Prospect of Near-Space Exploration and Scientific Experiment Carrier Platform Demand

YANG Haoliang ,WANG Yingcheng ,WU Weiping ,YANG Yiqiang

1 Beijing CAS Aerospace Exploration Technology Co.Ltd.,Beijing 100176

2 Institute of Mechanics,CAS,Beijing 100190

Abstract:It is an important scientific research activity in China to carry out near-space exploration and scientific experiments via aerospace carriers.Early near-space exploration projects mainly used aircraft,balloons,sounding rockets and Earth satellites to carry out space environment exploration.With the development of China’s space science and technology,microgravity science has become a frontier science that has developed rapidly in the past 20 years.With the continuous progress of national space science and technology,the demand for near-space exploration and scientific experiments is increasing year by year.In the next 2 to 3 years,many advanced science activities and the associated technologies need to conduct corresponding experimental research work.This paper mainly analyzes the significance of scientific research and the ways to realize near-space exploration at home and abroad,and analyzes the directions and innovations that can be carried out in the future.

Key words:Near-space exploration,scientific experiment carrier platform,sounding rocket

1 REQUIREMENTS OF NEAR-SPACE EXPLORATION AND SCIENTIFIC EXPERIMENTATION

It is an important scientific research activity in China to carry out near-space exploration and scientific experiments via aerospace carriers.Early near-space exploration projects mainly used aircrafts,balloons,sounding rockets and Earth satellites to study various solar-Earth physical phenomena such as ionosphere,geomagnetism,cosmic rays,solar ultraviolet and X-rays,meteorite dust,comprehensive detection of the trace components in the middle and upper atmosphere (ozone,nitrogen dioxide,etc.),electric field,electron temperature,electron density,ion concentration and other environmental parameters.study the dynamic processes in the upper atmosphere and ionosphere and their responses to geomagnetic and solar activities.In addition,explore the mysteries in the atmosphere and ionosphere,while establishing the physical and empirical models of the upper atmosphere and ionosphere,and the coupling effects and application studies at various spatial levels in order to discover new physical mechanisms and principles.

With the development of China’s aerospace science and technology,microgravity science has become a frontier science that has developed rapidly in the past 20 years.China’s microgravity science mainly focuses on carrying out innovative research on the basic laws of microgravity in a microgravity fluid field,and continuously explores the intersection and integration of space materials science and space life science and biotechnology.Microgravity science research includes theoretical research,ground-based experimental research,and space science experiments,focusing on fluid physics,combustion,biomechanics,nano-biotechnology,the intersection and integration with material science and life science and other fields.As an important part of microgravity science,space science experimentation is one of the most important key links.It is necessary to customize advanced and expensive scientific test platforms to support it.So far,China has carried out a number of space science experiments on scientific test platforms such as SJ-5 scientific test satellite,Russian Mir space station,IL-76 weightlessness aircraft,Shenzhou 4 spacecraft,22nd recoverable satellite,SJ-8 recoverable breeding satellite,etc.In recent years,space science experiments have been conduted more and more frequently.

In 2016,the Space Additive Manufacturing Technology Parabolic (SAMTP) aircraft flight test team,organized by the Space Application Engineering and Technology Center of the Chinese Academy of Sciences (CAS),carried out a totally of 3 sorties,enabling 93 parabolic flight tests,over Bordeaux,France.In these tests,five kinds of materials and two kinds of manufacturing processes were verified and explored under a microgravity environment,and the characteristic of different materials and processes in a microgravity environment were obtained.Tests were successful and it was the first time that China has carried out 3D printing technology test verification in a microgravity environment.The test used a completely independently developed technology (one of the equipments was jointly developed with Chongqing Green Intelligent Technology Research Institute),which not only successfully printed the target sample,but also observed the influence of the microgravity environment on the manufacturing process and materials,collecting valuable data.

Figure 1 Physical arrangement of the internal composition of evaporation convection box

The SJ-10 launched in 2016 was a recoverable scientific experimental satellite specially used for microgravity science and space life science experiments.It was also one of the scientific satellites approved under the “Space Science Pilot Project” of CAS.The recovery capsule of the satellite carried experimental materials and samples back to the ground after 12 on-orbit operation days,while the orbit retention capsule would continue to work on-orbit for 3－5 days.During the space experiments,all engineering parameters and scientific data were transmitted to the ground through telemetry and data transmission downlink channels.Scientists carried out timely on-line processing and analysis on the ground and adjusted the space experiment plan.A total of 19 scientific experiments (including 10 microgravity scientific experiments and 9 space life science experiments)were completed,covering 6 disciplines such as microgravity fluid physics,microgravity combustion,space materials science,space radiation effects,microgravity biological effects and space biotechnology.Among them,the representative experimental devices of microgravity physics and space life science are given as follows.

