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

[Tsuki]

Did i read right on the last update... about FARAPI!? now I really might try to implement that glide slope prediction.....

Time to start learning more about the math of aerodynamics, @ferram4 got any good starting point literature?

[R0cketC0der]

@ferram

Could you consider adding a method that returns the coefficients for a certain orientation at a certain Mach speed? I want to try and make a aerobraking calculator.

[Maxwell Fern]

@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.

Man, with all due respect you can't expect anyone to read through 500 pages hoping they might find an answer to a simple question. Moreso, if this is a regularly asked question, maybe consider adding a tip in the OP ?

Also, I don't understand your point. How can reading the topic keep it closer to the top ? I thought posting in it was what bumps it.

[Grunf911]

@Grunf911: Seriously, you don't need that many engines. Take a more moderate ascent path, and you won't have to worry about tailstrikes like that thing will.

Hi Ferram,

Actually i tried with a single Rapier, and by the end of the runway i was going at approx 68 m/s, which was way too low for even takeoff.

On a serious note i think that although the stock rapier was indeed overpowered, this is nerfed a tad too much. in 0.24 i was barely able to take off at approx 109m/s by end of runway, while current 68 m/s in 0.24.1 just does not cut it i am afraid. I would be happy to provide you with craft if you want to test yourself. If so, pls send me your mail in PM.

I would suggest for you to check if by introducing a latest nerf to other airbreathers, you might have double-nerfed the rapier perhaps.

Alternatively, i am open to suggestions to improve my SSTO design :-)

Edited July 25, 2014 by Grunf911

[thorfinn]

@ferram

Could you consider adding a method that returns the coefficients for a certain orientation at a certain Mach speed? I want to try and make a aerobraking calculator.

You mean, a table of the coefficients you get in the SPH? Yes, that would be great....

[DaMichel]

Ferram, the cargo bay shielding appears to be fixed. Thanks you.

Man, with all due respect you can't expect anyone to read through 500 pages hoping they might find an answer to a simple question

Perhaps we should start to report issues on github. I have seen there are some reports already. It certainly makes it easier to find known issues and each issues can have its own thread.

[ferram4]

@Thorfinn: Calculation CLMax isn't exactly trivial... I'll see what I can do though. (Welp, this is what I get for adding the beginnings of an API; never do that again )

@Tsuki: Umm... wikipedia isn't too bad to start with actually. Anything I send you at is either going to be thick textbooks or technical papers, which you might not want to get into.

@R0cketC0der: I think I can get you all the aerodynamic coefficients for a vessel if you can input altitude and velocity; sound good?

@Maxwell Fern: No, but I can expect people to read the latest posts of a topic and to use the search feature; it's not a frequently asked question though, not deserving of going into the OP. And what I meant was that if people actually read the topic before posting asking about a question, the answers to those questions won't get buried by repeated questions of those unwilling to read or search.

@Grunf911: Well, based on some quick testing, it does seem underpowered. However, I can't just make it more powerful than the turbojet without a good bit of balance, so air-breathing fuel efficiency will have to take a big hit.

[Grunf911]

@Grunf911: Well, based on some quick testing, it does seem underpowered. However, I can't just make it more powerful than the turbojet without a good bit of balance, so air-breathing fuel efficiency will have to take a big hit.

@ferram4 - I agree. We have to find the right balance. The power should IMO be Turbojet -> Rapier -> Jet. I have not nearly tested as much as you did, but since i have done some testings with my SSTO, I will later today slap a jet, and turbojet, and rapier, and measure the speed at the end threshold of the runway, and send you results in XLS for comparison.

While i know the truth is a bit more complex than that, this might at least give you a frame of reference, as well as power ratios between the engines. Let me know if that info would be useful, or if you have some better tests i could run instead.

Edit: looking into your files i have noticed that the maxThrust values are:

Jet: 140

Turbojet: 80

Rapier: 60

Compared to Stock:

Jet: 150

Turbojet: 225

Rapier: 190

.. could it be that you made a typo, and were thinking instead:

Turbojet: 180

Rapier: 160

Edited July 25, 2014 by Grunf911
Additional info

[ferram4]

No, the turbojet making 80 is intended. You would be hard-pressed to find a real-life 1.25m diameter turbojet that made more than 100 kN. Dropping the thrust down to 180 would leave the issue ultimately unsolved.

[R0cketC0der]

@R0cketC0der: I think I can get you all the aerodynamic coefficients for a vessel if you can input altitude and velocity; sound good?

I think you misunderstood me. What I meant was getting them via the API, not with the editor analysis tool. From what I can see the API will only return the current coefficients and doesn't allow me to input any data such as speed or AoA. Basically what I want is to get the data from the first page of the FAR Control & Analysis Systems with the FAR API.

[ferram4]

That's already doable for the active vessel; all the activeControlSys get functions will provide that sort of stuff already.

[p1t1o]

Hi all,

I've been away since the rollout of 0.23, I was just wondering if FAR still has that problem where drag would always be very slightly asymmetric, causing my rockets to roll uncontrollably? I seem to remember it was a fundamental problem back then?

