NASA's New Shortcut to Fusion Power: Lattice Confinement Fusion Eliminates Massive Magnets and Powerful Lasers
IEEE Spectrum, 2022
PHYSICISTS FIRST SUSPECTED MORE THAN A CENTURY AGO that the fusing of hydrogen into helium powers... more PHYSICISTS FIRST SUSPECTED MORE THAN A CENTURY AGO that the fusing of hydrogen into helium powers the sun. It took researchers many years to unravel the secrets by which lighter elements are smashed together into heavier ones inside stars, releasing energy in the process. And scientists and engineers have continued to study the sun's fusion process in hopes of one day using nuclear fusion to generate heat or electricity. But the prospect of meeting our energy needs this way remains elusive. The extraction of energy from nuclear fission, by contrast, happened relatively quickly. Fission in uranium was discovered in 1938, in Germany, and it was only four years later that the first nuclear “pile” was constructed in Chicago, in 1942.
A numerical analysis methodology and solutions of the interaction between the power stream and mu... more A numerical analysis methodology and solutions of the interaction between the power stream and multiply-connected multi-cavity sealed secondary flow fields are presented. Flow solutions for a multi-cavity experimental rig were computed and compared with experimental data of Daniels and Johnson. The flow solutions illustrate the complex coupling between the main-path and the cavity flows as well as outline the flow thread that exists throughout the subplatform multiple cavities and seals. The analysis also shows that the de-coupled solutions on single cavities is inadequate. The present results show trends similar to the T-700 engine data that suggests the changes in the CDP seal altered the flow fields throughout the engine and affected the engine performance.
Phillips stripping reactions in the highly screened environment. Neutron spectroscopy was conduct... more Phillips stripping reactions in the highly screened environment. Neutron spectroscopy was conducted using calibrated leadshielded liquid (EJ-309) and plastic (stilbene) scintillator detectors. The data support the theoretical analysis in a companion paper, predicting fusion reactions and subsequent reactions in the highly screened environment.
Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. ... more Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the Lead Center for NASA's scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA's institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types:
48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2012
NASA is developing a new docking system to support future space exploration missions to low Earth... more NASA is developing a new docking system to support future space exploration missions to low Earth orbit, the Moon, and other destinations. A key component of this system is the seal at the main docking interface which inhibits the loss of cabin air once docking is complete. Depending on the mission, the seal must be able to dock in either a seal-on-flange or seal-on-seal configuration. Seal-on-flange mating would occur when a docking system equipped with a seal docks to a system with a flat metal flange. This would occur when a vehicle docks to a node on the International Space Station. Seal-on-seal mating would occur when two docking systems equipped with seals dock to each other. Two types of seal designs were identified for this application: Gask-O-seals and multi-piece seals. Both types of seals had a pair of seal bulbs to satisfy the redundancy requirement. A series of performance assessments and comparisons were made between the candidate seal designs indicating that they meet the requirements for leak rate and compression and adhesion loads under a range of operating conditions. Other design factors such as part count, integration into the docking system tunnel, seal-on-seal mating, and cost were also considered leading to the selection of the multi-piece seal design for the new docking system. The results of this study can be used by designers of future docking systems and other habitable volumes to select the seal design best-suited for their particular application. Nomenclature AO atomic oxygen CBM Common Berthing Mechanism GRC Glenn Research Center ISS International Space Station kip one thousand lb f LEO low Earth orbit SOF seal-on-flange SOS seal-on-seal 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 26 19a. NAME OF RESPONSIBLE PERSON
44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008
Silicone rubber seals are being considered for a number of interfaces on NASA's Crew Exploration ... more Silicone rubber seals are being considered for a number of interfaces on NASA's Crew Exploration Vehicle (CEV). Some of these joints include the docking system, hatches, and heat shield-to-back shell interface. A large diameter molded silicone seal is being developed for the Low Impact Docking System (LIDS) that forms an effective seal between the CEV and International Space Station (ISS) and other future Constellation Program spacecraft. Seals between the heat shield and back shell prevent high temperature reentry gases from leaking into the interface. Silicone rubber seals being considered for these locations have inherent adhesive tendencies that would result in excessive forces required to separate the joints if left unchecked. This paper summarizes adhesion assessments for both as-received and adhesion-mitigated seals for the docking system and the heat shield interface location. Three silicone elastomers were examined: Parker Hannifin S0899-50 and S0383-70 compounds, and Esterline ELA-SA-401 compound. For the docking system application various levels of exposure to atomic oxygen (AO) were evaluated. Moderate AO treatments did not lower the adhesive properties of S0899-50 sufficiently. However, AO pretreatments of approximately 10 20 atoms/cm 2 did lower the adhesion of S0383-70 and ELA-SA-401 to acceptable levels. For the heat shield-to-back shell interface application, a fabric covering was also considered. Molding Nomex fabric into the heat shield pressure seal appreciably reduced seal adhesion for the heat shield-to-back shell interface application.
