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NASA NTRS2005

Utilizing Radioisotope Power System Waste Heat for Spacecraft Thermal Management

An advantage of using a Radioisotope Power System (RPS) for deep space or planetary surface missions is the readily available waste heat, which can be used for a number of beneficial purposes including: maintaining electronic components within a controlled temperature range, warming propulsion tanks and mobility actuators, and maintaining liquid propellants above their freezing temperature. Previous missions using Radioisotope Thermoelectric Generators (RTGs) dissipated large quantities of waste heat due to the low efficiency of the thermoelectric conversion technology. The next generation RPSs, such as the 110-Watt Stirling Radioisotope Generator (SRG110) will have higher conversion efficiencies, thereby rejecting less waste heat at a lower temperature and may require alternate approaches to transferring waste heat to the spacecraft. RTGs, with efficiencies of ~6 to 7 percent, reject their waste heat at the relatively high heat rejection temperature of 200 C. This is an advantage when rejecting heat to space; however, transferring heat to the internal spacecraft components requires a large and heavy radiator heat exchanger. At the same time, sensitive spacecraft instruments must be shielded from the thermal radiation of the RTG. The SRG110, with an efficiency around 22 percent and 50 C nominal housing surface temperature, can readily transfer the available waste heat directly via heat pipes, thermal straps, or fluid loops. The lower temperatures associated with the SRG110 avoid the chances of overheating other scientific components, eliminating the need for thermal shields. This provides the spacecraft designers more flexibility when locating the generator for a specific mission. A common misconception with high-efficiency systems is that there is not enough waste heat for spacecraft thermal management. This paper will dispel this misconception and investigate the use of a high-efficiency SRG110 for spacecraft thermal management and outline potential methods of waste heat utilization in several conceptual missions (Lunar Rover, Mars Rover, and Titan Lander). The advantages associated with the SRG110 as they relate to ease of assembly, less complex interfaces, and overall mass savings for a spacecraft will be highlighted.

Pantano, David R.↗

NASA NTRS2008

A Compact, Modular Superconducting Bolometer Array Package

We have designed a detector package to house a superconducting bolometer array, SQUID multiplexers, bias and integration circuitry, optical filtering, electrical connectors, and thermal/mechanical interfaces. This package has been used successfully in the GISMO 2mm camera, a 128-pixel camera operating at a base temperature of 270mK. Operation at lower temperatures is allowed by providing direct heat sinking to the SQUIDS and bias resistors, which generate the bulk of the dissipation in the package. Standard electrical connectors provide reliable contact while enabling quick installation and removal of the package. Careful design has gone into the compensation for differing thermal expansions, the need for heat sinking of the bolometer array, and the placement of magnetic shielding in critical areas. In this presentation, we detail the design and performance of this detector package and describe its scalability to 1280- pixel arrays in the near future.

Benford, Dominic J.↗

NASA NTRS1999

Thermal Control Replacement Materials Evaluated for Durability and Selected for the Hubble Space Telescope

During the Hubble Space Telescope (HST) second servicing mission, astronauts noticed that the outer layer of the multilayer insulation (MLI) was cracked in many locations around the telescope. The insulation s outer layer is composed of 5-mil (0.127 mm) Teflon FEP (DuPont; fluorinated ethylene propylene) with vapor-deposited aluminum (VDA) on the backside. The MLI blankets, which are used on over 80 percent of the external surface of the telescope, provide passive thermal control for equipment. Two large cracks were observed on the light shield directly above the high gain antenna. The upper light shield crack propagated from a cut placed in the blanket during installation around a handrail standoff. Two cracks propagated almost normal to each other, with the outer layer curling tightly as the cracks propagated. A second much larger vertical crack had started to curl and lift away from the telescope, as seen in the figure. MLI on the equipment bays was cracked extensively also, and in some areas it had pulled away from the bay. Continued degradation of the equipment bay insulation would potentially cause limited observations because of housekeeping boxes; for example, the data interface unit could overheat during some portions of the year, in certain sun angles.

deGroh, Kim K.↗

NASA NTRSDate not supplied

Thermal Analysis of an In-Space Heat Shield Exposed to a Rocket Plume During Stage Separation

