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

[jrandom]

Frankly, I'm thinking of just stripping out the control systems since they always seem to cause more trouble than they're worth. Too many people get confused by them or blame them for their problems even when they're turned off. Or turn them on with SAS, and then complain that it doesn't do anything since they left SAS in control. It would also clean up FAR's focus, since it's intended to be an aerodynamics plugin, not a control systems plugin.

NOOOO! Don't remove useful functionality! There will always be some subset of people who never read the instructions, and there's nothing you will ever be able to do to change that. Don't hinder your mod on their account, I beg you!

[localSol]

I like the control assists too. Adjust a few things and it's a flight comfortable enough to serve yourself an in-flight meal. And you're the captain. And captains get a captain's hat.

What would be great too if possible too would be a way to adjust deflection angle during flight of control surfaces, or even toggle P,Y,R independently as part of per actiongroup toggles that would include all settings from the FAR control surface menu.. With this you could have better maneuverability at low altitude and better sensitivity during transonic and higher speeds at high altitudes or on other planets. I realize though I have hardly used the dynamic control adjustment feature which may do a lot of that if I adjust the variables. I just get into a routine and forget it's there.

[Goozeman]

I agree, the wing leveler is extremely useful. I don't really need the others, though DCA can be useful for spaceplanes.

[Senshi]

Some control system is a must, and the current FAR implementation works just flawlessly. At least I can't think of a way to improve them...Yaw dampener and wing leveler make my life much easier for all my borderline unstable designs. As an avid year-long (decade?) flight simmer, I always felt right at home with them.

I also can't imagine those tiny buttons being problematic for players that don't use assistance systems. You don't understand/want those, just don't use them. I also doubt a general layman player will understand right away what the shortcuts (DCA...) mean at all without looking at the help. And once you look at the help, everything becomes clear .

[ferram4]

Fine, I'll leave them then. I'll just shift around the GUI so it's a little clearer (I hope).

Good news, we're getting different atmospheric compositions and more exact supersonic stuff! Eve and Duna are being modeled with CO2 atmospheres, and Jool with an H2 atmosphere. The speed of sound being 800 m/s, even in the upper Joolian atmosphere feels really, really weird. I do worry that the more exact shock relations might be noticeably more computationally intensive than the previous setup, but it was somewhat necessary for the atmospheric composition implementation. Also, I couldn't pass up an exact solution to the θ-β-M equation.

Besides that, I've reduced the default time constant for control surfaces, so they should deflect a little faster and cause less trouble for the SAS. I've also exposed the parameter in the config, so it can be modded back to the original 0.1s if desired (or larger for hard-mode), or it can be dropped to a crazy 0.00001s if you need absolute instant deflection with all the instant stalling that will come with it; a good thing all around.

Flap / camber code also got refactored so that it's easier for MechJeb to deal with by simply keeping everything internal to FAR; it should also remove some transient unrealistic stuff.

Haven't got it working yet, but I'm also looking into Blizzy's awesome new toolbar plugin, so FAR's GUIs should be less obnoxious if I get it to work with that.

So v0.12 should be awesome.

[jrandom]

That's just... wow. Can't wait!

I mean, I can wait, sorta have to wait. But the sentiment is there.

[Guest]

Would that be possible to allow flaps and speedbrakes to use the same surfaces as controls? Many modern fighters don't have separate speedbrakes, but rather a "speedbrake configuration" in which they deflect their control surfaces to increase drag. Flaperons are another nice invention that's been in use since WWII, but we still can't have them in FAR...

[ferram4]

I think I'll be able to get that to work... Now I have to research the details of how these things are set up so I can model them correctly.

[Camacha]

So v0.12 should be awesome.

Even more awesome. That is pretty awesome. More headaches trying to predict things like drag, hurrah!

[Senshi]

I actually barely understood anything in your post regarding the upcoming features (I have near zero interest in theoretical physics/math), but everything that makes the aerodynamics even more real will bring joy to my flightsim heart . The toolbar implementation would be great indeed, the number of GUI buttons to organize around the screen is getting out of hand with all these awesome complex plugins cropping up now.

