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NASA Marshall Space Flight Center In-Space Cryogenic Propulsion Capabilities and Applications to Human Exploration

The current focus on lunar exploration and future human missions to Mars is driving in-space propulsion system requirements toward higher performance cryogenic systems with long-duration storage and operational capabilities. Not only do these systems offer higher performance than storable propellant options, but they also enable the potential for in-situ propellant production. Future Mars transit systems are envisioned to utilize either high-thrust nuclear thermal propulsion (with liquid hydrogen propellant), or hybrid systems with both cryogenic chemical systems (likely LOX/CH4) for high acceleration maneuvers and nuclear electric systems for long duration high Isp maneuvers. Exploration architectures based on either of these options require the use of high-performance cryogenic propellants with long-duration storage capabilities for both in-space transportation as well as planetary descent and ascent functions. Current efforts focusing on lunar exploration also rely on cryogenic propellants (either LOX/LCH4 or LOX/LH2) for lunar transit and descent/ascent transportation functions. In-space cryogenic propulsion systems pose numerous technology challenges with respect to long-duration propellant storage and usage, including advanced insulation, tank stratification and pressure management, cryogenic refrigeration to reduce propellant loss through boil off, low leakage cryogenic valves, low temperature liquid acquisition, and cryogenic propellant transfer. NASA has invested in technology development efforts, demonstrating individual technologies and systems-level operations. NASA Marshal Space Flight Center has also invested in multiple test facilities and modular test rigs that allow ground demonstration of numerous integrated technologies and systems concepts of operations. Additional investments have been made to mature analytical capabilities and design tools. These capabilities, both test/demonstration & engineering design/analysis, are available to support internal efforts and industrial partners in the development of exploration and science mission systems. With this increased interest, it is critical to understand the current state of in-space cryogenic propulsion technology, determine risks to its successful application to human exploration, and prepare the engineering, test, and evaluation capabilities to support the ambitious plans for future systems. This paper provides a survey of recent developments in in-space cryogenic propulsion and cryogenic propellant management technologies, as well as facilities and engineering/analytical capabilities ready to support current and future exploration efforts.

Cryogenic propulsion, cryogenic fluid management, ↗

NASA Marshall Space Flight Center In-Space Cryogenic Propulsion Capabilities and Applications to Human Exploration

The current focus on lunar exploration and future human missions to Mars is driving in-space propulsion system requirements toward higher performance cryogenic systems with long-duration storage and operational capabilities. Not only do these systems offer higher performance than storable propellant options, but they also enable the potential for in-situ propellant production. Future Mars transit systems are envisioned to utilize either high-thrust nuclear thermal propulsion (with liquid hydrogen propellant), or hybrid systems with both cryogenic chemical systems (likely LOX/CH 4 ) for high acceleration manoeuvres and nuclear electric systems for long duration high Isp manoeuvres. Exploration architectures based on either of these options require the use of high-performance cryogenic propellants with long-duration storage capabilities for both in-space transportation as well as planetary descent and ascent functions. Current efforts focusing on lunar exploration also rely on cryogenic propellants (either LOX/LCH 4 or LOX/LH 2 ) for lunar transit and descent/ascent transportation functions. In-space cryogenic propulsion systems pose numerous technology challenges with respect to long-duration propellant storage and usage, including advanced insulation, tank stratification and pressure management, cryogenic refrigeration to reduce propellant loss through boil off, low leakage cryogenic valves, low temperature liquid acquisition, and cryogenic propellant transfer. NASA has invested in technology development efforts, demonstrating individual technologies and systems-level operations. NASA Marshal Space Flight Center has also invested in multiple test facilities and modular test rigs that allow ground demonstration of numerous integrated technologies and systems concepts of operations. Additional investments have been made to mature analytical capabilities and design tools. These capabilities (both test/demonstration & engineering design/analysis) are available to support both internal efforts and industrial partners in the development of exploration and science mission systems. With this increased interest, it is critical to understand the current state of in-space cryogenic propulsion technology, determine risks to its successful application to human exploration, and prepare the engineering, test, and evaluation capabilities to support the ambitious plans for future systems. This paper provides a survey of recent developments in in-space cryogenic propulsion and cryogenic propellant management technologies, as well as facilities and engineering/analytical capabilities ready to support current and future exploration efforts.

