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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

SU-E-J-166: Sensitivity of Clinically Relevant Dosimetric Parameters to Contouring Uncertainty During Post Implant Dosimetry of Prostate Permanent Seed Implants

Purpose: There is a strong evidence relating post-implant dosimetry for permanent seed prostate brachytherpy to local control rates. The delineation of the prostate on CT images, however, represents a challenge as it is difficult to confidently identify the prostate borders from soft tissue surrounding it. This study aims at quantifying the sensitivity of clinically relevant dosimetric parameters to prostate contouring uncertainty. Methods: The post-implant CT images and plans for a cohort of 43 patients, who have received I–125 permanent prostate seed implant in our centre, were exported to MIM Symphony LDR brachytherapy treatment planning system (MIM Software Inc., Cleveland, OH). The prostate contours in post-implant CT images were expanded/contracted uniformly for margins of ±1.00mm, ±2.00mm, ±3.00mm, ±4.00mm and ±5.00mm (±0.01mm). The values for V100 and D90 were extracted from Dose Volume Histograms for each contour and compared. Results: The mean value of V100 and D90 was obtained as 92.3±8.4% and 108.4±12.3% respectively (Rx=145Gy). V100 was reduced by −3.2±1.5%, −7.2±3.0%, −12.8±4.0%, −19.0±4.8%, − 25.5±5.4% for expanded contours of prostate with margins of +1mm, +2mm, +3mm, +4mm, and +5mm, respectively, while it was increased by 1.6±1.2%, 2.4±2.4%, 2.7±3.2%, 2.9±4.2%, 2.9±5.1% for the contracted contours. D90 was reduced by −6.9±3.5%, −14.5±6.1%, −23.8±7.1%, − 33.6±8.5%, −40.6±8.7% and increased by 4.1±2.6%, 6.1±5.0%, 7.2±5.7%, 8.1±7.3% and 8.1±7.3% for the same set of contours. Conclusion: Systematic expansion errors of more than 1mm may likely render a plan sub-optimal. Conversely contraction errors may Result in labeling a plan likely as optimal. The use of MRI images to contour the prostate should results in better delineation of prostate organ which increases the predictive value of post-op plans. Since observers tend to overestimate the prostate volume on CT, compared with MRI, the impact of the contouring uncertainty on V100 and D90 fortunately, has a conservative effect of underestimating the prostate coverage.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-287: Dose Verification On the Variation of Target Volume and Organ at Risk in Preradiation Chemotherapy IMRT for Nasopharyngeal Cancer

Purpose: To quantify the target volume and organ at risk of nasopharyngeal carcinoma (NPC) patients with preradiation chemotherapy based on CT scanned during intensity-modulated radiotherapy (IMRT), and recalculate the dose distribution. Methods: Seven patients with NPC and preradiation chemotherapy, treated with IMRT (35 to 37 fractions) were reviewed. Repeat CT scanning was required to all of the patients during the radiotherapy, and the number of repeat CTs varies from 2 to 6. The plan CT and repeat CT were generated by different CT scanner. To ensure crespectively on the same IMPT plan. The real dose distribution was calculated by deformable registration and weighted method in Raystation (v 4.5.1). The fraction of each dose is based on radiotherapy record. The volumetric and dose differences among these images were calculated for nascIpharyngeal tumor and retro-pharyngeal lymph nodes (GTV-NX), neck lymph nodes(GTV-ND), and parotid glands. Results: The volume variation in GTV-NX from CT1 to CT2 was 1.15±3.79%, and in GTV-LN −0.23±4.93%. The volume variation in left parotid from CT1 to CT2 was −6.79±11.91%, and in right parotid −3.92±8.80%. In patient 2, the left parotid volume were decreased remarkably, as a Result, the V30 and V40 of it were increased as well. Conclusion: The target volume of patients with NPC varied lightly during IMRT. It shows that preradiation chemotherapy can control the target volume variation and perform a good dose repeatability. Also, the decreasing volume of parotid in some patient might increase the dose of it, which might course potential complications.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-323: A Post-Mastectomy Radiation Therapy Dose Distribution Study Using Nanodots and Films

