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

[BLUESHADOW125]

when ever i use far with the pre made b9 planes, i get horrendous lag when it starts to show mach effects. does any1 know what this is caused by?

[cantab]

Regarding Shuttle re-entries, keep in mind what the real Shuttle did: https://en.wikipedia.org/wiki/Space_Shuttle#Re-entry_and_landing In particular, they banked it over steeply so that the lift would push the Shuttle sideways rather than upwards.

when ever i use far with the pre made b9 planes, i get horrendous lag when it starts to show mach effects. does any1 know what this is caused by?

In my experience it's the visual effects taxing a weak graphics card. Seems to affect some KSP versions more than others. Try turning re-entry effects down to minimal.

[Kobymaru]

Uhh.. where's your vertical stabiliser? Ya know, the thing that stops yawing..

@Kobymaru: Well, yes. All the problems you're having are a symptom of lacking a vertical tail. That is why most planes have a vertical tail: because when they don't, they run into the issues you're having. Add a vertical tail, all this behavior is exactly as expected for a vehicle of that design.

Just in case anyone cares: I traced back the issue, and it had nothing to do with a tail fin.

The problem was the way the control surfaces were attached to the wing.

- The wrong way: Attach them with no-angle snap to the rear edge of the wing and rotate them to fit

- The right way: Attach them with angle snap to the surface (top) of the wing, then move them towards the edge (but keep the attachment point on the top surface)

[ferram4]

... you were complaining about rolling and yaw instabilities, which are both caused by lack of a vertical tail. While I suppose you've got enough magic "reaction" wheel torque to substitute for a vertical tail, that is still the main issue. Not control surfaces.

[Matrix Aran]

Out of random curiosity, I've been having some issues with stall recovery today. Does anyone have any advice for how to design crafts to resist or better recover from flat spins? From what I can tell, once it goes into the spin, the vertical tail stays stalled and even once the craft slows to 100m/s, the nose can be hard to get back under control again. Any general advise would be appreciated.

[tetryds]

Out of random curiosity, I've been having some issues with stall recovery today. Does anyone have any advice for how to design crafts to resist or better recover from flat spins? From what I can tell, once it goes into the spin, the vertical tail stays stalled and even once the craft slows to 100m/s, the nose can be hard to get back under control again. Any general advise would be appreciated.

Try decreasing the dihedral effect on your vessel.

To avoid flatspins you can give it a bit of anhedral angle, put the wing lower, decrease swept angle or... add 2x more tail.

Edit: a pic would also be welcome.

Edited December 21, 2014 by tetryds

[Matrix Aran]

@tetryds: I've tried doubling the tail but that's not been that productive. I did add a very slight amount of dihedral to prevent some roll instabilities, so I'm guessing I've just neglected to lower the wing enough. In any case thank you very much for the advise.

@Tic-Tac: Its technically not cheating using drogue chutes if you imagine them as trailing ballutes. Its a proposed method for aerocapture, and you could probably apply it to re-entry. I have used parachutes in the past, or rather a set of RealChutes set to open at 60km. Even with DRE, they never cooked, but they were the kevlar sort.

I have noticed with the latest FAR build that drag at high altitudes on most of my old space planes seems to have increased, so you may want to pitch your craft aggressively at about 60km (assuming the craft has the control authority to do so) and use the thin atmosphere to help kill some of your velocity early before you get down below 45km. The new drag effects are so effective I managed (much to my surprise) to return from a trip around the Mun in one pass, and nearly ran out of fuel trying to stay at 30km until I got around to KSC.

[ferram4]

The trick to stall recover is to ensure that the forward-most lifting surfaces stall before the rearmost. The way to do that is to set up the forward-most surfaces to have less sweep and a higher AR than the rearmost surfaces. Also, lots of vertical tail + rudder to making getting out of spins possible.

[Matrix Aran]

Would this plane have too little tail for a low speed flat spin? Or is it a case of them being too close to the main lifting wing?

[Fabri91]

I have a question regarding the new drag model: my SSTO that was able to bring 6 kerbals or a small sat in low orbit is now unable to do so. Can this be due to the introduced changes?

Edited December 21, 2014 by Fabri91

[Empiro]

Most likely so -- how much speed are you getting before having to switch over to rocket engines? I'm definitely having trouble getting more than 1250 m/s these days on jets, most likely due to the new drag mode. Even a bit more drag leads to less speed, which leads to less intake air, which leads lower throttle, which leads to even less speed, and so on.

