At present, the strategic bombers of the major powers are developing to stealth penetration, rather than blindly pursuing the previous high-altitude high speed, and as far as the speed of manned aerial vehicles is concerned, all the current fighter speeds have not exceeded Mach 3, but the 60s of the last century is a special era, is the era of supersonic manned aerial vehicles, at that time the two major powers are higher, faster and stronger as the goal to design reconnaissance aircraft and interceptors, at that time the maximum speed of the aircraft can break through Mach 3, There are a number of high-sonic aircraft put into use, such as the MiG-25, SR-71, these aircraft have entered the military service, but there are also ambitions to die before pay, such as the XB-70, the speed of this bomber can also exceed Mach 3, and is the first manned aircraft in the history of aviation to use the concept of wave-riding body design, and almost became the first nuclear-powered bomber, nicknamed": "Valkyrie", then this article will talk about the Valkyrie strategic bomber.
The mach troika bomber that died prematurely: XB-70
< H1 class= "pgc-h-center-line" > dropped nuclear bombs on Soviet soil</h1>
Since the curtain of the Cold War fell, the United States and the Soviet Union have scrambled to develop strategic bombers, and they want to be able to carry out strategic in-depth bombing or directly drop nuclear bombs on each other in the event of a war one day, and there must be a shield for spears, and since bombers can drop bombs on my territory, then I must have corresponding defensive weapons to intercept your bombers, such as interceptors, or anti-aircraft missiles. Therefore, around the 1950s, supersonic fighters appeared one after another, and the speed of the bombers on the attacking side could not keep up, and at that time there was no concept of bomb dropping outside the defensive zone, and if our bombers entered the territory of the other side and were intercepted and shot down by the interceptors of the other side, there was no point in developing such bombers.
Therefore, in this context, the development of supersonic bombers was put on the table, as far as the United States is concerned, if it wants to penetrate the Soviet air defense network deep into the Soviet hinterland, the bomber must have high-altitude and high-speed conditions to prevent the interception aircraft from being easily intercepted. Therefore, in contrast, the B-52 at that time was completely unable to meet the conditions of high altitude and high speed, after all, the limit speed of the B-52 was only Mach. Therefore, after this, the B-58 bomber appeared, but the B-58, in addition to barely breaking through the speed of sound in terms of speed, was not as good as the B-52 in terms of range and combat radius, and its two Machs could only reach mach two when it was doing a breakthrough sprint to open the afterburner, and in the usual flight, it could still be caught up by fighters and anti-aircraft missiles.
The B-58 bomber's Two Mach dash still did not meet the requirements
Therefore, only a breakthrough of Mach 3 is the ultimate solution, after all, at that time the Soviet Union did not have a speed of Mach 3 fighters appeared, and the soviet early anti-aircraft missiles could only reach Mach 2.4 maximum speed. In 1955, the U.S. Air Force conducted a design tender for a new strategic bomber program, according to the requirements of the military, the new strategic bomber can sprint at a speed of Mach 3 at an altitude of 21,000 meters, and can also cruise at a low altitude at a speed of Mach 0.9, in addition, the aircraft must not be refueled in the air, in order to be able to pose a threat to the Soviet Union for a long time, the aircraft must have the ability to fly for a long time, that is, have nuclear power! It is possible to fly in Soviet airspace for a long time.
The companies involved in the tender were North American and Boeing, whose solutions generally met the requirements of high-altitude hypersonic speed, but also exceeded the requirements of the military a little, and the maximum take-off weight of the XB-70 in their design reached 450 tons. Therefore, in 1957, the military gave a restriction that the maximum weight could not exceed 222 tons, while the ceiling was raised to 23,000 meters. On December 23, 1957, North American companies won the bid, and on January 24, 1958, North American Airlines signed a contract with the military to build a prototype, while General Electric was responsible for the development of high-energy fuels.
North American Airlines
<h1 class="pgc-h-center-line" > how to achieve Mach Thransa</h1>
Want the aircraft to achieve the flight of Mach Thon, the first thing to solve is the shock resistance problem generated by the aircraft when it is supersonic flight, because the aircraft will produce shock waves on the surface of the body when it is transsonic flight, which makes a large part of the thrust of the fighter engine used to overcome this shock resistance, but the designers of North American Aviation have cleverly used the energy generated by the shock wave, and the designers have cleverly designed the high pressure area of the shock wave through the underside of the wing. This allows the XB-70 to generate additional lift of 30% of the total lift during flight, which improves the lift-to-drag ratio of the XB-70, and the XB-70 can further reduce the drag by using a smaller angle of attack during cruising.
In the design of the pneumatic layout, the XB-70 adopts the overall layout of the canard, no flat tail, and small triangular wing with a small scale ratio. The main wing swept angle is about 65.5 degrees, the wing ends on both sides are hydraulically variable design, which can be switched back and forth between 25 degrees and 70 degrees according to the needs of high-speed flight, 70 degrees is the angle of the second prototype, the maximum angle of the first is 65 degrees, and for such a foldable wing tip design, in addition to making the aircraft form a wave-riding body shape, it can also play the role of part of the vertical stabilizer to increase the direction stability of the B-70, and can cancel the upper anti-angle effect when performing supersonic flight.
