Lavochkin Scientific and Production Association (Lavochkin Association)
24, Leningradskaya str., Khimki, Moscow reg., 141400, Russia
: Space Mechanism and Components, 1042
: Space System for Controlling Emergency Situations on the Earth, 1053
: Analysis of Prospects for Geostationary Communication Satellites, 1068
: Soft Landing System, 1068-2
: Soft Landing System, 1265
: Rover with Video-Navigation System, 1374
: Homochirality as Extraterrestial Life Indicator, 1375
: Orbital Ionization-neutron Calorimeter, 1469
: Inflatable Re-entry Technology, 1578
: Space Remote Energy Transmission, 2010
: Samarium Sulfide Semiconductors, 2513
: Mars Lander, 2836
: In-Orbit Experiment with Inflatable Solar Generator, 2868
: Welding with Two Heating Sources, 3337
: Controlled laser thermocracking of dielectrics, 3594
: Heat Pipes for Pedestrian Municipal Objects, 3678
: Hybrid Laser Lighting Welding, 3742
: Moon Explorations, 3871
: Thermal Diagnostics of Aerospace Structures, 3912
: Laser Cutting of Triplex
The Lavochkin Association is one of the leading Russian enterprises in the development and practical use of unmanned means of exploration of celestial bodies and space. Spacecraft developed by the Lavochkin Association are proven pioneers in their field. Lavochkin spacecraft were the first to execute soft landings on the Moon, Mars and Venus and the first to conduct automated lunar soil sampling and sample delivery to Earth. The LUNOKHOD Lunar Rover was the first craft to perform multi-kilometer travel along the lunar surface and the VEGA spacecraft executed combined investigations of Venus and Halley’s Comet.
Specific Tech Areas
Each spacecraft represents a very complicated mechanism, and the reliable operation of its every unit is essential for execution of the whole program. Planetary Rovers are spacecraft, designed to function in the specific planetary conditions.
Determining factors of the space environment are as follows:
- high vacuum;
- large range of temperature variation;
These factors affect materials, change their surface properties and, as a consequence, change the conditions of interaction of friction pairs in spacecraft mechanical units.In fact, all spacecraft are equipped with friction units, including hinges, valves, and gears.
One can distinguish the main processes in materials in a vacuum by the following:
1) loss of mass (desorption of adsorbed gas films from the material surface; diffusion and desorption of gases solved in material; material sublimation);
2) adhesion of contacting materials;
3) destruction of multi-component materials.
The concentration of gaseous particles in space reaches 1 in cm3 and lower and, consequently, the dominant aspect of this environment is its capability to absorb (or “pump”, to use the correct term for vacuum technology) an unlimited quantity of gases and vapor, which can be released from spacecraft in space. It should be noted that the mass loss rate is the most characteristic effect of a vacuum on spacecraft elements of units and materials. Moreover, due to the above processes, the surfaces are cleaned from absorbed matters (water, hydrocarbons, etc.). The interfacing surfaces become unevenly clean and, as a result, binding bridges form in friction pairs and cold welding (adhesion) takes place.
An ultra-high vacuum is one of the most important factors of the lunar ambient environment. According to modern knowledge, the value of a vacuum on the lunar surface reaches 1E-8 to 1E-14 Pa.
Due to the absence of protective gaseous and water envelopes, the average temperature on the Moon’s surface varies from 125 °C by day to -175 °C by night. The average gradient of the temperature variation is not so high and is equal to approximately 9 °C per hour. However, during an eclipse it can reach 200 °C per hour. By day spacecraft are subjected to the thermal effect of the Sun and of soil and rock, heated by it.
When working on the lunar surface, it is probable that friction mechanisms may be polluted with dust.
The Martian atmosphere is extremely rarefied; the average pressure level of the Martian surface is 6.1 bars, i.e. 160 times lower than at sea level on Earth. In the lowland atmospheric pressure can reach 10 mbars, and on mountains - less than 1 mbar.
The atmosphere is 95 % composed of CO2.
Mars is distinguished by the seasonal variation of its wind. Usually the wind speed near the surface does not exceed 10 m/sec, but processes, related to seasonal variations, lead to development of stronger winds, reaching 40 - 70 m/sec, and sometimes more than 100 m/sec. Such winds and tornadoes pick up small particles from the surface of the soil. The dust particles (up to 200 m in size), moving with such great speed, will produce an essentially erosive action and can penetrate friction mechanisms.
Usually the minimum temperature on the surface does not drop to lower than -125 °C; average seasonal temperature is -60 °C and the maximum summer temperature in the tropical areas can reach +25 °C. Moreover, the soil temperature is about 10 - 15 degrees higher, than that of the atmosphere.
Spacecraft mechanical units (and spacecraft as a whole) must maintain their serviceability after the effect of great mechanical loads, relative to spacecraft ascent into the Earth’s orbit and when landing on planet surfaces.