42nd AIAA Aerospace Sciences Meeting and Exhibit, 2004
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to
34th Structures, Structural Dynamics and Materials Conference, 1993
A test fixture for measuring the dynamic performance of candidate high-temperature engine seal co... more A test fixture for measuring the dynamic performance of candidate high-temperature engine seal concepts has been installed at NASA Lewis Research Center. The test fixture has been designed to evaluate seal concepts under development for advanced hypersonic engines, such as those being considered for the National Aerospace Plane (HASP). The fixture can measure dynamic seal leakage performance from room temperature up to 840'C (1550'') and au pressure differentials up to 690 kPa (100 psi). Performance of the seals can be measured while sealing against flat or distorted walls. In the fixture two seals are preloaded against the sides of a 30 cm (1 ft) long saber that slides transverse to the axis of the seals, simulating the scrubbing motion anticipated in these engines. This report covers the capabilities of this test fixture along with preliminary data showing the dependence of seal leakage performance on high temperature cycling. Research Engineer, member AIAA Resident Research Associate Copyright C 1993 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The US. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposes. All other rights are reserved by the copyright owner.
Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end... more Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end of the resonator is investigated numerically. It is well known that the resonant frequencies and the nonlinear standing waveform in an acoustical resonator strongly depend on the resonator geometry. A quasi-Newton type scheme was used to find optimized axisymmetric resonator shapes achieving the maximum pressure compression ratio with an acceleration of constant amplitude. The acoustical field was solved using a one-dimensional model, and the resonance frequency shift and hysteresis effects were obtained through an automation scheme based on continuation method. Results are presented for optimizing three types of geometry: a cone, a horn-cone and a half cosineshape. For each type, different optimized shapes were found when starting with different initial guesses. Further, the one-dimensional model was modified to study the effect of an axisymmetric central blockage on the nonlinear standing wave.
