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The SPIRAL Orbital Plane and the BOR-4 and BOR-5 Flying Models

General Mikoyan S.A.
The paper tells about the SPIRAL system and flight tests of its analogue. It is explained the usage of the BOR-4 model of the SPIRAL Orbiter for creation of the BURAN orbiter’s Heat Protection. Problems, course of tests of the BOR-4 and BOR-5 flying models and main results are described.

Since the middle of 1960s in the Design Bureau, headed by General Designer Mikoyan A.I., it has been developing the SPIRAL aerospace system, consisted of an orbital manned plane with a rocket booster and a hypersonic booster-plane.

The Head Designer under this project was Dr. Lozino-Lozinsky G.E. Among leaders were Mr.: Seletsky Ya.I., Dementyev G.P., Voinov L.P. and Samsonov E.A. and later, at the stage of production and tests, also Mr.: Shuster P.A. and Blokhin Y.D.

The SPIRAL orbital plane is a single-seat aircraft of a lifting body configuration with fuselage nose of big radius. The 50* sweep wings with the noses of little radius had longitudinal axis of rotation and before transition to the atmospheric flight should have been deflected up thus excluding their direct flow by heated stream when flying through plasma formation leg.

When a velocity decreased approximately down to value M = 2, the wings opened and the angle of attack decreased down to usual plane’s values. The angular attitude control of the plane in orbit should have been ensured by means of the low-thrust jet control engines (RCS) and in the atmosphere dense layers – by means of the elevons, rudder and balancing flap.

An undercarriage of the plane was retractable, four-legs with round skis – ‘plates’. The rear skis were equipped with ‘knifes’ to provide stability at landing run.

During testing and on the first phase of usage, before creation of the carrier-plane it was supposed that the orbital plane would be injected into an orbit by means of a ballistic rocket. The orbital plane should have glided on the legs of atmospheric descent and landing on the airdrome, but the turbo-jet engine should have been used to define landing approach.

The subsonic piloted prototype of the SPIRAL orbital plane (105 Vehicle) was developed to test the landing approach and landing legs as well as to determine the aerodynamic and controllability characteristics.

To test taxiing and hop flight (flight at low height) the skis front legs were exchanged for the wheel ones.

The 105 Vehicle has been slung beneath a fuselage of the TU-95 (specially modified) bomber and then it should have been uncoupled at 5500-meters altitude above the airdrome. The first flight took place on 27-th October, 1977 and in 1978 additional five flights were fulfilled. The flights were performed by the test pilots from Mikoyan design bureau Mr.: Fastovets A.G., Ostapenko P. and pilot from the Air Force scientific research institute Mr. Uryadov V.E.

The government resolution draft about creation of the SPIRAL orbiter plane has never been signed due to negative decision made by the Minister of Defense Mr. Grechko A.A. though the signatures of all interested commanders-in-chief of different armed forces as well as the Ministers of Defense industries were presented. All works were conducted in accordance with decision of the Ministry of the Aircraft Industry.

The major participants of the SPIRAL project from the Mikoyan design bureau and its department placed in Dubna city as well as some participants of this project from other organizations have passed to NPO MOLNIYA Scientific & Industrial Enterprise which was specially-organized for creation of the reusable space vehicle in 1976. NPO MOLNIYA under the direction of Dr. Lozino-Lozinsky G.E included the Bisnovat M.R design bureau, the Potopalov A.V. design bureau and the Myasischev V.M. Experimental Machine-Building (EMZ) plant.

The General Designer of NPO ENERGIA – the major system designer in spite of the intentions and preliminary developmental works of the NPO MOLNIYA, based on the SPIRAL project, has decided to use the configuration similar to the American Shuttle, excluding the main engine (ME) replaced to the rocket-launcher. By the decision of the Ministry of the Aircraft Industry all works on the SPIRAL project was stopped.

The experience resulted from the works on the SPIRAL project was used in the development of the BURAN orbiter and the ideas of the SPIRAL project have been enhanced further in new projects of the aerospace systems.

Now the SPIRAL analogue is presented in the Air Force museum in Monino, near Moscow.

The BOR-4 Flying Orbital Model

The BOR-4 flying model was designed during studies on the SPIRAL project. It was the orbiter’s prototype on 2:1 scale. It was used for experimental launches into an orbit for the interest of SPIRAL project development. The previous models (BOR-2 and BOR-3) of less dimensions were used to research the aerodynamic characteristics, heat exchange and elements of the Thermal Protection System (TPS) at altitudes up to 100 km and velocity up to M = 13.

During development of reusable space vehicle BURAN in NPO MOLNIYA the BOR-4 flying model was supposed to be used for the heat protection test. So, for the first time before BURAN Orbiter’s flight the BOR-4 model allowed to test capacity for work of the materials and the construction elements of TPS in real descent through atmosphere along the trajectory similar to the trajectory BURAN. Such decision was made because the outlines of model nose was equal to BURAN Orbiter’s nose outlines, including the ventral fuselage (Figure 1).

