That involves calculations and assumptions way above my pay grade
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That involves calculations and assumptions way above my pay gradeThe Tallboy and Grand Slam were, of course, designed to be dropped at greater altitudes than 18,000ft and may , had that been the case, have been able to break the sound barrier.
Yeah, it's bullshit.A P-47 in a controllable, recoverable 725mph dive is bollocks.
Actually there were at least two cases where the Spitfire lost a prop. One occurred during dive tests of the Mk.VII/VIII designs, the other was a PR variant that was modified with an all-moving tail for the Miles M.52 program.The fastest dive speed for a WW2 piston engine fighter that was confirmed (in actual, instrumented, dive tests) that I know of was 606mph (Mach 0.89) by a Spitfire XI. The tests also achieved a maximum Mach number of 0.92, albeit with exploding superchargers, loss of propeller (broke the reduction gear housing).
That was during the Korean War, but it was a WWII design. If I recall he ended up stalling at around 50000' and ended up accelerating to around 0.96 Mach at around 40000'. The aircraft might not have been under ideally controlled conditions, but it was undamaged during the dive, as crazy as that happened.A Spitfire XIX fell from over 50,000ft with a maximum speed estimated to be 690mph. It was far from a controlled dive.
If you want to use unmanned aircraft, then you should have gone with the V-2. It reached around Mach 5. That said, I was kind of thinking of manned aircraft. That said, the Me 262 and P-80 could be good candidates. I don't know how the Me 163 would rank because, while it was slippery in shape, it also was out of fuel at high altitudes.Zipper, the grand slam bomb, weighing 10 tons dropped from 18,000
As I understand it, the variables are how streamlined it is versus it's mass, and how much propulsive force is shoving it down along with the help of gravity.I'm still trying to fully understand the attributes that made one air frame 'superior' in a dive over another.
What's a zero-lift drag coefficient? I assume that would be what the plane would do in a ballistic arc? As for flat-plate equivalency, I'm guessing that's what it says on the box, the drag produced by the aircraft correlating to a given amount of area of a flat object in the wind...Although the P-38 was a relatively clean design for a twin-engine aircraft, the P-47 still maintained a lower zero-lift drag coefficient and smaller equivalent flat plate area, however total engine power goes to the P-38 which probably mitigated much of this.
From what I remember, the P-47's placard limit seemed to be around 0.745 Mach. If I recall that's like 3 miles an hour different from the P-51 (Mach 0.75). If I recall they did dive speeds of 0.78 with the P-47B/C, so that was do-able early on. It was stated that they did 0.82 Mach with the use of dive-recovery flaps. I'm not sure if it was possible to recover without them at that speed, but that's a pretty good dive speed (the P-51 was limited to around 0.84), though.But the P-47 remained far more controllable as it entered into compressability (not sure how dive brakes might have changed the equation though).
Actually the Seversky airfoil, which was used on the P-35, and was modified on the P-47, was a pretty good airfoil. As for dive performance, from what I remember, the P-51 and P-47 were pretty close to each other.From what I read the P-47 was equally as fast in a dive as the P-51, the Thunderbolt's greater weight and power probably making up for it's larger aerodynamic footprint and more traditional airfoil.
The tall boy and grand slam were dropped from air breathing aircraft, not sent in a sub orbital lob by a rocket. As I understand it they couldnt go supersonic if dropped in the atmosphere, but as I said it involves "stuff" above my pay grade. I just used it as a comparison, if a grand slam doesn't go supersonic how would a P-47? Its engine at the front could have been designed as an air brake and the wings are huge. Reaching speeds of mach 0.9 in a dive doesn't mean you are in any way close to reaching mach 1, it is the equivalent to being at the base camp of Mt Everest. The 262 and P-80 weren't "good candidates", they were just above base camp too.If you want to use unmanned aircraft, then you should have gone with the V-2. It reached around Mach 5. That said, I was kind of thinking of manned aircraft. That said, the Me 262 and P-80 could be good candidates. I don't know how the Me 163 would rank because, while it was slippery in shape, it also was out of fuel at high altitudes.
As for the Grand Slam and Tallboy, I thought they actually did reach supersonic speed when dropped from 18000-25000 feet?
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how it behaves as it enters comprehensibility (the P-38 comes to mind here).
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Although the P-38 was a relatively clean design for a twin-engine aircraft, the P-47 still maintained a lower zero-lift drag coefficient and smaller equivalent flat plate area, however total engine power goes to the P-38 which probably mitigated much of this. But the P-47 remained far more controllable as it entered into compressability (not sure how dive brakes might have changed the equation though). Because of these factors I can easily see how the P-47 can be close in acceleration to the P-38 but have a higher maximum sustainable dive speed.