The general layout of the XB-70
In addition, there is a problem with the material, XB-70 will produce a temperature of more than 400 degrees Celsius when flying in Mach 3, although the heat resistance of titanium alloys is very good in the 1950s and 1960s has been widely used in the aviation field, but titanium alloys are also very expensive, accounting for only 9% of the structural materials used, and most of the body uses two layers of copper-plated stainless steel sandwiched between a honeycomb structure, accounting for 68%, Some other parts of the fuselage rely on fuel circulation cycles to absorb heat. Another point is the problem of paint shedding during high-speed flight, which was also encountered by the Soviet MiG-25, and the XB-70 was also the same, in a test flight due to the low melting point of red paint caused all the red stars to be blown off, and then replaced the red stars with higher melting points to solve the problem, but the white paint also encountered a similar problem, because most of the XB-70 body was painted in white paint, although it can withstand high temperatures, However, due to the soft shell structure, the patent skin of the white paint fell off in a large area in the cycle of high and low temperatures, and this problem was not fundamentally solved before the Valkyrie was encapsulated, and their delaying strategy was to re-paint every ten flights or re-spray before the public display.
XB-70's white patent leather peels off
Of course, the most important thing is the direct power source, the machine uses 6 General Electric J93-GE-3 turbojet engines, each engine can produce 14060 kg of after-force thrust, because the resistance of Mach Thoms is also very large plus 6 engines, so the fuel consumption of the XB-70 is also very large, so the fuel load XB-70 is close to the B-52 to reach 136 tons.
The XB-70's J93-GE-3 turbojet engine
< h1 class="pgc-h-center-line" > problems encountered in project development</h1>
The first part also mentions that XB-70 was also required to use a nuclear reactor to provide power when the project was established, but in the subsequent development of the project team and the military leadership are aware of the impossibility of the nuclear power scheme, first of all, the project team can not achieve a small nuclear reactor that can be loaded into the fuselage, although there were already nuclear-powered aircraft carriers and submarines at that time, but such an aircraft and the two compared to the volume is obviously not at the same level, and for the technology at that time to achieve the miniaturization of airborne nuclear reactors is very difficult, According to the design team's plan, the minimum weight of the nuclear reactor must reach 200 tons, which is close to the maximum take-off weight allowed when the plan is tendered.
And the military also took into account the nuclear pollution problem generated by the nuclear reactor, first of all, not to mention whether it can do enough safe protective measures for the air crew members, from the public point of view, the development of nuclear-powered aircraft at that time was not too mature, if installed on such a flying supersonic aircraft is undoubtedly a sword of Damocles hanging on the heads of the people of the United States and the Soviet Union, once the failure causes the crash or is shot down will cause nuclear pollution to the crashed area, And if it had crashed inside the Soviet Union, the consequences would have been tantamount to a small-scale nuclear provocation. So under these multiple considerations, the military eventually removed the nuclear power requirement from the XB-70 program. On the other hand, GE's high-energy fuels have not been successfully developed, so they have switched to ordinary fuels.
The nuclear-powered bomber program ultimately proved unfeasible
In addition, a problem is the situation and financial problems caused by the development of the times, when the XB-70 was just established, the Soviet anti-aircraft missile theory speed theory height could not pose a threat to the XB-70, but the development of the XB-70 could not keep up with the development and progress of the Soviet anti-aircraft missile, and in just a few years the SAM anti-aircraft missile made great progress, which directly led to a U-2 high-altitude reconnaissance aircraft being shot down by the SA-2 missile in 1960, which also affected the development of the XB-70. Because this means that the Soviet Union's high altitude is no longer safe, and the cost of the XB-70 on the other side is too expensive, according to the air force budget XB-70 will eventually be put into production, it will cost 750 million US dollars, it should be noted that this is only 750 million in the 60s, and it is 10 billion US dollars to put it to the present, which is completely astronomical, and it has always been very cheap compared to the B2 that only 21 aircraft were built because of the high cost. Therefore, during the Eisenhower administration, the government continued to argue with the Air Force over funds, which also slowed down the overall progress of the XB-70, and when Kennedy took office, the XB-70 first received a huge appropriation, but finally the government decided to finally abandon the construction of the aircraft, and the original production of 6 prototypes was reduced to 3.
XB-70's R&D funding was once squabbled
<h1 class="pgc-h-center-line" > characteristics of Mach Thrancher's genius</h1>
XB-70's start-up speed is very fast, compared to the SR-71 liters unprecedented need to prepare for more than half a day, XB-70 from start-up to liftoff only takes 25 minutes, and its crew do not need to wear thick spacesuits like also Blackbird, eliminating a lot of cumbersome processes. The XB-70's belly could carry up to 11.34 tons of bombs, and the design of the mounted missile was also considered at that time but was not used later; the cockpit of the XB-70 had extremely advanced electronic equipment at that time, and it was precisely because of the installation of these advanced electronic equipment that the crew of the XB-70 was reduced to 4 people, namely the main and co-pilots, and the bomber and the bomber and the navigator were eliminated in the subsequent design.
