Hypersonic Deltas
Yes, but there are theoretical rules of thumb to take into account scaling differences right?
What's an adverse pressure ratio?
And what's shear drag?
CliveL that diagram summarizes so much
Do we need a wing at all?
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CliveL
I don't understand the diagram you gave me (the one on the left side). I can read and everything, I just don't understand the significance of all the parameters and what everything means.
I don't understand the diagram you gave me (the one on the left side). I can read and everything, I just don't understand the significance of all the parameters and what everything means.
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J-D
Sorry JD, but I am not going to be tempted to go down your road. I have watched on several threads how answering one of your "innocent" questions leads to another and another .... just like they were programmed or something
Try a good textbook.
CliveL
I don't understand the diagram you gave me (the one on the left side). I can read and everything, I just don't understand the significance of all the parameters and what everything means.
Try a good textbook.
CliveL
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CliveL
Is the R = rankine?
As for the second diagram regarding temperatures of an object at Mach 25... how the hell did such a blunt object get up to 6,000 K? That's 10,340 F -- blunt objects generally achieve lower skin temperatures than do sharp objects which is why they're used. IIRC, the space shuttle on reentry reached something like 1,650 to 1,750 C
Is the R = rankine?
As for the second diagram regarding temperatures of an object at Mach 25... how the hell did such a blunt object get up to 6,000 K? That's 10,340 F -- blunt objects generally achieve lower skin temperatures than do sharp objects which is why they're used. IIRC, the space shuttle on reentry reached something like 1,650 to 1,750 C
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Okay to somebody other than CliveL, does the R mean Rankine? As for the second diagram regarding temperatures of an object at Mach 25... how the hell did such a blunt object get up to 6,000 K? That's 10,340 F -- blunt objects generally achieve lower skin temperatures than do sharp objects which is why they're used. IIRC, the space shuttle on reentry reached something like 1,650 to 1,750 C
CliveL
I know you think I'm some kind of chatterbot, or just purposefully being annoying, but I'm not a chatterbot, and I'm not purposefully trying to annoy you. I honestly am just having trouble understanding the graph and rather than help you're instead just being difficult.
CliveL
I know you think I'm some kind of chatterbot, or just purposefully being annoying, but I'm not a chatterbot, and I'm not purposefully trying to annoy you. I honestly am just having trouble understanding the graph and rather than help you're instead just being difficult.
it's not about the absolute temperatures it's about how fast the heat can be dissipated transfered to cooling medium such as fuel; do a pprune search for 'ram rise formula'...
further discussion involves too much writing about 'flow in pipes'...
and compressibility
further discussion involves too much writing about 'flow in pipes'...
and compressibility
interesting...blunt bodies always form detached shockwaves at very high speed
I see what they are doing but I'd imagine getting an airplane out of it, as opposed to a missile, would be difficult
I wish they'd declassify the SR71's flight envelope...about as close to a functional hypersonic platform as we've come...Space shuttle excepted, too heavy and cumbersome for a plane ---and it explodes a lot...
my guess regarding the blackbird is M 4.0 @ FL 900...
I see what they are doing but I'd imagine getting an airplane out of it, as opposed to a missile, would be difficult
I wish they'd declassify the SR71's flight envelope...about as close to a functional hypersonic platform as we've come...Space shuttle excepted, too heavy and cumbersome for a plane ---and it explodes a lot...
my guess regarding the blackbird is M 4.0 @ FL 900...
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msbbarratt
The air-spike they're talking about involves projecting a small amount of directed energy which effectively acts like a sharp-nose.
I don't know if that applies at all speeds. From launch to supercavitation, it definitely would use the exhaust gas to lower drag; once it's supercavitating, it is effectively riding in a stream of air/steam.
Absolutely not. You can have a wing that is not swept much yet performs well at supersonic speeds. The wing has to be comparatively thin compared to a delta, has to have a sharper leading-edge; it should either be symmetrical, or inversely cambered, with the crest at at least 50% back. The shockwave will either be split by the wing (not sure about this, but if so it would be at zero sweep) or will sweep beyond the leading edge of the wing (greater than zero-sweep).