I've had a look through the thread, but it is HUGE and its hard to tell if people are talking about the thing Im talking about.

Cheers!

Pete

[AndreyATGB]

I haven't noticed anything like that for a long time, except for when I forgot I opened the EVE menu and set up trim to slightly roll, that was a fun thing to figure out.

[Renegrade]

@Renegrade: The only way that could be happening is if somehow, the active FARControlSys is constantly switching between the current vessel and something else, but it's forced to go to the activeVessel, so unless some mod is playing with FlightGlobals.activeVessel there's not much I can do.

There can't be any mods interfering as it's just stock+FAR. My current modded KSP is kinda.. mod heavy, so I created a brand new install from scratch (just 0.24.1 and FAR 0.14.1) to remove the possibility of any other mod interfering.

Also that's a brand new sandbox save, there aren't any other vessels anywhere save (presumably) some asteroids in orbit. This issue wasn't present in 0.24 + FAR 0.14.0... so if it isn't a FAR thing..something seriously wrong with 0.24.1?

That and 0.14.0.x has an issue wherein the UI doesn't go away if you press F2 - this is still present in 0.14.1 and only affects FAR :/

NB: The flicker doesn't occur on every flight.. could it be possible that KSP is somehow leaving the craft from the previous flight in memory at the same time?

All the messages in the log are the way they're supposed to be. Ideally, they would have gotten to adding the one bool I wanted on PartModules that would allow me to flag them as "don't save this one" to avoid log spam, but that didn't happen.

Ah, wasn't sure if those log messages were related or not. They were the only warnings/errors I saw.

Well, instead of complaining regarding nerfing rapiers, i did some reengineering, kerbal style. Behold, my new reengineered SSTO.

Special thx to Renegade and ferram

You're welcome

I'm going to raise, though, with an SRB-powered 'spaceplane':

(from my tests to isolate what's causing that weird flicker..)

[Grunf911]

(from my tests to isolate what's causing that weird flicker..)

Are you refering to the flickering of the kerbin textures on the horizon ?

..cause i am 90% sure i saw that in stock. Will check and report though

[Renegrade]

Are you refering to the flickering of the kerbin textures on the horizon ?

..cause i am 90% sure i saw that in stock. Will check and report though

No no, the stats panel in FAR flickers between two distinct set of statistics. Ferram's suggestion about it bouncing around between objects sounds reasonable (a later test where I put a plane on the tarmac and launched a second flight seemed to have numbers from that second plane) ... it's just that most of my tests have exactly 0 flights in the atmosphere, and just some asteroids in interplanetary space...

Note in my screenshot how Q (that's dynamic pressure and it's "super cereal" err super important -- your lift and drag depend on it, and therefore everything to do with attitude control and speed) is between 122 Pa (pascals) and 76,957 pascals.

76k pascals is typical for supersonic flight on the deck, 122 pascals is typical for uh, being parked on the runway with a light breeze blowing.

The only graphical bugs I'm worried about are that the FAR GUI doesn't go away when you press F2, and sometimes won't go away at all when you press the 'FAR' button (Squad's "fix" there seems to have made things worse )

(the testbed for all this is a pure install of FAR 0.14.1 and KSP 0.24.1)

[Grunf911]

The only graphical bugs I'm worried about are that the FAR GUI doesn't go away when you press F2, and sometimes won't go away at all when you press the 'FAR' button (Squad's "fix" there seems to have made things worse )

I have experienced same thing with KER. First, the blizzy's toolbar button for it disappeared in .24.1, as well as the stock toolbar button. My guess is one of the squad code updates, goofed up toolbars.

I am suspecting this one:

* Fixed an issue with the App Toolbar where mod apps wouldn't display/hide properly at the VAB.

[Renegrade]

* Fixed an issue with the App Toolbar where mod apps wouldn't display/hide properly at the VAB.

Yeah, that's what I meant by "Squad's fix there seems to have made things worse".. I had a lot fewer problems of that nature in 0.24.

Of course maybe the mod developers all worked around some problem in 0.24, and now the problem's fixed and the workarounds are causing problems :/

[thorfinn]

@Thorfinn: Calculation CLMax isn't exactly trivial... I'll see what I can do though. (Welp, this is what I get for adding the beginnings of an API; never do that again )

I think I'm missing something... from your answer to R0cketC0der, don't you sorta do that already? If we can input parameters like speed and AoA to the getter functions, then it's a matter of finding the maximum in the cL/AoA curve... isn't it?

Edited July 25, 2014 by thorfinn

[andrehsu]

I don't know if this is a bug/feature/error, but when in VAB, the cargo bays says partShielded:23, but when in flight, the partShielded: then turns into zero. Is this is some sort of bug, or is it save to ignore? Another things is that the hex cans from tac life support tends to break off at high dynamic pressure, which shouldn't happen, since it is behind fairings/cargo bays(tried both). Is FAR designed so that fairings are ignored when the craft is in high dynamic pressure?