Purpose: In post-mastectomy radiation therapy (RT), skin dose must be accurately estimated to assess skin reactions such as erythema, desquamation and necrosis. Planning systems cannot always provide accurate dosimetry for target volumes distal to skin. Therefore, in-vivo dosimetry is necessary. A female anthropomorphic phantom was used with optically stimulated luminescence dosimeters (nanoDots) to measure dose to chest wall skin. In addition, EBT2 films was employed to measure dose to left lung and heart in post-mastectomy RT. Methods: Films and nanoDots were calibrated under full buildup conditions at 100cm SAD for 6MV photons. Five pieces of films were placed between slabs of Rando phantom to assess dose to left lung and heart. Two layers of 0.5cm thick bolus were used to cover the whole left chest. Six pairs of nanoDots were placed at medical and lateral aspects on the bolus surface, between the 0.5cm bolus layers, and under the bolus. Three control nanoDots were placed on chest wall to quantify imaging dose. The phantom was CT scanned with all dosimeters in place, and treatment planning was performed with tangential fields (200cGy). All dosimeters were contoured on CT and dose was extracted. NanoDots were read using nanoDot reader and films were scanned using film scanner. The measured and calculated doses were tabulated. Results: Dose to 12 nanoDots were evaluated. Dose variance for surface nanoDots were +3.8%, +2.7%, −5% and −9.8%. Those at lateral positions, with greater beam obliquity had larger variance than the medial positions. A similar trend was observed for other nanoDots (Table1). Point doses from films for heart and the left lung were 112.7cGy and 108.7cGy, with +10.2% and +9.04% deviation from calculated values, respectively. Conclusion: Dosimetry provided by the advanced planning system was verified using NanoDots and films. Both nanoDots and films provided good estimation of dose distribution in post-mastectomy RT.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1989

An algebraic homotopy method for generating quasi-three-dimensional grids for high-speed configurations

A fast and versatile procedure for algebraically generating boundary conforming computational grids for use with finite-volume Euler flow solvers is presented. A semi-analytic homotopic procedure is used to generate the grids. Grids generated in two-dimensional planes are stacked to produce quasi-three-dimensional grid systems. The body surface and outer boundary are described in terms of surface parameters. An interpolation scheme is used to blend between the body surface and the outer boundary in order to determine the field points. The method, albeit developed for analytically generated body geometries is equally applicable to other classes of geometries. The method can be used for both internal and external flow configurations, the only constraint being that the body geometries be specified in two-dimensional cross-sections stationed along the longitudinal axis of the configuration. Techniques for controlling various grid parameters, e.g., clustering and orthogonality are described. Techniques for treating problems arising in algebraic grid generation for geometries with sharp corners are addressed. A set of representative grid systems generated by this method is included. Results of flow computations using these grids are presented for validation of the effectiveness of the method.

Moitra, Anutosh↗
NASA NTRS1990

PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 4: Maintenance document (version 3.0)

The Maintenance Document Version 3.0 is a guide to the PAN AIR software system, a system which computes the subsonic or supersonic linear potential flow about a body of nearly arbitrary shape, using a higher order panel method. The document describes the overall system and each program module of the system. Sufficient detail is given for program maintenance, updating, and modification. It is assumed that the reader is familiar with programming and CRAY computer systems. The PAN AIR system was written in FORTRAN 4 language except for a few CAL language subroutines which exist in the PAN AIR library. Structured programming techniques were used to provide code documentation and maintainability. The operating systems accommodated are COS 1.11, COS 1.12, COS 1.13, and COS 1.14 on the CRAY 1S, 1M, and X-MP computing systems. The system is comprised of a data base management system, a program library, an execution control module, and nine separate FORTRAN technical modules. Each module calculates part of the posed PAN AIR problem. The data base manager is used to communicate between modules and within modules. The technical modules must be run in a prescribed fashion for each PAN AIR problem. In order to ease the problem of supplying the many JCL cards required to execute the modules, a set of CRAY procedures (PAPROCS) was created to automatically supply most of the JCL cards. Most of this document has not changed for Version 3.0. It now, however, strictly applies only to PAN AIR version 3.0. The major changes are: (1) additional sections covering the new FDP module (which calculates streamlines and offbody points); (2) a complete rewrite of the section on the MAG module; and (3) strict applicability to CRAY computing systems.