44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008
A universal docking system is being developed by the National Aeronautics and Space Administratio... more A universal docking system is being developed by the National Aeronautics and Space Administration (NASA) to support future space exploration missions to low Earth orbit (LEO), to the moon, and to Mars. The candidate docking seals for the system are a composite design consisting of elastomer seal bulbs molded into the front and rear sides of a metal ring. The test specimens were sub-scale seals with two different elastomer cross-sections and a 12-in. outside diameter. The seal assemblies were mated in elastomer seal-on-metal plate and elastomer seal-onelastomer seal configurations. The seals were manufactured from S0383-70 silicone elastomer compound. Nominal and off-nominal joint configurations were examined. Both the compression load required to mate the seals and the leak rate observed were recorded while the assemblies were subjected to representative docking system operating temperatures of-58, 73, and 122 °F (-50, 23, and 50 °C). Both the loads required to fully compress the seals and their leak rates were directly proportional to the test temperature. Nomenclature AO atomic oxygen CVCM collected volatile condensable materials LEO low Earth orbit LIDS Low Impact Docking System MMOD micrometeoroid and orbital debris NASA National Aeronautics and Space Administration RTD resistance temperature detector TML total mass loss UV ultraviolet radiation REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Future hypersonic vehicles require high temperature, dynamic seals in advanced hypersonic engines... more Future hypersonic vehicles require high temperature, dynamic seals in advanced hypersonic engines and on the vehicle airframe to seal the perimeters of movable panels, flaps, and doors. Current seals do not meet the demanding requirements of these applications, so NASA Glenn Research Center is developing improved designs to overcome these shortfalls. An advanced ceramic wafer seal design has shown promise in meeting these needs. Results from a design of experiments study performed on this seal revealed that several installation variables played a role in determining the amount of leakage past the seals. Lower leakage rates were achieved by using a tighter groove width around the seals, a higher seal preload, a tighter wafer height tolerance, and a looser groove length. During flow testing, a seal activating pressure acting behind the wafers combined with simulated vibrations to seat the seals more effectively against the sealing surface and produce lower leakage rates. A seal geometry study revealed comparable leakage for full-scale wafers with 0.125 and 0.25 in. thicknesses. For applications in which lower part counts are desired, fewer 0.25-in.-thick wafers may be able to be used in place of 0.125-in.-thick wafers while achieving similar performance. Tests performed on wafers with a rounded edge (0.5 in. radius) in contact with the sealing surface resulted in flow rates twice as high as those for wafers with a flat edge. Half-size wafers had leakage rates approximately three times higher than those for full-size wafers.
42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2006
The National Aeronautics and Space Administration is currently designing the Crew Exploration Veh... more The National Aeronautics and Space Administration is currently designing the Crew Exploration Vehicle (CEV) as a replacement for the Space Shuttle for manned missions to the International Space Station, as a command module for returning astronauts to the moon, and as an earth reentry vehicle for the final leg of manned missions to the moon and Mars. The CEV resembles a scaled-up version of the heritage Apollo vehicle; however, the CEV seal requirements are different than those from Apollo because of its different mission requirements. A review is presented of some of the seals used on the Apollo spacecraft for the gap between the heat shield and backshell and for penetrations through the heat shield, docking hatches, windows, and the capsule pressure hull.
A new test chamber and precision hydraulic actuation system were incorporated into an active clea... more A new test chamber and precision hydraulic actuation system were incorporated into an active clearance control (ACC) test rig at NASA Glenn Research Center. Using the improved system, a fastacting, mechanically-actuated, ACC concept was evaluated at engine simulated temperatures and pressure differentials up to 1140 °F and 120 psig, on the basis of secondary seal leakage and kinematic controllability. During testing, the ACC concept tracked a simulated flight clearance transient profile at 1140 °F, 120 psig, with a maximum error of only 0.0012 in. Comparison of average dynamic leakage of the system with average static leakage did not show significant differences between the two operating conditions. Calculated effective clearance values for the rig were approximately 0.0002 in. at 120 psig, well below the industry specified effective clearance threshold of 0.001 in. Nomenclature φ Flow Factor, () psia lbm/s R° X Distance between the inner diameter of the face seal and inner edge of the flexure seal, in. δ flow Effective clearance where flow is choked, in. A flow Area where flow is choked, in. 2 C Circumference of seal test section, in. m Measured mass flow rate, lbm/s R Gas constant for air, 53.3 lbf-ft/lbm-°R T Temperature, °R g c Gravitational constant, 32.2 lbm-ft/lbf-s 2 P s Supply pressure, psia
46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2010
