Cryogenic propellant liquefaction and storage for a precursor to a human Mars mission

An analysis of cryogenic liquefaction and storage methods for in-situ produced propellants (oxygen and methane) on Mars is presented. The application is to a subscale precursor sample return mission, intended to demonstrate critical cryogenic technologies prior to a human mission. A heat transfer analysis is included, resulting in predicted cryogenic tank surface temperatures and heat leak values for different conditions. Insulation thickness is traded off against cryocooler capacity to find optimum combinations for various insulation configurations, including multilayer insulation and microspheres. Microsphere insulation is shown to have promise, and further development is recommended.     

Recovery of lunar surface access module residual and reserve propellants

The vision for space exploration calls for human exploration of the lunar surface in the 2020 timeframe. Sustained human exploration of the lunar surface will require supply, storage, and distribution of consumables for a variety of mission elements. These elements include propulsion systems for ascent and descent stages, life support for habitats and extra-vehicular activity, and reactants for power systems. NASA KSC has been tasked to develop technologies and strategies for consumables transfer for lunar exploration as part of the exploration technology development program. This paper will investigate details of operational concepts to scavenge residual propellants from the lunar descent propulsion system. Predictions on the mass of residuals and reserves are made. Estimates of heat transfer and boil-off rates are calculated and transient tank thermodynamic issues post-engine cutoff are modeled. Recovery and storage options, including cryogenic liquid, vapor and water are discussed, and possible reuse of LSAM assets is presented.     

Cryogenic propulsion for the Titan Orbiter Polar Surveyor (TOPS) mission

Liquid hydrogen (LH2) and liquid oxygen (LO2) cryogenic propellants can dramatically enhance NASA’s ability to explore the solar system due to their superior specific impulse (I_sp) capability. Although these cryogenic propellants can be challenging to manage and store, they allow significant mass advantages over traditional hypergolic propulsion systems and are therefore enabling for many planetary science missions. New cryogenic storage techniques such as subcooling and the use of advanced insulation and low thermal conductivity support structures will allow for the long term storage and use of cryogenic propellants for solar system exploration and hence allow NASA to deliver more payloads to targets of interest, launch on smaller and less expensive launch vehicles, or both. These new cryogenic storage technologies were implemented in a design study for the Titan Orbiter Polar Surveyor (TOPS) mission, with LH2 and LO2 as propellants, and the resulting spacecraft design was able to achieve a 43% launch mass reduction over a TOPS mission, that utilized a traditional hypergolic propulsion system with mono-methyl hydrazine (MMH) and nitrogen tetroxide (NTO) propellants. This paper describes the cryogenic propellant storage design for the TOPS mission and demonstrates how these cryogenic propellants are stored passively for a decade-long Titan mission that requires the cryogenics propellants to be stored for 8.5 years.     

A Sounding Rocket Experiment to Control Boiling by Means of Acoustic Waves

One of the most critical issues when considering long-term space exploration missions is the management and storage of cryogenic propellants. The exposure of storage tanks to radiation and extreme temperatures implies the need of efficient technologies to counteract their effects on the fuel. A potentially dangerous effect for spacecraft operations is the generation of vapor bubbles in cryogenic propellants. We present an experimental setup and procedure to mature a technology based on acoustic waves to control boiling in microgravity.     

Passive ZBO storage of liquid hydrogen and liquid oxygen applied to space science mission concepts

Liquid hydrogen and oxygen cryogenic propulsion and storage were recently considered for application to Titan Explorer and Comet Nuclear Sample Return space science mission investigations. These missions would require up to 11 years of cryogenic storage. We modeled and designed cryogenic propellant storage concepts for these missions. By isolating the propellant tank’s view to deep space, we were able to achieve zero boil-off for both liquid hydrogen and oxygen propellant storage without cryocoolers. Several shades were incorporated to protect the tanks from the sun and spacecraft bus, and to protect the hydrogen tank from the warmer oxygen tank. This had a dramatic effect on the surface temperatures of the propellant tank insulation. These passive storage concepts for deep space missions substantially improved this application of cryogenic propulsion. It is projected that for missions requiring larger propellant tank sizes, the results would be even more dramatic.     

