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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

DSMC Simulations of Disturbance Torque to ISS During Airlock Depressurization

The primary attitude control system on the International Space Station (ISS) is part of the United States On-orbit Segment (USOS) and uses Control Moment Gyroscopes (CMG). The secondary system is part of the Russian On orbit Segment (RSOS) and uses a combination of gyroscopes and thrusters. Historically, events with significant disturbances such as the airlock depressurizations associated with extra-vehicular activity (EVA) have been performed using the RSOS attitude control system. This avoids excessive propulsive "de-saturations" of the CMGs. However, transfer of attitude control is labor intensive and requires significant propellant. Predictions employing NASA's DSMC Analysis Code (DAC) of the disturbance torque to the ISS for depressurization of the Pirs airlock on the RSOS will be presented [1]. These predictions were performed to assess the feasibility of using USOS control during these events. The ISS Pirs airlock is vented using a device known as a "T-vent" as shown in the inset in figure 1. By orienting two equal streams of gas in opposite directions, this device is intended to have no propulsive effect. However, disturbance force and torque to the ISS do occur due to plume impingement. The disturbance torque resulting from the Pirs depressurization during EVAs is estimated by using a loosely coupled CFD/DSMC technique [2]. CFD is used to simulate the flow field in the nozzle and the near field plume. DSMC is used to simulate the remaining flow field using the CFD results to create an in flow boundary to the DSMC simulation. Due to the highly continuum nature of flow field near the T-vent, two loosely coupled DSMC domains are employed. An 88.2 cubic meter inner domain contains the Pirs airlock and the T-vent. Inner domain results are used to create an in flow boundary for an outer domain containing the remaining portions of the ISS. Several orientations of the ISS solar arrays and radiators have been investigated to find cases that result in minimal disturbance torque. Figure 1 shows surface pressure contours on the ISS and a plane of number density contours for a particular case.

Lumpkin, F. E., III↗
NASA NTRS2021

Dare Mighty Things

Winston Churchill once said, “To improve is to change; to be perfect is to change often.” JPL’s Property Accountability objective is to provide superior services related to property accountability, reutilization, and disposition. JPL must report property reutilized and disposed through either sales, donation, or scrap. Implementing the JPL designed and built Property Information Reporting System (PIRS), opened a new perspective with our data and what are we reporting to NASA. With this new depth of visibility, we self-implemented as assessment to validate the fiduciary and stewardship responsibilities of what is being reporting to NASA. JPL strives to perform at a level beyond the basic primary expectations of our NASA requirements. JPL developed the PIRS - which rolled out in 2018 - to simplify the delivery of JPL’s Personal Property and Equipment (PP&E) reporting: PIRS takes the raw data from Oracle to generate the NASA Form (NF) 1018 and Contractor Held Asset Reporting System (CHATS) Reports, and to meet the requirements established for AS9100 compliance. The data presented from PIRS is exportable and used to analyze our property records. JPL is also embarking on an effort to define the JPL of the future with “Enterprise 2.0”. Enterprise 2.0 is the driving force of JPL’s strategy to digitally transform the Laboratory from the current legacy processes and systems to a modern, integrated, information-driven highway of business transactions. This should include automation of routine processes and data-related tasks, integration of data and systems, advanced search and analytics, and improved information sharing and collaboration. As JPL’s evolving landscape of digital technologies advance to meet the future, JPL Property Accountability is making strides to surpass these expectations. For every cause there is an effect: a revealing of something that aids in the further development and transformation of JPL best business practices.