This means that you'll need about 1600 m/s on rocket engines to make orbit, instead of the 1200 or so from before.

[tetryds]

Would this plane have too little tail for a low speed flat spin? Or is it a case of them being too close to the main lifting wing?

http://cloud-4.steampowered.com/ugc/40862204389870247/8261F481AAAD4DD99B3C6EC45FED0A67DC0AB298/

that is not a problem.

But even though they are very long they are not too wide,

Try adding one Type A/B right in front, clipping a bit on it, will look good.

You can also move these stabilizers a bit further back and angle them inwards a bit.

Your wings are highly swept, use the vertical stabilizer angle to compensate for your roll issues and angle those wings a bit less (also lower them a bit).

Your plane looks promissing.

[Matrix Aran]

Yes, I tried lowering the wings and that resolved a fair deal of the issues. I'll give the stabilizers some angle and see how that helps.

[Kobymaru]

... you were complaining about rolling and yaw instabilities, which are both caused by lack of a vertical tail. While I suppose you've got enough magic "reaction" wheel torque to substitute for a vertical tail, that is still the main issue. Not control surfaces.

Please compare the following two crafts:

https://www.dropbox.com/s/gxx9pq7ufo274q3/Flaps-Right.craft

https://www.dropbox.com/s/i9e1omjpu7awm9d/Flaps-Wrong.craft

They are visually identical and both have a Vertical tail.

The first one flies just fine. It has its Flaps attached on the top surface of the wing.

The second one yaws slightly to the left and rolls strongly to the right once airborne. It has its flaps attached at the rear edge of the wings.

Edited December 22, 2014 by Kobymaru

[Rebelgamer]

Suborbital hops seem worse than coming back from orbit, your going to have to flatten your trajectory out so you have more time to bleed off velocity. If your using DRE, another trick is to put the 1.5m heatshield on the 1 man capsule, and remove the ablative material from the capsule. Only downside is if you come in too steep, it flattens your kerbals...

[Wanderfound]

Out of random curiosity, I've been having some issues with stall recovery today. Does anyone have any advice for how to design crafts to resist or better recover from flat spins? From what I can tell, once it goes into the spin, the vertical tail stays stalled and even once the craft slows to 100m/s, the nose can be hard to get back under control again. Any general advise would be appreciated.

For the brute-force option: Vernors. Stick a couple either side of the nose and tail, and keep 'em turned off until you need them.

[ferram4]

@Kobymaru: First, you linked a picture that shows a plane lacking a vertical tail. When you do that, people are going to explain the problems with the most noticeable error in the design that you've shown.

Second, error is not on my end, it is due to action groups not being set properly. The flaps do not deflect evenly; don't complain to me about Squad not fixing that ancient Action Group bug.

@Fabri91: Maybe? Probably not unless you were just barely able to achieve orbit before, drag has not increased that significantly. If it _has_ increased that significantly, then you need to do a manual reinstall with a new download.

[Jovus]

Out of random curiosity, I've been having some issues with stall recovery today. Does anyone have any advice for how to design crafts to resist or better recover from flat spins? From what I can tell, once it goes into the spin, the vertical tail stays stalled and even once the craft slows to 100m/s, the nose can be hard to get back under control again. Any general advise would be appreciated.

Once you're in a flat spin or a stall, the best thing you can do is to open the throttle all the way up (assuming that asymmetric thrust isn't a contributing problem) and shove the nose into a dive. Get the plane back under control, and then pull up. Yes, if you don't have enough ground underneath you, you're screwed.

(I know you asked for design advice, but I thought piloting advice might also be helpful.)

[Matrix Aran]

For the brute-force option: Vernors. Stick a couple either side of the nose and tail, and keep 'em turned off until you need them.

Always an option but one I'd rather not resort to, Vernors utterly kill fuel reserves, even with just a few. For such a tiny engine their ISP is terrible.

Once you're in a flat spin or a stall, the best thing you can do is to open the throttle all the way up (assuming that asymmetric thrust isn't a contributing problem) and shove the nose into a dive. Get the plane back under control, and then pull up. Yes, if you don't have enough ground underneath you, you're screwed.

(I know you asked for design advice, but I thought piloting advice might also be helpful.)

Generally what you suggest helps on other designs, but with the particular plane above, once it gets into a flat spin, it's next to impossible to recover from. No matter how much tail I shove on it, it will refuse to stop spinning around the yaw axis until about 1km, by that point its usually too late.

Its a bit of a new design for me, usually I stick to flat delta shapes and they've tended to be easier to recover from. This is the first plane in months that I've decided to experiment with swept wing shapes, so its a bit of unfamiliar territory.

