TheAyaks (Russian:АЯКС, meaning alsoAjax) is ahypersonicwaverider aircraft program started in theSoviet Union and currently under development by the Hypersonic Systems Research Institute (HSRI) ofLeninets Holding Company inSaint Petersburg,Russia.[1][2][3]
Ayaks was initially a classified Sovietspaceplane project aimed to design a new kind of global range hypersonic cruise vehicle capable of flying and conducting a variety of military missions in themesosphere. The original concept revolved around a hypersonicreconnaissance aircraft project, but later was expanded into the wider concept of hypersonic multi-purpose military and civilian jets, as well as aSSTO platform for launching satellites.
The mesosphere is the layer of the Earth'satmosphere from 50 kilometres (160,000 ft) to 85 kilometres (279,000 ft) high, above thestratosphere and below thethermosphere. It is very difficult to fly in the mesosphere — the air is toorarefied for aircraft wings to generatelift, but sufficiently dense to causeaerodynamic drag on satellites. In addition, parts of the mesosphere fall inside theionosphere, 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.
In the late 1970s, Sovietscientists 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 inLeningrad.[4] He developed the Ayaks concept around the idea that an efficient hypersonic vehicle cannot afford to lose energy to its surroundings (i.e. to overcomeair 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 theWest, although early developments involved the cooperation of Soviet industrial enterprises, technical institutes, theMilitary-Industrial Commission of the USSR (VPK) and theRussian 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.[5][6]
Shortly after thedissolution of the Soviet Union, funding was cut and the Ayaks program had to evolve, especially as theUS government announced theNational Aero-Space Plane (NASP) program. At that time, Fraĭshtadt became director of theOKB-794 Design Bureau, publicly known asLeninets, aholding company running theopen joint-stock companyState Hypersonic Systems Research Institute (HSRI) (Russian:НИПГС pr: "NIPGS") in Saint Petersburg.
In early 1993, as an answer to the American announcement of theX-30 NASP demonstrator, the Ayaks project integrates into the wider nationalORYOL (Russian:Орёл pr: "Or'yol",Eagle) program, federating all Russian hypersonic works to design a competing spaceplane as areusable 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 theRussian Federation was ready to fund the Ayaks program for eight years and that a reusable small-scale flight test module had been built by theArsenal Design Bureau. He also stated that Ayaks' working principles had been validated with anengine test stand in awind tunnel. The same year, the American NASP project was cancelled and replaced by theHypersonic Systems Technology Program (HySTP), cancelled as well after three months. In 1995NASA launched theAdvanced Reusable Transportation Technologies (ARTT) program, part of theHighly Reusable Space Transportation (HRST) 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 toLeninetz HLDG Co. and consequently available publicly, the oldest having been filed 14 years before.[7][8][9][10]
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 theSapienza University of Rome; Paul A. Czysz, professor at theParks College of Engineering, Aviation and Technology atSaint Louis University; and S. N. B. Murthy, professor atPurdue 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 theODYSSEUS project.[11] Thereafter the three researchers copublished a conference paper summarizing the Western analysis of Ayaks principles.[12]
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 ofFlight Unlimited; Leon E. McKinney, world expert influid dynamics; Paul A. Czysz;Mark J. Lewis, aerodynamicist at theUniversity of Maryland, College Park, specialist ofwaveriders and airflows aroundleading edges and director of the NASA-sponsoredMaryland Center for Hypersonic Education and Research; Dr. Robert Boyd ofLockheed MartinSkunk Works able to build real working prototypes with allocated budgets fromblack projects, whose contractorGeneral Atomics is a world leader insuperconducting magnets (that Ayaks uses); and Dr. Daniel Swallow fromTextron Systems, one of the few firms still possessing expertise inmagnetohydrodynamic converters, which Ayaks extensively uses.[13][14]
