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BURAN Orbital

Spaceship Airframe

Creation

Cabin

Dr. Fedotov V.A., Novikov V.K.
The problem to create of a high strength and high air-tightness cabin (cockpit) module body (CM) for BURAN Orbiter was the first time in the country. It was welded of 1201-T1 aluminum alloy and was intended for arrangement in it of equipment components and means ensuring fulfillment of both automatic, and controlled by crew ‘aircraft-like’ landing at returning from orbit to the Earth. The questions of layout optimization, application of new design and technological solutions at development and manufacturing CM, Orbiter’s systems, using methods of their structural and air-tightness tests on specially created full-scale mock-ups completely meeting all requirements of space technique are considered.

Orbiter’s cabin represents a pressurized module (CM), placed in the nose part of fuselage (NPF). The module construction is protected from the effect of aerodynamic loads and heat by the surface of fuselage. The shell of the module (made of 1201-T1 alloy) has a complicated form of a truncated cone with flat segments in the zone of glazing and with the curved forward and flat rear domes.

CM is divided into three bays by internal horizontal floors: command, inhabited room and modular. The strengthening elements (frames, stringers, edging of hatches, sway bracing with internal floors) are included in the primary structure of CM shell. The module is connected to the framework of the nose of fuselage by docking units and stay rods (in the plane of floors).

At the cabin layout development the problems arose connected to both the extraordinary operation conditions and to novelty of the design shape. The CM is intended for both unmanned and manned flight of the orbiter and besides, for usage in Analogue plane, on which the automatic landing was worked out. Distinctions of the cabin equipment and accommodation of the members of crew for different tasks solution during orbital and atmospheric flights has made the selection of optimal cabin layout rather difficult in the sense of compliance with all requirements at minimum changes from version to version. At that the main role was given to the manned mission.

Creation of strong, pressurized construction of the module at minimum mass was a complicated problem. The dense layout of the placed equipment and work places for the crew had to be combined with a rational arrangement of optimal (by criterion of minimum mass) structural members included into the general load-bearing scheme of the shell, and also accepting local loads.

Besides the requirements of strength the construction of the welded shell should comply with the normative requirements for air-tightness under all operation conditions at strict instrumental control. The problems have also arisen in the process of manufacturing the welded assembly of the shell of a complex shape of aluminum alloy.

The principal difficulty was in the necessity of completely automatic welding with mandatory exclusion of mechanical straightening and manual finishing of welded edges from the manufacturing process. This complicated task was essentially new for domestic aerospace technique.

The problems of layout development were decided by the well mastered in the aircraft industry method of consequent working out of the design documentation on the full-scale experimental mockups. The equipment and places for the crew allocation over all three bays was specified on experimental mockups.

First, the crew accommodation and arrangement of electric equipment, onboard cable network and pipelines of different purpose (including numerous pressurized adapters on the forward and rear domes) were worked out.

Accommodation of two to ten members of the crew and arrangement of different equipment of total mass up to 10 t was provided in total.

Two work places with seats, consoles and instrument panels are composed in the command bay, in forward zone, with allowance for the requirements of aircraft standards of Orbiter and Analogue spaceship control. Two work places for working with equipment during the orbital flight and two seats for specialists are stipulated in the command bay, near the rear wall.

All equipment is allocated between the command, habitation and unit bays of CM.

In habitation module, six seats for additional members of the crew, air lock, devices, sleeping places of the crew, cesspool-sanitary system, buffet with diets, systems of CM ventilation, collecting wastes of habitability and many others were located. Thermal insulation was installed on the external surface of CM. In the unit bay, bulky units of means of life support were placed.

The ejection seats with a complex of means foe emergency escape were installed on the first two working places. It was difficult to provide a convenient crew placing, when wearing space suits into ejection seats, and to ensure their fast escape from CM in horizontal and vertical position. The problem was to provide ergonomic requirements on external view and view of consoles, instrument panels, range of control handles.

3 experimental mockups of the command bay and 5 experimental models of the complete module of different purpose were created. The experimental command bay mockups were handed over to co-developers of equipment.

