X-15 Rocket Plane in Space: Hypersonic 1967

Today, humanity has turned all its attention to reusable launch vehicles in terms of space exploration. But there have already been shuttles in history: both in the USA and in the USSR. At that time, great hopes were pinned on them. Hypersonics are also on everyone's lips, but this is also a stage that the Americans have long since passed.


In essence, the shuttles were by air, capable of reaching space. However, the path to their creation was long: first, it was necessary to rise to a height of "at least" 100 km. To achieve this, the US experimented with German V-2s, transported to America after the end of World War II.


The very first assembled rocket rose into the sky to a height of 112 km. Encouraged by their success, the Americans began to repeat the experiment, launching devices with plants, small rodents, and later – monkeys. The experiments continued for almost 10 years, but after a series of accidents it became clear that in order to better study the height of more than 50 km, a manned aircraft was needed. However, an ordinary machine was not capable of this: at that time, the maximum was 35 km. Therefore, NASA initiated the start of a project that implied the creation of a rocket plane capable of developing a speed of several Machs and rising above the Earth at least 100 km.

Experimental apparatus X-15

In 1955, the US Aerodynamics Committee (NACA, later re-profiled into NASA), in alliance with the military, who were also interested in creating similar technology, announced a competition. The winner among 12 participants was North American Aviation Inc.


Her project was considered more realistic, although there were others, ambitious ones. For example, Dornberger proposed to develop a flying machine that would reach 8800 km/h and rise to an altitude of 170 km. The winner of the competition was ordered to manufacture three machines. By 1958, they were ready. Investments in the project amounted to 163 million dollars.

About the design of the X-15

The aircraft was atypical, if only because it took off not from the runway, but from under the wing of its "carrier" - the B-52, which after minor modifications was assigned the index "A". Initially, they wanted to install the XLR-15-RM99 rocket engine on the X-1, which developed a thrust of 22,7 tf and ran on liquefied ammonia. In this case, oxygen played the role of an oxidizer. However, when the completed rocket plane was rolled out of the assembly shop, the power unit was not yet ready.


Therefore, they installed a pair of XLR-11, each with a capacity of 6,8 tf. These engines were installed during the first tests, not related to achieving maximum results. They also solved another problem caused by the temperature difference of the fuselage. And they will be in the range from -185 to +650 °C. At that time, only nickel could withstand such a test. The rocket plane's body was made of it, using riveting and welding.

Features of the X-15: controls and pilot clothing

In addition to the standard control wheel, there were a couple more handles with armrests in the cabin. This decision was caused by the impact of overloads, which would not allow holding the "horns" in the required position. The pilot's clothing also deserves attention: a sealed spacesuit with nitrogen circulating inside. It provided a comfortable pressure for a person, which drops at altitude. It was even decided to secure the pilot's head to protect it from overloads.


Overall dimensions and weight characteristics of the X-15:

✅ wingspan, length, height - 6,7, 15,2 and 4,1 m
✅ empty and fully loaded weight – 6 and 15 t

The machine was controlled by one pilot. A total of 1969 test pilots participated in the experiment, which lasted until 12.

Full-fledged flights

The training was conducted on F-104 aircraft, which were very similar in design to the X-15. Especially in terms of landing. The first launch, which took place in March 1959, was unsuccessful - due to electronic malfunctions, the experiment was stopped. The second flight, which involved free gliding after detaching from the B-52A, went as planned.


The machine, having reached a speed of 840 km/h, landed on the ground. In the autumn of this year, the X-15 flew with the jet engines on. In total, 77 flights were made during the first stage of testing, during which the first goal was achieved – a speed of 6548 km/h.

Height

The first attempts were also unsuccessful: the windshield could not withstand the pressure and cracked. The design of the rocket plane had to be improved. It is worth noting that the plane was equipped with numerous sensors operating in the infrared and ultraviolet ranges both inside and outside. The pilot's body was also covered with devices to understand how altitude and speed would affect him. The data obtained was later used to create launch vehicles.


Finally, the long-awaited flight was completed: in December 1961, the X-15 rocket plane rose to an altitude of 108 km. In 1967, another model of the machine, designated X-15A-2, managed to accelerate to a speed of 6,72 Mach (7274 km/h). This is an absolute record for aircraft, which has not been broken to this day. However, the International Aviation Federation FAI did not count it, since the machine did not take off independently from the runway, but was dropped from a B-52A.

Problems

They constantly accompanied test flights. In addition to electronic failures and cracked glass, there were also malfunctions in the engine and steering. For example, in 1967, pilot W. Knight managed to land the aircraft only thanks to his skill – all the onboard equipment failed. That same year, the same pilot barely managed to return in a rocket plane that began to overheat.


The test pilot said: "You physically feel how the machine is shaking, the skin starts to warp, and you have no idea what is happening." In 1962, the landing gear broke, the plane flipped over, caught fire - the pilot miraculously survived.

Pilots or astronauts?

An interesting question: the American military believes that space begins at an altitude of 80,5 km. If so, then the X-15 has been there 13 times. However, NASA is confident that the boundary is at a distance of 122 km from the Earth's surface. This means that the X-15 pilots did not violate the limits of the atmosphere. But there is a third party - the above-mentioned FAI, according to which space begins at an altitude of 100 km. Then it turns out that only J. Walker has visited the "universe", having risen to 106 and 108 (107906 m) km.


It is possible that this "rat race" over the definition of "space" is connected with the race between the USSR and the USA. The latter tried to catch up with the former in the number of people who had been beyond the Earth. And so 12 test pilots were given the title of "astronauts".


However, the world community did not agree with this. At that time, it was still possible to contradict the USA!

Completion of the X-15 project

The main "catalyst" for the program's closure was an incident in November 1967. After the flight began, the electronics failed: the instruments showed the normal condition of the rocket plane, while it was already faulty.


As a result, the machine crashed, the pilot M. Adams died. The media spoke out sharply against the project: the result was a refusal to finance - the program was finally closed down a couple of years later.

Was the X-15 needed?

Despite accidents and disasters, the rocket plane managed to collect a lot of information about the state and properties of the upper atmosphere. Important additions to knowledge of aero- and thermodynamics were obtained. The developments were in demand during the design and construction of the Shuttle. In the 1990s, the experience gained during the operation of the X-15 was used to create the Pegasus launch vehicle, which is also launched from an aircraft.