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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Fluid Dynamics of a Pressure Reducing Inlet

Instruments for the monitoring of hazardous gases in and near the space shuttle collect sample gas at pressures on the order of one atmosphere and analyze their properties in an ultra-high vacuum by means of a quadrupole-mass-spectrometer partial pressure transducer. Sampling systems for such devices normally produce the required pressure reduction through combinations of vacuum pumps, fluid Tees and flow restrictors (e.g. orifices, sintered metal frits or capillaries). The present work presents an analytical model of the fluid dynamics of such a pressure reduction system which enables the calculation of the pressure in the receiver vessal in terms of system parameters known from the specifications for a given system (e.g. rated pumping speeds of the pumping hardware and the diameters of two orifices situated in two branches of a fluid Tee). The resulting formulas will expedite the fine tuning of instruments now under development and the design of later generations of such devices.

Russell, John M.↗
NASA NTRSDate not supplied

Evolving the Design of a Volcanic Monitoring UAS over Several Flight Campaigns

A multi-organization effort has been underway for several years to develop and validate the use of small unmanned aircraft systems (UAS) for volcanic monitoring. The overall goal is to develop the aircraft, supporting systems, concept of operations, scientific payloads and regulatory framework to allow regular and reliable sampling in challenging and dynamic atmospheric conditions around volcanic summits. Central to this effort has been the development and refinement of the “S2” aircraft, which contains a tightly integrated system consisting of the airframe, avionics, and payload sensors specifically designed to measure atmospheric properties around volcanic plumes. The aircraft has a 3-meter wingspan and can carry a 2.3 kg payload for up to 100 km while operating at altitudes up to 6,000 m. To date, the system has been flown in Costa Rica to sample CO2 gases around Turrialba Volcano (Costa Rica), in Hawaii to assess the 2018 eruption of Kīlauea with several different sensors, and is currently planned for deployment in Alaska for gas sampling and photogrammetry at Makushin Volcano. Before and after each deployment, all aspects of the system and concept of operations (CONOPS) were extensively examined and modified to improve the safety and performance. This has culminated in the upcoming deployment which will fly up to 30 km - beyond visual line of sight for the first time. This expansion of the operational range through additional safety features and redundancy will pave the way for monitoring and accessing areas that were previously very difficult to reach from both a technical and regulatory perspective. These developments can be extended to a variety of missions requiring UAS for atmospheric sampling, specifically ones that would benefit from beyond visual line of sight operations or flights into harsh or difficult atmospheric environments.

UAS↗
NASA NTRS1974

The continuous measurement of hydrogen chloride in the ambient atmosphere using the dual isotope infrared absorption technique

The results of a program to develop a prototype gas filter correlation NDIR analyzer capable of providing the required HCl measurement capability, while maintaining an adequate rejection of any other gases anticipated in the atmosphere are presented. Examples of the performance of the prototype analyzer are presented which show an rms noise equivalent concentration of 0.06 ppm of HCl was achieved while maintaining an electronically determined 10% to 90% time response to gas samples of about 2 seconds. No measureable response was observed to CO2, CO, and H2O while maintaining an adequate rejection of the hydrocarbons, for example CH4 and n-hexane. The experiments were performed which demonstrate that the span stability of the HCl gas filter correlation analyzer is unaffected by the presence of water vapor and which support the belief that the incorporation of a relatively open-volume, multiple path sample cell into the instrument would enable ground station as well as airborne measurements of trace quantities of HCl in the ambient atmosphere to be performed.