The CM-1KA mockup, including the module and Orbiter’s nose mockup, was installed on a vertical rotary stand and used for working out the escape by crew from the spaceship at the start.

The module’s position inside the fuselage was corrected on the same mockup.

The equipment for Analogue, intended for horizontal flight tests of automatic unmanned landing working-out, have been simulated on CM-KB mockup.

The MK-GN mockup of a completely metallic structure and pressurized was created for water-tank test (the crew primary training and work in space suits in a weightlessness state was accomplished on it).

The MK-KB.E mockup was applied for electrical networks’ working-out, then it was included into the complex stand of NPO ENERGIA. On the MK-KB.U mockup simulation of nominal version of the equipment and crew places was carried out.

Further on, metallic modules of the cabin made on the basis of main operational documentation (both on abnormal and nominal technique, distinguishing only by different condition of 1201 alloy), which had been created for ground-based working-out of all systems of the Orbiter, were used to specify the layout.

In the bays of the cabin life support system (LSS), emergency escape system (EES), furnishing equipment, means of fire protection (MFP), means of biomedical support (MBMS), and temperature control support system (TCSS) were placed.

At creation of the systems for BURAN Orbiter’s airframe the whole experience of creation of domestic and foreign space flying vehicles was taken into account. The main attention was focused on the increase of reliability and safety in operation.

More comfortable conditions promoting the expansion of works scope executed by the crew at smaller ‘mass costs’ were created for the members of crew.

The large attention has been given to experimental ground-based stand working-out on full-scale mockups of the cabin, and all systems and subsystems were included. Scientific collectives of the leading aircraft, space-rocket and medical organizations were attracted to creation of the mentioned above complex.


Life Support Means

The means of life support create conditions necessary for the crew staying in pressurized and in the depressurized cabin at all stages of Orbiter’s flight.

The Orbiter’s Life Support System (LSS) includes the following parts:

  • gas composition system (GCS);
  • pressurization and depressurization system (P&DS);
  • individual life support system (ILSS);
  • water supply system (WSS), including technical and the potable water systems (TWS and PWS, the last includes water purification units powered by electrochemical generators, and units of its conditioning);
  • food supply system (FSS);
  • waste management provision system (WMPS);
  • means of biomedical control and support:
    - medical monitoring (MMM),
    - means of radiation control (MRC),
    - means of sanitary-hygienic maintenance (MSHM),
    - means of rendering of medical aid (MRMA),
    - means of unfavorable influence of the factors of flight prevention (MFFP).

The nitrogen-oxygen atmosphere of BURAN Orbiter’s cabin is adjusted according to the component partial pressure by GCS system and according to the absolute pressure by R&DS system. The structure of atmosphere is close to the Earth one. According to the conditions of fire prevention control, the contents of oxygen limits are restricted by volume 40 %.

The P&DS system prevents the CM over-pressurizing at change of atmosphere, which is necessary for elimination of fire consequences. P&DS also equalizes the possible negative pressure gradient, which acts on depressurized CM at Orbiter’s entrance into dense layers of atmosphere.

In case of pressure drop in CM, P&DS automatically supplies air from cylinders. Regenerators absorbing carbon dioxide, emanating oxygen and adjusting temperature are the actuating units. Special cylinders, integrated in units, are used for storage of reserve air compensatory for possible outflow and ensuring air-locking and other needs. Pressure control at its decrease is executed both automatically and manually.

STRIZH space suits and ORLAN special space suits for extra-vehicular work are included into the structure of ILSS. ILSS provides habitability of crew in all cases of CM depressurization at staying in space suits including presence of crew in an air lock. By means of ILSS space suits are dried at their preparation to reuse. The space suits are equipped with the units of WMPS and potable water supply. The multifunctional WSS is applied for the first time in LSS complex where water is generated in electrochemical generators (ECG) including regeneration of moisture containing waste of crew habitability, cleared, conditioned and supplied to the crew. ECG is a common source of water for the systems of potable and technical water.

In addition to the water obtained from ECG, WSS contains a small stand-by reserve of water (~10 l) picked up from the Earth. WSS supplies TCS and hydraulic system.

In connection with the foreseen reusability of Orbiter’s application, ECG produces rather large water volumes.

