How can i make my planes fly better?

[obtuse urchin]

Hi all, my aircrafts are not good enough and i'm not sure why, i managed to make a plane fly in a kerbin atmosphere but when i take it to mars it just doesn't work. I'm trying to make something like an SSTO to get to mars and back but my planes keep flying backwards and i can't keep them from going engines first in the mars, i had the same issue on kerbin but i solved it with some trial and error and with down scaling the design but now i can't figure it out. Any tips? (btw this is in a sandbox save file with infinite fuel so it's just about aerodynamics)

[turbid zinc]

deploy your airbrakes and look at the CoL and CoM markers again. I bet the airbrakes are making you flip around.

[obtuse urchin]

I'm not using them when landing because of that, but it flips without the airbrakes while i'm trying to enter the atmosphere or move inside of it even before the part where i use breaks. Lowest speed i got without a crash was like 280m/s and at that point i just fell like a rock.

[turbid zinc]

Not sure about the flipping yet, but I do know for sure that plane will not "fly" very well on Duna due to the very small amount of wing surface area. Duna (and mars) have a very thin atmosphere by comparison and need a LOT of wing area to get usable lift compared to kerbin. The opposite is true on eve or any thick atmosphere planet.

Also your vertical stabilizer is not very big, you may consider putting something bigger there

Here is a version of your plane I remade that might fly better

A large delta wing will have more lifting area, also the landing gear are better placed and not as tall

[obtuse urchin]

I did that last time but then i couldn't get off the runway, it felt like i was not suppose to make something bigger because it didn't even need to be in the air to do a flip. I tried to redo the wings and got a little better result but it's still not perfect. I can fly if i'm at 250m/s or more but anything below that the aircraft just spins.

[turbid zinc]

Are you playing sandbox or career/science?

Trying to see what parts you have available

[obtuse urchin]

Ok, but the big flat planes of wings ("connectors") made me spin even more when i tested it last time so i just avoided them.

[obtuse urchin]

sandbox

[turbid zinc]

Spin when taking off or spin while flying?

[obtuse urchin]

I have stock+near future modspack

[obtuse urchin]

both, i might be able to take off but it will spin at some point anyway.

[turbid zinc]

We can get you a good flyable craft, lets take ALL the wings off and leave just the fuselage, cockpit, engines, etc.

A good rule of thumb when designing aircraft is "does this thign look like anything in real life" if the answer is no it probably will have a hard time flying

Something you will notice if you take all the wings off is that your CoM is pretty far back on this plane, because of the big heavy vector engines. This isnt really a problem, but it will dictate what our wings are going to look like and where we place them

[obtuse urchin]

Well, i'm not good at "looks" i just go by funcionality and the only plane i might be able to make is something like the passenger one but with super small wings probably

[turbid zinc]

The goal is we need to add wings that move that CoL to a little behind that CoM marker.

I used a delta wing in my example because its quite far back, and delta wings have most of their wing surface at the rear. However, you can do other layouts too, for example:

[obtuse urchin]

I have one of the small tanks replaced with a cargo bay so it's even further for me, but when the bay was at the back it was flying worst

[turbid zinc]

That's fine let me add that to mine as well, is there anything in there right now?

Okay so, if I try to do different wing shapes, we are still fighting that rearward center of mass, in this example, the wings are too far forward

[obtuse urchin]

Yes, just few cargo containers, it's for repair kits for the mars base.

[turbid zinc]

and if I move them backwards so it works, I basically have a delta wing again but just worse

[obtuse urchin]

This is what i made, the wings are bigger

[turbid zinc]

A little big but in the right spirit

[obtuse urchin]

Ok, the mars has low atmo so are they little big for mars even?

[turbid zinc]

yes and no, while yes its gonna help we're now getting to "too big relative to the rest of the plane".

[obtuse urchin]

Ok, i reduced it by 1 layer and moved the cargo to the back to move the mass forward a bit

[turbid zinc]

I would start with the basics, you need wings for LIFT, and control surfaces for the different axis, being pitch yaw and roll

In my first example delta wing aircraft I have a vertical stabilizer which will do yaw, control surfaces on the outside for roll, and control surfaces on the inside for pitch.

[turbid zinc]

This looks a LOT better

You can even move the whole thing forward a bit, having the CoL TOO far back is also bad, as the nose wants to pitch down constantly.

[obtuse urchin]

Ok, so far it's good, at least on kerbin it seems to not spin in circles as soon as i press S for too long.

[turbid zinc]

Also consider making wings longer front to back vs wide to get more surface area, as that should have less drag as well.

although KSp handles drag different than real life

Try making a wing out of "Connector type A" and "wing type A"

[obtuse urchin]

It seems to fly faster but now when i pressed S the entire thing just desintegrated in less than a second

I used more wing again tho

[turbid zinc]

If the CoL and CoM overlap the aircraft is more manueverable, but, yes if you put too much input it will overturn and break

Yeah with that try adding another fuel tank to extend the fuselage. That will move the COM forward and make it fit the big wing better

[obtuse urchin]

I just made the wing smaller and it helped

[turbid zinc]

And then lets look at your control surfaces, right now you only have one on each wing. I like to use the elevons in game, where my outer ones are for roll, inner ones for pitch, and my vertical stabilizer has one for yaw

Also, with landing gear, try and use the small/medium on MK2 craft like this. I usually put a small under the nose, and mediums under the wings.

