How could the RAF have used the Hawker P1121?

[Archibald]

You have your quote screwed.

 

[sferrin]

You have your quote screwed.

 

[Arjen]

The “stick TSR2 avionics in Vulcan” is almost depressing in it’s complete lack of appreciation of reality.
[...]
I strongly suspect anyone suggesting “just add this platform’s bits to that platform” has never done anything more complex with those platforms than build airfix models of them!

Archibald was quoting Purpletrouble.

 

[zen]

In the context of fitting AI.18 or AI.23 the P1121 can reference it's heritage from 1103 which had AI.18 or continue with AI.23 as was intended.
The volume and weight margins are there for AI.23 with potential for more. Either additional components for Blue Parrot capability or for added illuminator function. Illumination seems solved by the 60's. Hence more Radar Red Top offered at that time.

Plenty of room for other avionics. LABS etc....

 

[pathology_doc]

The critical factors are weight and space, and the space being in the right places.

Sure. But the fact they looked at moving it from the 100,000lb XF-108 to the 40,000lb F-106 suggests there could be more flexibility than Archibald implies.

View attachment 634276

The F-106 had the right space in the right places. You could fit all the black boxes in without having to redesign the airframe, suggesting (if you will) that the system was undersized for the F-108.

 

[sferrin]

The critical factors are weight and space, and the space being in the right places.

Sure. But the fact they looked at moving it from the 100,000lb XF-108 to the 40,000lb F-106 suggests there could be more flexibility than Archibald implies.

View attachment 634276

The F-106 had the right space in the right places. You could fit all the black boxes in without having to redesign the airframe, suggesting (if you will) that the system was undersized for the F-108.

They did add a 5' stretch IIRC to the front end of that F-106. But it was, apparently, a pretty straight forward mod. Then there was the idea of putting the APG-65 in the F-16.



Where there's a will there's usually a way (within limits).

 

[zen]

AI.23 'as is' fitted into tiny spaces in Lightning. P1121 had lots of space in the nose, and frankly the whole section ahead of the inlet seems to be a discrete unit......with implication that redesign of this whole unit is possible.

 

[sferrin]

In the context of fitting AI.18 or AI.23 the P1121 can reference it's heritage from 1103 which had AI.18 or continue with AI.23 as was intended.
The volume and weight margins are there for AI.23 with potential for more. Either additional components for Blue Parrot capability or for added illuminator function. Illumination seems solved by the 60's. Hence more Radar Red Top offered at that time.

Plenty of room for other avionics. LABS etc....

Consider the nose of the original F4H Phantom II with the F-4J.

 

[robunos]

AI.23 'as is' fitted into tiny spaces in Lightning. P1121 had lots of space in the nose, and frankly the whole section ahead of the inlet seems to be a discrete unit......with implication that redesign of this whole unit is possible.

Indeed, my train of thought would be to switch to lateral, 'Mirage' (or P.1129)-style half-cone intakes, and then the entire forward fuselage could be deepened, plenty of room for avionics / weapons, also, no loss of space in a two-seat variant . . .

cheers,
Robin.

 

[zen]

AI.23 'as is' fitted into tiny spaces in Lightning. P1121 had lots of space in the nose, and frankly the whole section ahead of the inlet seems to be a discrete unit......with implication that redesign of this whole unit is possible.

Indeed, my train of thought would be to switch to lateral, 'Mirage' (or P.1129)-style half-cone intakes, and then the entire forward fuselage could be deepened, plenty of room for avionics / weapons, also, no loss of space in a two-seat variant . . .

cheers,
Robin.

If they reuse the 1103 front end they can fit something as large as AI.18 with a 30 inch diameter dish. So no need for complete redesign of entire forward half of the aircraft.

 

[zen]

In the context of fitting AI.18 or AI.23 the P1121 can reference it's heritage from 1103 which had AI.18 or continue with AI.23 as was intended.
The volume and weight margins are there for AI.23 with potential for more. Either additional components for Blue Parrot capability or for added illuminator function. Illumination seems solved by the 60's. Hence more Radar Red Top offered at that time.

Plenty of room for other avionics. LABS etc....

Consider the nose of the original F4H Phantom II with the F-4J.

View attachment 634280

View attachment 634281

Original F4 was designed for 24" diameter dish system.

 

[Purpletrouble]

The critical factors are weight and space, and the space being in the right places.