Williams, K. G.↗
NASA NTRS1999

Mars Solar Balloon Landed Gas Chromatograph Mass Spectrometer

A Mars surface lander Gas Chromatograph Mass Spectrometer (GCMS) is described to measure the chemical composition of abundant and trace volatile species and isotope ratios for noble gases and other elements. These measurements are relevant to the study of atmospheric evolution and past climatic conditions. A Micromission plan is under study where a surface package including a miniaturized GCMS would be delivered to the surface by a solar heated hot air balloon based system. The balloon system would be deployed about 8 km above the surface of Mars, wherein it would rapidly fill with Martian atmosphere and be heated quickly by the sun. The combined buoyancy and parachuting effects of the solar balloon result in a surface package impact of about 5 m/sec. After delivery of the package to the surface, the balloon would ascend to about 4 km altitude, with imaging and magnetometry data being taken for the remainder of the daylight hours as the balloon is blown with the Martian winds. Total atmospheric entry mass of this mission is estimated to be approximately 50 kg, and it can fit as an Ariane 5 piggyback payload. The GCMS would obtain samples directly from the atmosphere at the surface and also from gases evolved from solid phase material collected from well below the surface with a Sample Acquisition and Transport Mechanism (SATM). The experiment envisioned in the Mars Micromission described would obtain samples from a much greater depth of up to one meter below the surface, and would search for organic molecules trapped in ancient stratified layers well below the oxidized surface. Insitu instruments on upcoming NASA missions working in concert with remote sensing measurement techniques have the potential to provide a more detailed investigation of mineralogy and the extent of simple volatiles such as CO2 and H2O in surface and subsurface solid phase materials. Within the context of subsequent mission opportunities such as those provided by the Ariane 5 piggyback payload based Micromissions, it is essential to implement an even broader chemical analysis and to enable a significant extension of previous isotope measurements. Such a development would enhance the presently very active study of questions of atmospheric evolution and loss and past climatic conditions. The method selected to implement this program can be based on well-established mass spectrometry techniques. Sampled gas is chemically and physically processed to separate the gas mixture into components using gas chromatograph and related enrichment techniques. This allows trace species to be identified and reveals isotopic distributions in many cases with improved precision. Samples of interest, such as organic molecules, may lie deep below the highly oxidized surface layer and the suggested program includes enhanced sampling techniques to measure volatiles preserved in solid phase material deep below the surface as well as gas from the well mixed atmosphere.

Mahaffy, P.↗
NASA NTRS1978

Emission measurements for a lean premixed propane/air system at pressures up to 30 atmospheres

The emissions of a lean premixed system of propane/air were measured in a flametube apparatus. Tests were conducted at inlet temperatures of 600K and 800K and pressures of 10 atm and 30 atm over a range of equivalence ratios. The data obtained were combined with previous data taken in the same apparatus to correlate nitrogen oxide emissions with operating conditions. Sampling probe design was found to have a pronounced effect on measured CO levels but did not influence measurements. The most effective probe tested was one which combined thermal and pressure quenching of the gas sample.

Roffe, G.↗
NASA NTRSDate not supplied

Analytical and Experimental Demonstration of an Alternate Mixing Performance Metric for High-Speed Fuel Mixing Studies

To experimentally assess the fuel/air mixing performance of high-speed fuel injectors, one-dimensional metrics that quantify the degree of mixing completeness downstream of the fuel injection location are required. The most accurate assessment of mixing performance is achieved with the mixing efficiency parameter. In order to experimentally determine the mixing efficiency parameter, the spatial distributions of both mass flux and fuel mass fraction must be measured. In-stream gas sampling techniques are commonly used to measure the fuel mass fraction distribution; however, the mass flux distribution is not easily determined because it requires the measurement of three independent aerothermodynamic variables in addition to the gas composition. Therefore, to experimentally determine the mixing efficiency parameter, the spatial distributions of four independent properties must be measured, with each property generally requiring its own unique probe. Because of this difficulty, it is commonly assumed that alternate metrics, which rely solely on the fuel distribution, are good indicators of mixing performance. However, since these alternate metrics do not provide a mass flux-weighted measure of mixing completeness, they can lead to incorrect conclusions being drawn about the mixing performance of the studied fuel injector configuration. Recognizing this shortcoming, this work proposes two new alternate mixing performance metrics that are easier to obtain than the mixing efficiency parameter. The analytical development of the new metrics, as well as their application to relevant CFD and experimental data of high-speed fuel injector configurations, is presented in this work. For two different experiments, the new metrics are shown to provide an excellent representation of the true mass flux-weighted mixing performance, unlike the traditionally-used alternatives. The results presented herein suggest that the new metrics can serve as accurate surrogates for mixing efficiency in future high-speed fuel/air mixing studies.

