Controlling Micro Satellites at Comfortable Temperatures
Tsuyoshi Totani , Associate Professor
Faculty of Engineering/ Graduate School of Engineering (School of Engineering, Department of Mechanical and Intelligent System Engineering, Mechanical Systems Course)
High school : Chiba Prefectural Funabashi High School
Academic background : Doctorate from Hokkaido University
- Research areas
- Space engineering
- Research keywords
- micro satellites, thermal control
What are you aiming to achieve?
My goal is to control the temperature of Micro-Satellites so that they can reliably operate in outer space.
Micro-satellites are defined as satellites that measure a maximum of 50 x 50 x 50 cm, and weigh no more than 50kg. Unless it is properly controlled, the temperature of a satellite in low earth orbit can reach a minimum of -150°C and a maximum of +100°C. It is not only humans who would suffer in these high and low temperature environments; machinery will also not work properly. In order for a satellite to operate correctly, temperature control is extremely important. Controlling the temperature is referred to as thermal control.
What do you think of when someone says “a device to regulate temperature”? In space, since there is none of the air that we have on earth, we cannot use air conditioning or other thermal control devices that use air. In addition, micro-satellites are extremely small, and only have minimal power generation capacity, so they cannot use the sort of thermal control devices that are available to large-scale satellites. Thermal control of micro-satellites requires the development of thermal control technologies that are optimized for miniaturization.
Figure 1 is a photograph of the ultra-compact HIT-SAT satellite. It was launched on 23 September 2006 from the Kagoshima Prefectural Space Observatory, using M-V Rocket No. 7, and until it reentered and burned up in the Earth’s atmosphere on 18 Jun 2008, it was in orbit for 1 year and 10 months, transmitting back temperature, magnetism and positioning data, among other information.
Fig. 1 Micro Satellite, HIT-SAT
Fig. 2 Ultra-compact spacecraft, UNITEC-1
The satellite was built by a collaborative team of people from Hokkaido Institute of Technology, Hokkaido University, and various small and medium-sized enterprises around Hokkaido, and I was responsible for its thermal control and structural aspects.
Figure 2 shows the ultra-compact spacecraft UNITEC-1. It was launched from Tanegashima Space Center in Kagoshima Prefecture on 23 May 2010, aboard H-IIA Rocket No. 17, and as of 10 September 2010 it was traveling towards Venus. We were able to communicate with UNITEC-1 the first day after launch, but communication has since been lost. This is the first spacecraft, other than one operated by the National Space Agency, in which communication has been possible from 300,000 km away (roughly the orbit of the moon). This craft was built as a UNISEC (University Space Engineering Consortium) initiative, with 22 universities and vocational colleges around Japan taking part in its construction. I was responsible for its thermal control system.
What sort of equipment are you using to do what type of experiments?
We used manual calculations and computers to examine the temperature of HIT-SAT and UNITEC-1 while in space. Our initial thermal design stage calculations were manual, and we used computers when we reached the detailed design stage. The temperature analysis software we use is Thermal Desktop/SINDA/Fluint. Figure 3 shows the internal temperature distribution analysis for UNITEC-1 using Thermal Desktop/SINDA/Fluint. Figure 4 shows UNITEC-1 being fitted to the H-IIA rocket at the Japan Aerospace Exploration Agency (JAXA) Tanegashima Space Center. The person on the left in the white coveralls is me. We wear white to prevent any dirt being transferred to the satellite or the rocket if our hands, arms, hair, clothing etc.
Fig. 3 The internal temperature distribution for UNITEC-1
Fig. 4 UNITEC-1 being fitted to the rocket
What are you aiming for next?
Compact satellites are being actively developed throughout the world. Recently, some compact satellites have come into being that rival large-scale satellites in terms of function. I would like to build micro-satellites that are even smaller than compact satellites, with functionality that would rival large-scale satellites. This is because using micro satellites allows the complex testing required prior to launch to be simplified, and lowers the cost of the satellite. In addition, I would like to use my field of specialization, thermal control, to develop thermal control materials suitable for use in micro-satellites. Specifically, a high-performance heat storage material that would absorb excess heat from inside the satellite and then release it when little heat is being generated.
(1) Rei Kawashima, The Story of CubeSat, X-Knowledge (2005)