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#2407250 - 12/24/07 12:52 AM Aerodynamics and flight model.  

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Benny Moore
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Hello,

How is the flight model going to work? Is it fluid physics, as Gennadich's unreleased simulator is supposed to be using, or simple vectors like in conventional simulators? If the latter, how many vectors are used?

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#2407798 - 12/24/07 11:27 PM Re: Aerodynamics and flight model. [Re: ]  

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Aces High II, as shown in this picture (http://hitechcreations.com/pyro/poweron01.jpg), uses thirty-two lift vectors, thirty-two drag vectors, four thrust vectors, and several weight vectors (or moments of intertia). It's the best flight model I've seen in any simulator. If it must be vectors and not realistic fluid phsyics (which, to my knowledge, hasn't yet been done in a P.C. flight simulator), the more vectors the better.

Gennadich's Knights of the Sky looks as though it will be using fluid physics, as seen in this video (http://www.youtube.com/watch?v=cnwz3WQfuWM). I'm unsure whether or not the airflow actually affects the wing here, but I hope so. If it does, then it should be the most realistic flight model yet.

I am very curious about how Jet Thunder is going to handle the aerodynamics. It will determine whether or not I buy Jet Thunder. I have no interest in simulators with simplified aerodynamics, using only a handful of vectors as the highly-overrated IL-2 series does. Flight model is far more important than avionics.

#2408227 - 12/25/07 10:04 PM Re: Aerodynamics and flight model. [Re: ]  
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 Quote:
I am very curious about how Jet Thunder is going to handle the aerodynamics. It will determine whether or not I buy Jet Thunder. I have no interest in simulators with simplified aerodynamics, using only a handful of vectors as the highly-overrated IL-2 series does. Flight model is far more important than avionics.


Interesting post, Benny More. It's very good to hear opinions from the market. It confirms what I've tought before: what is left of the flight sims audience is interested only in the whole nine yards - there is no midterm or cutting corners.

Well, our flight model is being largely re-worked by a fluid dynamics engineer - I'll forward your post to his email, and I'll post back here his answer.

Btw, what do you think of Austin Meyer's Blade Element theory?


-----
Jet Thunder Project
http://www.thunder-works.com
#2408247 - 12/25/07 11:14 PM Re: Aerodynamics and flight model. [Re: Dante-JT]  

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I'm very happy to hear that a fluid dynamics engineer is working on the project; this simulator shows a great deal of promise and I am very impressed that it is being done by independent developers. The technological demonstrations (particularly the Harrier's V.T.O.L. system) look fascinating and original. The only thing about the simulator that I can recognize from the videos as being clearly wrong is the cannon firing rate, which is far too low. I am sure that will be amended long before release.

I have mixed feelings about X-Plane. I own it and on one hand I am impressed by the concepts and the technology used, but on the other hand limiting it to ten calculations on each side of the wing does limit the accuracy of the simulation. Having flown in the real world Cessna 152s and, briefly, a Cessna 172, I can say that the Cessna flight model seems reasonably accurate in X-Plane. However, it does lack stability compared to the real thing. Also, the wind model isn't the best, and there are various other problems which I feel can be amended in time.

I am already advertising Jet Thunder to anyone who I think might be remotely interested, although I make sure they are aware that it's in development and may not turn out as well as hoped. Are there plans for a playable demonstration sometime before or after the simulator's release? I've noticed that aerial combat simulators tend not to have playable demonstrations, for some reason. And it's very hard drawing new people into games when there is no playable demonstration; few people trust another's judgement enough to buy sight unseen.

Speaking of advertising, do you have any plans for publishing? On one hand it would be great if it were self-published; you'd retain full control over your product. On the other hand, I can't see a game already in a niche market, and self-published in Argentina, becoming a commercial success. Might I suggest looking into Idea Games, the Independent Developers Association? This group, created to help independent developers self-publish (http://www.idea-games.com/index.php?option=com_content&task=view&id=52&Itemid=35), was begun by the Czechlosovakian developer of Operation Flashpoint, Virtual Battlefield System, and Armed Assault. I'd hate to see a duplicitous publisher like Ubisoft or Eidos take over such a promising project and do unpleasant things to it in the name of the almighty dollar.

#2412810 - 01/02/08 02:48 AM Re: Aerodynamics and flight model. [Re: ]  
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Below, in quotes, is the answer from the fluid dynamics engineer, John Cagle:

 Quote:
Benny Moore,

Please accept my apologies for a belated response, your letter caught me in the middle of my Holiday travels. I won't comment on the flight models of other simulations, it's simply not something I view as professional (although you are welcome to voice your own opinions). With that in mind, your notion of vectors contrasted to Fluid Physics should be rectified. An aircraft in flight is essentially a complex 3-D mechanics problem. Vectors are at the heart of all mechanics; Speed, Acceleration, Forces, and Moments (Torques) can only be expressed as vector quantities. Therefore, every simulation must use vectors at some point or another.