Figure 2 Internal view of the space experimental device for cell growth and material transport research under microgravity

Figure 3 Photos of products used for research on the thermal diffusion characteristics of petroleum components and measurement of soret coefficient under microgravity conditions

2 APPROACHES TO NEAR-SPACE EXPLORATION AND SCIENTIFIC EXPERIMENTS

At present,the ways and carrier hosts to carry out nearspace exploration and scientific experiments mainly include falling towers,aircraft,sounding rockets,space stations,etc.Different carriers have their own advantages,disadvantages and application scopes.

2.1 Falling Tower

The falling tower is a ground microgravity test equipment.It provides microgravity for a free falling body,with a maximum duration of 10 s.The falling tower has the advantage that it is relatively simple to conduct experiments as a ground test facility.Once the test facility is completed,it can be reused for many times,and the cost is relatively low.Its disadvantage is that the microgravity duration provided is short,usually less than 10 s,which cannot meet some requirements when a long microgravity duration is required.

Figure 4 100-m falling tower at the microgravity laboratory,CAS

2.2 Aircraft

As a way to conduct near space exploration and scientific experimentation,the aircraft method is to fly the aircraft in a periodic parabolic flight thus realizing a microgravity environment by using the weightlessness state obtained in the descending segments.The microgravity level obtained in this way can reach 10-2g－10-3g,and the maximum microgravity duration can reach 20 s.The advantages of the aircraft method are relatively simple implementation,reusability,and relatively low cost.Its disadvantage is the same as that of falling tower:the single microgravity period is short,usually less than 20 s,which cannot meet the requirements of some tasks requiring long microgravity durations.

2.3 Sounding Rocket

Figure 5 Parabolic flight diagram

Figure 6 Parabolic repeated flight diagram

Sounding rocket technology refers to the technology of using rockets to measure the near-Earth space environment and utilize the near-Earth space resources.The rockets used for rocket sounding are called sounding rockets.It is a kind of rocket that carries out exploration and scientific experiments in near-Earth space.The flight altitude is between that of a sounding balloon and a satellite,and it is also the most important detection method in near-Earth space.Sounding rockets are generally uncontrolled rockets,which have the advantages of simple structure,low cost,short development period,flexible and convenient launching,etc..They can not only detect the structure,composition and parameters of atmospheric layers in the altitude,realizing the three-dimensional profile detection of the middle and upper atmosphere,but are also more suitable for temporary observation of special natural phenomena such as aurora,solar eclipses,solar eruption,and continuous observation of some natural phenomena that change with time and location.Moreover,sounding rockets can provide a microgravity environment,and the microgravity level can reach 4 g－10-5g,so can be used for experimental research on some special problems,such studying biopharmaceuticals,changing and adaptability of biological organisms in the microgravity environment,etc.In addition to carrying out comprehensive experiments,verification of flight experiments of spaceborne payloads,sounding rockets can also provide high-altitude atmospheric environment measurements for the launch of spacecraft such as satellites and spaceships,enabling monitoring and early warning of the electromagnetic environment in space.They have been widely used for space weather forecasting,research on the middle and upper atmosphere,research on the adjacent space environment,material processing under microgravity conditions,research on high altitude biology,exploration of Earth resources and other fields,and the application fields are still expanding.

At present,sounding rockets usually use solid booster rockets as power units,which have the advantages of being cheaper to host experiments than satellites or space stations,a short production cycle and microgravity durations of up to 10 mins.The disadvantage is that it can be used only once,the test equipment and samples cannot be reused,and the cost of a single test is expensive when compared with aircraft and falling towers.

Figure 7 Sounding rocket

Figure 8 International Space Station

Figure 9 Performance of different test platforms

2.4 Satellite or Spaceship (Space Station)

Compared with other near-space exploration and scientific experimental platforms,satellites or space stations have an obvious advantage and disadvantages.The advantage is that satellites or space stations can provide long-term microgravity action time,and their microgravity level can reach 10-2g－10-3g,which makes them the only choice for scientific missions requiring long-term experiments.In contrast,the shortcomings of satellites or space stations are also very obvious.Space stations(spaceships),satellites and other spacecrafts provide few opportunities and there are high costs for microgravity scientific experiments,hence the waiting test period is long.Scientific tasks that are in urgent need of experiments or with limited funds are often not compatible in terms of waiting time or to undertake.