Cody R Ground↗
NASA NTRSDate not supplied

Hydrogen Sensor via Plasma Techniques Development

Currently, NASA Kennedy Space Center’s Exploration Ground Systems (EGS) uses liquid hydrogen (LH 2 ) as fuel for launches and ensures hydrogen is no longer in the fill lines by sampling gas into a controlled environment. Then they use a catalytic sensor that detects when hydrogen interacts with oxygen. However, this procedure requires repeatedly backfilling and flushing with helium, which can be wasteful during a global helium shortage and expensive for each sampling port. Therefore, the team at KSC set out to establish proof-of-concept of a plasma-based hydrogen sensor that is anaerobic – and can in fact detect in most environments and below atmospheric pressures – and with a small footprint and more sensitive than other hydrogen sensors currently on the market. The technology development was done by testing known concentrations of hydrogen in argon gas fed through a vacuum cube containing an electrode feedthrough at varying pressures. The resultant emission spectra were recorded with a fiber optic spectrometer and analyzed to determine the instrument's accuracy. Throughout testing, efforts were made to prove the off-the-shelf capabilities of the setup. The traditional high voltage AC-power source was switched to an affordable, handheld plasma lighter. Additionally, the spectrometer was supplemented with a double photodiode circuit to take targeted measurements of the Balmer-α and - β lines in the hydrogen spectrum. From this, we established a proof of concept sensor. SLS required it to detect as low as 100 ppm whereas we detected hydrogen in concentrations as low as 50 ppm and in an anaerobic environment. * Work supported by NASA Kennedy Space Center’s Science Mission Directorate Innovative Research and Development Fund.

Plasma↗
NASA NTRSDate not supplied

Hydrogen Sensor via Plasma Techniques Development

Currently, NASA Kennedy Space Center’s Exploration Ground Systems (EGS) uses liquid hydrogen (LH2) as fuel for launches and ensures hydrogen is no longer in the fill lines by sampling gas into a controlled environment. Then they use a catalytic sensor that detects when hydrogen interacts with oxygen. However, this procedure requires repeatedly backfilling and flushing with helium, which can be wasteful during a global helium shortage and expensive for each sampling port. Therefore, the team at KSC set out to establish proof-of-concept of a plasma-based hydrogen sensor that is anaerobic – and can in fact detect in most environments and below atmospheric pressures – and with a small footprint and more sensitive than other hydrogen sensors currently on the market. The technology development was done by testing known concentrations of hydrogen in argon gas fed through a vacuum cube containing an electrode feedthrough at varying pressures. The resultant emission spectra were recorded with a fiber optic spectrometer and analyzed to determine the instrument's accuracy. Throughout testing, efforts were made to prove the off-the-shelf capabilities of the setup. The traditional high voltage AC-power source was switched to an affordable, handheld plasma lighter. Additionally, the spectrometer was supplemented with a double photodiode circuit to take targeted measurements of the Balmer-α and - β lines in the hydrogen spectrum. From this, we established a proof of concept sensor. SLS required it to detect as low as 100 ppm whereas we detected hydrogen in concentrations as low as 50 ppm and in an anaerobic environment.

plasma↗
NASA NTRS1974

High-response on-line gas analysis system for hydrogen-reaction combustion products

The results of testing an on-line quadrupole gas analyzer system are reported. Gas samples were drawn from the exhaust of a hydrogen-oxygen-nitrogen rocket which simulated the flow composition and dynamics at the combustor exit of a supersonic combustion ramjet engine. System response time of less than 50 milliseconds was demonstrated, with analytical accuracy estimated to be + or - 5 percent. For more complex chemical systems with interfering atom patterns, analysis would be more difficult. A cooled-gas pyrometer probe was evaluated as a total temperature indicator and as the primary mass flow measuring element for the total sample flow rate.

Metzler, A. J.↗
NASA NTRS1986

The chemical shock tube as a tool for studying high-temperature chemical kinetics

Although the combustion of hydrocarbons is our primary source of energy today, the chemical reactions, or pathway, by which even the simplest hydro-carbon reacts with atmospheric oxygen to form CO2 and water may not always be known. Furthermore, even when the reaction pathway is known, the reaction rates are always under discussion. The shock tube has been an important and unique tool for building a data base of reaction rates important in the combustion of hydrocarbon fuels. The ability of a shock wave to bring the gas sample to reaction conditions rapidly and homogeneously makes shock-tube studies of reaction kinetics extremely attractive. In addition to the control and uniformity of reaction conditions achieved with shock-wave methods, shock compression can produce gas temperatures far in excess of those in conventional reactors. Argon can be heated to well over 10 000 K, and temperatures around 5000 K are easily obtained with conventional shock-tube techniques. Experiments have proven the validity of shock-wave theory; thus, reaction temperatures and pressures can be calculated from a measurement of the incident shock velocity. A description is given of the chemical shock tube and auxiliary equipment and of two examples of kinetic experiments conducted in a shock tube.

