Kinetic Heating vs Mach Number

[KJ_Lesnick]

I've touched upon this topic once before.

From what I've read in aerodynamics text-books, that just seem to say things that just ain't so about kinetic heating. Especially regarding claims that the temperature jumps up to 800-degrees farenheit at Mach 3.2.

First of all, kinetic heating isn't exactly the same for every aircraft. Streamlined designs tend to not heat up as extremely as designs that are not as streamlined -- the B-58 at the nose reaches around 220 F at Mach 2, while the Concorde reaches 260 F for the exact same mach number. For all I know reynolds numbers might play a role as well, which are a function of scale. The lower the reynolds-numbers the flow tends to be smoother and less turbulent, the higher the reynolds-numbers the flow tends to be more turbulent. Turbulent-flow seems to aggravate kinetic-heating, as during the AST/HSCT-programs the use of boundary-layer control was evaluated not just in drag-reduction but in lowering skin-temperature as well. With turbulent flow aggravating kinetic heating, and larger vehicles having greater turbulence as a result of higher-reynolds numbers, it would be logical to conclude that smaller aircraft tend not to get as hot for the same mach-number either, although I'm not sure HOW much this plays a role.

Second of all, at Mach 3.2, it would be very unusual for skin temperature even at the nose to reach 800 or 900 farenheit. At mach 3, temperatures tend to be around 500-600 degrees depending on the design, at Mach 3.2 the temperatures would be higher than at Mach 3.0, however unlike the claims I've heard, they do not seem to jump radically by 200-400 degrees (Mach 3 = 500 - 600). However temperatures do seem to indisputably spike once in the hypersonic range.

Regarding inlet-temps, I'm not entirely sure if inlet temp is exactly the same on all aircraft. Higher efficiency would yield more pressure, but less turbulent air. And many inlets use porous ramps which skim off most of the turbulent air which improve efficiency. Since turbulent flow is a source of heating, it seems like there would be some varying here as well.

Am I missing anything?


BTW: I wonder with some of these aerodynamics-textbooks that I've read why the screw-ups? The numbers I'm coming up with are from actual aircraft, so either they over simplified it, or screwed-up royally -- I mean, if I started making screw-ups like that you'd be able to know something was seriously wrong!


Kendra

 

[Lee]

www.americanantigravity.com/documents/Paul-Czysz-Hypersonic-Interview.pdf

www.journals.royalsoc.ac.uk/index/27RTT12AJDP834HE.pdf

The foregoing sites hosting these papers deal with more than just frictional heating of aircraft, but the references should be understandable by the average person, I think.

The specific information you're looking for was found in the past by me in the middle of research papers like the second one listed.
Speed, altitude, thermal protection, and materials of aircraft construction are wide variables, so a simple, pat answer may be difficult to come by.

(The sites were up and running on the day they were first posted.)

 

[KJ_Lesnick]

This is incredible!

Am I reading this correctly that the X-7 was not a ramjet but a scramjet? And that they tested models with scramjets up to Mach 12 and tunnel models to Mach 22? Were the Mach 12 models (at least) drones, manned-vehicles, or just wind-tunnel models? (the wording seems kind of confusing)

The US had a vehicle that could takeoff and land like an airplane sometime before 1964? (They said as of 1964, they had 11 of them and 3 spares, and they flew 100 times a year for 15 years). When did it first fly? It was a SSTO or a TSTO? (mentioned on Page 9) or what was it? I don't know if I missed something.

What happened to the Mach 6 Naval Interdictor... and the Mach 4 deck-launched interceptor? Were either ever built, tested or ever used? What became of the Mach 8 strategic bomber that was mentioned on the upper half of page 8?


You know, it seems as if McDonnell actually did more than Skunk-Works did in the high-speed research area! And I think they managed to keep more secret about it than Lockheed did about it's A-12, which the Russians already knew about in 1960.


BTW: Did Czysz say that the YF-12 fired six missiles total or that it carried six missiles onboard? (because I always thought it carried 4)


Kendra Lesnick

 

[flateric]

.

What happened to the Mach 6 Naval Interdictor... and the Mach 4 deck-launched interceptor? Were either ever built, tested or ever used? What became of the Mach 8 strategic bomber that was mentioned on the upper half of page 8?

As said in one 2000 Marquardt history paper...hmmm...these were 'classified top secret then [60s] tactical aircraft program, no references available' which should use Marquardt SERJ engine. There was at least AF swing-wing hypersoniс interceptor and Navy desk-launched interceptor projects.

.
BTW: Did Czysz say that the YF-12 fired six missiles total or that it carried six missiles onboard? (because I always thought it carried 4)


Kendra Lesnick

It could carry three, right rear bay was occupied with electronics/test equipment. There were 7 launches of AIM-47 *on the drone target*, one was miss due to gyro failure. Total said of 12 launches of Falcon from YF-12.

