Study on impulse and ablation of aluminum irradiated by millimeter spot of short pulse laser

Aluminum is a high performance working medium for laser ablation micro propulsion. In order to study the propulsion performance and ablation of aluminum under millimeter light spot irradiation, a short pulse Nd: YAG laser with wavelength of 1064nm and pulse width of 8NS was used to irradiate aluminum target in atmosphere. The impulse, the impulse coupling coefficient and the ablation morphology of the aluminum target produced by 6 kinds of millimeter-level light spots are measured. The experimental results show that when the spot diameter reaches 6-7mm, the increasing trend of impulse and impulse coupling coefficient of aluminum target with the increase of laser energy slows down; A large number of ablation products began to accumulate on the surface of the target pit.

Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity

Microjet hydrogen flames can be directly used as micro heat sources or can be applied in micro propulsion systems. In our previous study, under zero gravity and without an active air supply, the combustion completeness of hydrogen jet flames within a mesoscale tube with an inner diameter of 5 mm was very low. In this study, we were dedicated to improving the combustion efficiency by using a convergent nozzle (tilt angle was around 68°) instead of the previous straight one, and the exit diameter was 0.8 or 0.4 mm. The numerical results demonstrate that the maximum combustion efficiency in the case of d= 0.8 mm was only around 15%; however, the peak value for the case of d = 0.4 mm was around 36%. This happened because with d = 0.4 mm, the fuel jet velocity was around four times that of the d = 0.8 mm case. Hence, the negative pressure in the combustor of d = 0.4 mm decreased to a much lower level compared to that of d = 0.8 mm, which led to an enhancement of the air entrainment ratio. However, the highest combustion efficiency of d = 0.4 mm was still below 36%; therefore, a slightly larger tube or an even smaller nozzle exit diameter will be necessary for further improvements to the combustion efficiency.

Novel Structure and Thermal Design and Analysis for CubeSats in Formation Flying

The CANYVAL-C (CubeSat Astronomy by NASA and Yonsei using a virtual telescope alignment for coronagraph) is a space science demonstration mission that involves taking several images of the solar corona with two CubeSats—1U CubeSat (Timon) and 2U CubeSat (Pumbaa)—in formation flying. In this study, we developed and evaluated structural and thermal designs of the CubeSats Timon and Pumbaa through finite element analyses, considering the nonlinearity effects of the nylon wire of the deployable solar panels installed in Pumbaa. On-orbit thermal analyses were performed with an accurate analytical model for a visible camera on Timon and a micro propulsion system on Pumbaa, which has a narrow operating temperature range. Finally, the analytical models were correlated for enhancing the reliability of the numerical analysis. The test results indicated that the CubeSats are structurally safe with respect to the launch environment and can activate each component under the space thermal environment. The natural frequency of the nylon wire for the deployable solar panels was found to increase significantly as the wire was tightened strongly. The conditions of the thermal vacuum and cycling testing were implemented in the thermal analytical model, which reduced the differences between the analysis and testing.

Design of high-resolution flow sensor used in cold gas micro propulsion system

Cold Gas Micro Propulsion (CGMP) is a reliable technology for spacecraft attitude and orbit control used in drag-free control system to compensate the environmental disturbance from the aerospace. The CGMP requiring a very fine control resolution and low noise is desired to be used on TAIJI mission for gravitational wave detection which is supported by Chinese Academy of Science (CAS). One of CGMP’s key technologies is high-resolution Gas Mass Flow Sensor (GMFS). In this paper, calorimetric thermal flow sensor characterized with miniaturization, high sensitivity and low noise is studied by simulation method and manufacturing process. By simulating the influence of heating power, electrode distance, temperature, etc. on sensor response, the methods on optimizing sensitivity and accuracy have been proposed. The sensitivity is about 2.53 mV/(m/s)/mW. An amplifier circuit with ultra-low noise of 7.29 nV/[Formula: see text]Hz for reading out has been designed, which is essential for high resolution. The sensor was fabricated and preliminary tests have been conducted. The sensitivity of the sensor is about 100 mV/(m/s).

Ground performance tests and evaluation of RF ion microthrusters for Taiji-1 satellite

The “Taiji-1” satellite is a test satellite for the verification of those key technologies involved in the “Taiji Program in Space”, China’s space gravitational wave detection project; and the spacecraft drag-free control technology is one of its key technologies used to improve the microgravity level of spacecraft. Thus, a demand for a high-precision and continuously adjustable micronewton-level thrust has been proposed on the spacecraft micro-propulsion system. In allusion to such a task, a set of micronewton-level RF ion propulsion system was designed based on the principle of self-sustained discharge of RF plasma so as to conduct studies on the parameter optimization and engineering of RF ion thruster, and an engineering prototype of the micronewton-level continuously adjustable RF ion thruster was successfully developed to meet the design index requirements. The operating parameters have been solidified through further studies on the extreme operating conditions of the engineering prototype, and a series of ground simulation tests of space environment were successfully passed. The ground test and calibration experiment results of the micro-propulsion engineering prototype show that the engineering prototype has fully met the requirements of the Taiji-1 mission, thus having laid a solid foundation for the successful space verification of the key technologies for the “Taiji-1” satellite.

Exploration of the coupling between thrust and interference in Taiji-1

As the first technology verification satellite of the space-based gravitational wave detection in China, Taiji-1 has tested the high-precision space laser interferometer, the inertial sensor, the micro thruster and the hyperstatic satellite platform in orbit. The micro thruster plays an important role in the micro propulsion system. The purposes of the research are to investigate the relationship between the thrust and the interference, and then get a comprehensive understanding about the maximum effect of the thrust in Taiji-1. The transfer function between the thrust and the optical path difference fluctuations is established through the modeling, the simulation and the data postprocessing of Taiji-1. In addition, the maximum effect of the thrust in Taiji-1 is about 32 pm/[Formula: see text] with an integration time of 100 s. It can be neglected compared to the requirement of 100 pm/[Formula: see text] for the interferometer stability in Taiji-1.

Numerical analysis of high temperature gas flow through conical micronozzle

Micro-propulsion is considered to be the emerging technology for the propulsion of micro and micro aerospace vehicles as it is preferred over mesoscale thruster due to lower overall life-cycle cost and launching costs. Hence this paper investigates the influence of critical parameters like the Nozzle Pressure Ratio (NPR) and Reynolds number (Re) on the operational characteristics of the micronozzle. A conical nozzle with throat diameter 710 µm and exit/throat area ratio ∼2.14 has been designed and is analyzed numerically by using a model based on pressure-based coupled implicit for various NPR, the backpressure with three Res namely, 1000, 1500, and 2000. The performance of this micronozzle has been characterized in terms of thrust, thrust coefficient, and specific impulse for all three Re cases. A subsequent analysis of the subsonic layer reveals that the nozzle is subjected to high viscous losses at low NPRs, which are independent of Re.