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

[camlost]

The second part can be fixed by taking the code from my post above yours and putting it into the FerramAerospaceResearch config where the turbofan code is. I goofed.

The velocity curve is independent of altitude. Besides that is just one engine. What I'm talking about is that all the engines, for example those in B9 pack, are seriously wrong. The problem is KSP uses atmosphere curve to determine Isp and velocity to determine the thrust. While this works reasonable well for rockets, jet engine performance is just outrageous

[ferram4]

Well, yes. Really what should happen is that jet engines should need much more intake air but have a much lower ignition threshold. That would allow the engines to effectively lose thrust as they ascend, but I haven't tried to work that out yet.

Especially since the jets count the mass of IntakeAir when calculation fuel consumption (in reality, they shouldn't, since a proper analysis of a jet engine also includes the air coming in, so the air mass flow balances out). So basically, since all air-breathers run at 1:15 fuel to air they're 16 times as efficient as they say they are. When the math is done out, a turbojet at Mach 4 in KSP is approximately as efficient as the most modern high-bypass turbofans that exist in reality. So yeah, they've always been overpowered, but everyone would complain if they saw their jets with Isps of ~300s or less, so we're stuck with them like this until there's a way to say "don't count the mass of this fuel type in Isp calculations."

[camlost]

Well, yes. Really what should happen is that jet engines should need much more intake air but have a much lower ignition threshold. That would allow the engines to effectively lose thrust as they ascend, but I haven't tried to work that out yet.

Especially since the jets count the mass of IntakeAir when calculation fuel consumption (in reality, they shouldn't, since a proper analysis of a jet engine also includes the air coming in, so the air mass flow balances out). So basically, since all air-breathers run at 1:15 fuel to air they're 16 times as efficient as they say they are. When the math is done out, a turbojet at Mach 4 in KSP is approximately as efficient as the most modern high-bypass turbofans that exist in reality. So yeah, they've always been overpowered, but everyone would complain if they saw their jets with Isps of ~300s or less, so we're stuck with them like this until there's a way to say "don't count the mass of this fuel type in Isp calculations."

Might as well dump the system and forget 'IntakeAir' altogether. InfiniteDice did something similar to his piston engine. In the case of jet engines, basically let atmo density and speed and throttle be input, as a result apply thrust and reduce fuel. Also detect the number of intakes and engines, if intakes are not enough, just add a multiplier

[Tic-Tac]

I had the same issue with a probe today. If you go into the FAR flight data menu when this happens you'll probably see some absurdly high number at "reference area". Basically, FAR erroneously assumes your craft has an enormous surface area. Combined with its (relatively) low mass, it descends like a sheet of paper rather than like a spacecraft on ballistic re-entry

Updating to FAR 12.5.2 fixed it.

But the thing is, I upgraded it yesterday, and it changed nothing :/

[ÄlveKatt]

I made a nice airplane that feels quite manouvreable with your mod:

https://www.dropbox.com/s/jy57qcfrmtruuqc/X-Kerbilazier-mkV.craft

You need this mod as well though: http://kerbalspaceprogram.com/realchute/ Realchute, because using the wheel breaks at high speeds is pretty suicidal...

Since the last update you really need an analogue stick I think. I am playing with keyboard, and the rolls are almost too quick to control. That said, this plane is very flyable without having SAS on. It could use smaller engines though, but there don't seem to be any. XD

[DaMichel]

Taverius made some rescaled parts including smaller engines.

http://forum.kerbalspaceprogram.com/threads/15348

Mind that his pack includes some balancing adjustments for stock parts, too.

You can decrease the deflection of the control surfaces when you right click on them in the SPH. That should help with the control issues.

[Surefoot]

(...) aileron reversal effects (...). Lots of rage will occur once that is implemented.

.. challenge accepted If we reach that level of realism, that will be very impressive, i dont know if any sim out there goes that far (pun intended).

