Thermo-vacuum Chamber Research Articles

Design and manufacture of CubeSat-type nanosatellite thermal subsystem

This work presents the design and validation of a thermal subsystem for a 1U CubeSat-type nanosatellite. The design encompasses two stages: regulating the satellite’s temperature range through implementing passive control based on multilayer coatings and an electronic board capable of measuring the internal surface temperature of each of the satellite’s six faces. Validation is conducted through tests performed in a theoretical thermo vacuum chamber that provides a controlled environment, simulating the thermal conditions to which the satellite will be exposed once in orbit. The data collected by the sensors on the electronic board are encapsulated and transmitted wirelessly in real-time to an Earth station, where they are processed and displayed through a graphical interface. This setup allows for assessing the effectiveness of the implemented passive control.

Analysis of S-Parameters for RF Coaxial Cables at Different Environmental Conditions

RF coaxial cables are essential components in radio frequency and microwave systems. RF coaxial cables are necessary for the test and measurement systems. In spacecraft (TTC & Payload subsystem) testing, RF coaxial cables are used to uplink the signal from signal sources to spacecraft and receive the signal from spacecraft to measuring equipment. The performance of the RF coaxial cable can affect the test results of the spacecraft. The primary performance parameter for coaxial cable is the loss or attenuation. The losses are attributed to several factors and are present in all the RF Coaxial Cables. Environmental conditions affect coaxial cables, including temperature, pressure, moisture, dampness, etc. In this paper, an analysis of S-Parameters for RF coaxial cables at different environmental conditions is given. For this purpose, in the thermo vacuum chamber (TVAC), an experiment was conducted on N-type Polytetrafluoroethylene (PTFE) or Teflon coaxial cables during TVAC IST. A vector network analyzer and a computer with a LabVIEW-based application were used as a data acquisition system. All the processing of acquired data is done using the matrix laboratory (MATLAB) tool.

Analytical model of cryo-target in thermo-vacuum chamber

Nitrogen and Flelium based Cryo-Target (CT) systems are used for various experimental, industrial and testing applications in high vacuum chambers. Thermal performance of such systems depends upon a number of factors such as thermal exchange coefficient of coolant, various forms of heat losses, coolant properties, CT plate characteristics, externally applied heat loads etc. Therefore an analytical formulation is necessary in order to quantify the effect of such factors over thermal performance of CT system. In this paper analytical model is developed for flat plate CT system based on the positive root of heat balance quartic equation. Important analytical formulas related to characterization of thermal performance of CT systems are presented. This paper doesn't consider mixed phase flow in CT.

Design and realization of pure LN2supply system for cooling of black body targets to qualify meteorology payloads

Radiometric calibration of meteorological payloads like IMAGER and SOUNDER of INSAT-3D is mandatory to evaluate the instrument for its onboard performance at different temperatures. For such calibration, black body targets (BBTs) are required to be maintained at different constant temperatures within the calibration temperature range. During operation of BBTs, supply of pure LN2 at a constant pressure controlled within 20–25 PSI is essential to control temperature stability and reduce cooling time for each BBTs. simultaneously other subsystems of thermo vacuum chamber needed supply of pure LN2 in the range of 60 – 80 PSI. To handle this situation, various options were studied and based on the merits of each option, it was concluded to incorporate a phase separator system with its own pressure control system which will serve these competing requirements and provide required immunity to the BBT system from other system fluctuations.

Realization and thermal performance analysis of liquid nitrogen based 80 K Cryo-Target system for space simulation of meteorological payloads

Liquid nitrogen based Cryo-target system need to be used in thermo-vacuum chamber to simulate on-orbit environments of meteorological payloads. For a number of reasons it is essentially important to quantify the thermal performance of CT system prior to the actual tests of meteorological payloads. In this paper we present thermal performance of an efficient closed loop liquid nitrogen circulated blistered type embossed CT system inside thermovacuum chamber. We discuss important experiments, tests and their results that were carried out for the performance optimization of CT system. The optimized CT systems with space qualified conductive black painted aluminum honeycomb mounted on it were successfully used for Met payloads of INSAT 3D during TVP tests. The heat load handling capacity of closed loop flat plate CT system in thermo-vacuum chamber is analytically investigated. It is concluded that a closed loop CT system is better for low temperature and high external heat load requirements.