 

[starviking]

www.americanantigravity.com/documents/Paul-Czysz-Hypersonic-Interview.pdf

On the X-7 scramjet quote in this document: I'd say - news to me.

On the caption that the NASP would have replaced the shuttle - I doubt it. The NASP designs all had much smaller payloads than the Shuttle.

Starviking

 

[KJ_Lesnick]

As said in one 2000 Marquardt history paper...hmmm...these were 'classified top secret then [60s] tactical aircraft program, no references available' which should use Marquardt SERJ engine. There was at least AF swing-wing hypersoniс interceptor and Navy desk-launched interceptor projects.

So there's no data whether it flew or not? Or it was just a study?

It could carry three, right rear bay was occupied with electronics/test equipment. There were 7 launches of AIM-47 *on the drone target*, one was miss due to gyro failure. Total said of 12 launches of Falcon from YF-12.

If I recall, the forward right bay had equipment in it, the forward left, rear left, and rear-right bay carried missiles, and a bay was carved in aft of the nose-gear. That's 4-missiles...

The production model would have not needed instrumentation in the forward right bay and the folding fin AIM-47B's would have been able to fit in smaller bays. Allegedly that would be four. But technically one could fit two AIM-47B's in two closely spaced center-bays as the thinner overall size could allow them to be squeezed together. I have no evidence this was done, but that could have fitted six.

Regarding launches from the YF-12, the first five launches were just to make sure the weapon would launch properly? Then the final 7 were at targets, of which five or six hit right?

On the X-7 scramjet quote in this document: I'd say - news to me.

I know, it has me puzzled too. It doesn't look like a scramjet either. I could be wrong.

On the caption that the NASP would have replaced the shuttle - I doubt it. The NASP designs all had much smaller payloads than the Shuttle.

Which NASP are you talking about. The 1964 one, or the 1986 one?

I'm not sure by the wording, was it a single stage to orbit, twin-staged? Was the last stage a rocket-powered vehicle?


K.J.

 

[Lee]

KJ_Lesnick, quoted:
"Am I reading this correctly that the X-7 was not a ramjet but a scramjet?"

Today's 'scramjets' in public media and patents aren't the same kind of engines available on the X-7. But the X-7 was so fast, hardly any antiaircraft missile could hit it. That may have been why it was cancelled. 'Saving political face', one might say.
I don't know if an early 60's Marquardt engine could go Mach 6-12 with that type of technology. Very large intakes at very high altitudes will increase thrust, but even an air-breathing SSTO (NASP?) would need intakes so big that weight and drag would be insurmountable problems.
(The X-7 set a long-standing speed record for ramjets until it was broken recently by a prototype hypersonic interceptor missile with a throttle stuck wide open.)




KJ: "And that they tested models with scramjets up to Mach 12 and tunnel models to Mach 22? Were the Mach 12 models (at least) drones, manned-vehicles, or just wind-tunnel models? (the wording seems kind of confusing)"

Ultra high speeds might seem to be easier to achieve in a lab, but scaling up a design and then trying to get it to perform the same way in the air has been problematic for a few programs in the past. The original SST programs come to mind as an example.





KJ: "The US had a vehicle that could takeoff and land like an airplane sometime before 1964? (They said as of 1964, they had 11 of them and 3 spares, and they flew 100 times a year for 15 years). When did it first fly?"

They would have had to build all the prototypes before 1964, so I'd logically say it flew in late '63 or early '64.





KJ: "It was a SSTO or a TSTO? (mentioned on Page 9) or what was it? I don't know if I missed something.

I read the page and Czysz didn't say. Skylab may have been what the application for a launch vehicle called for. Most studies I've seen indicated horizontally launched cargo vehicles---air-breathing or rocket---would have been limited by runway strength issues and very high wing loadings when size was unduly increased. The Sanger-style TSTO design might have been some improvement in efficiency, but size would remain an issue.
Launching vertically eliminated all but the inverse size scaling issue.

KJ: "What happened to the Mach 6 Naval Interdictor... and the Mach 4 deck-launched interceptor?

I have a couple of theoretical academic papers at home on the subject I printed off the Internet, but the sites may or may not be up and running now. I could go look later.
If they actually built the prototypes, they're still classified, or the sensationalistic media would have 'trumpeted' their existence by now.





KJ: "Were either ever built, tested or ever used? What became of the Mach 8 strategic bomber that was mentioned on the upper half of page 8?"

Czysz said the plans/blueprints were destroyed, didn't he? However, I seriously doubt that all the information was destroyed for the same reason the IRS keeps financial records in databases forever---possible future investigations. NASA is well known for keeping obscure research material filed away until someone might need it later, just in case.