NASA is developing advanced space-rated vacuum seals in support of future space exploration missi... more NASA is developing advanced space-rated vacuum seals in support of future space exploration missions to low-Earth orbit and other destinations. These seals may be 50 to 60 in. (127 to 152 cm) in diameter and must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions to the International Space Station or the Moon. Seal compression loads must be below prescribed limits so as not to overload the mechanisms that compress them during docking or mating, and seal adhesion forces must be low to allow two mated systems to separate when required. NASA Glenn Research Center has developed a new test apparatus to measure leak rates and compression and adhesion loads of candidate full-scale seals under simulated thermal, vacuum, and engagement conditions. Tests can be performed in seal-on-seal or seal-on-flange configurations at temperatures from-76 to 140 °F (-60 to 60 °C) under operational pressure gradients. Nominal and off-nominal mating conditions (e.g., incomplete seal compression) can also be simulated. This paper describes the main design features of the test apparatus as well as techniques used to overcome some of the design challenges. Nomenclature gpm gallons per minute
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Future reusable launch vehicles will require advanced structural seals. Seal protection will be n... more Future reusable launch vehicles will require advanced structural seals. Seal protection will be needed for reentry vehicle control surfaces such as moveable flaps and elevons and hypersonic engine edge and hinge line seals. These seals must remain in sealing contact with opposing surfaces over multiple missions, even though the seal gap may be opening and closing due to thermal and structural loads. To meet this requirement seals must be resilient. Case Western Reserve University is working with NASA's Glenn Research Center to develop more resilient, high temperature seals and preload devices. This study details the creation of finite element models for two high temperature resilient structures: canted coil springs and knitted spring tubes. Each model was verified by comparison to experimental results of compression tests performed at Glenn Research Center. The models reveal the locations of stress concentration, and they show the force versus displacement relationship for each structure. These models provide a means for optimizing the design of canted coil springs and knitted spring tubes to advance NASA's high temperature seal capabilities. x
40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2004
Trade names or manufacturers' names are used in this report for identification only. This usage d... more Trade names or manufacturers' names are used in this report for identification only. This usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration.
High temperature seals are required for advanced hypersonic airframe applications. In this study,... more High temperature seals are required for advanced hypersonic airframe applications. In this study, both spring tube thermal barriers and innovative wafer seal systems were evaluated under relevant hypersonic test conditions (temperatures, pressures, etc.) via high temperature compression testing and room temperature flow assessments. Thermal barriers composed of a René 41 spring tube filled with Saffil insulation and overbraided with a Nextel 312 sheath showed acceptable performance at 1500 °F in both short term and longer term compression testing. Nextel 440 thermal barriers with René 41 spring tubes and Saffil insulation demonstrated good compression performance up to 1750 °F. A silicon nitride wafer seal/compression spring system displayed excellent load performance at temperatures as high as 2200 °F and exhibited room temperature leakage values that were only 1/3 those for the spring tube rope seals. For all seal candidates evaluated, no significant degradation in leakage resistance was noted after high temperature compression testing. In addition to these tests, a superalloy seal suitable for dynamic seal applications was optimized through finite element techniques. I. Nomenclature σ max Maximum stress E Young's modulus ω max Maximum half-deflection on end t Material thickness L Length of beam element REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
Available electronically at http://gltrs.grc.nasa.gov Trade names and trademarks are used in this... more Available electronically at http://gltrs.grc.nasa.gov Trade names and trademarks are used in this report for identification only. Their usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration. Level of Review: This material has been technically reviewed by technical management.
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Knitted metallic spring tubes are the structural backbones that provide resiliency in control sur... more Knitted metallic spring tubes are the structural backbones that provide resiliency in control surface seals for use on current and future reusable space launch vehicles. Control surface seals fill the space between movable control surfaces such as body flaps, rudders and elevons, and the static body structures to which they are attached. These seals must remain in continuous contact with opposing surfaces to prevent the ingestion of damaging hot gases encountered during atmospheric re-entry. The Inconel X-750 spring tube utilized in the baseline control surface seal shows significant resiliency loss when compressed at temperatures as low as 1200 • F. High temperature compression testing and microstructural analysis show that creep is the dominant deformation mechanism leading to permanent set and resiliency loss in tested spring tube samples. Additional evaluation using a structured design of experiments approach shows that spring tube performance, primarily high temperature resiliency, can be enhanced through material substitution of Rene 41 alloy (for the baseline Inconel X-750 material) when coupled with specialized thermal processing.