WSS is divided into three subsystems:

  • debit and credit registration, regulation of distribution, redundancy and drop of excesses of water overboard (DCS);
  • service of evaporators in abnormal conditions and on the final stage of flight (WSS-TCS);
  • hydraulic system WSS, maintaining evaporators of hydraulic system (also at the final stage).

The operational modes of WSS units are determined by control system automatically, the crew interference is required only in emergency situations. Charging of WSS with distilled water on the ground is made in a volume of 370 liters. WSS is a new system and was never used before in domestic space technique.

FSS is a set of food staffs packed in aluminum tubes, metallic cans and plastic packages, which are picked up from the ground counting on four times meals for the crew. Composed according to rations for one man per day, the products are stored in containers in the buffet. There is a food heater and a facility for recovery of sublimated products with hot water is stipulated. Wastes are saved until Orbiter return to the Earth.

WMPS is intended for the collecting, storage (isolated from CM atmosphere) and return to the Earth of products of the crew habitability. Separate urine and feces storage in the receiving tanks is intended for one flight. Transportation of wastes is made with airflow from ventilators. Absorption of unhealthy impurities and odors is made by air pumping with its consequent, after filter, discharge into CM atmosphere.


Emergency Escape Means

The means of emergency escape of BURAN Orbiter were developed in two versions: MEE intended for GLI, and MEE (CMEE) for orbital flights.

MEE OK-GLI formed for saving a crew of two pilots-testers by method of double escape at occurrence of emergency over the whole range of altitudes and flying speeds.

In MEE OK-GLI the following are included:

  • ejection systems of K-36L type (development of MZ ZVEZDA), modified for double escape option;
  • system of drop of covers of emergency exits;
  • automation unit of emergency escape.

For maintenance of emergency escape from Analogue on the ground in case of emergency landing the means of escape through emergency and access hatches are developed. The Analogue’s emergency escape system has passed a complete cycle of special integrated tests with positive results. The scheme of double ejection was worked out during the tests on rocket track for the first time in domestic practice at speeds up to 600 km/h.

The complex of emergency escape means on the Orbiter N1 was intended for saving crew of two cosmonauts in case of emergency situation at stages of Orbiter’s start, ascent and landing in the flight altitudes range from 0 to 25 km at Mach number 2.5. The escape at this stage is made under the commands from the handles of ejection, from automatics and from the flight director.

The emergency saving of the crew was complicated with a wide band of modes and conditions of flight. Because of a steep glide path, no launch escape system from the used earlier in space-rocket engineering could be applied. Air ejection seats had rather a limited area of application within the altitudes and flying speeds range. They can’t provide the necessary removal from the launcher in case of its explosion at the start and fly-around of an exhaust jet of rocket engines at emergency during the ascent. Application of separated and recoverable vehicles (bays) would result in significant reduction of mass of the payload and necessity to decide problems of separation, withdrawal and landing of the separated vehicle (bay) on the steep landing glide path.

A comprehensive approach to the crew emergency saving task solution has demanded to develop the system for BURAN Orbiter on the basis of modified ejection seats in combination with the system of Orbiter’s emergency separation from the launcher. These means should provide the crew saving of a number up to four men in the majority of emergency situations.

Emergency escape system could be applied on the launch pad from the moment of tower removal from Orbiter and up to speed of about M = 2.5…3.0 at ascent. This is a boundary of application of ejection seats of open type for kinetic heat. As to the descent and landing stages, these means may applied after slowing down to M = 2.5…3.0 and to Orbiter’s stop on the runway. If necessary, the crew has an opportunity to leave the spaceship on the runway through an operational (entrance) hatch or through emergency exits with the help of special ropes with braking devices.

The control of emergency escape system was made by automatics, which provided performance of other functions of saving operation including Orbiter’s rapid departure from the launcher. The ejection was provided from launching and landing position of seats.