The Ayaks was projected to employ a novel engine using amagnetohydrodynamic generator to collect and slow down highly ionized and rarefied air upstream ofairbreathing jet engines, usuallyscramjets, 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 conventionalturbomachinery.[15][16] This would be a surprising technical solution considering such hypersonic speeds, yet confirmed as feasible by independent studies using Mach 2.7 turbojets[17][18][19] or even subsonicramjets.[20]
The air is mixed with fuel into themixture that burns in thecombustor, while theelectricity produced by the inlet MHD generator feeds theMHD accelerator located behind the jet engine near thesingle expansion ramp nozzle to provide additionalthrust andspecific impulse. Theplasma funnel developed over the air inlet from theLorentz 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 theMach regime and altitude the aircraft can cruise to. Thus, it is theorized that the Ayaks' engine can operate using atmosphericoxygen even at heights above 35 kilometres (115,000 ft).[21]
A non-equilibrium MHD generator typically produces 1–5MWe with such parameters (channel cross-section, magnetic field strength, pressure, degree of ionization and velocity of the working fluid) 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.[12][22] As Ayaks may use two to four of such engines, some electrical energy could be diverted to peaceful or militarydirected-energy devices.[2]
The fuel feed system of the Ayaks engine is also novel. Atsupersonic speeds, air brutally recompress downstream thestagnation point of a shock wave, producing heat. Athypersonic speeds, theheat flux fromshock waves andair friction on the body of an aircraft, especially at the nose and leading edges, becomes considerable, as thetemperature isproportional to thesquare of theMach number. That is why hypersonic speeds are problematic with respect to thestrength of materials and are often referred to as theheat barrier.[23]
Ayaks uses thermochemical reactors (TCRs): the heating energy fromair friction is used to increase the heat capacity of the fuel, bycracking the fuel with acatalyticchemical reaction. The aircraft has double shielding between whichwater and ordinary, cheapkerosene circulates in hot parts of the airframe. The energy of surface heating is absorbed throughheat exchangers to trigger a series of chemical reactions in presence of anickel catalyzer, calledhydrocarbonsteam reforming. Kerosene and water spits into a new fuel reformate:methane (70–80% in volume) andcarbon dioxide (20–30%) in a first stage:
Then methane and water reform in their turn in a second stage intohydrogen, a new fuel of better quality, in a strongendothermic reaction:
Thus, the heating capacity of the fuel increases, and the surface of the aircraft cools down.[24]
Thecalorific value of the mixture CO + 3H2 produced from 1 kg of methane through water steam reforming (62,900 kJ) is 25% higher than that of methane only (50,100 kJ).[16]
Besides a more energetic fuel, the mixture is populated by manyfree radicals that enhance thedegree of ionization of the plasma, further increased by the combined use ofe-beams that control electron concentration, andHFpulse repetitive discharges (PRDs) that control electron temperature. Such systems createstreamer discharges that irrigate the ionized flow with free electrons, increasing combustion effectiveness, a process known asplasma-assisted combustion (PAC).[25][26][27][28]
Such concept was initially namedMagneto-Plasma-Chemical Engine (MPCE),[29][30][31] and the working principle referred to asChemical Heat Regeneration and Fuel Transformation (CHRFT).[32] 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 ascramjet with MHD bypass as these concepts intimately require each other to work efficiently.[33]
The idea of thermally shielding the engine is detailed in the fundamental analysis of an ideal turbojet for maximum thrust analysis in theaerothermodynamics literature.[34] That is, putting the turbine (work extraction) upstream and the compressor (work addition) 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 (andunstarting the engine) 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."[16]