Trim drag is often substantial once the shockwave sweeps past the angle of the wing, the center of pressure will immediately go back to the 50% chord position, but that will happen once the shockwave sweeps beyond the leading-edge of a delta-wing too. Below the speed at which the shockwave sweeps beyond the leading-edge, a delta-wing is generally better from the standpoint of trim-drag; above it a straight or trapezoidal wing is actually better. The longer leading edge of the delta will have more shockwave traversing over it than an unswept wing (the leading edge is shorter from root to tip for the same span) as well as the fact that a delta wing is of a much longer chord typically than a straight-tapered, or trapezoidal wing.
The F-104 had a wing with barely any sweep and officially it could do Mach 2.2 (in truth, it could probably cruise near that speed), and in most likely could exceed Mach 3 in a short dash; it could definitely slip through the sound barrier even at low altitudes without afterburners being used (unsure if the plane was in a shallow dive when this happened or just at high power when level -- though this did happen with some remarkably loud results)
It's wings were effectively tapered, but otherwise considered straight. They were only 3.36% thick, had leading-edges as sharp as a knife, and other than a small degree of curvature on the leading and trailing edges, was virtually flat on top; the underside appeared to have a flared, inverse-camber (at least it appeared that way from an image a member posted on one of these forums). Trim drag appeared to be compensated for by the fact that the aircraft had a relatively large tail-surface; the basic drag of the airplane (not including trim-drag) was quite low; and the overall chord of the wing was not particularly massive relative to the length of the plane (meaning even though the CP shift was large relative to the chord, the actual shift was fairly small) and it's possible that the distribution of mass throughout the airplane resulted in very little pitch changes when transitioning through the sound-barrier.
The F-104 of course, was far from perfect; it's wings were way too small and it didn't maneuver very well unless you were flying like a bat out of hell -- oddly, it maneuvered very well when supersonic also (which seems to suggest that while L/D ratios tend to always be less when supersonic, the F-104's supersonic L/D ratio might not have been too much greater when subsonic compared to supersonic because it did so badly when subsonic and so well when supersonic).
The aircraft was originally designed as a dedicated light-fighter, but the USAF largely felt that if a fighter couldn't perform a nuclear strike mission, perform an interceptor role, or escort bombers (and their views on that oscillated periodically -- prior to WW2 they felt the bombers were fine on their own; then by around 1942 to 1943 they decided it would be a good idea to use planes like the P-38, P-47, and P-51 for that role, of which the P-51 was best suited; this stayed that way until the Korean War, until they switched to night-bombing, though sometimes a Navy F3D Skyknight was indeed providing escort; then they developed the XF-85 which could fly in the bomb-bay of a B-36 which had too long a range for any fighter, the XF-88 Penetration fighter which would fly escort in the traditional fashion, as well as some ideas of attaching F-84's onto the wings of a B-29 or B-50, but they changed their mind and cancelled all of them; then they decided that an escort wasn't such a bad idea after all and ordered the F-101 Voodoo, which they then cancelled. After that point they decided they'd just go supersonic, pursuing designs like the B-58 and XB-70 which due to their speed and range would not need escort -- unfortunately the B-58 was pretty expensive, and could only deliver nukes; the B-70 was psychotically expensive, costing 157 million dollars a pop had the USAF procured the 250 that they wanted resulting in it being relegated to a prototype), they didn't want to have anything to do with it. Unfortunately the USAF had this annoying characteristic of being rather uncompromising with designs (especially post Korea) and seemed to almost favor the secondary roles (i.e if you have a fighter/attack plane, they generally seemed to focus more on attack capability than they did the fighter capability) and the F-104 seemed to be designed more around the interceptor requirement than the fighter requirement (a delta wing would be far better suited for a fighter/interceptor as it would work well at subsonic/high-altitudes or supersonic) though at least it had a gun and a bubble canopy and may indeed be the first plane that could dogfight at Mach 2 (J/K)
The F-22, on the other hand, was designed both around agility and speed (as well as stealth): It has monstrously powerful engines which provide both good acceleration, the ability to go supersonic without using it's afterburners at all (afterburners are used to achieve the maximum dash speed, provide additional acceleration and thrust to sustain a high g-load across the performance envelope); it's wings are large, have automatically operated leading/trailing-edge flaps/flaperons to provide a good L/D ratio both when flying level and when aggressively maneuvering to provide a high degree of sustained agility; it has small strakes located just outboard of the engine inlets which produce a powerful vortex that when combined with thrust vectoring effectively eliminates any alpha limits; it's wings are more highly swept than the F-104 so it flies better at lower speeds (both subsonic and low-supersonic) and still does well supersonic; it is designed to be unstable which gives it remarkable instantaneous agility both subsonic and supersonic (which is again assisted by thrust vectoring as well); while it's missiles are carried internally for the purposes of stealth, it does reduce drag to some degree over carrying them externally.
