In the middle of the last century, manned jet aircraft, gradually mastering new speeds and heights, were able to come close to the threshold of space.
American challenge
The first successes were achieved by the Americans: on October 14, 1947, test pilot Chuck Yeager on an experimental X-1 rocket plane dropped from the B-29 "flying fortress" already on December 12, 1953, on an improved X-1A rocket plane, he reached a maximum speed of 2655 km / h (M = 2, 5) at an altitude of over 21 km. In 1953, tests of the X-2 rocket plane began, on which a record speed in horizontal flight of 3360 km / h was reached on July 25, 1956, and at the beginning of September 1956 - an altitude of 38 430 m.
In June 1954, the United States began a test program for the Kh-15 hypersonic winged rocket plane, which, starting from under the wing of a converted B-52 strategic bomber, had to develop a speed six times the speed of sound in a few minutes and reach an altitude of 76 km! The first prototype was flown under the wing of the aircraft on May 10, 1959, and on June 8, the X-15 for the first time separated from the B-52 and made an independent gliding flight. The first activation of the rocket engine was carried out on September 17, and in further test flights the records "poured down" one after another - on August 4, 1960, a speed of 3514 km / h was reached, and on August 12 - an altitude of 41,605 m; On March 7, 1961, the Kh-15 reached a speed of 4264 km / h, in flight on March 31, an altitude of 50,300 meters was taken; On April 21, a speed of 5033 km / h was reached, on September 12 - already 5832 km / h. The one-kilometer line, which is considered the "official" boundary of space, was crossed on August 22, 1963 - the maximum flight altitude was 107,906 m!
Space skier
Inspired by the success of the X-15, the US Air Force began development of a military space rocket plane as part of the Dyna Soar project (from Dynamic Soaring). The rocket plane, called the X-20, was supposed to fly at a speed of 24,000 km / h and was, in fact, a development of the idea of the German space bomber Zenger (see "PM" # 8'2004). This is not surprising, given that key engineering positions in the American space program were held by German specialists. The new rocket plane was planned to be armed with space-to-space, space-to-air and space-to-ground missiles and conventional bombs. The lower surface of the X-20 was covered with a metal heat shield made of molybdenum, which can withstand temperatures up to 1480 ° C, the leading edges of the wing were made of a molybdenum alloy, which could withstand temperatures up to 1650 ° C. Individual parts of the vehicle, which, upon entering the atmosphere, heated up to 2371 ° C, were protected by a reinforced graphite and a zirconium hemispherical cap in the nose of the fuselage or were lined with a ceramic insulating niobium coating. The pilot was placed in an ejection seat, providing rescue only at subsonic speeds. The cockpit was equipped with side windows and a windshield, protected by heat shields, which were dropped just before landing. A payload weighing up to 454 kg was placed in the behind-the-cock compartment. The landing gear consisted of three retractable struts equipped with skis.
But unlike its German predecessor, the X-20 was not a space plane in the truest sense of the word. It was supposed to start from Cape Canaveral in the traditional way on top of the Titan-IIIC launch vehicle, which launched the rocket plane into an orbit with an altitude of 97.6 km. Further, the X-20 had to either accelerate itself, using its own rocket engines, or, having completed an incomplete orbit, plan to Edwards AFB. It was planned that the first drop from the B-52 aircraft would be made already in 1963, the first unmanned flight would take place in November 1964, and the first manned flight in May 1965. However, this military program quietly died earlier, unable to compete with the simple and cheap solution - sending astronauts into space on a ballistic rocket in a pressurized capsule, implemented by a civilian organization NASA.
Belated response
Ironically, at the very moment when the Americans were closing their program of manned rocket gliders, the USSR, impressed by the X-15 records, decided to "catch up and overtake" America. In 1965, OKB-155 Artem Mikoyan was instructed to lead the work on orbital and hypersonic aircraft, more precisely, on the creation of a two-stage aerospace system "Spiral". The topic was supervised by Gleb Lozino-Lozinsky.
The 115-ton "Spiral" consisted of a 52-ton hypersonic accelerator aircraft, indexed "50-50", and an 8, 8-ton manned orbital aircraft (index "50") located on it with a 54-ton two-stage rocket booster. The booster reached a hypersonic speed of 1800 m / s (M = 6), and then, after separating the steps at an altitude of 28-30 km, returned to the airfield. The orbital plane, using a rocket booster operating on hydrogen fluoride (F2 + H2) fuel, entered the working orbit.
