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[1.3.1] Ferram Aerospace Research: v0.15.9.1 "Liepmann" 4/2/18


ferram4

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Right - it seems pairs of airbrakes ( to balance up/down force ) are suffering from biplane effects ( despite their leading edges technically being the single leading edge of the wing ) and reducing lift on the entire surface. Making them thick enough to mostly completely overlap seems to help, but that also makes life horrid.

It might be a pControlSurface/pWing thing, but it does appear to be relatively new.

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Right - it seems pairs of airbrakes ( to balance up/down force ) are suffering from biplane effects ( despite their leading edges technically being the single leading edge of the wing ) and reducing lift on the entire surface. Making them thick enough to mostly completely overlap seems to help, but that also makes life horrid.

It might be a pControlSurface/pWing thing, but it does appear to be relatively new.

You could place them like on this pic: http://forum.kerbalspaceprogram.com/threads/20451-0-25-Ferram-Aerospace-Research-v0-14-3-2-10-21-14?p=1553028&viewfull=1#post1553028

It's not super efficient but you won't have those issues.

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You could place them like on this pic: http://forum.kerbalspaceprogram.com/threads/20451-0-25-Ferram-Aerospace-Research-v0-14-3-2-10-21-14?p=1553028&viewfull=1#post1553028

It's not super efficient but you won't have those issues.

Yeah, I resorted to that - makes for some interesting turning forces with them deployed. I suspect given you can reduce the effect by making the surface leading edges thick enough to overlap that it's not an intentional effect, though. I'll investigate more with stock parts.

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Yeah, I resorted to that - makes for some interesting turning forces with them deployed. I suspect given you can reduce the effect by making the surface leading edges thick enough to overlap that it's not an intentional effect, though. I'll investigate more with stock parts.

I have a pair of control surfaces setup for airbrakes mounted on the vertical stabilizers, space shuttle style. Works real well.

Edited by Alshain
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I'll give it a try, thanks.

I know the fuel consumption logic is good, because I spent hours fixing it. It drains lateral rear - lateral front - core front - core rear

The problem I am seeing with your craft is the CoM is shifting as the fuel drains. That is a classic case of the nose becoming to light.

I can tell you one way to counter this problem without a new parts mod or a crazy amount of fuel line routing. TAC Fuel Balancer, it is a life saver for SSTOs, VTOLs, and aircraft in general in FAR.

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Hodo, that is very definitely not what's happening. Not only is this just with jet engines, and therefore the fuel drain is minimal, but also I have the fuel carefully set up to drain in such a way as to increase stability.

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Hodo, that is very definitely not what's happening. Not only is this just with jet engines, and therefore the fuel drain is minimal, but also I have the fuel carefully set up to drain in such a way as to increase stability.

The other thing I can see is your CoT being below your CoM. This would cause the craft to push the nose up, and at higher altitudes the air is so thin the control surfaces dont have the force they had at lower altitudes, thus causing you to lose pitch control.

EDIT- The otherthing it could be is as MAKC said in his post. Looking at the graph it looks like that is the most likely cuprit.

Edited by Hodo
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New to FAR. Why do even my most basic rockets spin and tip nose down. I'm doing the most gentle gravity turn imaginable, I'm not even leaving the tiny circle. I'm barely getting past 5 degrees and things start rotating and nosing down. Something seems buggy here.

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New to FAR. Why do even my most basic rockets spin and tip nose down. I'm doing the most gentle gravity turn imaginable, I'm not even leaving the tiny circle. I'm barely getting past 5 degrees and things start rotating and nosing down. Something seems buggy here.

Keep your COL under your COM, add some control surfaces to the bottom of the stages that will be inside the atmosphere to ensure that.

I am using the frequently asked questions on this topic to help me puting together the basic tutorial which may answer all of them.

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Yeah, I resorted to that - makes for some interesting turning forces with them deployed. I suspect given you can reduce the effect by making the surface leading edges thick enough to overlap that it's not an intentional effect, though. I'll investigate more with stock parts.

15661035659_412160e583_z.jpg

15661034169_dab40ed94a_z.jpg

Clean KSP, FAR from GitHub yesterday - don't know if it's a thing you're bothered about Ferram but easy enough to reproduce.

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https://farm8.staticflickr.com/7531/15661035659_412160e583_z.jpg

https://farm8.staticflickr.com/7495/15661034169_dab40ed94a_z.jpg

Clean KSP, FAR from GitHub yesterday - don't know if it's a thing you're bothered about Ferram but easy enough to reproduce.

It seems that you are killing some lift from your wings.

Based on how FAR models wings I don't think this would be workaroundable that easily.

IIRC FAR takes the wings, turn them into flat planes then models it as wings internally so it doesn't matter if they should be shielded.

What I mean is that this seems to be the good old "FAR does not magically shield parts" thing.

Not sure though.

