SJ-10 Recoverable Satellite for Space Microgravity Experiments*

HU Wenrui KANG Qi DUAN Enkui LONG Mian

SJ-10 Recoverable Satellite for Space Microgravity Experiments*

HU Wenrui1,2KANG Qi1,2DUAN Enkui3LONG Mian1,2

1 (100190)2(100049)3(100101)

SJ-10 is a recoverable scientific experiment satellite specially for the space experiments of microgravity physics science and space life science. This mission was officially started on 31 December 2012, and the satellite was launched on 6 April 2016. This paper introduces briefly the SJ-10 mission, the progress of SJ-10 engineering and the project constitution of sciences experiments onboard SJ-10. The purpose of this mission is to discover the law of matter movement and the rule of life activity that cannot be discovered on the ground due to the existence of gravity, and to know the acting mechanism on organisms by the complex radiation of space that cannot be simulated on the ground.

Microgravity physics, Space life science, Space microgravity experiments, Recoverable satellite

1 Introduction

Shijian-10 (SJ-10) satellite is the second mission of the Strategic Priority Research Program (First-Stage) on Space Science, the Chinese Academy of Sciences (CAS). On 6 April 2016, at 01:38:04 BJT, Long March 2D was launched at Jiuquan Satellite Launch Center (Figure1). And 559 seconds later, SJ-10 rec--overable scientific experiment satellite was success--fully sent into the near-circular orbit at the height of about 250 km. This is the 24th successful launch of China’s recoverable satellite. In the past, we also carried out many microgravity science experiments with China’s recoverable satellites.

SJ-10 is the recoverable scientific experiment satellite specially for the space experiments of mic-rogravity physics science and space life science. This mission was officially started on 31 December 2012. With the long period time in the microgravity environment and the radiation condition in space pr-ovided by SJ-10, a number of scientific and technological experimental studies on the law of matter movement and the rule of life activity were carried out through remote scientific and technological methods and sample recovery analytic techniques of space experiments. These space experiments focused on some fundamental and hot issues in microgravity physics science and space life science, especially for the verification of the original physical model, the utilization of spacecraft technology and space environment, and the important applications and theoretical breakthrough in space science in the future. The purpose of this mission is to discover the law of matter movement and the rule of life activity that cannot be discovered on the ground due to the existence of gravity, and to know the acting mechanism on organisms by the complex radiation of space that cannot be simulated on the ground.

Fig.1 SJ-10 satellite was launched successfully at Jiuquan Satellite Launch Center

Fig.2 Organization structure of SJ-10 engineering mission

SJ-10 engineering includes six systems: Satellite, Rocket, Launching, Control and Recover, Ground Support, and Scientific Applications, as shown in Figure2. The National Space Science Center of CAS is the general engineering management organization, the Institute of Mechanics of CAS is in charge of the scientific application system of the mission. Their tasks include overall organization, coordination, operation, and management of the scientific research work, as well as completing the planning and guiding the implementation of scientific experi-ments,

2 Introduction on SJ-10 Engineering

There are 28 research topics on microgravity physics and space life science aboard the SJ-10 satellite, and they are integrated into 19 projects of payloads. Among them, there are 10 payloads about microgravity physics sciences, and the research fields include 3 subjects: microgravity fluid physics (A1), microgravity combustion science (A2), and space material science (A3). The satellite fully inherited China’s recoverable satellite technology, and it is divided into the orbit capsule and the reentry capsule. All the 8 projects in the orbit capsule are about experiments of microgravity physics sciences, including 5 experimental payloads of fluid physics) and 3 experimental payloads of combustion, which all do not require sample recovery. In the reentry capsule, there are two experimental payloads about microgravity physics sciences: (i) synthetic furnace of multifunctional material in space; (ii) SCCO experimental payload of complex fluid, and nine other experimental payloads are all for life science research. All experimental samples in the reentry capsule need to be analyzed in the ground laboratory after the recovery.

The research and development of the payload prototypes of SJ-10 were completed in September 2013. The development of engineering prototypes and flight prototypes was completed in December 2014 and January 2016 respectively. The total weight of the 10 experimental payloads of microgravity physics science is about 350 kg. Figure3 shows the debugging and testing site of scientific experiment payloads and the satellite of SJ-10.