Brabbs, Theodore A.↗
NASA NTRS2016

Optical Breath Gas Extravehicular Activity Sensor for the Advanced Portable Life Support System

The function of the infrared gas transducer used during extravehicular activity (EVA) in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation portable life support system (PLSS) requires highly accurate CO2 sensing technology with performance beyond that presently in use on the International Space Station extravehicular mobility unit (EMU). Further, that accuracy needs to be provided over the full operating pressure range of the suit (3 to 25 psia). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode (LD) sensor based on infrared absorption spectroscopy is being developed for this purpose by Vista Photonics, Inc. Version 1.0 prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The prototypes were upgraded with more sophisticated communications and faster response times to version 2.0 and delivered to JSC in July 2012. The sensors incorporate a laser diode based CO2 channel that also includes an incidental water vapor (humidity) measurement. The prototypes are controlled digitally with an field-programmable gate array microcontroller architecture. Based on the results of the iterative instrument development, further prototype development and testing of instruments were performed leveraging the lessons learned where feasible. The present development extends and upgrades the earlier hardware for the advanced PLSS 2.5 prototypes for testing at JSC. The prototypes provide significantly enhanced accuracy for water vapor measurement and eliminate wavelength drift affecting the earlier versions. Various improvements to the electronics and gas sampling are currently being advanced including the companion development of engineering development units that will ultimately be capable of radiation tolerance. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU.

Wood, William R.↗
NASA NTRSDate not supplied

Quantitation of Trace Water in ISS Atmosphere Samples Recovered from CO2-Removal Systems

As crewed spaceflight continues to push the limits of exploration, instruments and hardware used to maintain and monitor crew and vehicle health must become more integrated, reliable, and efficient. By combining a carbon dioxide (CO2) removal system with a resource recovery system like a Sabatier or Bosch reactor, the waste gas from the removal system can be converted into valuable resources that help reduce reliance on ground resupply. Due to the high-pressure nature of the Sabatier and Bosch reactions, the vent gas from most CO2 removal systems will need to be compressed before it can be processed. In order to prevent condensation in the compressor of the recovery system, it is critical to ensure that the vent stream from the CO2 removal system does not contain an excess of water. There are currently three different CO2 removal systems that are being developed as candidates for exploration missions. Each of these systems will be evaluated as a technology demonstration on ISS, and vent gas samples will be collected in Summa sampling canisters fitted with Entech valves. Due to the need to measure low levels of water in these samples, it was not possible to use the current ISS miniature grab sample containers (GSCs) to collect these samples. The Summa containers, which were used to collect archive samples during Shuttle missions, have a different surface treatment that makes it possible to measure the low levels of water in samples collected in these containers. This paper will provide some background on the CO2 removal systems being evaluated for exploration missions as well as results from ground-based testing of the current miniature GSCs and Summa canisters. Details on the development of the analytical method and the plan for preparing the canisters that will be used for in-flight sampling are also discussed.

Steven W Beck↗
NASA NTRSDate not supplied

Quantitation of Trace Water in ISS Atmosphere Samples Recovered from CO2-Removal Systems

As crewed spaceflight continues to push the limits of exploration, instruments and hardware used to maintain and monitor crew and vehicle health, must become more integrated, reliable, and efficient. By combining a carbon dioxide (CO2) removal system with a resource recovery system like a Sabatier or Bosch reactor, the waste gas from the removal system can be converted into valuable resources that help reduce reliance on ground resupply. Due to the high-pressure nature of the Sabatier and Bosch reactions, the vent gas from most CO2 removal systems will need to be compressed before it can be processed. In order to prevent condensation in the compressor of the recovery system, it is critical to ensure that the vent stream from the CO2 removal system does not contain an excess of water. There are currently two different CO2 removal systems that are being developed as candidates for exploration missions. Each of these systems will be evaluated as a technology demonstration on ISS, and vent gas samples will be collected in Summa sampling canisters fitted with Entech valves for ground analysis. Due to the need to measure low levels of water in these samples, it was not possible to use the current ISS mini-grab sample containers (m-GSC) to collect these samples. The Summa containers, which were used to collect archive samples during Shuttle missions, have a different surface treatment that makes it possible to measure the low levels of water in samples collected in these containers. This paper will provide some background on the CO2 removal systems being evaluated for exploration missions as well as results from ground-based testing of the Summa canisters. Details on the development of the analytical method and the plan for preparing the canisters that will be used for in-flight sampling are also discussed.

