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  • MisterQ
    Rank 5 Registered User
    • Jan 2008
    • 475

    #81
    Originally posted by Scooter View Post
    Let's see supersonic performance and cooler thrust in the vertical......Sorry, but the numbers alone would disagree with your accessment.

    Supersonic performance has nothing to do with the engine and everything to do with the airframe, the F135 engine + lift fan is what I'm talking about, adding weight to create thrust which can only be used for lift, whersas a F135 changed from a 0.2 bypass to a 1.2 bypass using a pegasus style main fan would generate roughly 51000lbs of dry thrust (given the current estimates and released info on the F135 of roughly 28000lbs) with some simple lightweight ducting it could also be used to provide thrust in level flight while maintaining low RCS (actually easier with a low RCS airframe due to the layout) and you can still use the same 3 bearing pivoting tail and afterburners (afterburning 3 nozzle pegasus varients have existed for more than 20 years) giving 56000lbs or so (again using released data from PW on the F135), and the weight penalty for the ststem would probably be much lower than the lift fan, gearbox, ductwork and doors of the current F-35B system.

    Get it now?

    Comment

    • Distiller
      Talent on Loan from God
      • Oct 2003
      • 4760

      #82
      Originally posted by MisterQ View Post
      Supersonic performance has nothing to do with the engine and everything to do with the airframe, the F135 engine + lift fan is what I'm talking about, adding weight to create thrust which can only be used for lift, whersas a F135 changed from a 0.2 bypass to a 1.2 bypass using a pegasus style main fan would generate roughly 51000lbs of dry thrust (given the current estimates and released info on the F135 of roughly 28000lbs) with some simple lightweight ducting it could also be used to provide thrust in level flight while maintaining low RCS (actually easier with a low RCS airframe due to the layout) and you can still use the same 3 bearing pivoting tail and afterburners (afterburning 3 nozzle pegasus varients have existed for more than 20 years) giving 56000lbs or so (again using released data from PW on the F135), and the weight penalty for the ststem would probably be much lower than the lift fan, gearbox, ductwork and doors of the current F-35B system.

      Get it now?
      You will have a very hard time getting a 60in turbofan to fly supersonic within the duct length limitations of a tactical fighter. The lower your cross-section, and the higher your inlet-area/thrust index the easier it is to go supersonic.

      A key point - at least in my mind - why they chose X-35 over X-32 was, that the whole VTOL-complex really is an add-on and does not interfere with the basic layout of the airframe, meaning even if the B is dropped, the other versions are still fine and will give a more or less decent fighter (with some tweaking). The X-32 was in many ways a more interesting design, but too VTOL- and attack oriented and not enough fighter.
      Last edited by Distiller; 24th April 2008, 02:33.
      "Distiller ... arrogant, ruthless, and by all reports (including his own) utterly charming"

      Comment

      • eagle
        Rank 5 Registered User
        • Jan 2000
        • 2352

        #83
        Originally posted by MisterQ View Post
        Supersonic performance has nothing to do with the engine and everything to do with the airframe, the F135 engine + lift fan is what I'm talking about, adding weight to create thrust which can only be used for lift, whersas a F135 changed from a 0.2 bypass to a 1.2 bypass using a pegasus style main fan would generate roughly 51000lbs of dry thrust (given the current estimates and released info on the F135 of roughly 28000lbs) with some simple lightweight ducting it could also be used to provide thrust in level flight while maintaining low RCS (actually easier with a low RCS airframe due to the layout) and you can still use the same 3 bearing pivoting tail and afterburners (afterburning 3 nozzle pegasus varients have existed for more than 20 years) giving 56000lbs or so (again using released data from PW on the F135), and the weight penalty for the ststem would probably be much lower than the lift fan, gearbox, ductwork and doors of the current F-35B system.