Purdon, David J.↗
NASA NTRS2014

High Intensity Exercise Countermeasures does not Prevent Orthostatic Intolerance Following Prolonged Bed Rest

Approximately 20% of Space Shuttle astronauts became presyncopal during operational stand and 80deg head‐up tilt tests, and the prevalence of orthostatic intolerance increases after longer missions. Greater than 60% of the US astronauts participating in Mir and early International Space Station missions experienced presyncope during post‐flight tilt tests, perhaps related to limitations of the exercise hardware that prevented high intensity exercise training until later ISS missions. The objective of this study was to determine whether an intense resistive and aerobic exercise countermeasure program designed to prevent cardiovascular and musculoskeletal deconditioning during 70 d of bed rest (BR), a space flight analog, would protect against post‐BR orthostatic intolerance. METHODS Twenty‐six subjects were randomly assigned to one of three groups: non‐exercise controls (n=11) or one of two exercise groups (ExA, n=8; ExB, n=7). Both ExA and ExB groups performed the same resistive and aerobic exercise countermeasures during BR, but one exercise group received testosterone supplementation while the other received a placebo during BR in a double‐blinded fashion. On 3 d/wk, subjects performed lower body resistive exercise and 30 min of continuous aerobic exercise (≥75% max heart rate). On the other 3 d/wk, subjects performed only highintensity, interval‐style aerobic exercise. Orthostatic intolerance was assessed using a 15‐min 80 head‐up tilt test performed 2 d (BR‐2) before and on the last day of BR (BR70). Plasma volume was measured using carbon monoxide rebreathing on BR‐3 and before rising on the first recovery day (BR+0). The code for the exercise groups has not been broken, and results are reported here without group identification. RESULTS Only one subject became presyncopal during tilt testing on BR‐2, but 7 of 11 (63%) controls, 3 of 8 (38%) ExA, and 4 of 7 (57%) ExB subjects were presyncopal on BR70. Survival analysis of post‐BR tilt tests revealed no differences (p=0.77) between groups. Plasma volume (absolute or relative to body mass index) decreased (p<0.001) from pre to post‐BR, with no differences between groups. CONCLUSIONS These preliminary results corroborate previous reports that the performance of a vigorous exercise countermeasure protocol during BR, even with testosterone supplementation, does not protect against orthostatic intolerance or plasma volume loss. Preventing post‐BR orthostatic intolerance may require additional countermeasures, such as orthostatic stress during BR or end‐of‐BR fluid infusion.

Platts, Steven H.↗
DOE OSTI2016

Nodal Clearance Rate and Long-Term Efficacy of Individualized Sentinel Node–Based Pelvic Intensity Modulated Radiation Therapy for High-Risk Prostate Cancer

Purpose: To assess the efficacy of individual sentinel node (SN)-guided pelvic intensity modulated radiation therapy (IMRT) by determining nodal clearance rate [(n expected nodal involvement − n observed regional recurrences)/n expected nodal involvement] in comparison with surgically staged patients. Methods and Materials: Data on 475 high-risk prostate cancer patients were examined. Sixty-one consecutive patients received pelvic SN-based IMRT (5 × 1.8 Gy/wk to 50.4 Gy [pelvic nodes + individual SN] and an integrated boost with 5 × 2.0 Gy/wk to 70.0 Gy to prostate + [base of] seminal vesicles) and neo-/adjuvant long-term androgen deprivation therapy; 414 patients after SN–pelvic lymph node dissection were used to calculate the expected nodal involvement rate for the radiation therapy sample. Biochemical control and overall survival were estimated for the SN-IMRT patients using the Kaplan-Meier method. The expected frequency of nodal involvement in the radiation therapy group was estimated by imputing frequencies of node-positive patients in the surgical sample to the pattern of Gleason, prostate-specific antigen, and T category in the radiation therapy sample. Results: After a median follow-up of 61 months, 5-year OS after SN-guided IMRT reached 84.4%. Biochemical control according to the Phoenix definition was 73.8%. The nodal clearance rate of SN-IMRT reached 94%. Retrospective follow-up evaluation is the main limitation. Conclusions: Radiation treatment of pelvic nodes individualized by inclusion of SNs is an effective regional treatment modality in high-risk prostate cancer patients. The pattern of relapse indicates that the SN-based target volume concept correctly covers individual pelvic nodes. Thus, this SN-based approach justifies further evaluation, including current dose-escalation strategies to the prostate in a larger prospective series.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