KJ: "You know, it seems as if McDonnell actually did more than Skunk-Works did in the high-speed research area! And I think they managed to keep more secret about it than Lockheed did about it's A-12, which the Russians already knew about in 1960.

Oh, yeah! A know someone who had a VERY high clearance in the military (now retired) who said that things were way more advanced than even I would understand.





KJ:" BTW: Did Czysz say that the YF-12 fired six missiles total or that it carried six missiles onboard? (because I always thought it carried 4)"

Did the Blackbird have a missile bay or rocket launch rails? It did have an avionics bay aft of the pilot.


Kendra Lesnick
[/quote]

 

[KJ_Lesnick]

Today's 'scramjets' in public media and patents aren't the same kind of engines available on the X-7. But the X-7 was so fast, hardly any antiaircraft missile could hit it. That may have been why it was cancelled. 'Saving political face', one might say.

Saving political face? You mean to prevent the Russians from realizing how behind they were and building increasingly faster and more capable missiles to nail it?

I don't know if an early 60's Marquardt engine could go Mach 6-12 with that type of technology. Very large intakes at very high altitudes will increase thrust, but even an air-breathing SSTO (NASP?) would need intakes so big that weight and drag would be insurmountable problems.
(The X-7 set a long-standing speed record for ramjets until it was broken recently by a prototype hypersonic interceptor missile with a throttle stuck wide open.)

Keep in mind, the hypersonic designs developed by McDonnell were not blunt nosed airplanes with hot-structures as heat-sinks. This eliminated the need for high temp-fuels or cryogenic fuels like LH2 -- They were designed with light-weight heat-shields instead.

Ultra high speeds might seem to be easier to achieve in a lab, but scaling up a design and then trying to get it to perform the same way in the air has been problematic for a few programs in the past. The original SST programs come to mind as an example.

Well, the SST's were heavier than initially expected and low speed handling got it a bit. But the SST designs could have flown. It's just that politics and environmentalists got in the way.

They would have had to build all the prototypes before 1964, so I'd logically say it flew in late '63 or early '64.

Fascinating. Development I guess began in 1958?

Most studies I've seen indicated horizontally launched cargo vehicles---air-breathing or rocket---would have been limited by runway strength issues and very high wing loadings when size was unduly increased. The Sanger-style TSTO design might have been some improvement in efficiency, but size would remain an issue.
Launching vertically eliminated all but the inverse size scaling issue.

I'm confused... it's an SSTO, or a turboramjet launch plane, and a scramjet/rocket to get it to orbit?

I have a couple of theoretical academic papers at home on the subject I printed off the Internet, but the sites may or may not be up and running now. I could go look later.

Thanks...

If they actually built the prototypes, they're still classified, or the sensationalistic media would have 'trumpeted' their existence by now.

True... Especially the interdictor. The deck-launched Mach 4 interceptor doesn't seem to have been built as someone would have seen it (But I could be wrong! The Navy kept unbelievably tight-lipped about it's use of nukes until they stopped using them in 1997, where as the USAF while not exactly open about them, admitted their existance -- I mean, even in a *Star-Trek* episode for godssakes the USS-Enterprise's crew went back in time 300-years and were flying along the upper atmosphere and was within intercept range of a fighter, which as depicted was an F-104. The crew was worried that it might have nuclear-tipped missiles which could severely damage the ship. While Star-Trek is fiction, the fact that the carrying of nuclear-tipped air to air missiles by then current USAF aircraft on a TV-show shows that it wasn't that secret.)

Czysz said the plans/blueprints were destroyed, didn't he? However, I seriously doubt that all the information was destroyed for the same reason the IRS keeps financial records in databases forever---possible future investigations. NASA is well known for keeping obscure research material filed away until someone might need it later, just in case.

Still kind of hard to believe that we could have built a spaceplane in the 1960's, and yet we couldn't get a design off the ground in the 1980's and 1990's with drastically superior aerospace technology, better understanding of aerodynamics and CFD.

Oh, yeah! A know someone who had a VERY high clearance in the military (now retired) who said that things were way more advanced than even I would understand.

Magnetohydrodynamic stuff, and air-spike technology especially.

Did the Blackbird have a missile bay or rocket launch rails? It did have an avionics bay aft of the pilot.

Individual refrigerated missile bays. Missiles were ejected by explosive charge.

Regarding the bay set up-- I've seen the plane carrying a missile in the center-bay behind the cockpit, on either side, and one on the front left-side. There may have been a small amount of avionics stuff just underneath the WSO though or just above the missile bay.


Kendra

 

[starviking]

On the X-7 scramjet quote in this document: I'd say - news to me.

