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Full Scale Stand of Equipment (FSSE) and Piloting Dynamic Stand for Training (PDST)
Dr. Nekrasov O.N.
Problems, principles of construction and feature of work of the Full Scale Stand of the Equipment and the Piloting-Dynamic Training Stand, created in NPO MOLNIYA for the support horizontal flight tests of Analogue-Plane of the BURAN Orbital Spaceship are considered.
The role of the headquarters plant collective is always especially important and responsible, when creating new object it is necessary to form the technical requirements to all components of a flying vehicle, and also determine ways and means of experimental work and tests. BURAN orbiter is the unique object. That is why for its onboard equipment improvement and its software development it was necessary to create stands of semi natural simulation.
Large role in stand appearance the group of specialists from NPO MOLNIYA played. Among them were such people as Dr. Chugunov O.D., Mr. Zimenkov V.D., Dr. Balashov M.P., Dr. Nekrasov O.N., Mr. Shetinkin B.V. and Mr. Frolov V.I. These people, being the enthusiasts of semi natural modeling, have been invited for the work from Mikoyan and Tupolev Design Bureaus and from Moscow Institute of Electro-mechanics and Automatics. The group became the center of the future large team that created the FSSE and PDST stands in NPO MOLNIYA.
BURAN orbiter is the first domestic flying vehicle landing on an aerodrome like usual aircraft and supplied with digital remote control system of all control surfaces. The brain of the orbiter was the onboard digital computing system with four parallel and very complicated program that not only controls flight stages but also organizes the work of all systems of the orbiter, inspects their serviceability and given level of safety.
There are more than 50 different systems developed by different enterprises established on the orbiter and many of them have also co-developers cooperation. It is clear that each system has the principles of operation, different operational modes and, of course, definite tolerances on output parameters. That is why the first problem of FSSE was the check all systems interaction, mate of their inputs and outputs, regulation and set-up of systems operational modes and aggregates, so that installed on the orbiter they worked properly at all stages of the flight. The second problem of FSSE was to check and develop onboard software.
The FSSE stand is first of all BURAN orbiter airframe on which in stringent topological conformity all onboard systems, aggregates, gears, cables and pipelines are installed. The simulators, power loading, measuring and auxiliary equipment are connected to them through the devices of interface. All these through the system of sensors and adapters are connected to computers.
The full-scale stand of the equipment was under construction in two turns: FSSE-1 for Analogue-plane executing horizontal flight tests, and FSSE-2 for the manned Orbiter leaving in space. Unfortunately, FSSE-2 was not finally mounted at all. Tat is why the further speech goes only about FSSE-1.
The problem was to place stands and computer facilities and create conditions for normal operation. For this purpose there was specially designed and built the stand complex with the area of the main hall 12000 square meters and near to it a six-storied building where four floors were occupied by computer facilities and personnel servicing the equipment.
The FSSE stand is the unique instrument allowing simulate the stages of descent, landing approach and landing in real time.
The FSSE provides simulation the activity of informational-measuring and flight-navigation systems, center of mass and around center of mass motion, to evaluate the characteristics of stability and controllability and also to imitate with the help of loaders hinge moments, which influence on control drives.
Creation of software is very difficult, long and multi-stage process. At the first stage the designers prepared initial data (under the orbiter aerodynamic characteristics, structure and operational modes of the systems and aggregates) with a set of different disturbances and hardware failures. Then the mathematicians developed control laws of motion and systems’ control algorithms. At the next stage software, at last, was created. In such multi-stage process different discrepancies, errors, and sometimes inconsistency in operations of the different enterprises are inevitable.
Errors occur frequently by the most unexpected way. That is why control software correctness work, i.e. of algorithms and programs, is necessary to estimate there, where are collected together real instrumentation and programs i.e. on FSSE. Thus, FSSE became the important means on which it was possible on the ground to check up onboard systems and software correctness activity to prevent undesirable consequences in real flight tests.
FSSE uniqueness and novelty of engineering solutions first of all were dictated by the problem of BURAN to make automatic non-powered landing on runway. In other words, the complex of onboard equipment should have very high accuracy that was not required before for any flying vehicle. That is why the new requirements were presented to the stands.
