Help for my Eve plane

[Tatonf]

Hello !

I've been playing KSP for 3 years but I never used planes until now. Mainly because I don't understand how they work. But now I would like to collect science from multiple biomes on Eve and I'm afraid that using a rocket hopper will be too difficult, mainly because the precision is poor.

So I'm trying to build a plane with ISRU on it, but I can't make it work. Here's the poor monster :

The main problem is that despite the elevon it won't quit the ground, it just roll at 150 m/s before exploding. This on Kerbin and Eve.

So questions are : How do I make it work ? What do you think of it overall ?

Edited July 15, 2016 by Tatonf

[Empress Neptune]

Your main landing gear is very far back. When you try to takeoff, you're rotating around the center of mass until you lift off. The landing gear creates a counter force against the rotation. The further back the landing gear, the stronger the resisting force. This is why real planes tend to have the landing gear near the center of mass.

 

You can also try making the plane sit at an angle on its wheels. If you have enough wing and enough angle, the plane will lift off by itself at speed without any control inputs.

 

The rest of the plane looks workable, but there are some things you might want to change. Adding more lift to the front (and bringing your CoL forward) might make it more agile. Moving your pitch controls to the front can also help with short takeoff because they will create lift instead of downforce. Your vertical stabilizer is very large and might create annoying roll when you try to command yaw. I would make it smaller, or use multiple shorter stabilizers if you really need the yaw stability.

[bewing]

I agree with Empress Neptune. Tails are not important in KSP, like they are IRL. So make that much smaller. Use tailfins or something bigger as canard wings near the nose, and get rid of the large elevons. Add some BigS wing strakes to give more lift. More lift is very important.

[Tatonf]

1 hour ago, Empress Neptune said:

Your main landing gear is very far back. When you try to takeoff, you're rotating around the center of mass until you lift off. The landing gear creates a counter force against the rotation. The further back the landing gear, the stronger the resisting force. This is why real planes tend to have the landing gear near the center of mass.

 

You can also try making the plane sit at an angle on its wheels. If you have enough wing and enough angle, the plane will lift off by itself at speed without any control inputs.

 

The rest of the plane looks workable, but there are some things you might want to change. Adding more lift to the front (and bringing your CoL forward) might make it more agile. Moving your pitch controls to the front can also help with short takeoff because they will create lift instead of downforce. Your vertical stabilizer is very large and might create annoying roll when you try to command yaw. I would make it smaller, or use multiple shorter stabilizers if you really need the yaw stability.

Thank you my plane is now working. Well, except for the piloting part of course. If I turn a little bit too hard my plane is destroyed, I'm loosing control easily, and loosing speed when landing takes forever. I can barely "flare", so I rely on drogue chutes, AIRBRAKES and brakes, and still I think it's too slow. Geez, I really hate planes.

I also tested it on Eve and, well, the atmosphere is too punishing, it doesn't go very far.

[Aegolius13]

If you haven't already, you may want to set the canard controls to "inverted" on the tweakables menu.  The default setting only works right if the control surface is behind the center of mass.  The canard lift may be helping, but it will help more if the point the right way when you pull up!

Also, the Mk 1 cockpit is not a very heat tolerant part, and cockpits tend to bear the brunt of heating.  Maybe go Mk 2, or switch to the inline cockpit and put a nose cone or other heat resistant part in front. 

My experience in Eve is that heat shields are pretty much mandatory, so you're up to a very tough challenge.

[Snark]

It's not surprising that you're having problems-- your plane is a really unstable design.

The CoM is way far back in the back of the plane, with a long draggy fuselage sticking out front.  You're running a regular rocket engine (i.e. not airbreathing), since you're on Eve, which means it's going to drain fuel starting from the front of the ship and working its way back, which is going to just kill your stability, since that will move your CoM rapidly backwards as you consume fuel.

Some suggestions:

• Redesign the plane so that the CoM is approximately in the center of the plane, not way back at the back.  Put the CoL pretty close to that, but just slightly behind.
• Use a single big fuel tank (like the Mk3 LFO tank, or a Big Orange), instead of a bunch of tanks stacked on top of each other.  Have the fuel tank placed so that its center is located right at your ship's CoM.  This will simultaneously solve two problems:  first, your ship will be a lot stiffer (thus solving the bending problem), and, second, you'll stay stable as your fuel drains, because your CoM won't be moving.
• Make sure that you have disabled roll authority on your vertical stabilizer.  It shouldn't be doing anything except helping you yaw.  I'd also suggest disabling everything except pitch authority on your canards.
• Move the airbrakes to the back of the plane.  You want them behind your CoM so that they're not destabilizing you when you use them.

[Foxster]

Personally I'd not bother.

The gravity and drag is high on Eve, so even if you could get your plane there (which I doubt) it would be very hard to fly and land. Without jet engines that fuel you have there is not going to last long. 

There are places on Eve where there are several biomes within a few km of each other. You would be better dropping a science rover in one of those spots and driving around.