NASA's New Shortcut to Fusion Power: Lattice Confinement Fusion Eliminates Massive Magnets and Powerful Lasers
IEEE Spectrum, 2022
PHYSICISTS FIRST SUSPECTED MORE THAN A CENTURY AGO that the fusing of hydrogen into helium powers... more PHYSICISTS FIRST SUSPECTED MORE THAN A CENTURY AGO that the fusing of hydrogen into helium powers the sun. It took researchers many years to unravel the secrets by which lighter elements are smashed together into heavier ones inside stars, releasing energy in the process. And scientists and engineers have continued to study the sun's fusion process in hopes of one day using nuclear fusion to generate heat or electricity. But the prospect of meeting our energy needs this way remains elusive. The extraction of energy from nuclear fission, by contrast, happened relatively quickly. Fission in uranium was discovered in 1938, in Germany, and it was only four years later that the first nuclear “pile” was constructed in Chicago, in 1942.
A numerical analysis methodology and solutions of the interaction between the power stream and mu... more A numerical analysis methodology and solutions of the interaction between the power stream and multiply-connected multi-cavity sealed secondary flow fields are presented. Flow solutions for a multi-cavity experimental rig were computed and compared with experimental data of Daniels and Johnson. The flow solutions illustrate the complex coupling between the main-path and the cavity flows as well as outline the flow thread that exists throughout the subplatform multiple cavities and seals. The analysis also shows that the de-coupled solutions on single cavities is inadequate. The present results show trends similar to the T-700 engine data that suggests the changes in the CDP seal altered the flow fields throughout the engine and affected the engine performance.
Phillips stripping reactions in the highly screened environment. Neutron spectroscopy was conduct... more Phillips stripping reactions in the highly screened environment. Neutron spectroscopy was conducted using calibrated leadshielded liquid (EJ-309) and plastic (stilbene) scintillator detectors. The data support the theoretical analysis in a companion paper, predicting fusion reactions and subsequent reactions in the highly screened environment.
Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. ... more Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the Lead Center for NASA's scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA's institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types:
48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2012
NASA is developing a new docking system to support future space exploration missions to low Earth... more NASA is developing a new docking system to support future space exploration missions to low Earth orbit, the Moon, and other destinations. A key component of this system is the seal at the main docking interface which inhibits the loss of cabin air once docking is complete. Depending on the mission, the seal must be able to dock in either a seal-on-flange or seal-on-seal configuration. Seal-on-flange mating would occur when a docking system equipped with a seal docks to a system with a flat metal flange. This would occur when a vehicle docks to a node on the International Space Station. Seal-on-seal mating would occur when two docking systems equipped with seals dock to each other. Two types of seal designs were identified for this application: Gask-O-seals and multi-piece seals. Both types of seals had a pair of seal bulbs to satisfy the redundancy requirement. A series of performance assessments and comparisons were made between the candidate seal designs indicating that they meet the requirements for leak rate and compression and adhesion loads under a range of operating conditions. Other design factors such as part count, integration into the docking system tunnel, seal-on-seal mating, and cost were also considered leading to the selection of the multi-piece seal design for the new docking system. The results of this study can be used by designers of future docking systems and other habitable volumes to select the seal design best-suited for their particular application. Nomenclature AO atomic oxygen CBM Common Berthing Mechanism GRC Glenn Research Center ISS International Space Station kip one thousand lb f LEO low Earth orbit SOF seal-on-flange SOS seal-on-seal 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 26 19a. NAME OF RESPONSIBLE PERSON
44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008
Silicone rubber seals are being considered for a number of interfaces on NASA's Crew Exploration ... more Silicone rubber seals are being considered for a number of interfaces on NASA's Crew Exploration Vehicle (CEV). Some of these joints include the docking system, hatches, and heat shield-to-back shell interface. A large diameter molded silicone seal is being developed for the Low Impact Docking System (LIDS) that forms an effective seal between the CEV and International Space Station (ISS) and other future Constellation Program spacecraft. Seals between the heat shield and back shell prevent high temperature reentry gases from leaking into the interface. Silicone rubber seals being considered for these locations have inherent adhesive tendencies that would result in excessive forces required to separate the joints if left unchecked. This paper summarizes adhesion assessments for both as-received and adhesion-mitigated seals for the docking system and the heat shield interface location. Three silicone elastomers were examined: Parker Hannifin S0899-50 and S0383-70 compounds, and Esterline ELA-SA-401 compound. For the docking system application various levels of exposure to atomic oxygen (AO) were evaluated. Moderate AO treatments did not lower the adhesive properties of S0899-50 sufficiently. However, AO pretreatments of approximately 10 20 atoms/cm 2 did lower the adhesion of S0383-70 and ELA-SA-401 to acceptable levels. For the heat shield-to-back shell interface application, a fabric covering was also considered. Molding Nomex fabric into the heat shield pressure seal appreciably reduced seal adhesion for the heat shield-to-back shell interface application.
