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

[Shad0wCatcher]

@Traches looks like your fins are too small for the size of the rocket you're flying. Can't tell from how far zoomed out it is as to the size of the rocket body compared to the control surfaces.

@thylordroot You have to make sure you aren't running too much TWR as going too fast will cause a ton of drag on top of your vessel. My rule of thumb for surface TWR is 1.2-1.6 at launch and no more than an ending TWR of 3. Anything faster and you'll cause too much drag loss. Anything less and you're losing too much to atmospheric drag to be decently efficient. Also make sure you start your gravity turn very early (anywhere from just past the tower with shuttle analogues up to 691 meters if I'm using MJ for ascent). Also make sure your center of lift is well below center of mass to give you a solid amount of stability. Also if you know your upper stage will be inherently unstable (due to wide fairings producing a large amount of drag; use your first stage that has control surfaces to loft the rest of the rocket higher; see below for further information on that)

As an example: My typical two-stage to low kerbin orbit puts a payload in position to circularize on its own anywhere from 75-100 kM. I'll go over TWRs and D/V totals shortly. This should give an idea as to what I look for when I'm building rockets. First stage is around 1800-2500 D/V depending on payload size / mass etc. My typical burn time for the first stage without boosters is anywhere from 2:15 (two minutes 15 seconds) to 2:30. With SRBs mounted the burn time stays the same for the main engine; but the SRBs can vary wildly; I just look to end them with the main stage TWR above 1.2. My OCD dictates that they be a nice number but that is just for orderly purposes and has no bearing on functionality.

My upper stage starts off anywhere from 1.00 to 1.4 TWR; I sometimes run less depending on my flight profile.

If I run a more vertical ascent I can more easily get away with a sub 1.0 TWR and still get into orbit so long as my apoapsis is high enough to get above 1.0 TWR before reaching it; that's more based on experience and I'm sure there's mathematical formula to allow prediction of that; I just fly by the seat of my pants in that regard.

Upper stage due to DRE and FAR typically starts off between 20-30 kM depending on ascent profile and takes the craft to my final apoapsis.

If I run a three stage engine the first stage can go as low as 1500 D/V; I'm looking to loft the rest of the craft far enough away from the space center that when I decouple the first stage it lands in ocean east of KSP. The second stage pushes it out of the atmosphere and the third stage is used for circulizing and transfer.

Edited July 24, 2014 by Shad0wCatcher

[TeiwazVIE]

Repost of the "infinite glider plane"... If someone has an answer after all.

From what I've read it seems that drag in FAR is so extremely low (because it's mentioned to be accurate for Earth sized Kerbal... hwat?! ) to cause this - is there a value to adjust in some config file to get more drag?

So I'm having a "funny" issue with FAR.

It seems that I can't get my aircraft to land - it's just not losing velocity. Not even with a cut engine. Even better: doing an almost 90° cork screw seems to basically accelerate it infinitely (if it wouldn't lose structural integrity), which results also in gaining height.

I really don't think that I invented the "super plane" with just stock tiles...

That's the plane:

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

http://i.imgur.com/S9kgbyi.png

As I said, it's all basic stock parts.

Any tips? Flareing doesn't help btw.

[Entropius]

Do you have the B9 fixes installed? The engines have that NaN bug that spreads throughout the craft and breaks FARs displays.

I recall installing B9 and having to do some extra bits for a fix. I assume there was only one fix and not any more after the first one I had to do.

I had that happen as well, removing the short B9 landing gear fixed it. I'd guess something about them is confusing FAR.

I'll try seeing if that helps later tonight, but I seem to recall using small landing gear pretty frequently on other aircraft without this bug occurring.

@Ferram, had to sign up for dropbox to get my log in its entirety uploaded. Try this: https://www.dropbox.com/s/9vu7vagqhv3t95i/Player.log

[ferram4]

@thylordroot: Probably a minor asymmetry in the craft design caused by floating point errors that's compounded over time. That should be easily controllable with thrust vectoring.

@Kolago: Is your rocket stable in all the configurations it will be in while inside the atmosphere? Is it's TWR below 2?

@Maxwell Fern: There was a workaround posted a few pages ago; reading the topic before posting would have allowed it to stay closer to the top for other users like yourself that are looking for that solution.

@Entropius: Ack! What happened to the formatting it's just a wall of text?! Anyway, best I can tell is that you're running an out-of-date version of FAR; it looks like this is a bug that was fixed several versions ago.

[MainSailor]

I recall installing B9 and having to do some extra bits for a fix. I assume there was only one fix and not any more after the first one I had to do.

Realistically the only B9 fixes you need are the updated Firespitter, and updated Exsurgent Engineering (unless you replace that module in the SABRE cfgs.), and the landing gear stiffness fix. The control surface fix is unnecessary with FAR since you can adjust the control surfaces anyhow.