Sucher, Jay M↗
NASA NTRS2001

Determination of the Thermal Offset of the Eppley Precision Spectral Pyranometer

Eppley's precision spectral pyranometer (PSP) is used in networks around the world to measure downwelling diffuse and global solar irradiance at the surface of the Earth. In recent years several studies have shown significant discrepancy between irradiances measured by pyranometers and those computed by atmospheric radiative transfer models. Pyranometer measurements have been questioned because observed diffuse irradiances sometimes are below theoretical minimum values for a pure molecular atmosphere, and at night the instruments often produce nonzero signals ranging between + 5 and - 10 W/sq m. We install thermistor sondes in the body of a PSP as well as on its inner dome to monitor the temperature gradients within the instrument, and we operate a pyrgeometer (PIR) instrument side by side with the PSP. We derive a relationship between the PSP output and thermal radiative exchange by the dome and the detector and a relationship between the PSP output and the PIR thermopile output (net-IR). We determine the true PSP offset by quickly capping the instrument at set time intervals. For a ventilated and shaded PSP, the thermal offset can reach - 15 W/sq m under clear skies, whereas it remains close to zero for low overcast clouds. We estimate the PSP thermal offset by two methods: (1) using the PSP temperatures and (2) using the PIR net-IR signal. The offset computed from the PSP temperatures yields a reliable estimate of the true offset (+/- 1 W/sq m). The offset computed from net-IR is consistent with the true offset at night and under overcast skies but predicts only part of the true range under clear skies.

Haeffelin, Martial↗
NASA NTRS2021

Meta-aerogels: Auxetic Shape-memory Polyurethane Aerogels

Shape-memory poly(isocyanurate-urethane) (PIR-PUR) aerogels are low-density monolithic nanoporous solids that remember and return to their permanent shape through a heating actuation step. Herein, through structural design at the macro scale, the shape-memory response is augmented with an auxetic effect manifested by a negative Poisson’s ratio of approximately -0.8 at 15% compressive strain. Thus, auxetic shape-memory PIR-PUR monoliths experience volume contraction upon compression at a temperature above the glass transition temperature of the base polymer (Tg ~ 30 °C), and they can be stowed indefinitely in that temporary shape by cooling below Tg. By heating back above Tg, the compressed/shrunk form expands back to their original shape/size. This technology is relevant to a broad range of industries spanning the commercial, aeronautical, and aerospace sectors. The materials are referred to as meta-aerogels and their potential applications include minimally invasive medical devices, soft robotics, and in situations where volume is at a premium, as for example for storage of deployable space structures and planetary habitats during transport to the point of service.

Sadeq Malakooti↗
NASA NTRS1979

Radar observations of asteroid 1 Ceres

Radar observations of asteroid 1 Ceres were made at a 12.6-cm wavelength from the Arecibo Observatory in March/April 1977. The measurements, made with a received circular polarization orthogonal to that transmitted, yield a radar cross section of (0.04 + or- 0.01) piR-squared, for R = 510 km. The corresponding radar reflectivity is less than that measured for any other celestial body. Within the accuracy of measurement, no significant variation of cross section with rotational phase is apparent. The shape of the power spectrum suggests that Ceres is rougher at the scale of the observing wavelength than the moon and inner planets, but smoother than the outer three Galilean satellites.

Ostro, S. J.↗
NASA NTRS1987

Intelligent process development of foam molding for the Thermal Protection System (TPS) of the space shuttle external tank

A knowledge based system to assist process engineers in evaluating the processability and moldability of poly-isocyanurate (PIR) formulations for the thermal protection system of the Space Shuttle external tank (ET) is discussed. The Reaction Injection Molding- Process Development Advisor (RIM-PDA) is a coupled system which takes advantage of both symbolic and numeric processing techniques. This system will aid the process engineer in identifying a startup set of mold schedules and in refining the mold schedules to remedy specific process problems diagnosed by the system.

Bharwani, S. S.↗
NASA NTRS1990

Temperature sensitivity of Eppley broadband radiometers

Broadband radiometers manufactured by Eppley Laboratories Inc. are commonly used to measure irradiance from both ground-based and aircraft platforms. Namely, the pyranometer (Model PSP) measures irradiance in the .3 to 3.0 micron spectral region while the pyrgeometer (Model PIR) senses energy in the 4 to 50 micron region. The two instruments have a similar thermopile construction but different filters to achieve the appropriate spectral selection. During the fall of 1986, the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) commenced with the first cirrus Intensive Field Observation (IFO) conducted in Central Wisconsin. Due to the nature of this field project, pyranometers and pyrgeometers manufactured by Eppley were flown on NCAR's high altitude research aircraft, the Sabreliner. Inherent in the construction of these radiometers is temperature compensation circuitry designed to make the instrument sensitivity nominally constant over a temperature range from -20 to +40 C. Because the Sabreliner flew at high altitudes where temperatures were as cold as -70 C, it was necessary to determine the radiometers relative sensitivity to temperatures below -20 C and apply appropriate corrections to the FIRE radiation data set. A procedure to perform this calibration is outlined. It is meant to serve as a supplement to calibration procedures.

