Sign in to follow this  
ferram4

[0.90]NEAR: A Simpler Aerodynamics Model v1.3.1 12/16/14

Recommended Posts

Complicated installation procedure?

It's copying a directory over. NEAR is exactly as complicated to install, as is any other mod you'll install.

Share this post


Link to post
Share on other sites
My understanding was that tracking terminal velocity balances drag and gravity losses and is the most efficient way to do a vertical ascent as long as drag is mostly proportional to v^2 throughout the speed range of interest. It's not necessary for reference area to be proportional to mass. That result just becomes a lot less useful if you can pitch over early instead of slowly climbing straight out of the soup first.

But gravity losses aren't proportional to v^2, are they? They're inversely proportional to acceleration/speed...

:S

Share this post


Link to post
Share on other sites

Could there be an option to enable aerodynamic breakups?

It's so satisfying watching my space stations deorbit and break up with Nonbles Kerman still aboard.

Share this post


Link to post
Share on other sites

Then you probably want to play with FAR. This is supposed to be a simpler aerodynamics model; I will not make it more complicated when there's a perfectly good sophisticated model out there for people to use.

Share this post


Link to post
Share on other sites

What speed does this assume we are moving at in terms of mach physics? 0 m/s? You say that it is based on FAR, but minus wing interactions and Mach effects. I'm curious what exactly that entails.

What would be hilarious really evil would be to automatically assume that everything acts like it would at mach 0.95, with drag coefficients so high that they make bricks look like arrows.

Edited by Pds314

Share this post


Link to post
Share on other sites

In terms of Mach number, you are always at Mach = 0 for NEAR. This is analogous to an infinite speed of sound, and flow physics don't suddenly change at a given velocity because you're moving faster than a pressure wave can. In practice, this means no transonic drag rise, no extra supersonic drag, no wacky variations in lift, and no shifts in the aerodynamic center in the transonic regime.

For wings, basically sweep has no effect, and neither does aspect ratio. Wing stall is very much simplified (no hysteresis like in FAR). Biplanes are just as efficient with their area as monoplanes are. In practice, this means that only area affects the lift of a wing in NEAR. Without sweep effects, lots of delta wing craft can behave very differently than how they should.

Share this post


Link to post
Share on other sites
In terms of Mach number, you are always at Mach = 0 for NEAR. This is analogous to an infinite speed of sound, and flow physics don't suddenly change at a given velocity because you're moving faster than a pressure wave can. In practice, this means no transonic drag rise, no extra supersonic drag, no wacky variations in lift, and no shifts in the aerodynamic center in the transonic regime.

For wings, basically sweep has no effect, and neither does aspect ratio. Wing stall is very much simplified (no hysteresis like in FAR). Biplanes are just as efficient with their area as monoplanes are. In practice, this means that only area affects the lift of a wing in NEAR. Without sweep effects, lots of delta wing craft can behave very differently than how they should.

I see. Well, probably better than that one highly experimental this-is-not-a-good-solution aerodynamics mod you made that basically makes the speed of sound 0 m/s.

BTW, I don't how, but you need to make this more visible. When I first heard of NEAR, I Google-searched "NEAR KSP" and got the Near future mod family.

Edited by Pds314

Share this post


Link to post
Share on other sites
I see. Well, probably better than that one highly experimental this-is-not-a-good-solution aerodynamics mod you made that basically makes the speed of sound 0 m/s.

BTW, I don't how, but you need to make this more visible. When I first heard of NEAR, I Google-searched "NEAR KSP" and got the Near future mod family.

Speed of sound isnt 0 m/s, its infinity m/s. Mach number is zero; not speed of sound.

Share this post


Link to post
Share on other sites
Speed of sound isnt 0 m/s, its infinity m/s. Mach number is zero; not speed of sound.

NEAR uses Mach 0/infinite speed of sound.

A while back, some people had suggested a drag model based on raycasting, pretending that incoming air moves in a straight line until reflected off a part. Ferram did a proof-of-concept to demonstrate the limits of that approach. The raycasting approximation roughly corresponds to the zero-speed-of-sound/mach-infinity case.

Share this post


Link to post
Share on other sites
do rockets still flip over if you move too far away from the prograde while in atmosphere

Yes, but they don't fly apart.

Which is small comfort because if your rocket's upside down the mission's probably not going all that well. :D

Share this post


Link to post
Share on other sites

I just moved from stock aerodynamic to this mod and it is FREAKING AMAZING. Building spaceplanes that is actually able to do something like haul cargo to orbit or even go to the mun, is very difficult, bordering unfeasible with stock aerodynamics. Now, launching an S2 widebody behemoth like this into orbit with substantial residual delta-V is a breeze. Thank you for the mod effort, keep it up!

Share this post


Link to post
Share on other sites

Hmmm. So this basically means no aerodynamic breakups? I still don't want to use either this or far because turning even a few degrees with either of these makes you completely flip out if still in atmosphere. If you do flip out, then breaking up does not matter because I have never managed to recover from a flip. Ah well, I still like the concept.

Share this post


Link to post
Share on other sites

Vectura: you get a choice: do you want parts' shape to matter? (i.e. spindly rocket with nosecone more aerodynamic than big squat flat thing). Or do you want mass, and mass only, to matter for drag?

If you do want shape to matter, then the flipouts will occur. They go hand in hand. If you don't want flipouts, then drag *must* be *only* proportional to mass.