In case if explosion of the launcher occurred, the ejection provided the seat removal for the distance up to 400 m (which exceeded capabilities of a usual air ejection seat) and its withdrawal from a jet of running engines and from facilities of the launch complex. The seat was actually transformed into a peculiar flying vehicle with its own propulsion unit, automatics and control units. At descent and landing phase the accelerating unit was detached from the seat. STRIZH space suit, specially designed for BURAN at MZ ZVEZDA, was used for the seat. A unit of life-support for descent from high altitudes and portable emergency reserve for survival in deserted district were included in its structure.

At emergency system application, it were formed (at NPF and CM) the emergency exits with safe trajectories of motion of expendable panels in all modes of escape. In order to cut CM and NPF panels for emergency exits of seats special linear separators (LS) were used, for the first time in the branch, on the basis of charges of explosives providing to the crew safe levels of impact and acoustic loads and absence of debris.

Emergency escape system of BURAN has passed the initial stage of interdepartmental tests (5 launches) with a positive result.


Conditions of Life Equipment

The basis furnishing equipment was completed with the following units:

  • buffet with portions of meals and means of ingestion;
  • sleeping places;
  • items for rest and comfort.

The interior of CM completely met the requirements of prolonged flight in conditions of weightlessness, as well as those of human engineering, ergonomics and conditions of habitability of crew in artificial atmosphere of habitation. The interior elements and its color promoted creation of favorable conditions for performance by the crew of the duties.


Means of Fire Protection

At development of means of fire protection (MFP) the specificity of fire origin and development in conditions of space flight were taken into account. There is no free convection in conditions of weightlessness, owing to what the burning rate of materials and flame spread decreases, however, the presence of ventilation by means of the thermal control system’s induces forced convection and thus accelerates the flame spreading.

At development of means of flame safety the principle of fire prevention was adopted by application of materials in CM construction which are not supporting combustion, and special protection of onboard electric networks. Fire detection and extinguishing units, an autonomous system of fire suppression, manual fire extinguishers and smoke alarms were entered into the structure of fire-prevention means.

The crew extinguishes fire by supplying insulating gas (hexafluorated sulfur) with the help of manual fire extinguishers. The insulating gas is supplied to remote places from the cylinders of autonomous system by pipelines at opening manual valves. After fire suppression the change of CM atmosphere by means of LSS is stipulated for liquidation of smokiness and products of combustion removal.

In unmanned flights of Orbiter, fire protection was provided with creation in CM of nitrogen atmosphere with oxygen concentration about 10%.


Biomedical Support

Researches and experimental works, which have been carried out by the Institute of Biomedical Problems (IMBP) and a number of other institutes, allowed to develop techniques and means ensuring the crew performance of a set of operations including those on Orbiter control in specific conditions of flight.

The medical techniques, permitting to inspect the state of crew at landing and to forecast its functionality before performance of responsible stages of flight, were developed. Means of preventive measures of the unfavorable factors of flight were developed for the first time, and optimal structure of means for the Orbiter’s flights biomedical support is completed.

The executed biomedical researches on objective assessment of functionality and efficiency of a complex of LSS of BURAN and on materials of study of functional condition of two-man crew within 18 day, can be taken for the basis for application on manned reusable vehicles of aerospace systems.


System of Thermal Mode Maintenance (STMM)

STMM automated pneumatic and hydraulic system is an automated system of a radiator-evaporative type, which is permanently operational on the Earth and at all stages of the flight.

For the first time in domestic practice, the multifunction system has been developed for temperature mode maintenance with removal of heat excess. The heat up to 30 kW may be removed in orbit with the help of mobile radiator-emitter (on the doors of payload bay), and also the heat up to 40 kW at the stages of ascent, descent and landing, using water and liquid ammonia as cooling agents. At that the evaporation of water occurred at two different temperature levels: 5°С and 100°С.

An unprecedented complex STMM working out was executed on a newly created unique experimental base:

  • on a full-scale stand for hydraulic testing;
  • on a stand for thermal-vacuum tests of separate parts of the system with simulation of thermal effect of a near-earth space (at that, the nominal work of water evaporative heat exchangers could be carried out);
  • on a full-scale stand for interdepartmental tests of LSS an medical support systems and temperature and moisture mode of atmosphere in CM bays checkouts and computer-aided control by a system operating under the scheme: ‘man-computer-system’.