[NathanKell]

I'm more likely to squee than rage re: any of those changes, but you knew that.

[Traches]

I made a video trying to cover the basics of rocket building with FAR; hopefully it will help those having trouble with it. Please let me know if I need to fix anything! (Besides my rambling, that is.)

[Motokid600]

Im having touble finding this.. I know ive read it somewhere before. Stock Dv needed to get to Kerbin orbit is 4550m/s. So.. what is it with a properly constructed craft and FAR? Its MUCH less that's about all I know. I ask because I keep building over powered rockets. Granted im only sending up a few tons at a time. With StretchySRB's+FAR SSTO rockets are way too easy to make. But again.. my heaviest palyload in this play through so far was only 2.5 tons, so..

[ferram4]

@Traches: Cool!

Comments as I'm watching:

~5:20: The phrase you're working for is "moment arm." Moments are the angular equivalent of forces; torque generally refers to a specific type of moment, which twists something rather than tipping or bending it (as other moments can do).

~6:30: The Center of Pressure is NOT the same as the Aerodynamic Center / Center of Lift (I prefer AC to CoL to avoid implying that drag doesn't affect stability as much). The Center of Pressure is defined as the point where all the aerodynamic forces act without any extra moments to balance the system; it moves heavily with changes in angle of attack, is harder to use to determine stability and often can take an excursion outside the vehicle due to the moment arm necessary to balance any aerodynamic moments. The Aerodynamic Center / Center of Lift is where the forces can be modeled using forces and a constant moment, and is much easier to use to balance forces. The only time the CoP and CoL are in the same place is for perfectly symmetrical objects (for rockets this is a decent assumption; for planes, not so much).

~10:30: Sometimes the fairings aren't properly accounted for in the editor. I'm not entirely sure why though.

~15:15: You can use SAS for the first, short vertical portion of flight no-problem (unless you've got absurd roll authority). But otherwise, correct.

~23:00: Yeah, bleep out the curse or re-record that. Also, watch where you put your beer.

@Motokid: It's about 3.5 km/s. Stretchy SRBs are actually a lot heavier than you think (so more fuel mass to expel); they're very dense compared to other rockets.

Edited January 14, 2014 by ferram4

[Motokid600]

Thanks again ferram.

[Kalliopi42]

Complete newb here, having some problems I'm hoping someone might know something about. Haven't been able to find it anywhere. I'm playing a heavily-modded version (Basically what Scott Manley is playing right now, but in 0.22). I recently upgraded FAR to fix a bug that was making it impossible to play (at someone's suggestion) and now... the game always hangs on load at a B9 part (B9_Aero_Wing_ControlSurface_SE_1m) which is also almost exactly 50% loaded... I haven't changed anything but FAR... Is there any hope? Have I completely lost my game? I've tried reverting, but to no avail.

[ferram4]

The current version of FAR is incompatible with KSP v0.22. You'll want to use FAR v0.11, which can be found by following the mediafire link to the older versions on the OP of this thread.

Basically, the game is crashing trying to load the new tweakables stuff, which didn't exist in KSP 0.22.

[RabidMonkey]

Would it be possible to get a CP calculator or performance calculator for rockets similar to the one provided for planes? I'm horrible at aerodynamics, but I enjoy the challenge FAR provides when building rockets. It would be nice to see a plot of how stable the rocket is through various angles of attack (starting at 90) and various speed regimes.

Or is this possible with the existing calculator?

[ferram4]

It should be. There's really no reason it shouldn't be.

[Traches]

@Traches: Cool!

Thanks for the input! I'll make some edits and re-upload. Hopefully I'll get it done by tomorrow.

I was an engineering major for a couple years so I should know those things... It's amazing how quickly it disappears.