I know, it has me puzzled too. It doesn't look like a scramjet either. I could be wrong.

I'm wondering if some supersonic flow through the combustor occurred during the test programme - that could mutate into "X-7 had a scramjet".

On the caption that the NASP would have replaced the shuttle - I doubt it. The NASP designs all had much smaller payloads than the Shuttle.

Which NASP are you talking about. The 1964 one, or the 1986 one?

I'm not sure by the wording, was it a single stage to orbit, twin-staged? Was the last stage a rocket-powered vehicle?

Well, the PDF is talking about the 1986 one. The 60's design was just the study baseline according to the PDF. As for NASP - I always thought it was SSTO. The PDF text mentions a version with an upper stage rocket to go into LEO. It doesn't jibe with what I know about the programme, which isn't much - but there does seem to be a lot of hyperbole in the PDF which makes me leery of taking it at face value.

Starviking

 

[KJ_Lesnick]

So, the original design was single-stage and had a smaller payload than the Shuttle. I take it it used some kind of RBCC system... rocket low speed, ramjets and scramjets for high-speeds, with rockets to orbit.

I assume it was a lot bigger than the shuttle...

 

[Lee]

KJ, quoted: "Saving political face?

I meant the source I saw implied American politicians wanted to save face by not having to admit the Russians might be able to get something by the Air force and not have the military stop it with anything.

That's the face-saving I mean.





KJ: "You mean to prevent the Russians from realizing how behind they were and building increasingly faster and more capable missiles to nail it?"

Honestly, I read a couple of 1st person accounts of political prisoners in Russia or Siberia that lead me to believe that the Russian Communists (not the ordinary peasants---they were just trying to get by like everyone else), they were so paranoid toward the West that they would try and build a faster missile, regardless of cost to them.

Cold War Communists were really distrustful, in my opinion.

I don't know if an early 60's Marquardt engine could go Mach 6-12 with that type of technology. Very large intakes at very high altitudes will increase thrust, but even an air-breathing SSTO (NASP?) would need intakes so big that weight and drag would be insurmountable problems.
(The X-7 set a long-standing speed record for ramjets until it was broken recently by a prototype hypersonic interceptor missile with a throttle stuck wide open.)

Keep in mind, the hypersonic designs developed by McDonnell were not blunt nosed airplanes with hot-structures as heat-sinks. This eliminated the need for high temp-fuels or cryogenic fuels like LH2 -- They were designed with light-weight heat-shields instead.

Ultra high speeds might seem to be easier to achieve in a lab, but scaling up a design and then trying to get it to perform the same way in the air has been problematic for a few programs in the past. The original SST programs come to mind as an example.

Well, the SST's were heavier than initially expected and low speed handling got it a bit. But the SST designs could have flown. It's just that politics and environmentalists got in the way.

They would have had to build all the prototypes before 1964, so I'd logically say it flew in late '63 or early '64.

Fascinating. Development I guess began in 1958?

Most studies I've seen indicated horizontally launched cargo vehicles---air-breathing or rocket---would have been limited by runway strength issues and very high wing loadings when size was unduly increased. The Sanger-style TSTO design might have been some improvement in efficiency, but size would remain an issue.
Launching vertically eliminated all but the inverse size scaling issue.

I'm confused... it's an SSTO, or a turboramjet launch plane, and a scramjet/rocket to get it to orbit?

I have a couple of theoretical academic papers at home on the subject I printed off the Internet, but the sites may or may not be up and running now. I could go look later.

Thanks...

If they actually built the prototypes, they're still classified, or the sensationalistic media would have 'trumpeted' their existence by now.

True... Especially the interdictor. The deck-launched Mach 4 interceptor doesn't seem to have been built as someone would have seen it (But I could be wrong! The Navy kept unbelievably tight-lipped about it's use of nukes until they stopped using them in 1997, where as the USAF while not exactly open about them, admitted their existance -- I mean, even in a *Star-Trek* episode for godssakes the USS-Enterprise's crew went back in time 300-years and were flying along the upper atmosphere and was within intercept range of a fighter, which as depicted was an F-104. The crew was worried that it might have nuclear-tipped missiles which could severely damage the ship. While Star-Trek is fiction, the fact that the carrying of nuclear-tipped air to air missiles by then current USAF aircraft on a TV-show shows that it wasn't that secret.)

Czysz said the plans/blueprints were destroyed, didn't he? However, I seriously doubt that all the information was destroyed for the same reason the IRS keeps financial records in databases forever---possible future investigations. NASA is well known for keeping obscure research material filed away until someone might need it later, just in case.

Still kind of hard to believe that we could have built a spaceplane in the 1960's, and yet we couldn't get a design off the ground in the 1980's and 1990's with drastically superior aerospace technology, better understanding of aerodynamics and CFD.

