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

[Hodo]

Ok... FAR is proving to be a challenge... but I really can't tell what is going on.

I can make small basic jet SSTOs, and small turbot jet SSTOs.

Then I try to make a large payload carrying SSTO, and for some reason between mach 1.2 to 1.4, it just pitches up, no matter how close to 0 I try to keep the AoA, no matter mow much fuel I shift forward.

I tried a complete wing redesign (from a forward and aft wing design, with the engines on the forward wing so that it would balance when tanks were empy) to make a large delta wing.... Still, No luck

violent pitch up at mach 1.4

What gives?

Do you have a picture of the craft?

Because my only guess, and that is the best you are going to get without pictures, is you have to much drag at the top of the craft.

[K3-Chris]

I quite like the new dynamic pressure stuff, but it's problematic when adding radial stuff that you have to add in such a manner even though it should have been mounted flush/inside if we had the tools to do so, like radial parachutes, JSI/ALCOR cameras etc, they got a bad habit of snapping off even though they'd never be surface attached in that manner in reality, if you want a camera on the front of a plane you mount it in such a way it's inside the fusilage and you have a piece of glass/plastic in front of it shaped like the rest of the fuselage to add no drag, but my cameras drop off on their own easily. Similarly parachutes wouldn't be mounted on the outside, they'd be inside which makes it even more frustrating when they snap off due to FAR or burn up due to DRE.

Wings also break too easily in my opinion, yeah if they were just mounted to the side like they are in KSP they'd snap like that but in reality wings aren't just glued to the side, they're a structural part of the rest of the plane as well and usually continue into the fuselage or go straight through, and real wings are reinforced to better deal with the forces involved.

The speed relative steering adjustment is a good idea to solve some of these issues but on a larger plane with already pretty weak control effect turning it on tends to lower your control to none or almost none, it feels like it's just a flat reduction of steering input range, while a more dynamic solution that monitors the plane for stress/high g forces would be better suited I think, testing a plane looking a lot like the b9 HL sized cargo plane and it doesn't have enough pitch authority with the control option on to keep flying.

And struts don't seem to make a difference? Tried the same design with no struts and again with a silly amount of max strength KW struts connecting the wings to the fuselage at 45 degrees above and bellow, wings seem to snap off at the same speed/turn speed.

Edited June 8, 2014 by K3|Chris

[softweir]

I suppose there is a case to be made for the parachutes, cameras and so on being immune.

However for wings, the "snapping off" is intended to simulate "the wings falling apart due to extreme aerodynamic stress", and no amount of strutting will fix that! The rationale is: If you tried to use wings of that sort of weight and that shape going at that sort of speed in real life, they would fail. We simply aren't used to playing in such a realistic manner, so it takes us by surprise when FAR tries to do things right.

BTW, you do know that you can disable aerodynamic failure in the FAR settings menu?

[Starwaster]

I suppose there is a case to be made for the parachutes, cameras and so on being immune.

However for wings, the "snapping off" is intended to simulate "the wings falling apart due to extreme aerodynamic stress", and no amount of strutting will fix that! The rationale is: If you tried to use wings of that sort of weight and that shape going at that sort of speed in real life, they would fail. We simply aren't used to playing in such a realistic manner, so it takes us by surprise when FAR tries to do things right.

BTW, you do know that you can disable aerodynamic failure in the FAR settings menu?

they shouldnt snap on take off.... at 100m/s or even lower

[Taverius]

they shouldnt snap on take off.... at 100m/s or even lower

G limits don't have a magical speed threshold - when an airframe is designed for 6g, its not '6g, but only when you're going less than 350km/h' You can easily pull 10g at less than that.

[Starwaster]

G limits don't have a magical speed threshold - when an airframe is designed for 6g, its not '6g, but only when you're going less than 350km/h' You can easily pull 10g at less than that.

there's no way my g forces were nearly that high, even allowing for bugged physics. it would have triggered a DREC warning about kerbals nearing their tolerances. I dont remember what it maxed at but but if wings snapped that easily in the real world, jet travel wouldn't be viable and we wouldnt have all these airlines in business.

[softweir]

So, show us a picture, that will be useful!

[Starwaster]

So, show us a picture, that will be useful!

sorry I dont have one and I wont play with tha feature enabled anymore

[K3-Chris]

G limits don't have a magical speed threshold - when an airframe is designed for 6g, its not '6g, but only when you're going less than 350km/h' You can easily pull 10g at less than that.

True, would be nice if you could set some g limit in FAR and have the DCA obey that instead of a flat control range reduction.

[Hodo]

sorry I dont have one and I wont play with tha feature enabled anymore

No offence but it sounds like you didn't know what you were doing.

