My rocket always flies out of control.

[heck]

No matter how simple, or complex the design of the rocket is, it always flys out of control after I use the solid fuel rockets.

It's really starting to ♥♥♥♥♥♥♥ piss me off. I can't even get into orbit anymore. The new physics absolutely screwed me. I've watched videos, and done everything they said. Any help please?


http://images.akamai.steamusercontent.com/ugc/436073542218768681/9C3B01D001074059541AB6A022D8D97C51F5A650/

[Tetratrary]

if it's happening at 10,000 m then it's same problem for me. cant even make a 45 degree angle without horribly doing flips atleast 3 times

[Minion of Speed]

You need to put fins on near the bottom of the craft.

[heck]

Originally posted by anko:

if it's happening at 10,000 m then it's same problem for me. cant even make a 45 degree angle without horribly doing flips atleast 3 times

EXACTLY. No matter what, it feels like doing 15 cartwheels before it gets back into control.

[Bong_Science]

Keep in mind as you use up fuel, your center of mass is going to change and what may have been initially stable starts becoming unstable and can flip as you burn fuel.

Also, is that the "Reliant" or "Swivel" engine, for your liquid fuel engine?
I've found that without an SAS unit while using the "Reliant" variety, controlling a spacecraft is very sluggish at best, and has a nasty tendency to do what I previously described.

"Swivel" on the other hand, has a pretty nice gimbal range. You can generally get away with not using an SAS with these, but if you do happen to use one, it holds its position quite nicely.

[Shibe One]

Because it's not aerodynamic. Also don't try and just put it at a 45 degree angle. You need to do it gradually. If you see it beginning to slip, put it back at an angle where it's stable.

[jcekstro]

If you are going out of control anytime other than when you are staging than you are being too aggressive with your gravity turn. Make a slight turn to the 90 degree marker shortly after liftoff. From that point on make sure you so not get the nav ball outside of the prograde marker (I.e. the center dot of the ball needs to stay inside the yellow circle until you get at least above 20k m, some rockets need to be even higher before being able to be aggressive with the turn). If it is happening every time you stage, it is probably still too aggressive of a gravity turn coupled with too steep of a dropoff in TWR causing the nose to drop uncontrollably. As others have stated, fins do help, but it is very possible to do it without them, just have to be cautious with the turn. Also, I recommend the swivel engine now as others have stated.

[ghpstage]

The SRBs give inherent stability due to the large amount of drag they place at the bottom of the rocket, once they are gone the drag centre moves upwards a lot, possible near the fron end due to the draggy radial components (chutes, goo and legs(?)) you have up there. Once the centre of mass goes below the aerodynamic centre the rocket becomes unstable and will try to fly backward, requiring enough control authority to overcome the drag to styay forward.

Easiest things to do are add fins/control surfaces to the rear to increase drag and combat toque, or control surfaces and swivel engine (the LV-45 if your mot already using it) to provide control authority to overcome the instability, though an unstable craft is difficult to keep forward facing without SAS.

Also, what people said about not coming off the prograde marker before 20km or more is important.

[heck]

Originally posted by ghpstage:

The SRBs give inherent stability due to the large amount of drag they place at the bottom of the rocket, once they are gone the drag centre moves upwards a lot, possible near the fron end due to the draggy radial components (chutes, goo and legs(?)) you have up there. Once the centre of mass goes below the aerodynamic centre the rocket becomes unstable and will try to fly backward, requiring enough control authority to overcome the drag to styay forward.

Easiest things to do are add fins/control surfaces to the rear to increase drag and combat toque, or control surfaces and swivel engine (the LV-45 if your mot already using it) to provide control authority to overcome the instability, though an unstable craft is difficult to keep forward facing without SAS.

Also, what people said about not coming off the prograde marker before 20km or more is important.

So where should I put all of my science stuff like goo?

[jcekstro]

You still need to keep those up top or you won't be able to return them, just need to be cognizant that you will be very top heavy and need to be very careful with the gravity turn before you get to around 20k meters. Sometimes that will mean that you won't always have the most advantageous gravity turn you can, but its better to stay stable and get there using a little extra fuel than to tumble out of control trying to do it with the bear minimum.

[Hudgems the pouty pigeon]

You need to have resonably sized fins on bottom of you ship

[jhendriks87]

Basically keep the Center of mass high in your rocket, put fins on the bottom, and change your engine to the swivel type and you will have no issues at all.

[heck]

Originally posted by jhendriks87:

Basically keep the Center of mass high in your rocket, put fins on the bottom, and change your engine to the swivel type and you will have no issues at all.

I don't have the swivel engine unlocked yet. And wouldn't having the center of mass on top be bad? Wouldn't it cause it to flip?

[Tothmetres]

give it little taps on the keyboard, don't try to jerk it suddenly

[Woody]

Originally posted by UndyingWar:

Originally posted by jhendriks87:

Basically keep the Center of mass high in your rocket, put fins on the bottom, and change your engine to the swivel type and you will have no issues at all.

I don't have the swivel engine unlocked yet. And wouldn't having the center of mass on top be bad? Wouldn't it cause it to flip?

Think about darts or arrows and where most of the weight is. Seems a bit counter intutive that if you have a rocket flipping the solution is not moving the COM down.

The main use of fins in most rocket designs is to create drag towards the bottom of the rocket to balance the drag being generated at the top.

The problem with the COM shifting in flight is exasperated by only having the smaller tanks available. With the larger tanks the shift is not as drastic. When you advance in the tech tree the need for fins will decrease because of gimballed rockets, SAS, and you tend to make longer rockets. Again think of arrows, they are not made short and stubby for a reason.

Edit: Forgot to add watch your speed. The faster you go the more drag at the top.

[jhendriks87]

Originally posted by UndyingWar:

Originally posted by jhendriks87:

Basically keep the Center of mass high in your rocket, put fins on the bottom, and change your engine to the swivel type and you will have no issues at all.

I don't have the swivel engine unlocked yet. And wouldn't having the center of mass on top be bad? Wouldn't it cause it to flip?

Center of mass near the top, coupled with fins donw the bottom, will keep your rocket facing properly. Think of the COM as a pivot pooint which the rocket turns around, if you have that point near the top it is much harder to spin the rocket. Pick up a pen between your fingers and hold it near the bottom and try to tip it over, should tip very easily, now move your fingers near the top and try the same thing, should be almost impossible to tip over.