ferram4

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

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This is not the case in game.

(I hope that is clear....Please ask if it isn't.....)

 

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Post the picture of your spaceship, give the speed, acceleration and altitude where the air-flow beats the engine power. Or better, give the craft-file.  Otherwise it will be REALLY hard to explain it to you.
I`ve been using FAR as long as I can remember, and I had to strugle to make my stock rockets work with it (aka.: 100% of my rockets would do an unplaned disassembly when doing the gravitational turn or simply would not point straight up after lift-off).
No, there isnt many things that are "badly modeled" in this mod. It is quite good modeled (if you look at the source file, it is so heavy in equations that it amazes me that the game can actually comprehend them).

Edited by Scoppio

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1 hour ago, Fizwalker said:

Bare with me for a bit. When you put your hand outside a window while traveling in a car, you experience lift from the deflection of the airflow deflected from your vector of travel. That's because your hand is being propelled forward by the car. Generally speaking once the car is at cruising speed, it is 1G. Equal force opposing the constant acceleration of the car. Now that is horizontal acceleration. That is what it is because the point of thrust is horizontal. Meaning it is along the surface of the Earth.

 

Now, when you launch a rocket in this game and mod, the atmosphere seems to behave in a similar fashion to sticking your hand out a window of a car. That is to say, that the horizontal travel is more important than the direction of thrust. I posit that horizontal force is less than the force applied by rockets along the direction the force is being acted upon. This isn't being modeled properly in my opinion.

 

It is my theory, that action upon an object going to orbit will find more force being applied to towards its direction of travel based on it's length. Meaning it will not be deflected off track by random atmospheric forces while a constant source of thrust is behind it.

 

Your theory is incorrect. Horzontal vs vertical vectors doesn't matter. As long as something is traveling through atmosphere, it will be affected by that atmosphere. The strength of the effect is going to change with the surface area of the object, especially how much of that surface is directed into the relative wind (angle of attack). You seem to understand that basic principle, according to your first paragraph.

Where you've lost me is in the second paragraph. There are no winds or random aero forces in KSP - any aero forces you contend with come from your own velocity and angle of attack.

If you want to fly a rocket in FAR, you have to shape it like a real-world rocket, and fly it like a real-world rocket.

Good luck. :)

Edited by theonegalen

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1 hour ago, Fizwalker said:

Bare with me for a bit. When you put your hand outside a window while traveling in a car, you experience lift from the deflection of the airflow deflected from your vector of travel. That's because your hand is being propelled forward by the car. Generally speaking once the car is at cruising speed, it is 1G. Equal force opposing the constant acceleration of the car. Now that is horizontal acceleration. That is what it is because the point of thrust is horizontal. Meaning it is along the surface of the Earth.

Inasmuch as this means anything, it's wrong. There's no particular reason to suppose the force will be "1G", assuming that is meant to mean 9.8 N per kg of hand. Once the car is at cruising speed, there is no "constant acceleration"; there's no acceleration at all if it travels in a straight line.

Your complaint is also very unclear but:

If the rocket is turning end for end, that's because there's more rocket (drag-wise) in front of the centre of mass than behind it, so as soon as it gets slightly off-axis it keeps turning. This is very likely when a first stage is dropped, when suddenly a large empty section behind the centre of mass is lost, eliminating a lot of drag at the rear but hardly moving the centre of mass.

If the rocket seems to drag across the landscape unexpectedly, this may be down to Coriolis effects or confusion between surface-relative and orbital-relative measurement.

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3 hours ago, Fizwalker said:

This forum doesn't allow the posting of pictures, so I cannot post a picture of my craft (Not going to a third party just for a picture, sorry).

3 hours ago, Fizwalker said:

Edit: Not going to a 3rd party, so yes I understand that I can post to Imgur.....I won't because I  do not wish to go to a 3rd party.

If you refuse to post a photo then I assume you also will refuse to post a link to a craft file. If you refuse to do either of these simple things, then I refuse to try and help. Due to how much one can customize a craft in KSP, a simple text description is not enough to figure out what your problem is. 

