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#11
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wrote Since the standardized designation system is gone out the window now anyway, I won't be surprised if the R is for recon, instead of calling it an RB-1D(?). You might actually_read_the article in AvWeek.. The USAF is clearly in the market for better bombers, not recce platforms. |
#12
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Scott Ferrin wrote in message . ..
On Wed, 2 Jun 2004 21:23:08 GMT, "breyfogle" wrote: The F-101 produces enough thrust for Mach 1.2 to 1.25 and the shock is stable somewhere in the inlet ducting. It sounds like you're missing the point. The F101 has enough power to take the B-1 to Mach 2.2 and had done so prior to the inlet redesign. Since the inlet redesign it can't go there anymore. Period. More thrust isn't going to get you a higher top speed. More thrust (particularly dry thrust) will get you more speed for a given weight but if the inlets weren't an issue they'd have been fixed from the start or else a clean B-1B would still be able to hit Mach 2+. It can't. *ponders* I wonder if there's any new "lessons learned" data from F-22/35 development that might permit another inlet redesign on the Bone. The AF might be able to both get the speed and stay stealthy with a new, more sophisticated inlet design based on the technology and experience they've gained in the past ten years or so. |
#13
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Paul F Austin wrote: wrote Since the standardized designation system is gone out the window now anyway, I won't be surprised if the R is for recon, instead of calling it an RB-1D(?). You might actually_read_the article in AvWeek.. The USAF is clearly in the market for better bombers, not recce platforms. But think of the fun when the fifth version ( fourth modification ) is introduced. Bob McKellar |
#14
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One of the factors limiting installed thrust is the ability of the duct to
flow a maximum amount of air mass. I don't see any particular reason why a different engine (optimized for a different Mach/Altitude) might not be able to produce more thrust when installed in the same nacelle, flowing the same mass of air. I'm not an engine person but seems like increasing the compression ratio, changing the bypass ratio, increasing the turbine temp and increasing the fuel flow might all increase the thrust level for a given mass flow rate. Certainly, not every turbofan engine produces the same thrust when flowing the same mass of air. Scott Ferrin wrote in message ... On Wed, 2 Jun 2004 21:23:08 GMT, "breyfogle" wrote: The F-101 produces enough thrust for Mach 1.2 to 1.25 and the shock is stable somewhere in the inlet ducting. It sounds like you're missing the point. The F101 has enough power to take the B-1 to Mach 2.2 and had done so prior to the inlet redesign. Since the inlet redesign it can't go there anymore. Period. More thrust isn't going to get you a higher top speed. More thrust (particularly dry thrust) will get you more speed for a given weight but if the inlets weren't an issue they'd have been fixed from the start or else a clean B-1B would still be able to hit Mach 2+. It can't. The F-119 should produce enough extra thrust to increase the max Mach significantly. If you are comparing dry thrust to dry thrust then sure. Sure, the shock front moves aft as Mach increases and at some point the shock will reach the fan and bad things happen. F-16's & F-18's reach 1.6 (1.8?) Mach with fixed inlets. The B-1's speed is limited by the inlets, not the engines. True, the F119 is optimized for higher speed than the F101 but the inlets will still make a difference. "Peter Kemp" wrote in message news On Wed, 2 Jun 2004 13:42:25 GMT, "breyfogle" wrote: The F119 engines make sufficient thrust to allow high altitude supersonic cruise at a Mach somewhat less than Mach 2 while not requiring any significant change to the current fixed inlets. The tradeoff is a significant reduction in range. I thought the requirement for adjustable inlets was to avoid the supersonic shockwave impinging on the compressor and stalling the engine. If so, then the thrust of the F-119 isn't oging to help at all. Peter Kemp |
#15
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"breyfogle" wrote in message ... One of the factors limiting installed thrust is the ability of the duct to flow a maximum amount of air mass. I don't see any particular reason why a different engine (optimized for a different Mach/Altitude) might not be able to produce more thrust when installed in the same nacelle, flowing the same mass of air. I'm not an engine person but seems like increasing the compression ratio, changing the bypass ratio, increasing the turbine temp and increasing the fuel flow might all increase the thrust level for a given mass flow rate. Certainly, not every turbofan engine produces the same thrust when flowing the same mass of air. The problem is that the flow regime for subsonic flight is entirely different than for supersonic flight. The bottom line is that turbofan engines cant cope with supersonic flow so above Mach 1 you need to slow the flow. Trouble is this makes it inefficient at subsonic speeds. To get round this some aircraft use variable inlet geometries but this conflicts with stealth requirements. The B-1A had the variable geometry required for supersonic flight, the B-1B does not. You'd need to redesign the entire inlet system to provide high supersonic performance. Keith |
#16
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If I subscribed to AvWeek, I _would_ read the article.
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#17
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wrote in message ... If I subscribed to AvWeek, I _would_ read the article. Most University libraries and large city libraries carry it. It's worth while. |
#18
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"Keith Willshaw" wrote in message ... "breyfogle" wrote in message ... One of the factors limiting installed thrust is the ability of the duct to flow a maximum amount of air mass. I don't see any particular reason why a different engine (optimized for a different Mach/Altitude) might not be able to produce more thrust when installed in the same nacelle, flowing the same mass of air. I'm not an engine person but seems like increasing the compression ratio, changing the bypass ratio, increasing the turbine temp and increasing the fuel flow might all increase the thrust level for a given mass flow rate. Certainly, not every turbofan engine produces the same thrust when flowing the same mass of air. The problem is that the flow regime for subsonic flight is entirely different than for supersonic flight. The bottom line is that turbofan engines cant cope with supersonic flow so above Mach 1 you need to slow the flow. Trouble is this makes it inefficient at subsonic speeds. To get round this some aircraft use variable inlet geometries but this conflicts with stealth requirements. The B-1A had the variable geometry required for supersonic flight, the B-1B does not. You'd need to redesign the entire inlet system to provide high supersonic performance. That's certainly possible and even for a fixed inlet. If the inlet is optimized for M2, then off design point operation may suffer somewhat but Boeing is suggesting a supercruiser bomber in any case. |
#19
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"Bob McKellar" wrote in message ... But think of the fun when the fifth version ( fourth modification ) is introduced. Bob McKellar B-1RD? ;o) Steve R. |
#20
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On Wed, 2 Jun 2004 23:50:43 +0000 (UTC), Jim Yanik wrote:
Why bother converting a B-1 into a supersonic reconnaissance plane,when they could reactivate the SR-71's? What advantage would there be? SRs are *very* expensive to operate and maintain. The savings achieved by using the B-1 would soon pay for themselves. Al Minyard |
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