Final test results for the ground operations demonstration unit for liquid hydrogen

Described herein is a comprehensive project—a large-scale test of an integrated refrigeration and storage system called the Ground Operations and Demonstration Unit for Liquid Hydrogen (GODU LH2), sponsored by the Advanced Exploration Systems Program and constructed at Kennedy Space Center. A commercial cryogenic refrigerator interfaced with a 125,000 l liquid hydrogen tank and auxiliary systems in a manner that enabled control of the propellant state by extracting heat via a closed loop Brayton cycle refrigerator coupled to a novel internal heat exchanger. Three primary objectives were demonstrating zero-loss storage and transfer, gaseous liquefaction, and propellant densification. Testing was performed at three different liquid hydrogen fill-levels. Data were collected on tank pressure, internal tank temperature profiles, mass flow in and out of the system, and refrigeration system performance. All test objectives were successfully achieved during approximately two years of testing. A summary of the final results is presented in this paper.     

Lifetime test and heritage on orbit of coolers for space use

This report describes the results and operating status of ground lifetime testing and achievements on orbit of coolers for space use. Ground lifetime tests of coolers of three types were conducted to demonstrate their long life and reliability. Three single-stage Stirling coolers were tested for 89,016, 71,871 and 68,273 h from 1998, a two-stage Stirling cooler was tested for 72,906 h, and a 4-K class cooler with a two-stage Stirling cooler and a Joule–Thomson cooler was tested for over 2.5 years. After lifetime tests were completed, a few coolers were investigated to determine the cause of the cooling performance degradation. Additionally, the filled gas of the coolers was analyzed. These coolers have shown good results on orbit. Three single-stage Stirling coolers were carried on the X-ray astronomical satellite “SUZAKU” (launched in July 2005), Japanese lunar polar orbiter “KAGUYA” (launched in September 2007), and the Japanese Venus Climate Orbiter “AKATSUKI” (launched in June 2010). Two units of a two-stage Stirling cooler were carried on the infrared astronomical satellite “AKARI” launched in February 2006. A 4-K class cooler was carried on the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) aboard the Japanese Experiment Module (JEM) of the International Space Station (ISS). SMILES was launched in September 2009.     

A test bed for insect-inspired robotic control

Flying insects are remarkable examples of sophisticated sensory-motor control systems. Insects have solved the fundamental challenge facing the field of mobile robots: robust sensory-motor mapping. Control models based on insects can contribute much to the design of robotic control systems. We present our work on a preliminary robotic control system inspired by current behavioural and physiological models of the fruit fly, Drosophila melanogaster. We designed a five-degrees-of-freedom robotic system that serves as a novel simulation/mobile robot hybrid. This design has allowed us to implement a fly-inspired control system that uses visual and mechanosensory feedback. Our results suggest that a simple control scheme can yield surprisingly robust fly-like robotic behaviour.     

Bubble growth constants for liquid hydrogen and liquid helium

Bubble growth constants are calculated for LH₂ and LHe at various pressures and liquid superheats for spherically symmetric growth using Scrivens'solution. The constants are shown to be applicable to bubble growth at a heated wall during boiling of cryogenic liquids.     

Capacitive level meter for liquid hydrogen

A capacitive level meter working at low temperatures was made to use in magnetic refrigerator for hydrogen liquefaction. The liquid level was measured from the capacitance between parallel electrodes immersed in the liquid. The meter was tested for liquid nitrogen, hydrogen, and helium. The operation was successful using an AC capacitance bridge. The estimated sensitivity of the meter is better than 0.2 mm for liquid hydrogen. The meter also worked with pressurized hydrogen.     

Hybrid genetic algorithm for test bed scheduling problems

In this paper, we address the scheduling problem for a heavy industry company which provides ship engines for shipbuilding companies. Before being delivered to customers, ship engines are assembled, tested and disassembled on the test beds. Because of limited test bed facilities, it is impossible for the ship engine company to satisfy all customers’ orders. Therefore, they must select the orders that can be feasibly scheduled to maximise profit. An integer programming model is developed for order selection and test bed scheduling but it cannot handle large problems in a reasonable amount of time. Consequently, a hybrid genetic algorithm (GA) is suggested to solve the developed model. Several experiments have been carried out to demonstrate the performance of the proposed hybrid GA in scheduling test beds. The results show that the hybrid GA performs with an outstanding run-time and small errors in comparison with the integer programming model.     

电容式密度传感器低密度液氢校准实验研究

设计、搭建了一套可调节密度式多点电容式密度传感器校准装置,并进行了电容式密度传感器低密度液氢的校准试验。实现了对液氢在一定低密度范围内(50—70kg/m3)的调节,突破了传统的常压单一密度点校准技术,实现了液氢多密度点的校准,提高了校准结果的可靠性。对电容式密度传感器校准装置各因素引入的不确定度分量进行了评定,分析得到了该装置的不确定度,试验结果表明采用给液氢增压的方式可以对液氢低密度进行准确控制,该调节装置的不确定度满足电容式密度传感器校准设计要求,并且能够对电容式密度传感器在多种低温流体介质中进行较宽密度范围校准。     