[Frederf]

Frankly, I'm thinking of just stripping out the control systems since they always seem to cause more trouble than they're worth.

I think the control system should be applied to the engineering the aircraft end of the problem and leave FAR to the modeling of the environment itself. I'm a firm believer in keeping environment modeling apart from usability aids. If it were up to me FAR would be split into mandatory environment interaction and optional support. It should be possible to fly in a 1910-style setup where everything works as it should mechanically but without any graphs and readouts if desired.

[jrandom]

I'd actually like to see an additional control: "Attempt to maintain altitude by altering pitch". Also maybe an "Attempt to maintain altitude by altering thrust". Doesn't have to be perfect, just something to take those last fine-tuning steps when flying long distances, especially with Real Solar System installed.

[Camacha]

I think the control system should be applied to the engineering the aircraft end of the problem and leave FAR to the modeling of the environment itself. I'm a firm believer in keeping environment modeling apart from usability aids. If it were up to me FAR would be split into mandatory environment interaction and optional support. It should be possible to fly in a 1910-style setup where everything works as it should mechanically but without any graphs and readouts if desired.

In principal I agree with you, but you should be careful not to split things up that get used together 99,8% of the time anyway. In those cases, you will only increase the number of things the user has to do to get what he wants (download and install two or three files instead of one) and you will possibly add more calculations to KSP because things overlap. If that is the case, splitting things up is not desirable.

That being said, I think the aids could be split up into a seperate mod, but that is also a matter of whether Ferram wants to maintain another mod seperately. I can imagine he has enough work to do already. In reality, I am pretty content with them being part of FAR. No one is forcing you to use them. The same goes for the graphing aids in the VAB.

[Camacha]

I'd actually like to see an additional control: "Attempt to maintain altitude by altering pitch". Also maybe an "Attempt to maintain altitude by altering thrust". Doesn't have to be perfect, just something to take those last fine-tuning steps when flying long distances, especially with Real Solar System installed.

You know you could probably achieve that by using kOS? Building some kind of PI/PD/PID-control is actually not that hard, especially with all the stuff that can be found on the internet on the subject. Tuning it can be somewhat tricky, but even just applying something like the Ziegler-Nichols method usually is very effective. Besides, it is pretty much exactly what you are doing with the current controls.

[jrandom]

You know you could probably achieve that by using kOS? Building some kind of PI/PD/PID-control is actually not that hard, especially with all the stuff that can be found on the internet on the subject. Tuning it can be somewhat tricky, but even just applying something like the Ziegler-Nichols method usually is very effective. Besides, it is pretty much exactly what you are doing with the current controls.

I just installed kOS today. I'll have to go dig up the example PID code since I've wanted to learn how to do that anyways.

[Camacha]

I just installed kOS today. I'll have to go dig up the example PID code since I've wanted to learn how to do that anyways.

If you really want to learn the workings of these types of controllers, try to make one yourself - with help of the internet of course. But that way you gain a little more insight into what makes it tick, instead of just translating the code from example code.

If you start out with just the P-term it is easy, and you can see what changes when you add an I- or D-term to it.

Edited December 8, 2013 by Camacha

[jrandom]

I remember basic algebra and at one time could do simple derivatives and integrals. Granted, that was almost two decades ago...

I've give it a whirl.

[localSol]

That's just... wow. Can't wait!I mean, I can wait, sorta have to wait. But the sentiment is there.

Just what I was thinking. Haha!

Good news, we're getting different atmospheric compositions and more exact supersonic stuff! Eve and Duna are being modeled with CO2 atmospheres, and Jool with an H2 atmosphere. The speed of sound being 800 m/s, even in the upper Joolian atmosphere feels really, really weird.

Yeah! Now I have more reasons to hyperedit my various planes above other planets for re-entry or high altitude tests..why did I wait so long to try that last week, very fun..now with that, even better. No idea how sound travels in CO2. Looking forward to flying in all kinds of weird gas mixtures.

