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OOS (Odnostupenchati Orbitalni Samoliot]

In astronautics, a concept that is recurrent but almost never put into practice is air launch systems. Since Nazi Germany, vehicles have been projected that take off horizontally and reach space. Most air-launched systems have two components: the launcher and the spacecraft itself. The launcher is, as one might guess, an aircraft whose function is to take the spacecraft to the top and give it a modest initial acceleration, and above all, remove the huge fuel penalty that taking off from the ground means, allowing it to increase its payload. (which is still modest, if anything).

The Soviets designed many of these systems, but the one that dwarfed all the others was Tupolev and Antonov's in the late 1980s. Called OOS (Odnostupenchati Orbitalni Samoliot, 'single-stage orbital plane'), it consisted of an orbiter with a mass of 675 tons, although most of it would consist of fuel (a problem common to all space launch systems). Outwardly, it did not differ much from the Shuttle or Buran.

The OOS would use three 200-ton thrust cryogenic (liquid hydrogen and oxygen) engines to reach orbit, although the use of scramjet engines was also considered . Once in orbit, the OOS would use these same engines with kerosene and liquid oxygen -just like the Burán- to carry out orbital maneuvers. The use of engines with three types of propellants would save considerable mass. In addition, 38 small reactors would serve to control the attitude of the ship. Due to the large size of fuel tanks associated with any SSTO ( Single Stage To Orbit ) vehicle, the OOS could only carry a crew of two and a payload of 10 tons.

The shape of the orbiter was very similar to that of the Burán or the shuttleNorth American, although with a wider central fuselage. The thermal shield would also be very similar to that of the Burán, based on ceramic and carbon-carbon tiles. Although the mass at launch of the OOS would reach 675 tons, most of it would be fuel. For this reason, the mass of the vehicle on its return from space would be just over 100 tons, just like the Burán, which would allow a landing speed of just 240 km/h.

The An-225's original mission was to carry the space shuttle Buran and its Energia superrocket from production plants in Russia and Ukraine to the Baikonur Cosmodrome in Kazakhstan. Due to its enormous size, the An-225 will be the only way to return the orbiter to Baikonur intact. But the plane showed up too late. The Buran orbiter made its first and final flight a month before Mriya's liftoff, and an increasingly cash-strapped Soviet military lost interest in the expensive Buran project.

In any case, the world's largest aircraft arrived at the Baikonur Cosmodrome on May 13, 1989, and carried out a test flight with the space shuttle Buran. It then transported the Soviet space shuttle to the Paris Air Show in Le Bourget, where the astonished audience couldn't imagine that the impressive appearance was actually the swan song of the Bran space shuttle and the beginning of Mriya's retirement.

With the collapse of the Soviet Union in 1991 and the post-Soviet aerospace industry struggling to survive, various bizarre (and odd) uses for the An-225 were proposed. One of the ideas is to transform Mriya into a three-story airliner with private bedrooms, a shopping mall and a casino.

Other space programs in Russia, Ukraine and the UK saw Mriya and its planned successor, the An-325, as a flying launchpad for a new generation of space shuttles. One idea envisioned a monstrous twin-fuselage, 18-engine variant of the An-225, but the idea never left the drawings. The “OOS” stood for Odnostupenchati Orbitalni Samolyot, ‘one-stage orbital plane’ - a single-stage-to-orbit craft the size of the Orbiter. The OOS was to have been air-launched, and the other half of the system was the Antonov AKS.

The An-225, which was used to piggy-back the Buran shuttle around the Soviet Union, was by most measures the largest aircraft ever built. The AKS is two of them, one wing apiece removed and replaced with a sort of aerodynamic bridge, and then 675 tonnes of spacecraft and rocket propellants attached to its underside. It had twelve turbojet engines for when it flew without the orbiter attached (the dark circles in the diagram above, at lower right), with a supplementary ten more being added during launch operations (the white circles). With a length of 83 meters (272 feet), a wheelbase of 40m (131 feet) and a wingspan of 153m (502 feet), the combination came in at a whopping 1650 tonnes. By contrast, a fully fueled late-model 747 has a maximum takeoff weight of just under 440 tonnes.

It would have been an immensely expensive and difficult project right at a time when the Soviet Union was in no position to take one up, and technological limitations would have prevented anything like it at an earlier point in that country’s history. The OOS/AKS was a paper project, and would remain so.

The world's largest conjoined aircraft, the "Stratolaunch Systems" (Stratolaunch Systems) can carry a 275-ton rocket. This bizarre plane bundles two retired Boeing 747s together, with a wingspan of 117 meters. It is equipped with six Boeing 747 PW4000 engines. When the plane rises to an altitude of 35,000 feet, the rocket will separate and ignite. This money-burning project was invested by Microsoft founder Paul Allen. The Stratolanch system is a direct competitor to the Russian MAKS system, which was created but never built, based on the Mriya giant aircraft.

The OOS was conceived as an advanced space transportation system capable of replacing the Buran around the year 2000. In this sense, it was one of the many projects that appeared in the USSR during the 70s and 80s with the aim of developing a vehicle reusable spacecraft, such as the LKS or OK-M shuttles. Projects from another era, when the future of humanity seemed to go through space and when reusable ships were emerging as the only possible alternative. In other words, just the opposite of today.