The quick fix to the SABREs is to change the ModuleAlternator values to 0.1 for the amount = and maxAmount = lines.

You can alternatively use HotRockets, since that cfg patches that and replaces the SABRE Hyrda controller with the stock module that controls the RAPIERS, which also gives you the ability to see DV with both modes in MechJeb or KER.

The landing gear fix is as easy as creating a new text file and adding this:

@PART[B9_Utility_Landing_Gear*]:HAS[@MODULE[FSwheel]]
{
	@MODULE[FSwheel]
	{
		@sidewaysStiffness = 0.01
	}
}

...and saving the file with a .cfg extension. Place it anywhere in GameData.

[Renegrade]

Repost of the "infinite glider plane"... If someone has an answer after all.

From what I've read it seems that drag in FAR is so extremely low (because it's mentioned to be accurate for Earth sized Kerbal... hwat?! ) to cause this - is there a value to adjust in some config file to get more drag?

Drag values have fallen a fair bit since the 0.23.5 editions of FAR due to improvements and corrections in the calculations (Ferram addressed this a couple of pages ago)..but it's always had less drag than stock. Stock's drag is pretty much fake.

FAR air is equivalent to Earth air, but it thins out and ends a bit faster than on Earth because the stock atmosphere is what, 30-40% shorter than Earth's?

One thing I would recommend to land your plane (and this is what I do), is when you get close to the runway, perform a series of sharp maneuvers - those will cause your speed/energy to bleed off. Some things you can do are:

- come about in a complete 360 circle.

- dive and climb repeatedly. This is a net energy loss. Don't stall though!

- weave back and forth in a series of S-turns.

If you're more patient and have a lot of time on your hands, you can simply cut your engines several km away from the runway and let the speed bleed off naturally.

[Kolago]

@Kolago: Is your rocket stable in all the configurations it will be in while inside the atmosphere? Is it's TWR below 2?

I limit the acceleration with mechjeb to 40m/s. Rocket is perfectly stable if I don't add chutes.

[NathanKell]

So in other words you have a TWR greater than 4. That's your problem right there.

[Shad0wCatcher]

@Kolago .......40 m/s squared is 4 g's of acceleration. that's WAY TOO HIGH. Are you even watching your G meter? If it moves out of the green while you're in the lower atmosphere you're either going to flip or rip your rocket apart with aerodynamic forces.

EDIT: Ninja'd more nicely by NathanKell

[Hodo]

Drag values have fallen a fair bit since the 0.23.5 editions of FAR due to improvements and corrections in the calculations (Ferram addressed this a couple of pages ago)..but it's always had less drag than stock. Stock's drag is pretty much fake.

FAR air is equivalent to Earth air, but it thins out and ends a bit faster than on Earth because the stock atmosphere is what, 30-40% shorter than Earth's?

One thing I would recommend to land your plane (and this is what I do), is when you get close to the runway, perform a series of sharp maneuvers - those will cause your speed/energy to bleed off. Some things you can do are:

- come about in a complete 360 circle.

- dive and climb repeatedly. This is a net energy loss. Don't stall though!

- weave back and forth in a series of S-turns.

If you're more patient and have a lot of time on your hands, you can simply cut your engines several km away from the runway and let the speed bleed off naturally.

Try 1/3rd of Earths atmosphere.

[NathanKell]

Density at sea level is the same, so that should be correct. It's that Kerbin's falls off much faster. If you want to know what the Earth altitude of a Kerbin altitude is, set FAR to absolute atmosphere density, and reference that against Earth's atmospheric density in the ICAO atmosphere. Here's a more-or-less right calculator. http://www.digitaldutch.com/atmoscalc/

[Kolago]

@Kolago .......40 m/s squared is 4 g's of acceleration. that's WAY TOO HIGH. Are you even watching your G meter? If it moves out of the green while you're in the lower atmosphere you're either going to flip or rip your rocket apart with aerodynamic forces.

EDIT: Ninja'd more nicely by NathanKell

I don't get it! Why is adding chutes a big problem. I go 40 m/s without the chutes and my rocket is fine.

Edited July 24, 2014 by Kolago

[Roaken Corporation]

You can also set your cannards to act as spoilers, tilt back while holding the breaks and you bleed speed a lot faster, also allows you to approach the runway at much better angles of attack.

Some retroboosters also help when close to the runway, to avoid bouncing off.

Here is a landing example, not the best ever but very short:http://youtu.be/M9JwkQuBrWI?t=4m38s

The video is from KSP 0.23.5 but its an example.

Edited July 24, 2014 by Roaken Corporation

[TeiwazVIE]

One thing I would recommend to land your plane (and this is what I do), is when you get close to the runway, perform a series of sharp maneuvers - those will cause your speed/energy to bleed off. Some things you can do are:

- come about in a complete 360 circle.