Oh, yeah! A know someone who had a VERY high clearance in the military (now retired) who said that things were way more advanced than even I would understand.

Magnetohydrodynamic stuff, and air-spike technology especially.

Did the Blackbird have a missile bay or rocket launch rails? It did have an avionics bay aft of the pilot.

Individual refrigerated missile bays. Missiles were ejected by explosive charge.

Regarding the bay set up-- I've seen the plane carrying a missile in the center-bay behind the cockpit, on either side, and one on the front left-side. There may have been a small amount of avionics stuff just underneath the WSO though or just above the missile bay.


Kendra
[/quote]

 

[Orionblamblam]

What happened to the Mach 6 Naval Interdictor... and the Mach 4 deck-launched interceptor?

Nothing. Accorditing to Bill Escher, those designs were just artwork, cooked up to help sell the SERJ engine.

Calm down, people. This ain't ATS.

 

[Sferrin]

What happened to the Mach 6 Naval Interdictor... and the Mach 4 deck-launched interceptor?

Nothing. Accorditing to Bill Escher, those designs were just artwork, cooked up to help sell the SERJ engine.

Calm down, people. This ain't ATS.

With all of the "how fast could it REALLY go" posts I was starting to wonder. Between that, rocket powered SR-71s, and Mach 12 X-7s. Yeesh. ATS American Tinfoil hat Society.

 

[overscan (PaulMM)]

Agreed Scott. Sometimes, the US government *isn't* concealing the truth

 

[mz]

Really, this ramjet - scramjet thing and throwing mach numbers around...

AAG: Out of curiousity, in terms of actual,
tested aircraft, what’s the fastest speed that they’ve
ever gotten a hypersonic aircraft up to?

Czysz: We don’t know, because at least publicly we never completed the hypersonic facilities
study – but there were programs in existence inside the classified community that may have
taken the research farther than we did. The X-7, which was a Lockheed scramjet research vehicle
that recovered itself with a long spike sticking in the sand over in the desert supposedly
exceeded Mach 7 or 8.

My group actually tested engines in aircraft past Mach 12 – we had data on some of our
hypersonic glide vehicles when the tunnels were still operating all the way to Mach 20 or 22
down in Tullahoma.

Now, data in many places says the ramjet powered X-7 never went faster than about Mach 4.3 (4300 km/h) which was an air breathing speed record for it's time. Does anyone have any info of any subsequent versions of X-7 after 1960? I'm skeptical myself, but why would Paul Czysz say something like that? Is he wrong or did the interviewer misunderstand? Where the mach 7-8 things only done in a wind tunnel?

Here are some pictures
http://www.ninfinger.org/~sven/models/x_planes/x7.html

This one is a comprehensive story of the X-7 and the family of vehicles:
http://www.designation-systems.net/dusrm/m-60.html

Edit: the plot thickens, here's 1590 from the MX projects list:
MX-1590 Marquardt Development of 20" diameter Mach 3.0 supersonic ramjet (XRJ43-MA)
- MX-1590-A: Controls for XRJ43-MA-1
- MX-1590-B: Development, fabrication & flight testing of XRJ43-MA-3 on MX-1599 (XF-99 Bomarc)
- MX-1590-C: Development, fabrication & flicht testing of XRJ43-MA booster ramjets
- MX-1590-D: Construction of R&D ramjet test facilities at Marquardt Aircraft Co.
- MX-1590-E: Development, fabrication & flight testing of XRJ43-MA advanced components on MX-883 (X-7)

Is that a source of confusion, that it's a ramjet (subsonic internal flow) operating in the supersonic speed range? Scramjet stands for supersonic *combustion* ramjet.

 

[starviking]

"The X-7, which was a Lockheed scramjet research vehicle
that recovered itself with a long spike sticking in the sand over in the desert supposedly
exceeded Mach 7 or 8. "

"Supposedly" i.e. "someone said to me"

Not very firm.

I find it hard to believe myself that a Drone that reportedly hit Mach 4.3 was capable of exceeding Mach 7-8. The speed regimes are just too different.

Colour me 'sceptical'.

Starviking

 

[KJ_Lesnick]

Was the manned Mach-8 strategic bomber developed around the same time as the USN's Manned Hypersonic Interceptor or sometime later?

KJ
BTW: If the SST (Either Lockheed, or Boeing) entered service, do you think it would have resulted in either or both flying?

