Help Me Learn How To: Vertical Launch Shuttles/Space Planes (like IRL)

[connocclar]

How can I make a vertical launch "Shuttle" successfully? I'm talking about a Launch stage (the Big rocket with boosters) and a plane (with potential payload) attached to the side of it all. I've tried numerous different times to build them but they always lean to the side of the space plane immediately after launch even when I have the center of mass as perfectly centered as I can get it. HALP MEH!

Edited May 31, 2015 by connocclar

[connocclar]

I have no idea how to get vertical launch Space planes/Shuttles to work. I'm talking about vertical launch stages ( Huge rockets with boosters) and a space plane/Shuttle attached to the side of it. Like IRL Shuttles. I have tried making them before and have centered center of mass and everything but they always fail to launch properly, often just leaning to the side the plane is located on. Teach me how to create proper vertical launch ~3 stage crafts, stage ONE being solid booster ejection Stage TWO being Liquid fuel rocket ejection and stage THREE being the spaceplane/shuttle.

[Claw]

I've merged your two threads but left the posts since they contain slightly different questions/information. As a new member, your first few posts need to be approved. Sorry if that caused any confusion.

Let the flood of information commence. And welcome to the forum!

Cheers,

-Claw

[Lithocirkus]

The trick with making shuttle style launchers is watching your centre of thrust.

Start from the shuttle and build on one stage at a time. While you are coupled to the liquid booster with its solids your CoT should sit below your Center of mass. Check this on the buttons at the bottom of your VAB screen. you change the CoT by changing the thrust limitation on your engines. the shuttle engine should also fire and draw fuel from the liquid stage.

Basically the solid fuel boosters lift your liquid stage while it is heavier than your shuttle, then when the mass of your shuttle and liquid stage are similar you eject the solids and burn until the liquid fuel is gone. The center of thrust will change dynamically during the ascent so the trick is to check each stage and balance them individually.

Edited May 31, 2015 by Lithocirkus
Formatting

[connocclar]

thank you, I was confused when I couldn't find my post for like ten minutes....I'm ignorant QQ.

[connocclar]

So I should time the liquid stage and boosters, so that when the boosters run empty the liquid stage will be the same mass approx. to my shuttle?

[JoCRaM]

In addition to the centre of mass and centre of thrust, you have to account for the drag and lift of your craft. The drag will tend to pull down the side with the shuttle attached. The lift is a whole lot more complicated.

Check this on the buttons at the bottom of your VAB screen. you change the CoT by changing the thrust limitation on your engines.

Unfortunately, the direction of the thrust indicator is broken in version 1.0.0-1.0.2 (the suggested workaround is "have all your engines pointing the same way")

[NikkyD]

I am telling you, it's nearly impossible because i am trying for a day now to get my Rocket-Assisted-Space-Plane into orbit.

Neither MechJeb nor the joke SAS with 10 control surfaces can keep it steady. There is no streamlining effect on the wings, so the whole thing starts wobbling and suddenly there is massive lift on the wings and either you can't compensate for it or the joints break and everything explodes.

I don't think this can be done in 1.0.2 without building a very special plane just for this purpose which is a bit annoying

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Edited May 31, 2015 by NikkyD
added pic

[GoSlash27]

I am telling you, it's nearly impossible because i am trying for a day now to get my Rocket-Assisted-Space-Plane into orbit.

Neither MechJeb nor the joke SAS with 10 control surfaces can keep it steady. There is no streamlining effect on the wings, so the whole thing starts wobbling and suddenly there is massive lift on the wings and either you can't compensate for it or the joints break and everything explodes.

I don't think this can be done in 1.0.2 without building a very special plane just for this purpose which is a bit annoying

NikkyD,

Oh, it's possible. Just a major pain.

http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/shuttle%20konstitution/Kontender

The trick is to align the thrust with the center of mass so that the thrust isn't trying to rotate the launch stack.

Notice here that the main engines are pointed at the center of the CoM's shift and the SRBs are offset slightly toward the shuttle.

It helps to have the tank as far forward as you can manage.

You don't necessarily want more control surfaces to add stability, either. I placed Vernor engines around the launch vehicle and launched with RCS engaged.

Good luck!