The cockpit of the XB-70, with a large number of various instruments, was a very advanced cockpit at that time
The design of the cockpit escape system XB-70 is also very unique, because its flight environment will be flying at an altitude of tens of thousands of meters at Mach 3, so it is impossible to directly eject the cabin like ordinary fighters, but uses a seat with a special encirclement function, and the seat will wrap the driver up and catapult out when ejecting to meet the requirements of ejection at an altitude of 20,000 meters under the condition of Mach 3, and this design has indeed saved the life of a pilot. But because of its low reliability, it also cost another driver his life.
An ejection seat that wraps the driver tightly
<h1 class="pgc-h-center-line" > the failure encountered in the prototype flight</h1>
On September 21, 1964, the first prototype of the XB-70A began its first flight, and through the test flight, it was found that there was a problem with the material strength of the fuselage, the leading edge of the wing was torn due to the insufficient strength of the honeycomb material, in addition to the failure of the landing gear and the oil leakage of the hydraulic system and even the bad problem of fuel leakage; on May 7, 1965, the XB-70A had a direct rupture of the divider plate in the front part of the intake tract during the supersonic flight, and the ruptured fragments destroyed all 6 engines and could not be repaired. Testing continued after the engine was replaced, and on October 14 of the same year, the XB-70A had a structural strength problem with the honeycomb after reaching Mach 3, the left wing was damaged, and the Air Force no longer had the XB-70A's speed exceed mach 2.5 for frequent body damage, which also affected the actual performance test of the XB-70A.
The engine of the XB-70A Prototype I was completely damaged during testing
Prototype Two solved most of the problems with Prototype 1, and the proof for this was that on 19 May 1966 Prototype 2 flew at a speed of Mach 3 for 32 minutes. The maximum speed reached Mach 3.06, and at the same time flew a predetermined distance of 3900 kilometers in 91 minutes, and this safe flight proved that the XB-70 met the requirements of the original plan, but the weather was unpredictable, and all flight tests were normal XB-70A died again.
On June 8, 1966, after the XB-70A II completed NASA's flight data mapping mission, at the request of Geelectric, four fighters, T38, F4, F-104N and F5, flew to the side of the XB-70A to prepare a set of engine propaganda photos for GE; according to the needs of the shooting, five aircraft formed a dense formation flight. However, due to too close proximity, the F-104N, which was on the right side of the XB-70A, was sucked into the vortex created by the folded wing tip of the right wing of the XB-70A, and the fighter immediately turned into a ball of fire after hitting the fuselage, and the pilot was killed on the spot. The XB-70A did not feel abnormal at first, and continued to fly forward, but due to the damage to the two vertical tails and the left and right wing tips, the XB-70A began to slowly fall and eventually lost control into the stall spiral, and was successfully piloting the parachute, and the co-pilot fell with the XB-70A due to the unreliable seat and was not catapulted.
The whole process of XB-70A II being hit by the F104N and crashing
It was also because of this accident that the government executives, who already had various opinions about the XB-70, finally let it go, and the original plan to produce three prototypes eventually stopped on the crashed Second aircraft, after which the vacant task of the Second Aircraft was completed by the strengthened First Aircraft, but because the limitation of the First Aircraft mach 2.5 was not resolved, the Air Force eventually gave up and handed it over to NASA's Flight Research Center for use.
<h1 class = "pgc-h-center-line" > the last remainder of his life in the museum</h1>
The reason why XB-70 finally fell was not only due to its own reasons, but also part of the situation, it can be said that XB-70 was born of the situation and lost in the times, when the project XB-70 was first established, it was considered that the Soviet Union did not have a fighter and anti-aircraft missiles to catch up with it, and high-altitude high-speed penetration was her biggest feature. However, the Soviet MiG-25, which was established in the XB-70 project, also stepped up the project and successfully made its first flight in 1964, the fighter successfully achieved 1+1>2 despite the material and design, and later the Soviet SAM missile technology began to advance by leaps and bounds and was fully able to catch up with the XB-70, plus the XB-70 could not perform any effective maneuvering at high speeds. With its large radius of rotation and the huge radar reflection section, it was entirely possible for sam missiles to calculate the flight trajectory and lock, so the starting point that drove her development eventually became the last unshakable boulder that stopped her forward; the government was ready to change it from a bomber to a reconnaissance aircraft, but the brewing of the A-12 and the fall of the U-2 became the last pusher of its fall into the abyss.
The only prototype of the XB-70 can only be left alone in the museum
Therefore, combining these factors, the US government completely abolished the XB-70 and instead focused on intercontinental nuclear missiles, while the XB-70, which once carried the heavy responsibility of bombing the Soviet union, was left alone with the only prototype of the A type, which remained alone in the world and spent the rest of its life in the museum.