I think you are concerned with the simplifaction of physics into mathematical trends. For example, the concept of a Mass Moment of Inertia as a vector is flat out wrong. Newtons second law can be expanded to rotational behavior, and it's simplified version is: M=I*a. Where M is the sum of all External Moments (torques), I is the Mass Moment of inertia, and a is the Angular Acceleration. M and A are vector quantities which have identical directions. Given this, I must be a scalar quantity, because the dot product of two vectors is a scalar. Consequently, if the Mass Moment of Inertia were a vector, then torque would be scalar quantity.


 Quote:
This type of simplification will not be made in Jet Thunder, however, simplification is a necessity in the practical world. The trick is determining what is a reasonable simplification and what is not. If nothing were simplified, and true Computational Fluid Dynamics (CFD) were used, it would take minuets to hours to compute each frame. I am still early in the development process for Jet Thunder's physics, but I can tell you variables such as Reynold's Number, Lift Coefficient, Drag Coefficient, their related and dependant variables will be calculated according to the principles of Fluid Dynamics and Flight Mechanics every time the physics file is run (about every frame) for every independent surface on the aircraft. Right now, I am working on the A-4 and it has about 27 surfaces taken into account.
Hopefully this answered your questions. If you have any more, please feel free to ask me, I will be much quicker to respond in the future.

Best Regards,
John


By the way, thanks for the suggestion and link to Idea Games. Operation Flashpoint was great, commercial success, and done with a budget of just 600k dollars (according to Gamasutra's Post Mortem on it) - it's about 1/10 of the average budget of a game industry's typical action title, but it shows about 10 times more project scope than your average mass-appeal action videogame.

Ah, we won't be self-publishing only in Argentina, if we go this route, we must ensure worldwide spread, probably through a viral marketing campaign, banners and all paid out of our own pockets will be the rule of the day.

Last edited by Dante-JT; 01/02/08 02:49 AM.

-----
Jet Thunder Project
http://www.thunder-works.com
#2412822 - 01/02/08 03:16 AM Re: Aerodynamics and flight model. [Re: Dante-JT]  
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Benny have you ever flown the Su-25T in Lock On: Flaming Cliffs? I'm no engineer OR pilot, but it's by far the best 'feeling' sim FM I've ever flown. I'd be interested to hear your opinion of how it stacks up to your expectations of what a 'realistic' FM should be.

And Dante I am continually impressed by your dedication to getting Jet Thunder 'right'. I have been very impressed with the previews I've seen and your continual openness to community questions and suggestions is a welcome and refreshing change from most current sim development teams. I may have to buy 2 copies just to say thanks!!!


It doesn't matter how beautiful your theory is, or how smart you are, If it doesn't agree with experiment it is WRONG. ~Richard Feynman
#2412984 - 01/02/08 02:13 PM Re: Aerodynamics and flight model. [Re: Colt40Five]  
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A very interesting post here...

http://www.checksix-forums.com/showthread.php?t=141413

... about the Mirage III flying characteristics.

Worth to "babelized" for the dev team.

#2413371 - 01/02/08 11:10 PM Re: Aerodynamics and flight model. [Re: CHDT]  
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Colt40Five: Thank you very much for your words of support \:\) Indeed Su-25T in Lock On: Flamming Cliffs is my favourite sim FM ever, should be current sim industry's benchmark for sure.

CHDT: Thanks! I will give it a try in googletranslator!


-----
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http://www.thunder-works.com
#2413575 - 01/03/08 06:41 AM Re: Aerodynamics and flight model. [Re: Dante-JT]  
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Dont worry CHDT someone working with Dante has around 1500hrs Stick time on the Mirage III ... and a little DACT experience Mirage V Sea Harrier FRS1


Last edited by IvanK; 01/03/08 06:46 AM.
#2413924 - 01/03/08 07:05 PM Re: Aerodynamics and flight model. [Re: IvanK]  
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Given that Jet Thunder is a combat sim, I anticipate less attention being given to the flight models than a purely civilian flight sim, since there's radio chatter, ground units, combat AI, weapons and weapons systems, etc. to be done.

I'm an electrical engineer myself, though, and from the sounds of it, John Cagle knows what he's doing. I guess many flight sim teams just reuse what's been done by others and research "How to Code a Flight Model". However, from what John's talking about, he's back to first principles. Physics, number of data points, and reasonable linearization of equations between data points. The math can get very busy, though, and all those floating-point calculations can bog down the frame rate. It'll be exciting to see what multicore CPUs and physics coprocessors can do for us in the way of "physically real" games. While the calculations are pretty serial, they ought to eventually be completely off-loadable and run in parallel to the other game-threads.