Sure. But the fact they looked at moving it from the 100,000lb XF-108 to the 40,000lb F-106 suggests there could be more flexibility than Archibald implies.

View attachment 634276

The F-106 had the right space in the right places. You could fit all the black boxes in without having to redesign the airframe, suggesting (if you will) that the system was undersized for the F-108.

They did add a 5' stretch IIRC to the front end of that F-106. But it was, apparently, a pretty straight forward mod. Then there was the idea of putting the APG-65 in the F-16.

View attachment 634279

Where there's a will there's usually a way (within limits).

What was the common factor in these “put bits in something else” success??? oh yes, it was that they were from the same generation so you had a reasonable chance.

Not the sillyness of trying to put stuff into previous generations ala TSR2 into Vulcan. The same fanboy level thinking that gives us projects like Nimrod MRA4 and many other chaotic monsters.

 

[sferrin]

What was the common factor in these “put bits in something else” success??? oh yes, it was that they were from the same generation so you had a reasonable chance.

Not the sillyness of trying to put stuff into previous generations ala TSR2 into Vulcan.

Not sure what you're trying to say here. TSR2 stuff wouldn't fit into a Vulcan? That new generation stuff can't be put into an older airframe?

 

[Purpletrouble]

That it doesn’t normally go well when people try for good engineering reasons but which tend to be overlooked or ignored by those in comfy chairs, be they amateurs or supposed professionals!

 

[sferrin]

That it doesn’t normally go well when people try for good engineering reasons but which tend to be overlooked or ignored by those in comfy chairs, be they amateurs or supposed professionals!

Be more specific. What are you trying to say? There are tons of examples of successful upgrades, mods, and retrofits. I'd go so far as to say, "it can't be done" is a rarity.

 

[Archibald]

Folks,

There is no reason why an old but a) roomy and b) robust enough airframe can't be adapted through generations and generations of new technologies.
Most startling example is the B-52. In fact it is probably easier for bombers than fighters for the simple reasons bombers have more internal space.

There is another issue, however, which unfortunately applied a lot to GB aerospace industry in the 50's / 60's.

That is, for all kind of complicated reasons, they tended to botch and screw a lot of things.

A close analogy is late 30's French aerospace industry, which was a complete train wreck plagued with a bazillon of crippling issues, all over the place. From RFP to combat missions, NOTHING worked properly - pilot training, industry, engines, bombsights, tactics, propellers - every single bit of combat aircraft was deeply flawed.

Basically, there were in both cases systemic issues running very deep that led to absurd decisions, waste, cost overruns, cancellations - and then, rinse, repeat, rinse, repeat over and over.

In the end - the case of B-52 and Vulcan are exemplary. There is no reason a Vulcan could not pull a B-52 and get regular updates (including some TSR-2 very advanced stuff) without bursting the airframes limits.

Problem is to keep those upgrades under control - you need good management by the military & government, contractors in good health. Also a decent budget. GB in the early 60's had none of that - the overall situation of the aerospace industry, military, government and economy was kind of deeply rotten. Basically, a very bad environment.

Despite McNamara being a despicable bureaucrat, fact was the US military budget was colossal and their aerospace industry was top notch.

 

[pathology_doc]

oh yes, it was that they were from the same generation so you had a reasonable chance.

If anything, electronics should be an easier fit into an older airframe as they tend to get smaller for the same capability. The issues that have to be solved, depending on what you're putting into what and in which technological era, include (for example) determining whether it's possible to combine digital and analogue systems OR deciding whether to simply gut the older avionics and completely rewire the airplane. I'd be surprised if there's a single instrument or gauge in any surviving B-52 that is the same as when it was built, although it would be interesting to know how much commonality there was in 1982 (in which year I'd argue that the Vulcans which flew the Black Buck missions in that year probably had MOST of their instruments and gauges the same as built).

Once upon a time, I was a young fool who didn't understand why you couldn't just slap a sextet of AMRAAMs onto the racks of a Lightning F.53 (for example). It took me a LONG TIME to understand the importance of systems integration, economies of refit, etc., but when I did, I found these fields a fascinating area of study.

 

[pathology_doc]

They did add a 5' stretch IIRC to the front end of that F-106. But it was, apparently, a pretty straight forward mod.

