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

[Goddess Bhavani]

If I actually recall that correctly it used to be somehow possible to have different travel limits in different directions for the control surfaces like in most real planes. Is it currently possible and was it ever really possible?

For different control surface travel per axis, I typically 'fudge' this feature by using the flaps commands. For instance in my 1936 TB-3 replica I deliberately locked the elevators in a certain trim angle by both manually rotating the control surface (like old WW2 warbirds with trim set by ground crew) and thus restricting its movement.

I may also elect to equip some aircraft with 'AoA delimiter' function by using negative flaps to boost elevator response for spin recovery, takeoff rotation or demonstration flight routines.

[4plains]

@Ferram4

Do the engines count as part of the area wave drag? It wouldn't seem right if they did because the engine would be creating a vacuum right in front of the engine nose cones? I don't know much about air flow dynamics. But I guess that higher speeds a vacuum would not be present once going supersonic. The air wouldn't be able to move fast enough to counter the sudden air pressure changes in front of the engines. I could imagine an engine stalling say a vacuum bubble was created in front of the engine too... I'm unsure if nuFAR can account for this though?

Yes at the moment intakes and engines add to the wave drag area. (Unless changed and I've missed it in the changelog) This is still like it because it would be a lot of work to code this feature and as I understand Ferram4 is currently busy squashing bugs that are still in the aero model before implementing more features. I mean look at the source code on github. I learn programming at university (2nd semester) and I'm awed.

[tetryds]

@Ferram4

Do the engines count as part of the area wave drag? It wouldn't seem right if they did because the engine would be creating a vacuum right in front of the engine nose cones? I don't know much about air flow dynamics. But I guess that higher speeds a vacuum would not be present once going supersonic. The air wouldn't be able to move fast enough to counter the sudden air pressure changes in front of the engines. I could imagine an engine stalling say a vacuum bubble was created in front of the engine too... I'm unsure if nuFAR can account for this though?

No, they don't create vacum right in front of them, and yes ducts count for area-ruling.

nuFAR does not account for it yet, but it certainly will at some point

I always play using Mach as my speed indicator, it gives a much better sense of the aircraft behavior under certain speeds, especially when going supersonic.

[blu3wolf]

IAS is Indicated air speed. In real life every speed meter on the plane show this value and for aerodynamic purpose it is the one that matters.

Well that is simply not true. Sophisticated aircraft display CAS, TAS or GS on request. In real life, affordable (ha!) planes have simple instruments which can only display IAS. Whack an EGI on the sucker and you can do it all.

[DuxDucisHodiernus]

Is this mod really better than stock?

[taniwha]

DuxDucisHodiernus: If you are after KSP's atmosphere being as realistic as its vacuum, then yes.

[Goddess Bhavani]

Is this mod really better than stock?

If you want to learn how to build craft and operate them in a close to realistic fashion, and want to have better control over craft performance in atmosphere then there is no substitute for Ferram Aerospace.

To some it makes building aircraft difficult when too much Gs are pulled or faulty engineering rip craft apart with little warning, but look beyond these initial failures, learn to build working planes off real life models without fear of the stock aero forcing you to create unrealistic modifications... And after a while you will likely not want to revert to stock ever.

FAR gives a sense of accomplishment as you can apply or learn many facets of aircraft performance and design and rewards you with high performance air and spacecraft you spent time and effort designing and fine tuning till they work in today's advanced aerodynamic knowhow.

Summary:

FAR makes things easy for the craft builder, makes planes faster and more dynamic, makes you learn about aerodynamics, so long as you respect the laws of physics. For many fantasy aircraft designs they may face terrible consequences trying to go supersonic and/or fly high Gs at low level, but follow real world contemporary or historical aircraft templates and you will be awed how great they flew and how great your own efforts as a craft builder make you feel in making your own planes fly well.

[Roxette]

Is this mod really better than stock?

KSP is a game. Depending on what you want to get out of the game, FAR and all the other mods available can make the experience better or worse for you. It can make building things that fly easier or more difficult depending on your level of understanding of aeronautics and your skill level at assembling rockets and planes. As with all the other mods available, you can try it, and if you enjoy the changes it makes to the game, keep on using it.

[Goddess Bhavani]

Also free bacon for anyone proving they can master FAR by building nice working planes.

Just kidding, no real free bacon but too late, they're all playing with FAR already!

[Amram]

Is this mod really better than stock?

Better is rather....subjective. Do you have any specific gripes about how stock does things? Little annoyances, etc?

