Anybody Else Notice..

[Charley575]

...that Spaceplanes are really hard to control now? If your center of mass is even slightly behind the spacial center of the vehicle, then the vehicle becomes DESPERATE to flip over and fly backwards. Or such has been my experience.

[Red Iron Crown]

It's the relationship between center of mass and center of lift that matters, not spatial center. This plane has a CoM in the middle of the payload bay and is quite stable, because the CoL is even further rearward:

[Alshain]

That's because the new aero added more to think about than just CoM/CoL relationship. Drag, such as large intakes too far in the front, can cause you to flip too. Show us your plane.

[Charley575]

I've seen this on an early Mk.1 design and also my latest Mk.2 design. Even set the COL slightly behind the COM to compensate. No joy. Actually flew ok on the way up, but it was a tumble and roll all the way back. Until the damn thing crashed to desktop, that is. Maybe I'll go back in and grab a screenshot later. Too fed up to go back in now.

[hellion13]

Im imagining its a normalized plane with wings and fuel and such. But I wonder about where you've place the fuel, as it gets used faster now. If the CoL is too close to the CoM, as soon as any fuel is used mass gets shifted backwards(fuel runs backwards) putting the CoL in front of the CoM, effectively ruining any hope of stable flight.

Turn on the displays in the sph and empty the fuel front to back you can see it happening.

Edited June 27, 2015 by hellion13

[Guest]

Pump all of your fuel to the forward-most tanks before beginning reentry.

Maintaining COM by pumping fuel around is important in space planes and large aircraft.

[mike9606]

I find that aircraft like to flip far too much now. With designs that would have worked perfectly fine in previous versions now like to flip oevr for no reason. It seems that you have to have the CoL DIRECTLY in the middle of the CoM or else your craft will flip over. For Example: My KT-1 Dodo (Mk3 Airliner powered by 4 PT-100 TUrboprops from KAX), which flew perfectly fine in the version that it was deisgned (1.0.3 or 1.0.2) now can barely keep itself from flipping with SAS. I think I'm gonig to install FAR because frankly the amount these aircraft want to flip is stupid. The KT-1's CoL is in the middle of the CoM or atleast close as you can get without extreme fine tuning.

[clivman]

I find that aircraft like to flip far too much now. With designs that would have worked perfectly fine in previous versions now like to flip oevr for no reason. It seems that you have to have the CoL DIRECTLY in the middle of the CoM or else your craft will flip over. For Example: My KT-1 Dodo (Mk3 Airliner powered by 4 PT-100 TUrboprops from KAX), which flew perfectly fine in the version that it was deisgned (1.0.3 or 1.0.2) now can barely keep itself from flipping with SAS. I think I'm gonig to install FAR because frankly the amount these aircraft want to flip is stupid. The KT-1's CoL is in the middle of the CoM or atleast close as you can get without extreme fine tuning.

Im experiencing a weird problem where my planes are perfectly stable without thrust but go into a tumble when i start the engine

[SkyRender]

A picture is worth a thousand words, a .craft file is worth two thousand five hundred. It's hard to diagnose a problem without something to look at, let alone interact with. My suspicion, however, is that the flip-happy problem is caused by something silly like shifting center of mass. Though it could be the comedy gold that is center of thrust in front of center of mass. That one always cracks me up.

[Charley575]

I know that I seem like a noob because I don't post here often, but I've been playing the game since ver 0.24 (at least) so I know about fuel balancing and all that. I still think it's related to something they did to make sure capsules come down heat shield first. It seems that anything that's heavier in the rear wants to fly that way.

[mike9606]

Ok, here's the .craft for the KT-1. Mods Required: Adjustable Landing Gear, KAX. .Craft File

[SkyRender]

I know that I seem like a noob because I don't post here often, but I've been playing the game since ver 0.24 (at least) so I know about fuel balancing and all that. I still think it's related to something they did to make sure capsules come down heat shield first. It seems that anything that's heavier in the rear wants to fly that way.

Seriously, provide a .craft file. We'd be happy to diagnose the issue for you, but until you do, all we can do is speculate.

[Red Iron Crown]

Though it could be the comedy gold that is center of thrust in front of center of mass. That one always cracks me up.

What's wrong with CoT in front of CoM? I make spacecraft like that all the time.

[SkyRender]

What's wrong with CoT in front of CoM? I make spacecraft like that all the time.

It works great as long as you don't have much lift. If you do have lift, well... Let's just say it does bad things. Very bad things.

[LittleBlueGaming]

I've noticed my smaller aircraft seem to flip, rather than turn on a dime at a bagillion-g's. Makes sense, you can't have a draggy nose and bank hard at 1000m/s.

I use gentle inputs, trim adjustment now more than I used to.

[SAI Peregrinus]

That's the plane from OP's^H^H^H^Hmike9606's .craft file.

Now, what's wrong? Just about everything when it comes to flipping.