Mechanical responses of architected boron carbide-aluminum lattice composites fabricated via reactive metallic infiltration of hierarchical pore structures

The incorporation of micro and nanoscale constituents in a hierarchical order improves mechanical properties of bulk structures while inducing controlled deformation. However, these features have seldomly been applied to the fabrication of cermet materials due to manufacturing constraints. Here, overcoming previous limitations, boron carbide cermets with embedded aluminum lattices were produced using a combination of additive manufacturing and gelcasting techniques. Kelvin cell and octet truss scaffolds were printed, cast and burned out so the negative volume could be infiltrated with metal to form an architected cermet. Computed microtomography scans reveal full aluminum infiltration of the volume with high fidelity to the target architecture. Equibiaxial flexural tests showed localized crack propagation in lattice-reinforced cermets and that samples with imbedded architecture required nearly double the energy for complete failure. Overall, the addition of an internal aluminum lattice limits abrupt fracture of the composite and provides a method for tuning its mechanical response with architected ratios of metal to ceramic.

36 MATERIALS SCIENCE↗
NASA NTRS1975

Sinter of uniform, predictable, blemish-free nickel plaque for large aerospace nickel cadmium cells

A series of nickel slurry compositions were tested. Important slurry parameters were found to be the nature of the binder, a pore former and the method of mixing. A slow roll mixing which is non-turbulent successfully eliminated entrapped air so that bubbles and pockets were avoided in the sinter. A slurry applicator was developed which enabled an equal quantity of slurry to be applied to both sides of the grid. Sintering in a furnace having a graded atmosphere characteristic, ranging from oxidizing to strongly reducing, improved adhesion of porous sinter to grid and resulted in a uniform welding of nickel particles to each other throughout the plaque. Sintering was carried out in a horizontal furnace having three heating zones and 16 heating control circuits. Tests used for plaque evaluation include (1) appearance, (2) grid location and adhesion, (3) mechanical strength, (4) thickness, (5) weight per unit area, (6) void volume per unit area, (7) surface area and (8) electrical resistance. Plaque material was impregnated using Heliotek proprietary processes and 100 AH cells were fabricated.

Seiger, H. N.↗
DOE OSTI2016

SU-G-JeP3-13: Use of Volumetric Indices to Study the Viability of Respiratory Gating in Conjunction with Abdominal Compression in the Management of Non-Small Cell Lung Cancer Tumors Using Stereotactic Body Radiation Therapy Under the Conditions of Controlled Breathing

