Getting a plane into space as a payload without rocket flipping over

[szputnyik]

I'm trying to send a plane to Eve, but when I launch my rocket, with the plane sitting on top of it as a payload (pointing upwards) the plane's wings and control surfaces seem to interfere with the rocket's stability and I flip over at an altitude of 1 or 2 kms. I'm sure the rocket itself is good, it's a modified version of the Apollo 11 rocket from the tutorials (using 4 ASAS's to both stabilize it and turn it around easily), and I've managed to send a space station core to Eve orbit with it for example, but when my payload is a plane, it flips over.

Do you know how to prevent the rocket from flipping over?

Edited October 4, 2013 by szputnyik

[JerryIRacer]

Take two of them on the opposite side of your lifter. Their aero lift forces are going to cancel themselves out.

[softweir]

I assume the spaceplane is right on top of the rocket? If so, then it is inherently unstable. Think about the fins that used to be put at the bottom of rockets, or the feathers on arrows - if the rocket/arrow starts to turn a bit then fins/feathers drag the back of the rocket/arrow behind the head so it carries on flying in a straight line.

Now imagine an arrow fired backwards. While the arrow is going perfectly straight then it is OK, but the moment anything disturbs it then the drag will try to yank the feathers round so they are trailing the head. The same thing happens when you put a spaceplane on top of a rocket - the drag on the wings can be so large that nothing can correct things if the rocket veers even a little bit off course - EXCEPT for an even larger set of fins at the bottom of the rocket!

In the real world it is possible to build control and navigation systems that will keep a rocket pointing so very directly ahead that unbalanced drag near the nose won't destabilise things. (Indeed, modern fighters are designed to be unstable so they are more manoeuverable, and need high-performance computer-controlled stabilisers to stop them tumbling!) However that is near impossible in a simulation game on a PC.

JerryRacer's idea sound best - strap two spaceplanes either side of the lifter, as far down the stack as you can put them. Alternatively, bolt two small stacks to each wing, one above and one below.

Good luck!

[JerryIRacer]

Hey Szputnyik, on Eve there is no oxygen. Is your plane a rocket one or electric? If its rocket plane strap some additional tanks to it and maybe some solid boosters to get it to orbit. Then dock it to your interplanetary stage and take it from there. But even in space load has to be balanced along thrust axis.

[The Fleet Master]

I used to have this problem, I went through Nasa Archives, More Specificly the Dyna-Soar Launch Vehicel, I noticed if you put large fins on the bottom stage and use that in the thick atmosphere it keeps the rocket very stable.

[JerryIRacer]

Here is what I mean:

This shows what the plane looks like as tested on Kerbin and as intended to be used on Laythe

And here it is after adding some fuel and engines necessary to reach orbit. Also had to add more wings to help to lift the contraption off the runway.

Once I enter Laythe atmosphere I will stage and wings with empty tanks and useless rockets are going to be disconnected. In about 160 days that is...

[kahlzun]

I think only the cockpit on that is stock :S

perhaps it's topheavy? it looks like all your rockets are on top of your plane?

[RoboRay]

Right... your craft has negative dynamic stability from the drag of your wings and other aero surfaces near the front of the rocket.

So, add even bigger aero surfaces to the bottom of the rocket... http://imgur.com/a/RoHw0

[Lohan2008]

My (poor) drone ship looks puny. /weep

[szputnyik]

I have swept wings on my Eve plane, because I thought it would give it some extra lift in the thick atmosphere to stay aloft longer (it only has a small 180 rocket fuel units holding tank). If I put delta wings on the bottom of the rocket, will it be enough to cancel those out?

[bsalis]

Right... your craft has negative dynamic stability from the drag of your wings and other aero surfaces near the front of the rocket.

So, add even bigger aero surfaces to the bottom of the rocket... http://imgur.com/a/RoHw0

You beat me to it. So I will just say "Fins for the win!"

[PeteTimesSix]

Or you could go... a little crazy.

Required a bit of quantum-strutting, but it made the landing back on the runway just fine.

[Geschosskopf]

I made this stubby, clunky biplane with enough wing to fly on Duna:

This huge wing made it totally unable to be launched vertically either singly or in tandem, so in the end I had to build a huge winged ascent stage and fly it horizontally SSTO spaceplane-style, like this:

It needed the huge rear wing to balance all the lift of the plane itself. Funny thing is, this was the easiest spaceplane to get to orbit I've ever made. It was pretty slow and didn't pitch up very much, but it climbed like a champ with all that combined wing area. It was like a truck climbing a hill in low gear, didn't have to fight the controls at all. Then, once it got up to about 20km, it started picking up speed and from there to orbit. Still, it took like 20 minutes .

[rhoark]

The way NASA did it was the Space Shuttle. Side mount.

[Tex_NL]

Most suggestions until now are basically correct. Side-mounting your plane lower makes it less aerodynamically unstable but results in a misalignment between CoM and LoT. Mounting two could solve this but then you'll be carrying a lot more weight. Mounting in on top like you planned to do in the first place is the cheapest and easiest solution IF done correctly.

Most people mount their planes in such a way that before launch the wings are pointing north-south. During your gravity turn the nose of your rocket (the plane) will start behaving like a plane forcing it either up or down. It can be very difficult to counter this.

Instead of the north-south wing configuration rotate your entire rocket 90 degrees and point the wings east-west. In this configuration your wings will be pointing up-down during your gravity turn, the nose of your rocket will not behave like a plane and you keep full control.

[Anton P. Nym]

The glider is called the "Ghost". The launch stack is called "that freak of nature that just shouldn't fly, but does." The key is the set of giant fins (each a delta-wing stock part) at the bottom that pulls the Centre of Lift back behind the Centre of Mass (make the whole thing stable) until the stack leaves the atmosphere and lift isn't a problem anymore. Tricky to fly, but it does work. (I'm going to launch my second one soon, when the Jool launch window opens; that picture is from my Eve-destined launch.)

-- Steve

Edited October 4, 2013 by Anton P. Nym
grammar fix