Mach 2, 60,000 foot B-1R

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

The F-101 produces enough thrust for Mach 1.2 to 1.25 and the shock is
stable somewhere in the inlet ducting. The F-119 should produce enough
extra thrust to increase the max Mach significantly. 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.

"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

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

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.

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

"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

"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.

FWIW ISTR the Mne on the F102A was M 1.5 because of its simple
intakes. Again FWIW the only way you could fet anywhere near 1.5 was
in a dive . . .1.3 level was attainable, though.
Walt BJ

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. The F-119 should produce enough
extra thrust to increase the max Mach significantly. 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.

Know some pilots who swear they've gone 1.4, but only for very short
times. The biggest limiting factor are those two big RCS vanes in each
inlet.

Michael Kelly
Bone Maintainer

Why bother converting a B-1 into a supersonic reconnaissance plane,when
they could reactivate the SR-71's? What advantage would there be?

--
Jim Yanik
jyanik-at-kua.net