[cantab]

You may also find shifting weight forward helps. Very easy in KSP is you have more than one fuel tank (and have unlocked fuel transfer in career).

And there's always popping a parachute. That's one thing done with real experimental aircraft when testing their spin behaviour.

[Fabri91]

@Ferram4: yes, my previous SSTOs were only able to achieve low orbit without much of a margin.

Most likely so -- how much speed are you getting before having to switch over to rocket engines? I'm definitely having trouble getting more than 1250 m/s these days on jets, most likely due to the new drag mode. Even a bit more drag leads to less speed, which leads to less intake air, which leads lower throttle, which leads to even less speed, and so on.

This means that you'll need about 1600 m/s on rocket engines to make orbit, instead of the 1200 or so from before.

I'm able to reach 1400 m/s in airbreathing mode, 1440 tops.

[Matrix Aran]

1400m/s is quite generous all things considered. Most of my heavy lift designs hardly make it to 1200 m/s before they die off in 0.14.5.1 unless I make some rather extreme efforts at airhogging. Not that I'm complaining. The drag may be a pain to get things to orbit, but it does make re-entry much less painful than it used to be.

[whynot]

Can someone explain what the AoA % slider actually do? This one here:

[kcs123]

Can someone explain what the AoA % slider actually do? This one here:

http://i.imgur.com/VyhgD6W.png

Put whole wing on some slight angle (forward/backward axis). Put AoA slider on 200% and give more Ctrl Dflct. Now use FAR graph to perform some analysis.

After that control surfaces shold be shifted in desired direction based on positive or negative AoA and should be visible in SPH.

I think that this should best explain what it does then write thousen of words.

This thing can help a lot to fine tune controls, making craft less wooble if used properly and influence to adjustment of Cm (pitching moment on FAR graph, not center of mass).

[Kolago]

I have a problem with cockpits that have "ModuleResourceIntake" in the config, if I "Revert to Launch" my rocket disappears, only the cockpit is visible surrounded by airspeed graphics. Is this a MM collision with FerramAerospaceResearch.cfg ModuleResourceIntake Code?

MkIVFAR.cfg:

// Mark IV System FAR/NEAR Support
// Requires ModuleManager and FAR or NEAR to function
@PART[mk4cockpit]:NEEDS[FerramAerospaceResearch|NEAR]
{
	@maximum_drag = 0
	@minimum_drag = 0
	@angularDrag = 0
	!MODULE[ModuleLiftingSurface] {}
	@MODULE[ModuleResourceIntake]
	{
		@area = 0.01
	}
}

mk4cockpit.cfg:

// Mark IV System 1.1
// Inline Cockpit
PART
{
	// --- general parameters ---
	name = mk4cockpit
	module =  Part
	author = Chris Adderley

	// --- asset parameters ---
	mesh = mk4cockpit.mu
	rescaleFactor = 1.0

	// --- node definitions ---
	// definition format is Position X, Position Y, Position Z, Up X, Up Y, Up Z
	node_stack_bottom = 0.0, -1.655971, 0.00, 0.0, 1.0, 0.0, 3
	node_stack_top = 0.0, 3.351745, 0.1550713, 0.0, 1.0, 0.0, 1

	// --- editor parameters ---
	TechRequired = largeControl
	entryCost = 10200
	cost = 7600
	category = Pods
	subcategory = 0
	title = Mark IV Cockpit
	manufacturer = K.V Roe and Company
	description = The star of the Mark IV line, the aptly named cockpit allows four kerbals to travel the globe in style. With the purchase of a pressurization kit (25,000 funds per unit), it could even travel to space! Includes moderately effective air intakes.

	// attachment rules: stack, srfAttach, allowStack, allowSrfAttach, allowCollision
	attachRules = 1,0,1,1,0

	// --- standard part parameters ---
	mass = 5.5
	dragModelType = default
	maximum_drag = 0.40
	minimum_drag = 0.40
	angularDrag = 4
	crashTolerance = 150
	breakingForce = 300
	breakingTorque = 300
	maxTemp = 3400

	vesselType = Ship

	// --- internal setup ---
	CrewCapacity = 4
	INTERNAL
	{
		name = mk4cockpitIVA
	}

	MODULE
	{
		name = ModuleCommand
		minimumCrew = 1
	}

	RESOURCE
	{
		name = ElectricCharge
		amount = 325
		maxAmount = 325
	}
	RESOURCE
	{
		name = MonoPropellant
		amount = 80
		maxAmount = 80
	}
	MODULE
	{
		name = ModuleSAS
	}