The BOR-4 model was equipped with the heat protection in accordance with the heat protection of the BURAN vehicle (above the panels of usual ablation TPS of the original project left for emergency). The general surface consisted of panels made on the base of a quartz fiber. On the top surface of the body a flexible TPS on the basis of nonwoven fabric of organic fiber was used. The nose cowling was made from carbon-carbonic composite material.

The BOR-4 model was equipped with remote telemetric system. The information has been received from 150 thermocouples located generally on a duralumin sheathing of model under the heat protection panels. Besides, several dozens of temperature and pressure sensors were built in as well as thermal indicator paint and melting indicators.

The information from accelerometers, rate sensors, pressure sensors and position sensors of wing panels was also transmitted into the telemetric system. The information was recorded on the board and transmitted in packets when pass through two special measuring ships and when descend also to the on-ground receiving station.

The BOR-4 model weight is approximately 1450 kg. The model was being injected into an orbit by a K-65M-RB5 ballistic rocket and fulfilled the Earth single-orbit flight at 225 km altitude. It was controlled by micro jet engines (RCS) in accordance with a program of on-board autonomous control system, which was receiving information from the inertial navigation system.

The wing panels of the BOR-4 model as well as the SPIRAL plane wing panels could deflect up. At that, the angle of deflection (the angle of dihedral) of the wing panels determined the angle of attack when the model was self-balanced during upper-air flight. When the BOR-4 model was located under the rocket nose cone, the wing panels were completely folded. After separation, they were transferred into a position which ensured the model’s balancing in the atmosphere at 60…70 km altitude and with 57* angle of attack in the first flight and 52…54* in the following flights. In vacuum the model was controlled by eight micro jet engines of angular orientation. The differential deflection from balance position was used for the roll control.

After braking, gliding at the upper-air and passing through a plasma formation zone, at approximately 30-km altitude the model was being forced by the control system into a tight spiral. This was done to decrease the flight velocity, and then (at approximately 7500-m altitude) a parachute was being developed to provide an alighting on water with 7-8 m/s vertical velocity.

The first model copy with TPS made of ablation materials was launched into sub-orbital trajectory to test the whole system. This flight was done from the Kapustin Yar test range in the Balkhash lake direction on the 5-th December, 1980.

The first orbital flight of the model (KOSMOS 1374 satellite) took place on the 4-th June, 1982. The second launch (KOSMOS 1445) was on the 16-th March, 1983. The third launch (KOSMOS 1517) – on the 27-th December, 1983 and the fourth launch (KOSMOS 1616) – on the 19-th December, 1984. The tests confirmed efficiency of TPS as well as considerable heat decrease due to the catalytic neutrality of the surface. It allowed to decrease cover thickness and as a result a total mass of the BURAN orbiter. The received real characteristics have confirmed adequacy of technique used for recalculation of results received in a wind tunnel for nature conditions.

The planned launch of the fifth BOR-4 orbital model became unnecessary.

In the first two flights the model alighted on water in the Indian Ocean approximately 900 km to the west from Australia and after searching one were being lifted aboard. During the next two flights alighting on water took place in the Black Sea to the west of Sevastopol. The ships of USSR Navy performed the searching and evacuation. One of the model alighted on water in the Black Sea was not found.

The BOR-4 orbital model was created in the Flight-Research Institute (Ministry of Aircraft Industry) under the leaders of Dr. Utkin V.V., Shogin U.N. and Fedorovich F.F. on the basis of the existing original project. Manufacturing model with gluing of heat protection panels was done in the TUSHINSKY Machine Building Plant under the leader of Mr. Zverev I.K. and Vostrikov M.N..

The Deputy Chief Designer of the BOR-4 model from NPO MOLNIYA was Mr. Mikoyan S.A., the leading designer was Mr. Gress V.U.

In the creation of the model from NPO MOLNIYA took part Mr.: Ezhov V.P., Rozanov I.G., Mikrukov I.F. and other.

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Figure 1. The BOR-4 orbital model

The BOR-5 Sub-Orbital Flying Model

To receive the experimental aerodynamic characteristics during development of the BURAN space vehicle, the BOR-5 flying model was designed. It presented geometrically similar copy of the BURAN reusable space vehicle made in the 8:1 scale.

The model weight was approximately 1450 kg.

The model development and tests were the parts of general program on BURAN creation.
The BOR-5 purposes were:

  • to determine major aerodynamic characteristics in real flight conditions at high velocities;
  • to determine aerodynamic coefficients, lift-to-drag ratio, balancing characteristics, roll, pitch stability and to compare them with calculated characteristics;
  • to investigate pressure distribution along model surface;
  • to determine heat loads;
  • to determine acoustic loads;
  • to check adequacy of techniques for calculation of aerodynamic characteristics.