Thermal analyses were conducted to evaluate the thermal response of various individual materials and multi-layer configurations for an in-space heat shield exposed to a rocket plume during stage separation. Frequently used, readily available thermal protection materials consisting of cork, carbon cloth phenolic (CCP), and silica cloth phenolic (SCP) were selected for an initial screening analysis. SCP was chosen as the primary material for further evaluation using an updated thermal environment calculated using computational fluid dynamics (CFD) results. A multi-layer configuration consisting of SCP providing erosion resistance and a Nomex honeycomb providing thermal protection was then evaluated as a solution for more mass-efficient performance. Pyrolysis depth, bondline temperature, back-side temperature, and a thermal factor of safety were used to define the necessary material thickness profile. Adhesives were included in the analyses with considerations for maximum temperature and application method. One dimensional thermal analyses at several stations along the heat shield surface were performed for the initial screening and follow-on analyses. The methodology used standard processes and computer programs applicable to solid rocket motor internal insulation and nozzle thermal analysis such as Chemical Equilibrium and Applications (CEA), Aerotherm Chemical Equilibrium (ACE), Momentum/Energy Integral Technique (MEIT), and Insulation Thermal Response and Ablation Code (ITRAC). The baseline SCP/Nomex honeycomb multi-layer configuration thermal performance predictions satisfied the objectives with an acceptable mass estimate for the design maturity. The EA9673 film adhesive and SCP resin were the best performing bonding agents considered for the SCP/Nomex honeycomb and Nomex honeycomb/structural substrate interfaces. The baseline mass estimate was lowest when the resin was the bonding agent due to the higher maximum service temperature. These thermal analyses evaluated typical internal and external nozzle materials using a calculated thermal environment and heat loads that were lower than a typical rocket motor internal environment but greater than standard external aeroheating.

Andrew T Hiatt↗

NASA NTRS1971

The relative effects of entry parameters on thermal protection system weight

Shielding a spacecraft from the severe thermal environment of an atmospheric entry requires a sophisticated thermal protection system (TPS). Thermal computer program models were developed for two such TPS designs proposed for the space shuttle orbiter. The multilayer systems, a reusable surface insulation TPS, and a re-radiative metallic skin TPS, were sized for a cross-section of trajectories in the entry corridor. This analysis indicates the relative influence of the entry parameters on the weight of each TPS concept. The results are summarized graphically. The trajectory variables considered were down-range, cross-range, orbit inclination, entry interface velocity and flight path angle, maximum heating rate level, angle of attack, and ballistic coefficient. Variations in cross-range and flight path angle over the ranges considered had virtually no effect on the required entry TPS weight. The TPS weight was significantly more sensitive to variations in angle of attack than to dispersions in the other trajectory considered.

Hirasaki, P. N.↗

NASA NTRS2001

A Compact, High-Performance Continuous Magnetic Refrigerator

We present test results of the first adiabatic demagnetization refrigerator (ADR) that can produce continuous cooling at sub-kelvin temperatures. This system uses multiple stages that operate in sequence to cascade heat from a continuous stage up to a heat sink. Continuous operation aids the usual constraints of long hold times and short recycle times that lead to the generally large mass of single-shot ADRs, and allows us to achieve much higher cooling power per unit mass. Our design goal is 10 microW of cooling at 50 mK while rejecting heat to a 6-10 K heat sink. The total cold mass is estimated to be less than 10 kg, including magnetic shielding of each stage. These parameters envelop the requirements for currently planned astronomy missions. The relatively high heat rejection capability allows it to operate with a mechanical cryocooler as part of a cryogen-free, low temperature cooling system. This has the advantages of long, mission life and reduced complexity and cost. At present, we have assembled a three-stage ADR that operates with a superfluid helium bath. Additional work is underway to develop magnetocaloric materials that can extend its heat rejection capability up to 10 K. This paper discusses the design and operation of the ADR, as well as interface requirements for cryocooler-based operation.