[Hodo]

OK – I hadn't read the whole discussion. It just felt very odd that the turbojets had significantly less static thrust than the basic jets.

@Hodo: It's this section in particular that you want to cut to remove the nerf:

@PART
[*]:HAS[@MODULE[ModuleEngines*]:HAS[@PROPELLANT[IntakeAir]]]:BEFORE[FerramAerospaceResearch]:NEEDS[!AJE]
{
    @MODULE[ModuleEngines*]
    {
        @maxThrust *= [B]0.36[/B]
    }
}

You can also change the nerf percentage by changing the bold number.

Rolling the cfg file back also worked. All that did was delete that hole line.

[Hodo]

No, the turbojet making 80 is intended. You would be hard-pressed to find a real-life 1.25m diameter turbojet that made more than 100 kN. Dropping the thrust down to 180 would leave the issue ultimately unsolved.

Not quite 1.25m but it is 1.18m and the GE-F110 creates 120-125kn of thrust

Saturn AL-31 1.28m creates 122kn of thrust and that is an old version, the newer AL-41 creates over 170kn.

P&W F100, 1.18m and creates 127kn.

Soloviev D-30F6, 1.46m and creates 152kn of thrust.

Those are just what are in use today in most military fighters.

Perhaps instead of cutting the thrust in 1/3rd why not cut them in half. That would be a far more reasonable drop, seeing as you can find real life counterparts that create roughly half the power of the turbojet in game at the same size. But if you keep heading this direction you may as well take over AJE from Camlost because that is EXACTLY what he is doing. Which is why I say leave this out of FAR.

If people want more realistic jet engines they should get AJE.

Edited July 25, 2014 by Hodo

[Firov]

I think you misunderstood me. What I meant was getting them via the API, not with the editor analysis tool. From what I can see the API will only return the current coefficients and doesn't allow me to input any data such as speed or AoA. Basically what I want is to get the data from the first page of the FAR Control & Analysis Systems with the FAR API.

Ferram, he might be talking about the API, but it would be great to have the coefficient of drag and cross sectional size available in the analysis tool too. Primarily for the calculation of aerobraking/aerocapture using the following formula "Simple" Aerobraking Formula

I'm still trying to understand the formula myself, but having the drag coefficient and cross sectional area in the editor would be great. I know having the ballistic coefficient probably wouldn't be feasible, since it depends on other factors such as altitude, atmospheric density, and atmospheric scale height of the target planet.

Edited July 25, 2014 by Firov

[Hodo]

Yeah, that's what I meant by "Squad's fix there seems to have made things worse".. I had a lot fewer problems of that nature in 0.24.

Of course maybe the mod developers all worked around some problem in 0.24, and now the problem's fixed and the workarounds are causing problems :/

Noticed the flicker also, it is only the FAR menus, and in the speed of the aircraft display.

The air speed would flicker between my set MPH and m/s.

[Renegrade]

Not quite 1.25m but it is 1.18m and the GE-F110 creates 120-125kn of thrust

Saturn AL-31 1.28m creates 122kn of thrust and that is an old version, the newer AL-41 creates over 170kn.

P&W F100, 1.18m and creates 127kn.

Soloviev D-30F6, 1.46m and creates 152kn of thrust.

Those are just what are in use today in most military fighters.

Technically those are all turbofans, not turbojets, but then again, not even the TurboJet itself knows what it is.

Anyhow most of those engines explode into melty bits past about 7-800m/sec or so... The "TurboJet" is still spooling over nicely at 1600...

From the realism angle, none of the jets mounting those engines are capable of reaching space, let alone Mach 3.5. The Mig-31, with two D30s only goes Mach 2.83 at extreme altitudes, and 1.2 on the deck...

That's a 100x100-or-so orbit with 1500dv left over (clicky for big version). I am not some ace pilot, nor an ace designer, and that's entirely stock.

Ferram, what if we changed the curve so that it starts off with a lot of static thrust for the TJ as well as the basic, but then falls off?

IE:

150kn base

0 speed - 100% (1.0)

400 speed - 50%

1700 speed - 0%

That's probably not very realistic in terms of engine performance from what I understand, but is it possible that would approximate the FLYING performance that FAR is trying to reach?

Or maybe just wait for Nathan to write SJE?

I'm still trying to understand the formula myself, but having the drag coefficient and cross sectional area in the editor would be great. I know having the ballistic coefficient probably wouldn't be feasible, since it depends on other factors such as altitude, atmospheric density, and atmospheric scale height of the target planet.

I'd love to be able to see the Cd and area in the editor as numbers. I'm often tweaking my planes and rockets to try to squeeze out that last bit of efficiency, and that would definitely be handy. Also having a Cd*Area bit would be convenient too..

Oh another update about that flicker - it seems related to the bug where the display won't close... When it's flickering, if you click FAR off, and then turn off the HUD, the flickering goes away (but the windows are still open).