Concept for on orbit liquid hydrogen test bed

There is growing interest in the utilization of cryogenic propellants for future space missions. The utilization of these propellants for long duration in space presents substantial challenges in fluid management in the low g environment. Lockheed Martin (LM) is developing the concept for a space borne system for demonstration of long term storage, various fluid management tests involving control of tank pressure, location and identification of vapor and liquid phases, venting in low g, mass gauging, and extension of life with cryocoolers and location of liquid for transfer. In addition the concept includes autonomous coupling and hydrogen transfer from tank to tank. The concept is based on a flight qualified flight proven hydrogen Dewar design from a previous program The concept for this system is described.     

空间低温流体贮存的压力控制技术进展

分析了空间微重力条件对低温流体贮存的影响,重点介绍了亚临界空间低温流体贮存压力控制技术的主要内容和技术发展情况,并简要展望了空间低温流体贮存技术在未来空间系统中的应用。     

热沉最佳稳定工况仿真技术

介绍了热沉最佳稳定工况的概念、数字模型及其计算机实现，并利用本文的软件对国内最大的空间环模器热沉进行了仿真研究，验证了该技术的可行性。热沉最佳稳定工况仿真研究对指导大型空间环境模拟器初期的调试试验有重要意义。     

Cryogenic system design of the next generation infrared space telescope SPICA

The Japanese infrared space telescope SPICA mission, following the successful Akari mission, has been studied at the concept design phase in international collaboration with ESA under the framework of the ESA Cosmic Vision 2015-2025. The SPICA spacecraft is to be launched in 2018 and transferred into a halo orbit around the Sun-Earth L2 to obtain a stable thermal environment where the IR space telescope’s large mirror of 3 m-class in diameter can be cooled to <5.5 K with mechanical coolers and effective radiative cooling with no use of stored cryogen. The SPICA’s large and cold telescope is expected to provide unprecedented scientific observation optimized for mid-IR and far-IR astronomy with ultra-high sensitivity and excellent spatial resolution during a nominal mission life of 3 years (goal 5 years). Thermal and structural analyses show that the obtained design of the SPICA cryogenic system satisfies the mission requirement. Mechanical coolers for the 4.5 K stage and the 1.7 K stage, which have been continuously developed, have a sufficient cooling capacity with low power consumption to lift the heat loads from instruments and parasitic heat loads. As a result, it is concluded that the concept design of the SPICA cryogenic system is confirmed for the initial cooling mode after launch and the nominal operation mode.     

Magnetic levitation technology and its applications in exploration projects

An energy efficient cryogenic transfer line with magnetic suspension has been prototyped and cryogenically tested. The prototype transfer line exhibits cryogen saving potential of 30–35% in its suspension state as compared to its solid support state. Key technologies developed include novel magnetic levitation using multiple-pole high temperature superconductor (HTS) and rare earth permanent-magnet (PM) elements and a smart cryogenic actuator as the warm support structure. These technologies have vast applications in extremely low thermal leak cryogenic storage/delivery containers, superconducting magnetic bearings, smart thermal switches, etc. This paper reviews the development work and discusses future applications of established technologies.     

Three-dimensional analysis for liquid hydrogen in a cryogenic storage tank with heat pipe–pump system

This paper presents a study on fluid flow and heat transfer of liquid hydrogen in a zero boil-off cryogenic storage tank in a microgravity environment. The storage tank is equipped with an active cooling system consisting of a heat pipe and a pump–nozzle unit. The pump collects cryogen at its inlet and discharges it through its nozzle onto the evaporator section of the heat pipe in order to prevent the cryogen from boiling off due to the heat leaking through the tank wall from the surroundings. A three-dimensional (3-D) finite element model is employed in a set of numerical simulations to solve for velocity and temperature fields of liquid hydrogen in steady state. Complex structures of 3-D velocity and temperature distributions determined from the model are presented. Simulations with an axisymmetric model were also performed for comparison. Parametric study results from both models predict that as the speed of the cryogenic fluid discharged from the nozzle increases, the mean or bulk cryogenic fluid speed increases linearly and the maximum temperature within the cryogenic fluid decreases.     

