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Wait, WHAT? (Fairings)

Frybert

By Frybert
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Brotoro

Brotoro

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Not shedding the mass would certainly be a problem -- you don't want to be carrying the mass of a fairing you already ejected.

Not having the mass in the first place is also a problem -- there is no penalty for putting on a bigger fairing.

Not having the mass in the correct location is ALSO a problem -- the mass of the fairing should be bringing your rocket's CoM forward (not having it back at the base part, if it even did that) where it will help it be more stable.

Not realizing this is a problem is ALSO a problem.

Edited by Brotoro
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Sandworm

Sandworm

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Thats not the only wacky thing they do.

Lol. I think that confirms that "fairings" and anything within them are simply out of the mass/heat part of the physics engine. That isn't a bug. That is a design decision. Someone sat down and decided that they wanted things that way.

Edited by Sandworm
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hcalves

hcalves

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not shedding the mass would certainly be a problem -- you don't want to be carrying the mass of a fairing you already ejected.

Not having the mass in the first place is also a problem -- there is no penalty for putting on a bigger fairing.

Not having the mass in the correct location is also a problem -- the mass of the fairing should be bringing your rocket's com forward (not having it back at the base part, if it even did that) where it will help it be more stable.

Not realizing this is a problem is also a problem.

This.

It seems SQUAD had to get 1.0 out and this was a dirt fix.

1) They probably implemented a first prototype, then for Unity reasons had to make fairings panels physic-less parts.

2) Because of that, the mass had to go into the base.

3) Someone play testing noticed having the mass on the base made no sense.

4) Finally they made it have no mass *really*, just simulate the mass to count towards the new VAB mass limit mechanic.

5) Sneak into 1.0 and hope no ones notices :)

I hope they address this in the next patch.

Edited by hcalves
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Frybert

Frybert

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As the fairings themselves are massless, can't you start your base much lower in your stack, and just make the fairing go up tight to the side? That way, you can drop the base with one of your lower ascent stages instead of carrying it all the way to Duna.

And I'm sorry, but I just have to put this here.

The mass is all about the base, no fairings.

Oh I think I have an idea. And if it works, the forums will never forgive you for giving it to me!

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FlowerChild

FlowerChild

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Oh I think I have an idea. And if it works, the forums will never forgive you for giving it to me!

Here comes the gigantic bulbous and entirely efficient rockets completely covered in fairings that I was just considering building myself :)

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tetryds

tetryds

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So what's the bigger problem here? That you discarded your fairings a kilometre from the ground or that you're trying to ascend while looking at stuff you've discarded?

I was just pointing out that it's very strange, because they show to have mass on the editors.

Found it funny that you can simply lift them with a tinny engine, and that they should move the center of mass, but don't.

@Frybert, yeah, haha, I did not catch up with those.

This is not a complaint though.

Can that be toggled somewhere?

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Katalliaan

Katalliaan

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I was just pointing out that it's very strange, because they show to have mass on the editors.

Found it funny that you can simply lift them with a tinny engine, and that they should move the center of mass, but don't.

Any part with "PhysicsSignificance = 1" (which actually means it's not affected by physics) will show mass in the engineer's report. However, they don't appear to affect the CoM indicator, and they certainly don't affect the way a craft behaves. It's like how both of these craft will behave in the same way (other than how much electric charge they carry), even though the engineer's report shows that one has an extra ton off to one side.

EDIT: Just repeated the test with a 2-ton fairing in the place of the battery arm, and it went off-center. Not sure if that's due to drag or mass, though.

Edited by Katalliaan
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tetryds

tetryds

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Any part with "PhysicsSignificance = 1" (which actually means it's not affected by physics) will show mass in the engineer's report. However, they don't appear to affect the CoM indicator, and they certainly don't affect the way a craft behaves. It's like how both of these craft will behave in the same way (other than how much electric charge they carry), even though the engineer's report shows that one has an extra ton off to one side.

Yeah, I know how that works, I believe that since the game already knows what would be the mass of the fairing, it should apply a COM shift and increase weight of the fairing base to match what the fairings would have.

Then, when ejected, this difference should be removed.

That would be a way to make the fairings have weight keeping them physicsless.

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Frybert

Frybert

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Yeah, I know how that works, I believe that since the game already knows what would be the mass of the fairing, it should apply a COM shift and increase weight of the fairing base to match what the fairings would have.

Then, when ejected, this difference should be removed.

That would be a way to make the fairings have weight keeping them physicsless.

According to the Devs, the mass of the fairing was supposed to be added to the base. That does not appear to be working ATM.

