Center Of Mass widget

[KSK]

3 hours ago, Hotel26 said:

To hypothetically "move" the CoM of a stock part (and remain honest), you'd have to add (massively) to its base mass, wouldn't you?

 

Not as I understand it - you could redistribute that base mass instead. That’s why I’m suggesting that only certain parts be CoM tweakable.

For most parts, I think the current CoMs are either good enough or it’s difficult to see a real world justification for allowing them to be tweakable. Fuel tanks would be a good example, since to a decent approximation they’re just homogenous tubes and there’s not much you can do to shift their CoM, short of draining them - which the game already takes into account.

A crew capsule though is definitely not homogenous. They contain all kinds of internal structures and sub-systems which, in real life, can be moved around to give a desired centre of mass. If I recall correctly, the Apollo capsule is a good real-world example - it was designed with an offset CoM to provide additional control during reentry. 

KSP doesn’t model internal part structure in fine detail so we can’t, for example, change the CoM of a Mk1 capsule by moving the pilot couch. However a CoM widget would provide a reasonable simulation of that ability.

You could think of it as a way of modding parts on the fly to better work with a particular craft. A Hitchhiker module used as part of a space station would be fine with a central CoM. When used as part of a rover though, I don’t think it’s unreasonable or unrealistic to shift things around inside it (or to simulate that shifting) to lower its CoM to provide a bit of extra stability.

I would see that as sensible engineering rather than an easy-mode option.

[Loskene]

As someone who spends more time making tiny tweaks to aircraft to shift the CoM/L over to "aerodynamically stable" from "turns into a pretzel on takeoff" than actually designing or flying the planes, it's a constant pain in my neck I can't just *slightly* tweak the CoM in some parts to get the desired result instead, as I would easily be able to do were I designing a real aircraft. To me, that KSP doesn't simulate rearranging internal components (or just throwing out the passenger seat) to tweak the CoM of the overall craft is more of an oversight than a "would be nice to have" feature. It should at least be applicable to crew capsules, as this was a very important detail in the re-entry profiles of early spacecraft like the aforementioned Apollo command module. The offset centre of mass allowed them to "fly" the capsule during re-entry to adjust their approach and limit G-forces imparted on the crew by rolling the craft, something that we cannot simulate in KSP without mods or clipping ballast inside them, which are 2 things not every player is comfortable with and come with issues of their own.

So yeah, +1 from someone who makes planes with FAR, where precision placement of your CoM on the order of centimetres can be the difference between smooth sailing and a RUD at the sound barrier.

Edit: Consider this. If being able to move around the CoM of individual parts within a certain range is considered too finicky or "cheaty" for some, then perhaps there's a simpler solution that nearly already exists. One (or probably more) of the Apollo capsules I saw as mods for realism overhaul had a toggle switch option in flight called "Descent mode" or something along those lines. This would shift the capsule's centre of mass to one side a little in order to give it the aerodynamic properties I mentioned above. Very handy.

Now what if we implemented this descent mode option to all stock command pods and cockpits and let us configure, with 3 sliders for X, Y and Z, how much the CoM is displaced within a preset maximum range along those axes of the pod?

This would pretty much solve all the problems I mentioned above. We'd have a stock method of doing lifting-body re-entry manoeuvres with the basic pods without a mass or launch stability penalty for ballast, and I'd still be able to fine tune the CoM on my planes without rearranging all the wings one millimetre at a time.

Think about it, whoever's responsible for these kind of things, I'd appreciate it as a QoL.

Edit 2: Yeah this would be real handy right about now 

 

Edited December 29, 2018 by Loskene
ideas were had

[Gargamel]

18 hours ago, KSK said:

Kindly don't fix my posts. Especially when you're ignoring my argument and inserting one of your own. 

That's kind of the point of a FYP.  But apologies. 

12 hours ago, KSK said:

That’s why I’m suggesting that only certain parts be CoM tweakable.