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New to FAR. Why do even my most basic rockets spin and tip nose down. I'm doing the most gentle gravity turn imaginable, I'm not even leaving the tiny circle. I'm barely getting past 5 degrees and things start rotating and nosing down. Something seems buggy here.

One other thing besides control surfaces is the amount of thrust. High TWR and acceleration can be bad as well, especially with an engine that gimbles. With a lot of acceleration, it can cause a rocket to be very unstable as well. I usually limit my rockets to 18-20m/s.

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It seems that you are killing some lift from your wings.

Based on how FAR models wings I don't think this would be workaroundable that easily.

IIRC FAR takes the wings, turn them into flat planes then models it as wings internally so it doesn't matter if they should be shielded.

What I mean is that this seems to be the good old "FAR does not magically shield parts" thing.

Not sure though.

I assumed it turned all adjoining/overlapping colliders into one as far as calculations are concerned - but I guess control surfaces are not part of that, and effectively splitting the surface like that is an awkward case.

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I assumed it turned all adjoining/overlapping colliders into one as far as calculations are concerned - but I guess control surfaces are not part of that, and effectively splitting the surface like that is an awkward case.

I think that it needs to do that because it does not model wings that move or change shape.

So if you make a wing with internal flaps and control surfaces it will not work properly.

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Hodo, that is very definitely not what's happening. Not only is this just with jet engines, and therefore the fuel drain is minimal, but also I have the fuel carefully set up to drain in such a way as to increase stability.

Using the statistics tool that comes with FAR, I've found that there is a CoL shift as you pass into the higher mach speeds, and it tends to shift forward. The easiest way to figure if this is what's getting you is have the far window open and note the absolute pressure and mach that you lose control, drop back into the SPH and plug them into the statistics tool and see what turns red, which will probably be Mw. also wouldn't hurt to put a 2HOT on it to verify the temperature for the statistics window as well.

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I'm having some problems designing a light cargo lifter spaceplane. Specifically, around 20-25km it noses up uncontrollably until it stalls out and dies, every time. Can I get some help/advice fixing this? I'm obviously doing something wrong, but I've been carefully following the work of successful spaceplane designers, so I'm not sure where my mistake is.

http://imgur.com/a/9G2mD

Those full-body delta designs are prone to nasty pitch-up problems; once they start to go, there's a lot of wing area pushing them around and no tailplane to pull them back. That's what your yellow line is telling you; as soon as it inflects up, any pitch deviation will tend to increase rather than damp out. You want that yellow line to stay sloping down until at least 20° and preferably more.

Either shift to a conventional long tail design or give it a huge amount of high-speed high-altitude pitch authority (canards and Vernors). Reducing forward wing area may help a bit, but probably not enough.

Edited by Wanderfound
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Don't know if this has been mentioned before, but the latest version causes the lift vector from the center of lift indicator to disappear. Also, when using DangIt it stops the broken parts from glowing. I have narrowed it down to FAR by uninstalling all the mods and adding one by one, then double checking and it is indeed FAR, don't know what is causing it but I thought I should mention it here.

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Don't know if this has been mentioned before, but the latest version causes the lift vector from the center of lift indicator to disappear. Also, when using DangIt it stops the broken parts from glowing. I have narrowed it down to FAR by uninstalling all the mods and adding one by one, then double checking and it is indeed FAR, don't know what is causing it but I thought I should mention it here.

The lift vector removal was deliberate.

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Using the statistics tool that comes with FAR, I've found that there is a CoL shift as you pass into the higher mach speeds, and it tends to shift forward.

Are you sure you are reading that right, and not reading the AoA display in the FAR statistics tool. You want to use the "Sweep Mach" tab not the "Sweep AoA".

The CoL should shift back at supersonic speeds.

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Those full-body delta designs are prone to nasty pitch-up problems; once they start to go, there's a lot of wing area pushing them around and no tailplane to pull them back. That's what your yellow line is telling you; as soon as it inflects up, any pitch deviation will tend to increase rather than damp out. You want that yellow line to stay sloping down until at least 20° and preferably more.

Either shift to a conventional long tail design or give it a huge amount of high-speed high-altitude pitch authority (canards and Vernors). Reducing forward wing area may help a bit, but probably not enough.

That is funny I cant say I have had those issues on any of my craft that are delta wings.

Javascript is disabled. View full album

This old F-21 of mine flew fine even in the latest versions of FAR. And it is definately a full body deltawing.

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That is funny I cant say I have had those issues on any of my craft that are delta wings.

http://imgur.com/a/iLKXN

This old F-21 of mine flew fine even in the latest versions of FAR. And it is definately a full body deltawing.

As is this one:

screenshot191_zps160264b0.jpg

You can design around the problem, sure. But when they go wrong, they often go wrong in this particular way, and it's due to the lack of tailplane and rear-biased CoM tending to give inadequate high AoA pitch stability. Which is part of why the ones that work tend to be not too excessive in wing area, and taper down the wing towards the nose.

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