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Katalliaan

Katalliaan

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Okay. So I modified my testbed (without the battery arm) with a 0.4 ton fairing on top and turned off drag to eliminate aerodynamic forces from the equation and did three tests:

- Fairing attached throughout test: apoapsis of 54,659m

- Fairing ditched at launch, base attached: apoapsis of 54,659m

- No fairing: apoapsis of 187,670m

So I can confirm that they DO add mass, and it's all in the base.

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Frybert

Frybert

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Okay. So I modified my testbed (without the battery arm) with a 0.4 ton fairing on top and turned off drag to eliminate aerodynamic forces from the equation and did three tests:

- Fairing attached throughout test: apoapsis of 54,659m

- Fairing ditched at launch, base attached: apoapsis of 54,659m

- No fairing: apoapsis of 187,670m

So I can confirm that they DO add mass, and it's all in the base.

With that same craft, make the fairing .8t and run your tests again.

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pincushionman

pincushionman

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Okay. So I modified my testbed (without the battery arm) with a 0.4 ton fairing on top and turned off drag to eliminate aerodynamic forces from the equation and did three tests:

- Fairing attached throughout test: apoapsis of 54,659m

- Fairing ditched at launch, base attached: apoapsis of 54,659m

- No fairing: apoapsis of 187,670m

So I can confirm that they DO add mass, and it's all in the base.

Threads got merged, so there's going to be a little confusion. Check my results on page 5 of this merged thread - I found that while the fairing base is massful, the supposed weight of the panels is never added, but confirmation/refutation by independent tests is a good part of science. In your "no fairing" test, did you have "fairing base but no panels" or "no fairing parts at all"?

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Frybert

Frybert

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Here's a test I just performed:

Made a base craft of the round 1m pro core, smallest 1m fuel tank, and reliant engine.

Hyperedited 4 of them into 100 x 100 km orbit around Kerbin.

Fired prograde until out of fuel.

Results:

Craft 1: Base craft, no fairing/fairing base - 27.59Mm apo

Craft 2: .5 ton 1m fairing - 8.67Mm apo

Craft 3: 1 ton 1 m fairing - 8.67Mm apo

Craft 4: 1 ton 2 m fairing - 4.56Mm apo

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waterlubber

waterlubber

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Here's my conclusion:

1. Fairing bases (1.25, 2.5, and 3.75 m) have a flat mass. This mass counts for everything.

(This mass is high, for some reason)

2. Fairings themselves are completely massless. However, in the engineer report, this mass shows.

3. Ejecting fairings does nothing. The physicsless panels just fly off and drag is increased.

This is how Squad can fix it:

1. Fairing mass is real and added to the base. To compensate, bases have a lower flat mass

2. Ejected fairings remove their weight and a little more (explosive bolts) from the base.

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Katalliaan

Katalliaan

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With that same craft, make the fairing .8t and run your tests again.

54,658m with the fairing on, 54,659m with just the base. Okay, so I was wrong and it's just the mass of the base they're adding.

Threads got merged, so there's going to be a little confusion. Check my results on page 5 of this merged thread - I found that while the fairing base is massful, the supposed weight of the panels is never added, but confirmation/refutation by independent tests is a good part of science. In your "no fairing" test, did you have "fairing base but no panels" or "no fairing parts at all"?

The second test had the fairing base but the panels ejected before launch, the third had no fairing at all. But see the other reply in this post.

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Brotoro

Brotoro

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...This is how Squad can fix it:

1. Fairing mass is real and added to the base. To compensate, bases have a lower flat mass

2. Ejected fairings remove their weight and a little more (explosive bolts) from the base.

They also have to make sure the CoM of the base-fairing is in the correct location when the fairing is in place...Not located at the base part.

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Merill

Merill

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Hi

i made a quick fix: adding the fairing mass to the base plate.

link: https://kerbalstuff.com/mod/725/Fairing%20With%20Mass

The Com is not at the right place in the vab, but it's okay in flight scene.

Edit: The problem is from IPartMassModifier, which modified the mass only on the vab. And ModuleProceduralFairing use this ?broken? interface.

source: http://forum.kerbalspaceprogram.com/threads/103152-What-s-new-in-0-90

Edit2: The Com is shifted in the flight scene with v1.1

Edited by Merill
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Sandworm

Sandworm

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there is also somthing strage about the dragmodel.

Launching a satelite with a nosecone on top is worse than launching it with a small antenna sticking out on the top.

It's the half-baked occlusion model. In short: It computes a drag value based on the top and bottom parts of the stack. Stuff in the middle sees virtually no drag during 0 AOA. Not the shape. Not the profile. Put a tiny thing atop a large thing and the large thing will be shielded. So the tiny antenna is a better nosecone than any actual cone. Also, single or two-part stacks see massively more drag than three-parters. So long tanks = lots of drag, whereas piles of tiny tank = virtually no drag.

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