BURAN Orbital

Spaceship Airframe

Creation

Simulation on Piloting-Research Complex at Cosmonauts’ Training Center

Dr. Gorbatenko V.V., Shurov A.I., Vaskov A.S.
One of the initial stages of works on the control system for the reusable winged spaceships, orbital plane (orbiter), using stand simulation with effect of g-load factors on the pilot at descent is described. The paper presents some results and shows possible fields of their application.

In 1975 the Mikoyan Design Bureau suggested the idea of creating research facilities under the SPIRAL project within the Gagarin Cosmonauts’ (Astronauts) Training Center (CTC). The following organizations took part in these activities: NPO AP, MIEA, TsNIIMASH, Central Aero-Hydrodynamic Institute (TsAGI), NPO AO, MAI, DPKO RADUGA and others.

The basic aim was to work out the technique of manned space flights’ crews training, as well as to develop handle-operated, director, and automatic control systems for advanced space flying vehicles with the consider of the descent phase g-load factor effect on the pilot after weightlessness simulation.

General problems and tasks were branched and divided among the specialists. Colonel Lubimov A.V., Chief of the Centrifuges’ Department, was responsible for creation of the Static and Dynamic Stands on behalf of the Cosmonauts’ Training Center. Mr. Naidyonov V.P., Gorbatenko V.V and Vova V.E. from NPO MOLNIYA were responsible for mathematical flight dynamics model of the space flying vehicle. First valuable results made the heads of many enterprises and institutes believe in the future of the researches led by the Center. Their visits to the Cosmonauts’ Training Center became frequent. They discussed the results and developed new fields of research.

Simple numbering of the things conducted then may be the best memories and the best evidence of the tremendous work done in those years. The list of the problems solved may astonish a stranger. But those involved would feel the nostalgia for the years of self-denying work done together.

Figure 1. General layout of the Pilot-105 piloting-research complex:

1 – analogue computer; 2 – control for follow-up system; 3 – multi-purpose converter

Piloting-Research Complex

In 1976 an analogue-digital simulation complex was created at the Cosmonauts’ Training Center under the program: Orbital Plane g-Load Affected Flight Research. The purpose of the complex was to simulate the flight of orbital plane, designed under the SPIRAL project, at the phase of controlled descent in the conditions of g-load effect on the pilot. Handle-operated, director, and automatic control modes were supposed to be worked out on the simulator.

The structure of relations between the elements of the Pilot-105 piloting-research complex is shown on figure 1.

In corresponding with the resources of the computers available at the time and with the operation experience of such kind of the complexes, the distribution of functions between analogue and digital computers was as follows:

• Digital Computer – solution of a set of equations for long-period (trajectory) movement and flying vehicle’s center of mass movement control system;
• Calculating the dynamical coefficients of short-period movement equations;
• Analog Computer - solution of a set of equations for short-period (angular around center of mass) movement and short-period movement control system (system of stabilization).

Including the CF-7 centrifuge into the simulation circuit allowed to study the effect of g-load on the pilot’s dynamic performance in manual (handle-operated) and director control modes simultaneously with the solution for the problem of Orbiter’s control system synthesis at descent.

Maximal estimated accelerations on the Orbiter’s descent trajectories don’t exceed 1,5...3,5 g (at a roll angle modulus of up to 70°). However they are a long-time acting in a head-foot direction unlike those (a chest-back direction) on VOSTOK and SOYUZ manned space vehicles. This together with the increased acceleration sensitivity of human body after weightlessness makes it vitally important to study the effect of accelerations on the Orbiter control in handle-operated and director modes.

The performance of the CF-7 centrifuge’s electric actuator makes it possible to simulate the accelerations at the descent trajectory. Particularly, its pass band is of 0.3...0.7 Hz, so it allows to follow the acceleration of the Orbiter descent movement with essential frequencies of the spectrum not higher than 0.2 Hz.

