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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

SU-E-J-228: MRI-Based Planning: Dosimetric Feasibility of Dose Painting for ADCDefined Intra-Prostatic Tumor

Purpose: Apparent diffusion coefficient (ADC) map may help to delineate the gross tumor volume (GTV) in prostate gland. Dose painting with external beam radiotherapy for GTV might increase the local tumor control. The purpose of this study is to explore the maximum boosting dose on GTV using VMAT without sacrificing sparing of organs at risk (OARs) in MRI based planning. Methods: VMAT plans for 5 prostate patients were generated following the commonly used dose volume (DV) criteria based on structures contoured on T2 weighted MRI with bulk electron density assignment using electron densities derived from ICRU46. GTV for each patient was manually delineated based on ADC maps and fused to T2-weighted image set for planning study. A research planning system with Monte Carlo dose engine (Monaco, Elekta) was used to generate the VMAT plans with boosting dose on GTV gradually increased from 85Gy to 100Gy. DV parameters, including V(boosting-dose) (volume covered by boosting dose) for GTV, V75.6Gy for PTV, V45Gy, V70Gy, V72Gy and D1cc (Maximum dose to 1cc volume) for rectum and bladder, were used to measure plan quality. Results: All cases achieve at least 99.0% coverage of V(boosting-dose) on GTV and 95% coverage of V75.6Gy to the PTV. All the DV criteria, V45Gy≤50% and V70Gy≤15% for bladder and rectum, D1cc ≤77Gy (Rectum) and ≤80Gy (Bladder), V72Gy≤5% (rectum and bladder) were maintained when boosting GTV to 95Gy for all cases studied. Except for two patients, all the criteria were also met when the boosting dose goes to 100Gy. Conclusion: It is dosimetrically feasible safe to boost the dose to at least 95Gy to ADC defined GTV in prostate cancer using MRI guided VMAT delivery. Conclusion: It is dosimetrically feasible safe to boost the dose to at least 95Gy to ADC defined GTV in prostate cancer using MRI guided VMAT delivery. This research is partially supported by Elekta Inc.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Development of a Supercharged Octane Number and a Supercharged Octane Index

Gasoline knock resistance is characterized by the Research and Motor Octane Number (RON and MON), which are rated on the CFR octane rating engine at naturally aspirated conditions. However, modern automotive downsized boosted spark ignition (SI) engines generally operate at higher cylinder pressures and lower temperatures relative to the RON and MON tests. Using the naturally aspirated RON and MON ratings, the octane index (OI) characterizes the knock resistance of gasolines under boosted operation by linearly extrapolating into boosted “beyond RON” conditions via RON, MON, and a linear regression K factor. Using OI solely based on naturally aspirated RON and MON tests to extrapolate into boosted conditions can lead to significant errors in predicting boosted knock resistance between gasolines due to non-linear changes in autoignition and knocking characteristics with increasing pressure conditions. Here, a new “Supercharged Octane Number” (SON) method was developed on the CFR engine at increased intake pressures, which improved the correlation to boosted knock-limited automotive SI engine data over RON for several surrogate fuels and gasolines, including five “Co-Optima” RON 98 fuels and an E10 regular grade gasoline. Furthermore, the conventional OI was extended to a newly introduced Supercharged Octane Index (OI S ) based on SON and RON, which significantly improved the correlation to fuel knock resistance measurements from modern boosted SI engine knock-limited spark advance tests. This demonstrated the first proof of concept of a SON and OI S to better characterize a fuel’s knock resistance in modern boosted SI engines.