        Get it now?
        Supersonic performance has lots to do with the engine. Look at the Harrier. Its engine needs a huge (for fighter standards) bypass ratio to produce lots of thrust at the front of the engine. And theres basically no intake duct at all. Not good for supersonic flight.
        The F-32 "solved" the problem with that ugly intake at the front which allowed to mount the engine as far ahead as needed. And still it could barely take off without any weapons load and stuff like intake lip, gear and weapon bay doors.
        edit: Top speed of the F-32 would have been interesting. I bet its much lower than for the F-35 thanks to the engine, intake and thick wings which hold all the fuel.
        Last edited by eagle; 24th April 2008, 03:15.
        How can less be more? It's impossible. More is more.
        Yngwie Malmsteen

        Comment

        • MisterQ
          Rank 5 Registered User
          • Jan 2008
          • 475

          #84
          F-35B has the lowest internal fuel capacity due to the lift fan, and as for the intake duct cross section, the X-32 duct is not all that much larger than the 2 ducts of the F-35, plus the pegasus layout wouldn't require the convoluted ductwork to get around the lift fan, and like I said, the engine only provides thrust, it's th airframe that's wrapped around it that dictates top speed available from that thrust and with the low RCS requirements fo the JSF program they can go larger with the intake ducts and make use of all that lovely extra thrust by just ducting it to the rear, we are talking about a plane with a 30,000lb empty weight, and any increase in the intake duct size could be smoothed into the rest of the airframe giving a larger "clean" capacity for fuel and stores

          You know you guys should really look into the pegasus variants and the work done on VTOL craft by Hawker Siddeley, namely the 1150/1154 and the 1205 (and the front fusilage and wings of the 1216), then you might just get what I'm driving at.

          Comment

          • eagle
            Rank 5 Registered User
            • Jan 2000
            • 2352

            #85
            The engine does dictate top speed. Or do you think a Harrier with a pointy nose will go supersonic.

            As it seems, the F-35 solution is best for supersonic fighters. Direct lift didn't work as well when an actual plane (the X-32) tested it.
            How can less be more? It's impossible. More is more.
            Yngwie Malmsteen

            Comment

            • MisterQ
              Rank 5 Registered User
              • Jan 2008
              • 475

              #86
              Originally posted by eagle View Post
              The engine does dictate top speed. Or do you think a Harrier with a pointy nose will go supersonic.

              As it seems, the F-35 solution is best for supersonic fighters. Direct lift didn't work as well when an actual plane (the X-32) tested it.

              The engine only dictates top speed in so far as thrust available and speed of the air as it exits the nozzles, and as for a harrier with a pointy nose going supersonic, probably not, but a harrier with a pointy nose, inlet ducts shaped so that the forward nozzles don't interfere with the flow of air over the fusilage, a single rear nozzle and an aft fusilage shaped to allow supersonic flight quite easily could, hell Sea harrier could do Mach 0.97 and it isn't exactly sleek and the SEPECAT Jaguar could do Mach 1.6 with a bypass ratio of pretty much 1:1 (adour bypass is about 0.8:1) and the Tornado is even faster (RB199 bypass is about 0.77).

              Oh, and as for the X-32, have you looked at that engine, from what I can tell it doesn't use bypass air for lift, it merely ducts it's dry thrust downward to a single pair of ducts aft of the engine itself by closing flaps on the main rearward nozzle, that and the roll posts was it, no enlarged low pressure compressor, so it doesn't really come into this conversation.
              Last edited by MisterQ; 26th April 2008, 22:50. Reason: bad spelling and to add a few figures

              Comment

              • bring_it_on
                2005-year of the RAPTOR!!
                • Jun 2004
                • 12480

                #87
                LOCKHEED MARTIN POWERS UP F-35 STOVL ENGINE IN PREPARATION FOR FIRST FLIGHT



                http://www.lockheedmartin.com/news/p...reardoors.html




                Courtesy - Pirate @ alert5
                Last edited by bring_it_on; 28th April 2008, 11:54.
                Old radar types never die; they just phased array

                Comment

                • MisterQ
                  Rank 5 Registered User
                  • Jan 2008
                  • 475

                  #88
                  Much as I despise the lift fan, that back end is seriously funky

                  Comment

                  • eagle
                    Rank 5 Registered User
                    • Jan 2000
                    • 2352