Disclaimer: No information mentioned on the F-22 is classified
Pugilistic Animus
Yes, but they normally produce gigantic amounts of drag in the process. This effectively produces low drag by using directed energy to effectively produce a similar effect that a sharp flared cone would.
I don't get it either -- the Russians have seen what it can do after they've tried fruitlessly so many times to intercept it -- why not just admit the speed we knew the Russians saw it fly at?
You make it seem as if it blew up half the time! It only blew up twice.
There was this guy named Robert Widmer who worked for Convair (now works for Lockheed) and worked on the B-58 and (IIRC) the Convair Kingfish, which was the competitor to the A-12. According to what he said, the Kingfish could do Mach 6.5 and from what it would appear the A-12 and Kingfish had the same top speed. No idea about altitude but I'd guess 125,000 to 145,000 feet (Remember folks, no matter how I die, it was murder 
)
Consider the following
- The General Electric X279E was rated for Mach 4. The X279E later became known as either the XJ93-GE1 or YJ93-GE1. The engine was eventually enlarged into the J93-GE3. This was briefly mentioned in a book about the XB-70; this statement was effectively validated from a statement by Walt Spivak who was either the chief designer or chief engineer on the XB-70 and said the inlets could withstand conditions at Mach 4.0 made elsewhere.
- The J58 was capable of the same mach number as the J93 and was proposed briefly as a competitor, and was retained even after the J93 won the competition in case the J93 could not perform up to expectation (some people in the USAF also preferred it's simpler design).
- The J58 used on the A-12 was almost totally redesigned from the earlier versions. It was larger in diameter (IIRC: 52.5" vs 47"); it had a substantially greater amount of air-cooling; the metallurgy was almost entirely different; it had an elaborate bleed-bypass system routing up to 65% of the airflow around the engine into the afterburner; the combustion chamber and afterburner had features which allowed the fuel-to-air ratios to be lowered at high mach.
- Paul Csysz stated that the Blackbird was made out of a high temperature titanium alloy called Beta-Titanium. It has been stated that this alloy could take temperatures of 1,000 to 1,200 C; furthermore additional data has stated that the A-12 has active cooling in it's chines.
Jane D'oH!
I think it's interesting to compare a delta to a drag reducing aerospike like the Trident missile has:
Drag-resistant aerospike - Wikipedia, the free encyclopedia
Drag-resistant aerospike - Wikipedia, the free encyclopedia
VA-111 Shkval - Wikipedia, the free encyclopedia
This uses exhaust gas to push the water out of the way at the front in advance of the main body of torpedo.
This uses exhaust gas to push the water out of the way at the front in advance of the main body of torpedo.
I'm guessing, but I reckon that planes like the F22, with it's not very swept back wings, sacrifices high speed efficiency for agility, performance at lower speeds, etc.
