F-108 Rapier Question

[rickshaw]

Rickshaw

The reality was that as they developed the Lightning, the manned bomber threat had been replaced by the ICBM.

So it was bad timing?

In the 1950s, no timing was good as far as UK air defence went.  Read "Battle Flight" by Chris Gibson to see that.  Technology didn't stand still and the threat kept leaping and bounding ahead of slow and ponderous service and even slower government thinking.

The Lightning's value was in showing to foreign and domestic observers that the UK was at least willing to put up at least a token, conventional resistance to foreign incursions into UK airspace.

The end result you mean?

Nope, even from early on.  Without that showing, particularly to the UK's US ally, the US wouldn't have been willing to pour further monies into NATO.

That they weren't willing to fund a replacement for the Lightning until the 1980s

The Tornado?

Yes.  The spirit was willing, there were numerous proposals/projects/etc. but the coffers were empty, with most money going on nuclear deterrence.  "If this thing is going to exist, it's best that it has a British flag on it!"

Instead they misused the Phantom and the result was a severe curtailing of it's life.

How did the RAF misuse the Phantom?  I'm not really familiar with much about the RAF past WW2

Then you should familiarise yourself with it, Kendra/Robynne.  They misused their Phantoms in low-level roles which it's big wing wasn't very well designed for.  While McDonnell's design was perfect for a medium/high-level naval fighter it wasn't very good for a low-altitude land-based strike and ground-attack aircraft.

[martinbayer]

JCF

Robyn, the stainless steel honeycomb structure of the XB-70 was not good for Mach 4.

If I remember the statement correctly, he said the engines and inlets were good for mach 4 operation.

The basic layout of the XB-70 may have been usable for a Mach 4 aircraft, but the aircraft as designed and built was not capable of said speed.

Then what's the point of the J93?  As I understand it, the J93 was designed for WS-110 program, which ultimately became the XB-70.

The engine was needed to produce the necessary speed, thrust, and efficiency the plane required

• The General Electric X279E was the J93-GE-1: It was rated for Mach 4
  
• The J93-GE-3 and GE-5 were capable of the same mach numbers and greater thrust
  
• There is little value in designing a Mach 4 engine for a plane that can only do Mach 3: After all, designing for that speed would require more creativity in material-selection and air cooling, which is more expensive; a lower pressure ratio which could reduce efficiency of the engine, something highly undesirable in a plane where aerodynamics, inlet performance, and engine performance were to be maximized
  

There is a fairly involved discussion of the associated issues at http://www.airliners.net/aviation-forums/tech_ops/read.main/183270/1/#152.

It is not unheard of for initially overoptimistic development targets being reduced once realization of what is technologically realistically achievable inevitably sets in. This can result in individual components having a higher performance potential than the system as a whole can ultimately support.

Martin

[KJ_Lesnick]

Weaver

Well obviously all intercepts have some element of "head-on" at some point, the question is whether you can shoot effectively during that phase.

And usually the answer was no...

1. The curve-of-pursuit seems very similar to tactics used on fighters, with the exception of less maneuvering being involved on the fighter's side.  It's the oldest intercept tactic and trails right on back to WW2 if not earlier.

2. The collision-course seemed to coincide with the development of all-weather interceptors being routine (post WW2).  I know the rockets sucked -- it was simply used because it had a longer range and would more easily bring down a bomber; missiles seemed a logical conclusion.

and missiles had two problems. Firstly, their guidance systems struggled to deal with a high-speed crossing target, and secondly, they either had to fly an energy/fuel inefficient curved path, or they had to try to "lead" the target which added yet more complication to be solved with 1950s electronics.

1. I assume collision-course intercepts still had some probability of success, despite difficulty?

2. Wouldn't it have helped if you came in at a 45-60 degree angle relative to the bomber instead of abeam?  You'd have less "crossing" of the target by the missile and requiring less curvature of the flight path; closure rate would still be lower than head on...

Head-on solved all these problems in theory, but it was only possible with non-nuclear warheads when the missile/radar technology had advanced sufficiently.

The AIM-7. AIM-26, and AIM-47 were at this level correct?

Too many variables.

Okay...

While we're on this, I was wondering if you have an answer here regarding the XF-91

• I know the XF-91 used a J47 and four rockets
  
• Later on an afterburner was fitted to the J47
  
• At some point a radar was fitted to the plane
  

I remember it could do 1.71 or 1.79 mach... was this on full military power and rockets (no radome fitted), afterburning with rockets (no radome) or afterburning, rockets, and radome fitted?