It could be argued that stretching the nose of P.1121 to fit in a slightly larger radar or an illuminator or what have you would have been equally possible. But it would be a different question with a Lightning.

 

[sferrin]

They did add a 5' stretch IIRC to the front end of that F-106. But it was, apparently, a pretty straight forward mod.

It could be argued that stretching the nose of P.1121 to fit in a slightly larger radar or an illuminator or what have you would have been equally possible. But it would be a different question with a Lightning.

You'd probably have to do like China did with the J-8 and do a completely different nose.

 

[pathology_doc]

You'd probably have to do like China did with the J-8 and do a completely different nose.

At that stage it's fair to say that you don't have a MiG-21 any more. Terms like "inspired by" and "developed from" get bandied around.

 

[sferrin]

You'd probably have to do like China did with the J-8 and do a completely different nose.

At that stage it's fair to say that you don't have a MiG-21 any more. Terms like "inspired by" and "developed from" get bandied around.

They didn't have a MiG-21 at the beginning either. That's a twin-engined aircraft.

 

[zen]

They did add a 5' stretch IIRC to the front end of that F-106. But it was, apparently, a pretty straight forward mod.

It could be argued that stretching the nose of P.1121 to fit in a slightly larger radar or an illuminator or what have you would have been equally possible. But it would be a different question with a Lightning.

You'd probably have to do like China did with the J-8 and do a completely different nose.

View attachment 634284

View attachment 634285

Errr not really.
You see from the inlet which is the same for P1103,P P1116, P1123 and the final P1121 twin seater to the exhaust nozzle is the same for P1121 original to P1121 final offering. What changes is the section ahead of the inlet.
Because the nose gear is under the inlet, the whole section from cockpit to nose is something alterable.

In fact that's pretty much what happened as the cockpit to nose section is attached at the bulkhead behind the cockpit to the rest of the fuselage.

 

[sferrin]

They did add a 5' stretch IIRC to the front end of that F-106. But it was, apparently, a pretty straight forward mod.

It could be argued that stretching the nose of P.1121 to fit in a slightly larger radar or an illuminator or what have you would have been equally possible. But it would be a different question with a Lightning.

You'd probably have to do like China did with the J-8 and do a completely different nose.

View attachment 634284

View attachment 634285

Errr not really.
You see from the inlet which is the same for P1103,P P1116, P1123 and the final P1121 twin seater to the exhaust nozzle is the same for P1121 original to P1121 final offering. What changes is the section ahead of the inlet.
Because the nose gear is under the inlet, the whole section from cockpit to nose is something alterable.

" It could be argued that stretching the nose of P.1121 to fit in a slightly larger radar or an illuminator or what have you would have been equally possible. But it would be a different question with a Lightning."

 

[zen]

Yes I agree.
You'll need something like the solid nose on the VG offering for fitting more avionics into the nose of a Lightning.
I agree entirely with that fact.

Which is one of the major constraints on the Lightning and one the P1121 doesn't have.

 

[JFC Fuller]

Thinking about this a bit more, would it have been possible to strengthen the inner-wings to take a triple ejector rack as proposed for the Buccaneer? Then a potential load out could be six 1,000lb bombs on the inner wing pylons, 2 Red Tops (or Sidewinders) on the outer wing pylons and a single 200 gallon fuel tank under the fuselage. Combined with the Conway engine and Airpass II radar it would have made for a very interesting strike fighter, potentially something that could have proven more attractive to the Australians than their Mirage IIIs considering the timeline on which they bought them.

 

[Archibald]

I see what you did here - a half-between Mirage III and F-111, somewhat like... the Phantoms the RAAF loaned in the late 60's.
Except available right from 1961, and so potentially sweeping away all three above. Also, P.1121 in Vietnam - now that would be awesome.

 

[Purpletrouble]

That it doesn’t normally go well when people try for good engineering reasons but which tend to be overlooked or ignored by those in comfy chairs, be they amateurs or supposed professionals!

Be more specific. What are you trying to say? There are tons of examples of successful upgrades, mods, and retrofits. I'd go so far as to say, "it can't be done" is a rarity.

Anything “can be done”. Of course it can, well, bar the laws of physics (“Jim”). And even they can be bent with some ingenuity and/or a lot of money.

It’s the “should it be done” that is where “yes” becomes the rarity.

