Are fairings useless?

[Wemb]

Playing with a few utility type mods such as MJ, RasterPropMonitor and Docking Port Alignment Indicator but nothing (AFAIK) that affects aerodynamics - and am having terrible trouble when using fairings.

In short, most of the time, if I use fairings, my rockets tend to flip up and over early into the gravity turn - assume because the fairing is generating a ton of lift a the front of the rocket and it's pivoting about the engine. I would normally assume that this is because my rocket is inherently unstable - but this doesn't seem to be the case as generally they fly perfectly well without the farings at all....  

What's the practical purpose of fairings currently? The added weight, control systems, etc to prevent them flipping out has made my rockets that use them more expensive to get into orbit, rather than less aerodynamic, but more stable launchers. Am I missing something obvious?

Wemb

[Warzouz]

In 1.0.5 (not in 1.0.4) there is a but with fairings. The body lifting force is applied far in front of the fairing (outside of the rocket !), then the rocket would flip MUCH faster if you use a fairing than if you don't. As soon as you quit prograde, the rocket with start a unrecoverable flip.

I stop playing KSP mostly because of that bug. I'm waiting for 1.1

Edited January 19, 2016 by Warzouz

[Rodyle]

28 minutes ago, Warzouz said:

In 1.0.5 (not in 1.0.4) there is a but with fairings. The body lifting force is applied far in front of the fairing (outside of the rocket !), then the rocket would flip MUCH faster if you use a fairing than if you don't. As soon as you quit prograde, the rocket with start a unrecoverable flip.

I stop playing KSP mostly because of that bug. I'm waiting for 1.0.5

Damn. That explains why my fairinged rockets make their gravity turns much slower than I would expect them to.

[Frozen_Heart]

Yeah fairings are bugged in 1.0.5 and I've stopped using them. They apply their drag force beyond the rockets nose and cause it to flip.

Hopefully it will be fixed in 1.1.

[Warzouz]

11 minutes ago, Rodyle said:

Damn. That explains why my fairinged rockets make their gravity turns much slower than I would expect them to.

I don't see why, but with that but, you have not much choice than to set SAS to prograde and hope for the best...

Maybe you can use the "Procedural Fairings"  mods. It may not have this bug. (But as I don't use it, I don't know for sure)

[Rodyle]

1 minute ago, Warzouz said:

I don't see why, but with that but, you have not much choice than to set SAS to prograde and hope for the best...

Maybe you can use the "Procedural Fairings"  mods. It may not have this bug. (But as I don't use it, I don't know for sure)

Well, because the lift is further further in front than it should be, it creates a bigger moment-arm, which makes it so that the force of the lift should be able to hold the rocket pointed up further than it should.

[soulsource]

A workaround for that bug is to use FAR.

[Warzouz]

22 minutes ago, Rodyle said:

Well, because the lift is further further in front than it should be, it creates a bigger moment-arm, which makes it so that the force of the lift should be able to hold the rocket pointed up further than it should.

Yes and the only way to avoid it is to target prograde as much as possible. The usual 5° AoA maybe equivalent to a 15° or 20° AoA, due to this bug. With the new aero this doesn't end well...

[MagicFireCaster]

I keep using them, just remember if your ship is flipping try slowing down, the ship flips when you're going too fast in lower atmosphere. 

[Tex_NL]

1 hour ago, Warzouz said:

In 1.0.5 (not in 1.0.4) there is a but with fairings. The body lifting force is applied far in front of the fairing (outside of the rocket !), then the rocket would flip MUCH faster if you use a fairing than if you don't. As soon as you quit prograde, the rocket with start a unrecoverable flip.

I stop playing KSP mostly because of that bug. I'm waiting for 1.1

It still amazes me that this ever got through. Somebody really dropped the ball during the 1.0.5 testing phase.
But why stop playing when there is an excellent bug fix for this? Claw's Stock Bug Fix puts the body lift back where it belongs.

[Wemb]

Thanks everyone - glad I wasn't going mad...  I'll give up on them till 1.1 now. Thanks!

Wemb

[Streetwind]

1 hour ago, soulsource said:

A workaround for that bug is to use FAR.

Is that hearsay, or confirmed? I tried to ask this in multiple places when the fairing bug was first discovered, and never so much as even got a reply. So I'm kinda curious now.

[Plusck]

I'm still undecided whether the fairing lift bug means that you're better off without them, or not.

For all of my most recent draggy payloads I've used fairings. That means that you need to get the gravity turn just right and stick to prograde as soon as you have any speed, but I've yet to have a situation where that wasn't possible to achieve (at most with a revert or two to tweak / add fins and fine-tune the trajectory). Yes it's an inconvenience, but without fairings drag would have been terrible, and I haven't felt the need to go slower except, possibly, for the first few thousand metres altitude.

 

[Blaarkies]

20 hours ago, Streetwind said:

Is that hearsay, or confirmed? I tried to ask this in multiple places when the fairing bug was first discovered, and never so much as even got a reply. So I'm kinda curious now.

It works with FAR, no ill effects...however, I do use the Stock Bug Fix Modules (by Claw). With both these mods, I frequently send up SSTO rockets with absolutely no fins or wings or airbrakes (inspired by SpaceX's Falcon9), and everyone survived.

In KSP we cannot simultaneously control both ships, thus I build a massive 2orange-tanks+twin-boar SSTO that can lift about 10t payload into LKO. This SSTO uses some left over fuel to de-orbit, and weigh down the back end. I cannot even risk fins on the bottom of the engine because they will flip me over on re-entry...but you have to stay true to prograde on launch.