Not good enough to hit a carrier without using a nuke, which is a line you may want to have the option of not crossing.

Makes sense...

The point I'm making is that a carrier is a high-value target that can be destroyed in one hit without resorting to nuclear weapons, which is why it's worth spending megabucks on F-14s and AIM-54s to defend it.

Okay...

Flexible Response was first proposed by the Kennedy administration from 1961. It became formal NATO policy in 1967.

So the US came up with it first... that was always my impression.  Sad that it took us so long to realize that nukes should be a last resort -- not a first resort.

Well you have to remember that Massive Retaliation was a product of the late 1940s when the West had the advantage in nuclear weapons and no appetite, post WWII, to pay for large conventional forces.

Well from 1945 to 1949 at least...

In 1949 the Russians developed a nuclear weapon, and the next year they had the means to deliver them on one way trips (far from desirable as even if they survived delivering the nuke, they'd probably be killed by whoever caught them)

At the time it was seen as a strategic balance between the West's atom bombs and the Soviet's massive armies. As the Soviets gained an equivalent level of nuclear capability, Massive Retaliation began to look more and more like an "everybody loses" strategy

Which it sort of was...

which is why Flexible Response came along.

Sadly it would seem that flexible response took a 6 years before it was universally used, and SAC didn't seem to take it seriously...


Rickshaw

In the 1950s, no timing was good as far as UK air defence went.  Read "Battle Flight" by Chris Gibson to see that.  Technology didn't stand still and the threat kept leaping and bounding ahead of slow and ponderous service and even slower government thinking.

Oh, I'm aware of this... especially these days

Nope, even from early on.  Without that showing, particularly to the UK's US ally, the US wouldn't have been willing to pour further monies into NATO.

Understood...

Yes.  The spirit was willing, there were numerous proposals/projects/etc. but the coffers were empty, with most money going on nuclear deterrence.

Basically, you may nuke us but you will be bombed off the face of the earth in retaliation if you do as well...

If I recall the V-bomber force almost was entirely aimed at countervalue targets... city-for-city, correct?

"If this thing is going to exist, it's best that it has a British flag on it!"

Personally, I think it's good to have your own defense industry so long as you don't let it get so big that it is able to control the economy and make more wars.

They misused their Phantoms in low-level roles which it's big wing wasn't very well designed for.

Well, there were a few low-altitude high-speed flights in the F-4 during it's test-phase... but it wasn't really meant to do it with tanks and bombs on-board.

As for it's performance, I'm surprised it wasn't used alongside the Lightning.  It might have had better missile and radar capabilities, possibly more range.

It's high altitude performance was good, particularly supersonic, as for subsonic, I suppose it could do okay, but I don't know how tight you'd want to turn at altitude.  Optimum turning rates (sustained) tended to be around 15,000 to 17,000 feet on the -B/-C/-D/-E (early).


Martinbayer

1. I remember this thread... regardless there was a statement about the inlet and engines being good for the specified speed.

2. I know the first aircraft had numerous problems with the fabrication of it's skin and hydraulic lines; they were at least partially fixed with the second aircraft.

3. Despite trying to find an audio-recording of the crew specifically calling out Mach and Temp, I never actually got the recording.  I did hear "there's that big magic number boy" and that part.  The statement is essentially meaningless without the mach and temp specified

[jcf]

The J93 family had a service rating of Mach 3.2, that includes the HEF -5 variant.

Was the J93 design capable of Mach 4?, possibly but for an extremely short period of time,
and afterwards would probably be junk. But that is irrelevant as the airframe of
neither the XB-70 as built nor the XF-108 as designed up to cancellation
was capable of continuous Mach 4 flight.

Anyhow what would be the point of a Mach 4 high-altitude bomber? The thing would
glow like a forest fire, even with the best available, and very $$$$, anti-IR coatings
of the period.

Also you seem to think that military power ratings are for continuous output,
they aren't.

You remember the airliners thread, eh? No surprise as based on the style of "Blackbird's" posts
I'm going to hazard the guess that the poster was you. So we have Kendra, Robyn and now Andrea K.
as names, who's the real you? And why are you still tilting at the same windmill?

[martinbayer]

I remember this thread... regardless there was a statement about the inlet and engines being good for the specified speed.

Even if that might have been the case, as I stated before, the fact that individual components might support a certain speed does by no means imply that the integrated system as a whole would do so as well. You see, a chain is only as strong as its weakest link, not as its strongest one.