 

[Lee]

KJ, quoted: "I'm wondering if some supersonic flow through the combustor occurred during the test programme - that could mutate into 'X-7 had a scramjet'. "

Possibly? Rocket engines have supersonic flow in the exhaust throat all the time. At the very least the tailpipe was supersonic, but the combustion chamber? Would flameouts be a problem in a supersonic flow? I admit to not being very knowledgable on scramjet techology.
Also, I've seen the supersonic flow through turbofan, and that kind of engine wouldn't have made a useful scramjet.


"On the caption that the NASP would have replaced the shuttle - I doubt it. The NASP designs all had much smaller payloads than the Shuttle."
"Which NASP are you talking about. The 1964 one, or the 1986 one?"
"I'm not sure by the wording, was it a single stage to orbit, twin-staged? Was the last stage a rocket-powered vehicle?"
"Well, the PDF is talking about the 1986 one. The 60's design was just the study baseline according to the PDF. As for NASP - I always thought it was SSTO. The PDF text mentions a version with an upper stage rocket to go into LEO. It doesn't jibe with what I know about the programme, which isn't much - but there does seem to be a lot of hyperbole in the PDF which makes me leery of taking it at face value."

Here's a site page that shows both designs:

http://www.fas.org/irp/mystery/nasp.htm

NASP-1 and the later version in the site above were SSTO's. Also, slush H2 was considered a performance enhancer to the airframe. This paper goes into some of the theoretical infrastructure necessary to bring it about:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900004952_1990004952.pdf

 

[flateric]

I assume we always should understand the difference of 60s Aerospaceplane and 80s-90s National Aero-Space Plane in historical perspective.

 

[Hood]

According to Jay Miller's 'The X-Planes' the X-7 set a record of 4.31 Mach (2,881mph) using a 36in diameter ramjet. He mentions no further record speeds and this I believe must be the limit of the design.

He mentions no other powerplant than ramjets, although several types were tested (some with Boron fuel). Since there were only 80 successful flights and there were several problems (not with the airframe) I'd doubt any scramjet research was carried out on the X-7.

 

[Lee]

KJ, quoted: "BTW: If the SST (Either Lockheed, or Boeing) entered service, do you think it would have resulted in either or both flying?"

I liked the 'swing-wing' 2707 they chose, but not that big. A business-class-sized model as a demonstration model would have been more reasonable to me.

If they demanded to build and fly the 300-passenger plane, they could have taken out some of the fuel, made the engines smaller as a result with more compressor stages to make up for the original lack of thrust, and lastly, lighten the airframe to reflect less takeoff weight and fly 10,000-15,000 ft. higher.

This R & D approach would have required reruns on mainframe computer design software, but it would have become a better airliner.

To answer your question, if they persisted in flying the big plane, it would been another Concorde, but more expensive, like the Tu-144. A smaller plane would have been more economical, but more units would have been required to be built, so the effect could have been the same as the first case(?) I consider cost and earning economics to be too subjective for accurate estimation because of potentially undefinable future trends.

 

[KJ_Lesnick]

Lee,

I was talking about if the SST flew, would the Mach 8 Strategic Bomber have flown too?

 

[Lee]

I was talking about if the SST flew, would the Mach 8 Strategic Bomber have flown too?

Well, the SST and the Strategic Bomber are different planes going different speeds. Another member stated in the past he thought Mach 3 and Mach 7-8 were way different speed regimes in terms of aerodynamics and I agree.
Different speeds mean different wing/fuselage center-of-pressure issues which also means more strenuous overall balance issues. Bigger engines for the Bomber would mean center-of-gravity problems that might require shifting large amounts of fuel around the fuselage from takeoff to Mach 8.
A Mach 3 SST may not be stable at Mach 8, but then, I realize the X-7 could fly up to Mach 4.13 with the biggest engine and not need redesigning along the way. But, Mach 8-10 would also be different in how it affected the plane, too.
My Dad would tell me when I asked him something like your question, "I don't have enough numbers to be able to say. I need more data that's accurate. It needs to be run through a mainframe and optimized through testing first."
Now I think I see his point, since I've learned 'a thing or two' since I was a teenager. I hope I did, anyway.

 

[KJ_Lesnick]

What I meant to ask was if the SST was developed would the technological developments that were brought about by it, would have made it more likely that the Mach 8 Strategic-Bomber design would have flown?

Or would one have had no effect on the other?


KJ
(Not to sound difficult or anything)

 

[Lee]

What I meant to ask was if the SST was developed would the technological developments that were brought about by it, would have made it more likely that the Mach 8 Strategic-Bomber design would have flown? Or would one have had no effect on the other?

I believe, based on personal experience, that more technological advances would have been required---especially in materials---because aerodynamic heating really climbs in a hurry by the time one is going Mach 8-9.



KJ,quoted: "(Not to sound difficult or anything)"

Naw, you're fine. I've had a good time so far on this blog site. The last one I was on had people with
attitudes(!)

