how to reenter the atmosphere with a plane?

[lammatt]

my planes lose control almost everytime when they re-enter the atmosphere: it usually happen at altitude when the reentry effect kicks in

most of the time i have no authority in any axis and it turns into a spin (even if i have RCS to have exerting some torque for me)

- it goes like...it pitches up so hard that i cant push the nose back down even with the RCS on

while sometimes i can regain control before they smash into the ground... it's more than usually that the Kermans become helpless and die...

(the only success i can land my re-entering plane is when i throttle the rockets toward the horizon to raise my velocity vector so that i can have a more shallow angle of descend...but i've seen a lot of youtubers's clips that they can hold their planes' nose pretty well without any thrust during the descend till they reach well below ~10km)

this is the plane i was flying; it's basically the stock Aeris4A with a larger wing and a trailing center of lift and a 3-man cockpit and a few extra intakes

Edited July 23, 2013 by lammatt

[Furiou5]

A lot of times issues like that are caused because the center of lift and center of mass are very far off. One way to combat that is to use smaller tanks and transferring fuel around in the tanks to balance. Another way is to plan for that change of weight by starting with it out in front of center of mass, then it will move back. When entering the atmosphere get your PE around 30km you will aerobrake well without falling too quickly. If you do get out of control cut your power get control by going nose down. Then apply gradual throttle until you are flying level again.

[Kimberly]

This is normal. Your plane is designed for lift, and when you're hurtling through the atmosphere at supersonic speeds, lift is just what you'll get. What you want to do is make your plane as aerodynamic as possible--it means you slow down at a reduced pace, but your plane will stay more or less stable. I think the best way to to do this is to keep the nose pointing prograde. (Even if you want to glide, consider opening your air intakes for increased drag.)

[shand]

i cant say im a big spaceplane user so my solution would be to put a drogue chute on it to bleed off the troublesome speed, gently firing the jet when possible would provide control and help stabilise. once at a flyable speed ect cut the chute and carry on as normal. i find going too fast is the root of most of the problems, most likely due to the aerodynamics in play at this stage

[rioburrage]

First of all, they are Kerbals

It looks like you're pitching up way to much when you're re-entering making the plane pitch up even more because of the lift that your wings suddenly have, entering the atmosphere.

Also never use the physics warp/time warp because it messes up the physics.

Another possible solution is to balance or fill your plane's fuel. I suggest this because the fuel usually drains from the front of the plane again, making the plane become unbalanced and more prone to tipping upwards.

[lammatt]

First of all, they are Kerbals

It looks like you're pitching up way to much when you're re-entering making the plane pitch up even more because of the lift that your wings suddenly have, entering the atmosphere.

Also never use the physics warp/time warp because it messes up the physics.

Another possible solution is to balance or fill your plane's fuel. I suggest this because the fuel usually drains from the front of the plane again, making the plane become unbalanced and more prone to tipping upwards.

no i dont pitch up that early... who would pitch up during a descend when he's ~40km up high anyways

i started pointing at the direction of travel (ie. surface mode velocity vector)

and when the reentry flame kicks in... the plane pitches up uncontrollably even when i push it back down with the help of the mighty RCS

[lammatt]

A lot of times issues like that are caused because the center of lift and center of mass are very far off. One way to combat that is to use smaller tanks and transferring fuel around in the tanks to balance. Another way is to plan for that change of weight by starting with it out in front of center of mass, then it will move back. When entering the atmosphere get your PE around 30km you will aerobrake well without falling too quickly. If you do get out of control cut your power get control by going nose down. Then apply gradual throttle until you are flying level again.

but it'll take forever to land if i attack the atmosphere at such a shallow angle....wont it?

(well... i guess it's still better than crashing tho~)

[Furiou5]

It will take forever, and it should you have to bleed off a couple thousand meters per second... that is a lot of energy.

[Xeldrak]

I had the same problem - I used a chute, mounted at the end of the plane to straighten it out, once its in the deeper atmosphere. I know, thats a rather dirty solution, but it worked

[DaRocketCat]

Drogue chutes are your friend .

And an ejection system (add a decoupler, some separatrons, and a couple chutes on the cockpit) might increase survival rates..

[weekendgamer]

I've noticed the game simulates uneven drag, so it might be because of the intakes on top dragging the top of the plane backwards, pitching it up.

[lammatt]

I've noticed the game simulates uneven drag, so it might be because of the intakes on top dragging the top of the plane backwards, pitching it up.

so if i put the same number of intakes at the bottom... i'll gain my control back next time... true?

[AnalogAddict]

You can also just shut the intakes and that'll reduce their drag coefficient. I agree with an earlier poster, make sure to have a shallow angle of attack or you have a greater risk flipping out.

As a general rule of thumb, if I place intakes on top of my craft, I'll place a matching pair on its belly.

[Rune]

Actually, and take it from an aeronautic engineer, it's rather simple: if you lose control, it's because your plane is not aerodynamically stable. Now, what makes a plane aerodynamically stable? Well, picture the most aerodynamically stable stable thing I can think of, an arrow: how does it make it to keep pointing in the direction of travel no matter what happens? Well, the answer is simple: the center of lift is way, way behind the center of mass. Unlike in the rocket pendulum fallacy, you aerodynamic thingy "hangs" from the center of lift, and is pulled down from the center of mass. That means the center of mass will always try to get before the center of lift in the direction of travel. Which is why opening a chute behind it will always work (a parachute gets greats amount of "lift", or better said, aerodynamic forces).

Now you can go a bit too far, and make your plane too aerodynamically stable. Then what will happen is you don't have enough control authority to make it point anywhere but prograde, and "prograde" will start being more and more "downwards"... very gentle way of crashing, and with a beautifully curved trajectory.

All in all, what I can say is: there is a reason planes are long, and have rear stabilizing surfaces at the end of a tail, well behind the center of mass. And why flying wings are very, very tricky to pull off in the real world without fly-by-wire systems.

Rune. Hope that helps.