42 ENGINEERING↗
NASA NTRS2006

TRMM On-Orbit Performance Reassessed After Control Change

The Tropical Rainfall Measuring Mission (TRMM) spacecraft, a joint mission between the U.S. and Japan, launched onboard an H-I1 rocket on November 27, 1997, and transitioned in August, 2001, from an average operating altitude of 350 kilometers to 402.5 kilometers. Due to problems using the Earth Sensor Assembly (ESA) at the higher altitude, TRMM switched to a backup attitude control mode. Prior to the orbit boost TRMM controlled pitch and roll to the local vertical using ESA measurements while using gyro data to propagate yaw attitude between yaw updates from the Sun sensors. After the orbit boost, a Kalman filter used 3-axis gyro data with Sun sensor and magnetometers to estimate onboard attitude. While originally intended to meet a degraded attitude accuracy of 0.7 degrees, the new control mode met the original 0.2 degree attitude accuracy requirement after improving onboard ephemeris prediction and adjusting the magnetometer calibration onboard. Independent roll attitude checks using a science instrument, the Precipitation Radar (PR) which was built in Japan, provided a novel insight into the pointing performance. The PR data helped identify the pointing errors after the orbit boost, track the performance improvements, and show subtle effects from ephemeris errors and gyro bias errors. It also helped identify average bias trends throughout the mission. Roll errors tracked by the PR from sample orbits pre-boost and post-boost are shown in Figure 1. Prior to the orbit boost, the largest attitude errors were due to occasional interference in the ESA. These errors were sometime larger than 0.2 degrees in pitch and roll, but usually less, as estimated from a comprehensive review of the attitude excursions using gyro data. Sudden jumps in the onboard roll show up as spikes in the reported attitude since the control responds within tens of seconds to null the pointing error. The PR estimated roll tracks well with an estimate of the roll history propagated using gyro data. After the orbit boost, the attitude errors shown by the PR roll have a smooth sine-wave type signal because of the way that attitude errors propagate with the use of gyro data. Yaw errors couple at orbit period to roll with 1/4 orbit lag. By tracking the amplitude, phase, and bias of the sinusoidal PR roll error signal, it was shown that the average pitch rotation axis tends to be offset from orbit normal in a direction perpendicular to the Sun direction, as shown in Figure 2 for a 200 day period following the orbit boost. This is a result of the higher accuracy and stability of the Sun sensor measurements relative to the magnetometer measurements used in the Kalman filter. In November, 2001 a magnetometer calibration adjustment was uploaded which improved the pointing performance, keeping the roll and yaw amplitudes within about 0.1 degrees.

Bilanow, Stephen↗
NASA NTRS2009

Climate and Lightning: An updated TRMM-LIS Analysis

The TRMM Lightning Imaging Sensor (LIS) has sampled global tropical and sub-tropical lightning flash densities for approximately 11 years. These data were originally processed and results presented by the authors in the 3rd AMS MALD Conference held in 2007 using both pre and post TRMM-boost lightning data. These data were normalized for the orbit boost by scaling the pre-boost data by a fixed constant based on the different swath areas for the pre and post-boost years (post-boost after 2001). Inevitably, one must question this simple approach to accounting for the orbit boost when sampling such a noisy quantity. Hence we are in the process of reprocessing the entire 11-year TRMM LIS dataset to reduce the orbit swath of the post-boost era to that of the pre-boost in order to eliminate sampling bias in the dataset. Study of the diurnal/seasonal/annual sampling suggests that those biases are already minimal and should not contribute to error in examination of annual trends. We will present new analysis of the 11-year annual trends in total lightning flash density for all latitudinal belts and select regions/regimes of the tropics as related to conventional climate signals and precipitation contents in the same period. The results should enable us to address, in some fashion, the sensitivity of the lightning flash density to subtle changes in climate.