Your first few ventures in far are likely to frustrate, expect that. Your used to stock, what stock does and doesn't do, but this isn't stock aero, its not changes to stock aero, and it doesn't work with bits of stock aero, its a total replacement. There's a rather disturbing amount that stock doesn't factor and far does, and these little things can all come together to bite you, and you will get bit a few times before it all really sinks in. Once you get the hang of it though, you just can't go back. its not that its too different, its that, well, okay, its too different.....and better -subjective.....

The biggest caution I should give you is that you don't really know how much stock ignores to protect you from complexity until those protections aren't there, and you don't take them into account while designing/piloting, and end up shearing the wings off, or stalling, two things stock makes nearly impossible to achieve but far leaves for the player to avoid. In stock, jumble parts together, check that mass is ahead of lift, and if it is, its almost certain to fly. In far? Well, notice how I mentioned designing? Yeah, you can almost certainly make just about anything fly in far, but fly well is a whole other ball game, but when you get there, its an achievement of its own. Like getting to the mun, except, local. Best of all, far provides all the tool you will need to determine that is needed to correct any issues that are occurring, but that will take a little reading and learning on your end to interpret correctly so it can be useful to you.

As to what I think makes this mod better than stock, here's my answer to that, in point form, as a reply to asking what makes far special. Perhaps it answers your question better than simply asking if far is better than stock?

To answer as asked though, if you seek accuracy and realism, to not be bubble wrapped, to have flight assists and supporting data to aide you in design and flight, then yes, FAR is beyond simply better, its amazingly so.

[Voculus]

Just kidding, no real free bacon

Not cool, man! Not cool!

[Hodo]

I am having the absolute worst luck trying to pass about 20km altitude. I have tried speeds between 1.0 and 3.5 mach, but I always run in to odd yaw forces at the transition from the middle atmosphere to the upper (Medium blue to dark blue on the altitude gage).

Here's an example of the ship I used. Included is the stability data for the altitude and airspeed that the plane suffered loss of roll control, followed by a stall and flatspin. (Sorry, can't figure out how to embed a slideshow, the embed codes were crap.)

http://imgur.com/a/CDk9D

Additionally, reading back, I saw something about sudden changes in cross section, so I stripped a plane that I had down to a fuselage, wings, and rudder, and was presented with this:

http://i1310.photobucket.com/albums/s643/Pyromaniacal13/screenshot20_zpsvshqcycl.png

I am so confused. I have read the design process information on the Github page, but it isn't helping in the slightest, as all of the numbers in the example craft are green for the failure point. What is it that I'm doing wrong? How gradual do I need to build these wings and maintain a decent ship length? What is a proper flight path and airspeed breakdown for FAR?

Javascript is disabled. View full album

How high are you going before you go into a spin? What is the AoA before you lose control?

[tetryds]

I know that it's hard to area-rule airplanes with a big tail.

But if you are going supersonic and at high altitudes, you need a very big tail, their efficiency drops with mach number and altitude.

Also, check out if you aren't going overkill on dihedral effect (Lß), the effect comes from sweep angle, wings positioning and dihedral plane angle.

[balu0]

Well that is simply not true. Sophisticated aircraft display CAS, TAS or GS on request. In real life, affordable (ha!) planes have simple instruments which can only display IAS. Whack an EGI on the sucker and you can do it all.

What I mean that only the IAS is measured from the dynamic pressure and static pressure difference by the pitot system, all other speed are computed speeds. But the computation starts from IAS .. always.1 other thing can be measured and it is ground speed by GPS. So I think I'm still right. By the way CAS is just adding a number to your IAS (correction number for instrument error) and TAS is computed from altitude and temperature. Usually there is a simple knob that you can turn on your speed indicator , turn the knob till the outside temperature aligns with your altitude and you can read your TAS from the instrument. But it is still just an IAS meter.

http://upload.wikimedia.org/wikipedia/commons/thumb/c/c9/True_airspeed_indicator.svg/2000px-True_airspeed_indicator.svg.png

Edited May 12, 2015 by balu0

[Wanderfound]

Also, check out if you aren't going overkill on dihedral effect (Lß), the effect comes from sweep angle, wings positioning and dihedral plane angle.

What would be the expected symptoms of excess Lß? I've had a couple of ships unexpectedly lose yaw and roll control on the edge of hypersonic as well, despite looking all fine on my usual analysis screens.