Shirron, Peter↗

NASA NTRS2015

Use of Existing CAD Models for Radiation Shielding Analysis

The utility of a radiation exposure analysis depends not only on the accuracy of the underlying particle transport code, but also on the accuracy of the geometric representations of both the vehicle used as radiation shielding mass and the phantom representation of the human form. The current NASA/Space Radiation Analysis Group (SRAG) process to determine crew radiation exposure in a vehicle design incorporates both output from an analytic High Z and Energy Particle Transport (HZETRN) code and the properties (i.e., material thicknesses) of a previously processed drawing. This geometry pre-process can be time-consuming, and the results are less accurate than those determined using a Monte Carlo-based particle transport code. The current work aims to improve this process. Although several Monte Carlo programs (FLUKA, Geant4) are readily available, most use an internal geometry engine. The lack of an interface with the standard CAD formats used by the vehicle designers limits the ability of the user to communicate complex geometries. Translation of native CAD drawings into a format readable by these transport programs is time consuming and prone to error. The Direct Accelerated Geometry -United (DAGU) project is intended to provide an interface between the native vehicle or phantom CAD geometry and multiple particle transport codes to minimize problem setup, computing time and analysis error.

Lee, K. T.↗

NASA NTRS1991

Lunar campsite concept: Space transfer concepts and analysis for exploration missions

The lunar Campsite concept responds to a perceived need to identify early manned science and exploration missions that require minimal initial funding. The Campsite concept defers the build-up of many infrastructure components without escalating total program costs. The lunar Campsite has been sized nominally for four crew for 42 days (1 lunar night and 2 lunar days), but can be modified to span two lunar nights up to 60 days. Total mission fulfillment requires five Earth-to-LEO launches, four (100 mt class launch vehicle) for the two vehicle assemblies and one (PLS or NSTS) for the crew. The lunar Campsite mission mode is tandem direct using a booster stage and a lander stage. The booster is separated from the lander after the TLI burn and is expended into the Earth's atmosphere. In the Campsite mode, the lander lands on the surface not to be returned. In the crew delivery mode, the lander is guided to a precision landing about 500 m from the Campsite, and with enough propellant to return the crew to Earth. The Campsite consists of a habitat and airlock, body mounted radiators with a surface shield, sun tracking solar arrays, and an Earth-tracking high-gain antenna. The CV is very similar to the campsite delivery vehicle. The CV does not, however, have radiators or solar arrays. The vehicle stacks are essentially common in that they utilize the same structure system and engines, the same propellant tanks, the same 'cut-out' in which the CRV and payloads are incorporated, and the same RCS locations. The booster and lander stage propellant tank propellant capacities are identical and have margins which would allow additional fueling for propulsive capture of the boost stage into Earth orbit. This contractual study was performed to identify Campsite and vehicle interfaces and vehicle requirements, and to surface issues related to the integration of the Campsite and LTV's.

Source record↗

NASA NTRS2015

Online Simulation of Radiation Track Structure Project

Space radiation comprises protons, helium and high charged and energy (HZE) particles. High-energy particles are a concern for human space flight, because they are no known options for shielding astronauts from them. When these ions interact with matter, they damage molecules and create radiolytic species. The pattern of energy deposition and positions of the radiolytic species, called radiation track structure, is highly dependent on the charge and energy of the ion. The radiolytic species damage biological molecules, which may lead to several long-term health effects such as cancer. Because of the importance of heavy ions, the radiation community is very interested in the interaction of HZE particles with DNA, notably with regards to the track structure. A desktop program named RITRACKS was developed to simulate radiation track structure. The goal of this project is to create a web interface to allow registered internal users to use RITRACKS remotely.

Plante, Ianik↗

NASA NTRS2016

A Comparison of Van Allen Belt Radiation Environment Modeling Programs: AE8/AP8 Legacy, AE9/AP9, and SPENVIS

In the space surrounding Earth there exists an active radiation environment consisting mostly of electrons and protons that have been trapped by Earths magnetic field. This radiation, also known as the Van Allen Belts, has the potential to damage man-made satellites in orbit; thus, proper precautions must be taken to shield NASA assets from this phenomenon. Data on the Van Allen Belts has been collected continuously by a multitude of space-based instruments since the beginning of space exploration. Subsequently, using theory to fill in the gaps in the collected data, computer models have been developed that take in the orbital information of a hypothetical mission and output the expected particle fluence and flux for that orbit. However, as new versions of the modeling system are released, users are left wondering how the new version differs from the old. Therefore, we performed a comparison of three different editions of the modeling system: AE8/AP8 (legacy), which is included in the model 9 graphical user interface as an option for ones calculations, AE9/AP9, and the Space Environment Information System (SPENVIS), which is an online-based form of AE8/AP8 developed by NASA and the European Space Agency that changed the code to allow the program to extrapolate data to predict fluence and flux at higher energies. Although this evaluation is still ongoing, it is predicted that the model 8 (legacy) and SPENVIS version will have identical outputs with the exception of the extended energy levels from SPENVIS, while model 9 will provide different fluences than model 8 based on additional magnetic field descriptions and on-orbit data.