William M. King↗
NASA NTRS1997

Sample Diluter for Detecting Hypergolic Propellants and Other Toxic or Hazardous Gases

Hardware was developed to dilute vapor samples of purged hypergolic propellants (with air) into the range of existing instruments for detection of such toxic vapors. Since these detectors are normally used to monitor at the threshold limit value (TLV), most do not have quantitative capability at percent levels which relate to lower explosion limit (LEL) and fire hazards. For example, the upper limits of Energetic Sciences (ESI) 6000 series detectors used at KSC are 200 parts per million (ppm) for monomethyl hydrazine (MMH) and 500 ppm for nitrogen dioxide (NO2) arising from decomposition of nitrogen tetroxide (N2O4). Orbiter Processing Facility (OPF) personnel servicing Shuttle thrusters need to measure up to 250 ppm MMH and 7,500 ppm NO2 with portable, intrinsically safe instruments. Our objective was to quickly fabricate a sample diluter out of existing materials as a temporary measure while other parallel efforts were conducted to provide a commercial or in-house-developed instrument to detect high propellant levels. A 3 to 1 diluter would bring 500 ppm MMH into the range of the existing fuel ESI, and a 30 to 1 diluter would do the same for NO2. In this way, familiar equipment already available would be used, resulting in minimal paperwork, safety, and training impacts and low cost. An MMH vapor sample-diluter was constructed from a 1/4-inch Kynar tee, along with specially designed lengths of sample and dilution tubing. The sample line was 3 feet of Bev-A-Line 4, 1/4-inch tube leading to the straight run of the tee. The side run of the tee had a 17-inch length of Bev-A-Line 4, 1/4-inch tube, for nominal 3 to 1 dilution. A gas sample bag was prepared and assayed at 113 ppm ppm MMH, and diluted vapor samples were assayed at 39.5 ppm, or a measured dilution of 2.9 to 1. For NO2, a 316 stainless steel (SS) 1/8-inch tee with 49.5 inches of coiled, 1/8-inch outside diameter (OD) 316 SS tubing was used as the sampling end of the dilution system. The side run of the tee was open. The measured dilution ratio, based on the input value of 6,480 ppm NO2, and the average output value of 233 ppm, was 28 to 1. Thus, sample-diluters were successful in diluting concentrated hypergolic propellant vapors, both MMH and N2O4 into the ranges of existing TLV detectors.

Barile, R. G.↗
NASA NTRS1997

Sample Diluter for Detecting Hypergolic Propellants and Other Toxic or Hazardous Gases

Hardware was developed to dilute vapor samples of purged hypergolic propellants (with air) into the range of existing instruments for detection of such toxic vapors. Since these detectors are normally used to monitor at the threshold limit value (TLV), most do not have quantitative capability at percent levels which relate to lower explosion limit (LEL) and fire hazards. For example, the upper limits of Energetic Sciences (ESI) 6000 series detectors used at KSC are 200 parts per million (ppm) for monomethyl hydrazine (MMH) and 500 ppm for nitrogen dioxide (NO2) arising from decomposition of nitrogen tetroxide (N2O4). Orbiter Processing Facility (OPF) personnel servicing Shuttle thrusters need to measure up to 250 ppm MMH and 7500 ppm NO2 with portable, intrinsically safe instruments. Our objective was to quickly fabricate a sample diluter out of existing materials as a temporary measure while other parallel efforts were conducted to provide a commercial or in-house-developed instrument to detect high propellant levels. A 3 to 1 diluter would bring 500 ppm MMH into the range of the existing fuel ESI, and a 30 to 1 diluter would do the same for NO2. In this way, familiar equipment already available would be used, resulting in minimal paperwork, safety, and training impacts and low cost. An MMH vapor sample-diluter was constructed from a 1/4-inch Kynar tee, along with specially designed lengths of sample and dilution tubing. The sample line was 3 feet of Bev-A-Line 4, 1/4 inch tube leading to the straight run of the tee. The side run of the tee had a 17-inch length of Bev-A-Line 4, 1/4-inch tube, for nominal 3 to 1 dilution. A gas sample bag was prepared and assayed at 113 ppm MMH, and diluted vapor sarnples were assayed at 39.5 ppm, or a measured dilution of 2.9 to 1. For NO2, a 316 stainless steel (SS) 1/8-inch tee with 49.5 inches of coiled, 1/8-inch outside diameter (OD) 316 SS tubing was used as the sarnpling end of the dilution system. The side run of the tee was open. The measured dilution ratio, based on the input value of 6,480 ppm NO2 and the average output value of 233 ppm, was 28 to 1. Thus, sample-diluters were successful in diluting concentrated hypergolic propellant vapors, both MMH and N2O4, into the ranges of existing TLV detectors.

