Wooks

[Red Iron Crown]

Less engines on a high gravity body requires more thrust and more violent maneuvers, that´s not good at all when you are trying to fine tune a powered landing, much less trying to arrest lateral motion; when performing a powered landing you require a ship that can hover with little thrust so you can maneuver easily, hover and go up again easily. That´s my point.

I don't see how the number of engines matters. If I have a 200kN single engine or 4 50kN engines doesn't matter if everything else is equal. I don't know what the "violent maneuvers" you mention are about.

Or did you miss the part where I said one bigger engine vs many smaller ones?

[Streetwind]

Yeah, it doesn't really matter for control. But I generally find that I can more easily fit 4 smaller engines on the outside than 1 large one underneath. You want your lander to have a wide stance and a low center of mass so it doesn't fall over when landing on uneven surfaces in low gravity. Building outwards in 4-fold symmetry assists that.

[Wooks]

I don't see how the number of engines matters. If I have a 200kN single engine or 4 50kN engines doesn't matter if everything else is equal. I don't know what the "violent maneuvers" you mention are about.

Or did you miss the part where I said one bigger engine vs many smaller ones?

I´m just trying to provide easy to use tools to the OP and the stock ships are there and ready to experiment with, I have no doubt there are other ways to perform powered landings and more experienced players surely will know how to change engines to their own needs (I surely do myself), but if you are taking your first steps into this kind of maneuver then is better to use already available tools.

Please stick to the OP question and try to solve it, is a better use of our time and we can avoid a very pointless discussion about personal tastes on design.

Edited February 22, 2014 by Wooks

[Wooks]

Yeah, it doesn't really matter for control. But I generally find that I can more easily fit 4 smaller engines on the outside than 1 large one underneath. You want your lander to have a wide stance and a low center of mass so it doesn't fall over when landing on uneven surfaces in low gravity. Building outwards in 4-fold symmetry assists that.

More or less my point, and thanks for mentioning the low center of mass, I forgot to add that to my original post.

[HarvesteR]

The key thing you have to do to nail a landing with zero lateral movement is this: Chase the Retrograde Marker.

As you begin your powered descent, you'll notice that by thrusting laterally to the surface (initially pointing retrograde but not changing attitude), your retrograde marker on the navball will start to go up into the blue half. This happens because as you lose lateral speed, your vertical speed component will become ever more dominant.

It's tempting at this point to just flip perfectly vertical and try to hover into a landing, but the easiest way to make sure you're thrusting towards the direction that will most definitely slow you to a stop, is to always chase the retrograde marker.

Now, keep in mind the speed reading on your navball can read relative to the surface (which takes into account the rotation of the planet), or relative to orbit (which doesn't). For the Mun, which only has about 9m/s surface speed at the equator, this may not seem important, but those 9m/s when touching down can very much tip you over, if not even smear you across a patch of surface.

So, make sure your navball is reading 'surface' as you're about to touch down. This usually happens automatically, but you may inadvertently click the speed reading sometimes and disable the auto mode switch, which is why you have to keep an eye for that sort of thing. The speed reading also affects the velocity markers, so this is very important for final touchdown, otherwise you won't be slowing to a complete stop as you near the surface.

With all that in mind, you have everything you need at your disposal to pull off perfect landings. Keep SAS on to make your life easier (mind the batteries if you don't have solar panels though, or engines large enough to have alternators), and chase that retrograde marker until it is dead center on the navball's zenith point (straight up).

TL;DR:

Keeping it short though, as long as you're in surface speed mode and always decelerating while pointing towards your retrograde vector, you're bound to pull off a dead-stop landing.

Hope this helps

Cheers

[Wooks]

Hope this helps

Cheers

God has spoken, all hail HarvesteR.

[Red Iron Crown]

Please stick to the OP question and try to solve it, is a better use of our time and we can avoid a very pointless discussion about personal tastes on design.

Sorry, I was asking a genuine question. When you said "This gives your landers better control over the rate of descent of your ship" when talking about 4 way symmetry I thought maybe you knew some subtlety of control multiple engines provides that I didn't know about.

