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TL;DR: is this generally considered a "don't do this" type of thing for spaceplanes, or just a tradeoff? Hi, I've been refining a Mk3 "do-everything" spaceplane for a while now (all science, ISRU, amphibious, etc.) and I'm wondering if I'm making a mistake with the balance. The default CoM is very stable and just a tiny tiny bit forward of the CoL, but I understand that although these being very close makes the plane more maneuverable, it also makes it more vulnerable to loss of control. My question is: is this generally considered a "don't do this" type of thing for spaceplanes, or just a tradeoff? —Liftoff/landing: CoM and CoL being on top of each other is good here, right? —Ascent: CoM being somewhat ahead of CoL makes the plane more stable. But if it seems pretty controllable then is there a reason to worry? —Reentry: CoM being somewhat ahead of CoL makes the plane recover from aggressive reentry profiles. Is it reasonable to say "I expect to have some fuel left to create this condition for reentry" or is that considered a bad design? (It needs 10% fuel to ensure recovery from radial out position) Basically, I like the idea of maximum agility (for a Mk3 spaceplane) but I don't want to overlook a fatal flaw.

Hi, i think this would be an invaluable tool for all of us, if we could see real time inflight CoM and CoL, is it possible?

Well, after hours of testing, reading, and testing again, I am still having a really hard time understanding the aerodynamics. Previous post: Even though my previous post was ironically the only ground drag issue that came into the equation with trying to make a stable jet, I'm still trying to build a stable jet. Rather, understanding how to make one that is. I know CoM, CoT, and CoL, but I don't understand their results. There are numerous claims that if the CoL is behind the CoM, then the rocket will be stable. KSP wiki: http://wiki.kerbalspaceprogram.com/wiki/Center_of_lift#Flight_characteristics foamyesque: But my mind is vehemently refusing to accept this. Don't you guys mean the "center of drag"? I feel like this is very similar to the CoL, but is still different. You could have a ship with two wings in the front and then a bunch of random parts on the back, and would fly with the drag-inducing parts in the back like an arrow with feathers. Yet, the CoL would be right between the two wings, because they are the only things providing lift. I've had planes where the CoL is significantly behind the CoM, but it still wants to flip at high speeds, or at least doesn't want to just go straight. And this flows into my second question. You know, let's make a list. Welcome to the buffet of questions for all your answering needs: Is the CoL the same thing as the "Center of Drag"? If not, is there a good way to find how far the CoD (center of drag) is behind the CoM? I've been shooting my crafts way up in the atmosphere and then letting them fall to see if the CoD is behind the CoM. Kinda time-consuming. If all parts create lift (KSP wiki quote below), why don't they change the CoL in-game? KSP wiki: http://wiki.kerbalspaceprogram.com/wiki/Lift#Dynamics The wings are symmetrical. Do they still produce vertical lift in ksp if they are not given any angle of attack? Are there specific wings that do/don't produce vertical lift at 0° angle of attack? I'm really sorry I'm asking the same question that everyone always asks, but this is a little different. Thank you so much for taking the time - Spemble

OK, so a picture is worth a thousand words: Obviously, the center of mass for this craft is...a little off from the center of thrust, and at anything better than nominal thrust it starts spinning like a top. It -started- with a lot of RCS fuel, but it's mostly empty now and there isn't much by way of SAS on it....all things to add on my next design. Now, it's held together with 3 Advanced Grabbing Units, but I can only seem to get one of them to flex properly. In theory that's probably enough to move the CoM over the center of thrust but it would be a lot easier if I could get the other two joints to pivot. Is there some trick I'm missing? I've switched to other craft, reloaded the save and the game, changed control spots. I haven't tried decoupling the craft and recoupling (simply because it was so very painfully slow the first time to couple them). The simple way to test if the klaw pivot is working is to toggle torque off for half the craft, free that pivot, and then perform maneuvers. The expected result is that the parts with no SAS enabled should flop around almost at random.

I'm designing an Eve launcher but I'm having problems while testing it on Kerbin. I'm using asparagus staging, with 3 booster groups. 2 with aerospikes and the last one with "LV-909 "Terrier" Liquid Fuel Engine". But when the half of the first tank gets consumed, the rocket always flips. I don't know what I'm doing wrong, since the COM is always below de middle. Here are some pics that hopefully will help you to understand the problem, as you can see I have tried with diferend pods to make sure it was not a drag problem: http://imgur.com/a/opUs4 Thank you very much, I need to rescue some Kerbals!

A simple debug feature (much like how f12 shows drag/lift) that would display the CoL, CoM, and CoT while in flight. This would help with spaceplanes because you could adjust fuel levels to balance it out or watch how it moves in flight.

Something I've never really accomplished is building a reliable shuttle, so I set out to do just that. I've already done some test flights, but it's far from stable. The issues stem from the orbiter's aerodynamics which I can't figure out. The vehicle is completely stock except for the docking assembly in the forward bay, but here is the craft file with the assembly removed (it brings the CoM just in front of the aft docking port): https://www.dropbox.com/s/xyv532298gm371q/Shuttle%20Orbiter.craft?dl=0. I can't figure out why the centre of mass is so far back and why the centre of lift is upside down. I've double checked to make sure the wings are the right way up. The centre of thrust shown here is with the main engines disabled. In-orbit stability is another issue considering the two OMS engines aren't perfectly aligned unless I tilt them up to an awkward angle. Also, sometimes the CoL will act up and just appear as a dot in the middle of the tail without a vector:

To get the COM to display I have to click the COM icon three times then it appears like it was just having a kip. Any ideas what might be causing it?

Hi all! I've been creating rover designs recently. I have made a few, but my main problem is the lack of ability to go up steep inclines. Any tips? Thanks in advance! -Barrrrry