The end of the Second World War in 1945 saw a huge amount of disruption to the international order. The old Imperial powers of Britain and France were very much on the decline, displaced on the international stage in importance by the United States and the Soviet Union. But there was also another factor that had come into existence that also now differentiated the premier league powers from their rivals – atomic weapons.
France had been a leader in radiation and nuclear research before the Second World War and a scientist from that country, Bertrand Goldschmidt, would play an important and often overlooked role in the Manhattan Project that delivered the first nuclear weapons. So, though France suffered great damage during the war, even before the dust had settled that country’s government started supporting an indigenous research program aimed at mainly developing reactors.
However, once the Soviet Union demonstrated its possession of atomic weapons in 1949 and then Great Britain in 1952, France became more interested in developing their own atomic bomb, both for prestige and defensive purposes. A program to develop a weapon began in 1954 and this got a real boost in 1958 when de Gaulle came to power, determined to re-establish France’s position on the world stage. As a result, the first French nuclear test took place in French Algeria in 1960.
But even before this, thought was being given to how the French would deliver their new nukes. In 1955 the Force de dissuasion – also known as the Force de frappe (strike force) – was established. Though this ultimately would include both land-and-submarine based missiles, the initial focus was on bomber aircraft.
Initially these were Sud Aviation Vautour IIB’s, but it was recognised that these aircraft had neither the range nor performance to be effective for the nuclear role.
So, in 1956 the French government requested proposals for a new aircraft to provide their future nuclear deterrent. And they wanted it to be a considerable step up from the Vautour.
The new aircraft needed to be capable of a range of 1,860 miles (3,000km), delivering its payload onto targets in the Eastern Soviet Union from French airbases and then landing at ideally the nearest NATO base or, failing that, a neutral country. And it should be able to perform this at supersonic speed.
This was quite a demand, with only the American B-58 Hustler and F-105 capable of that sort of performance at the time.
But Dassault had just the thing. They had been developing their new delta-winged fighter, the Mirage III, and thought that a scaled up, twin-engine version of that aircraft could meet the requirement. Thus was created the Mirage IV.
Dassault was awarded a contract for development of the new aircraft in April 1957 and by basing the new nuclear bomber on the Mirage III the company hoped to streamline some of the development process, a rather sharp contrast to the huge and expensive bomber programs instituted by the United States and the UK.
The familial similarities are obvious to see between the two aircraft, with the Mirage IV having the same delta-wing layout as the smaller fighter.
The -IV was around one-and-a-half times larger, with double the wing area and gross weight and fitted with twin engines in contrast to the Mirage III’s one. These were Atar 09B’s in the prototypes and -09K’s in the production aircraft, which produced 15,400lbf each.
It also had a second crewman, the systems operator who sat behind the pilot.
But though it bares obvious similarities to the Mirage III and drew from Dassault’s experience in developing that aircraft, the -IV really pushed the engineering used to the limit, and this naturally slowed down development. The manufacturers, which included just about every aircraft builder in France at the time all making various parts of the design, had to test, test and test again every component to make sure that they could withstand the forces being exerted upon them.
Because the Mirage IV had a performance that still is considered pretty remarkable.
The Mirage IV’s original specification called for the aircraft to fly its approach at high altitude, undergo aerial refueling – for which France bought a fleet of Boeing KC-135 tankers – and then make its attack run at a sustained Mach 2 before exiting at the same speed after dropping its weapon. This was an extremely testing requirement for a service aircraft but was achieved. Dassault state that whilst the Mirage III could only manage Mach 2 for a few minutes, the -IV could sustain that speed for a full thirty minutes.
Indeed, the aircraft was rated as having a “safe” top speed of Mach 2.2. In fact, in could achieve more than this, but like many similar aircraft it then becomes a question of excessive heat damaging the aircraft.
To achieve this speed the wings were built extremely thin, indeed, some of the thinnest ever built on an aircraft. But despite this they were able to contain internal fuel tanks while minimising drag for optimal performance at supersonic speeds.
The wing tanks were supplemented with additional tanks in just about every location that Dassault could squeeze them in, including the leading edge of the tailfin. All this meant that the Mirage IV could carry three times the amount of fuel as the smaller Mirage III.
This gave the -IV a comparatively impressive range considering its thirsty engines, but it was still not enough for the French requirement, though that was understood when the design was being considered. Because the French had initially planned to achieve more form the basic design.
The initial version, which would be designated as the Mirage IVA, was intended to provide a nuclear supersonic bomber as quickly as possible. But it was planned to build a larger version, the -IVB, which would be considerably bigger with greater fuel tankage and use twin licence build J75 engines that produced over 26,000lbf each and which would mean the aircraft would be able to return to French bases after an attack on the Soviet Union.