Cryogenic propulsion↗

An Overview of NASA Space Cryocooler Programs--2006

Mechanical cryocoolers represent a significant enabling technology for NASA's Earth and Space Science Enterprises. Many of NASA's space instruments require cryogenic refrigeration to improve dynamic range, extend wavelength coverage, or enable the use of advanced detectors to observe a wide range of phenomena--from crop dynamics to stellar birth. Reflecting the relative maturity of the technology at these temperatures, the largest utilization of coolers over the last fifteen years has been for instruments operating at medium to high cryogenic temperatures (55 to 150K). For the future, important new developments are focusing on the lower temperature range, from 6 to 20 K, in support of studies of the origin of the Universe and the search for planets around distant stars. NASA's development of a 20K cryocooler for the European Planck spacecraft and a 6 K cryocooler for the MIRI instrument on the James Webb Space Telescope (JWST) are examples of the thrust to provide low-temperature cooling for this class of future missions.

cryogenics↗

Lightweight, Efficient Power Converters for Advanced Turboelectric Aircraft Propulsion Systems

NASA is investigating advanced turboelectric aircraft propulsion systems that use superconducting motors to drive multiple distributed turbofans. Conventional electric motors are too large and heavy to be practical for this application; therefore, superconducting motors are required. In order to improve aircraft maneuverability, variable-speed power converters are required to throttle power to the turbofans. The low operating temperature and the need for lightweight components that place a minimum of additional heat load on the refrigeration system open the possibility of incorporating extremely efficient cryogenic power conversion technology. This Phase II project is developing critical components required to meet these goals.

Hennessy, Michael J.↗

Liquefaction and Storage of In-Situ Oxygen on the Surface of Mars

ISRU is currently base-lined for the production of oxygen on the Martian surface in the Evolvable Mars Campaign Over 50 of return vehicle mass is oxygen for propulsion. There are two key cryogenic fluid-thermal technologies that need to be investigated to enable these architectures. High lift refrigeration systems. Thermal Insulation systems, either lightweight vacuum jackets of soft vacuum insulation systems.

