Spaceplane on a stick keep tipping over

[Jestersage]

I am trying to make an ESA Hermes clone, and for some reason it keeps tipping over, or pitched to the west. May I ask what could be the cause for such to happen?

[bewing]

We would need a craft file to tell for certain. Depending on how bad the tipping is, though -- it may be something you can use. You want to tip to the east, generally. So if you just twist the thing around 180 degrees, that may work out anyway.

[AeroGav]

It sounds like the OP means a small spaceplane launched on the top of a rocket.

The problem is, the spaceplane has wings, which moves the centre of lift of the rocket forward.   Your rocket now has a centre of lift in front of it's centre of mass, so it becomes unstable. 

One way to solve this is to put even bigger wings on the bottom of the rocket itself.

Or you can try gong full Kerbal and putting the airplane at the bottom of the stack.  Trouble is, the airplane ends up with a blunt nose after decoupling the rocket fuel tanks.  I built this in 10 minutes.  It is stable, but it runs out of rocket fuel at just 10km. Maybe with enough effort you could get this to work.

 

In real life they avoided this centre of lift problem , by putting the boosters alongside the airplane.

My Kerbal version -

https://kerbalx.com/AeroGav/Kolumbia

In my opinion these rocket launched airplanes don't work too well in KSP, they combine the worst of all worlds.   You need to be skilled at the rocket launch gravity turn as well as airplane stick n' rudder.

If the orbiter's wings aren't just cosmetic, it means you know how to build an airplane.   And if you can build an airplane, you can build a spaceplane.

True single stage to orbit spaceplanes are hard and require top level tech in career mode.    However you can make an 80% re-usable much easier.

For example, put the jet engine pods on decouplers, and hang them off the wing under the centre of gravity. When they flame out, jettison them.  Without their weight and drag,  accelerating to orbit gets much easier.

Edited October 22, 2016 by AeroGav

[Mikki]

4 hours ago, Jestersage said:

I am trying to make an ESA Hermes clone, and for some reason it keeps tipping over, or pitched to the west. May I ask what could be the cause for such to happen?

You need maybe a large tailelevon on the rocketstage to compensate the winglift/ liftingbody of the Hermes orbiter. It is possible to make it look and work like the original. Design is tricky though.
There are some working Hermes remakes in the Spacecraft exchange, have a shovel?

Here is mine, Hermes on a stick:

http://forum.kerbalspaceprogram.com/index.php?/topic/128332-105-hermes-shuttle-lifterdeorbiter/

Edited October 22, 2016 by Mikki
Link to KERMES

[bewing]

I launch spaceplanes on top of rockets all the time. The thing most people don't seem to understand is that you shouldn't try to gravity turn a spaceplane on a stick -- they are aerodynamically unstable in any other configuration than with the nose pointed straight up. Go straight up until you are at 40km, and they work just fine.

[GoSlash27]

Jestersage,

 A space plane on a stick means that the center of pressure is ahead of the center of mass. As a result, the rocket wants to weathervane backwards from it's direction of travel. Picture an arrow with the fins at the front.

Fixing this will require bigger fins on the back, assuming you want to keep the "plane on a stick" configuration. You can also make it more manageable by accelerating more slowly, but that means your DV budget must be higher to account for the increased gravity losses.

Best,
-Slashy

Edited October 22, 2016 by GoSlash27

[Jestersage]

Yeah, solved that by putting tail wings. Not that I really like it because Ariane 5 (and majority of modern launchers) do not come with wings, but hey, if Dyna-soar put wings on theirs...

22 hours ago, Mikki said:

There are some working Hermes remakes in the Spacecraft exchange, have a shovel?

Here is mine, Hermes on a stick:

http://forum.kerbalspaceprogram.com/index.php?/topic/128332-105-hermes-shuttle-lifterdeorbiter/

Thanks. I spend most of the time on KerbalX instead, and so thought there was no examples of Hermes. Unlike yours, I made mine with Mk-2, since I saw the sample pictures have the spacelab at the BACK of the Hermes..

Been flying my ver.c, which had just finished rescuing one kerbal and may do an Oberth maneuver (?) to rescue another.

On a sidenote, I am also trying to make a CEV-Lockheed, which have a Lifting body return plane, mission module, and service module, in that order. Should I:
1) Use a shroud on top?
2) Have a lab behind it, or just a service bay with the usual science fixings?

Edited October 23, 2016 by Jestersage

[Mikki]

2 minutes ago, Jestersage said:

...On a sidenote, I am also trying to make a CEV-Lockheed, which have a Lifting body return plane, mission module, and service module, in that order. Should I:
1) Use a shroud on top?
2) Have a lab behind it, or just a service bay with the usual science fixings?

Try first without shroud, as @GoSlash27 mentioned, a slower ascend is therefore needed... Cool thing the CEV!
Never heard about this vessel, cannot guess about the gear it has.

[Jestersage]

Just now, Mikki said:

Try first without shroud, as @GoSlash27 mentioned, a slower ascend is therefore needed... Cool thing the CEV!
Never heard about this vessel, cannot guess about the gear it has.

Yeah, and NASA ended up picking Orion. Meanwhile Shenzhou have an autonomous orbital module.

[Foxster]

Another way around the issue if you have a small spaceplane, like a Dynasoar, is to wrap it in a Protective Shell, removing the spaceplane's control surfaces from the airstream. 

Edit: Unless this is what the "shroud" discussion is about?

Edited October 23, 2016 by Foxster

[Foxster]

On 22/10/2016 at 7:20 AM, AeroGav said:

Trouble is, the airplane ends up with a blunt nose after decoupling the rocket fuel tanks. 

You can do something like this to help with that...

...or I suppose this is slightly better...

 

Edited October 23, 2016 by Foxster

[bewing]

Lol! Foxster, you are a nut.

[ForScience6686]

Another thing to try is a small scale shuttle.  I can carry for passengers to lko, and glide back to ksc for full shuttle recovery.  Instead of a belly mounted fuel tank I used a booster stack with srbs on the side.  Balancing thrust wasn't to difficult, but steering isn't to great.  I'll try and get some pics later today.

[GoSlash27]

11 hours ago, Jestersage said:

Yeah, solved that by putting tail wings. Not that I really like it because Ariane 5 (and majority of modern launchers) do not come with wings, but hey, if Dyna-soar put wings on theirs...

Jestersage,

 I agree, but we have access to more advanced avionics than the kerbals do. Without an active alpha hold control loop, the Hermes would've suffered the same problem. Best I can recommend is "hiding" your tail wings by rotating and clipping them inside the tank. I'm not certain that will still work in 1.2. I gotta try it.

Best,
-Slashy

Edited October 23, 2016 by GoSlash27

[ForScience6686]

Here is what I was talking about (sorry it took so long).  Crude early tech shuttle system for my current career.  Handles LKO tourists as well as rescues, plenty of DV to perform 4 rescues if managed properly.  And is suitable for cobra reentry for targeted KSC landing.

 

http://imgur.com/a/5Jmon

 

Crude shuttle system, but works pretty well for the amount of time I put into it.  Easier than the stick method I think, better looking than the inline method IMO as the shuttle aerodynamics are kept in place.  Of course, there are better alternatives, but for the tech level I am at and stage of game, this is working great.