履带车辆台架试验台负载模拟方法研究

针对履带车辆台架试验台路面负载、惯性负载模拟问题,推导履带车辆整车等效惯量,建立履带车辆以主动轮输出扭矩为输入、主动轮速度为输出的动力学模型,通过对电机加载系统建模及控制器设计,根据系统特性,提出用速度跟踪结合扰动观测器的控制方法解决负载模拟问题,速度跟踪模块采用的单边速度闭环双边扭矩加载可减少程序的运算量及提高负载模拟精度。台架系统试验结果验证了设计方法的有效性及精确性。     

减振器性能试验台控制系统研究

以机械式减振器性能试验台为背景,设计基于可编程逻辑控制器(PLC)的减振器性能试验台控制系统,实现激振频率的程序化控制。使用USS协议实现西门子PLC与MM440变频器之间的通信,并利用PLC中梯形图程序控制变频器参数,再通过PLC与触摸屏之间的串口通信实现良好的人机界面交换,从而完成减振器性能试验台的自动控制。经现场试验测试,结果表明该方法能简单方便地控制试验台激振频率,并能通过触摸屏实时读取试验数据。     

Heat transfer in liquid hydrogen

With boiling of hydrogen under pressure one observes a shift of the q-ΔT curves to higher values of ΔT, caused by a layer of solidified gases, the thickness of which increases continuously. With this process one observes ‘hysteresis’.The departure diameter D and the frequency f of bubbles were observed with discrete nucleate boiling under pressure. The results can be described by the equation f D² = K; K diminishes with rising pressure and with increasing roughness of the surface.     

Aerogel insulation applications for liquid hydrogen launch vehicle tanks

Solutions to thermal insulation problems using aerogel beads were demonstrated for space launch vehicles using a model of the space shuttle external tank’s liquid hydrogen (LH₂) intertank. Test results using liquid helium show that with aerogel, the nitrogen mass inside the intertank is greatly reduced and free liquid nitrogen is eliminated. Physisorption within the aerogel was also investigated, showing that the sorption ratio (liquid nitrogen to aerogel beads) is about 62%. The insulating effectiveness of the aerogel shows that cryopumping is driven by thermal communication between warm and cold surfaces. This technology can solve heat transfer problems and augment existing thermal protection systems on launch vehicles.     

基于CAN总线的主逆变器试验台的设计

针对目前对HXD3、HXD3C、HXD1B、HXD1C型电力机车变流器故障诊断需求以及它们之间的性能差异,提出使用CAN总线将各功能模块连接起来,并通过分析处理软件对测试数据进行分析、处理,并对存在故障的变流器进行故障诊断。利用CAN总线易于扩展、结构简单的特点,改变了以前诊断系统功能单一、不易扩展等缺点,便于系统的升级和节约重复设计的成本。     

Development of a nanowire-based test bed device for molecular electronics applications

In this paper, we present a novel test bed system which we believe addresses several key challenges in molecular electronics, i.e., the need to fabricate metal-molecule-metal junctions that have the potential to facilitate single-molecule measurements, are easily characterized, and are reproducible. The system is based upon template-electrodeposited metal nanowires incorporating a self-assembled monolayer spacer that are fabricated into electrical devices using direct-write photolithography. Removal of the spacer leaves a nanometer-sized, characterizable gap to which nanoparticles or a test molecule of interest can be attached postfabrication. Here we report the fabrication procedure together with results showing the application of these devices to the study of the i/V characteristics of Au nanoparticles at cryogenic temperatures. These data demonstrate that the performance of these easily produced, inexpensive, novel devices compares favorably to that of devices made using preexisting methods.     

一种液体型号导弹加注泵车测试系统的开发

针对加注泵车现场噪音大及操作人员数量受限的问题,本文提出了一种液体型号导弹加注泵车测试系统.系统采用机电一体化的结构方式,通过单片机Atmega8535采集泵车加注信息,由终端计算机实现加注信息的处理、监测和显示.此外,系统还可以对泵车故障进行报警提示.实际应用证明,该系统性能良好,测量精度高,具有广阔的应用前景.     

管片拼装试验台回转电液控制系统设计及试验分析

 针对管片拼装机高速、高精度及低冲击自动拼装技术的需求,在全面分析了管片拼装机回转驱动系统大行程、大惯量及长时间运行特点的基础上,设计了以比例换向阀为调节核心、以平衡阀为辅助保障的管片拼装试验台回转电液控制系统.参考工程应用管片拼装机相关参数及管片拼装试验台设计要求,基于相似理论提出拼装试验台回转电液控制系统参数指标及原理图,运用SolidWorks建模仿真及负载力矩分析,进而完成电液控制系统参数设计及元件选型,最后完成了¢2 m管片拼装试验台回转电液控制系统的搭建及试验分析工作.试验分析结果表明：系统稳态性能满足设计要求,最大转速为6.25 r/min;同时具有良好的动态性能,系统阶跃响应峰值时间为1.1 s,可平稳实现斜坡减速及低速停车．     

液氢长距离管道输送探讨

讨论了液氢在长距离管道输送中存在着最佳流速,并分析了实际液氢输送过程中的输送状态.对在稳定的大流量转注过程中存在的单相流和两相流两种流动状态分别给出了在不同压力、流速、漏热等情况下温升、蒸气含量的理论计算结果,并在试验的结果上对液氢的流动状态给出了一些看法.