Liquefaction↗

Bulk-Flow Analysis of Hybrid Thrust Bearings for Advanced Cryogenic Turbopumps

A bulk-flow analysis and computer program for prediction of the static load performance and dynamic force coefficients of angled injection, orifice-compensated hydrostatic/hydrodynamic thrust bearings have been completed. The product of the research is an efficient computational tool for the design of high-speed thrust bearings for cryogenic fluid turbopumps. The study addresses the needs of a growing technology that requires of reliable fluid film bearings to provide the maximum operating life with optimum controllable rotordynamic characteristics at the lowest cost. The motion of a cryogenic fluid on the thin film lands of a thrust bearing is governed by a set of bulk-flow mass and momentum conservation and energy transport equations. Mass flow conservation and a simple model for momentum transport within the hydrostatic bearing recesses are also accounted for. The bulk-flow model includes flow turbulence with fluid inertia advection, Coriolis and centrifugal acceleration effects on the bearing recesses and film lands. The cryogenic fluid properties are obtained from realistic thermophysical equations of state. Turbulent bulk-flow shear parameters are based on Hirs' model with Moody's friction factor equations allowing a simple simulation for machined bearing surface roughness. A perturbation analysis leads to zeroth-order nonlinear equations governing the fluid flow for the thrust bearing operating at a static equilibrium position, and first-order linear equations describing the perturbed fluid flow for small amplitude shaft motions in the axial direction. Numerical solution to the zeroth-order flow field equations renders the bearing flow rate, thrust load, drag torque and power dissipation. Solution to the first-order equations determines the axial stiffness, damping and inertia force coefficients. The computational method uses well established algorithms and generic subprograms available from prior developments. The Fortran9O computer program hydrothrust runs on a Windows 95/NT personal computer. The program, help files and examples are licensed by Texas A&M University Technology License Office. The study of the static and dynamic performance of two hydrostatic/hydrodynamic bearings demonstrates the importance of centrifugal and advection fluid inertia effects for operation at high rotational speeds. The first example considers a conceptual hydrostatic thrust bearing for an advanced liquid hydrogen turbopump operating at 170,000 rpm. The large axial stiffness and damping coefficients of the bearing should provide accurate control and axial positioning of the turbopump and also allow for unshrouded impellers, therefore increasing the overall pump efficiency. The second bearing uses a refrigerant R134a, and its application in oil-free air conditioning compressors is of great technological importance and commercial value. The computed predictions reveal that the LH2 bearing load capacity and flow rate increase with the recess pressure (i.e. increasing orifice diameters). The bearing axial stiffness has a maximum for a recess pressure rati of approx. 0.55. while the axial damping coefficient decreases as the recess pressure ratio increases. The computer results from three flow models are compared. These models are a) inertialess, b) fluid inertia at recess edges only, and c) full fluid inertia at both recess edges and film lands. The full inertia model shows the lowest flow rates, axial load capacity and stiffness coefficient but on the other hand renders the largest damping coefficients and inertia coefficients. The most important findings are related to the reduction of the outflow through the inner radius and the appearance of subambient pressures. The performance of the refrigerant hybrid thrust bearing is evaluated at two operating speeds and pressure drops. The computed results are presented in dimensionless form to evidence consistent trends in the bearing performance characteristics. As the applied axial load increases, the bearing film thickness and flow rate decrease while the recess pressure increases. The axial stiffness coefficient shows a maximum for a certain intermediate load while the damping coefficient steadily increases. The computed results evidence the paramount of centrifugal fluid inertia at low recess pressures (i.e. low loads), and where there is actually an inflow through the bearing inner diameter, accompanied by subambient pressures just downstream of the bearing recess edge. These results are solely due to centrifugal fluid inertia and advection transport effects. Recommendations include the extension of the computer program to handle flexure pivot tilting pad hybrid bearings and the ability to calculate moment coefficients for shaft angular misalignments.

SanAndres, Luis↗

The NASA-Lewis program on fusion energy for space power and propulsion, 1958-1978

An historical synopsis is provided of the NASA-Lewis research program on fusion energy for space power and propulsion systems. It was initiated to explore the potential applications of fusion energy to space power and propulsion systems. Some fusion related accomplishments and program areas covered include: basic research on the Electric Field Bumpy Torus (EFBT) magnetoelectric fusion containment concept, including identification of its radial transport mechanism and confinement time scaling; operation of the Pilot Rig mirror machine, the first superconducting magnet facility to be used in plasma physics or fusion research; operation of the Superconducting Bumpy Torus magnet facility, first used to generate a toroidal magnetic field; steady state production of neutrons from DD reactions; studies of the direct conversion of plasma enthalpy to thrust by a direct fusion rocket via propellant addition and magnetic nozzles; power and propulsion system studies, including D(3)He power balance, neutron shielding, and refrigeration requirements; and development of large volume, high field superconducting and cryogenic magnet technology.

Schulze, Norman R.↗

A Spinoff from Mariner

Among the technologies incorporated into the later Mariner missions was a dry film lubricant which offered exceptional lubrication quality for reduced friction and extended wear-life of mating parts in harsh interplanetary environments. Micro Surface Corporation acquired this technology, and currently market it as WS2 modified tungsten disulfide coating. A pressurized refrigerated air application process impinges a dry metallic WS2 coating without heat, curing, binders or adhesives. The coating binds instantly to metal or resin substrates with a 20 millionths of an inch thickness. Performance has been excellent in a variety of industries, particularly in plastics where in some operations, the coating increases production by reducing drag between tool steel and resin. Other advantages include product quality improvement, extension of equipment service life and maintenance elimination or reduction.