Petersen, Walter A.↗
DOE OSTI2015

A planning comparison of 7 irradiation options allowed in RTOG 1005 for early-stage breast cancer

This study compared the 7 treatment plan options in achieving the dose-volume criteria required by the Radiation Therapy Oncology Group (RTOG) 1005 protocol. Dosimetry plans were generated for 15 representative patients with early-stage breast cancer (ESBC) based on the protocol-required dose-volume criteria for each of the following 7 treatment options: 3D conformal radiotherapy (3DCRT), whole-breast irradiation (WBI) plus 3DCRT lumpectomy boost, 3DCRT WBI plus electron boost, 3DCRT WBI plus intensity-modulated radiation therapy (IMRT) boost, IMRT WBI plus 3DCRT boost, IMRT WBI plus electron boost, IMRT WBI plus IMRT boost, and simultaneous integrated boost (SIB) with IMRT. A variety of dose-volume parameters, including target dose conformity and uniformity and normal tissue sparing, were compared for these plans. For the patients studied, all plans met the required acceptable dose-volume criteria, with most of them meeting the ideal criteria. When averaged over patients, most dose-volume goals for all plan options can be achieved with a positive gap of at least a few tenths of standard deviations. The plans for all 7 options are generally comparable. The dose-volume goals required by the protocol can in general be easily achieved. IMRT WBI provides better whole-breast dose uniformity than 3DCRT WBI does, but it causes no significant difference for the dose conformity. All plan options are comparable for lumpectomy dose uniformity and conformity. Patient anatomy is always an important factor when whole-breast dose uniformity and conformity and lumpectomy dose conformity are considered.

61 RADIATION PROTECTION AND DOSIMETRY↗
NASA NTRS1990

Analysis and design of a high power, digitally-controlled spacecraft power system

The progress to date on the analysis and design of a high power, digitally controlled spacecraft power system is described. Several battery discharger topologies were compared for use in the space platform application. Updated information has been provided on the battery voltage specification. Initially it was thought to be in the 30 to 40 V range. It is now specified to be 53 V to 84 V. This eliminated the tapped-boost and the current-fed auto-transformer converters from consideration. After consultations with NASA, it was decided to trade-off the following topologies: (1) boost converter; (2) multi-module, multi-phase boost converter; and (3) voltage-fed push-pull with auto-transformer. A non-linear design optimization software tool was employed to facilitate an objective comparison. Non-linear design optimization insures that the best design of each topology is compared. The results indicate that a four-module, boost converter with each module operating 90 degrees out of phase is the optimum converter for the space platform. Large-signal and small-signal models were generated for the shunt, charger, discharger, battery, and the mode controller. The models were first tested individually according to the space platform power system specifications supplied by NASA. The effect of battery voltage imbalance on parallel dischargers was investigated with respect to dc and small-signal responses. Similarly, the effects of paralleling dischargers and chargers were also investigated. A solar array and shunt model was included in these simulations. A model for the bus mode controller (power control unit) was also developed to interface the Orbital replacement Unit (ORU) model to the platform power system. Small signal models were used to generate the bus impedance plots in the various operating modes. The large signal models were integrated into a system model, and time domain simulations were performed to verify bus regulation during mode transitions. Some changes have subsequently been incorporated into the models. The changes include the use of a four module boost discharger, and a new model for the mode controller, which includes the effects of saturation. The new simulations for the boost discharger show the improvement in bus ripple that can be achieved by phase-shifted operation of each of the boost modules.

Lee, F. C.↗
DOE OSTI2014

Volumetric-modulated arc radiotherapy for pancreatic malignancies: Dosimetric comparison with sliding-window intensity-modulated radiotherapy and 3-dimensional conformal radiotherapy