Modeling Programs↗

NASA NTRS1993

Retention latch mechanism for the Wake Shield Facility

The Wake Shield Facility (WSF) is a space transportation system (STS) payload that is scheduled for launch on STS-60 in November, 1993. It is being designed, tested and integrated into the STS by Space Industries Inc. for the University of Houston's Space Vacuum Epitaxy Center, a NASA Center for the Commercial Development of Space. The WSF is composed of two main components: a cross-bay carrier and a free-flying experimental platform. The WSF's primary objective is the epitaxial growth of thin films by controlled beam techniques in the ultra-high vacuum that exists in the wake of the free-flyer. The Retention Latch Mechanism (RLM) has been developed to act as the structural interface between the free-flyer and the carrier.

Vendrely, Timothy G.↗

NASA NTRS2004

NASA Tech Briefs, September 2004

Topics covered include: Brazing SiC/SiC Composites to Metals; Composite-Material Tanks with Chemically Resistant Liners; Thermally Conductive Metal-Tube/Carbon-Composite Joints; Improved BN Coatings on SiC Fibers in SiC Matrices; Iterative Demodulation and Decoding of Non-Square QAM; Measuring Radiation Patterns of Reconfigurable Patch Antennas on Wafers; Low-Cutoff, High-Pass Digital Filtering of Neural Signals; Further Improvement in 3DGRAPE; Ground Support Software for Spaceborne Instrumentation; MER SPICE Interface; Simulating Operation of a Planetary Rover; Analyzing Contents of a Computer Cache; Discrepancy Reporting Management System; Silicone-Rubber Microvalves Actuated by Paraffin; Hydraulic Apparatus for Mechanical Testing of Nuts; Heat Control via Torque Control in Friction Stir Welding; Manufacturing High-Quality Carbon Nanotubes at Lower Cost; Setup for Visual Observation of Carbon-Nanotube Arc Process; Solution Preserves Nucleic Acids in Body-Fluid Specimens; Oligodeoxynucleotide Probes for Detecting Intact Cells; Microwave-Spectral Signatures Would Reveal Concealed Objects; Digital Averaging Phasemeter for Heterodyne Interferometry; Optoelectronic Instrument Monitors pH in a Culture Medium; Imaging of gamma-Irradiated Regions of a Crystal; Photodiode-Based, Passive Ultraviolet Dosimeters; Discrete Wavelength-Locked External Cavity Laser; Flexible Shields for Protecting Spacecraft Against Debris; Part 2 of a Computational Study of a Drop-Laden Mixing Layer; Controllable Curved Mirrors Made from Single-Layer EAP Films; and Demonstration of a Pyrotechnic Bolt-Retractor System.

Source record↗

NASA NTRSDate not supplied

Updating the Thermal Vacuum Chambers at the NASA Johnson Space Center

Chambers A and B are two large thermal vacuum chambers at Johnson Space Center which enable space simulation for unmanned and human-rated missions, respectively. With the resurgence in deep space missions for scientific research and various private commercial ventures, these chambers are expected to be used frequently for at least the next decade. For qualifying the James Webb Space Telescope, upgrades to Chamber A were performed which included the addition of a 12.5 kW refrigeration system with helium shrouds capable of simulating deep space environment and an efficient and reliable LN2 natural flow thermosiphon system for the thermal shield. Continuous improvements since then have focused on ensuring operational readiness by modernizing the data acquisition, recording, controls, and visualization systems for both chambers and clean room. These upgrades will be the focus of this paper. Controlling the Cryochambers was enhanced by moving from a 32-bit SCADA system to a 64-bit architected system. Infrastructural changes involved installing redundant power circuits, adding new servers, network switches, and including load balancing with fail-over between servers to minimize downtime. Instead of distributed servers, 3 redundant servers are used to share configurations. Configurations are now kept in a shared SQL instance making it easy to deploy and maintain. During this upgrade process many sub-systems (PLCs and NI PXI interfaces to sensors) were upgraded from the prior OPC-DA to the more secure OPC-UA protocol. Cryo-system PLCs were updated to allow Ganni cycle floating pressure calculations from any cold box to be sent to any compressor. During the project, the team recreated over 70,000 live data points, 50000 historical data points, and 4000 alarms. Finally, the graphical interfaces were upgraded to support HTML 5 in conjunction shared pages were implemented reducing the total number of webpages by over 75%. These system updates reinvigorated the previous SCADA system which had reached its end of life. The same look and feel was maintained while providing operators with an updated interface to control, troubleshoot, and record. The new system architecture is more robust and easier to maintain creating a path forward to address remaining problem points and implement additional features.