Source record↗

Cryogenic systems for the large deployable reflector

There are five technologies which may have application for Large Deployable Reflector (LDR), one passive and four active. In order of maturity, they are passive stored cryogen systems, and mechanical, sorption, magnetic, and pulse-tube refrigerators. In addition, deep space radiators will be required to reject the heat of the active systems, and may be useful as auxiliary coolers for the stored cryogen systems. Hybrid combinations of these technologies may well be more efficient than any one alone, and extensive system studies will be required to determine the best trade-offs. Stored cryogen systems were flown on a number of missions. The systems are capable of meeting the temperature requirements of LDR. The size and weight of stored cryogen systems are proportional to heat load and, as a result, are applicable only if the low-temperature heat load can be kept small. Systems using chemisorption and physical adsorption for compressors and pumps have received considerable attention in the past few years. Systems based on adiabatic demagnetization of paramagnetic salts were used for refrigeration for many years. Pulse-tube refrigerators were recently proposed which show relatively high efficiency for temperatures in the 60 to 80 K range. The instrument heat loads and operating temperatures are critical to the selection and design of the cryogenic system. Every effort should be made to minimize heat loads, raise operating temperatures, and to define these precisely. No one technology is now ready for application to LDR. Substantial development efforts are underway in all of the technologies and should be monitored and advocated. Magnetic and pulse-tube refrigerators have high potential.

Mason, Peter V.↗

Cryogenics and the Human Exploration of Mars

Current plans within NASA involve extending the human exploration of space from low earth orbit into the solar system, with the first human exploration of Mars presently planned in 2011. Integral to all hum Mars mission phases is cryogenic fluid management. Cryogenic fluids will be required both as propellant and for In-Situ Resource Utilization (ISRU). Without safe and efficient cryogen storage human Mars missions will not be possible. Effective control and handling of cryogenic fluids is the key to affordable Mars missions, and advancing active thermal control technology is synergistic with all of NASA's exploration initiatives and with existing and future instrument cooling programs, including MTPE and Origins. Present mission scenarios for human exploration require cryogenic propellant storage for up to 1700 days and for up to 60 metric tons. These requirements represent increases of an order of magnitude over previous storage masses and lifetimes. The key cryogenic terminology areas to be addressed in human Mars missions are long-term propellant storage, cryogenic refrigeration, cryogenic liquefaction, and zero gravity fluid management. Long-term storage for the thermal control of cryogenic propellants is best accomplished with a mix of passive and active technologies. Passive technologies such as advanced multilayer insulation (MLI) concepts will be combined with the development of active coolers (cryogenic refrigerators). Candidates for long-life active cooling applications include Reverse Turbo-Brayton, Stirling, and Pulse-Tube coolers. The integration of passive and active technologies will form a hybrid system optimized to minimize the launch mass while preserving the cryogenic propellants. Since cryogenic propellants are the largest mass that Mars missions must launch from earth, even a modest reduction in the percentage of propellant carried results in a significant weight saving. This paper will present a brief overview of cryogenic fluid management technology as it applies to the current human Mars mission scenarios.

Salerno, Louis J.↗

Micromachined Active Magnetic Regenerator for Low-Temperature Magnetic Coolers

A design of an Active Magnetic Regenerative Refrigeration (AMRR) system has been developed for space applications. It uses an innovative 3He cryogenic circulator to provide continuous remote/distributed cooling at temperatures in the range of 2 K with a heat sink at about 15 K. A critical component technology for this cooling system is a highly efficient active magnetic regenerator, which is a regenerative heat exchanger with its matrix material made of magnetic refrigerant gadolinium gallium garnet (GGG). Creare Inc. is developing a microchannel GGG regenerator with an anisotropic structured bed for high system thermal efficiency. The regenerator core consists of a stack of thin, single-crystal GGG disks alternating with thin polymer insulating layers. The insulating layers help minimize the axial conduction heat leak, since GGG has a very high thermal conductivity in the regenerator s operating temperature range. The GGG disks contain micro channels with width near 100 micrometers, which enhance the heat transfer between the circulating flow and the refrigerant bed. The unique flow configuration of the GGG plates ensures a uniform flow distribution across the plates. The main fabrication challenges for the regenerator are the machining of high-aspect-ratio microchannels in fragile, single-crystal GGG disks and fabrication and assembly of the GGG insulation layers. Feasibility demonstrations to date include use of an ultrashort- pulse laser to machine microchannels without producing unacceptable microcracking or deposition of recast material, as shown in the figure, and attachment of a thin insulation layer to a GGG disk without obstructing the flow paths. At the time of this reporting, efforts were focused on improving the laser machining process to increase machining speed and further reduce microcracking.