Volumetric-modulated arc radiotherapy (VMAT) is an iteration of intensity-modulated radiotherapy (IMRT), both of which deliver highly conformal dose distributions. Studies have shown the superiority of VMAT and IMRT in comparison with 3-dimensional conformal radiotherapy (3D-CRT) in planning target volume (PTV) coverage and organs-at-risk (OARs) sparing. This is the first study examining the benefits of VMAT in pancreatic cancer for doses more than 55.8 Gy. A planning study comparing 3D-CRT, IMRT, and VMAT was performed in 20 patients with pancreatic cancer. Treatments were planned for a 25-fraction delivery of 45 Gy to a large field followed by a reduced-volume 8-fraction external beam boost to 59.4 Gy in total. OARs and PTV doses, conformality index (CI) deviations from 1.0, monitor units (MUs) delivered, and isodose volumes were compared. IMRT and VMAT CI deviations from 1.0 for the large-field and the boost plans were equivalent (large field: 0.032 and 0.046, respectively; boost: 0.042 and 0.037, respectively; p > 0.05 for all comparisons). Both IMRT and VMAT CI deviations from 1.0 were statistically superior to 3D-CRT (large field: 0.217, boost: 0.177; p < 0.05 for all comparisons). VMAT showed reduction of the mean dose to the boost PTV (VMAT: 61.4 Gy, IMRT: 62.4 Gy, and 3D-CRT: 62.3 Gy; p < 0.05). The mean number of MUs per fraction was significantly lower for VMAT for both the large-field and the boost plans. VMAT delivery time was less than 3 minutes compared with 8 minutes for IMRT. Although no statistically significant dose reduction to the OARs was identified when comparing VMAT with IMRT, VMAT showed a reduction in the volumes of the 100% isodose line for the large-field plans. Dose escalation to 59.4 Gy in pancreatic cancer is dosimetrically feasible with shorter treatment times, fewer MUs delivered, and comparable CIs for VMAT when compared with IMRT.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2015

SU-E-J-124: 18F-FDG PET Imaging to Improve RT Treatment Outcome for Locally Advanced Lung Cancer

Purpose: To investigate spatial correlation between high uptake regions of pre- and 10-days-post therapy{sup 1} {sup 8}F-FDG PET in recurrent lung cancer and to evaluate the feasibility of dose escalation boosting only regions with high FDG uptake identified on baseline PET. Methods: Nineteen patients with stages II– IV inoperable lung cancer were selected. Volumes of interest (VOI) on pre-therapy FDG-PET were defined using an isocontour at ≥50% of SUVmax. VOI of pre- and post-therapy PET images were correlated for the extent of overlap. A highly optimized IMRT plan to 60 Gy prescribed to PTV defined on the planning CT was designed using clinical dose constraints for the organs at risk. A boost of 18 Gy was prescribed to the VOI defined on baseline PET. A composite plan of the total 78 Gy was compared with the base 60 Gy plan. Increases in dose to the lungs, spinal cord and heart were evaluated. IMRT boost plan was compared with proton RT and SBRT boost plans. Results: Overlap fraction of baseline PET VOI with the VOI on 10 days-post therapy PET was 0.8 (95% CI: 0.7 – 0.9). Using baseline VOI as a boosting volume, dose could be escalated to 78 Gy for 15 patients without compromising the dose constraints. For 4 patients, the dose limiting factors were V20Gy and Dmean for the total lung, and Dmax for the spinal cord. An increase of the dose to OARs correlated significantly with the relative size of the boost volume. Conclusion: VOI defined on baseline 18F-FDG PET by the SUVmax-≥50% isocontour may be a biological target volume for escalated radiation dose. Dose escalation to this volume may provide improved tumor control without breaching predefined dose constraints for OARs. The best treatment outcome may be achieved with proton RT for large targets and with SBRT for small targets.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Power converter circuitry for photovoltaic devices

Power converter circuitry includes a direct current (DC) input comprising a first DC input node and a second DC input node, an alternating current (AC) output comprising a first AC output node coupled to the first DC input node and a second AC output node, a first boost switch coupled between the second DC input node and a boost intermediate node, a second boost switch coupled between the boost intermediate node and a common node, a boost inductor coupled between the boost intermediate node and the first DC input node, a link capacitor coupled between the second DC input node and the common node, a first half-bridge switch coupled between the second DC input node and a half-bridge intermediate node, a second half-bridge switch coupled between the half-bridge intermediate node and the common node, and a half-bridge inductor coupled between the half-bridge intermediate node and the second AC output node.