Trim drag is often substantial once the shockwave sweeps past the angle of the wing, the center of pressure will immediately go back to the 50% chord position, but that will happen once the shockwave sweeps beyond the leading-edge of a delta-wing too. Below the speed at which the shockwave sweeps beyond the leading-edge, a delta-wing is generally better from the standpoint of trim-drag; above it a straight or trapezoidal wing is actually better. The longer leading edge of the delta will have more shockwave traversing over it than an unswept wing (the leading edge is shorter from root to tip for the same span) as well as the fact that a delta wing is of a much longer chord typically than a straight-tapered, or trapezoidal wing.
The F-104 had a wing with barely any sweep and officially it could do Mach 2.2 (in truth, it could probably cruise near that speed), and in most likely could exceed Mach 3 in a short dash; it could definitely slip through the sound barrier even at low altitudes without afterburners being used (unsure if the plane was in a shallow dive when this happened or just at high power when level -- though this did happen with some remarkably loud results
)It's wings were effectively tapered, but otherwise considered straight. They were only 3.36% thick, had leading-edges as sharp as a knife, and other than a small degree of curvature on the leading and trailing edges, was virtually flat on top; the underside appeared to have a flared, inverse-camber (at least it appeared that way from an image a member posted on one of these forums). Trim drag appeared to be compensated for by the fact that the aircraft had a relatively large tail-surface; the basic drag of the airplane (not including trim-drag) was quite low; and the overall chord of the wing was not particularly massive relative to the length of the plane (meaning even though the CP shift was large relative to the chord, the actual shift was fairly small) and it's possible that the distribution of mass throughout the airplane resulted in very little pitch changes when transitioning through the sound-barrier.
The F-104 of course, was far from perfect; it's wings were way too small and it didn't maneuver very well unless you were flying like a bat out of hell -- oddly, it maneuvered very well when supersonic also (which seems to suggest that while L/D ratios tend to always be less when supersonic, the F-104's supersonic L/D ratio might not have been too much greater when subsonic compared to supersonic because it did so badly when subsonic and so well when supersonic
).The aircraft was originally designed as a dedicated light-fighter, but the USAF largely felt that if a fighter couldn't perform a nuclear strike mission, perform an interceptor role, or escort bombers (and their views on that oscillated periodically -- prior to WW2 they felt the bombers were fine on their own; then by around 1942 to 1943 they decided it would be a good idea to use planes like the P-38, P-47, and P-51 for that role, of which the P-51 was best suited; this stayed that way until the Korean War, until they switched to night-bombing, though sometimes a Navy F3D Skyknight was indeed providing escort; then they developed the XF-85 which could fly in the bomb-bay of a B-36 which had too long a range for any fighter, the XF-88 Penetration fighter which would fly escort in the traditional fashion, as well as some ideas of attaching F-84's onto the wings of a B-29 or B-50, but they changed their mind and cancelled all of them; then they decided that an escort wasn't such a bad idea after all and ordered the F-101 Voodoo, which they then cancelled. After that point they decided they'd just go supersonic, pursuing designs like the B-58 and XB-70 which due to their speed and range would not need escort -- unfortunately the B-58 was pretty expensive, and could only deliver nukes; the B-70 was psychotically expensive, costing 157 million dollars a pop had the USAF procured the 250 that they wanted resulting in it being relegated to a prototype), they didn't want to have anything to do with it. Unfortunately the USAF had this annoying characteristic of being rather uncompromising with designs (especially post Korea) and seemed to almost favor the secondary roles (i.e if you have a fighter/attack plane, they generally seemed to focus more on attack capability than they did the fighter capability) and the F-104 seemed to be designed more around the interceptor requirement than the fighter requirement (a delta wing would be far better suited for a fighter/interceptor as it would work well at subsonic/high-altitudes or supersonic) though at least it had a gun and a bubble canopy and may indeed be the first plane that could dogfight at Mach 2
(J/K)The F-22, on the other hand, was designed both around agility and speed (as well as stealth): It has monstrously powerful engines which provide both good acceleration, the ability to go supersonic without using it's afterburners at all (afterburners are used to achieve the maximum dash speed, provide additional acceleration and thrust to sustain a high g-load across the performance envelope); it's wings are large, have automatically operated leading/trailing-edge flaps/flaperons to provide a good L/D ratio both when flying level and when aggressively maneuvering to provide a high degree of sustained agility; it has small strakes located just outboard of the engine inlets which produce a powerful vortex that when combined with thrust vectoring effectively eliminates any alpha limits; it's wings are more highly swept than the F-104 so it flies better at lower speeds (both subsonic and low-supersonic) and still does well supersonic; it is designed to be unstable which gives it remarkable instantaneous agility both subsonic and supersonic (which is again assisted by thrust vectoring as well); while it's missiles are carried internally for the purposes of stealth, it does reduce drag to some degree over carrying them externally.
