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

[WeaselsInTheWalls]

I've been tinkering with a Mig-21 clone- that delta-wing is a godsend in FAR- and while it works very well overall and gets eerily similar performance to the original in a few ways I'm running into a small issue at higher altitudes and mach numbers that I'm not sure how to fix.

It wants to nose down from the start, which isn't a huge problem and can be trimmed out. But as I start going faster and higher that tendency gets so extreme I literally run out of elevator range- it's all devoted to the trim keeping the nose up long before I have problems with lift or intake air.

That's not too surprising in supersonic flight, but I'm not sure what the clean solution would be: inclining the tailplane forwards corrects that but only by giving it even worse in the opposite direction; the 5 degree minimum rotation is just too much.

http://www.flickr.com/photos/98971750@N05/9303052572/lightbox/

http://www.flickr.com/photos/98971750@N05/9300269915/lightbox/

(These are the stripped down version with the minimum of mod doodads, but none of those should alter its flying traits)

I've been experimenting with using it as a launcher for small satellites, but unfortunately the radial decoupler's force always makes the payload flip out on release and so far I'm too awful with piloting rockets to correct it quickly enough . If anyone's got tips on working round either issue I'd be glad to hear them!

[ferram4]

@asmi: I guess I can implement that; I've been thinking about redoing the GUI for awhile. Go ahead and PM the code.

@EvilNando: Set all the control surfaces you want to act as flaps to be flaps. Then switch to Action Groups and select each of those control surfaces; set the increase flap deflection and decrease flap deflection actions to the appropriate groups.

@WeaselsInTheWalls: You need to either increase the maximum deflection of the control surfaces, make the control surfaces larger or push the CoL a little bit further forward. Your basic problem is that your control surfaces just aren't powerful enough.

Also, make sure that your payload is aerodynamically stable on its own before you try to launch it; if it's unstable it'll flip out.

[ehlampley42]

I am sorry if this question has already been asked, but I have a question about something this mod is doing. As you can see in my screenshot FAR is adding the 3 new readouts. (cl, cd, cm) I have removed every other addons and confirmed that FAR is adding this. Does anybody know what these mean or if they can be disabled?

Thanks

http://imgur.com/kC5txpl

[NoMrBond]

It's just some debug values/readouts which were inadvertently left in, Ferram stated that it would be removed/fixed for the FAR release to go with the 0.21 patch.

[ehlampley42]

Thank you for the quick reply

[EvilNando]

well after two days of playing with this mod , all I have to say is that the idea is nice but I think that given the limited amount of parts that were given in ksp , this is kinda overkill

also sometimes ive experienced loss of control authority while in flight for no reason at all

in the end all Im saying is: the new dynamics are appreciated but maybe we can get a "toned down" version of it considering we are limited in the construction way of things

[camlost]

well after two days of playing with this mod , all I have to say is that the idea is nice but I think that given the limited amount of parts that were given in ksp , this is kinda overkill

also sometimes ive experienced loss of control authority while in flight for no reason at all

in the end all Im saying is: the new dynamics are appreciated but maybe we can get a "toned down" version of it considering we are limited in the construction way of things

There are a handful of good mods that support FAR

[The Lone Wolfling]

well after two days of playing with this mod , all I have to say is that the idea is nice but I think that given the limited amount of parts that were given in ksp , this is kinda overkill

also sometimes ive experienced loss of control authority while in flight for no reason at all

in the end all Im saying is: the new dynamics are appreciated but maybe we can get a "toned down" version of it considering we are limited in the construction way of things

Try procedural wings, procedural fairings, and b9. Between the three you are pretty much set. (If I were to install one - b9. 2 - pfairings + b9.)

As for loss of control, make sure you aren't stalling.

I agree that it would be nice to have a mod that only removed the infiniglide glitches without changing aerodynamics otherwise though. If nothing else, it would make some challenges a lot easier to judge. (For example: I've been wanting to do a glider challenge - mod the craft file to change launch clamps to 1km high, how far can you get, but with stock it's "trivial" to just keep going forever.)

And something vaguely related. Is it just me who is bugged by the fact that the internal gyros of command pods / SAS units seemingly have no saturation point? Real CMGs cannot simply keep trying to rotate a vessel in one direction forever.