Ayyanar, Rajapandian↗
DOE OSTI2020

Comprehensive Efficiency Analysis of Current Source Inverter Based SPM Machine Drive System for Traction Applications

A current-source inverter (CSI) has the natural capability of boosting the output voltage which is a notable advantage over voltage source inverter (VSI) in traction drive applications. This paper investigates the voltage boosting feature of the CSI to improve the overall efficiency of the CSI-based surface permanent magnet (SPM) machine drive system in the constant power region. The effects of the boost function on the total system losses, including the machine copper loss, core loss, and magnet loss, as well as the device conduction and switching loss in the CSI and dc/dc converter, are described using analytical models. The operating characteristics of the machine and CSI are validated by 2-D finite-element analysis (FEA) and simulations. Based on the loss model, the effects of the modulation index on the overall drive system losses and power factor have been analyzed. A genetic algorithm has been used to optimize the CSI's boost ratio, demonstrating that the drive system efficiency can be increased by 1% to 2.5% along the constant-power regime envelope by using the boost function.

current source inverter, genetic algorithm, SPM ma↗
DOE OSTI2017

Electrified Automotive Powertrain Architecture Using Composite DC–DC Converters

In a hybrid or electric vehicle powertrain, a boost dc-dc converter enables reduction of the size of the electric machine and optimization of the battery system. Design of the powertrain boost converter is challenging because the converter must be rated at high peak power, while efficiency at medium-to-light load is critical for the vehicle system performance. By addressing only some of the loss mechanisms, previously proposed efficiency improvement approaches offer limited improvements in size, cost, and efficiency tradeoffs. This article shows how all dominant loss mechanisms in automotive powertrain applications can be mitigated using a new boost composite converter approach. In the composite dc-dc architecture, the loss mechanisms associated with indirect power conversion are addressed explicitly, resulting in fundamental efficiency improvements over wide ranges of operating conditions. Several composite converter topologies are presented and compared to state-of-the-art boost converter technologies. It is found that the selected boost composite converter results in a decrease in the total loss by a factor of 2-4 for typical drive cycles. Furthermore, the total system capacitor power rating and energy rating are substantially reduced, which implies potentials for significant reductions in system size and cost.

25 ENERGY STORAGE↗
DOE OSTI2014

National Cancer Data Base Analysis of Radiation Therapy Consolidation Modality for Cervical Cancer: The Impact of New Technological Advancements

Purpose: To utilize the National Cancer Data Base to evaluate trends in brachytherapy and alternative radiation therapy utilization in the treatment of cervical cancer, to identify associations with outcomes between the various radiation therapy modalities. Methods and Materials: Patients with International Federation of Gynecology and Obstetrics stage IIB-IVA cervical cancer in the National Cancer Data Base who received treatment from January 2004 to December 2011 were analyzed. Overall survival was estimated by the Kaplan-Meier method. Univariate and multivariable analyses were performed to identify factors associated with type of boost radiation modality used and its impact on survival. Results: A total of 7654 patients had information regarding boost modality. A predominant proportion of patients were Caucasian (76.2%), had stage IIIB (48.9%) disease with squamous (82.0%) histology, were treated at academic/research centers (47.7%) in the South (34.8%), and lived 0 to 5 miles (27.9%) from the treating facility. A majority received brachytherapy (90.3%). From 2004 to 2011, brachytherapy use decreased from 96.7% to 86.1%, whereas intensity modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT) use increased from 3.3% to 13.9% in the same period (P<.01). Factors associated with decreased brachytherapy utilization included older age, stage IVA disease, smaller tumor size, later year of diagnosis, lower-volume treatment centers, and facility type. After controlling for significant factors from survival analyses, IMRT or SBRT boost resulted in inferior overall survival (hazard ratio, 1.86; 95% confidence interval, 1.35-2.55; P<.01) as compared with brachytherapy. In fact, the survival detriment associated with IMRT or SBRT boost was stronger than that associated with excluding chemotherapy (hazard ratio, 1.61′ 95% confidence interval, 1.27-2.04′ P<.01). Conclusions: Consolidation brachytherapy is a critical treatment component for locally advanced cervical cancer; however, there has been declining utilization of brachytherapy. Increased use of IMRT and SBRT boost coupled with increased mortality risk should raise concerns about utilizing these approaches over brachytherapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Effect of Thomas Rotation on the Lorentz Transformation of Electromagnetic fields

