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TurboBilder

Space Shuttle Help

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Dear KSP community,

I have been having some troubles lately with my space shuttle. When I launch the shuttle it just begins to roll to the  side and pitch back. I cant really figure out what the problem is here o i came for help.

Thanks!

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@TurboBilder

How do you expect help with such scarcedy of information. You are conversing over the internet. We are not mechanics at the place where things actually happen. You have to supply the details of the problem as far as you can describe so we have some information to go about.

In your case the cause could be kinda broad, I would make a screenshot (F1) of your spaceshuttle in the editor (VAB or SPH) Before making the screenshot have CoM, CoT and CoL activated. These are the Center of mass, center of thrust and center of lift markers in the lower left side of the editor screen (yellow, purplse and blue markers)

Screenshots are found in the screenshot folder in your main KSP directory (wherever it is installed)

You can upload them to imgur.com.
 

Edited by Aeroboi

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If you can post a picture, that would help to diagnose the issue.  But in general, space shuttles in this game are really, really hard.  The main reason is the center of thrust does not go through the center of mass.  I.e.. you've got a heavy external tank sitting out to the side, which makes the craft want to tip in that direction.  To deal with this, as with the real-life space shuttle, the engines have to angle so that they point through the center of mass.  But making things worse, the center of mass changes as the SRBs burn out and the external tank loses fuel and gets lighter.  I'm not aware of any easy fix to this issue; it just takes a lot of very careful tweaking part placement and the like.

Another problem is that the space shuttle analog parts are not balanced correctly, so it's very hard to make a 1-for-one copy.  The Kickbacks are way too weak compared to the shuttle SRBS, and the Vector engines are way too powerful compared to the SSMEs.  But Vectors are quite helpful due to their very wide gimbal range, so a common solution is to use less than 3.

The issue about rolling to the side is a bit more of a mystery -- if all the parts are symmetrical that theoretically should not happen.  It could just be a result of your control surfaces and engines trying to deal with the unbalanced torque, or you could have some actual asymmetry.

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Hi! Please post photos of your design so we can see what might be the issue.

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The biggest "trick" for shuttles is to point the thrust through the CoM to prevent uncontrollable pitch during launch. I've used this picture recently during a discussion about the roll program of a shuttle but it may help you as well:

fhcavIz.png

Most important is the CoM and the direction of the thrust vector (extended with the orange line). As you can see, the vector points directly on the CoM which has two effects:

1) Your shuttle will not pitch uncontrollable during launch

2) Your shuttle will not ascent in a straight line but along the thrust vector. This is important to know, otherwise you may crash into the launch clamps ;)

Keep in mind, that the CoM will shift during the launch (roughly displayed by the orange and red bubble) so at some point, you may have to start to pitch slightly to reduce the effect.

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