Summing up the microgravity duration and microgravity level for different near-space exploration and scientific experimental platforms,as shown in Figure 9,through comparison and analysis,sounding rockets have the following advantages in carrying out near-space exploration and scientific experiments:

1) Compared with satellites or spaceships (space stations),sounding rockets have a lower launch cost and launch period,hence can quickly establish the test capability of the platform and provide test services.

2) Compared with aircraft and falling towers,sounding rockets can provide a test time length of 10 mins and a microgravity level of 10-4g－10-5g.The application range is wide enough to meet the test requirements of most space science experiments.

3 DEVELOPMENT DIRECTION OF THE CARRIER PLATFORM FOR NEAR-SPACE EXPLORATION AND SCIENTIFIC EXPERIMENT

Sounding rocket,as a carrier for near-space exploration and scientific experiment verification,has certain technical and application advantages,and can quickly establish a test capability to meet the increasing demand for near-space exploration and scientific experimental missions.In order to greatly reduce the experimental cost and improve the adaptability of the carrier for the experimental load,the following requirements are put forward for near space exploration and scientific experiment carriers.

3.1 Autonomous and Controllable Loiter Time and High-level Microgravity Environment

Near-space scientific experiments all put forward higher requirements for loiter time.A large number of microgravity experiments require loiter time of more than 10 mins plus a high-level microgravity environment.Some in-situ experiments require even higher requirements for loiter time.The carrier realizes autonomous and controllable flight process,which can meet the experimental load requirements to the greatest extent.

3.2 Improve the Statistical Value of Scientific Experiments and Reduce the Launch Cost through Repeated Use

Through system-level recovery,rapid testing,rapid use and maintenance of the carrier,multiple reuses are realized to reduce the cost of a single launch.At the same time,the reuse of experimental samples and experimental instruments and equipment is utilized to enhance the statistical value of scientific experiments.

3.3 Development of Standardization and Generalization of Experimental Load Cabin

The design of sounding rocket payload cabins tends to be standardized.In order to shorten the development cycle,reduce the cost and improve the cost performance ratio,many countries have gradually adopted standardized designs,i.e.,standardize the mechanical equipment,electronic equipment,data acquisition and management equipment and data transmission equipment carried by rockets while providing spacious equipment space.

4 APPLICATION OF CARRIER PLATFORMS OF MAINSTREAM NEAR-SPACE EXPLORATION IN THE WORLD

4.1 Development and Application of American Sounding Rockets

Since 1999,the United States introduced the famous rocket sounding project,NASA Sounding Rocket Operations Contrat(NSROC),which provides complete preliminary planning,design,development,integration,testing,launch and later analysis for its rocket sounding research.NSROC reached the ISO9000 standard,and the average number of launches per year is about 20.NSROC has 10 different types of sounding rockets,covering different detection altitudes and scientific application ranges.

Figure 10 Types of sounding rockets of the United States

As the leader of the national space industry,the development of commercial space in the United States is booming.Companies represented by SpaceX and Blue Origin have successively developed liquid recyclable and reusable rocket technologies,which are advanced technologies having subverted the traditional one-time use of rockets.SpaceX’s Falcon 9 and Falcon Heavy have successfully carried out many substage recovery missions,fully proving the feasibility and value of liquid recovery technologies and leading the development trend in international commercial space.

Liquid recoverable and reusable rocket technologies also provided new development ideas for near-space exploration.Blue Origin Company took the lead in proposing a space tourism project:passengers are transported to an altitude of more than 62 miles above the Earth through New Shepard rockets,at which passengers can experience weightlessness for several minutes and experience the view of the complete Earth.Obviously,this process can be regarded as near-space exploration including a microgravity scientific experiment.

Liquid recoverable and reusable rocket technologies not only greatly reduce the launch cost,but also break through the limitation of production capacity,thus greatly reducing the cost range of the liquid rocket launch service,making it even lower than that of disposable solid sounding rockets.Moreover,compared with disposable solid rockets,using liquid reuseable rockets as experimental platforms for near-space exploration and science it can realize the reuse of scientific samples,improve the statistical value of the test and reduce the cost of the test itself.