[blu3wolf]

What I mean that only the IAS is measured from the dynamic pressure and static pressure difference by the pitot system, all other speed are computed speeds. But the computation starts from IAS .. always.1

Then we are in complete agreement, and are arguing semantics. Incidentally, you can measure GS without GPS. Just need an INS for that.

[mikegarrison]

I know that it's hard to area-rule airplanes with a big tail.

But if you are going supersonic and at high altitudes, you need a very big tail, their efficiency drops with mach number and altitude.

Also, check out if you aren't going overkill on dihedral effect (Lß), the effect comes from sweep angle, wings positioning and dihedral plane angle.

If you are supersonic, area rule isn't especially important. Area rule is for transonic flow. Once you get away from Mach 1, there are other considerations that are more important.

- - - Updated - - -

without wind, the ground speed GS is equal to the true airspeed TAS.

The indicated airspeed IAS is roughly the TAS at sea level, but accumulates error at higher altitudes. Basically the IAS is the result of imperfect instrumentation.

The equivalent airspeed EAS is the IAS after calibration to correct the imperfections (and that makes it TAS again), and after correction for compressibility (which is where it becomes EAS).

I havent really wrapped my head around EAS properly, but the way it works (I believe) is that EAS will be significantly lower than TAS, as it gives you the effective airspeed you are travelling at, with respect to the amount of air going over the wings.

At least, thats the way it works in Falcon. Problem there is that that speed is CAS which should not have the compressibilty correction.

Im sure someone here can set us both straight with how it works in FAR

This is ... confused in the way you wrote it.

IAS is the airspeed traditionally indicated on the instruments. (Modern avionics have more options.)

If you adjust for instrumentation effects, you get Calibrated airspeed.

If you adjust CAS for compressibility, you get Equivalent airspeed.

If you adjust EAS for density (ie. altitude), you get True airspeed.

If you adjust TAS for wind, you get ground speed.

Edited May 12, 2015 by mikegarrison

[MatterBeam]

What would be the expected symptoms of excess Lß? I've had a couple of ships unexpectedly lose yaw and roll control on the edge of hypersonic as well, despite looking all fine on my usual analysis screens.

My experience is that planes that reach the upper atmosphere (exit High Dynamic pressure altitudes) and start reaching Mach 3 velocity tend to yaw right/left for no reason at all.

The SAS doesn't even compensate for this?!

I have to manually tap the A/D buttons to keep it on track.

The only solution I have found for this behaviour is to pitch the plane down, so that is flies nearly level (usually I set planes at 20 degrees from horizontal and just let it accelerate until engine thrust starts dropping under 1 and switch to rockets).

[jrandom]

My experience is that planes that reach the upper atmosphere (exit High Dynamic pressure altitudes) and start reaching Mach 3 velocity tend to yaw right/left for no reason at all.

I ran into this a few forum pages back. The culprit is lifting surfaces don't lift so much as "drag" at high-mach / high-altitude situations. You need either tall yaw surfaces to compensate (or possible anhedral wings like the XB-70, which I just started reading about on my Kindle).

Yaw surfaces too small, yaws out of control past Mach 2.5:

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Revised design that is stable at Mach 4:

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[capi3101]

My experience is that planes that reach the upper atmosphere (exit High Dynamic pressure altitudes) and start reaching Mach 3 velocity tend to yaw right/left for no reason at all.

The SAS doesn't even compensate for this?!

I have to manually tap the A/D buttons to keep it on track.

The only solution I have found for this behaviour is to pitch the plane down, so that is flies nearly level (usually I set planes at 20 degrees from horizontal and just let it accelerate until engine thrust starts dropping under 1 and switch to rockets).

I've seen that myself before; usually when it happens to me it's because I've reached the part where my plane begins its slow transformation into a rocket, and I've got the CoM too far aft. This is the region where having a sufficiently-sized fin/rudder helps matters tremendously. Granted, that was pre-1.0 FAR where I was experiencing that phenomenon and I haven't had sufficient time to play with the new FAR to see if everything still applies or not. Start with a fin with an area somewhere between 10-20% of the total main wing area and go from there; you want at least a quarter of the fin area as rudder.

Might also try dedicated SAS units - 1.5 kNm per tonne of plane stowed in a bay is what I go with (the only rule of thumb from the old soup that I used to use with pre-1.0 FAR, and I'm convinced it helped). Might suggest closer to the nose to help draw the CoM forward.

EDIT: Mostly ninja'd - same general advice, different way of putting it.