Cody Schaefer↗

NASA NTRSDate not supplied

Updating the Thermal Vacuum Chambers at the NASA Johnson Space Center

Cody Schaefer↗

NASA NTRS1988

Electrical structure and its implication across the lower- and upper-crustal settings of South India

Measurements of a large scale MMA experiment covering both the granulite and greenstone terrains of Archeans in the southern part of India is re-visited and re-analyzed. The induced field variations contain the signatures of crustal and subcrustal electrical conductivities, although substantially distorted by the sea-land interfaces and cenozoic sediments. However, through a selection of some reconnaissance profiles and temporal variations, an attempt is made to deduce whether: (1) significant differences exist between the electrical structures of the high and low grade complexes (i.e., if the electrical conductivity of the lower crust is due to minerological composition or is intrinsic to the positioning at depths greater than 15 km); (2) the probable seaward extension of the continental crust and its transition to oceanic type may also contribute (through intracrustal DC-like telluric sheets) to the induction field in addition to or rather than the sharply localized zones; (3) the observed parameters are indicative of a formal anisotropy and/or undulations in the deep crust; and (4) the postulate of relatively hotter Indian shield is reflected particularly with regard to differential metamorphism. In the last case, the crust-mantle coupling in this region - unlike other similar areas - seems to be markedly affected by the evolution of Ne-plate velocity field.

Raval, U.↗

NASA NTRSDate not supplied

Control System Development for A Zero Boil-Off Hydrogen Storage Demonstration With Two-Stage Active Cooling

A NASA team is designing and building a test article to demonstrate the long duration storage of liquid hydrogen via active cooling (cryocoolers) while implementing a two-stage cooling approach. This activity is one of a large portfolio of NASA’s Space Technology Mission Directorate funded activities which focuses on the technology maturation needed for long duration storage of cryogenic liquid in-space. The current state-of-the-art for liquid hydrogen storage on-orbit is on the order of hours while NASA’s planned missions require storage for months, or even years. To enable such a long duration, Zero Boil-Off conditions must be achieved which requires passive technologies to minimize environmental heat loads, but also active cooling to intercept and reject the remaining heat to deep space. The implementation of active cooling results in a significant amount of dry mass added to the vehicle. Utilizing a Two-Stage Cooling approach, analysis and testing to date indicates the Zero Boil-Off of liquid hydrogen can be achieved with less mass and electrical power relative to a single-stage cooling approach where only one cryocooler is used. This activity will demonstrate the fully integrated suite of technologies needed to enable the Two-Stage Cooling approach which includes Multi-Layer Insulation blankets, Low Conductivity Structures, a Tube-On-Tank Heat Exchanger, Tube-On-Shield Heat Exchanger and a Two-Stage Cryogenerator (both 90 Kelvin and 20 Kelvin) with each stage having an independently controlled circulation loop. The bulk of the heat load is intercepted by the 90 Kelvin loop via a thin foil heat exchanger internal to the insulation blankets (also known as a Broad Area Cooling Shield), with the remainder removed at cryofluid temperature (20 Kelvin) by tubes directly welded to the outer tank surface. In this paper, we examine the challenges of controlling the system, and describe the development of control algorithms and software for future testing with liquid hydrogen. The interactions between the cryofans which control circulation loop mass flow rates, electrical heaters which vary the cryocooler lift to simulate the operation of variable-lift flight units, tank heaters which can vary the overall heat load, and the effects of changes in circulation loop pressure as temperatures change, can be complex and must be well understood to maintain steady-state propellant conditions and achieve Zero Boil-Off. Parallel PID loops and watchdog programs implemented on the user interface system will help bring the systems to steady state operation and keep them at selected operating points within acceptable error, while avoiding runaway feedback loops.