On 6 April 2016, four hours after the satellite was launched into the orbit, the orbit capsule firstly started the research experiment of colloidal crystals, and then the experimental payloads in the orbit capsule carried out cycled rounds of scientific experiments in a serial operating mode. In the reentry capsule, the experiment of SCCO payload lasted for 270 h, and the melting experiment on synthetic furnace of multifunctional materials accumulated totally 208 h with 6 working positions switched in turn. The scientific experimental data from the sa-tellite were received by the three satellite ground stations of CAS at Miyun, Sanya and Kashi, and delivered to the integrated operating and control center of the ground support system at the National Space Science Center of CAS in Beijing in real time for primary processing; Then the first level data pac-kages were distributed to the scientific experiment operating center of scientific application systems at the Institute of Mechanics of CAS. Scientists interpreted and processed the space experimental data on line and adjusted space experimental parameters, operating mode, and plans according to the space experimental status. After 12 days in orbit, the reentry capsule separated from the orbit capsule and returned to Siziwangqi recovery area in Inner Mongolia, China. The payloads and samples were disassembled on-site and taken back to laboratories for post-processing. The orbit capsule continued to work 8 days in space to complete all the follow-up and expanded experiments.

3 Introduction to the Microgravity Physical Sciences Projects

The research on microgravity physical sciences depends heavily on advanced space technologies. It promotes the development of space science and applications. It fully demonstrates a country’s ability in science and technology. It is an important driven force for the development of science and technology in the world. Therefore, microgravity physical sciences naturally become the hot subject of research in the world (especially in power countries in spaceflight). In recent years, the International Space Station (ISS) has become the main platform for research on microgravity physical sciences internationally. NASA, ESA, JAXA and Roskosmos/RKA established many special experimental racks for the researchon microgravity physical sciences, and greatly improved the experimental platform in the space station to carry out studies on microgravity physical sciences. They are promoting the fast development of micro-gravity physical sciences at an unprecedented speed.

The study on microgravity physical sciences in China started in the late 1980s. Since then, more than ten batches of space experiments on microgravity physical sciences have been carried out mainly on Chine’s recoverable satellites and Shenzhou spaceships. Chinese scientists have obtained some valuable first- hand experiences in space research, which has laid a good foundation for the development of this subject. In recent years, microgravity science, as an important content in space science, has been deeply demonstrated and planned for a medium and long term by the Strategic Priority Research Program on Space Science of CAS and China Space Station Program. Among the pre-res-earch projects of the Strategic Priority Research Program on Space Science and the first batch of science projects of China Space Station Program, dozens of microgravity physical science projects have been supported.

Space experimental research on microgravity physical science in SJ-10 focuses on some frontier subjects in the field of microgravity science in the world,microgravity fluid physics, microgravity combustion science, and space material science[4,5]. It is based on the fact that, some important physical processes could be understood clearly only in the long period time in the microgravity environment of space, and the research could increase people’s knowledge of the laws of matter movement under the extreme condition of microgravity: the processes of convection, self-organizing and phase change, and the laws of heat and mass transfer; material ignition and combustion behavior, coal combustion mechanism under the microgravity condition; the growth and solidification processes of new material samples in the microgravity environment. It will improve and optimize engineering fluid and thermal power machinery as well as material processing technology on the ground and in space, obtain high-quality materials that are difficult to grow in the gravity field on the ground, and provide scientific basis and fundamental data for the safety of manned spacecraft in China and some major national requirements such as energy and carbon emission reduction,.

The project’s objectives of microgravity physical sciences are as follows.

(1) Microgravity fluid physics. To study the internal mechanisms, dynamic processes and instabilities of heat and mass transfer in the convection and phase change (evaporation and boiling), and discover new laws and verify independently developed physical models; to verify the such molecule gas-liquid separation theory of granular gas; using a typical colloid system to study the establishment and evolution processes of the ordered phase driven by pure entropy, the establishment of liquid crystalline phase and the self-assembly mechanism of metal nano-particles; to accurately measure the Soret coefficient of the samples including Chinese petroleum, and study the cross diffusion rule of the multi-com-ponent medium.

(2) Microgravity combustion science.To discover the laws of ignition, combustion, flame spread, flue gas precipitation, soot emission and smoke distribution of typical non-metallic materials and wire insulations under microgravity condition; and to reveal the laws of pyrolysis, ignition, combustion and pollutant generation of typical coal of China under microgravity condition. To provide theoretical basis and technical support for ground combustion and space safety by microgravity research results.

(3) Space material science. To discover the selective occupation law of dopant atoms, the morpho-genesis and evolution mechanisms of the alloy structure during the crystal growth process, and understand in depth the interface dynamics in the formation of materials from the melt and develop relative theories; to realize the mass transport pro-cess dominated by diffusion, and achieve a uniform and large scale semiconductor crystals, high-quality metal alloys and composite materials that are difficult to grow in the gravity field on the ground.