STMM consists of means of passive thermal control (SPTM) and thermal control system (TCS). SPTM is a thermal insulation of CM, TCS units and pipelines, heat-insulators and special temperature-regulating coatings of glasses and non-thermal-insulating surfaces of CM.

Installed on the internal surfaces of payload bay doors, the radiation heat exchanger panels (RHE) during the orbital flight are open (together with the doors) and closed before descent. At descent (down to altitude of 35 km), the thermal load is removed by water, whereas at lower level ammonia evaporators. Two internal and two outside contours are included in TCS. The internal contours provide the cabin atmosphere temperature and moisture mode support and thermostatic control of the instrumentation-service equipment in CM and on CM, while the outside contours provide the thermostatic control of the instrumentation-service equipment in fuselage and thermal load removal.

‘Antifreeze-20’ is used as heat-transfer medium in internal contours, organic-silicone fluid is used in outside contours. From the internal contour through heat exchangers of connection, heat is transmitted into the outside contour, and then is dumped into ambient space.

Essentially new in TCS is that the atmosphere temperature and moisture mode is supported by separation into cooling and drying, which is performed by different units. Drying as a separate process allows to simplify considerably the construction of these units and the inter-flight service as a whole. A detailed description of design and principles of operation of the listed systems is explained in the book ‘Reusable BURAN Orbiter’, Moscow, MASHINOSTROENIE P.H., 1995, p. 215.


Strength and Air-Tightness Problems

In the process of CM creation, the problems of the Module strength were solved by theoretical and experimental methods. The complicated statically indeterminate construction exposed to the combined action of concentrated and distributed inertia loads, calculated by finite element method (FEM). FEM inclusion into the automated system of optimization of primary structures from the early stages of design was new. In the process of the loading scheme refinement the spectrum of strength, design and technological limitations was entered into calculations which permitted the maximum approach of calculation model to the actual design.

About 5,000 joints and 25,000 unknowns were included in the finite difference model. For the first time in the branch, substantiation of the applied method of pressurized body at combined loading strength provision was confirmed by its independent static tests in the assembly and separately. Calculations and experiments have been made for the fragments: panels, edgings, pressure domes, canopy windows, joints of equipment installation and its attachment to fuselage.

In the process of tests, the stability was checked up at pressurization of axes’ positions of command and visual devices of control system relative to the airplane axes. CM was subjected to dynamic tests under the special program, which has provided amplitude-frequency characteristics determination, and passed the shake-table testing with measurement of stresses in load-bearing elements of structure.

At the very first stage of the cabin creation, the special attention was focused on simultaneous studies of strength and air-tightness of weld joints of the shell of the module.

At selection of CM assembly technique for fatigue resistance, different kinds of welding were tested:

  • AHAW - automatic helium arc electric welding;
  • MHAW - manual helium arc electric welding;
  • EBW - electron-beam welding.

The best results, close to the characteristics of single-piece (solid) metal were obtained at EBW, at welding of slabs of large thickness.

The correlation of fatigue resistance of welds with their directivity relative to the filaments of roll stock, kinds of defects (edges displacement, cracks, pores, lacks of penetration, etc.), nature of loading (static, vibration, acoustic) were detected. The important innovation was ‘softening’ of strong concentrators of stresses in the zone of the shell cut-outs for hatches of ejection at the expense of adjacent installation of a number of supplementary concentrators with much smaller factors of concentration. During optimization of weld joints, the original engineering solutions on increase of welds longevity (for example, welding making with single or bilateral rough tolerances, with their consequent removal, together with an overwhelming majority of internal defects) were offered and implemented. Technological working out and preparation of production for CM manufacturing were accomplished with designer supervision from EMZ at TUSHINSKY Machine-building plant simultaneously in several directions. The manufacturing processes for different elements’ machining were mastered (intermediate products of high-strength 1201-T1 alloy, bulky panels of ‘wafer’ type with small width of walls, etc.). Special welding equipment was created necessary for provision of air-tightness of long shell welds with overall length of up to 152 m.