[asmi]

I think it has to stay the way it is now. This mod is not about making game harder or easier - it's about simulating real life phenomena.

[GreeningGalaxy]

I installed FAR in my .20.0 game the other day. I absolutely love it, and I've already managed to make an SSTO which I'm slowly improving on with the goal of taking it to Duna or Eve.

I hit a problem today, though- whenever I start any kind of flight, I get about 1 FPS, which quickly drops to about 0.2 FPS. I can still technically fly, but one frame every five seconds (I timed it) does make it less than enjoyable.

I also noticed that the FAR flight UI stuff wasn't showing up.

Any ideas?

[ferram4]

You'll need to post the output_log and a list of any other mods you're using before I can help. You should check to make sure that the ModuleManager.dll plugin is the most up-to-date version and that you're not using an out-of-date version of any other mods. If you're still running 0.20.0 rather than 0.20.2 that might be part of the problem too.

[GreeningGalaxy]

The FAR UI is now showing up and I can get a plane about 100 meters down the runway before the frame rate gets unbearable. Right now I've also got ISA Mapsat installed (improperly I think, because the parts are there but they do nothing). When I have time I'll see if I can find the output_log, but now it seems like the problem might be related to the slightly older ksp version, or maybe just my flukey computer.

[Autochton]

I come to you in my hour of need again. I've an SSTO, which will complete an orbit flight profile to 100x100km just fine, hits some 1.7 km/s in the upper atmosphere before going to rockets, etc. Very happy with it... Except for one thing: It will not aerobrake. Not properly, anyway. When reentering, I assume a 35â° nose-up attitude, and wait for the atmosphere to start slowing the ship down. Instead, it pushes the nose down to a maximum of ~10â°, at full pitch up. This is low enough that the wings are lifting the ship, which means the damn thing just flies along at 40+ km altitude and ~2 km/s. It slows down extremely slowly. It will even gain altitude, depending on circumstances. As a result, I overshot my landing zone by about 100 km, had to come around and readjust and, of course, flubbed my landing - which I don't quite think can be blamed on the plane, though.

So I guess my question is, what sorts of features will help my plane keep nose-up attitude through the braking? It's has mid-hull high-mounted wings with anhedral (center of lift ~20-25% of hull height above CoM), and a rear-mounted V-shape tail, with the 'smaller' B9 stabilators for control surfaces. I can sort out some screens of it later. Can the reentry trajectory affect this, by the way? Could it be because I was reentering too steeply?

[Van Disaster]

Well... it is a plane, so really unless you add brakes it *shouldn't* aerobrake - not like a lump you launched off a rocket, anyway. You can quite easily bounce off the atmosphere, as you've found, and as you also found your tail will be trying to point your nose along your motion vector, like it's meant to do . If you want to hold a high angle of attack then you probably want a delta rather than a wing+tail combo, but you'll still skim the atmosphere anyway ( and it will also still try and pitch down ). Kerbin's rather shallow atmosphere doesn't lend itself to steep re-entry.

Solutions:

* Shallower approach - I usually retrothrust almost half an orbit ahead and put my perogee 20km over KSC, quite often don't use any throttle until finals. You can easily adjust your descent in the upper atmosphere by levelling out at various altitudes.

* Airbrakes - unfortunately FAR isn't very convenient about using action groups with airbrakes - it likes flaps to behave like flaps do. However some draggy objects near the rear of the plane ( if your air intakes are well behind your centres, open them - otherwise don't, you really don't want a forward CoDrag during re-entry ). If you don't mind holding B down forever set them as brakes, otherwise with some fiddling you can set vertical surfaces up as flaps. I don't do this unless the plane has stability issues in re-entry.

In your case I suspect your design is a bit too stable too - I usually use tail-forward designs unless they're really huge which are not particularily stable but have a fair bit of pitch authority, which has made me use fairly gentle re-entry profiles ( overspeeding and large amounts of pitch authority are not good combinations! ).

Edited July 20, 2013 by Van Disaster

[Autochton]

Van Disaster: Okay. Shallowest reentry possible next time, probably according to your recipe there. Also, I'll strap some airbrakes on the rear end of it. Hmm... Does the parking brake activate airbrakes? I'd expect it to, and if so, that would allow for static deployment, without holding B down.