[Wooks]

Sorry, I was asking a genuine question. When you said "This gives your landers better control over the rate of descent of your ship" when talking about 4 way symmetry I thought maybe you knew some subtlety of control multiple engines provides that I didn't know about.

No problem, I´m a non native english speaker with good intentions, sometimes I sound harsher than I should and you helped me understand I didn´t make my point clear the first time.

Edited February 22, 2014 by Wooks

[vger]

Yeah, it doesn't really matter for control. But I generally find that I can more easily fit 4 smaller engines on the outside than 1 large one underneath. You want your lander to have a wide stance and a low center of mass so it doesn't fall over when landing on uneven surfaces in low gravity. Building outwards in 4-fold symmetry assists that.

Aye, I could've just given it wider legs, but I was more or less going for an Apollo setup in this case.

It's tempting at this point to just flip perfectly vertical and try to hover into a landing, but the easiest way to make sure you're thrusting towards the direction that will most definitely slow you to a stop, is to always chase the retrograde marker.

Totally hadn't thought of that, and yep, it worked like a charm. Only spent a 4th of my fuel before touchdown on the first try with this.

MechJeb has a good surface readout, with altitude above ground level, vertical speed and horizontal speed, among other things. May be more mod than you need, I'm not sure if there are other mods that only provide surface info without all of MechJeb's other features.

I had it installed but apparently hadn't found the surface detail switch yet. That made life a lot simpler and once I was using that for readings, I managed to hover about 1k back to the space center and land right smack dab on the helipad.

*

I think you all solved my problem. Thanks a ton! (but while we're on the topic of 'solving' things... am I supposed to be able to set this thread to "solved" now?)

Edited February 22, 2014 by vger

[Claw]

I agree with running MechJeb or Engineer. I don't let MJ land, but I use the data readouts. I find it too tedious and laggy to constantly switch between ship view, IVA, and the map when trying to navigate.

Plus IVA doesn't help when landing a probe because there is no IVA. And I find the stock vertical readout isn't very fine when moving heavy ships.

I also built a wide lander base when first learning the layout I prefered when using extra instrumentation.

Either way, I recommend picking one and sticking with it for a while. Roung through a lot of crashes and eventually you'll find a method or mod you like.

[m4rt14n]

Edit thread, go advaced mode. Make sure you're not on a mobile view. Then change status title or something to answered.

Btw IVA mode gives u radar whih tells u the actual altitude. Cheers..

[MarvinKitFox]

What also helps is to have more forgiving legs.

Building legs from heavy construction girders is not very efficient, but they allow landings (intact) of 30m/s and survivable up to 35 vertical + 65 horizontal.

[capi3101]

MarvinKitFox has given you a good suggestion - as has others: shorten and widen your lander. It'll be less prone to tipping over that way. It's perfectly legit (and doable) to stick your lander legs out on Modular Girder Segments or I-beams,

As far as the multiple-engine question is concerned, I'm kinda up in the air. Since you can't control the individual throttles of each engine in game, all that they would do is provide additional thrust. Which is not necessarily a bad thing, depending on what body you're landing on - Mün, it could come in handy. Minmus, probably not. Gilly you could land on with RCS...

Chasing the retrograde marker is key, as others have suggested. The rest is practice. I'd say more but I gotta run; maybe later if you're still having issues.

Mechjeb and KER are not necessary for landing, but they sure help an awful lot.

[Jouni]

As far as the multiple-engine question is concerned, I'm kinda up in the air. Since you can't control the individual throttles of each engine in game, all that they would do is provide additional thrust. Which is not necessarily a bad thing, depending on what body you're landing on - Mün, it could come in handy. Minmus, probably not. Gilly you could land on with RCS...

I like landing on Minmus with TWR 20+. With enough thrust, you can control your speed with quick taps on shift and ctrl, without the delay caused by the slow throttle adjustment. And if you are about to fall over, you can easily escape the situation by using a bit more thrust.

The downside is that you can't hover in place, because throttle adjustments are so coarse. I would never do that anyway, because it feels so wasteful. Like leaving the tap on while brushing your teeth.

[Kryxal]

With single-engine landers with high TWR, I usually throttle the engine down FROM the engine once I'm near the surface ... it makes finer control easier, but I wouldn't want to do that near the surface with multiple engines...