Barile, R. G.↗
NASA NTRS2010

Low-Dead-Volume Inlet for Vacuum Chamber

Gas introduction from near-ambient pressures to high vacuum traditionally is accomplished either by multi-stage differential pumping that allows for very rapid response, or by a capillary method that allows for a simple, single-stage introduction, but which often has a delayed response. Another means to introduce the gas sample is to use the multi-stage design with only a single stage. This is accomplished by using a very small conductance limit. The problem with this method is that a small conductance limit will amplify issues associated with dead -volume. As a result, a high -vacuum gas inlet was developed with low dead -volume, allowing the use of a very low conductance limit interface. Gas flows through the ConFlat flange at a relatively high flow rate at orders of magnitude greater than through the conductance limit. The small flow goes through a conductance limit that is a double-sided ConFlat.

Naylor, Guy↗
NASA NTRS2011

Low-Dead-Volume Inlet for Vacuum Chamber

Gas introduction from near-ambient pressures to high vacuum traditionally is accomplished either by multi-stage differential pumping that allows for very rapid response, or by a capillary method that allows for a simple, single-stage introduction, but which often has a delayed response. Another means to introduce the gas sample is to use the multi-stage design with only a single stage. This is accomplished by using a very small conductance limit. The problem with this method is that a small conductance limit will amplify issues associated with dead-volume. As a result, a high-vacuum gas inlet was developed with low dead-volume, allowing the use of a very low conductance limit interface. Gas flows through the ConFlat flange at a relatively high flow rate at orders of magnitude greater than through the conductance limit. The small flow goes through a conductance limit that is a double-sided ConFlat.

Naylor, Guy↗
NASA NTRS2013

Cryogenic Liquid Sample Acquisition System for Remote Space Applications

There is a need to acquire autonomously cryogenic hydrocarbon liquid sample from remote planetary locations such as the lakes of Titan for instruments such as mass spectrometers. There are several problems that had to be solved relative to collecting the right amount of cryogenic liquid sample into a warmer spacecraft, such as not allowing the sample to boil off or fractionate too early; controlling the intermediate and final pressures within carefully designed volumes; designing for various particulates and viscosities; designing to thermal, mass, and power-limited spacecraft interfaces; and reducing risk. Prior art inlets for similar instruments in spaceflight were designed primarily for atmospheric gas sampling and are not useful for this front-end application. These cryogenic liquid sample acquisition system designs for remote space applications allow for remote, autonomous, controlled sample collections of a range of challenging cryogenic sample types. The design can control the size of the sample, prevent fractionation, control pressures at various stages, and allow for various liquid sample levels. It is capable of collecting repeated samples autonomously in difficult lowtemperature conditions often found in planetary missions. It is capable of collecting samples for use by instruments from difficult sample types such as cryogenic hydrocarbon (methane, ethane, and propane) mixtures with solid particulates such as found on Titan. The design with a warm actuated valve is compatible with various spacecraft thermal and structural interfaces. The design uses controlled volumes, heaters, inlet and vent tubes, a cryogenic valve seat, inlet screens, temperature and cryogenic liquid sensors, seals, and vents to accomplish its task.

Mahaffy, Paul↗