rus
Issue #2/2014
S.Krat, V.Khristich, A.Sharov, M.Shlyakhtin, A.Filatov
Large Solar Radiation Simulators for Thermal Vacuum Tests of Non-Container Spacecraft
Large Solar Radiation Simulators for Thermal Vacuum Tests of Non-Container Spacecraft
Article provides an overview of solar radiation simulators based on the principle of summation of light streams from an array of gas discharge lamps. Current trends of stands for the ground experimental testing of spacecraft using solar radiation simulators are analyzed as well.
Теги: ground tests solar radiation simulators space vehicles имитаторы солнечного излучения космические аппараты наземные испытания
At the present stage of development of modern Russian spacecraft it is need to improve their performance and increase the active lifetime (ALT) up to 10–15 years.
This significant ALT increasing is achieved by creating a fundamentally new generation of SC based on the non-container devices with passive thermal control system (PTCS). These requirements are due to the formation and mutual integration of new technologies related to the production, processing and exploitation of spacecraft. At present spacecraft created using honeycomb panels with integrated heat pipes, special radiation surfaces and plenty of heaters.
Development of new generation USC requires research into the mechanisms of influence of the space environment on spacecraft systems. Without a corresponding very careful consideration and taking appropriate measures to protect USC from destructive space environment factors can lead to catastrophic failures in the operation of the modern USC [1].
SRS is one of the most important element of the thermal vacuum SGT. At present there are four large SRS are operated in Russia. In conjunction with the vacuum facilities VK 600/300 from the 1970s operated simulators IP-500 in R&D RSC Corp. and TsSKB Progress. Vacuum M.F.Reshetnev Information Satellite Systems OJSC operates a vacuum facility TBK-120 with SRS which produces the light spot sized of 2×2 m. Apart of it the SRS ISI GVU-600, cooperated with the vacuum facility GVU-600 and producing the light spot sized of 4×4 m, was commissioned in 2011. Both last mentioned SRS will be considered below.
SRS TBK-120 and SRS GVU-600
Historically, most simulators built in the Soviet Union, were planned for the work with lamps DKsRM-55000, which were in the jargon of the industry known as "Rabinovich lamp" by inventor’s name. This lamp had an electric power of 55 kW, the light flux power at the output was 15 kW. The lamp included a built in parabolic reflector, which formed parallel beam diameter of about 200 mm. The lamp provided the dual-circuit cooling. The first circuit provided cooling of the electrodes, and the second one with distilled water, provided the cooling of the lamp’s output quartz window. For this reason the emission spectrum was completely absent the UV component in the wavelength range 200–380 nm, which reduced reproduction accuracy of the factors space.
In particular above mentioned SRS TBK-120 worked with such lamps as well as several sub-systems of the SRS IS-500. By 2007, the industry was in a situation where the lamp-DKsRM 55,000 have already been taken out of production, and lamps stock in warehouses ended. As a result, there was a risk of failure of current thermal vacuum tests. OJSC ISS was decided to upgrade the SRS TBA-120 and adaptation IS scheme for advanced series-produced lamps. Together with specialists VOLO comp. we developed the IS scheme of the light fluxes summation from an array of discharge lamps.
As a result of modernization, SRS was equipped with two new light panels, each of which included seven lamps of up to 10 kW. The optical design of the new light panels was developed to minimize original design changes and maximize efficiency at the same time. Using this new light panel SRS produces at the tested object the light spot size of 2×2 m with a range of power density of 400–2880 W/m2. The new lamps require air cooling only and have a resource over 500 h.
Figures 3 and 4 shows a view of one of the two light panels that included into the SRS TBA-120.
Successful experience of operating 10 kW lamps SRS TBK-120 for several years was taken into account during designing a new SRS for horizontal vacuum installation GVU-600.
The simulator would have the following characteristics:
light spot size 4×4 m expandable to 5×5 m;
the power density inside of spot in the range of 400–1500 W/m2;
irregularity under 10%;
spectral range 200–2500 nm.
SRS includes the next sub-systems:
lighting system of 4 light panels;
input blocks mounted on the recoil cover of the vacuum facility;
mirror collimator mounted inside the vacuum facility;
power supply system;
automatic control system;
system for measuring the radiation parameters.
SRS was designed and manufactured by VOLO Comp., St. Petersburg, in cooperation with Tomsk Polytechnic University (automatic control system), LLC "Merlin", Moscow (power supply system), FSUE Institute of vacuum technology im.S.A.Vekshinsky, Moscow (system parameters measurement of radiation).
SRS GVU-600 was designed to install into existed vacuum facility, which led to a number of non-standard design solutions. For example, the lighting system with 4 light panels has been designed so as to allow its quick mounting/dismounting indoor GVU-600. This allows to store the lighting system in other areas of the company, freeing up extra space during tests that do not require simulation of solar radiation. Mirrired collimator also allows quick assembly/disassembly and storage of its components in 6-upgraded 20 foot containers.