 

[Sundog]

Rocket engines have supersonic flow in the exhaust throat all the time

So do jet engines, that's what a convergent-divergent nozzle is for. However, I have never heard of supersonic flow through a turbofan. I know the USAF was talking about trying to develop one, but to the best of my knowledge, it hasn't occurred. The limiting speed through most turbo-machinery propulsion is between 300mph to 400mph due to the added velocity of the rotational machinery; i.e. if the flow through the engine is 400 mph the speed across a fan blade may be around 700mph (Sea Level speeds for ref), for instance, due to the added rotational velocity.

As for the differences between Mach 3 and Mach 7, they are huge. Because Mach 3 is supersonic and Mach 7 is hypersonic. The difference between the two regimes has to do with gas dynamics. Once a vehicle begins moving fast enough it develops enough heat to change the gas dynamics of the atmosphere it's flying through. i.e.-Hypersonic vehicles aren't flying through "air," but rather, they are flying through air that has been cooked.

 

[Lee]

Lee, quoted: "Rocket engines have supersonic flow in the exhaust throat all the time"

Sundog, quoted: "...I have never heard of supersonic flow through a turbofan. However, I know the USAF was talking about trying to develop one, but to the best of my knowledge, it hasn't occurred. "

I've heard of supersonic turbojet compressors. The J-58 engine of the SR-71 stands out in my mind immediately. I think I stated elsewhere on SecretProjects that I estimated the J-58 would need to consume at least 350 lbs/sec of air to produce 35,000 lbs of thrust. The engine intake face should be only a little bigger than the F-106 engine, so I imply the compressor is rotating supersonically at sea level and made of forged beta-titanium throughout its entirety to handle the strain.




Sundog: "...The limiting speed through most turbo-machinery propulsion is between 300mph to 400mph due to the added velocity of the rotational machinery; i.e. if the flow through the engine is 400 mph the speed across a fan blade may be around 700mph (Sea Level speeds for ref), for instance, due to the added rotational velocity."

Okay, but only at sea level. At altitude, compressor rotation rates decrease with less air entering the engine at subsonic speeds and also at supersonic speeds at very high altitudes.




Here are 2 research reports from the NASA NTRS that may illustrate my point:

Variable-Cycle Engines for Supersonic Cruise Aircraft
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760023129_1976023129.pdf

The Supersonic Through-Flow Turbofan for High Mach Propulsion
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19870014193_1987014193.pdf



Sundog: ..."As for the differences between Mach 3 and Mach 7, they are huge....i.e.-Hypersonic vehicles aren't flying through "air," but rather, they are flying through air that has been cooked."

Oh, yes, absolutely! Flying passage of aircraft/spacecraft at Mach 5 or faster changes aerodynamics more than just *considerably*, and heat is a big issue for the change. I agree completely.

 

[KJ_Lesnick]

Hmmm, then how come an F-105 could do Mach 1.5 at 500 feet off the deck if the airflow speed added to the rotational velocity?

 

[overscan (PaulMM)]

The intake slows the air down to subsonic speeds :

 

[KJ_Lesnick]

Sundog,

If I recall correctly, the J-58 used on the Blackbird had an airflow on the order of 400 lbs/sec. It is bigger in diameter than a J-75 though to the best of my knowledge -- the original J-58 models was of the same diameter at 47-inches. However, the design featured some modifications including what appears to be part of the compressor enlarged for some reason -- Diameter: Approximately 54".

From what I read about the J-91, which the J-58 was derived from the compressor blades did operate in transonic conditions with the flow probably supersonic at the tips under some conditions, however the velocity across the leading edge of the blades on virtually the entire compressor except the tips were subsonic although some parts of the compressor blade (behind the leading edge but ahead of the crest) had supersonic flow on them. Despite this fact, the airflow-velocity at the engine-face was fully-subsonic.

As an interesting note, the two fan-stages of the JT3D/TF-33, which replaced the first three-compressor stages of the J-57/JT3C were actually either the first two compressor-stages of the J-91 or derived from the first two-stages of the J-91.


Overscan,

Believe it or not, I actually know that part -- I assumed what they were saying assumed an inlet was being used which is why it made no sense to me.

 

[Lee]

KJ_Lesnick, quoted: "If I recall correctly, the J-58 used on the Blackbird had an airflow on the order of 400 lbs/sec."

I estimated 350+ lbs/sec, but your estimation would allow a slower rotation speed on the compressor---and you may be correct in your recollection.





KJ: "As an interesting note, the two fan-stages of the JT3D/TF-33, which replaced the first three-compressor stages of the J-57/JT3C were actually either the first two compressor-stages of the J-91 or derived from the first two-stages of the J-91."