Edited May 12, 2015 by capi3101

[MatterBeam]

I ran into this a few forum pages back. The culprit is lifting surfaces don't lift so much as "drag" at high-mach / high-altitude situations. You need either tall yaw surfaces to compensate (or possible anhedral wings like the XB-70, which I just started reading about on my Kindle).

Yaw surfaces too small, yaws out of control past Mach 2.5:

http://imgur.com/a/DJcYZ

Revised design that is stable at Mach 4:

http://imgur.com/a/aRBVK

Currently have this:

I'll try different tails. Currently, it's four stock tail fins.

Edited May 12, 2015 by TruthQuark

[Hodo]

Currently have this:

http://i.imgur.com/f3xQWB1.png

http://i.imgur.com/0VyQKgP.png

I'll try different tails. Currently, it's four stock tail fins.

You may not need larger vertical stabilizers if you have them further from the CoM of the craft.

Think of the vertical stabilizers like your fingers holding a pen. If your fingers are to close to the center of the pen it is hard to pivot it left to right. If it is farther to one end or the other it gets easier to move the head of the pen around. It is all about leverage.

[B15HOP_xmen]

No, they don't create vacum right in front of them, and yes ducts count for area-ruling.

nuFAR does not account for it yet, but it certainly will at some point

I always play using Mach as my speed indicator, it gives a much better sense of the aircraft behavior under certain speeds, especially when going supersonic.

Regarding mach number: I mostly run into issues at mach 3+ . A general rule of thumb, is to make the plane stable at any altitude and any speed. In the design I posted earlier, you know I don't have thrust facing rear? I actually face 10 to 20 degrees downward. Thrust is still mostly behind centre of mass. I also don't have my centre of lift matching my centre of mass. Why? Because with larger plane designs, it's better to have the mass below centre of pressure. As a result my SSTO's tend to be far more stable. Gravity simple balances out the plane. My largest issue is that with a very good glide angle, my planes don't want to stop. Though that was pretty much fixed with air brakes. And I have managed to land my 200 tonn plane using a parachute. It stops very quickly though.

What would be the expected symptoms of excess Lß? I've had a couple of ships unexpectedly lose yaw and roll control on the edge of hypersonic as well, despite looking all fine on my usual analysis screens.

My 200 tonn SSTO actually has slightly anhedral wings. I only did this as an experiment because my wings are not procedural. The physics tries to bend them upward anyway so under lift, they flex up. It seems to work well, even though I have structural reinforcements.

Edited May 12, 2015 by B15HOP_xmen

[FourGreenFields]

Ok, ran into a bit of a bug.

Used the update from a couple of days ago, no dev version. Might have been fixed there.

The CoL isnt where it should be. I've been trying to build a BV 141 (asymmetric planes ftw!), and the CoL just loves my right wing tip.

Here how the thing looks without the cockpit:

http://steamcommunity.com/sharedfiles/filedetails/?id=441679915

The CoL does resemble the in-game CoL/CoP/Whatever. It is just that that wingtip generates LOADS of lift and mostly drag for whatever reason.

After I moved the cockpit to the front, the drag of the cockpit also went all over the place.

http://steamcommunity.com/sharedfiles/filedetails/?id=441682766

Hope it helps. As said, might have been fixed in the dev version already.

[Veskenapper]

I wanted to check if this is a proper behavior: 2.17t craft (Mk1 pod, service bay with science stuff, heat shield) dropped from ~20km (is it theoretically possible to launch rocket without fins?) While Mk16 chute is semi-deployed, around 10km the pod gained speed up to 1.3 Mach. Full deployment at 800m pulled about 14G. Is everything OK here?

Just wanted to raise this one again, as I can't see Psycho_zs having answered what might have caused it - but I just had a similar freak error last night; see screenshot.

This is just a command pod with some chutes and a heat shield attached, returning from orbit.

You'll note that I'm losing altitude at 841 m/s in this screenshot; but that's not because of too high reentry speed. Downward velocity had at the time been steadily increasing ever since the deorbit burn finished, and it kept increasing up until hitting the ground. Airbraking, in short, never happened.

What I found interesting is that the FAR readout window reports I'm going at mach 0.

I'm running 15.1 Fanno (watching for new releases like a hawk), and I always upgrade my mods by removing the old before I stick the newest version in. I have no idea what might be triggering the error either, and haven't been able to reproduce (except for by loading a quicksave before reentering a ton of times; always led to same result).

In addition to FAR, I'm using a catalog of 24 different mods, mainly just for parts, but all of them compatible with 1.0.2. MechJeb and CrossFeedEnabler are the only "non-supported" ones, and of those only the former was active while this happened.