The Ayaks () is a hypersonic waverider aircraft program started in the Soviet Union and currently under development by the Hypersonic Systems Research Institute (HSRI) of Leninets Holding Company in Saint Petersburg, Russia. Purpose Ayaks was initially a classified Soviet spaceplane project aimed to design a new kind of global range hypersonic cruise vehicle capable of flying and conducting a variety of military missions in the mesosphere. The original concept revolved around a hypersonic reconnaissance aircraft project, but later was expanded into the wider concept of hypersonic multi-purpose military and civilian jets, as well as a SSTO platform for launching satellites. The mesosphere is the layer of the Earth's atmosphere from to high, above the stratosphere and below the thermosphere. It is very difficult to fly in the mesosphere — the air is too rarefied for aircraft wings to generate lift, but sufficiently dense to cause aerodynamic drag on satellites. In addition, parts of the mesosphere fall inside the ionosphere, meaning the air is ionized due to solar radiation. The ability to conduct military activities in the mesosphere gives a country some significant military potential. History In the late 1970s, Soviet scientists began to explore a novel type of hypersonic propulsion system concept, exposed for the first time in a Russian newspaper with a short interview of Ayaks' inventor, Pr. Vladimir L. Fraĭshtadt. Fraĭshtadt worked at that time at the aero branch of the PKB Nevskoye-Neva Design Bureau in Leningrad. He developed the Ayaks concept around the idea that an efficient hypersonic vehicle cannot afford to lose energy to its surroundings (i.e. to overcome air resistance), but should instead take advantage of the energy carried by the high speed incoming flux. At that time, the whole concept was unknown to the West, although early developments involved the cooperation of Soviet industrial enterprises, technical institutes, the Military-Industrial Commission of the USSR (VPK) and the Russian Academy of Sciences. In 1990, two articles by defense specialist and writer Nikolai Novichkov gave more details about the Ayaks program. The second was the first document available in English. Shortly after the dissolution of the Soviet Union, funding was cut and the Ayaks program had to evolve, especially as the US government announced the National Aero-Space Plane (NASP) program. At that time, Fraĭshtadt became director of the OKB-794 Design Bureau, publicly known as Leninets, a holding company running the open joint-stock company State Hypersonic Systems