Have been considering a delta setup, but I don't know, I find I like the conventional wing-and-tail design, plus I like my V-tails too much, I think. I might try that for the heavier cargo plane I'm going to build for a primary lifter.

And, of course, I'll have to be less crap about the landing!

[regex]

I'm using FAR and DE, and I'm wondering where the Kerbin atmosphere starts? I came in for an aerobraking last night at 48km and didn't so much as drop a single m/s. I then did a retro burn at AP and tried again at 25km and received the desired result.

My reentry was pretty shallow; the heat shield worked as advertised and brought me down below 2k m/s before it was finally ablated, and the pod took care of the rest. I'll have to play around more with the combination but, aside from the muddy atmosphere height, everything seems to work okay.

[ferram4]

@Autochton: The solution is to make sure that your CoL is fairly close to the CoM and to make sure to come in at a very high angle of attack so all the wings are stalled; this will allow you to maintain a high angle of attack while the wings are stalled. Make sure that you have some RCS for attitude control though. Eventually, the dynamic pressure will increase enough to push your spaceplane's nose down, but you should have bled off quite a bit of speed in the meantime.

@regex: First, make sure that the attachnode sizes for the heat shield are correct; you can find them in the part.cfg file where they will be the last number in a list of 7 numbers, indicating position, orientation and then the size of the attachnode. The last number is an integer and should be 2 for the 3-man command pod heatshield; it should be 1 for the 1-man command pod. This determines the amount of drag created by those various parts.

Second, understand that FAR's more realistic drag is much lower than the stock drag model; the atmospheres of all the planets are kept the same as they were. Kerbin's atmosphere still ends at ~70km and its atmospheric density still goes with e^{altitude/-5000m}. So to help explain what happened, the atmospheric density at 48km is 6.773 * 10^-5 times that of sea level density which means that there's pretty much no air there for you to push against; without a very large drag area you're not going to slow down too much at that altitude. With FAR, it's actually possible to stay in a 55km orbit for a bit if you really want to. Basically, you didn't account for FAR's lower drag values enough in your first aerobraking maneuver.

[regex]

Basically, you didn't account for FAR's lower drag values enough in your first aerobraking maneuver.

I haven't tried more than a handful of aerobraking maneuvers to begin with, stock or otherwise, so I can't really claim I took anything "into account". I just looked at the atmosphere heights in the wiki and gave it a try. This first time was enlightening; bring a three-man pod in at about 28~25km, let the heatshield take off any velocity above 2km/s, deploy chutes once the heating effects are gone, and the pod will make it safely to the ground.

I'm liking the mod so far. Like I said though, I need to play around with it (since I play games more by feel).

Also, I really enjoy the increased air effects. Great work!

[Van Disaster]

Sadly airbrakes don't deploy with the parking brake, so you'll have to wedge the B key down. I've personally found coming in totally stalled means I end up out of control all the way to the ground, but that's quite probably because I don't design for it...

[birrhan]

I will preface this by saying my math sucks. A lot. Also physics. Also, programming.

So I am trying to reconcile FAR with Deadly Reentry, but my problem is that the heatshield does not seem to protect anything from overheating. From a circular orbit (80 x 80 km) I lower Pe to 20-30 km (any higher and I don't decelerate out of an orbit). At 32 km, I'm going about 2300 m/s, and I make my angle of attack 5-10 degrees. Somewhere before 28 km I'm going 1900 m/s and then exploding.

I have tried futzing with the drag values, even this "fix":

http://forum.kerbalspaceprogram.com/showthread.php/32342-0-20-Deadly-Reentry-2-3-reentry-heat-plus-thermal-and-g-force-damage-to-parts?p=528694#post528694

And none of these things has an effect. I should mention that the only thing I'm attempting to land is a 3 person command pod, with 2.5 m heatshield attached. Also, every component of the ship says "isshielded: false", and no part displays temperatures. All of these things suggest a programming glitch, but since there's crossover between both mods, I don't know which. The guy in charge of DE is being quiet until 0.21 comes out, so I was hoping someone here has some ideas or experience with this issue. Specifically, what conditions make for viable reentry? I'm looking everywhere and don't see consistent numbers, and this thread is so long I'm not even sure where to begin. So let's begin here! Thanks.