Chen, Weibo↗

TurboBrayton Cryocooler: A Flight Worthy and Promising Future

A new development in cryocooler technology, a reverse TurboBrayton cycle cryocooler, developed by Creare, Inc. of Hanover, NH, has now been flight tested. This cooler provides high reliability and long life. With no linear moving components common in current flight cryocoolers, the TurboBrayton cooler requires no active control systems to provide a vibration-free signature. The cooler provides first stage cooling for advanced cryogenic systems and serves as a direct replacement for stored cryogen systems with a longer lifetime. Following a successful flight on STS-95, a TurboBrayton cryocooler will be flown on Hubble Space Telescope (HST) in 2000 to provide renewed refrigeration capability for the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). The TurboBrayton cycle cooler is a promising technology already being considered for additional flight programs such as Next Generation Space Telescope (NGST) and Constellation X. These future missions require an advanced generation of the cooler that is currently under development to provide cooling at 10K and less. This paper presents an overview of the current generation cooler with recent flight test results and details the current plans and development progress on the next generation TurboBrayton technology for future missions.

Gibbon, Judith A.↗

Space Technology For Tuna Boats

Freshly-caught tuna is stored below decks in wells cooled to about zero degrees by brine circulated through a refrigerating system. The wells formerly were insulated by cork or fiberglass, but both materials were subject to deterioration; cork, for instance, needs replacement every three years. The Campbell Machine Division of Campbell Industries, San Diego, which manufactures and repairs large boats for the commercial fishing industry, was looking for a better way to insulate tuna storage wells. Learning of the Rockwell technique, Campbell contracted for a test installation on one boat, then bought its own equipment and adopted the spray-foam procedure for their boats. The foam hardens after application. It not only is a superior insulator, it also is considerably lighter and easier to apply. Fishing industry spokesmen say that foam insulation is far more reliable, efficient and economical than prior techniques. More than 40 foam-insulated tuna boats, ranging in cost from $1 million to $4 million, have been built and sold. Principal customers are Ralston Purina's Van Camp Seafood Division and Star-Kist Inc.

Source record↗

Gravitational Effects on Liquefaction Systems for Lunar and Mars Exploration

There is interest at NASA, other space agencies, and industry, in the liquefaction of fluids produced through in-situ processes on the surfaces of the Moon and Mars. A multi-center team at NASA recently considered multiple different refrigeration cycles and refrigeration integration methodologies and how these might fit into early liquefaction plants for NASA's exploration initiatives. The rate of liquefaction for these initiatives is quite slow in comparison to large scale terrestrial applications. These studies concluded that, for both structural and heat spreading reasons, integrating the refrigeration tubing on the surface of the storage tank wall is an attractive path to pursue in the near term. In order to develop a technology development path and inform investors, it was desired to investigate the sensitivity of gravity of the processes involved. An analysis of the condensation processes within the tank is performed. The objective is to determine the sensitivity of liquefaction to gravitational effects. The heat transfer mechanisms include forced convection heat removal to the refrigeration system (or cryocooler), conduction through the tank wall heat exchanger, and convection and condensation on the inner tank wall. Gravity affects the liquefaction process via condensate liquid drainage, natural convection in the ullage, and the shape of the liquid-vapor interface within the tank. Analysis of these mechanisms shows that while there is some sensitivity to gravitational level in general, within the bounds of current interest (rate of liquefaction appropriate to Lunar and Martian applications, and cooling capacity of the cryocooler), this sensitivity of liquefaction to gravity is quite small. Thus, system level testing on the Earth should suffice for the performance prediction and demonstration of liquefaction operations as applicable to Lunar and Martian applications.