Basic Problems and Results of the Orbiter’s Flight Dynamics Simulation at the Piloting-Research Complex

After calibrating and testing of the 3D movement mathematical model the complex was assigned to the task of working out and finishing the automatic control circuits designed by major aircraft builders (Mikoyan Design Bureau, Central Aero- Hydrodynamics Institute (TsAGI), MIEA etc). The following important results were obtained:

• short-period movement control algorithms which provide stability and permit to parry the wind gusts;
• a way of guidance in lateral direction using the targeting line was suggested;
• variable bottom limit on roll angle was introduced to prevent wide lateral dispersion by disturbances leading to undershooting;
• calibration parameters for longitudinal guidance functional were optimized;
• roll reversal rate effect on trajectory control quality was studied: it had been proved, that the chosen algorithms of automatic control allow Orbiter to counteract the disturbances and securely reach the desired point at the altitude of 20 km with the miss-tolerance of ± 2km (errors in the equipment and navigation system were out of consideration).

The researches of the second stage were as follows:

• defining the minimum of displayed information needed for the pilot to control the Orbiter in handle-operated and director control modes;
• substantiation the preliminary requirements to the list and layout of control and navigation instruments;
• comparative estimation for two versions of control handles (2-axis dynamo-metric handle and rudder pedals or 3-axis potentiometer handle) for orbital flight and for key points of descent trajectory;
• distribution of functions among the pilot and the automatic control system according to stability and handling characteristics research in the key points of the descent trajectory.

The research on the choice of control handles, instrument panel layout and cabin interior were held with the accelerations equal to those in the key points of the trajectory. The test pilots were chosen from the CTC staff: Mr. Janibekov V.A., Khrunov E.V., Surikov E.I., Khaustov A.I. and others.

These tests caused the necessity to work out a technique of objective estimation of the pilot’s operation based on statistic analysis of the processes in ergonomic system.

The tests had sown the following:

1. With the minimum of information displayed about value and deviation between current and estimated values of roll angle, about angles of attack and slip, and micro jet operation indicators, it is possible handle-operated and director control using Reaction Control System (RCS). There is a need in further research aimed to designing a combined indicator to concentrate the data above in a general display.
2. Comparative estimation of the control handles of two mentioned types showed that control quality for short-period movement when using the RCS (jet) system is practically the same.
3. Handle-operated aerodynamic & jet control is possible, when only damping signals from the control system are available as means of automatics. In this case appropriate characteristics of transient processes are maintained, when the Orbiter is rolling at an average angular speed of 5...10 °/sec.
4. To estimate the quality of ergonomic system the researchers made use of the techniques based on statistics processing, i.e. probability and information techniques. The former is based on calculating the probability of successful (faultless) operation of the system, the latter - on calculating entropy information content of the system.
5. The researches held at continuously acting accelerations in the head-foot direction, equal to those in the given point of trajectory, had showed that when operating the dynamo-metric handle with rudder pedals the quality of ergonomic system drops by 8...10% on average compared to acceleration free operation.
6. The factor of quality criterion variability may be regarded as objective indicator of the pilot’s skill. The variability factor of the test pilots was 5...10%.
7. The researches showed that in certain points of trajectory ergonomic system’s quality depends on pilot’s individuality with a dispersion of values of up to 20%.
The researches of the control modes under the SPIRAL project had made a good base for further research and design works on space flying vehicles.

Turnabout to the BURAN Project

In1976-77 many organizations engaged in spaceships design were assigned the BURAN project. The experience gained with the SPIRAL almost entirely came in handy for this case as well. Practically an entire sector (subdivision) from NPO MOLNIYA was permanently employed by the Gagarin Cosmonauts’ Training Center by that time (the specialists were registered as though on detached duty).

It meant a new form of co-operation. NPO MOLNIYA was engaged the CTC facilities development. A new chapter on manned space flights training facilities development appeared in the technical plan.