Purpose: AAPM TG-76 report advises lung patients experiencing tumor motion >5mm to use some form of motion management with even smaller limit for complex/special procedures like SBRT. Generally, either respiratory gating or abdominal compression is used for motion management. In this retrospective study, we are using an innovative index, Volumetric Indices (VI) = (GTVnn AND GTV{sub 50+}Xmm)/(GTVnn) to quantify how much of the tumor remains within 1, 2, and 3mm margins throughout the breathing cycle using GTV{sub 50+}Xmm margin on GTV{sub 50}[nn=0,10,20,…90]. Using appropriate limits, VI can provide tumor motion information and to check if RPM gates could have been used in conjunction with abdominal compression to better manage tumor motion. Methods: 64 SBRT patients with a total of 67 lung tumors were studied. 4DCT scans were taken, fully capturing tumor motion throughout the 10 phases of the breathing cycle. For each phase, Gross Tumor Volume (GTV) was segmented and appropriates structures were defined to determine VI values. For the 2mm margin, VI values less than 0.95 for peripheral lesions and 0.97 for central lesions indicate tumor movement greater than 4mm. VI values for 1mm and 3mm margins were also analyzed signifying tumor motion of 2mm & 6mm, respectively. Results: Of the 64 patients, 35 (55%) had motion greater than 4mm & could have benefited from respiratory gating. For 5/8 (63%) middle lobe lesions, 21/27 (78%) lower lobe lesions, and 10/32 (31%) upper lobe lesions, gating could have resulted in smaller ITV. 32/55 (58%) peripheral lesions and 4/12 (33%) central lesions could have had gating. Average ITV decreased by 1.25cc (11.43%) and average VI increased by 0.11. Conclusion: Out of 64 patients, 55% exhibited motion greater than 4mm even with abdominal compression. Even with abdominalcompression, lung tumors can move >4mm as the degree of pressure which a patient can tolerate, is patient specific.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TH-CD-209-10: Scanning Proton Arc Therapy (SPArc) - The First Robust and Delivery-Efficient Spot Scanning Proton Arc Therapy

Purpose: To develop a delivery-efficient proton spot-scanning arc therapy technique with robust plan quality. Methods: We developed a Scanning Proton Arc(SPArc) optimization algorithm integrated with (1)Control point re-sampling by splitting control point into adjacent sub-control points; (2)Energy layer re-distribution by assigning the original energy layers to the new sub-control points; (3)Energy layer filtration by deleting low MU weighting energy layers; (4)Energy layer re-sampling by sampling additional layers to ensure the optimal solution. A bilateral head and neck oropharynx case and a non-mobile lung target case were tested. Plan quality and total estimated delivery time were compared to original robust optimized multi-field step-and-shoot arc plan without SPArc optimization (Arcmulti-field) and standard robust optimized Intensity Modulated Proton Therapy(IMPT) plans. Dose-Volume-Histograms (DVH) of target and Organ-at-Risks (OARs) were analyzed along with all worst case scenarios. Total delivery time was calculated based on the assumption of a 360 degree gantry room with 1 RPM rotation speed, 2ms spot switching time, beam current 1nA, minimum spot weighting 0.01 MU, energy-layer-switching-time (ELST) from 0.5 to 4s. Results: Compared to IMPT, SPArc delivered less integral dose(−14% lung and −8% oropharynx). For lung case, SPArc reduced 60% of skin max dose, 35% of rib max dose and 15% of lung mean dose. Conformity Index is improved from 7.6(IMPT) to 4.0(SPArc). Compared to Arcmulti-field, SPArc reduced number of energy layers by 61%(276 layers in lung) and 80%(1008 layers in oropharynx) while kept the same robust plan quality. With ELST from 0.5s to 4s, it reduced 55%–60% of Arcmulti-field delivery time for the lung case and 56%–67% for the oropharynx case. Conclusion: SPArc is the first robust and delivery-efficient proton spot-scanning arc therapy technique which could be implemented in routine clinic. For modern proton machine with ELST close to 0.5s, SPArc would be a popular treatment option for both single and multi-room center.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2014

OCCAMS: Optically Controlled and Corrected Active Meta-Material Space Structures

Telescopes require sub-wavelength figure (shape) error in order to achieve acceptable Strehl ratios. Traditional methods of achieving this require rigid and therefore heavy mirrors and reaction structures as well as proportionally heavy and expensive spacecraft busses and launch vehicles. This effectively limits the diameter and therefore resolution and collecting area of space optics. Large diameter telescopes must either be heavy or actively controlled. Space telescopes of the size proposed for missions such as TPF (Terrestrial Planet Finder), TPI (Terrestrial Planet Imager), etc. will likely require large active primaries and structures and corrective optics to implement downstream wavefront control. We propose a novel viable enabling technology. High resolution space imaging requires the production of lightweight large aperture optics subject to design tradespace constraints based on nanometer physical tolerances, low system aerial density, high control authority, suitable thermal and mechanical properties, deployment capability, launch vehicle volume constraints, as well as production cost and schedule risk mitigation. Segmented systems impose additional requirements on segment alignment, wavefront phasing, and telescope mass with increased edge diffraction. Photons weigh nothing. Why must even small space telescopes "weigh" tons? Our team is working to demonstrate that they do not, by leveraging 15 years of effort and a novel advanced concept.The ultimate research goal is to refine technology to produce a mission capable ultra-lightweight membrane optic whose shape can be remotely controlled using a laser beam. Using our novel optically-controlled molecular actuators allows substitution of optically-induced control for rigidity and mirror mass. In analogy with noise-canceling headphones, this technique also potentially provides a way to excite vibratory modes to couple with and damp out normal modes of oscillation induced by slewing, other motion and thermal changes, thus allowing a robust response to repointing of a large aperture.