                    #89
                    Originally posted by MisterQ View Post
                    The engine only dictates top speed in so far as thrust available and speed of the air as it exits the nozzles, and as for a harrier with a pointy nose going supersonic, probably not, but a harrier with a pointy nose, inlet ducts shaped so that the forward nozzles don't interfere with the flow of air over the fusilage, a single rear nozzle and an aft fusilage shaped to allow supersonic flight quite easily could, hell Sea harrier could do Mach 0.97 and it isn't exactly sleek and the SEPECAT Jaguar could do Mach 1.6 with a bypass ratio of pretty much 1:1 (adour bypass is about 0.8:1) and the Tornado is even faster (RB199 bypass is about 0.77).
                    And how are you going to shape almost non-existing inlet ducts? How are you going to install a single rear nozzle? Thats an entirely new aircraft and the end result is about the X-32. Which failed.
                    Look at the F-35. What it does in STOVL mode is increasing the bypass ratio by engaging the fan. This allows for a fighter typical bypass ratio in normal flight. So while it has to carry around that ballast for the rest of the flight, it doesnt have the cross section of a barn and bypass ratio of a 747. In other words, its a fighter.

                    Originally posted by MisterQ View Post
                    Oh, and as for the X-32, have you looked at that engine, from what I can tell it doesn't use bypass air for lift, it merely ducts it's dry thrust downward to a single pair of ducts aft of the engine itself by closing flaps on the main rearward nozzle, that and the roll posts was it, no enlarged low pressure compressor, so it doesn't really come into this conversation.
                    Thats true, but the difference beetween that and the Harrier is it saves some nozzles but its the same principle.

                    The thing about direct lift VTOL jets is they need the engine mounted forward of the center of gravity. Very impractical as the engine is quite heavy.
                    How can less be more? It's impossible. More is more.
                    Yngwie Malmsteen

                    Comment

                    • bring_it_on
                      2005-year of the RAPTOR!!
                      • Jun 2004
                      • 12480

                      #90
                      Originally posted by MisterQ View Post
                      Much as I despise the lift fan, that back end is seriously funky
                      I believe that the Nozzle is an offshoot of the LOAN (Low observable Auxillary Nozzle) test nozzle (tested on the F-16) with the primary difference in the production nozzle being the higher useage of ceramics .
                      Old radar types never die; they just phased array

                      Comment

                      • MisterQ
                        Rank 5 Registered User
                        • Jan 2008
                        • 475

                        #91
                        Originally posted by eagle View Post
                        And how are you going to shape almost non-existing inlet ducts? How are you going to install a single rear nozzle? Thats an entirely new aircraft and the end result is about the X-32. Which failed.
                        Look at the F-35. What it does in STOVL mode is increasing the bypass ratio by engaging the fan. This allows for a fighter typical bypass ratio in normal flight. So while it has to carry around that ballast for the rest of the flight, it doesnt have the cross section of a barn and bypass ratio of a 747. In other words, its a fighter.


                        By shaping the inlet ducts I mean flowing the fusilage around the front nozzles, just as the F-35 continues the fusilage directly back instead of it following the contour of the inlet duct, the rear single nozzle would be the same Yak nozzle the F-35 has borrowed, and as for having the cross section of a barn, you have a 2 stage lift fan which has a 50 inch diameter being powered by the engine which has I believe a 47 inch diameter, why not just move to a 5 stage, 50 inch LP compressor (up from 3) making the extra bypass air available in level flight by either ducting it directly aft to it's own exhaust nozzles or feeding it back into the main.

                        Oh, and I'm talking about a roughly 1:1 bypass ratio which is not rare in Fighters (as I mentioned before), 747 engines have bybass ratios of up to 10:1 which is a bit beyond what I'm talking about

                        Comment

                        • pegon
                          Rank 5 Registered User
                          • May 2006
                          • 303

                          #92
                          To give an input on the cost of the F-35, they actually undercut the Swedes offering 48 fighters, at 20 billlion Nkr, for the Norwegian defence contract.

                          The gripen offer was 23 billion.

                          None of the offers contain lifetime support or weapons, as i understand it.

                          Comment

                          • swerve
                            Rank 5 Registered User
                            • Jun 2005
                            • 13610

                            #93
                            Originally posted by pegon View Post
                            To give an input on the cost of the F-35, they actually undercut the Swedes offering 48 fighters, at 20 billlion Nkr, for the Norwegian defence contract.

                            The gripen offer was 23 billion.