As altitude increases, the electrical resistance of air decreases according toPaschen's law. The air at the nose of Ayaks is ionized. Besides e-beams and HF pulse discharges, ahigh voltage is produced by theHall effect in the MHD generator that allows a planarglow discharge to be emitted from the sharpnose of the aircraft and the thinleading edges of its wings, by aSt. Elmo's fire effect. Such a plasma cushion in front and around the aircraft is said to offer several advantages:[2][35][36]
According to the data presented at the 2001MAKS Airshow, the specifications of the Ayaks are:
| Parameter | Hypersonic Satellite Launcher | Multi-purpose Hypersonic Craft | Transport Hypersonic Craft |
|---|---|---|---|
| Maximum takeoff weight,tonne | 267 | 200 | 390 |
| Loaded Weight, tonne | 113 | 85 | 130 |
| Empty weight, tonne | 76 | ||
| Mass of the second stage, tonne | 36 | ||
| Payload, tonne | 10 | 10 | |
| Satellite mass, tonne | 6 | ||
| Turbojet engines | 4 | 4 | 4 |
| Magneto-plasma-chemical engines | 4 | 6 | 4 |
| Thrust, turbojet engines, tonne | 4×25 | 4×25 | 4×40 |
| Thrust, magneto-plasma-chemical engines | 4×25 | 6×14 | 4×40 |
| Maximal speed, m/s | 4000 | 4000 | 4600 |
| Service ceiling, km | 36 | 36 | 36 |
| Practical range at M = 8 ... 10 and height of 30 km, km | 14200 | 10000 | 12000 |
Later publications cite even more impressive numbers, with expected performance of service ceiling of 60 km and cruising speed of Mach 10–20, and the ability to reach theorbital speed of 28,440 km/h with the addition ofbooster rockets, the spaceplane then flying inboost-glide trajectories (successive rebounds or "skips" on the upper layers of the atmosphere, alternating unpowered gliding and powered modes) similarly to the US hypersonic waverider projectHyperSoar with a highglide ratio of 40:1.[15][39][40]
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In 2003, French engineer Jean-Pierre Petit's study was based on a paper published in January 2001 in the French magazineAir et Cosmos by Alexandre-David Szamès,[15] and in the same month from information gathered in a small workshop on advanced propulsion inBrighton, England,[41] especially after discussions with David Froning Jr. fromFlight Unlimited about his prior work involving electric and electromagnetic discharges in hypersonic flows, presented during the workshop.[35]
Petit wrote about a large and long multipole wallMHD converter on the upper flat surface of the aircraft in contact with thefreestream, instead of the linear cross-field Faraday converters located within a channel usually considered. In such a multipole converter, magnetic field is produced by many parallel superconducting thin wires instead of pairs of bigger electromagnets. These wires run below the surface directly in contact with the airflow, their profile following the body of the vehicle. Air is progressively decelerated in theboundary layer in alaminar flow without too much recompression, down to subsonic values as it enters the inlet then the air-breathing jet engines. Such an open wall MHD-controlled inlet will be exposed by two scientists of the Ayaks program in a similar way two years later, although they propose to locate it on the surface of the inclined front ramp underneath the aircraft, to vector the shock wave as a "shock-on-lip" upon the air inlet, whatever the speed and altitude.[42]
As subsonic velocities can be achieved internally while the external flow is still hypersonic, Petit proposes that such platform could use almost conventional turbojets and ramjets instead of scramjets more difficult to control, and such plane would not needvertical stabilizers norfins anymore, as it would maneuver through locally increasing or reducing drag on particular regions of the wetted area with electromagnetic forces. He then describes a similar multipole MHD accelerator located on the physical surface of thesemi-guided ramp nozzle, which accelerates the conductive exhaust gases downstream the jet engines.
Ten years before Petit, Dr. Vladimir I. Krementsov, head of theNizhny Novgorod Research Institute of Radio Engineering (NIIRT), and Dr Anatoly Klimov, chief of theMoscow Radiotechnical Institute of the Russian Academy of Sciences (MRTI RAS), exposed toWilliam Kaufmann that the MHD bypass system of the Ayaks concept would have been already built in the rumoredAurora secret spaceplane, successor of theLockheed SR-71 Blackbird.[40][43][44]
The 'Magneto Plasma Chemical Engine' title was used in the paper for designation of the engine. At present the title 'Scramjet with MHD bypass' is frequently used for the engine designation.