Astronomy↗
DOE OSTI2016

WE-AB-202-10: Modelling Individual Tumor-Specific Control Probability for Hypoxia in Rectal Cancer

Purpose: To investigate hypoxia-guided dose-boosting for increased tumour control and improved normal tissue sparing using FMISO-PET images Methods: Individual tumor-specific control probability (iTSCP) was calculated using a modified linear-quadratic model with rectal-specific radiosensitivity parameters for three limiting-case assumptions of the hypoxia / FMISO uptake relationship. {sup 18}FMISO-PET images from 2 patients (T3N0M0) from the RHYTHM trial (Investigating Hypoxia in Rectal Tumours NCT02157246) were chosen to delineate a hypoxic region (GTV-MISO defined as tumor-to-muscle ratio > 1.3) within the anatomical GTV. Three VMAT treatment plans were created in Eclipse (Varian): STANDARD (45Gy / 25 fractions to PTV4500); BOOST-GTV (simultaneous integrated boost of 60Gy / 25fr to GTV +0.5cm) and BOOST-MISO (60Gy / 25fr to GTV-MISO+0.5cm). GTV mean dose (in EQD2), iTSCP and normal tissue dose-volume metrics (small bowel, bladder, anus, and femoral heads) were recorded. Results: Patient A showed small hypoxic volume (15.8% of GTV) and Patient B moderate hypoxic volume (40.2% of GTV). Dose escalation to 60Gy was achievable, and doses to femoral heads and small bowel in BOOST plans were comparable to STANDARD plans. For patient A, a reduced maximum bladder dose was observed in BOOST-MISO compared to BOOST-GTV (D0.1cc 49.2Gy vs 54.0Gy). For patient B, a smaller high dose volume was observed for the anus region in BOOST-MISO compared to BOOST-GTV (V55Gy 19.9% vs 100%), which could potentially reduce symptoms of fecal incontinence. For BOOST-MISO, the largest iTSCPs (A: 95.5% / B: 90.0%) assumed local correlation between FMISO uptake and hypoxia, and approached iTSCP values seen for BOOST-GTV (A: 96.1% / B: 90.5%). Conclusion: Hypoxia-guided dose-boosting is predicted to improve local control in rectal tumors when FMISO is spatially correlated to hypoxia, and to reduce dose to organs-at-risk compared to boosting the whole GTV. This could lead to organ-preserving treatment strategies for locally-advanced rectal cancer, thereby improving quality of life. Oxford Cancer Imaging Centre (OCIC); Cancer Research UK (CRUK); Medical Research Council (MRC)

60 APPLIED LIFE SCIENCES↗
NASA NTRS1993

High surface area, low weight composite nickel fiber electrodes

The energy density and power density of light weight aerospace batteries utilizing the nickel oxide electrode are often limited by the microstructures of both the collector and the resulting active deposit in/on the collector. Heretofore, these two microstructures were intimately linked to one another by the materials used to prepare the collector grid as well as the methods and conditions used to deposit the active material. Significant weight and performance advantages were demonstrated by Britton and Reid at NASA-LeRC using FIBREX nickel mats of ca. 28-32 microns diameter. Work in our laboratory investigated the potential performance advantages offered by nickel fiber composite electrodes containing a mixture of fibers as small as 2 microns diameter (Available from Memtec America Corporation). These electrode collectors possess in excess of an order of magnitude more surface area per gram of collector than FIBREX nickel. The increase in surface area of the collector roughly translates into an order of magnitude thinner layer of active material. Performance data and advantages of these thin layer structures are presented. Attributes and limitations of their electrode microstructure to independently control void volume, pore structure of the Ni(OH)2 deposition, and resulting electrical properties are discussed.