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4 hours ago, Fizwalker said:

Edit: Not going to a 3rd party, so yes I understand that I can post to Imgur.....I won't because I  do not wish to go to a 3rd party.

It doesn't have to be imgur. Just throw an image up somewhere you have access to a webhost and then click the "Insert other media" button down in the bottom-right of the post editor. paste the URL to the image in there and it will show up embedded in the thread. Or just post a link to the image.

Really, you're not going to get any sort of quality help without us seeing what your rocket looks like. Post a gif or a video if you like that better.

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On 5/23/2017 at 4:27 AM, Mighty1 said:

I reported this issue a while ago and thought that it was a dev version problem but it is happening again.

So, a clean install, only Modular Flight Integrator 1.2.4,ModuleManager 2.7.6 and FAR De Laval installed. I landed a stock Gull in the water some 15 km off the KSC in the water, launch another gull and approach. When I get to cca 200 m distance the game crashes. Sometimes there is no crash but the targeted vessel just vanishes and lands on the sun accoring to the tracking station. I tried the same approach while landed and nothing happens and in orbit there are no issues also. It appears it is a water thing.

Here is the crash log https://www.dropbox.com/s/ikrh70zh7sxyfdi/2017-05-23_093008.rar?dl=0

 

Get the most specific reproduction steps you can, ideally ones that create the issue reliably all the time (if you can't, most of the time) and then post a copy of the save file that causes this.  Post it all on Github so it's easier to track and I'll look into it.

Probably something coincidental though.  Most crashes are memory related and I'm not sure how this could result in some memory access or memory allocation error.

17 hours ago, Angstinator said:

I have encountered a problem running this mod with Procedural Fairings (which is FAR-compatible according to its OP).

One of my probe designs has a shrouded midsection which contains solars, radiators and scientific instruments and is meant to be exposed after leaving the atmosphere. Jettisoning the fairing works perfectly fine, but the probe's solars and radiators refuse to deploy, reporting they are in a stowed state. This does not occur without FAR.

I would like to know possible causes of and, if available, solutions to this problem.

 

This message has also been posted to the Procedural Fairings thread.

Post a copy of the craft file and make a Github issue for it.  In addition, if other mods are required for this craft, simplify it down to the point where only the mods absolutely necessary to cause the issue are involved and then list every single mod needed.  If you don't do this, I can't guarantee that I can reproduce the issue considering how variable designs can be.

7 hours ago, Fizwalker said:

It is my theory, that action upon an object going to orbit will find more force being applied to towards its direction of travel based on it's length. Meaning it will not be deflected off track by random atmospheric forces while a constant source of thrust is behind it.

Your theory violates conservation of angular momentum as well as basic Newtonian relativity, because boiled down to its basics, it says, "so long as there's a high enough force in this special direction, any forces in a different direction placed anywhere else will not cause the object to rotate."  Fortunately for us, physics is more completely consistent than that, and any forces applied anywhere will cause the vehicle to accelerate and rotate, regardless of which direction or the magnitude of any other forces.  Hooray for simple vector addition.

Anyway, the problem is that your rocket is aerodynamically unstable.  All rockets, unless they have very silly large fins will be aerodynamically unstable.  This is not because of drag, but because of lift: the nose of the rocket produces a huge amount of lift when the rocket is angled off of its velocity vector, even slightly.  As it turns out, the lift produced by the rest of the rocket is much smaller than the lift produced by the nose, so more lift is produced ahead of the CoM, so it becomes unstable.  So the standard solution is careful control + active control through thrust vectoring to keep this under control.  You're not flying through a hurricane, you're just manually flying through the same stuff that real rockets do, but probably with a sub-optimal design for handling the aerodynamic forces.

So, without seeing your rocket (seriously, post a picture; being unnecessarily stubborn about this doesn't help), I'll make a big guess: it's got a huge fairing at the top, and not much pitch and yaw control.  So lots of lift from the nose, not much thrust vectoring to counter it.  So either add more thrust vectoring control, add giant fins, or make the fairing smaller.

