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

[biohazard15]

Yeah, new high-altitude drag is kinda noticeable now - my rockets now tend to "fart" in order to keep Ap when I use MJ's ascent guidance. Not that it severely affects performance, though (FASA Atlas was able to put 10 tons to 120x120 orbit in 0.25, and still able to do that in 0.90)

[Alshain]

I have a question. If I were moving from NEAR and wanted to "import" some of my plane designs without directly altering their parts, what would I assign to wing strength. I know NEAR's fixed value and FAR's default value are not the same, I'm just looking for an equivalency.

[ferram4]

@Rakaydos: Okay, so then it sounds like your flaps are set to deflect as flaps, they have a deflection angle of 0. There is no other explanation.

@Voculus: No, that's right. Skin friction drag coefficient increases a lot as Reynolds number decreases, but dynamic pressure decreases a lot faster. I also flew a ship that looked almost exactly like that, but with more swept wings and even more wing area for my test, so I'm not sure what's wrong then.

I also looked at correlations for skin friction drag at the point where continuum flow starts to break down, and it's apparently supposed to be even higher, so... yeah.

@Alshain: Well, you can't, simply because NEAR's value is infinite. Okay, pedantry aside, the default value will give you more than enough wing strength. The mass might be too high though, so try reducing it a bit.

[Rakaydos]

@Rakaydos: Okay, so then it sounds like your flaps are set to deflect as flaps, they have a deflection angle of 0. There is no other explanation.

Then I've got a user interface issue:

Edited December 18, 2014 by Rakaydos

[obj]

@Rakaydos: I raised a github issue about spoilers that looks similar to what you're having with flaps. See https://github.com/ferram4/Ferram-Aerospace-Research/issues/40. TL;DR: negative flap/spoiler deflections seem to be broken.

[IllicitMedic]

Yeah, new high-altitude drag is kinda noticeable now - my rockets now tend to "fart" in order to keep Ap when I use MJ's ascent guidance. Not that it severely affects performance, though (FASA Atlas was able to put 10 tons to 120x120 orbit in 0.25, and still able to do that in 0.90)

My MJ accent AP has always done that to maintain AP while coasting, even with stock aerodynamics.

Fart, lol, love it.

[Voculus]

Thanks for the clarification, Ferram. I'll have to start burning out at a steeper angle in the future.

[biohazard15]

My MJ accent AP has always done that to maintain AP while coasting, even with stock aerodynamics.

Fart, lol, love it.

Well, mine too, but it was almost un-noticeable in 0.25, especially if the ascent burn ended somewhere above 40 kilometers. Now it's just like stock.

[Rakaydos]

@Rakaydos: I raised a github issue about spoilers that looks similar to what you're having with flaps. See https://github.com/ferram4/Ferram-Aerospace-Research/issues/40. TL;DR: negative flap/spoiler deflections seem to be broken.

Sounds like the same problem. And if I use spoilers for the same effect, I'd need to turn on brakes on the runway to get the lift I need.

Might be able to figure out a workaround, but w havean identifued bug for Ferram to work on.

[obj]

Sounds like the same problem. And if I use spoilers for the same effect, I'd need to turn on brakes on the runway to get the lift I need.

Might be able to figure out a workaround, but w havean identifued bug for Ferram to work on.

I fixed the apparent bug and rebuilt and my spoilers work now, at least: https://github.com/ferram4/Ferram-Aerospace-Research/pull/42

[karamazovnew]

This may be another case of user error, but I'm noticing massive amounts of drag in the upper atmosphere.

However, when I get into the upper atmosphere, get up to Mach 7+, and push my Ap up to 120k, the plane is now a solid yellow mass of draginess. Is that a word? I have to keep burning more fuel to keep the Ap up. Most recently, at a height of 55 km, I finished another burn to raise up the Ap, and kept the nose prograde. In about ten seconds, the Ap had dropped from 120k to 84k. This happening with any plane, in any configuration, and the excessive drag is only present in the upper reaches of the atmosphere.

Hope that makes sense. Is this a FAR issue, or my issue? Anyone else experiencing this?

Same here, although I'll use reentry as examples. Simple rocket with nosecone, nose first.

- starting from a 100km orbit. 68 km Pe results in a drop of Ap to 75km. 67.7 km Pe results in complete reentry.

- starting from a 200km orbit. 65 km Pe results in a drop of Ap to 129km. 63 km Pe results in complete reentry.

This can't be normal. I'm not saying that I miss the old way, as there was next to no friction until slamming into a wall at 40km altitude. But this is worse, spaceplanes will have a hard time to get up into orbit, while reentry using fuselage effect will be impossible. Maybe a happy medium between the two?

Edited December 18, 2014 by karamazovnew

[ferram4]

Yeah, looking at the data it's about 50 times too high. The current dev build should fix that, as well as the flap and spoiler deflection limitations, and not assume the user will pick a sane altitude for testing.

Release of the bugfixed version will wait until I make sure that I got all the bugs.

[Empiro]

Awesome! I'm glad you're looking into this and fixing the issues. I have a small request for the flight info display: would it be possible for you to show the amount of (maybe approximate) drag in terms of force and/or acceleration? It seems like the numbers are all available already (coefficient of drag, velocity, atmosphere thickness, etc.), and knowing the amount actual amount of deceleration / drag forces would let us plan our trajectories and designs better.

[NathanKell]

Uh, drag force = Q * Cd * ref area. That's already there.

[Empiro]

Right -- the numbers are available but it's hard to do the math in my head in the middle of a flight. If we have the actual net acceleration, we'd be able approximate delta-v losses in our head fairly easily.

Much of the stuff we think about in ksp boil down to delta-v, so having a number that's more easily converted to delta-v is helpful I think.

[Rakaydos]

Got it into orbit!

Drag was a bit che, so I had to light rockets at 1400m/s insteead of 1600, but I had enough reserve fuel to make it to orbit nyway. I can only hope I can get close to that performance with a payload.

[blowfish]

Drag was a bit che, so I had to light rockets at 1400m/s insteead of 1600, but I had enough reserve fuel to make it to orbit nyway. I can only hope I can get close to that performance with a payload.

You might be able to get rid of some of that drag with more swept wings - at hypersonic speeds those wings are sure to be protruding into the shockwave.

[ferram4]

Well, that and the fact that it's a biplane. Biplanes are terrible, even when the wings aren't as close together as that one's are.

[Rakaydos]

And yet I put Mk3 parts into space.

[Voculus]

Took the current dev version of FAR out for a whirl today. I'm home again!

[Autochton]

And yet I put Mk3 parts into space.

And with a monoplane, you'd probably get more mass up there, too, with more or less the same design. Honestly, just strip off the one set of wings and move the other to the middle position, and you should be fine. Double-wings like that generate almost no extra lift under any regime I can think of, and you'd be better off at low speed with some well placed flaps, maybe slats.

[blowfish]

And yet I put Mk3 parts into space.

I'm sure it's doable, but you're only getting a maximum of 20% more lift at subsonic speeds, and probably much less at supersonic speeds, while creating much more drag.

[stevron]

Where does one obtain this dev version, or is it just the main download?

[jstnj]

Where does one obtain this dev version, or is it just the main download?

Use the github link in the OP and search for the most recent .dll

[Hodo]

And yet I put Mk3 parts into space.

You can put a school bus into orbit if you put enough power behind it. Does that mean it is right? No...

I can tell you you can send MUCH larger craft into orbit with monowing designs if they are built correctly, and on top of this, how many supersonic biplanes do you see?