cryogenics↗

NASA NTRS2021

Simulation of Landing and Take-Off Noise for Supersonic Transport Aircraft at a Conceptual Design Fidelity Level

The German Aerospace Center has launched an internal project to assess the noise impact associated with supersonic transport aircraft during approach and departure. A dedicated simulation process is established to cover all relevant disciplines, i.e., aircraft and engine design, engine installation effects, flight simulation, and system noise prediction. The core of the simulation process is comprised of methods at the complexity and fidelity level of conceptual aircraft design, i.e., typical overall aircraft design methods and a semi-empirical approach for the noise modeling. Dedicated interfaces allow to process data from high fidelity simulation that will support or even replace initial low fidelity results in the long run. All of the results shown and discussed in this study are limited to the fidelity level of conceptual design. The application of the simulation process to the NASA 55t Supersonic Technology Concept Aeroplane, i.e., based on non-proprietary data for this vehicle, yields similar noise level predictions when compared to the published NASA results. This is used as an initial feasibility check of the new process and confirms the underlying methods and models. Such an initial verification of the process is understood as an essential step due to the lack of available noise data for supersonic transport aircraft in general. The advantageous effect of engine noise shielding on the resulting system noise is demonstrated based on predicted level time histories and certification noise levels. After this initial verification, the process is applied to evaluate a conceptual supersonic transport design based on a PhD thesis with two engines mounted under the wing, which is referred to as aircraft TWO. Full access to this vehicle’s design and performance data allows to investigate the influence of flight procedures on the resulting noise impact along approach and departure. These noise results are then assembled according to proposed Federal Aviation Agency regulations in their Notice of Proposed Rulemaking, e.g., speed limitations, for Supersonic transport noise certification and the regulations from Noise Chapters of the Annex 16 from the International Civil Aviation Organization in order to evaluate the resulting levels as a function of the flight procedure.

noise↗

NASA NTRS2005

Wireless Acoustic Measurement System

A prototype wireless acoustic measurement system (WAMS) is one of two main subsystems of the Acoustic Prediction/Measurement Tool, which comprises software, acoustic instrumentation, and electronic hardware combined to afford integrated capabilities for predicting and measuring noise emitted by rocket and jet engines. The other main subsystem is described in "Predicting Rocket or Jet Noise in Real Time" (SSC-00215-1), which appears elsewhere in this issue of NASA Tech Briefs. The WAMS includes analog acoustic measurement instrumentation and analog and digital electronic circuitry combined with computer wireless local-area networking to enable (1) measurement of sound-pressure levels at multiple locations in the sound field of an engine under test and (2) recording and processing of the measurement data. At each field location, the measurements are taken by a portable unit, denoted a field station. There are ten field stations, each of which can take two channels of measurements. Each field station is equipped with two instrumentation microphones, a micro-ATX computer, a wireless network adapter, an environmental enclosure, a directional radio antenna, and a battery power supply. The environmental enclosure shields the computer from weather and from extreme acoustically induced vibrations. The power supply is based on a marine-service lead-acid storage battery that has enough capacity to support operation for as long as 10 hours. A desktop computer serves as a control server for the WAMS. The server is connected to a wireless router for communication with the field stations via a wireless local-area network that complies with wireless-network standard 802.11b of the Institute of Electrical and Electronics Engineers. The router and the wireless network adapters are controlled by use of Linux-compatible driver software. The server runs custom Linux software for synchronizing the recording of measurement data in the field stations. The software includes a module that provides an intuitive graphical user interface through which an operator at the control server can control the operations of the field stations for calibration and for recording of measurement data. A test engineer positions and activates the WAMS. The WAMS automatically establishes the wireless network. Next, the engineer performs pretest calibrations. Then the engineer executes the test and measurement procedures. After the test, the raw measurement files are copied and transferred, through the wireless network, to a hard disk in the control server. Subsequently, the data are processed into 1/3-octave spectrograms.

Anderson, Paul D.↗