-Slashy

[NikkyD]

My problem is NOT the gravity pull but that my huge wings create so much "lift" sideways the second they are 0.1° off 90° that the whole thing flips. Reducing the wings is not an option as they are supposed to be like that. See image above

[Starhawk]

My problem is NOT the gravity pull but that my huge wings create so much "lift" sideways the second they are 0.1° off 90° that the whole thing flips. Reducing the wings is not an option as they are supposed to be like that. See image above

I've never tried to make a shuttle replica, so take what I say with a grain of salt.

I would try to configure the lifter so the wings are as low as possible. They should be as near the bottom as you can manage.

Happy landings!

[GoSlash27]

Oh, just saw your design. I don't know why it didn't come up the first time.

Yeah, unfortunately that's not gonna work that way.

You could try moving the control fins on the boosters from the top to the bottom. That would help some. Perhaps sandwich the plane in between the boosters further down.

You really can't have all that drag in the nose of the rocket like that. It's like trying to shoot an arrow with the fins on the front.

Best,

-Slashy

[NikkyD]

@GoSlash27 it is actually shooting an arrow with a rocket mounted behind the fins. It works for as long as there is no deviation from the course.

All the control surfaces i added to fake more stability but it just prolongs the inevidable. Since 1.0 or dunno which version the whole SAS thing can no longer hold a rocket really steady. If you look at my design, if i use MJs Smart A.S.S and keep the rocket at 90° dead on... well it SHOULD work, but at some point for BS reasons something moves and suddenly the wings get lift and BOOM DEAD.

Sure i could place the wings somewhere where they would fight the mass of the fuel etc pp add controls to counter the "lift" but the issue is the unexplainable sudden wobble and change in direction. I see blue arrows coming up at about 4000m and suddenly BOOM they are really big and everything is a mess. Setting SAS prograde doesnt help, using MJs control doesnt help... the game is broken atm

[GoSlash27]

@GoSlash27 it is actually shooting an arrow with a rocket mounted behind the fins. It works for as long as there is no deviation from the course.

All the control surfaces i added to fake more stability but it just prolongs the inevidable. Since 1.0 or dunno which version the whole SAS thing can no longer hold a rocket really steady. If you look at my design, if i use MJs Smart A.S.S and keep the rocket at 90° dead on... well it SHOULD work, but at some point for BS reasons something moves and suddenly the wings get lift and BOOM DEAD.

Sure i could place the wings somewhere where they would fight the mass of the fuel etc pp add controls to counter the "lift" but the issue is the unexplainable sudden wobble and change in direction. I see blue arrows coming up at about 4000m and suddenly BOOM they are really big and everything is a mess. Setting SAS prograde doesnt help, using MJs control doesnt help... the game is broken atm

NikkyD,

There are a lot of designs that will fly just fine so long as there is no deviation from the course. They are what we call "dynamically unstable".

The problem isn't that you're getting small deviations, it's that your rocket is unstable.

If you build it so that the drag is behind the CoM instead of in front of it, your rocket can handle deviations without going 'splodey.

Best,

-Slashy

[NikkyD]

What you are suggesting is a mere compensation for the whole issue. Why do i get drag sideways ? Because the whole thing wobbles.

[MarvinKitFox]

I have no idea how to get vertical launch Space planes/Shuttles to work.

You need to get the balance, center of drag, thrust and lift *exactly* right, ..... not at all easy

or

You can do it the NASA way. Highly dirigible shuttle engines being re-pointed 16 times per second... not an option in KSP

or

Do it the "hard" way, and restore symmetry to your vehicle. Mount a *second* identical shuttle to the other side.

Forces will balance perfectly now, and you only have the normal rocket instabilities to worry about.

... and the fact that you are lifting twice the mass. ;-)

[GoSlash27]

What you are suggesting is a mere compensation for the whole issue. Why do i get drag sideways ? Because the whole thing wobbles.

Nikky,

Chicken or the egg argument. It's "wobbling" (oscillating) because it's unstable and your SAS is trying to correct it. This leads to bigger and bigger deviations until it finally disassembles.

If you want a working booster, I suggest trying my advice. Spaceplane mounted as far down the stack as you can get it and fins in the back of your boosters instead of the front. You'll see the entire problem disappear.

Best,

-Slashy

Edited May 31, 2015 by GoSlash27

[GoSlash27]

NikkyD,

Observe...

Scale model of your launch vehicle.

It wants to fly anywhere but straight.