[ferram4]

First, the "isShielded" flag refers to whether the part is inside a cargo bay or payload fairing, and so that is the proper value if FAR is working.

Aside from that, I suspect that Deadly Reentry is currently set up to be more compatible with stock aerodynamics than with FAR aerodynamics, which would mean that you will have a much narrower reentry window to work with. I would suggest setting your periapsis lower and trading lower heating for higher g-loads. Probably pushing periapsis down to 10km or less should work for reentry from a circular 80km orbit. Remember, the longer you stay in the upper atmosphere the more heat is absorbed by the heat shield, which will degrade it faster. You want to dive quickly to try and bleed off speed so that the heat shield survives the reentry.

[NathanKell]

Trying again--last time I posted this it didn't show up

(crossposted to the DRE thread)

First, I'm absolutely loving FAR, thank you so much! I flew a plane like...a plane, and it was a revelation. Plugged in my HOTAS setup and had a ball.

Having a few issues that I'll ask about in a later post or two, because they seem to be bugs (adding four fins changes the Cd of a rocket from 0.02 to 1.5!?) but for now, DRE integration.

I've found and fixed the problem with the heatshields and FAR. FAR applies open-node drag by first raycasting from CoM to node to find where the node is; on the 2.5m heatshield, for example, both top and bottom nodes are above CoM so there's no open bottom node, and thus very little drag (Cd of 0.05 vs 0.6 for unshielded Mk1-2 pod). If you move the node below the CoM (and move the model too, so no visual changes) then all's well--you get a Cd of like .4 or so, which makes sense for a rounder, smoother, more aerodynamic bottom.

Changes:

replace asset params and node defs with this:

// --- asset parameters ---
//mesh = model.mu
MODEL
{
	model=DeadlyReentry/Parts/deadlyReentry_2.5Heatshield/model
	position = 0.0, -0.1, 0.0
	// bnode of shield was at 0.05*1.3=0.065
	// tnode of shield was at 0.145*1.3=.1885
	scale = 1.3, 1.3, 1.3
	rotation = 0, 0, 0
}
scale = 1
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, 0.05, 0.0, 0.0, 1.0, 0.0, 2
//node_stack_top = 0.0, 0.145, 0.0, 0.0, 1.0, 0.0, 2
node_stack_bottom = 0.0, -0.035, 0.0, 0.0, 1.0, 0.0, 2
node_stack_top = 0.0, 0.0885, 0.0, 0.0, 1.0, 0.0, 2

You can do the same thing for the other shields with this issue: replace mesh= with a MODEL{} block, move the model and both nodes down by the same amount. I chose to bake in rescaleFactor because I didn't know how rescaleFactor played with MODEL{} blocks but you might be all right otherwise.

[birrhan]

negative on that approach. Same result. Again, it appears that the heatshield is nonfunctional.

Test: 83 x 2 km. retrograde orientation at 32km, v = 2050 m/s. Exploded at 29 km, speed 2000 m/s.

The cause appears to be a non-functional heatshield. How do you make the heatshield work? I know it's a DE product, but everyone's using the damned thing, and I appear to be the only one having a problem with it....

[Autochton]

The solution is to make sure that your CoL is fairly close to the CoM and to make sure to come in at a very high angle of attack so all the wings are stalled; this will allow you to maintain a high angle of attack while the wings are stalled. Make sure that you have some RCS for attitude control though. Eventually, the dynamic pressure will increase enough to push your spaceplane's nose down, but you should have bled off quite a bit of speed in the meantime.

So I'm probably looking at well over the 35â° I was using to have that work. Will have to run some sims.

Manipulating my CoM will be a trick, I think. I would have to shift fuel around different fuel tanks in order to do it... Would there be a problem, when doing this reentry, if the CoL ends up in front of the CoM for the duration of the braking maneuver, as long as I shift it forward once going to flight? Alternatively I will have to get a hold of TAC's fuel balancer mod, hope that'll sort it.

[Van Disaster]

Get TAC's mod anyway. If nothing at all is providing lift ( and that is fairly rare ) then you're attempting to balance using CoD, which unfortunately you'll have to guess. You'll also need to work out how to transition to flight with your CoL forwards, because the plane is not going to help you at all...