SRS GVU-600 was built in a fairly short time by the standards of the project: the design was initiated in early 2010, and in autumn 2011 simulator was commissioned.
Illuminating system of the SRS GVU-600 based on the same principles of light fluxes summation from the lamp array like TBK-120. Illuminating system includes of 4 light panels and each of them containes of 10 lamps by 8 kW each.
Perspective SRS
As noted earlier in this article, the progress on the USC stimulates the development of SGT for their experimental improvement. Development of stand base with SRS due to several aspects. First, is the modernization and maintenance in operational condition of existing facilities. Analysis of the status of IS-500 SRS shows that despite more than 40 years of service life they are in good condition and require only light panels modernization with replacement of water-cooled lamps for air-cooled lamps with significantly longer operating life, as well as restoration mirror coatings. Imitators IC-500 has an unique illuminating scheme, which allows to form on the tested objects areas with different power densities. This is extremely important for thermal vacuum tests of USC, requiring produce different levels of light output at different parts of the tested object to simulate shading effects during space flight.
By the other side is very actual to create large SRS having exposure area of 25–40 m2 and possibility to rotate test spacecraft during testing around 3 axes. An example of such a facility is a Large Space Simulator, operated in the test center ESTEC European Space Agency ESA.
The main distinguishing feature of this simulator is a high volume of luminous flux uniformity within the scope of the vacuum unit. This allows to investigate the thermal regimes of SC during its rotation around 3 axes with playing all possible positions of the SC at the orbit relative to the Sun. High bulk uniformity of luminous flux can be obtained under the condition that all light directed at the test object is radiated by a single light panel. However, it demands to use of high powered water-cooled 25–30 kW lamps. For example, mentioned before SRS of ESA has the next specs:
light spot diameter 6 m;
power density up to 2800 W/m2 in the 6 m light spot diameter;
power density up to 14400 W/m2 in the 2.5 m light spot diameter (unparallel light bundle);
paralellism ±1.5°;
uniformity on the plane ±5%;
uniformity in the volume ±10%;
light plate: 19 lamps of 25 kW.
Conclusions
Service life of SC currently determines its commercial viability. This value depends critically on the quality of SC experimental testing ground and fidelity space factors, which include solar radiation. This determines the importance of the SGT development, equipped with SRS.
Considering that the vast majority of SC will be untightened with specific requirements to their thermal vacuum working out, it is impossible to develop a line of middle class SRS with lighting areas from 2 to 10 m2 and based on 3–5 kW lamps, as well as the direction of large SRS with lighting areas 20–50 m2, based on high-power water-cooled lamps of 25–30 kW.
This significant ALT increasing is achieved by creating a fundamentally new generation of SC based on the non-container devices with passive thermal control system (PTCS). These requirements are due to the formation and mutual integration of new technologies related to the production, processing and exploitation of spacecraft. At present spacecraft created using honeycomb panels with integrated heat pipes, special radiation surfaces and plenty of heaters.
Development of new generation USC requires research into the mechanisms of influence of the space environment on spacecraft systems. Without a corresponding very careful consideration and taking appropriate measures to protect USC from destructive space environment factors can lead to catastrophic failures in the operation of the modern USC [1].
SRS is one of the most important element of the thermal vacuum SGT. At present there are four large SRS are operated in Russia. In conjunction with the vacuum facilities VK 600/300 from the 1970s operated simulators IP-500 in R&D RSC Corp. and TsSKB Progress. Vacuum M.F.Reshetnev Information Satellite Systems OJSC operates a vacuum facility TBK-120 with SRS which produces the light spot sized of 2×2 m. Apart of it the SRS ISI GVU-600, cooperated with the vacuum facility GVU-600 and producing the light spot sized of 4×4 m, was commissioned in 2011. Both last mentioned SRS will be considered below.
SRS TBK-120 and SRS GVU-600
Historically, most simulators built in the Soviet Union, were planned for the work with lamps DKsRM-55000, which were in the jargon of the industry known as "Rabinovich lamp" by inventor’s name. This lamp had an electric power of 55 kW, the light flux power at the output was 15 kW. The lamp included a built in parabolic reflector, which formed parallel beam diameter of about 200 mm. The lamp provided the dual-circuit cooling. The first circuit provided cooling of the electrodes, and the second one with distilled water, provided the cooling of the lamp’s output quartz window. For this reason the emission spectrum was completely absent the UV component in the wavelength range 200–380 nm, which reduced reproduction accuracy of the factors space.