42nd AIAA Aerospace Sciences Meeting and Exhibit, 2004
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to
34th Structures, Structural Dynamics and Materials Conference, 1993
A test fixture for measuring the dynamic performance of candidate high-temperature engine seal co... more A test fixture for measuring the dynamic performance of candidate high-temperature engine seal concepts has been installed at NASA Lewis Research Center. The test fixture has been designed to evaluate seal concepts under development for advanced hypersonic engines, such as those being considered for the National Aerospace Plane (HASP). The fixture can measure dynamic seal leakage performance from room temperature up to 840'C (1550'') and au pressure differentials up to 690 kPa (100 psi). Performance of the seals can be measured while sealing against flat or distorted walls. In the fixture two seals are preloaded against the sides of a 30 cm (1 ft) long saber that slides transverse to the axis of the seals, simulating the scrubbing motion anticipated in these engines. This report covers the capabilities of this test fixture along with preliminary data showing the dependence of seal leakage performance on high temperature cycling. Research Engineer, member AIAA Resident Research Associate Copyright C 1993 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The US. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposes. All other rights are reserved by the copyright owner.
Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end... more Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end of the resonator is investigated numerically. It is well known that the resonant frequencies and the nonlinear standing waveform in an acoustical resonator strongly depend on the resonator geometry. A quasi-Newton type scheme was used to find optimized axisymmetric resonator shapes achieving the maximum pressure compression ratio with an acceleration of constant amplitude. The acoustical field was solved using a one-dimensional model, and the resonance frequency shift and hysteresis effects were obtained through an automation scheme based on continuation method. Results are presented for optimizing three types of geometry: a cone, a horn-cone and a half cosineshape. For each type, different optimized shapes were found when starting with different initial guesses. Further, the one-dimensional model was modified to study the effect of an axisymmetric central blockage on the nonlinear standing wave.
44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2008
A universal docking system is being developed by the National Aeronautics and Space Administratio... more A universal docking system is being developed by the National Aeronautics and Space Administration (NASA) to support future space exploration missions to low Earth orbit (LEO), to the moon, and to Mars. The candidate docking seals for the system are a composite design consisting of elastomer seal bulbs molded into the front and rear sides of a metal ring. The test specimens were sub-scale seals with two different elastomer cross-sections and a 12-in. outside diameter. The seal assemblies were mated in elastomer seal-on-metal plate and elastomer seal-onelastomer seal configurations. The seals were manufactured from S0383-70 silicone elastomer compound. Nominal and off-nominal joint configurations were examined. Both the compression load required to mate the seals and the leak rate observed were recorded while the assemblies were subjected to representative docking system operating temperatures of-58, 73, and 122 °F (-50, 23, and 50 °C). Both the loads required to fully compress the seals and their leak rates were directly proportional to the test temperature. Nomenclature AO atomic oxygen CVCM collected volatile condensable materials LEO low Earth orbit LIDS Low Impact Docking System MMOD micrometeoroid and orbital debris NASA National Aeronautics and Space Administration RTD resistance temperature detector TML total mass loss UV ultraviolet radiation REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Future hypersonic vehicles require high temperature, dynamic seals in advanced hypersonic engines... more Future hypersonic vehicles require high temperature, dynamic seals in advanced hypersonic engines and on the vehicle airframe to seal the perimeters of movable panels, flaps, and doors. Current seals do not meet the demanding requirements of these applications, so NASA Glenn Research Center is developing improved designs to overcome these shortfalls. An advanced ceramic wafer seal design has shown promise in meeting these needs. Results from a design of experiments study performed on this seal revealed that several installation variables played a role in determining the amount of leakage past the seals. Lower leakage rates were achieved by using a tighter groove width around the seals, a higher seal preload, a tighter wafer height tolerance, and a looser groove length. During flow testing, a seal activating pressure acting behind the wafers combined with simulated vibrations to seat the seals more effectively against the sealing surface and produce lower leakage rates. A seal geometry study revealed comparable leakage for full-scale wafers with 0.125 and 0.25 in. thicknesses. For applications in which lower part counts are desired, fewer 0.25-in.