A relativistic particle undergoing successive boosts which are non collinear will experience a rotation of its coordinate axes with respect to the boosted frame. This rotation of coordinate axes is caused by a relativistic phenomenon called Thomas Rotation. We assess the importance of Thomas rotation in the calculation of physical quantities like electromagnetic fields in the relativistic regime. We calculate the electromagnetic field tensor for general three dimensional successive boosts in the particle’s rest frame as well as the laboratory frame. We then compare the electromagnetic field tensors obtained by a direct boost β δβ → + → and successive boosts β → and Δβ → and check their consistency with Thomas rotation. This framework might be important to situations such as the calculation of frequency shifts for relativistic spin1/2 particles undergoing Larmor precession in electromagnetic fields with small field non-uniformities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Longitudinal hydrodynamics from event-by-event Landau initial conditions

Here we investigate three-dimensional ideal hydrodynamic evolution, with Landau initial conditions, incorporating event-by-event variation with many events and transverse density inhomogeneities. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of θ (20%-30%) expected at freeze-out for most scenarios. Moreover, the deviation from boost invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, hydrodynamics where boost invariance holds at midrapidity is inadequate to extract transport coefficients of the quark-gluon plasma. We conclude by arguing that developing experimental probes of boost invariance is necessary, and suggest some promising directions in this regard.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: Part 2, photon noise theory

High-resolution broadband spectroscopy at near-infrared (NIR) wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar, with the TEDI interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec NIR echelle spectrograph. These are the first multidelay EDI demonstrations on starlight. We demonstrated very high (10×) resolution boost and dramatic (20× or more) robustness to point spread function wavelength drifts in the native spectrograph. Data analysis, results, and instrument noise are described in a companion paper (part 1). This part 2 describes theoretical photon limited and readout noise limited behaviors, using simulated spectra and instrument model with noise added at the detector. We show that a single interferometer delay can be used to reduce the high frequency noise at the original resolution (1× boost case), and that except for delays much smaller than the native response peak half width, the fringing and nonfringing noises act uncorrelated and add in quadrature. This is due to the frequency shifting of the noise due to the heterodyning effect. We find a sum rule for the noise variance for multiple delays. The multiple delay EDI using a Gaussian distribution of exposure times has noise-to-signal ratio for photon-limited noise similar to a classical spectrograph with reduced slitwidth and reduced flux, proportional to the square root of resolution boost achieved, but without the focal spot limitation and pixel spacing Nyquist limitations. At low boost (~1×) EDI has ~1.4× smaller noise than conventional, and at >10× boost, EDI has ~1.4× larger noise than conventional. Readout noise is minimized by the use of three or four steps instead of 10 of TEDI. Net noise grows as step phases change from symmetrical arrangement with wavenumber across the band. As a result, for three (or four) steps, we calculate a multiplicative bandwidth of 1.8:1 (2.3:1), sufficient to handle the visible band (400 to 700 nm, 1.8:1) and most of TripleSpec (2.6:1).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Potential benefits of dosimetric VMAT tracking verified with 3D film measurements

