Shuttle spin

[Engineer Gaming]

I've been making a NASA space shuttle style rocket but whenever i detatch the boosters (a different question, is there a way to pump more fuel into the SRBs or are they limited?) the shuttle and the fuel tank will start spinning even tho its covered in RCSs (they are working) and full of reaction wheels but they still keep spinning when i activate the engines on the shuttle. IDK if its because of balancing but its really annoying

[Scarecrow71]

You have part of the answer on your post.  Balance and center of mass on the shuttle post-staging can cause the craft to spin as it tries to get level.  Another part is center of lift, coupled with where in the atmosphere you are when staging happens.  Simply put, too much atmosphere causes way too much drag, while too little doesn't cause enough (or any) for the craft you are flying.

[Snark]

21 hours ago, Engineer Gaming said:

is there a way to pump more fuel into the SRBs or are they limited?

There is not.  SRBs are solid fuel, which can't be pumped.  Their two main limitations:

• once activated, they can't be turned off or throttled down
• no fuel transfers

21 hours ago, Engineer Gaming said:

IDK if its because of balancing

It's because of balancing.  Almost certainly the reason you're having these problems is that you've designed your shuttle in a way that is aerodynamically unstable.  Your CoM (center of mass) is too far to the back of the craft.

It's basically impossible to "fix" aerodynamically unstable craft with RCS thrusters or reaction wheels, so don't bother even trying:  the aero forces due to the instability are orders of magnitude stronger than RCS and reaction wheels, so they're pretty much useless for this purpose.

In general, almost certainly what you need to do to fix this is to move your center of mass forward.  It would be easier to offer specific advice if you could post a screenshot of your craft-- ideally, one that shows the CoM without the SRBs attached.  (For example, in the VAB, temporarily take the SRBs off, and then turn on the CoM display via the button in the bottom left corner.  That would help to answer the question of what's going on.

It's worth noting that very probably the reason your craft is unstable and won't fly right-- i.e., the reason the CoM is too far in the rear-- is precisely because you tried to build a craft that looks like the US space shuttle.  This is a well-known issue that a lot of players have gotten bitten by before you.    The problem is this:

• On the one hand, KSP makes it really easy to build a craft that looks just like the US space shuttle.  Mk3 cockpit, Mk3 fuselage parts, Big-S delta wings, Big-S tail fin, Mk3 engine plate, Vector engines.
• On the other hand, if you build one out of those parts... it tends to be horrifically unstable.  This is because, first, the CoM ends up way in the back, because that's where the heavy engines are, and, second, all the control surfaces are right back there too, which makes them useless because they have no lever arm to work with.

What it boils down to is, you can build a craft that either looks like the US space shuttle, or can actually fly.  It's very difficult to do both.  If you could post a screenshot, though, we might be able to offer some concrete suggestions about how you might be able to improve your flight characteristics.

[Coyote Foxtrot]

On 2/1/2023 at 8:38 PM, Engineer Gaming said:

a different question, is there a way to pump more fuel into the SRBs or are they limited?

Not a way to pump, but you can modify the craft file to give SRBs more fuel by modifying the SRBs' module "amount = #" and "maxamount = #" values.

[Engineer Gaming]

On 2/3/2023 at 3:28 AM, Snark said:

There is not.  SRBs are solid fuel, which can't be pumped.  Their two main limitations:

• once activated, they can't be turned off or throttled down
• no fuel transfers

It's because of balancing.  Almost certainly the reason you're having these problems is that you've designed your shuttle in a way that is aerodynamically unstable.  Your CoM (center of mass) is too far to the back of the craft.

It's basically impossible to "fix" aerodynamically unstable craft with RCS thrusters or reaction wheels, so don't bother even trying:  the aero forces due to the instability are orders of magnitude stronger than RCS and reaction wheels, so they're pretty much useless for this purpose.

In general, almost certainly what you need to do to fix this is to move your center of mass forward.  It would be easier to offer specific advice if you could post a screenshot of your craft-- ideally, one that shows the CoM without the SRBs attached.  (For example, in the VAB, temporarily take the SRBs off, and then turn on the CoM display via the button in the bottom left corner.  That would help to answer the question of what's going on.

It's worth noting that very probably the reason your craft is unstable and won't fly right-- i.e., the reason the CoM is too far in the rear-- is precisely because you tried to build a craft that looks like the US space shuttle.  This is a well-known issue that a lot of players have gotten bitten by before you.    The problem is this:

• On the one hand, KSP makes it really easy to build a craft that looks just like the US space shuttle.  Mk3 cockpit, Mk3 fuselage parts, Big-S delta wings, Big-S tail fin, Mk3 engine plate, Vector engines.
• On the other hand, if you build one out of those parts... it tends to be horrifically unstable.  This is because, first, the CoM ends up way in the back, because that's where the heavy engines are, and, second, all the control surfaces are right back there too, which makes them useless because they have no lever arm to work with.

What it boils down to is, you can build a craft that either looks like the US space shuttle, or can actually fly.  It's very difficult to do both.  If you could post a screenshot, though, we might be able to offer some concrete suggestions about how you might be able to improve your flight characteristics.

thanks for the advice, I think ill work on something else so thank for the offer to help but i think ill just try something else