But if you build it like I say...

It flies just fine.

Draggy stuff needs to be in the back.

Best,

-Slashy

[MadChris48]

I submit to you the Kaddy Shuttle. 3 stages, 4 kerbal capacity (with options for ship customization), takes a shuttle with 2.9k dV to ~80km orbit.

There were a few challenges to building this ship, but the biggest in my opinion is balancing the weight with some clever fuel flow as the craft uses it up. I have it rigged so the bottom orange tank drains first, then to top. This keeps the weight in the front of the ship the entire flight and helps counteract the offset thrust from the skipper.

Full throttle off the pad. Launch is the new standard, turn a few degrees right of the pad and it almost flies itself to space. Usually just minimal input is needed to keep it on course. The SRBs stage ~8km. From there its a gentle turn and climb to space.

It gets a little unstable as the last of the fuel drains out of the orange tank and it isn't heavy enough to help keep the nose down. The last ~500 units of fuel in the orange tank the ship wants to pitch up. I put a vernor to help out that last bit, but its the only time you need it (along with some light throttling).

2.9k dV is enough to get to minmus, mun, or anywhere else in Kerbin's SOI and return. I've rescued multiple kerbals in one go with this ship.

Re-entry is super easy. This thing has so much surface area you can come in a little 'belly up' and it slows down quickly. She glides to a gentle touchdown every time. I'm rather proud of her balance.

The shuttle was built in the SPH then imported to VAB.

To get the thrust right, the Skipper has been rotated 1 Shift-click notch on the rotation gizmo.

To get the fuel flow right, it has a fuel line from the top tank to the shuttle, and from the bottom of the shuttle directly to the Skipper.

You can even replace a Mk2 fuel tank with a Mk2 cargo bay and it can carry a small payload to space. I've found I can play around with the number of cockpits and cargo bays with some decent variation of ships and equally similar/easy launches.

I even have a mini shuttle version using FL-T800 tanks with a Swivel as the core stage.

It is possible and I hope this inspires you! Its super rewarding to build a shuttle-like craft. Enjoy!

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Edited May 31, 2015 by MadChris48

[GoSlash27]

I have no idea how to get vertical launch Space planes/Shuttles to work. I'm talking about vertical launch stages ( Huge rockets with boosters) and a space plane/Shuttle attached to the side of it. Like IRL Shuttles. I have tried making them before and have centered center of mass and everything but they always fail to launch properly, often just leaning to the side the plane is located on. Teach me how to create proper vertical launch ~3 stage crafts, stage ONE being solid booster ejection Stage TWO being Liquid fuel rocket ejection and stage THREE being the spaceplane/shuttle.

Connocclar,

Actually, they are built backwards from the staging.

First item of business is to build the spaceplane itself. You need to get it all balanced out so it'll fly okay.

Then you attach the tank, check the CoM location both full and empty, and point the main engine(s) so it's aimed at the center of that line.

Then you attach the SRBs. They need to be aligned with the CoM when the tank is full, which is toward the shuttle's side of the tank's CoM.

This should get you in the ballpark.

After that, it's a lot of trial-and-error tweaking, rebalancing, etc.

Good luck!

-Slashy

[MadChris48]

Connocclar,

Actually, they are built backwards from the staging.

First item of business is to build the spaceplane itself. You need to get it all balanced out so it'll fly okay.

Then you attach the tank, check the CoM location both full and empty, and point the main engine(s) so it's aimed at the center of that line.

Then you attach the SRBs. They need to be aligned with the CoM when the tank is full, which is toward the shuttle's side of the tank's CoM.

This should get you in the ballpark.

After that, it's a lot of trial-and-error tweaking, rebalancing, etc.

Good luck!

-Slashy

This. So this.

[JoCRaM]

My problem is NOT the gravity pull but that my huge wings create so much "lift" sideways the second they are 0.1° off 90° that the whole thing flips. Reducing the wings is not an option as they are supposed to be like that. See image above

You fix that by putting even more lift at the bottom of the orange tanks.

[NikkyD]

You fix that by putting even more lift at the bottom of the orange tanks.

I'm pretty sure this will cause rapid disassembly

[Ferdoni]

Much easier than reading all this, just search youtube for a good tutorial on this. You will understand the matter much quicker

[JoCRaM]

works fine for me, unlike steam cloud