                            None of the offers contain lifetime support or weapons, as i understand it.
                            But the F-35 price is non-binding. LM will not commit itself to a price until, IIRC, 3 years before delivery, even with clauses allowing adjustment for inflation, currency changes, etc.

                            Saab will make a commitment.
                            Juris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere.
                            Justinian

                            Comment

                            • bring_it_on
                              2005-year of the RAPTOR!!
                              • Jun 2004
                              • 12480

                              #94
                              Originally posted by swerve View Post
                              But the F-35 price is non-binding. LM will not commit itself to a price until, IIRC, 3 years before delivery, even with clauses allowing adjustment for inflation, currency changes, etc.

                              Saab will make a commitment.
                              Do you have more information on this ? Perhaps a copy of the contract
                              Old radar types never die; they just phased array

                              Comment

                              • swerve
                                Rank 5 Registered User
                                • Jun 2005
                                • 13610

                                #95
                                Originally posted by bring_it_on View Post
                                Do you have more information on this ? Perhaps a copy of the contract
                                It's public information. Seek, & ye shall find. Plenty of public statements by the Norwegian authorities, for example, in response to questions from the better-informed press about the lack of a definite F-35 press. I think there may even be some further back in this thread, but I have to get back to work.

                                It's not specific to Norway, of course. It's a general rule. The price of the F-35 is not yet set for anybody, including the USA. Estimates only.

                                Note that it's not design & development cost, but production cost which will set the price.

                                [Edit]
                                '(Defense Minister Ann-Grete) Strom-Erichsen says Norway intends to ask tough questions before committing to any no-fixed-price JSF offer. “We don’t expect to find a price in there, and we expect that we’ll ask for more information.”'

                                Aviation week article

                                Also see public statements by Tom Burbage, e.g. in 2006 - and lots more.
                                Last edited by swerve; 30th April 2008, 13:01.
                                Juris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere.
                                Justinian

                                Comment

                                • pegon
                                  Rank 5 Registered User
                                  • May 2006
                                  • 303

                                  #96
                                  "Binding offer" in my world means "Binding offer"

                                  Comment

                                  • swerve
                                    Rank 5 Registered User
                                    • Jun 2005
                                    • 13610

                                    #97
                                    Originally posted by pegon View Post
                                    "Binding offer" in my world means "Binding offer"
                                    But not in Lockheed Martins world. As I understand it, the offer states that everything is binding except the price.
                                    Juris praecepta sunt haec: honeste vivere, alterum non laedere, suum cuique tribuere.
                                    Justinian

                                    Comment

                                    • Sintra
                                      Rank 5 Registered User
                                      • Aug 2007
                                      • 3838

                                      #98
                                      Originally posted by pegon View Post
                                      "Binding offer" in my world means "Binding offer"
                                      But its not, Lockheed Martin isnt prepared to sign a fixed price contract. They cant. That was one of the reasons why Eurofighter GMBH droped of the contest.
                                      When the Norwegian MOD transformed the contest from an RFP based to a RBI one, basically theyve given "carte blanche" to Lockheed Martin to advertise a unit cost based on a late 2005 "best case scenario", and those 20 billlion Nkr are exactly that, a highly optimistic prediction that LM wont put in a signed contract. And those 20 billlionNkr/48 Units are less than what the USAF states that its going to cost them their F-35A fleet, so we have a problem here...

                                      But dont take my word on it, from Bill Sweetman:
                                      Both countries have also adopted procurement strategies that gloss over a key difference between JSF and the European aircraft: Eurofighter and Gripen are both offering a fixed price, but there is no firm price on JSF, there won't be one until the first full-rate, multi-year production contract (set for 2013), and if Norway and Denmark stick to their current schedules they'll be buying some aircraft, at least, from the expensive low-rate initial production (LRIP) batches. Norway has covered up this issue by issuing a "request for binding information" (RBI) rather than a request for proposals, which would normally contain a binding price agreement.