Johnson, Bradley A.↗
NASA NTRS2011

Dexterous Operations on ISS and Future Applications

The Mobile Servicing System (MSS) is a complex robotics system used extensively in the assembly, inspection and maintenance of the International Space Station (ISS). Its external components are comprised of the Space Station Remote Manipulator System (SSRMS), the Mobile Base System (MBS), and the Special Purpose Dexterous Manipulator (SPDM or "Dextre"). Dexterous robotic maintenance operations on the ISS are now enabled with the launch and deployment of "Dextre" in March 2008 and the recently completed commissioning to support nominal operations. These operations include allowing for maintenance of the MSS capability to be executed uniquely via robotic means. Examples are detailed inspection and the removal and replacement of On-orbit Replaceable Units (ORUs) located outside the pressurized volume of the ISS, alleviating astronauts from performing numerous risky and time-consuming extra-vehicular activities (EVAs). In light of the proposed extension of the ISS to 2020 and beyond, "Dextre" can also be seen as a resource for the support and conduct of external ISS experiments. "Dextre" can be utilized to move experiments around ISS, as test bed for more elaborate experiments outside the original design intent, and as a unique platform for external experiments. This paper summarizes the status of "Dextre", its planned use, and future potential for dexterous operations on the ISS. Lessons learned from the planning and execution of SPDM commissioning are first introduced, and significant differences between "Dextre" and SSRMS operations are discussed. The use of ground control as the predominant method for operating "Dextre" is highlighted, along with the benefits and challenges that this poses. Finally, the latest plans for dexterous operations on ISS are summarized including visiting vehicle unloading, nominal maintenance, and operations of a more experimental flavor.

Keenan, P. Andrew↗
NASA NTRS2013

Propellant-Flow-Actuated Rocket Engine Igniter

A rocket engine igniter has been created that uses a pneumatically driven hammer that, by specialized geometry, is induced into an oscillatory state that can be used to either repeatedly impact a piezoelectric crystal with sufficient force to generate a spark capable of initiating combustion, or can be used with any other system capable of generating a spark from direct oscillatory motion. This innovation uses the energy of flowing gaseous propellant, which by means of pressure differentials and kinetic motion, causes a hammer object to oscillate. The concept works by mass flows being induced through orifices on both sides of a cylindrical tube with one or more vent paths. As the mass flow enters the chamber, the pressure differential is caused because the hammer object is supplied with flow on one side and the other side is opened with access to the vent path. The object then crosses the vent opening and begins to slow because the pressure differential across the ball reverses due to the geometry in the tube. Eventually, the object stops because of the increasing pressure differential on the object until all of the kinetic energy has been transferred to the gas via compression. This is the point where the object reverses direction because of the pressure differential. This behavior excites a piezoelectric crystal via direct impact from the hammer object. The hammer strikes a piezoelectric crystal, then reverses direction, and the resultant high voltage created from the crystal is transferred via an electrode to a spark gap in the ignition zone, thereby providing a spark to ignite the engine. Magnets, or other retention methods, might be employed to favorably position the hammer object prior to start, but are not necessary to maintain the oscillatory behavior. Various manifestations of the igniter have been developed and tested to improve device efficiency, and some improved designs are capable of operation at gas flow rates of a fraction of a gram per second (0.001 lb/s) and pressure drops on the order of 30 to 50 kilopascal (a few psi). An analytical model has been created and tested in conjunction with a precisely calibrated reference model. The analytical model accurately captures the overall behavior of this innovation. The model is a simple "volume-orifice" concept, with each chamber considered a single temperature and pressure "node" connected to adjacent nodes, or to vent paths through flow control orifices. Mass and energy balances are applied to each node, with gas flow predicted using simple compressible flow equations.