Just off the top of my head engineering reasons: power supplies, CG balancing, EMI/EMC, structural interactions such as vibration/heat (self and external), software, integration with existing and retained equipment, fire, damage and failure considerations and so on all day long. The detail of stuff that whilst a bit of kit X from platform Y has been put on platform Z, it comes with a host of maintenance and operational issues - most of which are not publicised.

And this is before we get to complex programme management. At which it seems nearly everyone os awful.

Porting TSR2 into Vulcan would require redesigning Vulcan (ok you can have most of the external shape bar new engines for gennys for the TSR2’s avionics power requirements). The exact same kind of problems the UK had with Nimrod Mks 3&4 and which snowball across the whole platform. Could it have been done eventually? Yes? Was it sensible/should it have been done? No - build TSR2 and spec it as a Vulcan as hat’ll be easier (that also failed!).

B52 is different- the core build lasted much longer and upgrade was incremental, plus never attempted to bring across whole capabilities and systems from say F111/B1/2 generations. Not to mention the vast resources the US had at its disposal vice UK. A B52 is huge compared to a Vulcan, which is a 1/3rd the size and designed earlier. Has the US tried to fit F15E avionics to it?

As an example - a hardpoint for a missile needs a bunch of avionics boxes to control that and what goes on it. They need to be near the hardpoint, accesible and with dedicated wiring to the hardpoint and back through the aircraft to the firing system. The box will get hot and needs cooling from the aircon system (ECS) which then needs certain diameter pipes and a system sized to generate and supply that including bleed air offtake, volume and weight. Prior to software controlled systems the physical cards/wiring of the box was the software and so any change to the weapon meant redesigning the box - changing latency, weight, power required, heat generated and cooling needed. This is huge work. Imagine a Vulcan needing more power, more bigger gennys on the engines, more powerful engines to run them and provide air for cooling, more fuel being used to do all this. Avionics very different sized and weighted in different places. The end result won’t be a Vulcan as we know it and it won’t be with us quickly. It’ll still be slow and not low level capable, which is what the TSR2 avionics were specifically based around, so why are we doing this again?

Ultimately the point is what the MoD was trying to get industry to do in the 60s, move away from focussing on platforms with avionics as an afterthought limited to the size of lump (as P1121 was) and to an integrated weapons system where all of it was considered together from the outset and developed as such. TSR2 failed although not for that reason, but MRCA clearly shows the direction. Even today with common standards and software allowing us to not physically have to change many things, it is still diffifuclt (slow and expensive) to upgrade or change things.

So the point is, it is not about “the nose is long enough” although of course that is a factor - but the mass of detailed engineering considerations that people are (understandably) blind to if they haven’t done any of this. History shows even the professionals can be blind to this, although arguably politics often drives things that engineers feel are ill advised, and are usually proved correct!

apologies for length!

 

[zen]

In the context of the subject.
P1121 was designed around the fitting of AI.23 into the nose, and the final submission as a twin seater is highly likely to have yet another variation on the AI.23 set in a reprofiled nose and cockpit section. Very probably something closely related to Blue Parrot and almost certainly retaining AIRPASS's interception capabilities.

The volume for additional capability is there and more is achievable.

All this talk of TSR.2 electronics into Vulcan is a complete side issue.

 

[Mike Pryce]

I spent a year going between Harrier and Typhoon teams looking at lessons each could learn about upgrades.

Everything Purpletrouble says, and more, is true. Easier to build a new plane sometimes.

I recall one component was expected to need 'the arm of a giant with the hand of a child' to get at.

I used to teach about updates by making students crawl under a Tornado and stick their heads into Zone 19. The horror, the horror.

P1121 does not look like the worst offender for complexity, but wires and cooling etc. are a nightmare for most aircraft.

 

[sferrin]

I recall one component was expected to need 'the arm of a giant with the hand of a child' to get at.

I used to teach about updates by making students crawl under a Tornado and stick their heads into Zone 19. The horror, the horror.

Oh, I NEVER said it was always easy. Even right on the factory floor, building it the FIRST time, one can wonder WTF designers were thinking. (They weren't and one could be forgiven for thinking they'd never heard the term, "design for manufacturing".) Currently trying to figure out how to safely break Hi-Lite collars, that require the strength of the Six-Million Dollar Man in a location that you could almost fit a baby arm into, IF you could fit a baby in the area around the location.