ISRU↗

NASA Space Cryocooler Programs: A 2003 Overview

Mechanical cryocoolers represent a significant enabling technology for NASA's Earth and Space Science missions. An overview is presented of ongoing cryocooler activities within NASA in support of current flight projects, near-term flight instruments, and long-term technology development. NASA programs in Earth and space science observe a wide range of phenomena, from crop dynamics to stellar birth. Many of the instruments require cryogenic refrigeration to improve dynamic range, extend wavelength coverage, and enable the use of advanced detectors. Although, the largest utilization of coolers over the last decade has been for instruments operating at medium to high cryogenic temperatures (55 to 150 K), reflecting the relative maturity of the technology at these temperatures, important new developments are now focusing at the lower temperature range from 4 to 20 K in support of studies of the origin of the universe and the search for planets around distant stars. NASA's development of a 20K cryocooler for the European Planck spacecraft and its new Advanced Cryocooler Technology Development Program (ACTDP) for 6-18 K coolers are examples of the thrust to provide low temperature cooling for this class of missions.

Ross, R. G., Jr.↗

Sensor requirements for Earth and planetary observations

Future generations of Earth and planetary remote sensing instruments will require extensive developments of new long-wave and very long-wave infrared detectors. The upcoming NASA Earth Observing System (EOS) will carry a suite of instruments to monitor a wide range of atmospheric and surface parameters with an unprecedented degree of accuracy for a period of 10 to 15 years. These instruments will observe Earth over a wide spectral range extending from the visible to nearly 17 micrometers with a moderate to high spectral and spacial resolution. In addition to expected improvements in communication bandwidth and both ground and on-board computing power, these new sensor systems will need large two-dimensional detector arrays. Such arrays exist for visible wavelengths and, to a lesser extent, for short wavelength infrared systems. The most dramatic need is for new Long Wavelength Infrared (LWIR) and Very Long Wavelength Infrared (VLWIR) detector technologies that are compatible with area array readout devices and can operate in the temperature range supported by long life, low power refrigerators. A scientific need for radiometric and calibration accuracies approaching 1 percent translates into a requirement for detectors with excellent linearity, stability and insensitivity to operating conditions and space radiation. Current examples of the kind of scientific missions these new thermal IR detectors would enhance in the future include instruments for Earth science such as Orbital Volcanological Observations (OVO), Atmospheric Infrared Sounder (AIRS), Moderate Resolution Imaging Spectrometer (MODIS), and Spectroscopy in the Atmosphere using Far Infrared Emission (SAFIRE). Planetary exploration missions such as Cassini also provide examples of instrument concepts that could be enhanced by new IR detector technologies.

Chahine, Moustafa T.↗

Advances in cryogenic engineering. Vols. 37A & 37B - Proceedings of the 1991 Cryogenic Engineering Conference, Univ. of Alabama, Huntsville, June 11-14, 1991

The present volume on advances in cryogenic engineering discusses heat and mass transfer in helium, heat transfer in cryogenic fluids, thermoacoustic oscillations, and insulation. Attention is given to applications of superconductivity with reference to magnetic stability and coil protection, cryogenic techniques, and refrigeration for electronics and superconducting systems. Topics addressed include compressors, expanders, and pumps for liquid helium, magnetic refrigerators, pulse tube refrigerators, and cryocoolers. Also examined are properties of cryogenic fluids, cryogenic applications in transportion and space science and technology, and cryogenic instrumentation.

Fast, Ronald W.↗

Testing Devices Garner Data on Insulation Performance

To develop a test instrument that could garner measurements of the thermal performance of insulation under extreme conditions, researchers at Kennedy Space Center devised the Cryostat 1 and then Cryostat 2. McLean, Virginia-based QinetiQ North America licensed the technology and plans to market it to organizations developing materials for things like piping and storage tank insulation, refrigeration, appliances, and consumer goods.

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