Disclaimer: No information mentioned on the F-22 is classified
Pugilistic Animus
interesting...blunt bodies always form detached shockwaves at very high speed
I wish they'd declassify the SR71's flight envelope...
-- why not just admit the speed we knew the Russians saw it fly at?
Space shuttle excepted, too heavy and cumbersome for a plane ---and it explodes a lot...
my guess regarding the blackbird is M 4.0 @ FL 900...
)Consider the following
- The General Electric X279E was rated for Mach 4. The X279E later became known as either the XJ93-GE1 or YJ93-GE1. The engine was eventually enlarged into the J93-GE3. This was briefly mentioned in a book about the XB-70; this statement was effectively validated from a statement by Walt Spivak who was either the chief designer or chief engineer on the XB-70 and said the inlets could withstand conditions at Mach 4.0 made elsewhere.
- The J58 was capable of the same mach number as the J93 and was proposed briefly as a competitor, and was retained even after the J93 won the competition in case the J93 could not perform up to expectation (some people in the USAF also preferred it's simpler design).
- The J58 used on the A-12 was almost totally redesigned from the earlier versions. It was larger in diameter (IIRC: 52.5" vs 47"); it had a substantially greater amount of air-cooling; the metallurgy was almost entirely different; it had an elaborate bleed-bypass system routing up to 65% of the airflow around the engine into the afterburner; the combustion chamber and afterburner had features which allowed the fuel-to-air ratios to be lowered at high mach.
- Paul Csysz stated that the Blackbird was made out of a high temperature titanium alloy called Beta-Titanium. It has been stated that this alloy could take temperatures of 1,000 to 1,200 C; furthermore additional data has stated that the A-12 has active cooling in it's chines.
Jane D'oH!
Last edited by Jane-DoH; 23rd May 2011 at 21:46.
Yes, but they normally produce gigantic amounts of drag in the process. This effectively produces low drag by using directed energy to effectively produce a similar effect that a sharp flared cone would.
cool stuff, I think I see why you picked 'Jane'...
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Pugilistic Animus
I didn't create the name Jane DoH as an homage to "Jane's All The World's Aircraft". Jane DoH is basically a parody of Jane Doe, which is a fairly anonymous name pronounced like Homer Simpson saying "D'oH!"
I didn't create the name Jane DoH as an homage to "Jane's All The World's Aircraft". Jane DoH is basically a parody of Jane Doe, which is a fairly anonymous name pronounced like Homer Simpson saying "D'oH!"
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Pugilistic Animus
And I assume some energy is re-radiated back into the air? I do distinctly remember reading that if you flew at a given mach number at two different altitudes you'd get different skin temperatures which I was under the impression at the time had to do with the thinner air able to impart less heat to the plane, and the airplane's structure naturally able to radiate away a certain amount of heat.
it's not about the absolute temperatures it's about how fast the heat can be dissipated transfered to cooling medium such as fuel; do a PPRuNe search for 'ram rise formula'...