A joint research project: Researching and Development of BURAN Orbiter Descent Phase Control System in the Conditions of Actual Accelerations - was started almost by the same parties as previous projects. The research was held through all the steps covered above starting with systems and software calibration of Pilot-105, creation of the Pilot-35 special test bed and ending with conclusions and recommendations on future employment conditions and possibilities. The following specialists participated in this research and design works in NPO MOLNIYA and other organizations:

Mr. Naidyonov V.P., Dudar E.N., Vova V.E., Zazhogin G.N., Trufakin V.A.,. Zhovinsky V.N., Inozemtsev O.A., Kolomensky I.M., Mrs. Melnikova L.M. (NPO MOLNIYAolniya”); Mr. Lubimov A.V., Ryabov V.V., (CTC); Studnev R.V., Kobzev V.I., Yershov V.P., Suprunenko S.N. (TsAGI); Vladychin G.P., Mrs. Yezhova T.A. (Flight Research Institute - LII); Mrs. Khazan M.A., Mr. Beketov V.L., Litvinov Yu.Yu. (NPO AP); Kryukov S.P. (MIEA); Lobanov V.S. (TsNII MASH); Krymov A.B., Mitroshin E.I., Glinsky B.A., Moiseenko V.E. (MAI) and others.

Dr. Lozino-Lozinsky G.E., Chief Designer of NPO MOLNIYA paid profound attention to all the works on the complex in CTC.

Main Results of Piloting Complex Simulation for the 100…20 km Descent Leg

1. A set of nominal descent trajectories with constant temperature at the leg with maximal aerodynamic heat was chosen for the cases of various values of lateral descent range (cross range) taking into account temperature constraints.
2. Guidance automatic algorithm, based on the reference trajectory method, was tested. The algorithm uses the data of current coordinates, velocity vector and its vertical component generated by inertial navigation system. The algorithm was proved to meet the requirements to control precision and stay within the trajectory parameters’ constraints under the effect of disturbances.
3. It had been done the synthesis of the automatic control laws in longitudinal and lateral channels for angular motion around center of mass. That control laws allow to maintain appropriate transient processes quality through all the stage of descent from 100 down to 20 km.
4. A version of the director control loop layout with control signals indication on pilot’s landing instruments was suggested and tested.
5. Calibration parameters were chosen for director control laws and loops to maintain appropriate handling and stability through all the stage of descent.
6. It was proved that different variants of the handles’ connection into the director control loop don’t affect the system’s efficiency at the stage of descent.
7. Integrated Quality Index (IQI) for the Orbiter’s control was suggested and worked out through the descent simulation.
8. The CTC pilots team confirmed the suitability of the given Information Displaying System (IDS), control handles, an stabilization loop settings for a director-controlled descending trajectory flight.
9. Automatic and director control modes compared in non-caution (normal) operation mode. The comparison of precision characteristics and control jets fuel consumption showed that the pilot is capable of conducting a descent flight with quality equal to that one of the automatic mode.
10. Control jets fuel consumption was estimated considering the effect of moments caused by aerodynamic and weigh asymmetry of the Orbiter’s airframe and wind gusts.
11. It was substantiated the time schedule for the aerodynamic and reaction (jet) control units in normal operation at the descent stage of flight.
12. It was shown that reaction (jet) control system (RCS) tolerates a failure of any two control engines (considering the effect of jet and external air flow interference) and ensure in this case an appropriate quality of transient processes.
These conclusions show that stage one of this research and development defined the structure of BURAN orbiter’s control system, showed the principal possibility of its safe recovering into the atmosphere, and outlined the way of further system’s perfection and optimization.

The Features of the Control Modes Interpretation for a Reusable Orbiter

The question about human capability for Orbiter’s control and his role in different situations and flight modes was a natural consequence of this study.

Here we quote Mr. Beregovoy G.T., (Russian cosmonaut) who was the Chief of CTC at the time and actively participated in the research:

‘No matter the safety of automatics in use, human’s role in the manned space flights is understood by all, and he should feel like a master in space, not like an appendage of his own equipment. Only the feeling of mastery gives him the self-confidence he needs...and confidence about the automatics he uses.’