I believe you. I saw the engines of the C-141 Starlifter in the Air Force and they put out 23,000 lbs. of thrust with a bypass ratio of about 1.5 and an air intake of almost 375 lbs/sec.

 

[KJ_Lesnick]

I saw the engines of the C-141 Starlifter in the Air Force and they put out 23,000 lbs. of thrust with a bypass ratio of about 1.5 and an air intake of almost 375 lbs/sec.

You know, I had long since suspected the TF-33, and even J-57 was somewhat powerful than their civilian-grade counterparts.


Kendra

 

[Lee]

KJ, quoted: "You know, I had long since suspected the TF-33, and even J-57 was somewhat powerful than their civilian-grade counterparts."

The civilian engines had the same number of stages as the military ones. Even if the thrust should have been the same, I was told(admittedly offhand) that the C-141 Starlifter's nacelles accounted for an additional 2,000 lbs of thrust for the TF-33. On each engine.
That was what I was told. You know how military rumors can be? The information should be taken with a megaton of salt ;D unless you know the truth. Then you can set the other man straight.

 

[KJ_Lesnick]

The civilian engines had the same number of stages as the military ones. Even if the thrust should have been the same, I was told(admittedly offhand) that the C-141 Starlifter's nacelles accounted for an additional 2,000 lbs of thrust for the TF-33. On each engine.

The JT3D variants included the JT3D-1 = 17,000 lbf, the JT3D-3B = 18,000 lbf, and the JT3D-7 = 19,000 lbf. 2,000 extra lbf would be 21,000 not 23,000.

I doubt the nacelle would add any significant amount of thrust.

 

[Lee]

KJ: "I doubt the nacelle would add any significant amount of thrust."

I remember now that an instructor in USAF SAC jet maintenance technical school (Chanute A.F.B., Rantoul, Ill., before it was closed) said what I had asserted about C-141 thrust. He didn't say where he learned it from. We were students and we accepted his word from no experience on our part.
That said, I might be wrong. Orionblamblam is an aerospace engineer; would he know for sure?

 

[KJ_Lesnick]

I wouldn't mind hearing what Orionblamblam would have to say


KJ_Lesnick

 

[KJ_Lesnick]

Let's get back to the primary topic of this particular message: Effects of kinetic-heating versus mach-number on aircraft design

According to this source, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070035924_2007036871.pdf (Page 8 and 9), it says that the V-2 was capable of speeds in excess of Mach 5 but stainless-steel was acceptable for it's design. It stated that aerodynamic heating was a limited concern.

Yet the X-15 which was a later, more advanced design made likely out of even higher grade steels and metals and it only flew on average about 90-seconds (from engine-start, to burnout) powered. Why was the heating such a serious problem on the X-15 in comparison -- temperatures were listed as being very high and some X-15 flights the plane took minor-damage?


KJ Lesnick

 

[starviking]

Let's get back to the primary topic of this particular message: Effects of kinetic-heating versus mach-number on aircraft design

According to this source, http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070035924_2007036871.pdf (Page 8 and 9), it says that the V-2 was capable of speeds in excess of Mach 5 but stainless-steel was acceptable for it's design. It stated that aerodynamic heating was a limited concern.

Yet the X-15 which was a later, more advanced design made likely out of even higher grade steels and metals and it only flew on average about 90-seconds (from engine-start, to burnout) powered. Why was the heating such a serious problem on the X-15 in comparison -- temperatures were listed as being very high and some X-15 flights the plane took minor-damage?

I guess it'll have something to do with the flight profiles. Perhaps the X-15 spent longer at high speed in denser air than the V-2? Also, coming down the V-2 will be much lighter - having burned all its fuel, and will thus be subject to less thermal loading.

Starviking

 

[KJ_Lesnick]

starviking,

I'm not entirely sure how valid that is. The V-2 was launched at sea-level or close to; the X-15 was launched at 35,000 or 45,000 feet? The V-2 actually passes through much denser air on the way up and more on the way down at high-speed.

Kendra Lesnick

 

[starviking]

starviking,

I'm not entirely sure how valid that is. The V-2 was launched at sea-level or close to; the X-15 was launched at 35,000 or 45,000 feet? The V-2 actually passes through much denser air on the way up and more on the way down at high-speed.

Kendra Lesnick

Well, that would depend on how long the V-2 spends in the lower, denser air. Also, going up there'll be the fuel and oxidiser available as heat sinks, and as I mentioned going down the V-2 will be lighter - lowering the thermal loading.

The X-15 is a heavy plane that spends almost all of its time in the atmosphere travelling at up to Mach 6.7, if I recall correctly.


Another point - the V-2 is a one-shot weapon. You can put it through a lot more stress than a vehicle which is designed to be reused.

Starviking