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3 hours ago, ferram4 said:

the nose of the rocket produces a huge amount of lift when the rocket is angled off of its velocity vector

Are some fairing shapes better than others? I would expect shape would matter, but one thing I've learned from you is my intuition about aerodynamics is generally wrong.

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So, I have been away from home, on a military exercise for the past couple of months, and the only entertainment I brought with me was a crap ton of movies and KSP. With regards to KSP, I've had to remove about half of my parts mods, and all of the graphical enhancement mods for my poor old Asus G75 to keep up. 

I really really love my huge space planes, and I was getting a little more frustrated with it each time I played with one of them... until last night when I saw FAR was updated!! I tethered my phone (already over my data limit), downloaded and installed it as soon as my shift was over... it took me a while to re-adapt my space planes back to FAR compatibility, but OH MAN when I got it done, the fun I had!! I played KSP until almost midnight inside a crappy leaking modular tent buffeted by high winds and horizontal rain... with a smile on my face.

Thank you ferram4, I truly appreciate your work.

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11 hours ago, ferram4 said:

Your theory violates conservation of angular momentum as well as basic Newtonian relativity, because boiled down to its basics, it says, "so long as there's a high enough force in this special direction, any forces in a different direction placed anywhere else will not cause the object to rotate."  Fortunately for us, physics is more completely consistent than that, and any forces applied anywhere will cause the vehicle to accelerate and rotate, regardless of which direction or the magnitude of any other forces.  Hooray for simple vector addition.

Anyway, the problem is that your rocket is aerodynamically unstable.  All rockets, unless they have very silly large fins will be aerodynamically unstable.  This is not because of drag, but because of lift: the nose of the rocket produces a huge amount of lift when the rocket is angled off of its velocity vector, even slightly.  As it turns out, the lift produced by the rest of the rocket is much smaller than the lift produced by the nose, so more lift is produced ahead of the CoM, so it becomes unstable.  So the standard solution is careful control + active control through thrust vectoring to keep this under control.  You're not flying through a hurricane, you're just manually flying through the same stuff that real rockets do, but probably with a sub-optimal design for handling the aerodynamic forces.

So, without seeing your rocket (seriously, post a picture; being unnecessarily stubborn about this doesn't help), I'll make a big guess: it's got a huge fairing at the top, and not much pitch and yaw control.  So lots of lift from the nose, not much thrust vectoring to counter it.  So either add more thrust vectoring control, add giant fins, or make the fairing smaller.

Hey Ferram, totally agree, but perhaps it might help to point out that there is a positive feedback loop involved. As a small amount of lift develops that pushes the nose to one side, that increases the angle of attack. So more lift. Which further increases the angle of attack. Etc. Positive feedback loop. To counter it, a bigger negative feedback loop is necessary. Thrust vectoring, RCS, steerable tailfins, etc. can supply this, if their control authority is sufficient.

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42 minutes ago, mikegarrison said:

Hey Ferram, totally agree, but perhaps it might help to point out that there is a positive feedback loop involved. As a small amount of lift develops that pushes the nose to one side, that increases the angle of attack. So more lift. Which further increases the angle of attack. Etc. Positive feedback loop. To counter it, a bigger negative feedback loop is necessary. Thrust vectoring, RCS, steerable tailfins, etc. can supply this, if their control authority is sufficient.

You can already do this with FAR, it's called longitudinal instability. You get this when your centre of gravity is too far aft (with a conventional aircraft design).

Also note that if you raise the nose you don't necessarily increase lift, but alpha. Depending on your position in the CL-alpha graph, it will result in an increase or decrease of lift. If I understand your suggestion correctly you basically ask Ferram to add code that reduces the realism, and makes every plane un-flyable.

From a humble pilot, I am sure the engineers in this forum will be able to explain it much better!

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2 hours ago, Ricovandijk said:

You can already do this with FAR, it's called longitudinal instability. You get this when your centre of gravity is too far aft (with a conventional aircraft design).