[ferram4]

Well, it turns out that at 300K, here's what you get for sound speeds:

21% O₂, 79% N₂: 347 m/s

100% CO₂: 269 m/s

100% H₂: 1316 m/s

Sound speed is calculated as:

a = SQRT(T * γ * R_gas)

where

a = the speed of sound in m/s

T = temperature in K

γ = ratio of specific heats

R_gas = 8.3145 * J / (mol * K) / M

M = molar mass of the gas, in kg / mol

The ratio of specific heats is nearly constant and is largely based on the molecular shape and arrangement of atoms. For a diatomic gas, it's ~1.4; for CO2, it's ~1.28. For water, it's ~1.33. For a monoatomic gas (argon, xenon, other noble gases) it's ~1.66. This is the number that controls a lot of supersonic phenomena, such as the maximum pressure coefficient, shock angles, pressure behind shocks, the maximum angle that a supersonic flow can be turned through in an expansion fan, etc.

Overall, I haven't done too much testing to see what the big differences are, but suffice to say that the different atmospheres (with the exception of Jool, which is weird) feel different, but not horribly different.

It does require spaceplanes to land at Mach 1 on Duna though. Which is a serious win.

[Starwaster]

Well, it turns out that at 300K, here's what you get for sound speeds:

21% O₂, 79% N₂: 347 m/s

100% CO₂: 269 m/s

100% H₂: 1316 m/s

Sound speed is calculated as:

a = SQRT(T * γ * R_gas)

where

a = the speed of sound in m/s

T = temperature in K

γ = ratio of specific heats

R_gas = 8.3145 * J / (mol * K) / M

M = molar mass of the gas, in kg / mol

The ratio of specific heats is nearly constant and is largely based on the molecular shape and arrangement of atoms. For a diatomic gas, it's ~1.4; for CO2, it's ~1.28. For water, it's ~1.33. For a monoatomic gas (argon, xenon, other noble gases) it's ~1.66. This is the number that controls a lot of supersonic phenomena, such as the maximum pressure coefficient, shock angles, pressure behind shocks, the maximum angle that a supersonic flow can be turned through in an expansion fan, etc.

Overall, I haven't done too much testing to see what the big differences are, but suffice to say that the different atmospheres (with the exception of Jool, which is weird) feel different, but not horribly different.

It does require spaceplanes to land at Mach 1 on Duna though. Which is a serious win.

How is atmospheric composition being assigned to planets? Are we saying, "It's Duna so it's mostly CO2" or will there be a way to custom assign composition? Especially if a new planet is added? (which is really what I'm getting at; how extensible will it be)

Also, another question:

I decided to see if I could make an engine fairing by taking the KWR interstage pieces, stripping the decouplers out of them and changing the title to have the word Fairing in it (since I'd read that this was one of the ways that FAR determined if a part was a fairing)...

and it seemed to work in that the the new fairing GUI started reporting how many pieces were being shielded. The bad news is that no matter how I physically arranged it, it never actually seemed to shield anything, least of all the engines. How exactly does a fairing determine how many parts are being protected?

[ferram4]

Atmospheric composition will be listed in the config.xml and can be modified at whim (though I'd prefer it if you didn't). Automatically adds an entry for each body id#, and if a body is loaded that doesn't have a composition preset explicitly stated it defaults to using air. I don't know how it will work with Planet Factory, but it will handle the expansion of the stock solar system perfectly fine. Whether it works with Planet Factory is dependent on the order that things start up in.

Fairing determine what pieces should by calculating the bounds of the fairing object and then searching through the vessel's parts to see if the part origin is inside the fairing. Since KW Rocketry parts have their origins placed at the center of the engine, they should be shielded perfectly fine; I'll investigate and see if I can find any errors.

