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

[RoboRay]

How can something that's supposed to work via "just copy mod to directory" have improper installations?

If you peruse the various mod threads, you'll find people that have difficulty with "copy this folder to that location" in every... single... one... of them.

It's so sadly common that "improper installation" is always among the first issues suggested when people have "unique" problems that don't seem to affect other people, for any mod.

Edited July 31, 2014 by RoboRay

[tetryds]

@TeiwazVIE: post a screenshot of your plane.

TurboJets are super powerful, and heavier, most designs won't welcome them as a straight replacement.

About being unplayable with stock, it's super playable, and the parts "limitation" is a fun challenge.

[TeiwazVIE]

Either you're using mod wing parts that aren't FAR-compatible (in which case, you should mention which ones and then go talk to the mod author about adding compatibility), or you did mess up "copy the mod to directory" step. People have, in the most amazing ways possible.

That I very much believe. And I'm not saying that that didn't happen 100%, but I'm 99,99999...% sure it didn't ;-)

For the differences between those designs, it sounds a lot like the turbojet shifts the mass around enough to make it unstable in yaw. Considering how short a plane you're talking about, that wouldn't surprise me, since you'd have almost no yaw stability with the tail on that, since it won't be far behind the CoM.

As long as relatives are kept nothing should change IMO. Sure, take off might take longer due to more mass, but based on relatives it has to be the same. I'm aware that more thrust should result in different handling. Still, I tested longer designs too. CoM being ~middleish, CoL (using even 2 fins, which should stabilise yaw movement) being almost near CoT - plane has irritating yaw movement.

Post a copy of your output_log.txt if you think it's caused by a bug.

Already did that on the infinite glide design and you didn't find any errors/mod conflicts. As nothing has changed since then, I don't see the benefit of reposting it. I'm not saying that it's a bug in the mod itself, but I think the calculations might be "wrong" (on certain occasions).

[TeiwazVIE]

@TeiwazVIE: post a screenshot of your plane.

Not exaclty the latest design (played around with CoL), but one I did save:

Maybe there's a sweet spot for CoL (or length) to make it work, but again - sorry - that's not what I would call "realistic aerodynamics". As I mentioned I also accounted for same (or at least not too much) thrust (in kN).

I seriously don't know what would be wrong with that design. But alas, I can't tell exactly for Kerbal "physics" as I don't know the exact numbers.

[edit]

Just noticed: that's the design with the jet engine. Turbojet actually moves CoL center to the edge of CoM on that design.

[/edit]

Edited July 31, 2014 by TeiwazVIE

[tetryds]

The wheels on the back are angled.

Zero that angle relative to the ground and try again.

When you change the engine you increase the weight over those angled wheels, causing it to be worse.

Just in case you don't know how to do that (you probbaly do but I took a while to figure that out when I started playing), Q/W/E/A/S/D and SHIFT+Q/W/E/A/S/D trims the part when placing.

Other tip: leave only the middle tank with fuel, that will decrease COM shift during flight.

When you replace the engine for the TurboJet you can tweak it to have almost no shift.

Edited July 31, 2014 by tetryds

[TeiwazVIE]

The wheels on the back are angled.

Zero that angle relative to the ground and try again.

Angled wheels (might) cause yaw movement on the runway? What? Seriously? I think I don't have to say that this would be very...strange...to put it in a very polite way. But ok, I'll try that. Might also try shifting/emptying fuel to move CoM more to the back. Thx for the hints.

[tetryds]

If you stop to think it's not as strange as it seems.

It's because the wheels are not perfectly at the same height.

Then, with angle, when you put them open like that each of them is trying to pull the aircraft outwards.

Any imperfection on the symetry, node position, part configuration, anything that makes the weight on one of the wheels to be even slightly bigger than on the other will cause one to have "more grip".

When that happens, they tend to make the aircraft to go unstable at takeoff.

Some designs have bigger effect than others, some go totally unstable, others have issues at landings.

So yeah, that happens.

[BudgetHedgehog]

Just an FYI, the FAR windows (neither the main one nor the Flight Data one) don't obey the F2/Hide GUI button. Ferram, pls fix?

[NathanKell]

TeiwazVIE: Get Firespitter and use the alignment guides to perfectly align your wheels. KSP has a giant honking known issue with unaligned wheels causing planes to skitter all over the runway and go boom.