First, CoL is way ahead of CoM. So it's going to flip.

Second, CoL is below CoM, so it's going to flip even harder.

Third, CoT is not in-line with CoM, so it's going to flip yet harder.

Not related to flipping, but the ailerons are right next to the body instead of at the ends of the wings. It has terrible roll performance.

That plane really, REALLY wants to be facing with its nose up and towards the rear.

On the good side, the fuel is all to the rear, so the CoL tends to shift backwards.

Move the wings back and up. Move the ailerons out.

Edited June 27, 2015 by SAI Peregrinus

[mike9606]

Oops, that's mine. I thought the .craft file thing was directed at me. That craft does have the same issue though. I guess my editor is broken though. The CoL and CoM are in different places for me. I don't know why the CoM and CoL are in different places in your editor.

[SAI Peregrinus]

Aah, misremembered the names. I know FAR will mess up the CoL marker (but give much, much better tools for finding stability), so if you've got that installed it might explain that. Not sure why the CoM would move though.

[mike9606]

Aah, misremembered the names. I know FAR will mess up the CoL marker (but give much, much better tools for finding stability), so if you've got that installed it might explain that. Not sure why the CoM would move though.

I have mods, but FAR is not one of them.

[Overland]

Not entirely sure about space planes as such.. but I have this plane I call the "Ugh-Y" series thats persisted across recent releases from 90 onwards..

it flies perfectly.. stable.. dont even need SAS.. its cruise speed is around 1200m/s

its still stable as a rock and I got no idea why..

http://kerbalx.com/Overland/Ugh-Y

anyone wishing to test can download.. fully stock.. ignite first engines with pressing action group 1..

ignite the second group with 2 when around 1000 feet..

as to why or how it flies.. no idea.. I been thinking for a long time some of the airliner parts have strange properties

Edited June 28, 2015 by Overland

[Superfluous J]

I know that I seem like a noob because I don't post here often, but I've been playing the game since ver 0.24 (at least) so I know about fuel balancing and all that. I still think it's related to something they did to make sure capsules come down heat shield first. It seems that anything that's heavier in the rear wants to fly that way.

Go outside right now (or wait until sunrise) with a hammer, and toss it up into the air. Try as hard as you can to make it land on the handle, instead of the head.*

Air resistance FORCES the heavier parts of craft to the front, all other things being equal and sometimes in spite of your trying to make them unequal. This was not modeled correctly prior to 1.0 and is modeled (more) correctly now. It's not a bug. It's a fact of life.

*And please do so away from anything breakable. Preferably on soft ground too like a lawn instead of a driveway.

[Col_Jessep]

That's why my cat always lands on her feet: Center of Mass points along the velocity vector and her belly is definitely the center of mass... =3

[BlueCanary]

Just read the last two posts two fast, got mixed up and thought someone was planning to throw a hammer at their cat.

I don't know about other people but flipping is the only thing I haven't had problems adapting too in 1.0+, although I am finding that planes become increasingly unstable and flippable at high speeds, until at above about 900m/s their yawing all over the place. I don't know if that's just me messing up, or part of the new aerodynamics though. Any ideas?

[Charley575]

Go outside right now (or wait until sunrise) with a hammer, and toss it up into the air. Try as hard as you can to make it land on the handle, instead of the head.*

Air resistance FORCES the heavier parts of craft to the front, all other things being equal and sometimes in spite of your trying to make them unequal. This was not modeled correctly prior to 1.0 and is modeled (more) correctly now. It's not a bug. It's a fact of life.

*And please do so away from anything breakable. Preferably on soft ground too like a lawn instead of a driveway.

Yeah, I get that. But a Cessna is heavier in the front than it is in the rear because of the mass of the engine. Yet, it flies, because the wings sit over the COM.

- - - Updated - - -

Ok, so I guess I AM a noob when it comes to attaching files to posts. Can someone tell me how to do that? I guess this means I'm getting old. I have to ask some youngin' how to make the VCR clock stop flashing 12:00. Did I just use a VCR reference? Crap!

I know how to locate the file on my hard drive I just can't find the button or whatever to attach something here.

[pandaman]

Yeah, I get that. But a Cessna is heavier in the front than it is in the rear because of the mass of the engine. Yet, it flies, because the wings sit over the COM.

- - - Updated - - -

Ok, so I guess I AM a noob when it comes to attaching files to posts. Can someone tell me how to do that? I guess this means I'm getting old. I have to ask some youngin' how to make the VCR clock stop flashing 12:00. Did I just use a VCR reference? Crap!

I know how to locate the file on my hard drive I just can't find the button or whatever to attach something here.

what 5th is saying is that the hammers COM is inside the head, and the hammer will rotate around its COM as you know. Due to aerodynamics the handle will behave like the tail in a dart and trail out behind as the hammer falls. Even a dart with the flights not fitted into the stem will still fly pointy end first, just not as stable as with them.

Hope this helps.