Center Of Mass widget

[Daveroski]

If I were a designer.. (and I am. )

I would design vehicles while keeping the COM in mind in their development.

What I'm proposing is another widget. Now I know we already have widgets for Rotating and Repositioning an item.

What I would like to see is a widget that will allow me to adjust the COM in any item I use for building.

As though each item currently has a weight or lump of mass already in its design only now we get to move it. Within reason of course but I would like to be able to go so far as to be able to move the COM on a rover below the wheels.

There is precedent for the COM being outside the object. Indeed this is often used to offset the COM in various builds. Usually rovers.

Suppose I have built a vehicle. I click the COM display button and see the ball showing the COM of the vehicle. Then I click the COM widget and have the option to move it in much the same way a moving an object works now.

I just feel that my Rovers, Bases Lander and even Space Planes would be much more stable if this were a facet of the game.
I also feel that I would be even more inclined to build Rovers and Bases if such extra stability were available.

 

Edited December 25, 2018 by Daveroski

[Rocket In My Pocket]

Jet engines.

There COM is well ahead of the actual model to account for interior plumbing and such.

Point them at the sky and sink them into your craft, will push COM down, even below the vehicle or ground.

Edited December 25, 2018 by Rocket In My Pocket

[Daveroski]

2 hours ago, Rocket In My Pocket said:

Jet engines.

There COM is well ahead of the actual model to account for interior plumbing and such.

Point them at the sky and sink them into your craft, will push COM down, even below the vehicle or ground.

 

3 hours ago, Daveroski said:

There is precedent for the COM being outside the object. Indeed this is often used to offset the COM in various builds. Usually rovers. 

 

[Rocket In My Pocket]

So...why do you need a widget then? (Also, why mention a precedent but not specify?)

It's already possible to do in the game, as you apparently know. Works great even!

Allowing you to move the COM for no additional cost/weight/complexity would just be "cheaty." It would be better to have a new "weighted block" part that functioned similarly to the Jet Engine trick.

Edited December 25, 2018 by Rocket In My Pocket

[qzgy]

1 minute ago, Rocket In My Pocket said:

It would be better to have a new "weighted block" part that functioned similarly to the Jet Engine trick. 

Basically ballast?

I agree, a mechanism like in the OP is a bit too cheaty.

[Rocket In My Pocket]

1 minute ago, qzgy said:

Basically ballast?

I agree, a mechanism like in the OP is a bit too cheaty.

Yeah, but not just heavy; heavy off center.

Then you just rotate it the way you want it's mass offset.

Exactly like Jet Engines are now basically, but with a nice purpose built block so it feels less like an exploit.

Edited December 25, 2018 by Rocket In My Pocket

[qzgy]

14 minutes ago, Rocket In My Pocket said:

Yeah, but not just heavy; heavy off center.

Then you just rotate it the way you want it's mass offset.

Exactly like Jet Engines are now basically, but with a nice purpose built block so it feels less like an exploit.

Ok. I still feel as if thats not quite physically accurate (adding a lump of metal would just add more mass there not two feet to the left) but I guess KSP sometimes bends physical laws anyways.....

[Rocket In My Pocket]

17 minutes ago, qzgy said:

Ok. I still feel as if thats not quite physically accurate (adding a lump of metal would just add more mass there not two feet to the left) but I guess KSP sometimes bends physical laws anyways.....

Not if you make one half of it out of a less dense material. Ie. A half plastic/half metal cube would have most of it's weight concentrated on the metal side, and thus would have an off center COM.

A rectangle would obviously be better, but would be more awkward to use.

It would still be a bit of a stretch for this to move the vehicles COM significantly, but hey like you said; it's KSP.

Edited December 25, 2018 by Rocket In My Pocket

[HebaruSan]

When a game presents you with a challenge that exists for a reason, why not try to solve it with the tools available rather than simply wishing it away?

There's no shortage of other games with unrealistic vehicle physics.

[Daveroski]

1 minute ago, HebaruSan said:

When a game presents you with a challenge that exists for a reason, why not try to solve it with the tools available rather than simply wishing it away?

There's no shortage of other games with unrealistic vehicle physics.

 

Wow you are really rude.

 

 

 

 

[HebaruSan]

7 minutes ago, Daveroski said:

Wow you are really rude.

I don't see how, but you have no answer to my question?

To elaborate, when you build a rover and it tips over, that's the game showing you that designing a wheeled vehicle has challenges. Challenges grounded in physics, that can even vary from environment to environment, and there are all sorts of strategies available for handling them. It's a feature, not a bug. Real life vehicle designers have to move the center of mass the old fashioned way, by moving actual massive parts downwards. You're meant to do the same in KSP. When you crash a rover and update it (whether it's CoM or wheel base width or steering or whatever) and it drives better, that's the core KSP gameplay loop working well.