Share this post


Link to post
Share on other sites

I'm curious, is ModStatistics still packaged with your mod? I don't see it listed on your OP, but it's listed on the ModStatistics forum post and I noted it was mentioned in your changelog as being added but not being removed.

Share this post


Link to post
Share on other sites

NEAR no longer includes ModStatistics. If you're wondering about other mods, you can tell because the OP was last updated after the date the new rules went into effect, because it no longer references ModStatistics as required by Majiir, or by checking the contents of the zip before installing.

Share this post


Link to post
Share on other sites

Hmm, my attempts at flying a plane with NEAR seem to run into sudden unplanned dis-assembly for no reason I can discern. Not that far from the runway, shortly after liftoff, speed seems not to matter, have done it at 100m/s if I take throttle back and the plane can reach over 175m/s easily if I don't take throttle back... So not sure why the plane is disintergrating, are there any logs that would help?

Share this post


Link to post
Share on other sites
Vectura: you get a choice: do you want parts' shape to matter? (i.e. spindly rocket with nosecone more aerodynamic than big squat flat thing). Or do you want mass, and mass only, to matter for drag?

If you do want shape to matter, then the flipouts will occur. They go hand in hand. If you don't want flipouts, then drag *must* be *only* proportional to mass.

I don't think that's the only 2 solutions. Someday I hope some one creates an aerodynamics model that uses shape and orientation in order to determine drag, but then applies that drag to center of mass. I think that would be an awesome combo of Stock and NEAR.

Share this post


Link to post
Share on other sites

Part center of mass? That's how it is now, in Stock and in FAR (with the effect I described). If you apply drag at vessel center of mass, then every vessel will have no stability at all--they will continue to point in whatever direction they are currently pointed in, no matter which way "the wind is coming from." Flying will be...kinda tough, if the plane doesn't try to head into the wind at all...

Share this post


Link to post
Share on other sites

@CattyNebulart: Then that means that you're going fast enough that aerodynamic forces are strong enough to break you up even in stock. Yes, logs would help:

Upload your entire output log (NOT ksp.log) to dropbox or something.

Windows: KSP_win\KSP_Data\output_log.txt

Mac OSX: Open Console, on the left side of the window there is a menu that says 'files'. Scroll down the list and find the Unity drop down, under Unity there will be Player.log Aka Files>~/Library/Logs>Unity>Player.log

Linux: ~/.config/unity3d/Squad/Kerbal\ Space\ Program/Player.log

Then I'll need a complete modlist, with version numbers.

@jmanidb: Yes, and it would be great! Command pod orientation would never forced to be blunt end first, so you can reenter at any orientation you like. The only reason that orientation is forced is by drag not being applied at the CoM, and in stock, that's accomplished by parachutes (even not deployed) having higher drag than capsules. You'd never have to worry about where you attached wings, because after all, with the center of pressure forced to be at the center of mass perpetually, there's no way to build an unstable plane! Of course, there's also no way to build a stable plane either, so you'll be sideslipping and pitching out of control with no way to right things, but hey, aerodynamic forces applied to CoM means only neutral stability, not actual static stability!

Oh, and funny thing about applying all the aerodynamic forces to the center of mass: without distributed forces, there is no aerodynamic damping. Now, that basically means that there is absolutely no chance that this aerodynamic system could ever stop a plane from tumbling! Of course, you could instead argue that wings remain magical special things that apply forces at their own location (for no apparent reason to the player) solely because that results in the outcome you want, but then you're setting up inconsistent physics to get a desired outcome. Inconsistent physics is bad game design and is confusing for players. Yes, this applies to stock aerodynamics (the bad game design comment), and I submit all of the players confused by why their spaceplanes-on-top-of-booster-rockets are unstable as proof that it confuses people; they have not considered that aerodynamic forces might be applied somewhere that would make the vehicle unstable because they were taught otherwise.

TL;DR: Your system makes everything worse. If turned into something like stock, it maintains the privileged physics nature of wings that confuses new users. This is a bad idea.

Share this post


Link to post
Share on other sites
Part center of mass? That's how it is now, in Stock and in FAR (with the effect I described). If you apply drag at vessel center of mass, then every vessel will have no stability at all--they will continue to point in whatever direction they are currently pointed in, no matter which way "the wind is coming from." Flying will be...kinda tough, if the plane doesn't try to head into the wind at all...

Talking about this, do you have plan to create a small PartModule that allow user to shift CoM during flight? so that command pods can set its CoM at center by default and shift the CoM right before they are going to reentry. I don't know if such technology exists in RL...

Share this post


Link to post
Share on other sites

It's in the latest RO. asmi gave me permission to use his module that does that (for BobCat's Soyuz); I tweaked it slightly.

Share this post


Link to post
Share on other sites
Talking about this, do you have plan to create a small PartModule that allow user to shift CoM during flight? so that command pods can set its CoM at center by default and shift the CoM right before they are going to reentry. I don't know if such technology exists in RL...

Such technology does exist IRL. You can use weights that could be shifted. Or there's the Curiosity method: Just before reentry they jettisoned via mortar a series of weights from one side. That caused it to come in angled the way Apollo did. (also steering automatically via RCS but that's not important right now). Then before the chutes deployed, another series of weights were ejected from the opposite side as the first set thus restoring center of mass back to its original position. And I'm sure that's not even exhausting all possibilities.

Share this post


Link to post
Share on other sites

Is NEAR the reason most of my spaceplanes fly AMAZINGLY smooth and well, but above a certain altitude, they become completely uncontrollable and flat spin or roll out of control or both? Or is this related to my plane design?

Share this post


Link to post
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this