A considerable time passes from the moment spacecraft manufacture commences to the time of the launch thereof; the spacecraft subsystems and units are usually under normal atmospheric conditions during this period. Nevertheless, certain pieces and assembled units are subjected to the effects of atmospheric air, different temperatures and humidity.
During the first phase of space exploration most of the equipment, units and boxes were installed inside the spacecraft pressurized compartment, but now most of these items are mounted directly in a vacuum.
Most investigations and experiments, concerning selection of materials, lubricants and test conditions during the ground testing, were carried out during preparation for the third phase of lunar exploration (1970 - 1975) by LUNA 16 - 24 Spacecraft, delivery by LUNOKHOD 1, 2 Rovers of lunar soil samples to Earth, their landing on the lunar surface and their operation there.
These investigations were based on the testing of special experimental reduction gear, intended for the investigation of elements of LUNOKHOD-1 apparatus. This reduction gear represents two pairs of cogwheels, loaded with circulated power. In this case motor energy is spent only on restoring losses in the castellation and bearings. This experimental unit was installed in the LUNA-12 Lunar
Satellite and also tested in vacuum chambers.Comparison of test results facilitated the elaboration of main requirements to thermal/vacuum tests of the spacecraft mechanical units in ground-based conditions.
These experiments and investigations helped to develop a number of mechanisms for the LUNOKHOD-1 Lunar Rover.
LUNOKHOD is a vehicle, automatically controlled from the Earth and consisting of two main parts: a pressurized equipment container and a self-driven mobility system.
The gear was designed to provide 4 months of motion on the lunar surface for the LUNOKHOD mobile scientific vehicle. Structurally it is included in the composition of the vehicle mobility system.
The electromechanical gear includes an electric drive motor, reduction gear, mechanical brake with electromagnetic control, temperature sensor, R.P.M. counter, electric connector and cable wiring. A DC electric motor is used in the electromechanical gear.
To enable the motor to operate in vacuum conditions, its brushes are fabricated of a special material.
The driving reduction gear of the motor/wheel is a three epicyclic series connected in serial. Planet pinion cages are installed without rigid fixation in a radial direction (a “floating” epicyclic series).
The selected kinematics of the reduction gear ensure high efficiency (no lower than 0.85, taking into account all losses). Sun wheels and satellites are fabricated of a special self-lubricating material, thermally treated to high hardness, to allow an increase in resistance to wear of the cogs’ working surfaces. The lubricant ВНИИ НП-249 is applied to all movable connections.
The special end plate/bellows seal of the gear, in which the spring presses the bellows against the seal holder, thus blocking the penetration of gas particles from the inner cavity, where the planetary gear and driving motor are installed, to the exterior cavity, was developed for use in LUNOKHODs 1 and 2.
The actuator of the LUNOKHOD’s High Gain Antenna was mounted outside the equipment compartment and provided the antenna pointing on azimuth and angle of site. The control method on the azimuth and angle of site was accepted basing on condition of maximal simplifying of the Rover’s guidance & control on the lunar surface.
The actuator includes two DC brushless motors with nominal power of 10W each. One motor is in the kinematic circuit of actuation on the angle of site, the other one - for the azimuth circuit.
This actuator also includes the following items:
- cogwheel and worm drives;
- tapped gears of end switches;
- end-plate /bellows seal for rotating connections (identical to that of the wheel gear);
- labyrinth seals.
It should be noted that, in order to provide the mechanism’s serviceability, special cases were installed in the gear’s inner cavities; these cases were filled with ЦИАТИМ-221 lubricant and, together with sealing devices, they provide inner pressure of no less than 1E-2 Pa (at ambient pressureof 1E-10 Pa and temperature difference from 120 °C to minus 140 °C).
In 40 years of practical cosmonautics considerable success in the development of electronics, automation, material sciences and engineering has considerably changed the architecture and composition of spacecraft. All electrical units became essentially «lightweight», their power consumption and heat dissipation decreased, and their qualitative level ameliorated. For instance, the Planetary Rover now with scientific objectives identical to those of LUNOKHOD-1, weighs 80 - 120 kg (7 - 10 times lower).
The Lavochkin Association now develops Mars Rovers, 50 - 100 kg in mass, and with a great number of gears and hinges.
The gear is intended for provision of motion and operation of Rover mechanisms of the mobility system for the MARS-2003 advanced project.
The gear includes a five-series epicyclic gear with a total reduction ration of i = 3125 and an inductor brushless electric motor. The gear’s output axle has a labyrinth seal.
To achieve a long life span, steady-state and dynamic strength of the actuator, high alloy stainless steel is used, which has a hardness of HRS 30 - 36. Sun wheels, as the most loaded, are fabricated of special maraging steel with HRC 45.
At the manufacturing stage, the gear is subjected to running with low grain (1 - 3 m) paste, that allows one to achieve a value of efficiency of no worse than 0.85.
The Lavochkin Association has great expertise in the development of spacecraft, whose reliability is confirmed by long-term operation in the conditions of space flight.
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Description of Research Activity