Odds are you were dealing with 30,000kpa of pressure on the craft, and you attempted a 3-5g turn and it snapped the wings.

I know I have torn the wings off of more than a few test craft at subsonic speeds because I pulled to many g's with to much air pressure.

[Hodo]

Wings also break too easily in my opinion, yeah if they were just mounted to the side like they are in KSP they'd snap like that but in reality wings aren't just glued to the side, they're a structural part of the rest of the plane as well and usually continue into the fuselage or go straight through, and real wings are reinforced to better deal with the forces involved.

.

All I have to say, B9 invisible struts. They are stronger, and they actually work at keeping the wings on the aircraft as intended.

You can use them one of two ways.

Because REAL aircraft often have a wing root design that attaches the wings to the fuselage of the aircraft. It was not unheard of of WWII fighters snapping the wing root due to damage or overpressure, and none of those were supersonic.

[thorfinn]

Question 1: is the "Yaw" flight aid a turn coordinator?

Question 2: The aircraft pictured below flies reasonably well, but has a tendency to yaw into the turn when rolled. I noticed a "Lr" derivative turning slightly red sometimes, but it's not on Ferram's list (by the way, is anyone adding to the wiki?) and I'd like to know more about it. Also, if I understand the notation correctly, that should mean yaw causing roll, not the other way around; is that correct?

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Odds are you were dealing with 30 kPa of pressure on the craft, and you attempted a 3-5g turn and it snapped the wings.

This is also not very clear though: the load factor should be the only thing dictating failure. If Q is high, that means that a small AoA will suffice to give you that large load factor... (...right?)

Edited June 9, 2014 by thorfinn

[K3-Chris]

I assume the yaw is caused by the small amount of vertical surface and small rudder, that plane feels maneuverable at the cost of stability just judging from the profile of it.

[Hodo]

Question 1: is the "Yaw" flight aid a turn coordinator?

Question 2: The aircraft pictured below flies reasonably well, but has a tendency to yaw into the turn when rolled. I noticed a "Lr" derivative turning slightly red sometimes, but it's not on Ferram's list (by the way, is anyone adding to the wiki?) and I'd like to know more about it. Also, if I understand the notation correctly, that should mean yaw causing roll, not the other way around; is that correct?

Ok your craft is great, but what is the controll surfaces set at. Do you have them set to specific jobs? Like ailerons control roll, the elevators at the back inner part of the wings just handling pitch, and the canards handle just pitch and the rudder on the tail just handle yaw? Or do you have them setup doing different things?

Also your vertical stabilizer is a bit small for the craft.

[thorfinn]

Thank you: I suspected the tail was too small but I was too lazy to make a larger procedural one And the derivatives seemed good enough, in fact it handles at least sufficiently for its SSTO job even though it can certainly get better. Also, first time I've ever seen a subsonic L/D above 10 in something I built

@Hodo: the inner surfaces are pure elevators, the canards are also pitch only, and the small outer surfaces are pure ailerons.

Edit: I enlarged the tail somewhat and shrank the wings a tiny bit; got it to space again, easier than the last time (it actually tumbled quite a bit on the way up the first time ^^) and I'm now in a 100x75 orbit with 22% oxidizer left. The biggest problem left is lack of control authority around M1.7 - not Mach tuck, more like Mach freeze: after accelerating through the transonic regime there was a moment where pitch was just largely insensitive, until I got to about M2. Now I'm a bit worried about the reentry... but hey, I'm learning.

Edited June 9, 2014 by thorfinn

[Sparker]

Hello!

I remember I was reading about Buran and its amazing aerodynamics and found one interesting fact about its elevons: at some specific hypersonic speeds they started acting contrariwise. I mean, If they were applied to produce left roll, the plane would roll right, so the elevons were not used at such speeds.

I encountered the same in FAR twice, but I don't know, whether it is my design fault or it is the effet mentioned above implemented...

[diegzumillo]

I just started to play with this mod, and it's a lot of fun! There are some crazy maneuvers that I couldn't pull it off before, like making the plane "brake" and stand with nose up. Flying planes really is a lot of fun with this mod.

Overall, although the mod adds a lot of variables and complexity to the game, it's quite overpowered. My first plane with the mod got an apogee of 75 km. Let me say that again. My very first plane - not a rocket, it only had one jet engine - could, in theory, get involved in an accident with my space station. The thing was so damn fast it's a challenge not to dismantle the plane at every curve.

I've been messing with space planes a while and one of my long time goals was to make a 3-seat space plane SSTO that could land at other planets. I managed to make a 2-seat plane that could land on the mun and that was my record. Until now, that is. My second plane with this mod was a 3-seat plane with 2 rapiers and a nuclear engine, and it got to duna and back! (no landing) It didn't even have lights, landing gear, docking port, because it was a test flight to see it achieved orbit. I admit that climbing to orbit was a bumpy ride (its Lp is positive and I have no idea how to solve that).