Martin

[KJ_Lesnick]

joncarrfarrelly

The J93 family had a service rating of Mach 3.2, that includes the HEF -5 variant.

Either they were rated for Mach 3.2 or 4.0...

Was the J93 design capable of Mach 4?, possibly but for an extremely short period of time, and afterwards would probably be junk.

The question I keep raising is why would a person design an engine for a mach number the plane wasn't even built for -- especially when the engine was specifically built for the plane?

They could have used a higher pressure ratio and achieved better performance at Mach 3 if they really were designing for that speed...

But that is irrelevant as the airframe of neither the XB-70 as built nor the XF-108 as designed up to cancellation was capable of continuous Mach 4 flight.

From what it would seem the inlets were designed for it... the XB-70 program was cut back significantly in 1961, though there were cutbacks before that point.

1. Hydraulic lines: This was actually an issue on the first XB-70 design, by the second newer lines were incorporated which fixed some things

2. Honeycomb skin: This was due to fabrication errors mostly, and of course an inability to detect them.  As time went on, fortunately that ability improved as did methods of fixing it

3. Hydraulic fluids/lubrication oils: Not sure to what extent this was addressed

Anyhow what would be the point of a Mach 4 high-altitude bomber?

I guess the idea would be greater speed would make you harder to catch...

[quite]The thing would glow like a forest fire[/quote]Possibly!  As for thermal coatings, they were looking into them: It didn't lower the temperature of the skin, it merely altered the frequency of the emitted energy to those the IRST's wouldn't pick up ideally.

Also you seem to think that military power ratings are for continuous output, they aren't.

Well, if the engines were designed to run on continuous AB, my assumption would be that they'd run whatever RPM was used when the burner was started at, though I suppose it makes sense that the RPM would be throttled down a certain amount of time in.  Still the plane was designed with it's whole cruise portion supersonic.

So we have Kendra, Robyn and now Andrea K. as names, who's the real you?

Andrea K. was a fake name that I used on the airliners forum, I was using that screen-name frequently in 1998-1999 to keep an eye on my step-daughter who was a teenager.  I generally used the same screen-name on other sites as well out of habit (with some exception).  Later on I used the name K.J. because I though it sounded dynamic and Lesnick was the name of a person I knew online; later on I decided the K would be Kendra because I don't know anybody who ever pretended to have the name Kendra.

As for the name Robyn, I simply pulled that out of my donkey quickly when I came back to the same forum where that Lesnick member was located -- I forgot about that detail.  Robyn sounds like a cool name and frankly less hokey than my real name (Hannah).


martinbayer

Even if that might have been the case, as I stated before, the fact that individual components might support a certain speed does by no means imply that the integrated system as a whole would do so as well. You see, a chain is only as strong as its weakest link, not as its strongest one.

True enough, it still strikes me weird that you'd design an inlet for Mach 4, design an engine for Mach 4, then build an airplane that couldn't do it.

It would appear that skin defects, the hydraulic lines were inadequate and needed some work, new lubrication would have been needed and as I've done some checks, my guess is they were lost initially in the cutbacks in 1961; from what I remember the first and second prototypes had a lot of stuff missing from them that the YB-70 and B-70 would have had

• The YB-70 and B-70 were to have a crew of four (Pilot, Co-Pilot, DSO, OSO/Bombardier/Navigator)
  
• The YB-70 and B-70 were to have a functional weapons bay, a bomb/navigation computer, possibly the RWR and ECM jammers, and potentially the defensive missile system the plane was to use
  

.
A/V-1 & 2 only had a crew of two, no functional weapons-bays, ECM, RWR, or defensive armament; the first aircraft didn't even have fully functional fuel tanks (Tank 5) or automated inlets; neither aircraft had a proper fuel-tank sealant

A/V-3 at least had a crew of four, a bomb-nav computer, and a functional bomb-bay: The RWR and ECM system was cancelled so it would either have to be restarted or a new program would have to be put into effect

[martinbayer]

True enough, it still strikes me weird that you'd design an inlet for Mach 4, design an engine for Mach 4, then build an airplane that couldn't do it.

Once again, in real world aircraft design things don't always work out as perhaps originally envisioned or planned. The XFV-12A comes to mind.

Martin

[pyro-manic]

Or it might have been an accident.

Designing something to a set of parameters, it may be possible that it exceeds those parameters through error or conservative design practices. Something that is reduced as the engineering becomes more sophisticated, it very rarely happens now. But back in the '50s it would be entirely possible.