This however fell by the wayside, mainly because the focus on using as many French components as possible became recognised as more important as the aircraft would be France’s primary nuclear deterrent, and so only the -IVA would be built.
The prototype flew for the first time in June 1959, followed by another three development aircraft and then a production order for fifty -IVA’s for service with the Force de frappe was signed in May 1960, with another twelve ordered in 1962.
The complexities of the mission meant that some components had to be especially designed for the aircraft as they were not then manufactured in France and the emphasis on indigenous parts slowed things down somewhat. As it was deliveries, to the French Air Force began in February 1964 and in October of that year the first squadron became operational.
Carrying first the AN-11 and then the AN-22 nuclear bombs, the Mirage IV made France the fourth effective nuclear power, and the aircraft remained that country’s exclusive deterrent until 1971 when ground and submarine-based missiles became available.
Carrying the bomb in a centreline recess, the Mirage IV also had four wing pylons which largely carried drop tanks on the inner racks and ECM gear and decoys on the outer. The pylons also gave the big Mirage the capability to carry 16,000lb (7,250kg) of conventional bombs, though this seem to have been very rarely utilised.
The Mirage IV’s remarkable abilities certainly caught the attention of other operators, and consideration was given by both the British and the Australians to purchasing the aircraft. But this came to naught, and the French remained the only operator.
And though the intent was for the Mirage IV fleet to deter Soviet aggression, it in fact caused waves with France’s allies. One of the reasons for France’s withdrawal from the NATO command structure was partly due to the French refusing to integrate their nuclear deterrent force into NATO planning and control.
Indeed, far less certain of allies’ support in the event of a nuclear strike against them, the French would disperse the entire Mirage IV fleet, with never more than four aircraft on any one airfield and twelve aircraft permanently in the air carrying their bombs to prevent a pre-emptive decapitation strike against the fleet.
That might not be as impressive as the numbers of B-52 or even the RAF’s V-bombers deployed, but it’s important to remember that the strategy behind French nuclear doctrine wasn’t to completely annihilate any attacker. Instead, the French considered it sufficient to have enough capability to wipe out ten major cities in the event of being attacked for their deterrent to be taken seriously.
As it was, the Mirage IVs soon had to adapt to changing circumstance as they found themselves, like pretty much all aircraft of their type and generation, used in a way that they had not been originally intended for. Though designed to make high-altitude and high-speed approaches to their targets the development of Surface to Air Missiles meant that now the -IVs would need to be able to conduct low-level missions. In fact, the Mirage IV proved quite capable of performing well in this sort of profile, though the reduction in range meant that it seems to have been an open secret that, in the event of the balloon going up, the -IVs would be making one-way trips to their targets.
But they continued to provide an important element in France’s nuclear deterrent throughout the Cold War, though with the afore-mentioned entry into service of ballistic missiles they became less critical for deterrence and so could be tasked to other duties. In 1972 twelve aircraft were modified to a new standard, the Mirage IVR, which saw them retain their nuclear capability whilst also being configured to carry a reconnaissance pod.
The rest of the fleet continued to perform their standard deterrence duties, though they would gradually be updated with improved electronics over the years and ultimately in 1979 it was decided to upgrade eighteen of the aircraft to a new configuration, the Mirage IVP. These were fitted to carry an ASMP nuclear cruise missile which, with its low-level capabilities and 300km (186mile) range gave these aircraft an improved stand off capability when the missile entered service in 1986.
These aircraft could also carry a reconnaissance pod, and from 1996 onwards this became the types primary job when they were replaced in the role of nuclear strike by the Mirage 2000. Indeed, though the Mirage IV was an important nuclear asset for France, their practical service was providing reconnaissance in distant lands that the French had interests in, starting with conducting missions over Chad in 1974.
A French archaeologist, Françoise Claustre, was seized by rebels and held captive.
Though the French government began negotiations for her release, they also considered the possibility of undertaking military action and so detailed intelligence of the area suspected to contain the rebel base and their hostage was required. The Mirage IIIR’s that were the French Air Forces main reconnaissance aircraft did not have the range to stage so far, but the -IVR’s, with their aerial refuelling capability did and subsequently flew missions to provide the required photographs.
This typified the primary usage of the Mirage IV, and they would fly many photo-reconnaissance missions over the next few decades, eventually ending their service in 2005. And despite the comparatively low numbers built a surprising amount have been retained, with seventeen currently on display at French air bases and aero museums, including one at the Yorkshire Air Museum in England.
Which is nice, because the Mirage IV, though very much over shadowed by the reputation and success of its smaller and later siblings, was a rather remarkable aircraft and quite a feat of aeronautic engineering.
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