At creation others flying vehicles semi natural stands were also applied but they carried either individual character or incorporated simulators of low accuracy were used that enabled to receive only an approximated assessment of onboard systems work. For example, when creating Space Shuttle a number of independent and integrated stands for systems’ functioning tests were used. As Space Shuttle landed in manned version at the obligatory visual contact of the crew with the ground the high accuracy of the terminal phase was not required.
When FSSE creating its designers had to decide a number of difficult problems. First of all it was the creation of a multi-computer digital modeling complex. This complex consists of synchronously working in a real time a simulating computer, a control program computer, a special stand information collecting and imitators control computer, onboard digital computer, a telemetry information processing computer.
The next important problem was to develop the mathematical models of object motion, atmospheric disturbances, information systems etc., and these models should have had a capability of their refinement, perfecting and modification in process of accumulation of experimental data obtained during development and testing of the systems. When creating FSSE stand, for the first time in domestic simulating stands development practice there was used a modular design of software allowing change separate models irrespective of the others.
The problem of great complexity was creation of the hydraulic system of loading rudder drives such as simulators of hinge moments working by ‘a booster in a booster’ principle.
The clear characteristic of novelty and uniqueness of the stands is the fact that at their creation there was developed and introduced for about 200 inventions.
On the stand three main operational modes were organized:
In the mode of docking tests step-by-step actuation of every onboard system or its group was done. At this it were tested all circuits and joints docking, the level of signals that the systems exchanged, integrity of circuits on which commands of actuation passed, sequence of their transiting etc.
Mode of complex tests was for a more detailed check of systems functioning and their serviceability in every edge of redundancy and in different types of the tests. So, one of sub stages was the version of pre-landing realization preparation.
On the Analogue-plane complex of onboard equipment if compared with the Orbiter one was self-checked i.e. docking and complex tests were conducted by the control system without the use of ground test equipment. During the tests two problems such as improvement of the program and equipment (installed on the stand) serviceability check were decided.
At semi natural modeling the part of the Orbiter was shown physically as real aggregates, and the other as mathematical models. In a structure of the stand there was the most powerful for those times ES-1060 computer. The software of the computer solved the problem of modeling the flight of the Analogue-plane, its aerodynamic characteristics in view of their possible dispersions, equations of motion and characteristics of the atmosphere with its possible disturbances. The effects of the environment on sensitive elements of the control system and on control surfaces were modeled. The results of evaluations were transmitted to onboard reality. All the aggregates, systems and indicators worked as in the real flight. A pilot or an operator, using the indications of the devices through the control handle, pedals and other controls, ‘piloted’ the orbiter. The control drives overcoming resistance of the simulators of external aerodynamic loads rejected control surfaces that position was transmitted to the computer on the model of motion thus closing the loop. At the stages appropriate to the stages of the flight of the Orbiter (i.e. on gliding and landing) the mode of automatic control was modeled.
The complexity of semi natural modeling is that the maintenance of real time of the problem solution in the modeling computer. The step of onboard computers’ activity was only 33 milliseconds during which in the modeling computer the problem was solved. Mathematicians great knowledge was necessary ‘to squeeze’ the full problem into this short interval.
On the stand the system of onboard telemetry measurements was also involved that collects onboard all possible information and transmits it through the receive station to the telemetry information processing computer. The special system of the automated tests results analysis was entered into the stand structure to treat the information from the storage of the modeling computer and telemetry systems and represent different schedules, diagrams and tables.
The stand tests were divided into three types: development, record and accompanying. During development tests, that were of research character, the engineers could on their own discretion set different entry conditions, disturbances and make different versions of the flight. On record tests the versions of the onboard software that passed preliminary development and intended for delivery on flying laboratories and aboard the Analogue-plane was only used. The record tests actuated not less than 12 ‘flights’ in each mode. Accompanying tests were for remarks analysis obtained at flight tests. The large skill of the experimenters was required to reproduce on the stand set of reasons influenced on deviation from normal activity in real flight. The PDST stand had double assignment. As the stand it allowed to conduct research activities on creation and optimization of control algorithms and as the simulator it was used for preparation and preflight training of the Analogue-plane crews, for improvement of the piloting technique, skills of the exit from abnormal situations at systems different failures.
