Wolf_rt

Heres Mine. The KX-10 download KX-10

For whatever reason, the engine is reaching its stated thrust at sea level now, with the fresh install and new model. No idea what would have changed... It must be an aerodynamic issue. I'm not sure what reference area refers to, but it is stated at 84.5m2 cd is 0.25 at mach 1. The model is actually around 75% of the size of the real thing. I have posted in the FAR thread, as im beginning to think that is where the issue lies.

Ok, i have been having a lot of trouble getting my F-104 replica to behave as expected with FAR, AJE, and B9 installed. Originally i though it was an issue with the thrust the J79 engine was producing due to the AJE mod. However the more i have looked into it, the more it seems like that is behaving properly. This is the beginning of the conversation on the AJE thread http://forum.kerbalspaceprogram.com/threads/70008-0-90-Advanced-Jet-Engine-v2-0-4-Apr-10?p=1833343&viewfull=1#post1833343 In the end, i decided that the thrust i am getting of ~80KN at sea level at Mach 0.5 and 20KN at 10000M should be correct. However the F-104 should be able to do Mach 1.2 at sea level, and Mach 2 At 10000M. As it stands, it can do Mach 0.95 up to 10000M as the thrust falls away to 20KN due to the AJE mod. It does not seem to be able to go above Mach 1 though. I have found two figures for the cd of the real F-104. 0.017 (no lift) and 0.048 on wikipedia. The in game model has a cd of 0.011, rising to 0.25 at Mach 1 then falling to 0.023 at Mach 1.5 (using a larger engine to get to that speed) This pic shows it maxed out at 10000M, Note that the angle of attack is wrong due to the cockpit being angled, the actual AOA of the wings is 1-2deg i believe. Note this is a fresh install with only FAR, AJE, B9, Tweak Scale, Procedural Tanks and KJR installed via CKAN. Tweakscale has been used on all of the stock wings and control surfaces. The current version of the plane shown above, uses no part clipping, and the weight is ~6000KG dry, as per the actual aircraft. Although i noticed this model is actually around 75% scale.

Cheers for your help.... For what its worth, a thrust of ~20KN at 10000M seems reasonable, im just not sure what is stopping the plane behaving as expected... The cd does rise to around 0.03 at Mach 1, then falls to around 0.022 at mach 1.5... Perhaps it is more an issue with FAR? Wiki puts the F-104 cd at 0.048 http://en.wikipedia.org/wiki/Drag_coefficient Where as another source i found put it at 0.017 (no lift) Its got me stuffed....

No other mods than those stated, all latest versions, installed with CKAN. plane flies at an AOA of around 2deg in general. Inlets are aligned. Current design uses the stock radial inlets, but i have tried all the others with no effect. The area rule is implemented somewhat, as the plane is slightly narrower in the center of the fuselage where the wings are, and fuselage tapers further at the tail. The cd does rise to 0.03 around Mach 1 though. Not sure what i could do to make it more slippery though. It should be able to hit Mach1 with 52KN of thrust (military power) It will basically do this at sea level (ie, there is 50KN of thrust available at sea level, and i can hit M 0.95) any increase of altitude absolutely kills it though. I understand that kerbin is different to earth, but i thought this mod was to add realism? what is that realism measured against if i cant take this 'as realistic as possible' plane to any appreciable altitude without thrust dropping way more than in RL? If i use the J58-P-4, i need around 55KN of thrust to reach Mach 1.9 at 10000m

The issue is, i cant seem to get a model that has the same cd as it real life counterpart, the same weight, and the same thrust, to behave anything like it should. The F-104 should be able to do at least mach 1.9 at 10000m At the moment, is is only capable of Mach 0.95 at 3000m, and by the time you reach 10000m the J79 is only making around 20Kn of thrust, and the plane has slowed to Mach 0.4, no matter how gentle the ascent. The J58-P-4 seems to be able to deliver the correct flight profile, but it delivers over 200KN at ground level, and 90KN at 10000m The J79 never reaches its stated thrust of 79KN, and falls massivly as soon as altitude is gained. The J79 is the correct engine for the F104, so im wondering what has happened to the realisim, if everything is correct. This has all been recreated on a fresh install, with FAR, AJE, B9, Tweak Scale, Procedural Tanks and KJR. I have made a new plane from scratch with no clipping.