So before you reach 100ms, you already need a slight east tilt. Then lock to prograde and keep it centered until about 40km altitude, from then on you can easily control the craft as you see fit. Engine gimbal does most of the work, so you are not really allowed to drop the thrust to below 30%. This thing costs way more than it should to put 10t into orbit, but when i land this near ksc the whole missions ends up costing 15k-17k.

[Dunbaratu]

23 hours ago, Warzouz said:

In 1.0.5 (not in 1.0.4) there is a but with fairings. The body lifting force is applied far in front of the fairing (outside of the rocket !), then the rocket would flip MUCH faster if you use a fairing than if you don't. As soon as you quit prograde, the rocket with start a unrecoverable flip.

I stop playing KSP mostly because of that bug. I'm waiting for 1.1

That explains a LOT.  I kept wondering why adding fairings to my payloads actually made my rockets flip MORE than when they weren't there.  Seems to completely invalidate the entire POINT of having fairings.

 

[ForScience6686]

Hmm, this is odd, I have not experienced any control issues when using fairings.  and I use them on just about everything except planes.  I'd want to see what the craft looks like to see if there are any other possible issues with how you've built it and the launch profile used.  I just haven't experienced the issues you guys are bringing up.  Usually, you're trying to protect something larger than the core stack and the fairing is going to create a larger profile to protect it.  Does this not mean that any deviation from prograde will cause a huge drag spike that begins the flip.  Of course, unless you build your rocket properly.  

Being a cylindrical object, how would it induce lift unless off of prograde?   at that point it would be the same as body lift on a space plane correct?

 

[swjr-swis]

I am not entirely sure if I am 'suffering from' this issue, or benefiting from it, with this particular build...

The 'dish' is two 3.75m fairings, back to back. Notice the aero vector starting in the empty air above the dish. It goes a loooong way...

 

[Warzouz]

@swjr-swis, it seems to be good. The light blue line starts from the center of the forward part. Seems logical.

 

Here is what it looks like when it messes. you can see body lifting from many parts, but there is one in front of the fairing and not on the fairing. It seems the position of the application of the force is right, but it's set at the top of the fairing as it should be set at the bottom of it.

I don't understand why Squad didn't do a quick fix about that.

[swjr-swis]

20 minutes ago, Warzouz said:

The light blue line starts from the center of the forward part. Seems logical.

20 minutes ago, Warzouz said:

Here is what it looks like when it messes. you can see body lifting from many parts, but there is one in front of the fairing and not on the fairing.

I think they are the same thing. Look closely: in my case the same as yours, the base of that line starts away from the fairing, there's a good bit of empty space between them, where it should start inside the part. And they point in the same direction, if you consider that my fairing is 90 degrees rotated compared to yours (facing 'radial' instead of 'prograde', from the ship's perspective).

Also, I am not convinced that the vector should really be that large.

[Foxster]

There are (IMHO) at least three things currently wrong with fairings:

The bug discussed above.

Their drag is about double what it should be. 

Their weight is about double what it should be. 

Plus it's hard to stabilise loads inside them, but that's being fixed in 1.1. 

It is almost always better to streamline a craft than to use a fairing. You can also put your scrappy bits and pieces in a service or cargo bay rather than wrapping them in a fairing.

Really fairings are just handy for the lazy or not-so-experienced rocket builder. You can  throw any old stuff together on top of a rocket, stick a fairing around it and call it a rocket. Doesn't work too well though.  

There is the odd occasion though when you have a really un-aerodynamic load (maybe a Laythe aircraft or a fat rover) and the only way to get it to orbit is with a fairing. 

[Tex_NL]

To deal with this bug there are two options:

1. Use the bug fix as I have already suggested yesterday.
2. Exploit the bug and use it to enhance stability. Instead of building your standard fairing 'bottom up' place a decoupler on top of your payload and build in-line fairing 'top-down'. This way the bug places the body lift vector way lower on your craft than it should be. Possibly even behind the CoG making your craft incredibly stable.

[fourfa]

On 1/20/2016 at 1:05 PM, Tex_NL said:

Exploit the bug and use it to enhance stability. Instead of building your standard fairing 'bottom up' place a decoupler on top of your payload and build in-line fairing 'top-down'. This way the bug places the body lift vector way lower on your craft than it should be. Possibly even behind the CoG making your craft incredibly stable.

...except that 90% of the time, it's impossible to get the fairing to close on existing stages

[hellblazer]

You need a heavier payload or a lighter first/second stage. Rockets are supposed to be like a dart (top heavy)

[soulsource]

On 19.1.2016 at 4:11 PM, Streetwind said:

Is that hearsay, or confirmed? I tried to ask this in multiple places when the fairing bug was first discovered, and never so much as even got a reply. So I'm kinda curious now.

I'm playing with FAR and I never noticed any issues regarding fairing drag. Also, I've been launching rockets I built for 1.0.2 in 1.0.5 (both cases with FAR installed) and they handle exactly the same, as far as I can tell. So if my experience isn't misleading, I'd say I can confirm this.

I suspect FAR can work around this, because it builds a voxel representation of the craft based on the colliders of the craft's parts, and then calculates aerodynamic properties based on this voxel representation.

[ExtremeSquared]

I've encountered a separate fairing bug where the contents of the fairing are subject to aerodynamic forces as if the fairing isn't there at all. It could be a linux bug, as fairings seem especially buggy on linux builds. So the answer is yes.