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I'm using a modded ksp and I've just started having a problem. This happened without installing any new mods, although who knows what patches Module Manager picked up.

The size, cost, and projected ISP of my rockets remain as before. But the actual performance I'm getting has shrunk drastically. For example 2000 delta V used to easily get me out of the Kerbin atmosphere. Now it gets me to less than 18 km, straight up. (yes I'm measuring ISP in atmosphere not in vacuum.)

What mod is likely to be doing this and how can I fix it?

Edit: So far this doesn't happen with all parts. It definitely happens with larger Space Y parts.

Edit: it happens with some, but not all, upsized stock parts too

Edit: I'm definitely getting much less than the calculated TWR.This is independent of atmosphere.

Edit: at 1.4 calculated TWR I'm geting an actual 1 TWR

I'm using a modded ksp and I've just started having a problem. This happened without installing any new mods, although who knows what patches Module Manager picked up. The size, cost, and projected ISP of my rockets remain as before. But the actual performance I'm getting has shrunk drastically. For example 2000 delta V used to easily get me out of the Kerbin atmosphere. Now it gets me to less than 18 km, straight up. (yes I'm measuring ISP in atmosphere not in vacuum.) What mod is likely to be doing this and how can I fix it? Edit: So far this doesn't happen with all parts. It definitely happens with larger Space Y parts. Edit: it happens with some, but not all, upsized stock parts too Edit: I'm definitely getting much less than the calculated TWR.~~This is independent of atmosphere.~~ Edit: at 1.4 calculated TWR I'm geting an actual 1 TWR

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[–] • 4 pts (edited )

Press alt f12 to bring up debug menu Go to physics -> aero (I think) either here or in one of the other items under physics you can turn on show aerodynamic info in context menus.

Then right click and check parts for high drag numbers in flight.

This was happening to me due to drag being calculated on parts that were in a cargo bay. I reassembled everything and made sure nothing was clipping through the bay and it solved it.

Also. Use kerbal engineer mod for isp calculations.

I love this game and have spent far too much time on it.