ThorBeorn, there is defiantly something going wrong... i uninstalled AJE and B9 and i can still only get 50% thrust from the stock turbojet. There was an issue with drag as you mentioned, but i fixed it and the cd is now identical to the real plane, see edit in last post. I am installing a fresh copy with only FAR and procedural tanks, to asses the stock turbojet. I will then add AJE, to see if it is some conflict.

So i have been trying to make an F-104 with the J79 turbojet. I think there is something wrong with the thrust i'm getting. I wasnt actually aware that i had AJE installed... CKAN must have helped me out there...lol, i origionaly asked this question in the B9 thread, thinking it was an issue with that. I am using FAR and B9. the model i have made is the correct weight (6000kg dry) and the J79 supposedly supply's the correct amount of thrust (79KN) However it just wont go fast enough, or climb... On takeoff thrust reaches 62Kn At very low altitude flying level, thrust reaches almost 70KN at about Mach 0.45 As soon as i initiate a gentle climb at 10deg or less, thrust rapidly falls of (along with airspeed) You can see here, at a rate of climb of under 15m/s thrust has dropped to 40KN by 3000m At this point i have to level out, or the thrust will continue to decrease to around 20KN, at which point i fall out of the sky. Even after leveling out though, the thrust doesn't recover very fast, and i cant get airspeed above Mach 0.5... the plane eventualy runs out of fuel without thrust ever going over 50KN Anyone know what is going on here? The plane should be able to hit Mach 1 with only 55KN of thrust. I thought these engines were balanced with FAR & realistic performance specifically in mind? Is this a bug or a conflict? or some other issue? EDIT: So i have made some progress by reducing the drag of the craft. in the photos above the cd was 0.058 now it is a 0.02 very close to the actual F-104 at 0.017 This allows the aircraft to get up to 100KN of thrust at sea level, which quickly pushes it to Mach 0.95, however as soon as i initiate a climb, the thrust drops massively, and i'm still stuck at the 3000m ceiling. where thrust drops to 40KN, and i either dive to regain thrust, or climb further and thrust drops below 20KN.

@gilfo: its a struggle to get things to attach to the nodes, you basically have to do it before you attach the docking bay to anything else... So i have been trying to make an F-104 with the J79 turbojet. I think there is something wrong with the thrust i'm getting. I am using FAR and B9, (obviously) the model i have made is the correct weight (6000kg dry) and the J79 supposedly supply's the correct amount of thrust (79KN) However it just wont go fast enough, or climb... On takeoff thrust reaches 62Kn At very low altitude flying level, thrust reaches almost 70KN at about Mach 0.45 As soon as i initiate a gentle climb at 10deg or less, thrust rapidly falls of (along with airspeed) You can see here, at a rate of climb of under 15m/s thrust has dropped to 40KN by 3000m At this point i have to level out, or the thrust will continue to decrease to around 20KN, at which point i fall out of the sky. Even after leveling out though, the thrust doesn't recover very fast, and i cant get airspeed above Mach 0.5... the plane eventualy runs out of fuel without thrust ever going over 50KN Anyone know what is going on here? The plane should be able to hit Mach 1 with only 55KN of thrust. I thought these engines were balanced with FAR & realistic performance specifically in mind? Is this a bug or a conflict? or some other issue? EDIT: So i have made some progress by reducing the drag of the craft. in the photos above the cd was 0.058 now it is a 0.02 very close to the actual F-104 at 0.017 This allows the aircraft to get up to 100KN of thrust at sea level, which quickly pushes it to Mach 0.95, however as soon as i initiate a climb, the thrust drops massively, and i'm still stuck at the 3000m ceiling. where thrust drops to 40KN, and i either dive to regain thrust, or climb further and thrust drops below 20KN.