There are eleven space experiments on microgravity physical sciences.

4 Introduction to the Space Life Science Projects

The aforementioned projects attempt, from the view-point of space life science and biotechnology, to unravel the sensing and transduction mechanisms of various species under microgravity and space radiation and to develop the novel techniques in stem cell differentiation and embryonic development. Scientific issues are mainly focused on understanding the effect of space environment on the evolution of terrestrial life and the impact of space environment on the physiological homeostasis of organisms. Three specific aims are: (i) how do the terrestrial lives sense microgravity and/or space radiation signaling and what are the underlying transduction pathways; (ii) how do the organisms adapt themselves to the microgravity and/or space radiation environment; (iii) how are the microgravity and/or space radiation resources utilized to promote the perspective of space life science and the development of space biotechnology.

The outcomes of these projects would provide the fundamental understandings, propose new concepts, new ideas, and new methodology, and establish the integrated platforms in ground- or space-based studies for space life science and biotechnology. Expected results are to develop numerical simulation platforms and biologically-specific techniques and to further the understandings in sensation and transduction of microgravity and space radiation signaling for plant or animal cells or in tissue histogenesis.

4.1 Radiation Biology

The first project in this category, entitled “Molecular biology mechanism of space radiation mut-agenesis”, aims to (i) analyze the sequence infor-mation of genome methylation and transposon cha-nge caused by space radiation and explore the mol-ecular mechanisms of space radiation induced gen-omic instability; to (ii) study the proteomics profiles of model organisms caused by different radiation qualities, mine the molecular mechanisms of func-tional proteins, and to establish the biological sys-tems that evaluate radiation qualities. Plant and ani-mal model organisms are located at three distinct radiation environments inside the satellite. By mon-itoring three tissue equivalent detector devices, the space radiation parameters such as absorbed dose, absorbed dose rate, linear energy transfer value, and dose equivalent are detected. The biological materials irradiated by different kinds of particles that belong to the same satellite orbit are then harvested and recovered. System biology analyses such as genome epigenetic scanning and proteomic approaches are conducted to obtain information of biological changes under different radiation qualities and to correlate biological effects with different radiation parameters.

The second project entitled “Roles of space radiation on genomic DNA and its genetic effects”, attempts to elucidate the roles of space radiation on genomic DNA and its genetic effects in the real space environment in two aspects.

(1) Space radiation and genomic stability. Genomic stability of wild type and radiation-sensitive mouse cells and fruit flies is investigated in pre- and post-flight or at different time points during the spaceflight. Quantitative parameters of space radiation of the genome and its genetic effects are then obtained in the real space environment.

(2) Gene expression profiles and sensitive response genes to space radiation. Gene expression profiles are obtained from the above mouse cells and of fruit flies. Novel and sensitive biological molecules are identified as space radiation markers. This work provides novel information for developing evaluation methods for the risk factors and protection tools against space radiation.

The third project, entitled “Effects of space env-ironment on silkworm embryo development and me-chanism of mutation”, applies the selected silkworm embryos to pursue the following contents: (i) gene expression pattern of embryo under real space environment; (ii) proteome of silkworm embryo; (iii) mutation discovery and functional analysis; and (iv) embryo development and its characterization. Systematic approaches of the embryo development design and multiple sampling throughout the entire developmental stages are performed under space environment. Multiple platforms of gene expression, proteomics, and functional genomics, are employed to unravel the development characteristics of the silkworm in space and to find out the possible mutations through molecular approaches.

4.2 Gravitational Biology

The first project in this category, entitled “Biological effects and the signal transduction of microgravity stimulation in plants”, focuses on elucidating the effects of microgravity (weightless) environment in space on plant growth and the molecular mechanisms underlined in two specific aims: (i) whether plant’s sensation of the weight loss is also mediated by statoliths or other mechanisms; and (ii) whether there are any differences in transduction cascades between weight loss and gravitropic signaling. The hypothesis that the rigidity of the supporting tissue (., the cell wall in the plant) is regulated by mi-crogravity is tested to understand how space mi-crogravity affects the rigidity of plant cell wall and the metabolism of the plant cell wall, which in turn manipulates the growth of plants.