Also note that if you raise the nose you don't necessarily increase lift, but alpha. Depending on your position in the CL-alpha graph, it will result in an increase or decrease of lift. If I understand your suggestion correctly you basically ask Ferram to add code that reduces the realism, and makes every plane un-flyable.

From a humble pilot, I am sure the engineers in this forum will be able to explain it much better!

Well, the thing is, it wasn't a suggestion for Ferram to change his mod. It was only a matter of trying to help him explain to that other fellow how stability works.

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11 hours ago, taniwha said:

Are some fairing shapes better than others? I would expect shape would matter, but one thing I've learned from you is my intuition about aerodynamics is generally wrong.

As always, it's a compromise.

A nice slender von Karman ogive is the best drag-wise, but is going to produce a lot of body lift and is a pain to manufacture.

A slender cone is easier to manufacture, but is worse drag-wise and will still produce tons of body lift.

A bi-conic is a good compromise drag-wise between the ogive and cone, but still the body lift issue.

A flat, unfaired end is very good at minimizing the body lift, but is terrible for drag purposes.  Still bad from a stability perspective, probably likely to break up under drag.

More stout versions of everything have more drag, less body lift.  It always just turns into what you can get away with.  There's enough variety in fairing shape that I don't think that the specifics of shape matter too much in the grand scheme of things, at least for rockets.  For planes though, von Karman ogive because drag is so much more important.

3 hours ago, mikegarrison said:

Hey Ferram, totally agree, but perhaps it might help to point out that there is a positive feedback loop involved. As a small amount of lift develops that pushes the nose to one side, that increases the angle of attack. So more lift. Which further increases the angle of attack. Etc. Positive feedback loop. To counter it, a bigger negative feedback loop is necessary. Thrust vectoring, RCS, steerable tailfins, etc. can supply this, if their control authority is sufficient.

I thought it was implied with lift being caused by going slightly off axis and it being unstable, but yes, that's the more explicit form of what's going on.

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2 hours ago, Tricky14 said:

So yeah I guess KSP updated?

So yeah I guess you're asking when FAR will update?

The answer to that is whenever ferram feels like it. If FAR is important to you, just stay on 1.2.2 until he updates.

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17 minutes ago, TheRagingIrishman said:

1.3 came out yesterday

Oh really :o

Well then, good luck ferram

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1 hour ago, TheRagingIrishman said:

So yeah I guess you're asking when FAR will update?

The answer to that is whenever ferram feels like it. If FAR is important to you, just stay on 1.2.2 until he updates.

You're not in the least bit thrown off by the fact he only *just* released 1.2.2 two days ago?

I'm not complaining, I'm just hating this kind of luck right now. There may not be a difference.

Edited by Tricky14

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15 minutes ago, Tricky14 said:

I'm not complaining, I'm just hating this kind of luck right now. There may not be a difference.

*pats pats* That's KSP for you. It's been this way for a long time now!

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Honestly, aside from the localization (which admittedly is a big thing for those who speak those languages), there isn't really a lot of stuff in 1.3 anyhow. I'm fine with staying on 1.2.2 for a while.

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4 hours ago, Maeyanie said:

Honestly, aside from the localization (which admittedly is a big thing for those who speak those languages), there isn't really a lot of stuff in 1.3 anyhow. I'm fine with staying on 1.2.2 for a while.

Well, they did fix runways... Did you check if FAR got broken though?

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8 hours ago, m4ti140 said:

Well, they did fix runways... Did you check if FAR got broken though?

I just installed the latest FAR on a fresh 1.3 install alone, no other mods. The aerodynamics tweaks appear to work, but the interface doesn't show. Might be an easy fix. 

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Narf!  Love the "better late than never" part,   What I can't believe is a whole version of KSP went without one of it's Big 10 mods pretty much until the next version was out months later...   What happened?

Oh well,  best thing thats happened in a while,   cheers Ferram for all da hard work that goes into thish masterpiece ^_^

Edited by GorillaZilla

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