	MODULE
	{
		name = ModuleReactionWheel
		actionGUIName = Toggle RW

		PitchTorque = 20
		YawTorque = 20
		RollTorque = 20

		RESOURCE
		{
			name = ElectricCharge
			rate = 3.5
		}
	}
	MODULE
	{
		name = ModuleScienceExperiment	

		experimentID = crewReport

		experimentActionName = Crew Report
		resetActionName = Discard Crew Report
		reviewActionName = Review Report

		useStaging = False	
		useActionGroups = True
		hideUIwhenUnavailable = True	
		rerunnable = True

		xmitDataScalar = 1.0
	}
	MODULE
	{
		name = ModuleScienceContainer

		reviewActionName = Review Stored Data
		storeActionName = Store Experiments
		evaOnlyStorage = True
		storageRange = 1.6
	}

	MODULE
	{
		name = ModuleLiftingSurface
		deflectionLiftCoeff = 2.3
		dragAtMaxAoA = 0.1
		dragAtMinAoA = 0.05
	}
	MODULE
	{
		name = ModuleAnimateGeneric
		animationName = Mk4Cockpit-Windows
		startEventGUIName = Lights On
		endEventGUIName = Lights Off
	}

	MODULE
	{
	  name = ModuleResourceIntake
	  resourceName = IntakeAir
	  checkForOxygen = true
	  // area = intended_area / (mass/0.01)
	  //550
	  area = 0.0000181
	  //unitScalar = 0.2 * sqroot(mass/0.01)
	  unitScalar = 4.69
	  //maxIntakeSpeed = 100 * (unitScalar + sqroot(mass / 0.01)) / (unitScalar + 1)
	  // 100* (28.12)/(4.69)
	  maxIntakeSpeed = 599
	  intakeSpeed = 10
	  intakeTransformName = Intake  
	}

	RESOURCE
	{
		name = IntakeAir
		amount = 0.8
		maxAmount = 1.6
	}

}

FerramAerospaceResearch.cfg

@PART[*]:HAS[@MODULE[ModuleResourceIntake]&!MODULE[FARBasicDragModel]&!MODULE[FARWingAerodynamicModel]&!MODULE[FARControllableSurface]]:FOR[FerramAerospaceResearch]
{
	@MODULE[ModuleResourceIntake]
	{
		useDynamicDrag = false
	}

	@maximum_drag = 0
	@minimum_drag = 0
	@angularDrag = 0
	@dragCoeff = 0
	@deflectionLiftCoeff = 0
MODULE
{
	name = FARBasicDragModel
	S = #$../MODULE[ModuleResourceIntake]/area$ //1.58859927382939 per 0.01 intake area
	@S *= 158.859927382939
	cosAngleCutoff = -0.877545339888915
	majorMinorAxisRatio = 0.999999692164099
	taperCrossSectionAreaRatio = 0.546403296718528
	ignoreAnim = False
	CdCurve
	{
		key = -1 0.035 0.1849239 0.1849239
		key = 0 0.3819719 0 0
		key = 1 0.035 -0.1849239 -0.1849239
	}
	ClPotentialCurve
	{
		key = -1 0 0.5464033 0
		key = -0.866 0.4098325 5.790329 5.790329
		key = 0 0 -0.4732477 -0.4732477
		key = 0.866 0.4098325 0 0
		key = 1 0 0.5464033 0.5464033
	}
	ClViscousCurve
	{
		key = -1 0 -0.7076027 -0.7076027
		key = -0.95 -0.03538014 -0.6355354 -0.6355354
		key = -0.866 -0.08271147 -0.3644226 -0.3644226
		key = -0.5 -0.1432395 0.06055094 0.06055094
		key = 0 0 0.2864789 0.2864789
		key = 0.5 0.1432395 0.06055094 0.06055094
		key = 0.866 0.08271147 -0.3644226 -0.3644226
		key = 0.95 0.03538014 -0.5634682 -0.5634682
		key = 1 0 0 0
	}
	CmCurve
	{
		key = -1 -0.04871378 -0.09742755 -0.09742755
		key = -0.5 -0.09742755 -0.09742756 -0.09742756
		key = 0 -0.1461413 0 0
		key = 0.5 -0.09742755 0.09742756 0.09742756
		key = 1 -0.04871378 0.09742755 0.09742755
	}
}

}

Edited December 22, 2014 by Kolago