Cryogenic Boiling and Two-Phase Flow during Pipe Chilldown in Earth and Reduced Gravity

For many industrial, medical and space technologies, cryogenic fluids play indispensable roles. An integral part of the cryogenic transport processes is the chilldown of the system components during initial applications. In this paper, we report experimental results for a chilldown process that is involved with the unsteady two-phase vapor-liquid flow and boiling heat transfer of the cryogen coupled with the transient heat conduction inside pipe walls. We have provided fundamental understanding on the physics of the two-phase flow and boiling heat transfer during cryogenic quenching through experimental observation, measurement and analysis. Based on the temperature measurement of the tube wall, the terrestrial cryogenic chilldown process is divided into three stages of film boiling, nucleate boiling and single-phase convection that bears a close similarity to the conventional pool boiling process. In earth gravity, cooling rate is non-uniform circumferentially due to a stratified flow pattern that gives rise to more cooling on the bottom wall by liquid filaments. In microgravity, there is no stratified flow and the absence of the gravitational force sends liquid filaments to the central core and replaces them by low thermal conductivity vapor that significantly reduces the heat transfer from the wall. Thus, the chilldown process is axisymmetric, but longer in microgravity.      

空间低温热管的设计与实验研究

介绍了为空间辐射制冷器研制开发的一种干道吸液芯氮气低温热管 ,该热管直径为6mm ,长度210mm ,工作温度80 .0～120 .0K ,最大传热功率可达2.5W ;并对其传热性能进行了实验研究。实验结果表明低温热管的传热性能远远优于固体的导热性能 ,完全能够满足辐射制冷器冷焦面耦合需要     

Two-Phase Flow and Heat Transfer During Chilldown of a Simulated Flexible Metal Hose Using Liquid Nitrogen

For many industrial, medical and space technologies, cryogenic fluids play irreplaceable roles. When any cryogenic system is initially started, it must go through a transient chill down period prior to normal operation. Chilldown is the process of introducing the cryogenic liquid into the system, and allowing the system components to cool down to several hundred degrees below the ambient temperature. The chilldown process is an important initial stage before a system begins functioning. The objective of this paper is to investigate the chilldown process associated with a flexible hose that was simulated by a channel with saw-teeth inner wall surface structure in the current study. We have investigated the fundamental physics of the two-phase flow and quenching heat transfer during cryogenic chilldown inside the simulated flexible hose through flow visualization, data measurement and analysis. The flow pattern developed inside the channel was recorded by a high speed camera for flow pattern investigation. The experimental results indicate that the chilldown process that is composed of unsteady vapor-liquid two-phase flow and phase-change heat transfer is modified by the inner wall surface wavy structure. Based on the measurement of the channel wall temperature, the teeth structure and the associated cavities generally reduce the heat transfer efficiency compared to the straight hose. Furthermore, based on the measured data, a complete series of correlations on the heat transfer coefficient for each heat transfer regime was developed and reported.     

Experimental study on natural circulation precooling of cryogenic pump system with gas phase inlet reflux configuration

A novel gas-phase inlet configuration in the natural circulation system instead of the liquid-phase inlet is introduced to cool down a cryogenic pump system from room temperature to cryogenic temperatures, effectively. The experimental apparatus is illustrated and test process is described. Heat transfer and pressure drop data during the cool-down process are recorded and portrayed. By contrast with liquid-phase inlet configuration, experimental results demonstrate that the natural circulation with the gas-phase inlet configuration is an easier and more controllable way to cool down the pump system and maintain it at cryogenic temperatures.     

Example of cryogenic process simulation using EcosimPro: LHC beam screen cooling circuits

CERN has developed a dedicated library to model helium cryogenic plants with a commercial software called EcosimPro. The aim of such a library is to provide a simple way to model small and large scale cryogenic systems performing dynamic simulations in an acceptable timescale to assist both control and operation teams in the optimal commissioning and operation of cryogenic plants. Moreover, the tool allows users to easily develop models related to their specific components such as cryogenic transfer lines or superconducting magnets. During the last few years, this library has been used to model several CERN cryogenic systems. The models have been used for different purposes, e.g. operator training, virtual commissioning of control systems and control optimization. This paper briefly presents EcosimPro with the cryogenic library developed at CERN and gives an example of modeling the LHC beam screen cooling circuits showing simulation results compared with experimental data.     