But the other serious issue is that your takeoff speed is going to be insanely high because your main wheels are so far back from your COM, and even with perfectly aligned wheels, KSP *does not like* high speed on the wheels. Of course, you also have the wing loading of an F-104, so that doesn't help either, but the main fix will be to place your main wheels *right* below your AC, slightly back from the CoM. That will let you takeoff at maybe 100-120m/s? (aka 220-250 mph).

[FenrirWolf]

One thing I'm curious about is how spaceplane launch profiles should be in FAR in relation to stock. I've been messing with the best way to get my current set of planes into orbit and so far I'm finding that usually the best I can do on jets alone is getting to 28-30km at 1600-1650m/s. After that point I generally have to switch to rockets for the rest of my ascent.

Frankly that makes more sense than in stock where airhogging and other factors let you go on jets all the way into orbit, but I'm curious if my results represent the usual limit of what a FAR spaceplane can be expected to achieve or if a better design would get more mileage out of jets.

[Dangerous_Beans]

Frankly that makes more sense than in stock where airhogging and other factors let you go on jets all the way into orbit, but I'm curious if my results represent the usual limit of what a FAR spaceplane can be expected to achieve or if a better design would get more mileage out of jets.

that is about what my last one was getting on the rapiers: 30km and 1,500m/s before toggling mode.

my guess is that with FAR it depends more on your T/W with jets rather than your air-intakes. eg i had a KSP Interstellar fusion powered plane that had a T/W of around 4.5, and was able to get to Kerbin escape velocity at about 30-35km.

[BudgetHedgehog]

the best I can do on jets alone is getting to 28-30km at 1600-1650m/s.

Yup, that's pretty much what I found.. Tried airhogging, didn't work. Only got like 25 odd km high before Intake Air got so low as to cause flameouts, even on lowest thrust setting. Was pretty galling to see I still had almost 1km/s dV needed to attain orbit.. felt like I was burning for hours... still, I like a challenge! Bring it on!

[Beetlecat]

@BeetleCat: It's been there for a while. You should check the numbers in FAR Flight Data when your gear are up and down and compare.

Ah! Cheers ferram4 and all -- obviously old enough news that it didn't even register anymore.

[Motokid600]

Whats a good cruising altitude? Also how can I set trim? I see the flight assistance options, but they don't seem to do anything.. At high altitude the craft slowly pitches down due to a pair of drop tanks. But I can easily counter it... but how can I make it so that I don't have to? Is there a way to zero the controls at level?

Edited August 1, 2014 by Motokid600

[Beetlecat]

Whats a good cruising altitude? Also how can I set trim? I see the flight assistance options, but they don't seem to do anything.. At high altitude the craft slowly pitches down due to a pair of drop tanks. But I can easily counter it... but how can I make it so that I don't have to? Is there a way to zero the controls at level?

I don't believe there's a "zero" controls (in that manner) but you can alt-<input> to nudge the trim incrementally W A S D Q E. This sounds like the perfect idea for an aerospace helper mod: "Match trim to attitude" -- though SAS kinda sorta does that already.

As to your first question, that's entirely different for every aircraft.

[Renegrade]

Just an FYI, the FAR windows (neither the main one nor the Flight Data one) don't obey the F2/Hide GUI button. Ferram, pls fix?

Yeah I've had that issue too. Also I've noticed that 0.24 editions of FAR are kinda uh, "sticky" with the show/hide button (either on Blizzy's toolbar or the stock thing).

That is, sometimes clicking to show it or to remove it is ignored for the first click. Usually picks up the second one though. It didn't do this before..

Edited August 1, 2014 by Renegrade
closing quotation

[FenrirWolf]

Whats a good cruising altitude? Also how can I set trim? I see the flight assistance options, but they don't seem to do anything.. At high altitude the craft slowly pitches down due to a pair of drop tanks. But I can easily counter it... but how can I make it so that I don't have to? Is there a way to zero the controls at level?

That's what trim is. Hit ALT-S while flying to set up a downward trim. Keep hitting ALT-S if you need it to be stronger. Same goes for any of the other WASDQE controls. ALT-X resets the trim to neutral when you're done with it.

[Motokid600]

Wow, been playing over a year and I'm still learning. Lol thanks everyone.

Edit: Uhm... ALT-S nor any of the others do anything it seems. My input key does work. I use it to transfer fuel..