Wollen, Mark↗
NASA NTRSDate not supplied

Hierarchical Mixture of Experts for Advanced Air Mobility Flight Phase Classification

Advanced Air Mobility (AAM) and Urban Air Mobility (UAM) operations will have numerous vehicles and aircraft flying in the airspace, which poses safety and security concerns. Commercial airlines utilize Air Traffic Management (ATM) and Air Traffic Control (ATC) for real-time monitoring, surveillance, traffic coordination, and rerouting to maintain safe and efficient flight patterns. Transferring ATM and ATC architectures to AAM/UAM will be challenging to implement since AAM/UAM aircraft fly at lower altitudes, have more static and dynamic obstacles, operate in highly dense environments, and have several more aircraft to monitor for a given volume of the national airspace (NAS). Aircraft typically have the following flight phases: takeoff, climb, cruise, descent, and landing. Classifying these flight phases provides insight into ensuring safe operations, providing situational awareness of the NAS, and monitoring flights in emergencies. Automatic flight phase classification will enhance the efficiencies of ATM/ATC-like architectures for AAM/UAM, especially since numerous aircraft will be flying in highly dense urban environments. Typical flight phase classification methods are all-or-nothing, which will not capture or accurately classify the transitions between flight phases. Utilizing hierarchical mixture of experts (HME) provides a flight phase classification solution that includes transitions between the flight phases by assigning weights based on ground-based distributed sensor readings from cameras and radar. Adding the transitions between flight phases increases the fidelity of flight phase classification and provides deeper insight into flight phase classification by leveraging distributed sensing concepts. Simulation results and post-processed flight test results demonstrate the utility of HME for automatic and robust flight phase classification for real-time AAM operations.

distributed sensing↗
DOE OSTI2015

Uniaxial Creep as a Control on Mercury Intrusion Capillary Pressure in Consolidating Rock Salt

The nature of geologic disposal of nuclear waste in salt formations requires validated and verified two-phase flow models of transport of brine and gas through intact, damaged, and consolidating crushed salt. Such models exist in other realms of subsurface engineering for other lithologic classes (oil and gas, carbon sequestration etc. for clastics and carbonates) but have never been experimentally validated and parameterized for salt repository scenarios or performance assessment. Models for waste release scenarios in salt back-fill require phenomenological expressions for capillary pressure and relative permeability that are expected to change with degree of consolidation, and require experimental measurement to parameterize and validate. This report describes a preliminary assessment of the influence of consolidation (i.e. volume strain or porosity) on capillary entry pressure in two phase systems using mercury injection capillary pressure (MICP). This is to both determine the potential usefulness of the mercury intrusion porosimetry method, but also to enable a better experimental design for these tests. Salt consolidation experiments are performed using novel titanium oedometers, or uniaxial compression cells often used in soil mechanics, using sieved run-of-mine salt from the Waste Isolation Pilot Plant (WIPP) as starting material. Twelve tests are performed with various starting amounts of brine pore saturation, with axial stresses up to 6.2 MPa (~900 psi) and temperatures to 90°C. This corresponds to UFD Work Package 15SN08180211 milestone “FY:15 Transport Properties of Run-of-Mine Salt Backfill – Unconsolidated to Consolidated”. Samples exposed to uniaxial compression undergo time-dependent consolidation, or creep, to various degrees. Creep volume strain-time relations obey simple log-time behavior through the range of porosities (~50 to 2% as measured); creep strain rate increases with temperature and applied stress as expected. Mercury porosimetry is used to determine characteristic capillary pressure curves from a series of consolidation tests and show characteristic saturation-capillary pressure curves that follow the common van Genuchten (1978, 1980) formulation at low stresses. Higher capillary pressure data are suspect due to the large potential for sample damage, including fluid inclusion decrepitation and pore collapse. Data are supportive of use of the Leverett “J” function (Leverett, 1941) to use for scaling characteristic curves at different degrees of consolidation, but better permeability determinations are needed to support this hypothesis. Recommendations for further and refined testing are made with the goal of developing a self- consistent set of constitutive laws for granular salt consolidation and multiphase (brine-air) flow.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