Make sure your rear landing gear are just a little bit behind the center of mass. Too far forward and it tips back, too far back and you wont be able to pick the nose up off the runway.

[obtuse urchin]

Like this?

[turbid zinc]

Yeah I tend to do that but KSP is actually pretty good and you dont usually need to make them exclusive to a specific input.

I would try like that and again with all enable and see what flies better

[obtuse urchin]

The gear is as far back as i can place it and the nose goes up on it's own.

After the elevation change i desintegrate again

[turbid zinc]

No need to change it if it works then. If you ever find your craft turning and driving off the runway when trying to takeoff a tip to fix that is to place the rear landing gear on the fuselage itself, and then move them outwards with the movement gizmo to guarantee they are straight and won't flex/bend and therefore steer

[turbid zinc]

Check COM and COL, if they are overlapping too much move the wings back or mass forward. Too close together and it overturns and shreds itself if not careful

I like about this much one most "manueverable" planes

[obtuse urchin]

I did that and it now spins vertically on low speeds again

[turbid zinc]

Here is a plane I made for kerbin flight previously as a reference for some COL/COM placement

[turbid zinc]

Not sure what this means

[obtuse urchin]

nose goes up when i'm pulling down, and it doesn't stop untill it hits the ground/water

[turbid zinc]

That means the center of mass and lift are not set up right. If a craft flips end over end its because the COL is in front of the center of mass or too close. If the COL is too far back then your plane just wants to nose down constantly

[obtuse urchin]

Doesn't look that close

[turbid zinc]

Yeah that plane should fly just fine. Lets check other things then. Is the root part of your plane the cockpit or the drone core?

[obtuse urchin]

cockpit

[turbid zinc]

If the drone core is backwards all inputs would be reversed and can cause stuff like this to happen

[obtuse urchin]

It has pilots at 5 starts too

[obtuse urchin]

I checked already, it's forwards

[turbid zinc]

I just took that plane you made for a test drive, the vector engines are VERY VERY VERY powerful for how small this craft is. Does it fly better if you keep the throttle down and use caps lock to keep the controls slower?

[obtuse urchin]

I don't use caps lock, i just tap the keys, and yes i keep it at about half G force or at the green but it can start and work at full power.

It seems like i have no control once it starts to spin, once it's out of control it can't come back from it unless i make the engines work at full power and just hope that they take me up instead of down faster.

[turbid zinc]

Hmmmmm, I can't think of a reason it wont fly. Can you send a craft file?

[obtuse urchin]

It's against the server rules as far as i know but i think we only have differant elevators at the end of the wings, at least from the pics it seems like it.

I used the big one on the vertical wing and the elevator-1 at the side wings

[turbid zinc]

Okay I built the same thing let me see how it flies

Its a little nose heavy but seems to fly just fine so far

[obtuse urchin]

I tried it on duna and it's much much better now but it doesn't feel like i have control over the direction of the flight once i'm already in the air

Yaw specificly*

[turbid zinc]

I managed to get the aircraft into a stall by overdoing the pitch at slow speed. It tries to put itself into a flat spin if I don't correct it, that might be what was happening to you.

However, thats kinda just a skill issue if thats all it is

[turbid zinc]

lemme try flying on duna real quick

[obtuse urchin]

Ye it wouldn't surprise me, i'm like bottom 30% skill level in a lot of games so it checks out.

[turbid zinc]

The things going against you with this plane and stalling is 1) the vectors are MASSIVE AND WAY TOO POWERFUL for this plane and 2) they have incredible thrust vectoring (hence the name) so they fling your plane around as well as the wing control surfaces.

Try the plane with swivel rocket engines instead

[obtuse urchin]

When i disable the gimbal it's even worst, current problem is that i can't turn really unless i will stall and then do a full burn the other direction

[turbid zinc]

Kerbin or duna?

[obtuse urchin]

duna

[turbid zinc]

I can barely fly this on duna

theres just so little atmosphere

The vertical stabilizer being a full size delta wing puts a decent amount of mass ABOVE the thrust of the engines which doesnt help. In a vacuum that would cause the plane to flip, but any good airflow would stablilize it

[obtuse urchin]

True, i just tried to land and i just went down without gliding as soon as i turned the engines off

[turbid zinc]

Most duna-bound spaceplanes I have seen and made tend to have some sort of VTOL capability for the final landing and takeoff. The wings are very useful for full flight up and out of atmosphere but you cant really land like you can at kerbin, you have to be going pretty quick to have good airflow