 

[Mike Pryce]

The AV-8B remanufacture programme, with new fuselages and old wings, made a lot of sense. Easier to fit new bits into fresh fuselages, even though it is.indeed hard enough on the production line.

That Harrier wing removal palaver was a pain in the field, but it made it 'modular'.

 

[pathology_doc]

It’s the “should it be done” that is where “yes” becomes the rarity.

Just off the top of my head engineering reasons: power supplies, CG balancing, EMI/EMC, structural interactions such as vibration/heat (self and external), software, integration with existing and retained equipment, fire, damage and failure considerations and so on all day long. The detail of stuff that whilst a bit of kit X from platform Y has been put on platform Z, it comes with a host of maintenance and operational issues - most of which are not publicised.

That's the problem here. We can look at the aircraft and their approximate shapes and volumes, and say "You know what? That would probably fit, based on what we know of the internal volume." But we'll never know about the some of the bits in bold.

And while it's valid for you to give us the fifty gazillion reasons why it would probably not have worked, or won't necessarily work every time, the ongoing upgrades and reconditioning of some combat types to keep them going long after you'd think their usefulness was at an end (e.g. the B-52, early marks of Phantom and Skyhawk renewed with late-alphabet suffixes) points our eyes with hope (admittedly sometimes too much hope) to all the times it WAS possible.

P1121 does not look like the worst offender for complexity, but wires and cooling etc. are a nightmare for most aircraft.

I found it enlightening to read, in Damien Burke's TSR.2 book, of how horrified the English Electric people were at how little detail attention Vickers had given to this.

 

[zen]

How plausible is it fund a P1121 variant for FGA mission set?

Perhaps one factor in it's favour would be clearing it for Red Beard....

Ordered as Fighter Attack FGA mk1 1958
First Flight 1960, some 64 aircraft plus one development aircraft. IOC '61?
FOC Cleared for 3" rockets, 500lb bombs, 1,000lb bombs, napalm, 60lb warhead rocket, single 30mm ADEN 600 rounds?
In Fighter mission, 2 Firestreak AAMs and AI.23 AIRPASS.
LABS system, Nuclear delivery for Red Beard, a limited number of machines designated FGA mk1B by early 60's.

1960 upgrade 18 round SNEB Pods and LABS to rest of fleet, designated mk1*

FR mk2 ordered 16 for 1961. AI.23 removed and new nose section with multiple cameras.

Two seater FAW mk3 ordered 1960 for 70 aircraft.
Equipped with 2 Red Top and 2 Radar Red Top, integrated AI.23 AIRPASS with illuminator function and ISIS.
Delivery 1962?

FAW mk4 ordered 1964 for 56 aircraft.
Including extending IFR.

Assuming NMBR.3 fails, P1154 deferred to future spending and 1963 limited number of 40 two seater FGA mk5 ordered. Cleared for WE.177, AS rocket ???.
Further 30 ordered after AFVG failure as interim to UKVG. Cleared for Martel.
All 70 tasked for nuclear strike MRI.

Additional 70 mk6 cleared for wide range of munitions new systems and new engine RB.172 named Severn. Forms offer to other European states as successor to Starfighter.

 

[Purpletrouble]

I do apologise for the party pooper meme, but the devil is always in the detail, and even when things appear succesful, those that actually work with then will often tell a different story. The temptation to take a successful legacy platform and modernise it with the latest stuff is incredible - yet it so rarely works out because there are so 1000s of decisions that are in the legacy design precisely because it had legacy stuff. That’s before we get to the poor buggers who have to maintain it in practice and deal with the boundaries between new and old and a 1000 more unknown complications. As for Zone 19, every tonka technician should get compensation for the PTSD that has left Ruddy ancient RHWR crate requiring removal to get anything, never look at the control rod crush struts and don’t even mention the ECS water extractor...

An, much as I love P1121, I think the criticism on weapons system grounds was very justified.

Earlier the hot/cold aspect of RAF/MoD support was raised and this was ascribed to “leading Hawkers on”. I think that is wrong, and misses that the RAF is (and was) a collection of competing ideas, plans and wants. As people over the years move round, their ability to influence and make decisions changes, as of course can their mind (ok joking on latter, no Air Marshal ever does that!). Hence what you see is the outcome of different agendas at different times with different traction.

For all the “we see the future as integrated weapon systems not this obsession on platform performance”, there would be as many “this is a super version of what I liked flying and I want it”.

