Planes/gliders shake uncontrollably on Eve?

[Himynameisjake]

So I have been trying to figure out the best way to move a kerbal about 20km from my landing zone at sea level and up about 7km to a mountain that I take off from to orbit. The immediate solution was a glider as light rovers are notoriously bad on Eve and making a rocket capable of reaching the target on a ballistic trajectory would take very large amounts of deltaV. The problem is, when I try to take planes/gliders to Eve (even ones that are tried and true on Kerbin) they get up to speed and they start to shake. Go slower and I stall, maintain speed and I shake right out of the sky.

I play a stock version of KSP (no FAR or similar). I have my center of lift slightly behind and above my center of mass and I have a reaction wheel on it. I will upload pictures when I get home, but I wanted to ask, is this a known problem (preferably with a known solution).

Any thoughts?

Edited June 18, 2014 by Himynameisjake
answered-ish

[LethalDose]

Do you have SAS on your glider? Also pics, please. It's hard to trouble shoot without knowing what we're looking dealing with.

I'm just curious: Why are rovers "notoriously bad" on Eve. They're a headache on low gravity worlds, I would think they could useable on a high G world.

[asb3pe]

Do you have SAS on your glider? Also pics, please. It's hard to trouble shoot without knowing what we're looking dealing with.

I'm just curious: Why are rovers "notoriously bad" on Eve. They're a headache on low gravity worlds, I would think they could useable on a high G world.

Don't quote me, and I can't quote where I read it (while studying and trying to learn this game), but he said "light rovers" and I believe I remember reading that in higher gravity planets, the wheels literally break off.

I think it's right in the wiki, hang on... yep. It's in the "bugs" section for Eve.

Rovers can be challenging to drive on Eve due to its gravity. The rover's wheels will easily break, but on the upside, since the gravity pulls them lower on their shocks and thus lowers the centre of mass, they will be harder to flip over. Although not a glitch, it could cause clipping issues with a kerbals sitting in EAS-1 External Command Seats

I'll be following this thread because Eve is my next big goal, never been there. It's quite the challenge, I'm realizing! I gotta get going with planes and gliders first, it seems...

Edited June 17, 2014 by asb3pe

[asb3pe]

I dunno if it will help anyone at all, but this reddit post is one I've been saving for quite a while (knowing that someday I would play KSP and probably want to have this sort of information).

Sub's Plane/SSTO Design for Beginners *Long Post*

submitted 10 months ago * by subhumann

[Himynameisjake]

Do you have SAS on your glider? Also pics, please. It's hard to trouble shoot without knowing what we're looking dealing with.

I'm just curious: Why are rovers "notoriously bad" on Eve. They're a headache on low gravity worlds, I would think they could useable on a high G world.

I do have sas, a reaction wheel and a probe core, which should be plenty for a 1ton plane. Light rovers are bad on Eve because they break down A LOT, and in my experience lack the power (at the wheels, I never run out of charge) to get up the big hills.

[cantab]

You might have too much torque. I've found my little asteroid control sections vibrate if they have both reaction wheels and the probe core torque enabled and SAS on when they're unloaded, and that's in deep space. They work fine with no or one wheel enabled.

[technion]

Regarding rovers, I found Eve to be my favourite place for them. I hated going over a hill on the Mun and taking off.

I didn't put any significant thought into making it handle the terrain, but I don't use those small wheels.

[Pecan]

Shakes are usually a sign that SAS is fighting very hard so I suspect the drag/balance of your plane is shifting as it is dependent on speed. The best cure is to turn SAS off and adjust the trim of the plane so that it flies more-or-less stably without that or constant control-input. Hold the 'mod' key (alt on Windows) and the WASD keys to adjust trim, alt-X to reset it. I find that a lot of planes work best with positive (up, alt-S) pitch trim of 1 - 2 notches on the control-indicators at the bottom-left of the screen. The thing is to just check what your plane does without SAS and use trim to counter it - so if it goes into a dive on its own use pitch-up, if it does a back-flip use pitch-down, etc. You might have to re-adjust trim every now and again as your speed/AoA or fuel (if applicable) changes.

Note that a tendency to back-flip often indicates that there is too much drag ahead of the CoM. That's often because of air-intakes but I take it that isn't the case here.

[Mesklin]

When I made my BlueBird Eve lander I found similar problem, not shaking, but stall problem in gliding time. Move COL of your craft more behind COM then usual, as minimum twice, it should partially help. And I recommend to use plane wheels in the front of rover for Eve, like on picture. Wings on Eve work very well and it lighter then bunch of parachutes

[Himynameisjake]

While it's not exactly the result I would have liked (smaller is always better in a component ship), based on the recommendations in this thread, I was able to come up with a ship that met my needs! I present to you my Eve mini-plane, capable of reaching 19km inland and 7km final altitude, basically through sheer will.

Thanks for your help guys!

Edited June 18, 2014 by Himynameisjake
answered-ish

[SlimeCrusher]

Actually, you DO have way too much torque! Try removing that Reaction Wheel, is just too much!

The problem is, that SAS is trying to fix a small move in the craft, but having too much torque it overshoots and has to deal with a worse rotation, and then it starts shaking more and more rapidly

[Pecan]

And have you tried adjusting trim yet, instead of using SAS?

[Himynameisjake]

Actually, you DO have way too much torque! Try removing that Reaction Wheel, is just too much!

The problem is, that SAS is trying to fix a small move in the craft, but having too much torque it overshoots and has to deal with a worse rotation, and then it starts shaking more and more rapidly

That makes a lot of sense! As I was building the thing, I ran into the deliema that the probe cores couldn't provide enough torque to keep me headed in the right direction, and so I added the reaction wheel, which, as you are saying gives me TOO much torque. I wish there was a happy medium

And have you tried adjusting trim yet, instead of using SAS?

I did, and it worked, ish. It cost me some fuel efficiency (because I'm not very skilled in atmospheric craft), but in the end, a combination of trim adjustment and changing wing placement gave me the oomf! I needed to get the job done.

[cantab]

That makes a lot of sense! As I was building the thing, I ran into the deliema that the probe cores couldn't provide enough torque to keep me headed in the right direction, and so I added the reaction wheel, which, as you are saying gives me TOO much torque. I wish there was a happy medium

You could always try adding an extra probe core. An OKTO2 has 13% of the weight and 2.5% of the torque of a standard reaction wheel, so may be good for craft where you want to keep the weight down but need a bit more torque than one core gives you.

[Himynameisjake]

You could always try adding an extra probe core. An OKTO2 has 13% of the weight and 2.5% of the torque of a standard reaction wheel, so may be good for craft where you want to keep the weight down but need a bit more torque than one core gives you.

It needs way more than one extra probe core, I got the results I needed, so I'm happy. If I really wanted to, I could fiddle around with a set of probe cores, but I'm not worried about it. If I didn't need the kerbal to be in a chair, I think a Mk1 command pod might actually be a nice compromise between weight, parts, and torque, but I am going to be carrying multiple science reports of the same type (4x all splashed reports) so I need to be in a chair.