Edited August 1, 2014 by Motokid600

[Hodo]

One thing I'm curious about is how spaceplane launch profiles should be in FAR in relation to stock. I've been messing with the best way to get my current set of planes into orbit and so far I'm finding that usually the best I can do on jets alone is getting to 28-30km at 1600-1650m/s. After that point I generally have to switch to rockets for the rest of my ascent.

Frankly that makes more sense than in stock where airhogging and other factors let you go on jets all the way into orbit, but I'm curious if my results represent the usual limit of what a FAR spaceplane can be expected to achieve or if a better design would get more mileage out of jets.

I have built a lot of SSTO spaceplanes in FAR, and I can say that the best I have achieved is a craft that actually managed to get to mach 5.5 on air breathers alone, and then I pitched up to 25deg to climb to space from 28km. At that point I switched from jets to rockets and finished the burn. I followed the launch profile of the real Skylon, and it seems to be the most efficient.

My current most efficient craft is one that was designed messing around with the new wings in the procedural wings.

I even extended the original design slightly just to add a small 2m cargo bay.

[DaMichel]

Ferram, i swear that since the supersonic drag patch my spacecraft stall at AoA as low as 15 deg during reentry, and i'm sure that before i could put them in any orientation and they would not stall until they get much slower & lower. What is the matter with this? Or is it just my design?

Then this leads me to my second point. I tried to design a spaceplane that can reenter at high AoA (40 deg) like the space shuttle. At such AoA my crafts become unstable in yaw/roll due to stalling i guess. I tried different designs with various degree of an-or dihedral and delta and sweep wing configurations but they all have such instability in common. Do you (anybody) have tips on how to achieve better post-stall-high-AoA stability or have it not stall in the first place?

Not saying i cannot reenter at all. I have to do it very gently though. Low AoA, bleeding off speed veeeeeeery slowly ...

[tetryds]

Is there a way to zero the controls at level?

What you can do is build the aircraft so it won't require any trim at a certain speed and altitude range.

You will usually want to do that at cruise speeds or instability zones where controls sudden change and would require trimming too fast (Mach0.9~1.1).

Also, trimming is super sensible, you will want to hold it until it's where you wish.

Watch your controls on the bottom left.

[RoboRay]

Angled wheels (might) cause yaw movement on the runway? What? Seriously? I think I don't have to say that this would be very...strange...to put it in a very polite way. But ok, I'll try that.

There's no "might" about it... it's a known issue.

The reason for laterally angled landing gear causing uncommanded yaw during the takeoff roll is that the runway is not "flat" to the pull of gravity. All of the raised ground surfaces of KSC are on a perfectly parallel plane, while the rest of the ground is a sphere. Gravity pulls you toward the center of the sphere, not straight down through the plane of the runway. This is also why planes roll forward on the runway if you don't set the brakes... gravity is pulling them "downhill" toward the middle of the runway.

As to the yaw, since the plane is technically on a slight gravitational slope, dropping off to the right because the center of KSC is south of the runway, the right-side wheel has a tiny bit more weight resting on it. So, the planes tend to to turn. This "slope" also exacerbates any flexing in your craft due to its weight... parts will preferentially shift to the right, creating even more of an imbalance.

Edited August 1, 2014 by RoboRay

[SirSock]

Is there a way to tone down the mid-air unplanned rapid dis-assemblies? I find it kind of unbelievable that my plane designed to fly at thousands of meters per second can't go into a stall at any speed or altitude without bursting into pieces, even purposefully putting myself into a stall by flying really slow (just to see if I can recover) pulls the wings off almost all of my designs that have more than one part in each wing.

[Maxwell Fern]

Is there a way to tone down the mid-air unplanned rapid dis-assemblies? I find it kind of unbelievable that my plane designed to fly at thousands of meters per second can't go into a stall at any speed or altitude without bursting into pieces, even purposefully putting myself into a stall by flying really slow (just to see if I can recover) pulls the wings off almost all of my designs that have more than one part in each wing.

Sadly, even if watching my planes torn into pieces is a lot of fun, I have to agree with you. A little tone-down would be appreciated.

[Master Tao]

SirSock, Maxwell Fern,

Open the FAR window from the Space Center view. You can modify the maximum stress for several classes of parts in Aerodynamic Failure, or completely disable them in Debug Options.