-thick wafers may be able to be used in place of 0.125-in.-thick wafers while achieving similar performance. Tests performed on wafers with a rounded edge (0.5 in. radius) in contact with the sealing surface resulted in flow rates twice as high as those for wafers with a flat edge. Half-size wafers had leakage rates approximately three times higher than those for full-size wafers.
42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2006
The National Aeronautics and Space Administration is currently designing the Crew Exploration Veh... more The National Aeronautics and Space Administration is currently designing the Crew Exploration Vehicle (CEV) as a replacement for the Space Shuttle for manned missions to the International Space Station, as a command module for returning astronauts to the moon, and as an earth reentry vehicle for the final leg of manned missions to the moon and Mars. The CEV resembles a scaled-up version of the heritage Apollo vehicle; however, the CEV seal requirements are different than those from Apollo because of its different mission requirements. A review is presented of some of the seals used on the Apollo spacecraft for the gap between the heat shield and backshell and for penetrations through the heat shield, docking hatches, windows, and the capsule pressure hull.
A new test chamber and precision hydraulic actuation system were incorporated into an active clea... more A new test chamber and precision hydraulic actuation system were incorporated into an active clearance control (ACC) test rig at NASA Glenn Research Center. Using the improved system, a fastacting, mechanically-actuated, ACC concept was evaluated at engine simulated temperatures and pressure differentials up to 1140 °F and 120 psig, on the basis of secondary seal leakage and kinematic controllability. During testing, the ACC concept tracked a simulated flight clearance transient profile at 1140 °F, 120 psig, with a maximum error of only 0.0012 in. Comparison of average dynamic leakage of the system with average static leakage did not show significant differences between the two operating conditions. Calculated effective clearance values for the rig were approximately 0.0002 in. at 120 psig, well below the industry specified effective clearance threshold of 0.001 in. Nomenclature φ Flow Factor, () psia lbm/s R° X Distance between the inner diameter of the face seal and inner edge of the flexure seal, in. δ flow Effective clearance where flow is choked, in. A flow Area where flow is choked, in. 2 C Circumference of seal test section, in. m Measured mass flow rate, lbm/s R Gas constant for air, 53.3 lbf-ft/lbm-°R T Temperature, °R g c Gravitational constant, 32.2 lbm-ft/lbf-s 2 P s Supply pressure, psia
46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2010
NASA is developing advanced space-rated vacuum seals in support of future space exploration missi... more NASA is developing advanced space-rated vacuum seals in support of future space exploration missions to low-Earth orbit and other destinations. These seals may be 50 to 60 in. (127 to 152 cm) in diameter and must exhibit extremely low leak rates to ensure that astronauts have sufficient breathable air for extended missions to the International Space Station or the Moon. Seal compression loads must be below prescribed limits so as not to overload the mechanisms that compress them during docking or mating, and seal adhesion forces must be low to allow two mated systems to separate when required. NASA Glenn Research Center has developed a new test apparatus to measure leak rates and compression and adhesion loads of candidate full-scale seals under simulated thermal, vacuum, and engagement conditions. Tests can be performed in seal-on-seal or seal-on-flange configurations at temperatures from-76 to 140 °F (-60 to 60 °C) under operational pressure gradients. Nominal and off-nominal mating conditions (e.g., incomplete seal compression) can also be simulated. This paper describes the main design features of the test apparatus as well as techniques used to overcome some of the design challenges. Nomenclature gpm gallons per minute
