Stage separation problem - spacecraft jettisoned instead of 1st stage

[uncle_jew]

Hello,

I am trying my first steps with the KSP demo, and I sometimes get a strange stage separation problem. When I jettison the first stage during launch, the 2nd stage doesn't ignite and can no longer be controlled and the view remains centered on the first stage until it crashes. If I try controlling RCS jets, RCS jets on the first (jettisoned) stage fire. It is as if the program considers the first stage to be the "main spacecraft" instead of the 2nd one (which has the capsule attached).

The Engineer's Report contains a warning "Engines jettisoned before use" about 2nd stage engines, which confirms that the program thinks I am jettisoning the 2nd stage and keeping the 1st one, and not vice versa.

Is this a known problem, and is there a solution? When a stack decoupler separates the spacecraft into 2 parts, how does KSP decide which one of these parts remains under my control?

Thanks!

[Vanamonde]

Could you post a screenshot of your ship, with the staging display visible?

[soulsource]

I guess this might be caused by having the root part of the whole craft in the first stage. I don't know about the demo, but in the full version there's a gizmo (I think they are called like this...) in the upper left corner of the editor that lets you edit the root part (next to the placement, offset, and rotation gizmos).

My rule of thumb when building craft is to always start with the probe core/capsule of the last stage/payload. This way the root part will always be on the payload.

Anyhow, if after separating parts the game chooses the wrong part as active, you should be able to switch with the ALT+[ combination (on Windows - on Linux use Right Shift+[ instead).

Edit: What's also strange is that you are able to control the RCS of a detached stage. If a stage doesn't have any capsule or probe core, it should be completely uncontrollable.

[The_Rocketeer]

Hello,

I am trying my first steps with the KSP demo, and I sometimes get a strange stage separation problem. When I jettison the first stage during launch, the 2nd stage doesn't ignite and can no longer be controlled and the view remains centered on the first stage until it crashes. If I try controlling RCS jets, RCS jets on the first (jettisoned) stage fire. It is as if the program considers the first stage to be the "main spacecraft" instead of the 2nd one (which has the capsule attached).

The Engineer's Report contains a warning "Engines jettisoned before use" about 2nd stage engines, which confirms that the program thinks I am jettisoning the 2nd stage and keeping the 1st one, and not vice versa.

Is this a known problem, and is there a solution? When a stack decoupler separates the spacecraft into 2 parts, how does KSP decide which one of these parts remains under my control?

Thanks!

Welcome to the forums!

What soulsource said about starting with the pod/probe core is good advice. Build the rocket from the top down, not the bottom up.

I don't know if the demo is different, but in the main game you can switch crafts with "[" or "]" so I don't think u need to use shift, in Windows anyway.

Also, stack separators are one-sided - they have a red arrowhead on them that indicates which side they stay attached to, so make sure the fat end of the arrow is on the side of the stage you're discarding.

Good luck, and keep asking for help - learning to KSP can be tough, but this community is generally very friendly and helpful!

[AlextheBodacious]

3 options:

1. You need to fire that engineer, he's been wrong about this whole mission.

2. One of the decouplers is before the engine, drag it to the top.

3. Your root part is off, use the root tool in the VAB by pressing 4.

[uncle_jew]

You are absolutely right, I built the rocket from the bottom to the top!

Here is the rocket (built from the bottom to the top) that had the error message and the inflight problem I described earlier.

Here is a simplified rocket (built from the bottom to the top) that exhibits the same error message (although it magically gets sorted out in flight and works properly). Apart from "engine jettisoned before use", it also complains about the decoupler being attached wrong, although it is correctly attached.

How do you set the root part? If I click on the "Root" icon, it doesn't say "select the new root part". It says "select a set of two or more parts to attach" I clicked on the command pod (using the simplified rocket posted above), it demanded a second part to click on. I clicked on the fuel tank directly beneath the command pod. This seems to have solved the error message. If instead, I click on the command pod, then on the bottom engine, the problem persists. So what does the 2nd part I am supposed to click mean?

Back to the "full" rocket, clicking on the "Root" icon, then on the command pod, then on the decoupler directly beneath it seems to have solved the problem. KSP now complains about the "command module facing the wrong way", but it seems to work properly nonetheless.

Thanks!

[federicoaa]

Remember to build from top to bottom. First thing you add in a vessel is the pod, then the rest.

[The_Rocketeer]

How do you set the root part?

Click the root tool.

Click on the rocket.

Click on the pod/probe core.

Done!

Back to the "full" rocket, clicking on the "Root" icon, then on the command pod, then on the decoupler directly beneath it seems to have solved the problem. KSP now complains about the "command module facing the wrong way", but it seems to work properly nonetheless.

Thanks!

Yes, but you've set the decoupler/separator as the root part rather than the command pod. This is nearly right, and will solve the problem, but it's still not the same as if you'd build from the pod down.

Lastly, if you have a question again it's best to ask in the 'Questions and Tutorials' subforum