Open loop, auto reversing liquid nitrogen circulation thermal system for thermo vacuum chamber

In a thermo vacuum chamber, attaining and controlling low and high temperatures (-100 Deg. C to +120 Deg. C) is a very important task. This paper describes the development of "Open loop, auto reversing liquid nitrogen based thermal system". System specifications, features, open loop auto reversing system, liquid nitrogen flow paths etc. are discussed in this paper. This thermal system consists of solenoid operated cryogenic valves, double embossed thermal plate (shroud), heating elements, temperature sensors and PLC. Bulky items like blowers, heating chambers, liquid nitrogen injection chambers, huge pipe lines and valves were not used. This entire thermal system is very simple to operate and PLC based, fully auto system with auto tuned to given set temperatures. This system requires a very nominal amount of liquid nitrogen (approx. 80 liters / hour) while conducting thermo vacuum tests. This system was integrated to 1.2m dia thermo vacuum chamber, as a part of its augmentation, to conduct extreme temperature cycling tests on passive antenna reflectors of satellites.

The feasibility of doppler monitoring during EVA

During extravehicular activities (EVA) outside the spacecraft, astronauts have to work under reduced pressure in a space suit. This pressure reduction induces the risk of decompression sickness (DCS) by the formation of gas bubbles from excess nitrogen dissolved in the organism by breathing air at normal pressure. Under laboratory conditions the gas bubbles moving in the blood stream can be detected by the non-invasive ultrasonic Doppler method. By early detection of excessive bubble formation the development of DCS symptoms may be prevented by early application of preventative measures. The method could also be useful when applied in the space suit in order to compare the results of laboratory tests with operational results, because there is a discrepancy according to the DCS risk of laboratory experiments and actual EVA missions, where no symptoms have been reported yet. A prototype Doppler sensor has been developed and implemented in the Russian Orlan suit. To investigate the feasibility of this method under simulated space conditions, the equipment has been used in a series of 12 thermovacuum chamber tests with suited subjects, where intravenous bubble formation was compared to unsuited control experiments. In more than 50% of the suited tests good Doppler recordings could be achieved. In some cases with unsatisfying results the signal could be improved by breathholding. Although the results do not yet allow any conclusion about a possible difference between suited and unsuited subjects due to the small number of tests performed, the method proved its feasibility for use in EVA suits and should be further developed to enhance the safety of EVA procedures.

Automatic thermal control switches

Two complementary types of flexible connection thermal control switches are described in detail. Both preflight and flight test results that demonstrate the successful operation of the switch that is presumed to have the more general application are presented. Finally, a more extensive postflight thermo-vacuum test that reveals the natural proportional control feature of the tested switch is included. The flight test of the switch was per- formed in the Get-Away Special (GAS) container which was flown on the third Shuttle flight. HE subject thermal switches have been designed and manufactured and the switch that is expected to have the more general application has been tested in a thermo-vacuum chamber and in the first flight of the GAS package on the third Shuttle flight (STS-3). Both switches are described, and the performance of the tested switch is given in detail. In- cidental to the thermal switch development was the development of the flexible heat pipes which are used as heat carriers in the tested switch. Space limitations preclude a discussion of the heat pipe development in this paper. Purpose of the Switches The objective of the thermal switch development program was to provide an off-the-shelf thermal control device that will: 1) control heat flow between any two adjacent structural components that are otherwise isolated from each other; 2) accommodate limited motion between the two components; 3) require no electric power; 4) need no outside control; 5) provide the maximum amount of self-containe d control logic; and 6) provide a thermal transport capacity of 5 to 50 W. Description of the Switches There are two types of switches (switch A and switch B), each of which is operated by a pair of phase change motors that exerts the required mechanical force when their tem- peratures exceed the phase change temperature of the working fluid within/The actuating motor is a special form (sealed for vacuum operation) of the phase change capsule used to control the coolant temperature in automobile engines. The switches are shown diagrammatica;ly in Figs. 1 and 2. These sketches are simplified to clarify the principles involved. Switch B (Fig. 2) is closed at low (below phase change) temperature so that heat will flow from the source plate (to which the connector is attached) through the heat carriers to the payload item to be thermally controlled (to which the switch is attached). This switch opens when the payload item exceeds the motor fluid phase change temperature and heat promptly ceases to flow. A typical application would have the connector of switch B attached to a space radiator, and the switch proper attached to a piece of internal structure. The purpose would be to allow heat (e.g., solar energy) to flow into the internal structure only until that structure reached the phase change control temperature of the switch. This would provide a regulated heat input to the payload item.

Design of a thermal system for thermovacuum chambers

Abstract Design of the thermal system of two thermovacuum chambers, recently installed for the Indian Space Research Organization, is considered in detail. These Chambers operate in the temperature range 173 K–373 k. Two alternative systems, the gas-bypass flow system and the LN 2 injection system are analysed. Results are plotted in the form of generalized graphs. Specific results for the 2.0 m diameter thermovacuum chamber are also presented.