Lockheed L-133

[Zipper730]

I was told about this sometime ago, but I don't recall much mentioned on it.

Supposedly Lockheed wanted to build a plane that could dive through the sound-barrier in 1939 after problems popped up with the P-38, and from what I remember:

• It was designed around two gas-turbines, a weight of 18,000 pounds, 4 x 20mm cannon and 3 hrs endurance
  
• Lockheed supposedly ruled out using swept-wings in favor of straight ones: The first use of swept wings for high speed flight seemed to be suggested in 1935 (Volta conference)
  
• Originally it had a flush canopy with a glazed nose like a bomber, a cruciform tail like the Westland Whirlwind; later it morphed into a canarded design with a more conventional canopy with razorback

I remember the USAAF had little interest, and I'm not sure if it was because

• They wanted Lockheed to be focusing on building large numbers of conventional fighters
• They used the above as a pretext because they were already in the process of developing the P-59: A proof of concept intended to be our first jet-fighter
• A bit of both

They did express great interest in the engine, despite little in the aircraft, and continued to fund it until the late 1940's or early 1950's, though it was eventually reworked into a turboprop.

 

[FLYBOYJ]

 

[Graeme]

I remember the USAAF had little interest, and I'm not sure if it was because...

I've read it's because the L-1000 (X-37) engine eventually developed less than half the expected power and as a result the USAAF elected to go with the de Havilland Goblin instead.

Estimated maximum speeds based on the engines providing the designed thrust...

• 615 mph at SL.
• 620 mph at 20,000 ft.
• 605 mph at 40,000 ft.
• 710 mph terminal velocity as SL.

 

[Zipper730]

I've read it's because the L-1000 (X-37) engine eventually developed less than half the expected power and as a result the USAAF elected to go with the de Havilland Goblin instead.

I'm surprised with some of the absurdly complicated features built into it

You have to read this stuff to believe it (I might be wrong on a few details, but I did do some rudimentary research).

Layout 1

• Axial flow compressor, feeding a reciprocating compressor, driven by axial-turbine, and featuring an afterburner from the outset
• Engine weight was 1235 pounds, diameter was 24 inches
  
• Sea-level thrust was 6700-6750 pounds, 2200 pounds at 50,000 feet

I don't know if the thrust was based on mil-power or A/B, and I have no idea why you'd use a reciprocating compressor. The design was replaced with...

Layout 2

• Axial flow compressor (11-12 stage) feeding a (3-stage) centrifugal flow compressor, driven by a five-stage turbine.
  
• Inter-cooling was added between the axial and centrifugal compressor, and provision was made for additional cooling between the centrifugal stages
• The first compressor-stage was variable-pitched
  
• Differential-gearing and hydraulic coupling was to be incorporated as part of a desire to fine-tune the engine-RPM at altitude, as well as drive a boundary-layer-control suction device, while maintaining ideal engine RPM.
• Afterburner was retained with a fixed-geometry convergent/divergent nozzles
• Engine weight was now around 1700 pounds.

I'm not sure how serious Lockheed was in using laminar-flow control (it seemed to be more the interest of Nathan Price, who designed the engine. It's a feature that's useful in theory, but something more fit for a proof-of-concept design), though a pair of suck-in doors were located above/below the engines in an effort to remove turbulent air using jet-efflux.

Layout 3

• Twin-spool axial-flow compressor (16-stages per shaft), driven by a four-stage turbine (two per shaft)
• Intercooling was retained, but placed only between the two shafts
• Hydraulic coupling was confined only to the first four compressor stages
• An annular combustion chamber was now added.
• The turbines appeared to be designed with hollow passages to allow for either air or liquid cooling
• Afterburner now incorporated an eyelid nozzle and was regeneratively cooled
• Design was now approximately 1600 pounds

Estimated maximum speeds based on the engines providing the designed thrust...

• 615 mph at SL.
• 620 mph at 20,000 ft.
• 605 mph at 40,000 ft.
• 710 mph terminal velocity as SL.

• Thanks! I never had these figures before

 

[MIflyer]

And it was going to be made out of stainless steel.

 

[Zipper730]

And it was going to be made out of stainless steel.

Why?

 

[Zipper730]

Nobody?

 

[FLYBOYJ]

Why?

Because at the time it had the best known strength to weight ratio that would also withstand high temps

 

[pbehn]

Because at the time it had the best known strength to weight ratio that would also withstand high temps

It still does in comparison to other steels.

 

[Zipper730]

Because at the time it had the best known strength to weight ratio that would also withstand high temps

I understand the strength-to-weight thing. Why high temperatures? The plane's top speed was expected to be low supersonic...

 

[pbehn]

I understand the strength-to-weight thing. Why high temperatures? The plane's top speed was expected to be low supersonic...

You are discussing engines, they get hot.

 

[Zipper730]

pbehn,

I'm sorry, I basically got confused as the thread was initially about the aircraft, and then the engine and aircraft. Both actually had steel in their construction, so I didn't just go blonde all the sudden (though I do have premature gray)

 

[pbehn]

pbehn,

I'm sorry, I basically got confused as the thread was initially about the aircraft, and then the engine and aircraft. Both actually had steel in their construction, so I didn't just go blonde all the sudden (though I do have premature gray)

In some ways it is an historical trick. Steel is officially an alloy of Iron and Carbon. Stainless steel can almost be what you want it to be as long as it has some Iron and some Carbon. Some stainless steels have over 50% chromium nickel and others, while turbine blades from the start had circa 20% cobalt.

 

[Zipper730]

Steel is officially an alloy of Iron and Carbon. Stainless steel can almost be what you want it to be as long as it has some Iron and some Carbon. Some stainless steels have over 50% chromium nickel and others, while turbine blades from the start had circa 20% cobalt.

That's actually good to know (and it's kind of sad I don't know that...)

 

[Zipper730]

I'm wondering why the engines were so overly complicated even from the outset? While all early jet-engines were sort of uncharted waters: None of the other designs I know of included the following

• Reciprocating compressors
• Mixed-flow compressors (unless you count the diagonal stage on some of the Heinkel designs)
• Twin-spool compressors
• Differential gearing & hydraulic coupling
• Intercoolers

I know they wanted the efficiency of the engine to be as close to a piston-engine as possible, I know that high pressure-ratios are conducive to high engine efficiency, but how close did they think the could get to a piston-engine?