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

[ferram4]

@cardgame: That could simply be the result of overspeeding; post a video soon, it should be helpful.

My response to the other problem is fairly snarky: So when you decide to break physics you end up with behavior that breaks physics? The fact is that when you start engaging in serious part clipping the FAR code (which makes the assumption that you aren't clipping parts) can get fairly messed up. Also, the control surfaces shouldn't be activating by themselves; it's possible that you left one of the autopilots on and that it did something unexpected during take-off.

@Camacha: That looks good, though hopefully the latest release of FAR should remove the need to do that.

@Van Disaster: Normally flap deployment causes the plane to have to be re-trimmed. This is why flaps get deployed well before the final approach to landing, so that the pilot has time to balance it. This is a normal problem in airplane design and is one of the things that needs to be accounted for in the design.

@Noc: If you mean adding lift modules like the wings have, then no, that won't work well. Instead you would be better off modifying the Cl curve for the standard drag model; most of those numbers are taken from real-world data. You might want to look at the command pods, since it includes the non-wing modules explicitly stated for those.

@xau: Known issue; will be fixed in the next release.

[Van Disaster]

I have had a little success using flaps on swept wings split between forwards & aft of what one might call the average lift axis in an attempt to balance moments, but it's hugely awkward trying to build wings like that with the stock bits - I just wondered if someone had found a nice solution already. Would FAR flaps still behave if they were only attached to lifting surfaces second-hand? like if they were attached to a mounting bracket of some sort, or a hydraulic ram?

[SalmonellaDingDong]

Is this fun or does it make things too hard?

Edited April 22, 2013 by SalmonellaDingDong

[ferram4]

@Van Disaster: They would still work, but some of the interactions might not be properly accounted for. You might not get as much lift as you wanted, for example.

@SalmonellaDingDong: Well, I think it makes things more fun, as do many other users of this mod. The increase in realism means that you can use lessons from real life aerodynamics to build your vehicles; if you build a plane that looks like a Boeing 747, it'll probably fly like a 747. There's also the fact that for a properly streamlined vehicle you can actually reach some pretty fast speeds in the lower atmosphere (like you should be able to do).

As for whether it makes things too hard there are (IMO) three attitudes on this:

1. The need to consider aerodynamics when building rockets makes it too hard; these people have rockets tumble and spin out during launch because of poor design.

2. The reduced drag due to proper aerodynamics makes it too easy to reach orbit; these people complain that they aren't losing as much delta-V to drag as they're used.

3. The need to consider aerodynamics combined with the reduced drag for streamlined vehicles adds new design constraints to launching a certain payload into orbit; whether it is harder or easier depends on the mission.

[SalmonellaDingDong]

Installed it, I love it!

I'm having issues with the FAR windows not appearing though. How do I get it to show in flight?

[ferram4]

Currently it only has the windows appear on command pods that have the FARControlSys module defined in their part.cfg. Check to make sure that the command module you're using has that defined in the part.cfg; then it should work.

[SalmonellaDingDong]

Can I add it to pods that do not have it? I'm asking because I'm looking to use it with B9.

[ferram4]

Yeah, sure. Just look at the code for the stock pods; when you installed FAR those should have been overwritten with the proper data.

[SalmonellaDingDong]

Okay, thanks!

[Amaroq]

@SalmonellaDingDong:

1. The need to consider aerodynamics when building rockets makes it too hard; these people have rockets tumble and spin out during launch because of poor design.

2. The reduced drag due to proper aerodynamics makes it too easy to reach orbit; these people complain that they aren't losing as much delta-V to drag as they're used.

3. The need to consider aerodynamics combined with the reduced drag for streamlined vehicles adds new design constraints to launching a certain payload into orbit; whether it is harder or easier depends on the mission.

Personally, I seriously love this mod. You will encounter some of the problems above, though!

Tumble

When you first experience "tumble", your intuitive feeling will be "It felt like my rocket got top heavy". In reality, it tends to be one of the following:

Gravity Turn - the primary cause of tumble, for me, is making my gravity turn too sharply. You can't just nose over sharply, or you get to a point where the lateral force from drag overcomes the ability of your aerodynamic surfaces to straighten out. However, I've also had it come up for the following reasons:

Structural Integrity - if I've built a vessel that is too tall, and has a ton of flex along it, I get myself into trouble with the entire rocket developing oscillations. This is especially true using ASAS to keep your rocket on-heading, as the vanilla ASAS system tends to "overcorrect", and doesn't understand the FAR model, so it gets into real trouble really quickly - you can get a Tacoma Narrows resonating oscillation thing going. The first place you'll want to go with this is struts and tail fins, essentially, giving yourself additional forces to keep yourself rigid and on-course.

ASAS - Some of my designs that felt "unflyable" with ASAS turned out to be as simple as "turn ASAS off and manage heading by hand," and they were really easy. If you'd rather use ASAS, I've found that the best way to integrate ASAS with FAR is by limiting its inputs. Turn off engine gimbaling for your bottom-stage launch engines. Use the FAR control panel in the VAB to limit the maximum deflection of the control surfaces -- values between 2 and 6 degrees seem to work pretty well.

Too Easy - really, the only thing I had here was the discovery that it was pretty much trivial to get a Sputnik orbit -- this is due to the reduced scale height of the atmosphere. In particular, it makes building small easier than building large.