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Future reusable launch vehicles will require advanced structural seals. Seal protection will be n... more Future reusable launch vehicles will require advanced structural seals. Seal protection will be needed for reentry vehicle control surfaces such as moveable flaps and elevons and hypersonic engine edge and hinge line seals. These seals must remain in sealing contact with opposing surfaces over multiple missions, even though the seal gap may be opening and closing due to thermal and structural loads. To meet this requirement seals must be resilient. Case Western Reserve University is working with NASA's Glenn Research Center to develop more resilient, high temperature seals and preload devices. This study details the creation of finite element models for two high temperature resilient structures: canted coil springs and knitted spring tubes. Each model was verified by comparison to experimental results of compression tests performed at Glenn Research Center. The models reveal the locations of stress concentration, and they show the force versus displacement relationship for each structure. These models provide a means for optimizing the design of canted coil springs and knitted spring tubes to advance NASA's high temperature seal capabilities. x
40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2004
Trade names or manufacturers' names are used in this report for identification only. This usage d... more Trade names or manufacturers' names are used in this report for identification only. This usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration.
High temperature seals are required for advanced hypersonic airframe applications. In this study,... more High temperature seals are required for advanced hypersonic airframe applications. In this study, both spring tube thermal barriers and innovative wafer seal systems were evaluated under relevant hypersonic test conditions (temperatures, pressures, etc.) via high temperature compression testing and room temperature flow assessments. Thermal barriers composed of a René 41 spring tube filled with Saffil insulation and overbraided with a Nextel 312 sheath showed acceptable performance at 1500 °F in both short term and longer term compression testing. Nextel 440 thermal barriers with René 41 spring tubes and Saffil insulation demonstrated good compression performance up to 1750 °F. A silicon nitride wafer seal/compression spring system displayed excellent load performance at temperatures as high as 2200 °F and exhibited room temperature leakage values that were only 1/3 those for the spring tube rope seals. For all seal candidates evaluated, no significant degradation in leakage resistance was noted after high temperature compression testing. In addition to these tests, a superalloy seal suitable for dynamic seal applications was optimized through finite element techniques. I. Nomenclature σ max Maximum stress E Young's modulus ω max Maximum half-deflection on end t Material thickness L Length of beam element REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188),
Available electronically at http://gltrs.grc.nasa.gov Trade names and trademarks are used in this... more Available electronically at http://gltrs.grc.nasa.gov Trade names and trademarks are used in this report for identification only. Their usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration. Level of Review: This material has been technically reviewed by technical management.
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Knitted metallic spring tubes are the structural backbones that provide resiliency in control sur... more Knitted metallic spring tubes are the structural backbones that provide resiliency in control surface seals for use on current and future reusable space launch vehicles. Control surface seals fill the space between movable control surfaces such as body flaps, rudders and elevons, and the static body structures to which they are attached. These seals must remain in continuous contact with opposing surfaces to prevent the ingestion of damaging hot gases encountered during atmospheric re-entry. The Inconel X-750 spring tube utilized in the baseline control surface seal shows significant resiliency loss when compressed at temperatures as low as 1200 • F. High temperature compression testing and microstructural analysis show that creep is the dominant deformation mechanism leading to permanent set and resiliency loss in tested spring tube samples. Additional evaluation using a structured design of experiments approach shows that spring tube performance, primarily high temperature resiliency, can be enhanced through material substitution of Rene 41 alloy (for the baseline Inconel X-750 material) when coupled with specialized thermal processing.
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Papers by Bruce Steinetz