This source seems to indicate the weapon could achieve a terminal velocity of 3600-3700 fps, though I don't know what altitude it was dropped from to achieve this speed.The tall boy and grand slam were dropped from air breathing aircraft, not sent in a sub orbital lob by a rocket.
Okay, I guess we sort of got off topic, focusing on supersonic flight rather than dive-acceleration rates. I was mostly interested in manned aircraft acceleration rates in dives.Reaching speeds of mach 0.9 in a dive doesn't mean you are in any way close to reaching mach 1, it is the equivalent to being at the base camp of Mt Everest. The 262 and P-80 weren't "good candidates", they were just above base camp too.
Both the booms and the gondola did it?The nacelles and pod on the P-38 created the venturi, that further accelerated the air stream.
I didn't know the windscreen caused a problem, but I knew about the gondola and the pod-afterbody. I'm surprised they didn't add the tail-cone extension.Another problem on P-38 was the pod, particularly the too steep windscreen and rear end of the pod, that was also modified by NACA to improve critical Mach number.
I also have comprehensibility-related issues...
Zipper, the grand slam bomb, weighing 10 tons dropped from 18,000 ft didn't break the sound barrier and it could hardly be more aerodynamic. A P-47 had 2000 BHP but no means to produce thrust, at speeds close to Mach1 the propeller comes off and the wings come off, even what is remaining wouldn't break the sound barrier. Pic from wiki
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People routinely discuss supersonic speeds, a passenger plane just crossed the Atlantic at "supersonic speed" it had a 200+ MPH tailwind. The V2 got to 100miles above the earth, easy to tell how fact it was going when it hit the ground, if we had no atmosphere, which is the point.I do remember in a documentary regarding the sinking of the Tirpitz, that the bomb was specifically said to achieve supersonic speeds on the way down.
Okay, I guess we sort of got off topic, focusing on supersonic flight rather than dive-acceleration rates. I was mostly interested in manned aircraft acceleration rates in dives.
My mentioning of the V-2 was that it reached Mach 5 in flight: The truth is, I don't know how fast it accelerated on the way up/down. That said, for acceleration rates, for manned aircraft, the Me-163, Me-262, or P-80 seem like good candidate as they have a streamlined fuselage, thin wings, and no propeller to produce air resistance at higher speeds.
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What's a zero-lift drag coefficient? I assume that would be what the plane would do in a ballistic arc? As for flat-plate equivalency, I'm guessing that's what it says on the box, the drag produced by the aircraft correlating to a given amount of area of a flat object in the wind...
That's why I posted the calculations are above my pay grade. The atmosphere becomes thicker and thicker, then you hit the ground.I read somewhere that the sound barrier would be broken by a Tallboy dropped at 40,000ft but it would barely break the barrier mach 1.001 or some such
A P-47 in a controllable, recoverable 725mph dive is bollocks.
The fastest dive speed for a WW2 piston engine fighter that was confirmed (in actual, instrumented, dive tests) that I know of was 606mph (Mach 0.89) by a Spitfire XI. The tests also achieved a maximum Mach number of 0.92,
FWIW, critical Mach speed of the P-47 was around 0.79 - 0.80.
Back to my pet peeve, static ports! No way an aircraft designed for pre supersonic flight is going to give you reasonably accurate airspeed indications once you bump up against the transonic range. Once shock waves form and Center of Pressure shifts, static port installations carefully developed for subsonic flight are likely subject to faulty sampling of static pressure. As SR6 mentioned above, the propeller arrives at an overrun condition near critical Mach, where it's an airbrake, creating cavitations and low pressure areas all around the fuselage. This is going to result in an absurdly high airspeed indication, especially considering that also the pitot tube is likely starting to push a pressure wave.There were newsreel reports of a P-40 doing 661mph in a dive
That is my understanding, I believe that in a theoretical situation with an unlimited atmosphere as we have at sea level and a force of 1G a tallboy would never break the sound barrier. Take one up to 100 miles high in the real world and it will on the way down then hit the earth before it has slowed down to its terminal velocity in air again. Unfortunately no Lancasters flew to 100 miles high and since the tallboy and grand slam were dumb bombs even dropping from 40,000 ft would mean you just didn't get any close enough.As for Tallboys/Grand Slams/V2s and Mach busting; it seems to me that it's all a function of how much acceleration is achieved in the thin atmosphere before the drag rise of the lower atmosphere sets in.
The USAF man that jumped from a balloon at 100,000+ feet in the early 60's exceeded the speed of sound.That is my understanding, I believe that in a theoretical situation with an unlimited atmosphere as we have at sea level and a force of 1G a tallboy would never break the sound barrier. Take one up to 100 miles high in the real world and it will on the way down then hit the earth before it has slowed down to its terminal velocity in air again. Unfortunately no Lancasters flew to 100 miles high and since the tallboy and grand slam were dumb bombs even dropping from 40,000 ft would mean you just didn't get any close enough.