The same can be seen today. Typhoon was of course to be succeeded by UCAVs, and for a decade plus all thar was ever talked about and R&D funded was autonomous UCAVs. Every man and his dog was adamant that high agility, self fighting UCAVs were just around the corner and Taranis was the next EAP.

If like me you wondered how to replicate the incredible decision making ability of a pilot (I feel a bit sick praising them tbh though) in a computer, and how secure/reliable a comms link can ever be - you got put back in your box because we could save on a seat and cockpit. Plus we’d never need to train, and could just “break glass case in emergency”.

Now, after 2 decades of operating UAVs and masses of research and thought into UCAVs, we have the manned Tempest project. Go figure!

err, another long post!

 

[overscan (PaulMM)]

Here's Deputy Chief of the Air Staff Air Vice Marshal G.W. Tuttle's take:



You are completely correct in saying that concepts like "The Ministry" hide the complexities of a variety of different people with different views. There was the Air Ministry, the Ministry of Supply, each containing many different people with different views. Some were giving tacit encouragement while others viewed looking at P.1121 as a total waste of everyone's time. At times it seemed that the Air Ministry's job was demand the highest spec possible, knowing it wasn't their job to deliver it, while the Ministry of Supply's job was to spend as little as possible in delivering something at least vaguely filling the requirement. The Ministry of Supply wouldn't want to stop Hawker spending their own money doing their job, funding development of a plane.

Often, the problem wasn't finding money to build the designs but to undertake the basic technical research necessary to meet the overly ambitious specifications emanating from the Air Ministry OR department.

Sir Thomas Pike ( Air Officer Commanding-in-Chief RAF Fighter Comand) was strongly supportive of the 'multirole fighter/bomber for limited wars' concept, and in general the senior RAF officers were more supportive of Camm and the P.1121 than the younger staff of Operational Requirements, steeped in the latest technologies and buzzwords and at times contemptuously dismissive of the P.1121.

 

[Mike Pryce]

Tuttle and Kyle. Camm's "Evil bloody Air Marshals"?

It's always nice to get someone else to pay for your insurance policy.

 

[zen]

OR.329......isn't that F.155T?

Or to put it another way a superlative set of requirements for a dedicated interceptor so extreme that NO aircraft entering service in the early 60's met it. Not even the vaunted MiG.25 on the other side.

Meanwhile the kind of performance the P1121 was expected to reach, was in the ballpark for a host of high end aircraft in that era.

 

[overscan (PaulMM)]

OR.329 = Air MInistry Requirement
F155T = Ministry of Supply Requirement to fulfil OR.329

 

[JFC Fuller]

This comes back to why the RAF bought/buys aircraft, and its something that often gets lost. It's easiest to understand in the terms of interceptors and F.155T is a great example. The requirement was based around meeting the perceived threat, a supersonic bomber carrying a stand-off missile. That drove a host of sub requirements from the interceptor system; the warhead requirements for the missile, which drove the size of the missile, the speed and range requirements for the aircraft, the detection and engagement range of the radar etc., etc. Mixed with the technology of the time it soon drives the design process towards something as massive as the Fairey Delta III. This seems exorbitant when viewed in a vacuum but to the decision makers it was binary, analysis was telling them what the threat was and anything that couldn't meet that threat was pointless. That we now know the analysis of the threat was wrong does not change the fact that it was perceived to be right at the time. The quote from DCAS Tuttle that Paul posted outlines this in blunt terms, in the mid-late 1950s there were two big aircraft requirements, OR.329 and GOR.339, both of these were derived from analysis of perceived need and the P.1121 could meet neither.

From an Alternative History perspective the options are therefore an OR to a different requirement; my suggestion being the Venom Fighter-Bomber replacement, or a radical re-writing of the two OR's mentioned above. My reasoning for the Venom replacement being that I suspect the P.1121 could have met all the range, speed, payload and nav-attack system requirements of the later Hunter FGA.9/FR.10 replacement, although it obviously wouldn't have provided the STOVL element. Equally, the timeframes can be made to work by making the Venom replacement programme a better funded project that is initiated earlier, around 1956, but with a similar in-service date (1960/61).

 

[overscan (PaulMM)]

Alternatively a more correct assessment of the actual threat could have resulted in a less ambitious set of requirements.