Might I suggest you get some books? You will learn much more that way than by asking a constant stream of questions of people who are not privy to any more information than is in the public domain. Libraries are amazing resources.

[PR19_Kit]

Or it might have been an accident.

Designing something to a set of parameters, it may be possible that it exceeds those parameters through error or conservative design practices. Something that is reduced as the engineering becomes more sophisticated, it very rarely happens now. But back in the '50s it would be entirely possible.

And in the 60s too. In the motor industry the performance of a car could not be predicted as it is these days, and that resulted in lots of development work to produce a car that did what the Product Planning guys wanted it to do. I expect pretty much the same thing occured in the aviation industry of the day.

At least two cars that I worked on proved to be considerably faster than intended in prototype form, and were 'UN-developed' to fit into their intended market niche. That never happened with a Jaguar I might add.  

[KJ_Lesnick]

martinbayer

Once again, in real world aircraft design things don't always work out as perhaps originally envisioned or planned.

Arguably a good point, but usually major performance deviations in terms of speed in those days was generally tied to one of the following

• Excessive drag of the airframe
  
• Inadequate thrust of the engine
  
• Errors in fabrication design
  

.
The J93 was tested by 1962 in a test cell so the temperatures would have been evaluated and it passed, thrust levels would have been known as well; the airframe far as I know was fine in terms of drag, and skin temperatures were as predicted by the way during testing.

This leaves only one thing: Errors in fabrication design which we know are true with the honeycomb skin.  My guess is this would have been better sorted out had better funding been present from 1961 on at least if not 1959.  I would not be surprised if most of the other issues would have been addressed had adequate funding been present, but that's not engineering -- that's politics.


PR19_Kit

And in the 60s too. In the motor industry the performance of a car could not be predicted as it is these days

Maybe true, but in the 1940's the aerospace industry was generally pretty decent at predicting maximum aircraft speeds

As things began to transition to very high subsonic and supersonic, things were iffy, but throughout the late 1940's and early 1950's considerable improvements were made but there were still areas that were not clearly as understood as they should after all we have

• The YF-102: Inadequately area-ruled (ironically they did notice in the wind-tunnel that drag levels were twice as high as predicted, most ignored it)
  
• The F11F-1: Inadequate thrust
  
• The YF-105: Inadequate area-ruling, despite this it could go supersonic in level flight at least at altitude (if not at low level, up high)
  
• The YF-106: Inlet lips were too blunt initially
  
• The F-111: Due to an error in reducing wind-tunnel data, they somehow added nearly every single drag producing device on the afterbody; it was ultimately fixed of course
  

[rickshaw]

Kendra/Robyne, no one here I suspect knows the answers to these questions.  As information about the F-108 is at best quite sketchy and we don't have access to the wind tunnel test data, we cannot answer these questions.   Now, why don't you build us a model/draw us a picture/paint us a picture/etc. and we can all admire it?  We are a modelling website.  This would be more appropriate to Secret Projects.  Please stop trolling us with unending technical questions which I would suggest only the good people at North American (or it's successor corporation(s) ) know the answer to and it's more than likely still classified anyway.   

[tahsin]

Fact: The US Goverment is so going to sue Lockheed Martin.

Fact: Lockmart will wave the American flag and remark on how remarkably Patriotic they are.

Theory: Possibly unpatriotic companies could be named. To stress that the remarkably Patriotic ones are so good for the US to have.

Theory: Like those who "propose and take" Uncle Sam's Money with tales of a  B-70 at Mach 4.

Fact: The contract that stipulates anything like this would be most interesting to see here.

Obvious fact: Any pilot that can coax Mach 2 out of an F-102 will surely be named Capt. Clark Kent. Because he would have to push it himself.

Theory: But then, Lockmart is sure to have a monopoly on Kriptonite...

Fact: The F-102 that made Mach 2 was '102B, became '106. Whose fault it is, why didn't Kelly Johnson point out the fact that Convair was mixing Mirage data?

[Dizzyfugu]

Probably because it was the result of industrial intelligence work. Recently saw a documentation about Marcel Dassault, and his success after WWII, esp. with the Mirage III and its prototypes, severely stirred the US military and the major manufacturers.

[rickshaw]

Well, Ol' Marcel wasn't above using a bit of stolen data either.  Fairey Delta helped his Mirage no end.

[tahsin]

OK, let's  make this even better... Always an amazement that the IAI couldn't make a Mirage with a J-79. Avoid too much questions and comments, people are known to have lost their jobs in aviation companies over this particular one. And yes, how come the US couldn't make a Mirage?