Edited January 14, 2014 by Traches

[NathanKell]

Regarding dV to orbit: back before I switched to RSS, my best was ~3050 expended to a 100x100 orbit. My target would be 3200, which is highly possible with a reasonably staged rocket and a decent ascent profile, no throttle limiting necessary. Remember this is actual dV expended, not a "subtract vacuum dV remaining from total vacuum dV at launch" check.

[localSol]

Thanks Damichel, yes variable sweep wings definitely do work in FAR, though it occurs to me I didnt even think of trying pivoting the hinge in the SPH and see if that changed the FAR analysis pre-flight! I just used one mostly unswept servo setting and guessed for the fully swept setting.

I accept your challenge to challenge myself, not-a-cylon, that's quite a nice plane. I have been forgetting that most of my planes lately have had problems due to CoM being so far back that the rear-only control surfaces don't do much of anything, and/or have serious problems with negative L/D at takeoff even when positioning wheels conservatively. And so my engines are doing more work than they might need to. Where I guess an Sr-71 type design moves at least two of the engines further forward, and a great deal of the mass in my planes is in the engines. Or maybe I could just use some otherwise dead weight to shift the 'red' (dynamic?) CoM as shown by RCS build aid more forward. I just haven't had much luck with canards in the cases where the CoM is far back. Except that they really do help pitch the plane up in those cases. Not that I'm 'anti-canard' (lol), they just seem to cause extra drag and stalling for my planes compared to rear ailerons. PWings all-moving procedural surfaces seem great for potentially sleeker canards and all sort of kerbal airfoils but for me right now they cause the CoL in FAR to go off center, something with part mirroring maybe. Still, 0.7 is a great update.

I've got to at least try a TWR under 1...

[Luckfish]

I made a video trying to cover the basics of rocket building with FAR; hopefully it will help those having trouble with it. Please let me know if I need to fix anything! (Besides my rambling, that is.)

Thank you so much for the video Traches... Since installing FAR I had been having serious troubles in design/launch, and had been hoping there was a primer on the internet somewhere. I think it would probably help quite a few people if a link to your video was in the original FAR post, and in the Spaceport.

[BelgarionNL]

Ferram do you have an update on when your mod will work with Mechjeb?

I know you are ready to go but we are still waiting on mechjeb?

[Kalliopi42]

The current version of FAR is incompatible with KSP v0.22. You'll want to use FAR v0.11, which can be found by following the mediafire link to the older versions on the OP of this thread.

Basically, the game is crashing trying to load the new tweakables stuff, which didn't exist in KSP 0.22.

Ahaaaaaa. I wasn't going back far enough. Ferram Beuller, you're my hero.

[TelluriumCrystal]

Ferram, I am curious as to how I might go about making reentry capsules that want to face the correct direction (heat shield down) during reentry. Here's one I made for a small rover I built:

During reentry testing it flipped itself around nose first, despite me desperately trying to keep it facing heat shield down, once it hit the thicker layers of the atmosphere. As you can imagine, this resulted in Rapid Unscheduled Disassemblyâ„¢. Any advice would be greatly appreciated!

[NathanKell]

1. Flip the whole capsule upside-down in VAB (airflow comes from top of VAB)

2. Ensure CoM is in front of aerodynamic center.

(3. check the flight analysis tab for Cm at high mach--but step 2 should ensure stability)

That doesn't mean it will *orient* to that attitude if it starts far from it, but it should ensure it will be stable *in* that attitude.

[ferram4]

@BelgarionNL: No idea. It's not something I pay much attention to myself; I don't use MJ.

@Thrfoot: You don't necessarily need that procedural fairing around the payload on the reentry vehicle; it should be fine without it. Otherwise, just try to make sure that the CoM is very, very close to the heat shield so that it's stable. If you're doing a skycrane design it might make sense to send it in upside down so that the heavy fuel in the skycrane helps orient it properly, but then you'll have to bring along drogue chutes and RCS to flip it upright once you ditch the shield. If you're integrating the landing rockets into the rover, make sure that the fuel tanks are as low to the ground as you can manage.