- dive and climb repeatedly. This is a net energy loss. Don't stall though!

- weave back and forth in a series of S-turns.

If you're more patient and have a lot of time on your hands, you can simply cut your engines several km away from the runway and let the speed bleed off naturally.

That's what I meant with "cork screws" - the 360° turns. Also S-turns or climb-dive maneuvers actually increase my velocity instead of - what I would assume - bleed it off. I tend to think of myself as someone who does know quite a bit about aevionics, aerodynamics and/or flight sims, but nothing that usually should work seems to work with this plane and FAR. Maybe I still have to get used to it as I did have to "realistic" gravity turns so my once fine rockets don't break themselves during a maneuver - but making a 50km+ approach with that little plane to maybe get it to land just doesn't feel right (but yes, that COULD work). Maybe I'm a bit harsh here but I see the error more on the side of FAR... Don't get me wrong, I don't want to blame anyone for doing a bad job (I'm a SW developer myself and know that sometimes tweaking can be a pain in the ass). The contrary. FAR is great, but in this case it's just super strange behaviour - and a mod as great as this one IMO should be...well...super awesome and not just awesome

[ferram4]

@Kolago: Then that sounds like the chute is producing more drag than it should. In that case, it's outside my control as I ignore all the drag added (in any form) by RealChute.

In any case, 4 gs is going to be a problem no matter the configuration. You should probably get rid of half the engines to start with, and then remove a few more.

[softweir]

Also S-turns or climb-dive maneuvers actually increase my velocity instead of - what I would assume - bleed it off.

Maybe you lost altitude during the turns? If you lose any altitude during braking manoeuvres then that will put airspeed right back on - but you will end up slower than if you just lost the altitude.

[ferram4]

Part of me wonders if the ModuleManager tweaks were applied properly.

@TeiwazVIE: When you right-click on the control surfaces, do you have the option to set them to be flaps or spoilers? If you don't, you have installed FAR / ModuleManager incorrectly and that is the source of your issues.

[Atrius129]

It looks like this new 0.24.1 just broke my FAR. I'm sure there will be a lot of these posts very soon.

I went to fly my new spaceplane on one of those pickup missions, and it dolphintailed out of control. repeatedly. Pretty funny... the first few times.

[ferram4]

So version 0.14.1 is out, fixing some issues, 0.24.1 compatibility, and tweaking the air-breathers down a bit, thanks to Renegrade, so blame him if you don't like it.

[ABZB]

the Update is working so far - one problem, the ferram toolbar button is duplicating itself like the KIDS did.

[ferram4]

I can't replicate the behavior you describe; post a full copy of your output_log.txt.

[TeiwazVIE]

Maybe you lost altitude during the turns? If you lose any altitude during braking manoeuvres then that will put airspeed right back on - but you will end up slower than if you just lost the altitude.

Nope, didn't do it. Lose 500m, gain enough speed to get on a stable +800m glide. That's how it works for me basically...

Part of me wonders if the ModuleManager tweaks were applied properly.

@TeiwazVIE: When you right-click on the control surfaces, do you have the option to set them to be flaps or spoilers? If you don't, you have installed FAR / ModuleManager incorrectly and that is the source of your issues.

Hmmmm...no, I have pitch, yaw & roll for my controls. But as I said, it's all stock tiles - so maybe it's because of that? I don't have air brakes or something unlocked in my tech tree. If I had air brakes I guess I wouldn't have that problem. I don't know how I could have installed FAR or the module manager wrong? As it seems to me the ModuleManager is just a DLL that's supposed to go into a certain folder (GameData I think?). All I can say is that I have a ModuleManager.dll 2.2.0 in my GameData folder. Maybe that helps figure out what the issue might be?

[ferram4]

If you right-clicked the stock control surfaces and didn't see anything in the editor, then somehow the stock control surface behavior has been removed, but FAR's isn't being added. In any case, output_log.txt please.

[TeiwazVIE]

If you right-clicked the stock control surfaces and didn't see anything in the editor, then somehow the stock control surface behavior has been removed, but FAR's isn't being added. In any case, output_log.txt please.

As I said, I can set pitch, roll & yaw, but nothing else.

@output_log.txt - ok, that thing got 16.9 MB and I really don't want to post the whole thing here Can you specifiy somehow what you'll need? Lines from to or something else (everything wit Ferram or so)?

Btw. I can definitely tell that FAR works (at least somehow) - cause my "got that sucker into orbit before" rockets "suddenly" break at previously working standard gravity turns (read: reach 10k height, turn 45°).

Edited July 25, 2014 by TeiwazVIE

[ferram4]

I need the whole thing in order to know what happened before everything started to break and how the breaking occurred. There's a reason I specified the whole thing, and it's not because I like downloading huge files.

Just because the rest of FAR works doesn't mean the wings work, since they run on different code.