In particular above mentioned SRS TBK-120 worked with such lamps as well as several sub-systems of the SRS IS-500. By 2007, the industry was in a situation where the lamp-DKsRM 55,000 have already been taken out of production, and lamps stock in warehouses ended. As a result, there was a risk of failure of current thermal vacuum tests. OJSC ISS was decided to upgrade the SRS TBA-120 and adaptation IS scheme for advanced series-produced lamps. Together with specialists VOLO comp. we developed the IS scheme of the light fluxes summation from an array of discharge lamps.
As a result of modernization, SRS was equipped with two new light panels, each of which included seven lamps of up to 10 kW. The optical design of the new light panels was developed to minimize original design changes and maximize efficiency at the same time. Using this new light panel SRS produces at the tested object the light spot size of 2×2 m with a range of power density of 400–2880 W/m2. The new lamps require air cooling only and have a resource over 500 h.
Figures 3 and 4 shows a view of one of the two light panels that included into the SRS TBA-120.
Successful experience of operating 10 kW lamps SRS TBK-120 for several years was taken into account during designing a new SRS for horizontal vacuum installation GVU-600.
The simulator would have the following characteristics:
light spot size 4×4 m expandable to 5×5 m;
the power density inside of spot in the range of 400–1500 W/m2;
irregularity under 10%;
spectral range 200–2500 nm.
SRS includes the next sub-systems:
lighting system of 4 light panels;
input blocks mounted on the recoil cover of the vacuum facility;
mirror collimator mounted inside the vacuum facility;
power supply system;
automatic control system;
system for measuring the radiation parameters.
SRS was designed and manufactured by VOLO Comp., St. Petersburg, in cooperation with Tomsk Polytechnic University (automatic control system), LLC "Merlin", Moscow (power supply system), FSUE Institute of vacuum technology im.S.A.Vekshinsky, Moscow (system parameters measurement of radiation).
SRS GVU-600 was designed to install into existed vacuum facility, which led to a number of non-standard design solutions. For example, the lighting system with 4 light panels has been designed so as to allow its quick mounting/dismounting indoor GVU-600. This allows to store the lighting system in other areas of the company, freeing up extra space during tests that do not require simulation of solar radiation. Mirrired collimator also allows quick assembly/disassembly and storage of its components in 6-upgraded 20 foot containers.
SRS GVU-600 was built in a fairly short time by the standards of the project: the design was initiated in early 2010, and in autumn 2011 simulator was commissioned.
Illuminating system of the SRS GVU-600 based on the same principles of light fluxes summation from the lamp array like TBK-120. Illuminating system includes of 4 light panels and each of them containes of 10 lamps by 8 kW each.
Perspective SRS
As noted earlier in this article, the progress on the USC stimulates the development of SGT for their experimental improvement. Development of stand base with SRS due to several aspects. First, is the modernization and maintenance in operational condition of existing facilities. Analysis of the status of IS-500 SRS shows that despite more than 40 years of service life they are in good condition and require only light panels modernization with replacement of water-cooled lamps for air-cooled lamps with significantly longer operating life, as well as restoration mirror coatings. Imitators IC-500 has an unique illuminating scheme, which allows to form on the tested objects areas with different power densities. This is extremely important for thermal vacuum tests of USC, requiring produce different levels of light output at different parts of the tested object to simulate shading effects during space flight.
By the other side is very actual to create large SRS having exposure area of 25–40 m2 and possibility to rotate test spacecraft during testing around 3 axes. An example of such a facility is a Large Space Simulator, operated in the test center ESTEC European Space Agency ESA.
The main distinguishing feature of this simulator is a high volume of luminous flux uniformity within the scope of the vacuum unit. This allows to investigate the thermal regimes of SC during its rotation around 3 axes with playing all possible positions of the SC at the orbit relative to the Sun. High bulk uniformity of luminous flux can be obtained under the condition that all light directed at the test object is radiated by a single light panel. However, it demands to use of high powered water-cooled 25–30 kW lamps. For example, mentioned before SRS of ESA has the next specs:
light spot diameter 6 m;
power density up to 2800 W/m2 in the 6 m light spot diameter;
power density up to 14400 W/m2 in the 2.5 m light spot diameter (unparallel light bundle);
paralellism ±1.5°;
uniformity on the plane ±5%;
uniformity in the volume ±10%;
light plate: 19 lamps of 25 kW.
Conclusions
Service life of SC currently determines its commercial viability. This value depends critically on the quality of SC experimental testing ground and fidelity space factors, which include solar radiation. This determines the importance of the SGT development, equipped with SRS.
Considering that the vast majority of SC will be untightened with specific requirements to their thermal vacuum working out, it is impossible to develop a line of middle class SRS with lighting areas from 2 to 10 m2 and based on 3–5 kW lamps, as well as the direction of large SRS with lighting areas 20–50 m2, based on high-power water-cooled lamps of 25–30 kW.
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