But rovers aren't the biggest reason why this idea should not be implemented. Consider the effect on planes and rockets. Instead of learning to design a plane with a CoM and CoL properly aligned, the player can simply drag the CoM around and magic any design into flightworthiness. Instead of learning to construct rockets with the heavy bits in front and the draggy parts at back, again you can simply drag the CoM to the top and be done with it. Significant portions of the gameplay are deleted.

I like to use Super Mario Bros. as an analogy in gameplay discussions, because I'm old. This suggestion sounds to me like saying that Mario should have an auto-punch option so instead of the monsters killing you when you run into them, you would kill them.

[Daveroski]

1 hour ago, qzgy said:

Basically ballast?

I agree, a mechanism like in the OP is a bit too cheaty.

Not at all cheaty. Each part could have a mean distance for COM offset. When taken together the offset would be very noticeable and make a real difference in performance.

Car chassis in many cases are designed to be a little heavier and the frame and material above it designed to be lighter to get the COM as close to the level of the chassis as possible.

It isn't possible to do this in game which is why people who build rovers use aircraft engines to offset the COM. They know the game needs it and attempt to rectify the problem. Adding considerably more mass to move the COM an unrealistic amount.

If all the physics of KSP worked as it should, (No offence Squad - you didn't write the engine and your attempts at fixing it are to be applauded.),  then planes and landers wouldn't dance and it would't be necessary to shunt all remaining fuel in your re-entering Space Plane to the front to stop it doing somersaults.

However some things can be done to improve things over all and this is, I think, one of them.

 

[Daveroski]

1 minute ago, HebaruSan said:

To elaborate, when you build a rover and it tips over, that's the game showing you that designing a wheeled vehicle has challenges. Challenges grounded in physics, that can even vary from environment to environment, and there are all sorts of strategies available for handling them. It's a feature, not a bug.

 

I will not pooh-pooh what you say as you clearly think you are right. So please demonstrate this with one of your rovers that works really well on Minmus carrying 4 kerbals in a hitch-hiker module. Go up and down some hills in it. Then tell me how wonderfully realistic the physics of KSP are.

10 minutes ago, HebaruSan said:

Real life vehicle designers have to move the center of mass the old fashioned way, by moving actual massive parts downwards. You're meant to do the same in KSP. When you crash a rover and update it (whether it's CoM or wheel base width or steering or whatever) and it drives better, that's the core KSP gameplay loop working well.

Real life designers, and I know what I'm talking about here, Use parts that are themselves made with the COM as appropriate as possible. All of KSP parts have the COM dead-center. With the exception of a couple of engines that people use to try to offset the unrealistic nature of that which is KSP.

15 minutes ago, HebaruSan said:

But rovers aren't the biggest reason why this idea should not be implemented. Consider the effect on planes and rockets. Instead of learning to design a plane with a CoM and CoL properly aligned, the player can simply drag the CoM around and magic any design into flightworthiness. Instead of learning to construct rockets with the heavy bits in front and the draggy parts at back, again you can simply drag the CoM to the top and be done with it. Significant portions of the gameplay are deleted.

If you had paid attention or even queried my proposal when I could have reiterated "Within reason of course"

Enough to make it more realistic, not unrealistic.

You missed it though. You just jumped in thinking I was trying to make KSP 'Magic' and decided to put me in my place.

That is why you are rude.

 

 

[pandaman]

Interesting idea.

I guess what the OP wants to simulate is rearranging the internal components of a large complex part (like a lander can) to adjust the CoM so that it is more appropriate for what you are trying to build.

The idea makes some sense, and i quite like it, but i'm on the fence as to how practical or useful it would be.

[qzgy]

3 hours ago, Rocket In My Pocket said:

Not if you make one half of it out of a less dense material. Ie. A half plastic/half metal cube would have most of it's weight concentrated on the metal side, and thus would have an off center COM.

A rectangle would obviously be better, but would be more awkward to use.

It would still be a bit of a stretch for this to move the vehicles COM significantly, but hey like you said; it's KSP.

Ok, so something like that. I thought of a thing which had its COM unrealistically outside of its actual part. At that point though, why not just use actual ballast smaller and more dense? Because effectively you're just asking for a lump of metal.

1 hour ago, Daveroski said:

If you had paid attention or even queried my proposal when I could have reiterated "Within reason of course"

Enough to make it more realistic, not unrealistic.

Who defines that? I may say moving the COM about 0.5M is realistic, although on very small craft that might effectively make it impossible to tip, while on large craft basically moot. "Make it realistic" is a very vague statement, especially when its such a broad thing like this.