OT: Not sure if John's read this - Div, Grad, Curl, and All That - but it's an excellent treatment of vector calculus from an "intuitive" point of view. A "must have" for any engineer, in my opinion. Gives some great physical insight into the complex calculations that can seem arcane and meaningless at times. It's been around forever and the second edition (mine, at my desk right now) is only 162 pages long.

Last edited by chronoPilot; 01/03/08 07:11 PM.

Not by accident does Genesis 3 make the father of knowledge a serpent - H.L. Mencken
#2414080 - 01/03/08 11:11 PM Re: Aerodynamics and flight model. [Re: chronoPilot]  
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IvanK: amazing pics!!! \:D Any chance of some of the SHAR celebrities (David Morgan, Sharkey Ward, Neil Thomas, Paul Barton etc) has been caught on camera in the above guncam photos?


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#2414108 - 01/03/08 11:54 PM Re: Aerodynamics and flight model. [Re: Dante-JT]  
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It was many moons ago Dante:) and on the day its just another piece of metal out in front not really a person. What I can tell you was these were taken around 12 months after the Falklands War. The RN was on a "Colonial tour" with the worlds "best fighter". Well the colonials with their French lady took it to the Harriers with vengeance. There was no doubt that a well flown R550 equipped Mirage was easily the equal of the Sea Harrier.

The scenario was different (to the Falklands) however it was totally Air to Air with both sides operating only 50nm from base (us the land the SHARS the boat). Both sides had good GCI. We didn't have the prospect of a 400nm trip home. It was a fair test of both types and crews. In the end the much maligned Mirage accounted for itself exceptionally well. The only real area the SHAR had over us was the front sector capability of the 9L, but this can be and was denied on most occasions. as to the mighty VIFF .... never saw it used once.

#2414174 - 01/04/08 01:28 AM Re: Aerodynamics and flight model. [Re: IvanK]  
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 Originally Posted By: IvanK
...as to the mighty VIFF .... never saw it used once.


David Morgan used it in the war, at page 212 in his book 'Hostile Skies' he describes how he has vectored the nozzles to the braking stop position to decrease his speed over a slow Pucara flying below, trying to get a AIM9L growl - VIFF means Vectoring In Forward Flight, which was exactly what he did in his description. \:\)


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#2414288 - 01/04/08 04:31 AM Re: Aerodynamics and flight model. [Re: Dante-JT]  
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VIFFING V Pucara thats a novel concept \:\)

#2414392 - 01/04/08 08:40 AM Re: Aerodynamics and flight model. [Re: IvanK]  
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LOL probably just better staying in the hover against that one IvanK!

#2414714 - 01/04/08 04:42 PM Re: Aerodynamics and flight model. [Re: SC/JG_Oesau]  
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It is worth mentioning that VIFF was a USMC invention IIRC and apparently the concept was viewed with a certain amount of scepticism in by the British. Therefore it is entirely possible that the technique was not standard operating procedure for them at that point.

#2414869 - 01/04/08 07:58 PM Re: Aerodynamics and flight model. [Re: Trident]  
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Remember the Harrier was fairly new then..


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#2415085 - 01/04/08 10:34 PM Re: Aerodynamics and flight model. [Re: joey45]  
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VIFFING was invented and implemented long before the Sea Harrier saw the light of day. There are two main versions of VIFFING. "VIFFING" and "Nozzling".

"VIFFING" is what most know of. Rapid movement of the nozzle lever towards the rear stop. This results in large loss of Airspeed and momentary increase in G. Good as a last ditch Guns defence manoeuvre. Negative aspects are that after it you are sitting there at exceptionally low IAS with little manoeuvre potential... but survived the guns attack.

NOZZLING is a technique typically used when trapped in lag and you cant quite get the nose on. small "tweaks" of the nozzle lever to raise the nose in an attempt to get a solution. You dont get many goes at nozzling as the resultant IAS loss results in reduced G capability, that cant be made up for with further nozzling.... is a IAS loss making spiral.

Good hard technical data is available and in Dantes hands on the magnitude of Flight path change and resultant performance loss that can be achieved by both methods.

#2416001 - 01/06/08 08:24 AM Re: Aerodynamics and flight model. [Re: IvanK]  
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Good IVANK

I can't wait for it....

#2420010 - 01/11/08 01:31 PM Re: Aerodynamics and flight model. [Re: GADGET]  

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That's fantastic news. I don't understand much of the mathematics but it's clear that this flight model is being taken seriously and looks like it'll be done right.

I have Lock On: Modern Air Combat, but unfortunately I was forced to refuse to buy Lock On: Flaming Cliffs because of the Starforce copy "protection." Thus I don't know how the Su-25T flies therein.

#2420131 - 01/11/08 03:09 PM Re: Aerodynamics and flight model. [Re: ]  
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your missing something good B.M.


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#2423603 - 01/16/08 04:50 AM Re: Aerodynamics and flight model. [Re: joey45]  

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Yes, I am. But I'm also missing something very bad.

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