PDST was constructed by the same principles of semi natural modeling as FSSE stand. But the only real part of PDST was the command compartment of the cabin with full nominal accommodation in it devices, indicators, light panels, handles, buttons etc.; i.e. there was everything that the crew sees and through what it can effect on the plane during the flight. All the rest including models of motion, the models of systems and aggregates activity is shown as the programs loaded into modeling computer. The cabin is mounted on a mobile platform ensuring sensation simulation of angular motions and g-loads. At first, the platform with three-axis was used thus the longitudinal and lateral g-loads (by an inclination of the cabin) and angular motions were only imitated. The stand with a six-sedate platform ensuring imitation of normal g-loads was created later.
Before the glazing of the cabin the system of visualization out-of-cockpit space is mounted. This system represents for the crew the image of the horizon, cloud cover and earth surface around runway, as in actual flight in the terminal area of Ramenskoye (the site of the flight tests). The visualization was done in the scale appropriate to the altitude of the ‘flight’ and under necessary angle of aspect depending on the angular position of the Analogue-plane. As well as in other stands the instructor workplace was organized from which the ‘random’ failures in activity of different systems were entered and the changes of weather conditions could be set.
In 1983 for the realization of starting-up and adjustment activities and tests of the equipment by the Aircraft Industry Minister, General Machine-Building Minister and Radio Industry Minister order there was created an interdepartmental complex test brigade into which the assistants of 47 enterprises were included. From the end of 1984 the Chief of the brigade became Dr. Nekrasov O.N. (NPO MOLNIYA). The first actuation of the stand was held on June 4, 1984. And everything was all right. It was possible to start operational development of the stand and conduct tests.
The work that faced the designers was huge. It was necessary to develop the stand itself, its hydraulic systems of loading of the drives, develop imitative and processing telemetry software etc. It was also necessary to check up onboard equipment i.e. to solve the main problem. The work was complicated by the imperfection of computer facilities. The main modeling ES-1060 computer worked well in a batch mode of problem solving and was not adapted for real-time activity; what’s more TUSHINSKY Machine-Building Plant and the tram route provided powerful industrial interference and that did not promote the normal activity of the computer. The most terrible words for us then were: ‘the ES has hung up’. It meant that the terms are again broken and it was necessary to change the program of the tests.
We overcame the difficulties by super human efforts. The engineers and the heads such as Mr.: Naidenov V.P., Pereverzev V.T., Sharensky V.A., Inozemtsev O.A., Aleskin A.B., Risenberg V.H., Gusakov A.I., Kalinin M.A., Karnauhov S.S. (NPO MOLNIYA) and many others sometimes for some day did not leave the stand. Only their talent and self-spring back has provided the necessary scope of testing. Within the frame of this short paper it is impossible to name everyone who was the part of the stands and without whom the stand could not exist. Those were not only the workers of NPO MOLNIYA. Almost constantly worked on the stand were the experts from the co-developers: Mr.: Mesheryakov G.M., Kostritso R.P. (NPO AP), Bonk R.I., Kuznetsov U.V., Andreev V.P. (MARS DB) and others. To the work connected to the stand more than 800 men there were totally attracted at different stages.
Large understanding and support we received from our management. Every day Dr. Lozino-Lozinsky G.E. (sometimes on Sundays and holidays) discussed the working process on the stands and did his best to help the work to go on. Mr. Sistsov A.S. (the Minister of Aircraft Industry) and later his assistant Mr. Gerachenko A.N. each Monday heard the reports on the stands activities with the purpose of rendering of the necessary help. As a result of semi natural tests the conclusions about the tolerance to the flights of the flying laboratories and the Analogue-plane were given. The materials obtained on stands have come as a component in the base of the conclusion about the first flight of BURAN Orbiter.
The methodology application created for the Orbiter due to later development is especial one taking into account the sharply increased productivity of modern computing systems. It will allow to conduct research of flying vehicles structure and their characteristics and their systems at the earliest stage of the designing that will reduce essential terms of creation and costs on its development and will also lower necessary volumes of flight tests.
For stand-modeling creation 25 employees of NPO MOLNIYA and co-developers were awarded with USSR Soviet of Ministry award. It was the last award of the Soviet and the only collective one for the whole BURAN project. But, perhaps, the most important merit of the collective that created the stands was the estimation of the pilots. After the first flight of Analogue-plane the test pilot Mr. Stankyavichus R.A. has sparingly said: ‘There is no difference with the stands’.