On the basis of this experience (under the proposal of the leading technologist of NIAT Mr. Khristoev Yu. Ya.) for the first time in domestic engineering, the general purpose welding-assembling stand (UPFS-2) was created, on which at assembly of one system, preparation of panels edges by milling and their automatic welding was performed. For flawless manufacturing of welding-assembly, in the assembly department the special climatic conditions were set up (cleanness, temperature, air humidity, absence of wind, etc.). The special attention was given to compliance with the rigid requirements to the local and general air-tightness of the Module’s bodies, which was checked out by tests in VK-48 vacuum chamber at NPO named after S.A. Lavochkin. The final mastering was divided in two stages:

  • manufacturing according to an abnormal technique (without automatic welding, with admittance of mechanical straightening of the connected edges);
  • manufacturing according to a nominal technique with completely automatic welding-assembly and consequent pre-delivery tests in an armored box.

The high requirements to stability of CM air-tightness have demanded a special experimental technique of its control at the stage of inter-flight service, when the module is allocated inside the fuselage with the minimum gaps. For this purpose the complete set of special equipment was created, where hexafluorated sulfur (insulating gas) was used as trial gas instead of conventional helium.

The system with the use of sensors with acoustic emission and determining the zones of damages development and disturbance of continuousness of material was created for onboard systems monitoring the integrity and air-tightness of the body.


Tests on the Stands

The system working out on stands together with crew and ground-based services operators’ training on a specially created training complex was an independent direction. Full-scale mockups of cabins were used in these works, each of them was composed with reference to a definite purpose.

The following objects were manufactured according to the abnormal technique (of the shell material admitting mechanical straightening of modular body):

  • MK-T - for thermal and ventilation tests, work-out of TCS, WSS and MFP systems on a stand;
  • MK-KS - for tests of the equipment within the structure of a special complex stand at NPO ENERGIA.

Under the nominal technique for ground tests and two flight models of an airplane the following were manufactured:

  • MK-ML1 - for OK-ML1 airplane intended for frequency tests;
  • MK-MT - for OK-MT airplane (static structural strength tests with consequent transfer for working out of technological operations on the space port objects);
  • MK-TVA - for joint tests with the nose part of fuselage (thermal resistance, vibration resistance, acoustic, resource from pressurization, etc.);
  • MK-TVI - for vacuum tests;
  • MK-KMS - for a complex simulating stand at NPO ENERGIA;
  • MK-M - for complex interdepartmental tests of LSS in VU-1000 vacuum chamber.

Two cabin modules were established in the Analogue airplane and in the Orbital vehicle.

With the purpose of costs and terms reduction the framework of the cabins mockups for the training complex was made under the operational documentation on mockups of an abbreviated design, (glued-riveted, instead of welded assembly of expensive milled panels), and in the abnormal framework fragments of the nominal systems were installed (under the nominal drawings, but with the help of transient brackets) pursuant to the block structure for each simulator.

In addition to the mockups of the training complex the following were manufactured and handed over:

  • to the Cosmonauts’ Training Center – the mockup of a command bay with the equipment for СТСС simulator;
  • to NII RTK – fragment of CM (FCM) for a simulator intended for working out the operations with Orbiter’s manipulators.

The works on the listed CM mockups have played the great role in implementation of the ground-based optimization of all systems of BURAN Orbiter, and of training its flight and terrestrial crews.

BURAN Orbiter, as against the earlier created domestic spaceships, was the first airspace flying vehicle which accomplished an orbital flight with automatic unmanned landing.

The absence of operational experience of FV of such purpose has essentially determined the complexity of the set of works, which have been carried out at creation of the cabin and its equipment. This explain the greater than in aircraft construction, value of layout and operation of systems on full-scale experimental models of the cabin module working out. The scope of works on manufacturing strong and highly hermetic load-bearing welded construction of aluminum-lithium alloy is also explained by this reason.

Design of the cabin and its equipment were brought to the level sufficient for performing the manned orbital flight by BURAN spaceship, which, unfortunately, due to the circumstances, independent of the initiators, was not carried out. The experience of creation of BURAN cabin, ensuring comfortable conditions to the members of crew at the ascent, flight in space and returning to the Earth, will undoubtedly be used at designing the perspective airspace flying vehicles.