I agree with this in principle, that certain modules are realistically tweakable... but.....   the ones that would be able to do so, don't have enough movable mass parts to really make a difference.   We could move some couches, or redesign the air scrubbers within the capsule, but that's a tiny percentage compared to the mass of the rest of the vehicle.   In KSP, it really won't make that big of a difference, if the tool is kept realistic. 

[Hotel26]

My simple take on this suggestion/request is that it is much more suitable for implementation as a mod to KSP.

[Assuming that is feasible.  If not, consider designing some add-on parts specifically for rovers like more massive base plates...]

Edited December 29, 2018 by Hotel26

[KSK]

6 hours ago, Gargamel said:

That's kind of the point of a FYP.  But apologies. 

I agree with this in principle, that certain modules are realistically tweakable... but.....   the ones that would be able to do so, don't have enough movable mass parts to really make a difference.   We could move some couches, or redesign the air scrubbers within the capsule, but that's a tiny percentage compared to the mass of the rest of the vehicle.   In KSP, it really won't make that big of a difference, if the tool is kept realistic. 

Apology accepted.  

And yeah, that was pretty much my thinking. Tweakable CoM as an assist or a fine-tuning tool rather than a magic ‘fix everything’ button. Tweaking the capsule CoM on even a modestly sized rocket would make a negligible difference, tweaking the crew cabin on a rover will help its stability but wouldn’t stop a really bad design from flipping over at speed.

Or to use a personal example, my first Mun lander (Mk1 pod, FL-T800 tank, engine and legs) is going to fall over on a slope no matter where that capsule CoM is! 

I’m thinking you could exaggerate the CoM tweak a bit for aircraft parts because KSP aircraft parts are very oddly designed compared to their real-world counterparts (fuselage sections as strictly passenger or fuel carrying for example). A better solution might be to allow limited CoM shifting on complete aircraft but I can see that being a complete bear to implement or balance.

6 hours ago, Hotel26 said:

My simple take on this suggestion/request is that it is much more suitable for implementation as a mod to KSP.

With respect, I think it would work quite nicely as an advanced tweakable in stock. Not something a new player will see by default but there to be found (or ignored) as they like.

No need to relegate everything to mods, especially when it (tweakable CoM) would already work quite intuitively with the stock widgets and CoM indicator.

Edited December 29, 2018 by KSK

[Loskene]

6 hours ago, KSK said:

With respect, I think it would work quite nicely as an advanced tweakable in stock. Not something a new player will see by default but there to be found (or ignored) as they like.

No need to relegate everything to mods, especially when it (tweakable CoM) would already work quite intuitively with the stock widgets and CoM indicator.

I also think it would be best as an advanced tweakables option. It's not meant to give you a broad range of freedom over your CoM placement, it's just for fine tuning it when you already have the arrangement basically how you want it. ie your plane must already be able to fly before you tweak the CoM, this is just to make it fly exactly how you want it to. For these purposes just simulating rearranging the seats in the crew cabin is more than sufficient.

Also, it already exists as a mod, as I mentioned earlier.

Edited December 29, 2018 by Loskene
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[GluttonyReaper]

On 12/26/2018 at 2:55 AM, Gargamel said:

Take a look this poorly designed rover:

Sharing this because I think it's neat, even if not super relevant to this thread, but those buses are a heck of a lot more stable than people think they are:

Quotes are being funky atm, but I would like something like @KSK's suggestion to be implemented - the weight shift equivalent of putting all the snacks in the lower cabinets of the Hitchhiker. Enough to useful for making rovers a bit more stable and tiny last-minute adjustments, not so much an EZ-fix solution for all COM problems.

Additional thoughts: maybe small COM changes could be done on capsules even during flight - I seem to recall something about Apollo astronauts packing their cargo before re-entry in a certain way to affect COM?

I was about to suggest being able to change the COM of fuel tanks at the cost of reducing fuel capicity - idea being that you take up some of the space with ballast. But then I realized that dedicated ballast parts would be more useful.