Problem Sc3 aerodynamics

[T.Neo]

I am making, basically, a rocket. It will reenter base first, -backwards. However, when I fly it in Orbiter, it behaves like a Deltaglider. :hmm:

I try to delete the aerodynamis code, but it still flies like a Deltaglider.

The closest thing it resembles is a capsule reentering backwards.
This is a screenshot of the 3d model in Anim8or.

I don't want any fancy lift, maybe just a COG offset for steering during reentry. I don't want it to start flying backwards on the way up!

How do I fix this?

 

[Tommy]

Use capsule aerodynamics, not winged

 

[T.Neo]

But I thought capsule aerodynamics were not fully implemented and caused a CTD?

 

[Tommy]

Guess I'm not sure with SC3. To be honest, it's not really much harder to learn enough C++ to make a .dll than it is to do up a ship in SC3. Orbiter's SDK and API is so complete it's almost trivial, even for someone who isn't a coder, like myself.

At any rate, I'd try capsule aerodynamics in SC3 (capsule aerodynamics has been around forever, in fact it's "depreciated" but still works in orbiter) and see if it works.

 

[T.Neo]

I have managed to remove the control surfaces. :woohoo:

I have started to change the lift settings, but I have very little idea of what to do to make it work.

Here is the current Aerodynamics section of the ini:

[SIZE=2][SIZE=1][AERODYNAMICS][/SIZE]
[SIZE=1]MODEL:capsule [/SIZE]
[SIZE=1]; lift/drag attack point of the vertical airfoil[/SIZE]
[SIZE=1]VAIRFOIL_ATTACK=(0,0,-0.0)[/SIZE]
[SIZE=1]; wing chord length of the vertical airfoil[/SIZE]
[SIZE=1]VAIRFOIL_CHORD=0[/SIZE]
[SIZE=1]; wing area of the vertical airfoil[/SIZE]
[SIZE=1]VAIRFOIL_AREA=0[/SIZE]
[SIZE=1]; wing aspect ratio of the vertical airfoil[/SIZE]
[SIZE=1]VAIRFOIL_ASPECT=1.5[/SIZE]
[SIZE=1]; lift/drag attack point of the horizontal airfoil[/SIZE]
[SIZE=1]HAIRFOIL_ATTACK=(0,0,-4)[/SIZE]
[SIZE=1]; wing chord length of the horizontal airfoil[/SIZE]
[SIZE=1]HAIRFOIL_CHORD=0[/SIZE]
[SIZE=1]; wing area of the horizontal airfoil[/SIZE]
[SIZE=1]HAIRFOIL_AREA=0[/SIZE]
[SIZE=1]; wing aspect ratio of the horizontal airfoil[/SIZE]
[SIZE=1]HAIRFOIL_ASPECT=1.5[/SIZE]
[SIZE=1]; surface area of aileron[/SIZE]
[SIZE=1]AILERON_AREA=0.0[/SIZE]
[SIZE=1]; lift change of aileron[/SIZE]
[SIZE=1]AILERON_LIFT=0[/SIZE]
[SIZE=1]; lift/drag attack point of left aileron (right aileron deduced by x -> -x[/SIZE]
[SIZE=1]AILERON_ATTACK=(0,0,0)[/SIZE]
[SIZE=1]; surface area of elevator[/SIZE]
[SIZE=1]ELEVATOR_AREA=0[/SIZE]
[SIZE=1]; lift change of elevator[/SIZE]
[SIZE=1]ELEVATOR_LIFT=0[/SIZE]
[SIZE=1]; lift/drag attack point of elevator[/SIZE]
[SIZE=1]ELEVATOR_ATTACK=(0,0,0)[/SIZE]
[SIZE=1]; surface area of rudder[/SIZE]
[SIZE=1]RUDDER_AREA=0[/SIZE]
[SIZE=1]; lift change of rudder[/SIZE]
[SIZE=1]RUDDER_LIFT=0[/SIZE]
[SIZE=1]; lift/drag attack point of rudder[/SIZE]
[SIZE=1]RUDDER_ATTACK=(0,0,0)[/SIZE]
[SIZE=1]; speed brake maximum drag change[/SIZE]
[SIZE=1]SPEEDBRAKE_DRAG=0[/SIZE]
[SIZE=1]; speed brake drag attack point[/SIZE]
[SIZE=1]SPEEDBRAKE_ATTACK=(0,0,0);[/SIZE]
[/SIZE][SIZE=2][SIZE=1][/SIZE]
[/SIZE]

EDIT: it still won't want to fly backwards, and still produces lift! :huh:

How can I get it to fly backwards? I need a neutral ship!

P.S: another issue: when I launch, and then come back down, at a high speed, my touchdownpoints sink below the surface, and then I rebound fast enought to cause aeroheating plasma? How can I fix this?

 

[MajorTom]

Put your airfoil attack points downstream of your cg. Think of it as the tail feathers on a badminton birdie or an arrow. You can't get an arrow to fly backwards, can you?

So set up your harfoil and varfoil attack values to be positive Z values, not zero or negative, if you want your rocket to come down tail first. And give them some positive area (say 1 square meter each) or you'll not get any drag, which you'll need to slow down.

I wouldn't use capsule aerodynamics in sc3. There is a CTD possibility, and I'm not convinced that capsule aerodynamics simulate capsule re-entry any better than "space plane" aerodynamics. I just don't declare any particular aerodynamics model when I use sc3.

 

[T.Neo]

Capsule aerodynamics did not really change anything. Setting the hairfoil and vairfoil to positive must have done the trick, as it will fly backwards during reentry, and it doesn't try to fly backwards on launch. However, she doesn't have enough drag. I aimed for florida, crashed in the gulf of mexico, and kept on dragging along the ground, well into the mid United States. :blackeye:

I guess my vessel mass hasn't been set right either. Better fix that...

EDIT:

If the widest point at the base of my vessel is 14 meters in diameter, and I think it is 153 meters square surface area, will setting hairfoil and vairfoil area to 153 give my vessel the right drag?

 

[BrianJ]

Hi,
leave the "MODEL=capsule" out.

Increasing the size of the airfoils will increase drag, so will using a higher value for the drag coefficients.

VAIRFOIL_WAVE_DRAG=4
VAIRFOIL_CD0=4
HAIRFOIL_WAVE_DRAG=4
HAIRFOIL_CD0=4

You may find you need to cancel the default lift parameters for the airfoils (unless you want lift)

HAIRFOIL_LIFT_1=(-180,0)
HAIRFOIL_LIFT_2=(0,0)
HAIRFOIL_LIFT_3=(180,0)
VAIRFOIL_LIFT_1=(-180,0,0)
VAIRFOIL_LIFT_2=(0,0,0)
VAIRFOIL_LIFT_3=(180,0,0)

Good luck,
Brian