Booster plane
The booster crew was housed in a two-seater pressurized cockpit with ejection seats. The living aircraft, together with the rocket booster, was attached from above in a special box, with the nose and tail parts being covered with fairings.
The accelerator used liquefied hydrogen as fuel, which was fed into a block of four AL-51 turbojet engines developed by Arkhip Lyulka, which had a common air intake and operated on a single supersonic external expansion nozzle. A feature of the engines was the use of hydrogen vapor to drive the turbine. The second fundamental innovation is the integrated, adjustable hypersonic air intake, which used almost the entire front part of the lower wing surface to compress the air entering the turbines. The estimated flight range of the accelerator with a load was 750 km, and when flying as a reconnaissance aircraft - more than 7000 km.
Orbital plane
Combat reusable manned single-seat orbital aircraft with a length of 8 m and a wingspan of 7, 4 m was carried out according to the "carrying body" scheme. Due to the selected aerodynamic layout, from the total span, the swept wing consoles had only 3.4 m, and the rest of the bearing surface was related to the width of the fuselage. The wing consoles during the passage of the plasma formation section (launching into orbit and the initial phase of descent) were deflected upward to exclude a direct heat flow around them. In the atmospheric section of the descent, the orbital plane unfolded its wings and switched to horizontal flight.
Orbital maneuvering engines and two emergency liquid-propellant rocket engines ran on high-boiling AT-NDMG fuel (nitrogen tetraxide and asymmetric dimethylhydrazine), similar to that used on combat ballistic missiles, which was later planned to be replaced with more environmentally friendly fluorine-based fuel. The fuel reserves were sufficient for a flight lasting up to two days, but the main task of the orbital aircraft had to be performed during the first 2-3 orbits. The combat load was 500 kg for the reconnaissance and interceptor variant and 2 tons for the space bomber. Photographic equipment or missiles were located in a compartment behind a detachable cockpit-capsule of the pilot, which provided the rescue of the pilot at any stage of the flight. The landing was made using a turbojet engine on a dirt airfield at a speed of 250 km / h on a four-post ski chassis.
To protect the apparatus from heating during braking in the atmosphere, a heat-shielding metal screen was provided from plates of heat-resistant steel VNS and niobium alloys arranged according to the principle of "fish scales". The screen was suspended on ceramic bearings that played the role of thermal barriers, and when the heating temperature fluctuated, it automatically changed its shape, maintaining a stable position relative to the body. Thus, in all modes, the designers hoped to ensure the constancy of the aerodynamic configuration.
A disposable two-stage launch unit was docked to the orbital plane, on the first stage of which there were four liquid-propellant rocket engines with a thrust of 25 tf, and on the second - one. For the first time, it was planned to use liquid oxygen and hydrogen as fuel, and later to switch to fluorine and hydrogen. The stages of the accelerator, as the aircraft was put into orbit, were sequentially separated and fell into the ocean.
Mythic plans
The plan of work on the project provided for the creation by 1968 of an analogue of an orbital aircraft with a flight altitude of 120 km and a speed of M = 6-8, dropped from the Tu-95 strategic bomber, a kind of response to the American record system - B-52 and X-15.
By 1969, it was planned to create an experimental manned orbital aircraft EPOS, which bears full resemblance to a combat orbital aircraft, which would be launched into orbit by a Soyuz carrier rocket. In 1970, the accelerator was also supposed to start flying - first on kerosene, and two years later on hydrogen. The complete system was supposed to be launched into space in 1973. Of this entire grandiose program, in the early 1970s, only three EPOS were built - one for researching flight at subsonic speeds, one for supersonic research, and one for reaching hypersonic. But only the first sample was destined to rise into the air in May 1976, when all similar programs in the United States had already been phased out. Having made a little more than a dozen sorties, in September 1978, after an unsuccessful landing, the EPOS received minor damage and did not rise into the air again. After that, the already scanty funding for the program was curtailed - the Ministry of Defense was already busy developing another response to the Americans - the Energia - Buran system.
Locked topic
Despite the official closure of the Spiral program, the work expended was not in vain. The groundwork created and the experience gained in working on the "Spiral" greatly facilitated and accelerated the construction of the reusable spacecraft "Buran". Using the experience gained, Gleb Lozino-Lozinsky led the creation of the Buran glider. The future cosmonaut Igor Volk, who made flights on a subsonic analogue of the EPOS, was subsequently the first to fly the atmospheric analogue of the Buran BTS-002 and became the commander of a detachment of test pilots under the Buran program.