But in this case the designers wondered how to divide the control modes – manual, director or semi-automatic, and automatic for the Orbiter when on a descent flight, as previously used the airplane principles didn’t quite fit the case. The decision was to divide these terms in the following way:

Automatic control – human doesn’t interfere in control. All the signals are worked out instrumentally and directly transferred to control jets and aerodynamic control surfaces. The crew’s role is to check passively the systems’ operation and communication. This mode is conventional for descent stage.

Director control – in this mode a general image of discrepancy is displayed to the pilot as deflections of director bars (needles) of the corresponding instruments. The control is resorted to the actions on the handles aimed at matching the two director bars to zero securing mission accomplishment. Tests revealed that at the stage of descent this mode is useful for pilot’s post weightlessness adaptation before a most demanding stages of pre-landing approach, landing and landing run, where director modes may be conventional.

Manual (handle-operated) control – referred to as pilot’s active operation via controls with minimum of instruments data and guiding the Orbiter to a pre-calculated reference trajectory which enables to beam and land the orbital plane securely provided the existing constraints met. Manual (handle-operated) control at these flight stages may only be used in emergency situations.

Later with the creation of piloting, static and dynamic stands in TsAGI, NPO MOLNIYA and other organizations, other more detailed definitions of manual (handle-operated) and director control modes appeared. They did not contradict, but supplement to each other (see the paper Guidance and Control of Orbital Plane in this book).

Another version of handle-operated control mode was suggested. It was the mode of active operation by two crew members. The pilot operates controls producing signals on rolling, defines reversing moments, stabilizes the roll angle, and trimming the angle of attack whereas the co-pilot (navigator) checks piloting and navigation parameters and defines the roll angle from discrepancy between current data of the parameters checked and those of reference trajectory.

Actual tests, conducted by the CTC pilots, proved the principal possibility of manual control even despite of disturbances. Considerable statistics confirmed that temperature, dynamic pressure, g-load and angular parameters of short-period movement do not exceed the preset constraints.

Models of Defining the g-load Affecting the Pilot after Weightlessness

Next stage defined the effect of accelerations on the pilot after weightlessness.

Military medical experts from CTC and from Aerospace Medicine Institute were invited to participate in this research. To simulate weightlessness they chose the hema-dynamic and hypo-dynamic models i.e. the operator either lay 21 days upside down or was rotated in a position which provided blood flow to his head. Then he took his seat at the controls and was centrifuged under the descent pattern. The results appeared to be absolutely new: about a half of those tested stands accelerations well, the others – badly (the borders between the groups are smeared due to training, seasick drugs, anti g suits etc.). Working capability of those, who stood the g-load well, dropped insignificantly. Basing on this study the medical experts promptly developed a technique of pilots selection in order to send people to space ‘on business’, not ‘on a vacation’. The ‘flights’ in the centrifuges were of a great help also for the control system designers. There was born a supposition of equal information supply of automatic, director, and handle-operated control systems. It allowed them to compare the abilities of the three modes and to prove the information precision requirements to ‘Inertial System - Onboard Digital Computer - Information Displaying System’ highways.

Development of the Information Display System Equipped with Multi-Functional Situation Displays

Naturally the next step on the director- and handle-operated control modes finalizing was to develop the layout, tasks, and ways to use the information displaying system (IDS) and controls.

The instruments previously mounted on the Pilot-35 test bed were just analogues of those supposed to be mounted on BURAN. Besides different variants of their position in the cabin and on the instrument panel were tried.

The designing and combination variants of instruments and controls were made by other organizations. All these instruments were tested by pilots at CTC. Figure 2 shows one of the latest variants of co-pilot’s seat interior in the cabin of the Pilot-35 piloting test complex. This development resulted in a comparative analysis of automatic and director control modes of BURAN.