                                      Without a fixed-price requirement, JSF marketeers are able to advertise their current estimated flyaway price (average price over the entire 3,000-plus projected run, without spares or support equipment), which looked like a bargain even before the dollar fell through the floor.
                                      http://www.aviationweek.com/aw/blogs...9-0fa4496c7e91

                                      What Tom Burbage has just said to the Norwegian Press is that LM his prepared to "sell" a 13 Ton, F-4E Phantom size, LO strike fighter, with a next generation AESA radar set, equiped with an internal "evolved" SNIPER XR LDP for the same price tag of a naked 8,5 ton "classical" Block 50+ Viper equiped with a mechanical AN/APG-68(V9) !!!
                                      But it didnt stop here, he was quoted saying that the logistical/cost footprint of the F-35A was "20% smaller than that of the F-16"!
                                      Hell, if thats true it goes "head to head" with the "old" Gripen C/D, the indisputable champion of the "im cheap to run" fighter award until now!
                                      Wait a minute, why my "Bulsh%# Metter" just went "through the roof"?

                                      If Lockheed Martin his prepared to sign a "fixed cost" contract with those numbers on it, double the original requirement and buy 96 of those "Lightning II".
                                      Its an historic event, the first time in history that a next generation fighter being bigger, heavier, more advanced, more capable his actually CHEAPER to buy and operate than their predecessor... It never happened before.
                                      This coming from LM, the guys responsable for the VH-71 helicopter, the Hercules Juliet, the LCS-1, the Raptor, etc, etc, etc, all projects with an "impecable" cost management.

                                      Right...
                                      sigpic

                                      Comment

                                      • bring_it_on
                                        2005-year of the RAPTOR!!
                                        • Jun 2004
                                        • 12480

                                        #99
                                        logistical/cost footprint of the F-35A was "20% smaller than that of the F-16"!
                                        That is an indication one gets if one reads into some of the requirments for the JSF (specially some of the RAND publication of COST:CAPABILITY trade off studies) , Atleast 20% reduction was supposed to be a reasonable requirment back then. Right now they are hush hush about it which isnt too different from what happened when F-22 program was @ this stage . Once the F-35A goes to the USAF for IODTE we will hear more about this .

                                        equiped with an internal "evolved" SNIPER XR LDP
                                        The EOTS+DAS is a lot different in capability then the SNIPER pod , i hear from internal sources that the imagery are greatly improved .

                                        If Lockheed Martin his prepared to sign a "fixed cost" contract with those number´s on it, double the original requirement and buy 96 of those "Lightning II".
                                        Good luck @ getting them to do that :-) , wont be done . The Gripen and the EF are production aircraft , fully ready and operational so the F-35 cannot compete until it goes operational iteself @ which time with huge lots and high per capita production runs i would expect it to be more economical .... BUT NOT YET.
                                        Old radar types never die; they just phased array

                                        Comment

                                        • eagle
                                          Rank 5 Registered User
                                          • Jan 2000
                                          • 2352

                                          Originally posted by MisterQ View Post
                                          By shaping the inlet ducts I mean flowing the fusilage around the front nozzles, just as the F-35 continues the fusilage directly back instead of it following the contour of the inlet duct, the rear single nozzle would be the same Yak nozzle the F-35 has borrowed,
                                          I see. But then the problem with the air intake remains. I dont think a supersonic jet is possible without intake. I'm no expert, but I think air needs to be slowed down to subsonic speed so the engine cannot face the air directly.

                                          Originally posted by MisterQ View Post
                                          and as for having the cross section of a barn, you have a 2 stage lift fan which has a 50 inch diameter being powered by the engine which has I believe a 47 inch diameter, why not just move to a 5 stage, 50 inch LP compressor (up from 3) making the extra bypass air available in level flight by either ducting it directly aft to it's own exhaust nozzles or feeding it back into the main.
                                          The lift fan adds those 47 inches to the engine which gives you a way bigger bypass ratio than possible with a single engine.

                                          Originally posted by MisterQ View Post
                                          Oh, and I'm talking about a roughly 1:1 bypass ratio which is not rare in Fighters (as I mentioned before), 747 engines have bybass ratios of up to 10:1 which is a bit beyond what I'm talking about
                                          The ones you mentioned aren't exactly the benchmark for fighters. And I dont know the bpr of the Harrier or the F-35 with engaged fan. But its probably more than 1:1.
                                          How can less be more? It's impossible. More is more.
                                          Yngwie Malmsteen

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