Figure 11 SpaceX rocket substage recovery

Figure 12 Blue Origin carrier

4.2 Development and Application of Japanese Sounding Rockets

Japan has conducted very extensive research on sounding rockets.Many scientific achievements have been made in atmospheric science,ionosphere,solar physics,astrophysics,atmospheric climate and prediction.In cooperation with the United States,UK,France and West Germany,various types of rocket experiments have been completed and unique exploration and researches on the equatorial region’s upper atmosphere,ionosphere and in astronomy have been carried out.

Similar to the development in the United States,in recent years,Japan has also been vigorously developing the reusable technologies for liquid rockets.In addition to the reusable verification flight platform CALLISTO developed with Germany and France,Japan Aerospace Exploration Agency (JAXA) has developed RV-X aircraft with a height of 7 m,a diameter of 1.8 m,a weight of 2900 kg and a LOX-LH engine to verify vertical landing guidance and control technology.In 2018,a vertical take-off and landing flight test to an altitude of 100 m was carried out.

Figure 13 RV-X aircraft

4.3 Development and Application of Sounding Rockets in Europe

The European Space Agency (ESA) has taken microgravity scientific experimental research as one of its main tasks and formulated a comprehensive development research plan,including microgravity experimental research using sounding rockets.

Similar to the development trend of the United States,in recent years,Europe has also been vigorously developing liquid reusable rockets.ESA provides a guarantee to ensure Europe’s entry into space through its future launch vehicle preparation plan.

CALLISTO,a reusable verification flight platform jointly developed by the CNES,DLR the German Space Agency and the JAXA,planned to carry out flight tests in 2020.The reusable LOX-LH engine developed by JAXA is to be used,with a rated thrust of 40 kN,a maximum mission profile height of 50 km and a maximum speed of Mach 5.Through CALLISTO’s comprehensive verification of the key technologies of the aerodynamic deceleration section and the dynamic soft landing section of the vertical landing process,as well as the verification of key components such as grid rudder,reaction control system,landing leg and main engine,technical support is provided for the new-generation Ariane 6 reusable rocket.According to the mission profile,the reusable verification flight platform CALLISTO already has the capability of a sounding rocket and can carry out near-space exploration and scientific experiments.

Figure 14 Validation flight platform CALLISTO

5 SIGNIFICANCE OF DEVELOPMENT OF MAINSTREAM NEAR-SPACE EXPLORATION CARRIER PLATFORMS AT HOME AND ABROAD

Through the above analysis of the development of sounding rockets at home and abroad,it can be seen that in recent years,with the continuous development of rocket sounding in various countries,the development trend of sounding rockets has shown the following characteristics.

1) The number of sounding rockets launched by various countries has not decreased,and the development momentum of sounding rockets is strong.Countries are paying more and more attention to projects in sounding rocket research.They have set up many research institutions and projects to launch sounding rockets for various purposes.

2) Sounding rockets from different countries are of great significance in scientific exploration.Sounding rockets in the United States and Japan are mostly used for space exploration,while sounding rockets in Europe are mainly used for microgravity science experiments,including microgravity physics experiments,microgravity life science and biotechnology experiments.

3) The weight of the payload carried by the sounding rocket is continuously increasing.The payload weight that a single sounding rocket can carry has increased from 50 kg in the early days to more than 800 kg.Carrying more weight and payload can reduce the launch cost and improve the cost performance of sounding rocket tests.

4) The flying height of sounding rockets is continuously improving.The flying height of the traditional sounding rocket is about 200 km,and can reach more than 1000 km at present.Of course,the flying height of sounding rockets is determined by the test target.In order to obtain a longer microgravity time,microgravity test rockets are often required to have a higher flying altitude performance.

5) All countries in the world are vigorously developing the reusable technologies of liquid rockets.Several reusable verification flight platforms in different countries have reached the flight and carrying capabilities of a sounding rocket and have the capability to carry out near-space exploration and scientific experiments.

6 CONCLUSION

Reusable liquid sounding rockets,as a carrier for near-space exploration and scientific experiment verification,has certain technical and application advantages,and can quickly establish a test capability to meet the increasing demand for near-space exploration and scientific experimental missions,so as to greatly reduce the experimental cost and improve the adaptability of the carrier to the experimental load.