Ayaks
The Ayaks is a hypersonic waverider aircraft program started in the Soviet Union and currently under development by the Hypersonic Systems Research Institute 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, 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 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 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 Research Institute in Saint Petersburg.
In early 1993, as an answer to the American announcement of the X-30 NASP demonstrator, the Ayaks project integrates into the wider national ORYOL program, federating all Russian hypersonic works to design a competing spaceplane as a reusable launch system.
In September 1993 the program was unveiled and a first small-scale model of Ayaks was publicly shown for the first time on the Leninetz booth at the 2nd MAKS Air Show in Moscow.
In 1994 Novichkov revealed that the Russian Federation was ready to fund the Ayaks program for eight years and that a reusable small-scale flight test module had been built by the Arsenal Design Bureau. He also stated that Ayaks' working principles had been validated with an engine test stand in a wind tunnel. The same year, the American NASP project was cancelled and replaced by the Hypersonic Systems Technology Program, cancelled as well after three months. In 1995 NASA launched the Advanced Reusable Transportation Technologies program, part of the Highly Reusable Space Transportation initiative, but experts from consulting firm ANSER evaluating Ayaks technologies did not believe at first in the performances announced by the Russians and did not recommend development along the same path.
However, between October 1995 and April 1997, a series of Russian patents covering Ayaks technologies were granted to Leninetz HLDG Co. and consequently available publicly, the oldest having been filed 14 years before.
As the information available out of Russia started to grow, three western academic researchers started to collect the sparse data about Ayaks: Claudio Bruno, professor at the Sapienza University of Rome; Paul A. Czysz, professor at the Parks College of Engineering, Aviation and Technology at Saint Louis University; and S. N. B. Murthy, professor at Purdue University. In September 1996, as part of the Capstone Design Course and the Hypersonic Aero-Propulsion Integration Course at Parks College, Czysz assigned his students to analyze the information gathered, as the ODYSSEUS project. Thereafter the three researchers copublished a conference paper summarizing the Western analysis of Ayaks principles.
With such information, long-time ANSER main expert Ramon L. Chase reviewed his former position and assembled a team to evaluate and develop American versions of Ayaks technologies within the HRST program. He recruited H. David Froning Jr., CEO of Flight Unlimited; Leon E. McKinney, world expert in fluid dynamics; Paul A. Czysz; Mark J. Lewis, aerodynamicist at the University of Maryland, College Park, specialist of waveriders and airflows around leading edges and director of the NASA-sponsored Maryland Center for Hypersonic Education and Research; Dr. Robert Boyd of Lockheed Martin Skunk Works able to build real working prototypes with allocated budgets from black projects, whose contractor General Atomics is a world leader in superconducting magnets ; and Dr. Daniel Swallow from Textron Systems, one of the few firms still possessing expertise in magnetohydrodynamic converters, which Ayaks extensively uses.
Novel technologies
MHD bypass
The Ayaks was projected to employ a novel engine using a magnetohydrodynamic generator to collect and slow down highly ionized and rarefied air upstream of airbreathing jet engines, usually scramjets, although HSRI project lead Vladimir L. Fraĭshtadt said in a 2001 interview that the Ayaks MHD bypass system could decelerate the incoming hypersonic airflow sufficiently to almost use conventional turbomachinery. This would be a surprising technical solution considering such hypersonic speeds, yet confirmed as feasible by independent studies using Mach 2.7 turbojets or even subsonic ramjets.The air is mixed with fuel into the mixture that burns in the combustor, while the electricity produced by the inlet MHD generator feeds the MHD accelerator located behind the jet engine near the single expansion ramp nozzle to provide additional thrust and specific impulse. The plasma funnel developed over the air inlet from the Lorentz forces greatly increases the ability of the engine to collect air, increasing the effective diameter of the air inlet up to hundreds of meters. It also extends the Mach regime and altitude the aircraft can cruise to. Thus, it is theorized that the Ayaks' engine can operate using atmospheric oxygen even at heights above.
A non-equilibrium MHD generator typically produces 1–5 MWe with such parameters but the increased effective diameter of the air inlet by the virtual plasma funnel greatly increases the power produced to 45–100 MWe per engine. As Ayaks may use two to four of such engines, some electrical energy could be diverted to peaceful or military directed-energy devices.
Thermochemical reactors
The fuel feed system of the Ayaks engine is also novel. At supersonic speeds, air brutally recompress downstream the stagnation point of a shock wave, producing heat. At hypersonic speeds, the heat flux from shock waves and air friction on the body of an aircraft, especially at the nose and leading edges, becomes considerable, as the temperature is proportional to the square of the Mach number. That is why hypersonic speeds are problematic with respect to the strength of materials and are often referred to as the heat barrier.Ayaks uses thermochemical reactors : the heating energy from air friction is used to increase the heat capacity of the fuel, by cracking the fuel with a catalytic chemical reaction. The aircraft has double shielding between which water and ordinary, cheap kerosene circulates in hot parts of the airframe. The energy of surface heating is absorbed through heat exchangers to trigger a series of chemical reactions in presence of a nickel catalyzer, called hydrocarbon steam reforming. Kerosene and water spits into a new fuel reformate: methane and carbon dioxide in a first stage:
Then methane and water reform in their turn in a second stage into hydrogen, a new fuel of better quality, in a strong endothermic reaction:
Thus, the heating capacity of the fuel increases, and the surface of the aircraft cools down.
The calorific value of the mixture CO + 3H2 produced from 1 kg of methane through water steam reforming is 25% higher than that of methane only.
Besides a more energetic fuel, the mixture is populated by many free radicals that enhance the degree of ionization of the plasma, further increased by the combined use of e-beams that control electron concentration, and HF pulse repetitive discharges that control electron temperature. Such systems create streamer discharges that irrigate the ionized flow with free electrons, increasing combustion effectiveness, a process known as plasma-assisted combustion.
Such concept was initially named Magneto-Plasma-Chemical Engine, and the working principle referred to as Chemical Heat Regeneration and Fuel Transformation. In subsequent literature, the accent has been put more on magnetohydrodynamics than on the chemical part of these engines, which are now simply referred to as a scramjet with MHD bypass as these concepts intimately require each other to work efficiently.
The idea of thermally shielding the engine is detailed in the fundamental analysis of an ideal turbojet for maximum thrust analysis in the aerothermodynamics literature. That is, putting the turbine upstream and the compressor downstream. For a conventional jet engine, the thermodynamics works, however the advanced thermo-fluids analysis shows that in order to add sufficient heat to power the aircraft without thermally choking the flow the combustor has to grow and the amount of heat added grows as well. It is more "efficient" in using the heat, it just needs a lot of heat. While thermodynamically very sound, the real engine is too large and consumes too much power to ever fly on an aircraft. These issues do not arise in the Ayaks concept as the plasma funnel virtually increases the cross-section of the air inlet while maintaining its limited physical size, and additional energy is taken from the flow itself. As Fraĭshtadt said, "Since it takes advantage of the CHRFT technology, Ayaks cannot be analyzed as a classical heat engine."