The second project, entitled “Biomechanics of mass transport of cell interactions under micrograv-ity”, attempts to (i) develop a novel space cell culture hardware consisting of the precisely controlled flow chamber and gas exchange system and to investigate the mass transport mechanisms in cell growth and cell-cell interactions under microgravity; and to (ii) distinguish the direct responses of cells from those indirect responsesthe varied mass transport conditions induced by gravity changes. New data sets on the metabolism, proliferation, apoptosis, differ-en-tiation, and cytoskeleton of osteoblasts and mesenchymal stem cells are collected under well-defined mass transfer. This work provides an insight into qua--ntifying the direct cellular responses in space, rev-ealing the effects of gravity on cell-cell interactions, elucidating the mechanisms of cell growth and diffe-rentiation in space, and overcoming the meth-odolo-gical bottlenecks of space cell biology studies.

The third project, entitled “Photoperiod-con--trolling flowering ofand rice in micro--gravity”, aims at deciphering how space microgravity regulates the transportation of flowering signals from leaf to shoot apex at a molecular level. Using transgenicand rice plants (ex-pressing FT or Hd 3a gene with the reporter genes GFP or GUS), living fluorescence imaging technique is developed to determine the induction of FT and Hd3a gene expression and floral initiation in shoot apex under long-day and short-day photoperiod condition under space microgravity or in normal gravity on the ground. This work sheds light on regulating mechanisms of photoperiod controlled flowering in bothand rice by microgravity.

4.3 Space Biotechnology

The first two projects, entitled “Three-dimensional cell culture of neural and hematopoietic stem cells in space”, share the same hardware in SJ-10 satellite. They aim to understand whether microgravity environment is suitable for the self-renewal and differentiation of hematopoietic or neural stem cells. Three-dimensional cell culture of hematopoietic stem cells and neural stem cells is conducted in space. With microscopic detection, image transmission, and gene/protein analysis through the recovered samples, the effects of microgravity on the self-renewal/diff-erentiation of two types of stem cells are tested to reveal the characteristics of growth and differentia-tion of these 3D cultured stem cells under microgravity. The outcomes are crucial in regenerative medicine for the treatment of various blood diseases and neural injury, respectively.

5 Conclusion

The China National Space Administration (CNSA) promotes the microgravity experiments onboard the Chinese recoverable satellite in the period of late last century and early this century. The Program of SJ-8 recoverable satellite launched on 9 September 2006 was organized jointly by CNSA and the Chinese Academy of Sciences (CAS). The recoverable capsule was used for the breeding experiments, and the unrecoverable capsule was used for microgravity exp-eriments which scientific results were summarized in Ref.[1]. The SJ-10 Mission was formally organized and then determines by CNSA in May 2006. Unfortunately, the engineering phase was stopped at the beginning due to the reform of CNSA, and then the missions of scientific satellite were moved from CNSA to CAS in 2011. The CAS restarted the demonstration phase at the end of 2012, and the engineering phase since the beginning of 2013. The introduction was published for the scientific program in Ref.[2], and for the experiments on the grand in Ref.[3].

A grant was supported jointly by the CAS and National Natural Science Foundation for research of space experiments, and the experimental results were summarized in two books published respectively by Science Press (Beijing) and Springer[4,5].

Acknowledgements The authors are grateful for all the individuals and institutions to implement the SJ-10 mission. They are (but not limited to) Prof. YIN Hejun and Prof. XIANGLI Bin as Chief of the mission, Prof. WU Ji as Acting Chief of the mission, Prof. TANG Bochang as the Chief Designer of the mission, Prof. MENG Xin as the Deputy Chief of mission; Prof. HUANG Chengguang as the Chief Commander of scientific application system; Prof. ZHANG Xiaohui, ZHAO Huiguang, QIU Jiawen, and XUE Changbin as the Director of SJ-10 engineer, satellite, and payload. The authors also acknowledge all the colleagues, experts, engineers, administrators, and participants from the six systems of Satellite, Rocket, Launching, Control and Recover, Ground Support, and Scientific Applications for the SJ-10 satellite mission. We are also particularly grateful to our scientist/payload teams.

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[4] HU W R, KANG Q. Physical Science under Microgravity: Experiments on Board the SJ-10 Recoverable Satellite [M]. Beijing: Science Press and Springer, 2019

[5] Duan E K, Long M. Life Science in Space: Experiments on Board the SJ-10 Recoverable Satellite [M]. Beijing: Science Press and Springer, 2019

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HU Wenrui, KANG Qi, DUAN Enkui, LONG Mian. SJ-10 Recoverable Satellite for Space Microgravity Experiments., 2020, 40(5): 648-654. DOI:10.11728/cjss2020.05.646

* Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA04020000) and United Funding from National Natural Science Foundation of China and Chinese Academy of Sciences

March 6, 2020

E-mail: wrhu@imech.ac.cn