Figure 2. Co-pilot’s seat interior in the cabin of thePilot-35 piloting test complex:

1 – analogue computer; 2 – control for follow-up system; 3 – multi-purpose converter

It have been received the following results:
1. Synthesis and analysis of director control law parameters carried out for the two control principles. According to the first one (automatic) the director bars read the signal values proportional to the discrepancy between current Orbiter’s attitude and reference attitude. According to the second one (director) - those proportional to the discrepancy between the control signal and the signal obtained from the handle. The simulation verified that both principles produce comparable results in control precision and control jets fuel consumption. Besides, the former one more corresponds to the stereotype, have gained by professional pilots, and provides a safe transition to handle-operated control.
2. Director and automatic control modes were compared as for the use of electromechanical devices and electronic Multi-Functional Displays of situation (MFD). The modes appeared to have close transient characteristics. A series of 30 ‘flights’ revealed, that he quality of director control depends on the pilot’s skill. The latest ‘flights’ scored a decrease in fuel consumption by 50…60% compared to the earlier ones. In addition, the indicators of the Reaction Control System (RCS) jets operation helped to lower fuel consumption by approximately 20%.
3. It was made a synthesis and a selection of variants of informational frames for the MFD vertical and horizontal situation displays to provide the pilot with the necessary complex flight information.
4. A technique of pilot’s activities estimation was developed to analyze the results of the centrifuge training in the conditions of g-loads.

It uses generalized and particular control activities’ parameters as well as pilot’s psycho-physiological situation data. The generalized data were those of the Orbiter’s handling capability and the crew’s fitness for the work whereas consumption data, erroneous actions, critical situations organism condition changes etc. were taken as particular data.

The results of the semi-actual simulation on the complex laid the basis of the BURAN preliminary and technical project.

Many inventions were claimed and patented during the research and designing, for example, stabilization loop for yawing control system which doesn’t need slide angle data [2], director control mode [3], integrated quality index [4] and others.

The researches on the problem listed above were carried out up to BURAN Orbiter’s unmanned flight. Algorithms and software were continually advanced and optimized. The safe landing of BURAN gave a new impulse to these works. All the participants of this research and design work began to process the results of telemetry and were enthusiastic about the manned flight. The importance of CTC activities rose. Handle-operated and director control modes, time schedules of pilot’s actions in normal and abnormal situations were thoroughly revised. There were intensively developed the algorithms for BURAN Orbiter’s return maneuver after separation from rocket launcher in emergency situation when injecting into an orbit. It was developed the procedure of transition from emergency trajectory to normal-state trajectory.

Unfortunately, the BURAN project was dismissed under the well known circumstances, and all research and design works have been canceled. However, due to its versatility the scientific and practical experience of control modes development gained on the Pilot-105 and Pilot-35 piloting research complexes at CTC may be of great demand when designing reusable orbital planes.

Literature

1. Khrunov E.V., Lubimov A.V., Mitroshin E.I., Krymov A.B., Naidyonov V.P., Gorbatenko V.V., Vova V.E. Assignment of the Task for Studying Director and Automatic Orbiter’s Control Modes on Analog-Digital Computer Incorporated Semi-Actual Simulation Stand (Almanac ‘Scientific Readings on Aviation and Astronautics’). – Moscow, NAUKA Publishing House, 1980.
2. Gorbatenko V.V, Naidyonov V.P., Kobzev V.I., Khrunov E.V., Shurov A.I. Flying Vehicle Yawing Control Device. Inventor’s certificate No. 156832 (USSR).
3. Beketov V.L., Gorbatenko V.V, Naidyonov V.P., Kobzev V.I., Khazan M.A. Flying Vehicle Yawing Control Device. Inventor’s certificate No. 185452 (USSR).
4. Zhovinsky V.N., Kolomensky I.M., Gorbatenko V.V, Naidyonov V.P., Vova V.E., Khrunov E.V Control System Quality Probabilistic Estimation Computer. Inventor’s certificate No. 867191 (USSR)