A modified jacketed cold storage design

The development of an energy efficient and economical modified jacketed vegetable storage concept and design is presented. Most fruits and vegetables require a storage environment near 0°C and 100%rh, which is difficult to achieve with conventional refrigeration systems. In a jacketed storage system, refrigerated air is circulated through air spaces surrounding the storage. High relative humidity levels can be achieved through the use of the large heat transfer surface of walls, ceiling and floor maintained at uniform temperature, and by preventing transmission heat gains into the storage space. While the jacket concept was initially introduced as a full jacket (covering walls, ceiling and floor), this paper discusses an alternative jacketed design which uses only the ceiling as a heat transfer surface. Based on construction simplicity, it is felt that this jacket design can be applied to conversion of conventional storage facilities and to new storage facilities. Acceptable relative humidity levels are attainable by the jacketed ceiling design with an extended heat transfer surface. It is expected that this concept will find favourable applications for storing fruits and vegetables wherever high humidity, medium temperature cold rooms are required.     

Hydrogen powered automobiles must use liquid hydrogen

A problem of particular interest and importance in the evaluation of a future hydrogen-oxygen economy is hydrogen's use as a fuel for highway vehicles.If, as many authors suggest, hydrogen is the only fuel that will simultaneously keep the environment clean and conserve natural resources, it must eventually be applied to the private vehicles that are a major pollution offender. Although a number of automobiles have been successfully operated on hydrogen (and this represents no large problem even with unmodified engines), the question remains of how to carry the fuel. This problem is primarily in the technology of the fuel tank - that is how to carry the hydrogen on board the vehicle safely, economically, and with a minimum of other penalties. It is unfortunate that this problem has attracted a number of suggested solutions that are less than optimum (for example, high-pressure gas and metallic hydrides) and that detract from the credibility of entire concept.If, as this author contends, the use of cryogenic liquid hydrogen is the sole, real candidate, its use will have a broad effect on industry. While requiring no basic research, it will necessitate key engineering developments in both the very large cryogenic production facilities and the small vehicle storage vessels and ancillary systems and hardware.     

Structural analysis of a cryogen-free refrigerator for space

Future X-ray observatories in space, such as European Space Agency's (ESA) X-ray evolving universe spectroscopy (XEUS) mission, will require cooling to the region 10–100 mK to enable the utilisation of advanced cryogenic photon detectors in cryogenic spectrometer instruments. Such missions are envisaged to be completely cryogen-free, replacing the traditional superfluid liquid helium cryostat with a space worthy mechanically cooled system. As part of the Mullard Space Science Laboratory's (MSSL) adiabatic demagnetisation refrigerator (ADR) development programme, we have investigated the construction of a flight cryostat containing a 10 mK ADR (the MSSL double ADR (dADR)) that can be cooled by a single Astrium (formally Matra Marconi Space (MMS)) 4 K mechanical cooler. A proto-type dADR has been constructed and will be flight proven as part of a sounding rocket payload, where the dADR system will be used to cool an array of superconducting tunnel junction (STJ) detectors at the focus of an X-ray telescope.     

A coupled numerical analysis of shield temperatures, heat losses and residual gas pressures in an evacuated super-insulation using thermal and fluid networks: Part II: Unsteady-state conditions (cool-down period)

This paper analyses the cool-down period of a 300 L super-insulated cryogenic storage tank for liquid nitrogen. Storage tank and evacuated shields are the same as described in part I of this paper where stationary states were investigated. The aim of the present paper is to introduce thermal resistance networks as a tool to quantitatively understand and control also unsteady-states like cool-down of super-insulations. Numerical simulations using thermal resistance networks have been performed to determine time dependence of local shield temperatures and heat loss components. Coupling between radiation and solid conduction is investigated under these conditions. Using the numerical results, we have checked an experimental method suggested in the literature to separate heat losses through the insulation from losses through thermal bridges by measurement of unsteady-state evaporation rates. The results of the simulations confirm that it takes the outer shields much longer to reach stationary temperature; cool-down does not proceed uniformly in the super-insulation. Coupling between different heat transfer modes again is obvious. Thermal emissivity is important also during the early phase of cool-down. Using the obtained numerical results, the experimental method to separate heat loss components could only roughly been confirmed for thick metallic foils.