Purpose: To evaluate three different plan adaptation strategies using 3D film-stack dose measurements of both focal boost and hypofractionated prostate VMAT treatments. The adaptation strategies (a couch shift, geometric tracking, and dosimetric tracking) were applied for three realistic intrafraction prostate motions. Methods: A focal boost (35 × 2.2 and 35 × 2.7 Gy) and a hypofractionated (5 × 7.25 Gy) prostate VMAT plan were created for a heterogeneous phantom that allows for internal prostate motion. For these plans geometric tracking and dosimetric tracking were evaluated by ionization chamber (IC) point dose measurements (zero-D) and measurements using a stack of EBT3 films (3D). The geometric tracking applied translations, rotations, and scaling of the MLC aperture in response to realistic prostate motions. The dosimetric tracking additionally corrected the monitor units to resolve variations due to difference in depth, tissue heterogeneity, and MLC-aperture. The tracking was based on the positions of four fiducial points only. The film measurements were compared to the gold standard (i.e., IC measurements) and the planned dose distribution. Additionally, the 3D measurements were converted to dose volume histograms, tumor control probability, and normal tissue complication probability parameters (DVH/TCP/NTCP) as a direct estimate of clinical relevance of the proposed tracking. Results: Compared to the planned dose distribution, measurements without prostate motion and tracking showed already a reduced homogeneity of the dose distribution. Adding prostate motion further blurs the DVHs for all treatment approaches. The clinical practice (no tracking) delivered the dose distribution inside the PTV but off target (CTV), resulting in boost dose errors up to 10%. The geometric and dosimetric tracking corrected the dose distribution’s position. Moreover, the dosimetric tracking could achieve the planned boost DVH, but not the DVH of the more homogeneously irradiated prostate. A drawback of both the geometric and dosimetric tracking was a reduced MLC blocking caused by the rotational component of the MLC aperture corrections. Because of the used CTV to PTV margins and the high doses in the considered fractionation schemes, the TCP differed less than 0.02 from the planned value for all targets and all correction methods. The rectal NTCP constraints, however, could not be realized using any of these methods. Conclusions: The geometric and dosimetric tracking use only a limited input, but they deposit the dose distribution with higher geometric accuracy than the clinical practice. The latter case has boost dose errors up to 10%. The increased accuracy has a modest impact [Δ(NT)CP < 0.02] because of the applied margins and the high dose levels used. To allow further margin reduction tracking methods are vital. The proposed methodology could further be improved by implementing a rotational correction using collimator rotations.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1976

Investigation of TC-1 flight failure using power spectral analysis

During the Titan Centaur 1 test flight a failure involving at least one of the Centaur propellant boost pumps occurred. Also, neither of the boost pump speed instruments indicated pump rotation. Accelerometer data from the Titan Centaur 1 flight failure were analyzed using power spectral density methods to determine boost pump speed during attempted starts of the Centaur. The technique was demonstrated on a reference flight. The hydrogen boost pump speed transient was determined for the TC-1 flight. Other trends are seen in the data. However, these are not believed to be the oxygen boost pump. Discussion of data enhancement techniques is also presented.

Lorenzo, C. F.↗
NASA NTRS1988

Booster propulsion/vehicle impact study, 2

This is the final report in a study examining the impact of launch vehicles for various boost propulsion design options. These options included: differing boost phase engines using different combinations of fuels and coolants to include RP-1, methane, propane (subcooled and normal boiling point), and hydrogen; variable and high mixture ratio hydrogen engines; translating nozzles on boost phase engines; and cross feeding propellants from the booster to second stage. Vehicles examined included a fully reusable two stage cargo vehicle and a single stage to orbit vehicle. The use of subcooled propane as a fuel generated vehicles with the lowest total vehicle dry mass. Engines with hydrogen cooling generated only slight mass reductions from the reference, all-hydrogen vehicle. Cross feeding propellants generated the most significant mass reductions from the reference two stage vehicle. The use of high mixture ratio or variable mixture ratio hydrogen engines in the boost phase of flight resulted in vehicles with total dry mass 20 percent greater than the reference hydrogen vehicle. Translating nozzles for boost phase engines generated a heavier vehicle. Also examined were the design impacts on the vehicle and ground support subsystems when subcooled propane is used as a fuel. The most significant cost difference between facilities to handle normal boiling point versus subcooled propane is 5 million dollars. Vehicle cost differences were negligible. A significant technical challenge exists for properly conditioning the vehicle propellant on the ground and in flight when subcooled propane is used as fuel.

Johnson, P.↗