1 hour ago, Daveroski said:

Real life designers, and I know what I'm talking about here, Use parts that are themselves made with the COM as appropriate as possible. All of KSP parts have the COM dead-center. With the exception of a couple of engines that people use to try to offset the unrealistic nature of that which is KSP.

First, I wouldn't parade yourself as a man "who knows everything because I do this stuff for real". Yes, you might, yes, it probably is true, but it opens you up for attack from others and also makes you look a bit... high on your horse lets say.

The reason most KSP parts have the COM dead center is because that's where the COM is. Or roughly is. Close enough to not worry about it. You wouldn't expect a round homogeneous battery to have its COM higher or lower up, or on its edge or something. The Jet engine thing is part of that. Because they are relatively heavy parts, they would normally (in real life I assume) add their mass and bulk more in the fuselage, because the actual pat isn't limited to the tiny exhaust that we see. Having all that mass more towards the center is something more realistic than the Jet engines having their COM right at the very tail, which would also incidentally make it a lot harder to design planes. Any examples with builders intentionally abusing that to make their COM lower is just that - an abuse of the system. It is an abuse that has to exist though for the sake of balancing their primary role as jet engines.

The basic challenge in KSP is being given those parts and making something (read - arranging the parts) in such a way that it does work suitably well, keeping the COM and stuff in such a way that your thing actually works. As HebaruSan mentioned also, the ability to play fast and loose with it removes part of that critical challenge. NO, would it be ideal to make your parts in such a way that more weight is kept lower? Yes, it would, but KSP parts have to work in every single situation without being too weird. If it is too high, too low, too far forward or too far back, one can simply just add ballast in the necessary places to make the design work.

2 hours ago, Daveroski said:

it would't be necessary to shunt all remaining fuel in your re-entering Space Plane to the front to stop it doing somersaults.

actually, depending on the design. yes it would. if it does that, the design doesn't account for fuel mass not existing and then the thus relative dry COM/COL positioning. It's perfectly possible to make a design that flies nicely without pumping fuel.

[Vanamonde]

Watch the tempers please, folks. We can disagree about game matters without attacking each other. 

[HebaruSan]

Quote

You missed it though. You just jumped in thinking I was trying to make KSP 'Magic' and decided to put me in my place.

I didn't miss anything. I read every word you wrote and considered them in the context of the game. Specifically:

On 12/25/2018 at 2:53 PM, Daveroski said:

I would like to be able to go so far as to be able to move the COM on a rover below the wheels

CoM below the wheels. The wheels are on the ground, so this would put the CoM at ground level or underground. There's nothing "within reason" about that; it's as "magic" a situation as you could imagine.

[snip]

Edited December 26, 2018 by Deddly
Minor trim to avoid escalation of the previous issue

[Gargamel]

7 hours ago, Daveroski said:

I will not pooh-pooh what you say as you clearly think you are right. So please demonstrate this with one of your rovers that works really well on Minmus carrying 4 kerbals in a hitch-hiker module. Go up and down some hills in it. Then tell me how wonderfully realistic the physics of KSP are.

Well, that's because a sensible design for a rover wouldn't include a huge blocky part that will force your rover to roll over.    The COM is there for a reason, as the part is some size, and the mass is located somewhere within the part.   Yes we have engines with weird COM's, but those are done for a very reasonable reason. 

Take a look this poorly designed rover:

There's no way such a design can handle turns, as it's COM is way too high.    First time it tries to take a corner, it will definitely.....      oh wait.... these are actually quite widely used, because the people operating it can account for this center of mass being higher, and drive appropriately. 

So while there are times I wouldn't mind having this tool, it would definately be overpowered and cheaty to me.  If my COM is way too high for a rover, I just redesign it so it's not.    I also understand the limits of the rovers I have made, and drive them in a safe manner.  

[HvP]

7 hours ago, Daveroski said:

So please demonstrate this with one of your rovers that works really well on Minmus carrying 4 kerbals in a hitch-hiker module. Go up and down some hills in it. Then tell me how wonderfully realistic the physics of KSP are.

A real spacecraft engineer wouldn't even begin to imagine going the speeds KSP rovers are capable of in low gravity environments. The lunar rover topped out at about 5 meters-per-second and the mars rovers are struggling along at less than 0.04 m/s.

Remember that while gravitational attraction to the ground may be reduced, mass inertia in a straight line never changes.

Edited December 26, 2018 by HvP

[KSK]

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

Well, that's because a sensible design for a rover wouldn't include a huge blocky part that will force your rover to roll over.    The COM is there for a reason, as the part is some size, and the mass is located somewhere within the part.   Yes we have engines with weird COM's, but those are done for a very reasonable reason. 