Anyway, that's my general opinion so far. Maybe 'realistic' isn't the ideal parameter for ksp where kerbin is much smaller than earth and has a different atmosphere.

[BudgetHedgehog]

The parts are balanced for Kerbins soup atmosphere - it's a well known fact that drag is dependant on mass and mass alone. FAR makes the atmosphere actually behave like an atmosphere should, but obviously, you're still using parts that were designed to work in soup.

[thorfinn]

Doesn't FAR nerf the jet engines, though? At least the stock ones?

[K3-Chris]

Not sure if FAR modifies the stock jet engines at all, if you want less overpowered jet engines try installing Tav's pizza pack or using the B9 engines, much more realistic altitude/speed curves.

[BudgetHedgehog]

Not sure if FAR modifies the stock jet engines at all

See, I didn't think so, but inside FerramAerospaceResearch.cfg:

@PART[turboFanEngine]:FOR[FerramAerospaceResearch]
{
	@MODULE[ModuleEngines*]
	{
		@maxThrust = 200
		@velocityCurve
		{
			@key,0 = 0 0.7 0 -0.00098

			@key,1 = 140 0.63 0 0

			@key,2 = 400 0.7 0.00049 0.00049
			@key,3 = 900 1 0 0

			key = 1800 0 -0.00098 0
		}
	}
}
@PART[RAPIER]:FOR[FerramAerospaceResearch]
{
	@MODULE[ModuleEngines*]
	{
		@velocityCurve
		{
			@key,0 = 0 0.7 0 -0.00098

			@key,1 = 170 0.63 0 0

			@key,2 = 400 0.7 0.00049 0.00049
			@key,3 = 1100 1 0 0

			key = 1700 0 -0.00098 0
		}
	}
}
@PART[JetEngine]:FOR[FerramAerospaceResearch]
{
	@MODULE[ModuleEngines*]
	{
		@maxThrust = 140
		@velocityCurve
		{
			@key,0 = 0 1 0 -0.005
			@key,1 = 250 0.2 -0.001 -0.001
			@key,2 = 350 -0.005 0 0
		}
	}
}

For comparison, the stock jet engine has the following, along with 150 thrust instead of FARs 140:

velocityCurve
	{
		key = 1000 0 0 0
		key = 850 0.2 0 0
		key = 0 1 0 0
	}

Edited June 10, 2014 by ObsessedWithKSP

[thorfinn]

B9 jets are more realistic? Interesting to know, I was worried that the D30 I just used in that SSTO was too powerful actually ^^

How does AJE compare? Is it a major downgrade, or does it make things just a bit harder with normal-size Kerbin?

[Taverius]

B9 jets are more realistic?

Within the limits of what the stock engine module can do (and my limited knowledge) yeah - much like when rebalancing jets in TVPP, when doing the balance for B9 I have to work with something that really doesn't model jet engines very well at all.

As far as AJE - all the speed and altitude curves for jets in B9 and TVPP were done based on data from NASA EngineSim, and AJE is NASA EngineSim implemented as a PartModule.

[Hodo]

To

I just started to play with this mod, and it's a lot of fun! There are some crazy maneuvers that I couldn't pull it off before, like making the plane "brake" and stand with nose up. Flying planes really is a lot of fun with this mod.

Overall, although the mod adds a lot of variables and complexity to the game, it's quite overpowered. My first plane with the mod got an apogee of 75 km. Let me say that again. My very first plane - not a rocket, it only had one jet engine - could, in theory, get involved in an accident with my space station. The thing was so damn fast it's a challenge not to dismantle the plane at every curve.

I've been messing with space planes a while and one of my long time goals was to make a 3-seat space plane SSTO that could land at other planets. I managed to make a 2-seat plane that could land on the mun and that was my record. Until now, that is. My second plane with this mod was a 3-seat plane with 2 rapiers and a nuclear engine, and it got to duna and back! (no landing) It didn't even have lights, landing gear, docking port, because it was a test flight to see it achieved orbit. I admit that climbing to orbit was a bumpy ride (its Lp is positive and I have no idea how to solve that).

Anyway, that's my general opinion so far. Maybe 'realistic' isn't the ideal parameter for ksp where kerbin is much smaller than earth and has a different atmosphere.

FAR does nothing to jet engines in KSP fact is jets in KSP are overpowered. If you want to bring them more in line with real jet engines you need AJE which changes them to act like real jets. Thus killing intake spamstrosities and making ssto jets near impossible.

[Taverius]

FAR does nothing to jet engines in KSP

Not true. Check the MM file.