MPJayActually the GE/RR/Allison F136 engine as mentioned by Rolls Royce to Wired will be significantly higher in thrust than the Pratt F135 apparently.
http://www.wired.com/news/technology/0,1282,54143,00.html
Wonder if the lift shaft, clutch and gearbox will tolerate that.
MPJayI remember reading that years ago, they also made a prototype purpose built parasite fighter the Goblin, looked llike an aluminum pumpkin with wings, evil handling POS.
MPJayI have that documentry on VHS, it was supposed to be a ramjet powered missile, nuclear powered, they had problems with fuel rod erosion. The air fed into the test models was from large compressed air tanks, it was a whole farm of tanks they built to feed it. The reactors were assembled remotely and then taken by a specially constructed rail line to the test site. But as you said ICBM’s rendered it obsolete.
MPJayThe F-15 can sprint to Mach 2.5, which is a completely different animal than cruising for over an hour at Mach 3.17. Heat is a big issue.
MPJayYeah, the Israelis tracked “wet leased” Foxbats from Egypt or Libya clocking that, flown by scared ****less Russians of course. They didn’t know whether they were gonna make it back or not before the engines melted.
MPJayThat’s been there for ages…….however i have that manual in adobe acrobat form. 108 megs of glorious Mach 3 goodness. Looks like you read my post on ATS there, i posted that link over an arguement tonight on what the top speed was 😉
MPJayYeah, but my point was useful speed of each, and efficiency, F-15 has to use a LOT of fuel to match the Raptors cruising speed while carrying a warload.
MPJayThat speed is in a clean configuration, an operational pilot wouldn’t see anything near that. The F/A-22 is faster using military power while carrying 8 AAM’s than the Eagle is in full afterburner while carrying 4 Sparrow/AMRAAM + 4 Sidewinders. That’s from a chart the AF published years ago giving relative capabilities of the Eagle and its replacement.
MPJayThe E/F Hornet is not a parity replacement for the Tomcat, but i daresay its more reliable, the Tomcat was horrendous for maintainance man hours. Do a little research on the B-2 for instance, if you look down the intakes of the B-2 you’ll see those engines quite plainly and nobody says it has an RCS issue.
MPJayGo to the contractor site and you’ll see videos of current Russian SAM systems in action, i don’t have the site addy handy with me but i do have the vids i downloaded. Pretty spectacular stuff.
Found a video link, enjoy.
MPJayThe YF-23’s engine intakes similarly were serpentine, and in each aircraft the ducting has some radar absorbant properties that paint also used to reduce todays fighters RCS. The F-117A has straight ducts but had a grid the dimensions of which are smaller than typical tactical radar wavelengths, so in effect acts like a solid face barring radar from the engine face. Have a good look at the front of a Raptor and an F-15 or F-14, look right in there you can see the Tomcats and the Eagles are minimally inset towards the centerline, but there’s no direct line of sight at all between the entry of the inlet and the engine face of the Raptor.
Your other preferred topics, the F-35, now that’s a whole new kettle of fish there that’s for sure, it will replace the old A/C Hornets, the EF Hornets will be a bit of a downsized replacement for the Tomcat, improved performance AMRAAMs will go some way to being a Phoenix missile replacement but the Buffalo is dead when the Tomcat goes to the boneyard.
MPJayover G, your statements on what makes a low observable aircraft don’t make a lot of sense at all. What difference is there that its a high winged aircraft? It’s wing and tail planforms are edge aligned with the intake lips, the control surface junctions are catseyed, side surfaces, vertical tail surfaces are angled well away from vertical, its the 90 degree angles that are an absolute no no with RCS. The intakes are not directly in line with the engine face they sweep upwards and inwards, where have you been getting such incredibly wrong information?
During early EMD RCS testing they reduced the surface apex count of access panels to fix a slight signature issue and it worked, coatings technology has improved and it is beatings its specification RCS figures by about 5%
As for the fuel system being used to trim the CoG around the CoL that’s a given, in cruise flight if possible they don’t want positive tail surface trim, that causes drag, during maneuvering flight they want a slight negative trim so instead of pushing the tail around the pitch axis, the tail “catches” the overrotation and is slightly trimmed down itself to provide lift. It’s been done that way since the F-16, the inititial kick gets it moving and the fly by wire keeps the machine from diverging in the pitch axis. Classic pitch unstable flight laws.