Take a look this poorly designed rover:

There's no way such a design can handle turns, as it's COM is way too high.    First time it tries to take a corner, it will definitely.....      oh wait.... these are actually quite widely used, because the people operating it can account for this center of mass being higher, and drive appropriately. 

So while there are times I wouldn't mind having this tool, it would definately be overpowered and cheaty to me.  If my COM is way too high for a rover, I just redesign it so it's not.    I also understand the limits of the rovers I have made, and drive them in a safe manner.  

Actually, I think that bus makes @Daveroski‘s point quite well. It’s centre of mass isn’t dead centre, KSP style and will be sufficiently low that it can corner safely, despite its height.

KSP design isn’t finely grained enough to let us make like bus designers and, for example, put the heavier subsystems of a Mk1 capsule at the bottom to lower its centre of mass. So we’re left with fixed CoMs which may or may not be realistic or useful, or ugly hacks like sticking a jet engine on a Mun rover to make it more stable.

With a couple of tweaks to @Daveroski‘s proposal, I think a CoM widget would be a good and useful addition to the game.

Tweak number one - only allow parts with significant internal heterogeneity to have their CoM tweaked. In other words, crew compartments and possibly the RoveMate. Big components with a decent amount of internal space which the player can readily imagine being made up of various subsystems in real life.

Tweak number two - the CoM can only be shifted to within a certain distance of the collider for that part. Or some other mechanism that would a) prevent the CoM moving outside the part and b) reflect the fact that real world parts do have a thickness and shouldn’t be considered as an arbitrarily thin shell with a mass somewhere within it (even if that’s how KSP is modelling it  ).

Edited December 27, 2018 by KSK

[Gargamel]

3 hours ago, KSK said:

will be driven by a skilled driver that it can corner safely, despite its height.

FYP.  

The point is, while a rover can be tweaked and such all you want at design time, it is ultimately up to the driver to to drive it safely.   A rover with a COM that is at the level of the bottom of the tires, will still flip over if it is driven off a cliff. 

I usually do not have any issue with rovers, as I design them to be wide and low, and I drive them safely. 

[KSK]

3 hours ago, Gargamel said:

FYP.  

The point is, while a rover can be tweaked and such all you want at design time, it is ultimately up to the driver to to drive it safely.   A rover with a COM that is at the level of the bottom of the tires, will still flip over if it is driven off a cliff. 

I usually do not have any issue with rovers, as I design them to be wide and low, and I drive them safely. 

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

[FleshJeb]

On 12/25/2018 at 11:25 AM, Daveroski said:

...and it would't be necessary to shunt all remaining fuel in your re-entering Space Plane to the front to stop it doing somersaults.

While I think your proposal has some merits, I have to disagree.

I think one of the absolutely key portions of KSP gameplay is learning to design elegantly and well given the limited number of parts. Yes, it’s challenging, but it can be done. Having restrictions increases gameplay depth, and makes the good solutions that much more satisfying. I’m reminded of what my high school English teacher said about Shakespeare writing in iambic pentameter, “He accepted the restrictions because it was hard; he’s considered great because he did it beautifully.”

Back to your spaceplane complaint: Real life airplanes pump fuel for balance. The Concorde was notorious for it. However, KSP is a lot easier than real life, and if someone has to pump fuel for balance, I think they just haven’t yet learned how to design without needing to.

In any case, thank you for presenting the idea. It’s very creative and pretty well thought out—I just don’t think it fits within the scope of KSP.

ADDENDUM: I also think it would enforce bad design habits by giving players an easy out. Most of the “awkward” craft that I’ve seen (and created) are a result of a poor understanding of physics and mechanics, not a flaw of KSP.

Edited December 28, 2018 by FleshJeb

[KSK]

2 hours ago, FleshJeb said:

ADDENDUM: I also think it would enforce bad design habits by giving players an easy out.

Given how much KSP abstracts away real world engineering concerns, I think that argument is more than a bit subjective. To use a much chewed over counter-example, one could argue that the lack of life support requirements in the stock game is enforcing bad design habits by giving players an easy way out, vis ignoring a significant constraint on spacecraft design  altogether.

With some caveats to the original proposal (see my previous post), I would regard a CoM widget as a convenience, in the same way that using existing widgets to fine tune aircraft wing position is a convenience. The player still needs to understand why that CoM needs to be in a particular place but having a widget to move it around (within reason) means that you don’t need to completely redesign a craft to implement a minor change, or hang a bunch of extraneous parts off that craft simply to move its CoM around a little.

Put another way, it would help the player design elegantly and well with a limited number of parts, as you wanted.

 

Edited December 28, 2018 by KSK

[Hotel26]

35 minutes ago, KSK said:

KSP abstracts away real world engineering concerns

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?

 

Edited December 28, 2018 by Hotel26