Design Constraints - you will almost certainly want one of the Fairing mods from somewhere. Personally, I've been using the KW Rocketry ones, and have been quite happy with them.

[Camacha]

Personally, I seriously love this mod. You will encounter some of the problems above, though!

ASAS - Some of my designs that felt "unflyable" with ASAS turned out to be as simple as "turn ASAS off and manage heading by hand," and they were really easy. If you'd rather use ASAS, I've found that the best way to integrate ASAS with FAR is by limiting its inputs. Turn off engine gimbaling for your bottom-stage launch engines. Use the FAR control panel in the VAB to limit the maximum deflection of the control surfaces -- values between 2 and 6 degrees seem to work pretty well.

I personally like to fly most craft by hand; ASAS just introduces way too many unwanted oscillations and movement. Even when turning it on for a short period of time it can be a pain to correct and iron out all the movement. It is also sort of a check whether I built a decent craft; with anything that is really hard to control by hand is usually something wrong. Most craft only show some minor rotation, but that is easily corrected by hand. Limiting inputs sometimes helps a lot indeed if you do want to use ASAS; some fiddling round with what motors gimbal and which do not usually fixes a lot of problems.

That being said, I am having a problem I have not quite found the cause of. In the lower atmosphere, but after reaching some decent speed, some rockets start squirreling out on me. Most notably, when I try to correct course with W and S, the things start rolling like crazy without me ever touching Q or E. I have tested quite extensively and systematically broke down my rockets into separate parts to test, but it seems that some very basic rockets show this behavior. First I thought my somewhat odd payloads might be at fault, but that does not seem to be the case. For instance, FAR doesn't seem to like the tricoupler at all. Pretty much anything I build with that shows aforementioned behavior.

I might upload some stock rockets to illustrate the problem. I usually do get into orbit, but controlling the heading and thus inclination accurately is nearly impossible.

Design Constraints - you will almost certainly want one of the Fairing mods from somewhere. Personally, I've been using the KW Rocketry ones, and have been quite happy with them.

I use Faring Factory a lot, since I like nice, compact payloads.

Edited April 23, 2013 by Camacha

[SalmonellaDingDong]

I have determined FAR to be the cause of this:

http://www.youtube.com/watch?v=RX4bLs6H0dk&feature=player_detailpage

It spams "[Exception]:NullReferenceException: Object reference not set to an instance of an object" in the debug log.

The game is unplayable with FAR installed, how do I fix this?

Especially bad considering how much I've been enjoying using it.

Edited April 24, 2013 by SalmonellaDingDong

[Hyratel]

is there a way to get a deployable flap with an upward cut? I need this for a 'shuttle' type vehicle but I don't want to tie it to brakes for other reasons

[Van Disaster]

Hyratel - use negative angles. I've used those as large trim tabs when deploying enormous flaps.

[dlrk]

After installing FAR, KER has the wrong terminal velocity, but the right altitude. It gives me a terminal velocity of 2.239 km/s on the pad at KSC.

Edited April 24, 2013 by dlrk
wrong infoposted previously

[ferram4]

@SalmonellaDingDong: Cause it again and post a copy of the output_log.txt; you can find it in the KSP_Data folder. That will help me track down the source of the error.

@dlrk: Well, Kerbal Engineer uses the stock drag model to calculate terminal velocity; it doesn't know how to deal with FAR at all. Previous to the forum reset there was some discussion about whether setting up a system to allow FAR data to be accessible to Kerbal Engineer would be worthwhile, and the resulting conclusion was that it would result in too many dependencies and instabilities in the plugins, at least for now.

[dlrk]

Ferram,

What's the best way to find terminal velocity with FAR? Also, with FAR installed, I keep losing control of my rockets during the gravity turn at 10k. Any ideas?

[dlrk]

Also, does FAR work with KW Rocketry?

[ferram4]

It does work with KW.

I assume that you're doing the standard fly straight up 10km before pitching over to continue your ascent, right? You don't wanna do that. Instead, start pitching over when you reach ~60 m/s and just keep aiming prograde. You'll run a proper gravity turn trajectory (what you've described is not a gravity turn, look up the term if you want more info) and that will allow you to keep more control of your vehicle.

If that doesn't help I'd advise adding fins to the bottom of the rocket and /or designing your rocket so you don't have a series-staging event until you're up at about 20 - 25km; that should help it be more stable.

If you need more help, post a picture of the rocket and I should be able to help more.

[dlrk]

Ferram, thanks, I'll try your suggested method.

[aquilux]

Ferram, I posted some counterpoints to your arguments and suggestions as comments on your drag experiment mod so that I do not clutter up this thread. I would be grateful if you took the time, at your leisure, to read over my points and respond to them.

[dlrk]

I added fins to the bottom of my rocket, and it works good using the pitch over at 60 m/s method. I appreciate your help, and I do have a couple more questions.

How far should I pitch over? Is there a way to find my terminal velocity?

[dlrk]

Is there a guide to the proper pitch technique anywhere?

[SalmonellaDingDong]

Ferram, the lag only happened when there was crashed craft debris being loaded around me, just like that other guy. I wiped my output logs when I did my latest reinstall.

[Glaucus]

is there a save way to remove this?

I love it for planes, but rockets I seem to have the same issue as a lot of people and well im bored of launching the same old rocket by hand all the time.