MPJaySens, right from USAF they state the empty weight is “in the 40 thousand lb class”
http://www2.acc.af.mil/library/factsheets/fa-22.html
They lost quite a bit of internal volume normally used for fuel specifically because of the internal weapons bays, and to improve supersonic drag the wing thickness/chord ratio is not like an Eagles, a large wing yes, but not very deep. In reprofiling the wings from the YF to the EMD production configuration they reduced it even further. Thickness/chord ratio is 5.92 at root, 4.29 at tip. Each wing carries more fuel yes, but not proportionally more due its size. Have you seen the CAD model of the Raptor, how little space there is inside for fuel? I recorded a tv show which for 5 seconds showed just the fuel tanks and for a plane its size they’re limited in size. A couple saddle tanks that reside beside each engine, a smallish space above the intake ducts and the largest one sitting behind the cockpit going back to just before the inlet ducts converge. You’ve got internal gun, oxygen and nitrogen generation equipment, the heat exchanger behind the cockpit sitting on the fuel, hydraulics, databus lines everything affected the amount of fuel they were able to cram into it. It certainly doesn’t have the internal fuel capacity of a Flanker. Almost 2 tonnes less fuel. That disadvantage IS offset by far superior aerodynamics since it runs in a clean config except in very long duration flights.
So yes, it will be reliant on tankers for some missions, just rather less than other aircraft on internal fuel only.
I’m not a basher by any means, its the best fighter all round in the skies currently and probably for some time as a package, it just doesn’t have everything people on the outside would want it to have……yet. Wait till they transition more IHPTET technologies into the engine side for better fuel economy.
Here is a typical bulkhead of a Raptor showing how much area inside the Raptor at that point consists of intake duct, main weapons bay and side bays, this is a small picture of one of the main loadbearing bulkheads.
http://content.miw.com.sg/LifeStyle/Military/Images/20040611_combat05.jpg
It is SOMEWHAT misleading, some cross sections of the plane have more free volume, some are like this, its a very tightly packaged aircraft.
MPJaybring_it_on, during the competition for the engine for the ATF program which became the Raptor, the YF120 lost, and it was a much more advanced engine. It was variable cycle, the bypass ratio, which is the ratio of air going through the core and burned and that going around the core to cool and add mass to the airflow exiting the back of the engine was somewhat changable, it didn’t use a powered mechanism to do this, doors were aerodynamically opened or closed based on engine airflow pressures. At a low speed it operated at a bypass ratio around that of today’s F119, at supersonic speed the bypass closed leaving it to operate much like an old turbojet, much more efficient at supersonic cruise than an engine like an F100 or F110. That technology continues to be developed jointly by GE and Allison Advanced Developments in the IHPTET program proposing to use a core driven fan stage to supercharge the air going down the fan duct improving performance in many ways. The IHPTET developed technologies for the F135 engine and it will continue to develop new ones to transition into it and the F119 engine, older engines and civilian engines as well, improving thrust to weight, fuel economy and other factors. GE and Allison are developing a derivative of the YF120 called the F136 for F-35 use, a situation similar to when PW had a monopoly on F-15 and F-16 aircraft and ran into troubles big time. Competition improves the breed, even if PW develops a reliable engine, which from what i’ve heard it is, the newer technology of the F136 will be a compelling asset by USAF planners, its maximum output as stated by Rolls Royce, who owns Allison is over 50 thousand pounds of thrust. It may be downrated to improve life, but it will have better thrust growth compared to the F135, more margin as the aircraft ages.
MPJayTry the Breguet range equations, the emepty weight of the Raptor is 42974 lbs and it has 18348 lbs of internal fuel. It’s empty weight is not in the 30 thousand pound class, the USAF stated years ago that in the sacrifice to have internal weapons carriage it came with a 10 thousand pound weight penalty. The empty weight of an F-15C is generally regarded as 28600 lbs or so, a large difference in empty weight, and the Raptor only carries ~5000 lbs more fuel internally than an F-15C. It will fly differently than an Eagle, most of its mission will be subsonic, but the actual combat will be in supercruise mode to get the most launch energy into the AMRAAMs and it will leave the combat area when its weapons are expended using supercruise until its in a safe position to go back to subsonic cruise home. The real key to the Raptor is sensor fusion, to see what’s around it and enable the pilot to manage his energy state to best handle offensive actions, and defensive actions.
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