The launch of the model into sub-orbit was being fulfilled by the K65M-RB5 ballistic rocket from the launch pad located in the Kapustin Yar test range in Balkhash lake direction. The rocket with the model was being approaching maximal altitude, approximately 210 km, and after separation the model continued its way along ballistic trajectory with approximately 5 km/s velocity. In atmosphere, from approximately 50 km altitude the model flight was being done with programmed variation of bank angle and angle of attack at trajectory, chosen to provide optimal dependence Reynolds number from Mach number corresponded to the flight path of the BURAN space vehicle. It demanded greater indicated speed - from approximately 1070 km/h in the beginning of test leg to 850 km/h in the end (while maximum speed of the BURAN orbiter on this leg is 650 km/h).

As a result the temperature on the vehicle’s surface was greater on 1000 degrees than for the full-scale BURAN vehicle. That’s why the heat protection of quartz tiles similar to the protection of the BURAN orbiter could not be used there. On the model ablation heat protection was made of materials on the basis of mineral fiberglass plastic and the nose cone was made of tungsten-molybdenum alloy. The radioparent heat protection material (fiberglass plastic with silica filling) was tested too.

The model’s programmed control was performed by the on-board autonomous control system, which was receiving information from inertial navigation system.

On sub-orbital trajectory the model angular orientation of the model was ensured by micro jet engines and after upper-air descending the model was controlled by plane-like control surfaces, which for the first time were used in our country at such great velocity and such great kinetic heating of material.

The flight range of the BOR-5 model from starting point to landing was approximately 2000 km. At 7…8-km altitude the on-board program control system forced the model by means of rudders into the tight spiral for decreasing of the flight velocity. And at approximately 3-km altitude the parachute was being developed to provide landing with 7*8 m/s vertical speed (Figure 2).

The on-board telemetry system recorded all information internally and then transmitted it to the Earth for analyzing of aerodynamic characteristics. The information was received from several accelerometers, rate and acceleration sensors, free gyroscopes, pressure indicators, ailerons and rudder deviation sensors and sensor for measuring hinge moment on rudders. Besides, the information was transmitted from temperature thermocouples, calorimetric sensors and other temperature sensors.

The thermal indicator paint and the melting indicators were also used.
From 1984 five launchings have been fulfilled:

  • 501 model – on 6th July, 1984;
  • 502 model - on 17th April , 1985;
  • 503 model - on 27th December, 1986;
  • 504 model - on 27th August, 1987;
  • 505 model – on 22nd June, 1988.

The first two launching were performed in accordance with a program of flight-design tests of launcher rocket specially modified for the BOR-5 model. They included tests of model system functionality.

During the first launching the separation of the model from rocket launcher didn’t appear because of electrical failure and they fell down together while the second launching was absolutely successful.

Three launching according to the program of the BOR-5 model test appeared to be successful, were passed and they provided specialists with the full amount of data needed. The actual lift-to-drag ratio of the model appeared to be greater than calculated one.

The BOR-5 model was designed in NPO MOLNIYA under the direction of Deputy Chief Designer Dr. Samsonov E.A. The leading designers were Mr. Bogov U.P. and then Grachev I.G.. The construction design was made under the direction of Mr. Kavunovsky N.P. by Mr.: Chistov V.A., Khorev D.M., Glotov V.I., Mendzilo V.V., Frolkov V.M., Kiryanov I.V and other.

The models were produced on the Myasischev V.M. Experimental Machine-Building Plant under the direction of Mr.: I.M. Lipkin I.M. and Tvorogov N.G..

The BOR-4 and BOR-5 models were equipped with autopilots with a computer and on-board measure system. These systems were produced by the Flight Research Institute (Ministry of Aircraft Industry) under the leaderships of Dr. Vladychin G.P., Dr. Kondratov A.A., Dr. Fedorovich A.A., Mr. Khanov I.K. and Tishenko V.V.

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Figure 2. The scheme of the BOR-5 model’s sub-orbital flight

The tests of both model versions (BOR-4 and BOR-5) were performed by the representatives of LII under the direction of Dr. Vladychin G.P. and Dr. Kondratov A.A. The specialists of the Military-Research Institute, NPO MOLNIYA and other organization under general supervision of the State Commission, headed by the first Deputy Director of GUKOS, General of aviation, Mr. Titov G.S. also took part in testing.

The Conclusion

The application of orbital and sub-orbital flying models for the confirmation by experimental data of the heat protection efficiency and reliability of aerodynamic calculation became a news in developing of the aerospace systems (ASSs) and was fulfilled for the first time in the world. Such models will find the application in further researches of aerospace systems (ASS).

The tests results of the BOR-4 flying model were used not only in the BURAN program, but also in development of the MAKS Multipurpose aerospace system with the AN-225 MRIA subsonic carrier aircraft. The orbital plane in this system as well as the SPIRAL plane and BOR-4 experimental plane have identical aerodynamic scheme ‘lifting body’ with deflected wing panels.

Wide experience of experimental researches in natural conditions of the BOR-5 model’s orbital and sub-orbital flight and SPIRAL analogue’s launching allowed to choose a well-founded aerodynamic configuration of orbital plane of the MAKS advanced system. In the nearest future this system will allow to decrease the cost of space missions and open new possibilities for fulfilling different tasks due to the advantages of air launch from the subsonic carrier-plane.