[drtedastro]

Well, it turns out that at 300K, here's what you get for sound speeds:

21% O₂, 79% N₂: 347 m/s

100% CO₂: 269 m/s

100% H₂: 1316 m/s

Sound speed is calculated as:

a = SQRT(T * γ * R_gas)

where

a = the speed of sound in m/s

T = temperature in K

γ = ratio of specific heats

R_gas = 8.3145 * J / (mol * K) / M

M = molar mass of the gas, in kg / mol

The ratio of specific heats is nearly constant and is largely based on the molecular shape and arrangement of atoms. For a diatomic gas, it's ~1.4; for CO2, it's ~1.28. For water, it's ~1.33. For a monoatomic gas (argon, xenon, other noble gases) it's ~1.66. This is the number that controls a lot of supersonic phenomena, such as the maximum pressure coefficient, shock angles, pressure behind shocks, the maximum angle that a supersonic flow can be turned through in an expansion fan, etc.

Overall, I haven't done too much testing to see what the big differences are, but suffice to say that the different atmospheres (with the exception of Jool, which is weird) feel different, but not horribly different.

It does require spaceplanes to land at Mach 1 on Duna though. Which is a serious win.

H'mm, I find this quite interesting. I am quite surprised that the less dense gas H2 has a faster speed of sound than the more dense CO2.??? Personally I would have gone with the exact opposite, as typically the more dense the faster wave propagation through the medium....

[localSol]

Well, it turns out that at 300K, here's what you get for sound speeds:

21% O₂, 79% N₂: 347 m/s

100% CO₂: 269 m/s

100% H₂: 1316 m/s

Sound speed is calculated as:

a = SQRT(T * γ * R_gas)

where

a = the speed of sound in m/s

T = temperature in K

γ = ratio of specific heats

R_gas = 8.3145 * J / (mol * K) / M

M = molar mass of the gas, in kg / mol

The ratio of specific heats is nearly constant and is largely based on the molecular shape and arrangement of atoms. For a diatomic gas, it's ~1.4; for CO2, it's ~1.28. For water, it's ~1.33. For a monoatomic gas (argon, xenon, other noble gases) it's ~1.66. This is the number that controls a lot of supersonic phenomena, such as the maximum pressure coefficient, shock angles, pressure behind shocks, the maximum angle that a supersonic flow can be turned through in an expansion fan, etc.

Overall, I haven't done too much testing to see what the big differences are, but suffice to say that the different atmospheres (with the exception of Jool, which is weird) feel different, but not horribly different.

It does require spaceplanes to land at Mach 1 on Duna though. Which is a serious win.

Requires, but how could that be? I have not actually landed yet (in one piece) but did notice the speed for me was pretty amazing at low altitude due to the low atmospheric pressure/density. I just guessed I might need more wing area, swing/telescoping wing or a fancier solution to land for some planes than just gliding with control surfaces. And/or huge flat improvised runway and nerves of titanium.

1316 m/s in H2, that does go against my unfamiliar intuition, I just read that the speed of sound in liquid water can be around 1484 m/s which seems very close! But then I just understood, this formula includes density, it must be very dense hydrogen even at altitudes you can get away with flying in.

...Jupiter stunt pilots...

IIRC just for discussion the temperatures likely on earth didn't change the speed of sound in air as much as I wondered they might when I went googling around some time ago..I guess in the scale of kelvin, usual temperatures of earth atmosphere are very narrow.

[softweir]

H'mm, I find this quite interesting. I am quite surprised that the less dense gas H2 has a faster speed of sound than the more dense CO2.??? Personally I would have gone with the exact opposite, as typically the more dense the faster wave propagation through the medium....

Density does affect speed of sound, but the mass of the molecules has a much greater effect. H2 molecules are very, very much lighter than CO2 molecules, so the speed of sound is very much higher.

[Camacha]

Will there be a way to detect the substance you are flying in without relying on lookup tables? The density or other properties of the gas or fluid you are moving through are - as you are well aware of - a very useful thing to know when modeling performance. I try to build my craft as universal as possible (measuring as much as possible and assuming the least) and different atmospheres could pose a bit of a problem there, as suddenly three terms are unknown in something like the drag equation.

I have been looking at the ideal gas law to convert temperature and pressure into density, but unless I am mistaken you will need the molar mass for that, which will be different for each gas.