Smith, William L., Jr.↗
NASA NTRS1994

Simulation study of the ROMPS robot control system

This is a report presenting the progress of a research grant funded by NASA for work performed from June 1, 1993 to August 1, 1993. The report deals with the Robot Operated Material Processing System (ROMPS). It presents results of a computer simulation study conducted to investigate the performance of the control systems controlling the azimuth, elevation, and radial axes of the ROMPS and its gripper. Four study cases are conducted. The first case investigates the control of free motion of the three areas. In the second case, the compliant motion in the elevation axis with the wrist compliant device is studied in terms of position accuracy and impact forces. The third case focuses on the behavior of the control system in controlling the robot motion along the radial axis when pulling the pallet out of the rack. In the fourth case, the compliant motion of the gripper grasping a solid object under the effect of the gripper passive compliance is studied in terms of position accuracy and contact forces. For each of the above cases, a set of PIR gains will be selected to optimize the controller performance and computer simulation results will be presented and discussed.

Nguyen, Charles C.↗
NASA NTRS2005

California Space Grant Consortium

The organizational and administrative structure of the CaSGC has the Consortium Headquarters Office (Principal Investigator - Dr. John Kosmatka, California Statewide Director - Dr. Michael Wiskerchen) at UC San Diego. Each affiliate member institution has a campus director and an scholarship/fellowship selection committee. Each affiliate campus director also serves on the CaSGC Advisory Council and coordinates CMIS data collection and submission. The CaSGC strives to maintain a balance between expanded affiliate membership and continued high quality in targeted program areas of aerospace research, education, workforce development, and public outreach. Associate members are encouraged to participate on a project-by-project basis that meets the needs of California and the goals and objectives of the CaSGC. Associate members have responsibilities relating only to the CaSGC projects they are directly engaged in. Each year, as part of the CaSGC Improvement Plan, the CaSGC Advisory Council evaluates the performance of the affiliate and associate membership in terms of contributions to the CaSGC Strategic Plan, These CaSGC membership evaluations provide a constructive means for elevating productive members and removing non-performing members. This Program Improvement and Results (PIR) report will document CaSGC program improvement results and impacts that directly respond to the specific needs of California in the area of aerospace-related education and human capital development and the Congressional mandate to "increase the understanding, assessment, development and utilization of space resources by promoting a strong education base, responsive research and training activities, and broad and prompt dissemination of knowledge and technology".

Kosmatka, John↗
NASA NTRS2008

Improving the Optical Quality Factor of the WGM Resonator

Resonators usually are characterized with two partially dependent values: finesse (F) and quality factor (Q). The finesse of an empty Fabry-Perot (FP) resonator is defined solely by the quality of its mirrors and is calculated as F=piR(exp 1/2)/(1-R). The maximum up-to-date value of reflectivity R approximately equal to 1 - 1.6 x 10(exp -6) is achieved with dielectric mirrors. An FP resonator made with the mirrors has finesse F=1.9 x 10(exp 6). Further practical increase of the finesse of FP resonators is problematic because of the absorption and the scattering of light in the mirror material through fundamental limit on the reflection losses given by the internal material losses and by thermodynamic density fluctuations on the order of parts in 109. The quality factor of a resonator depends on both its finesse and its geometrical size. A one-dimensional FP resonator has Q=2 F L/lambda, where L is the distance between the mirrors and lambda is the wavelength. It is easy to see that the quality factor of the resonator is unlimited because L is unlimited. F and Q are equally important. In some cases, finesse is technically more valuable than the quality factor. For instance, buildup of the optical power inside the resonator, as well as the Purcell factor, is proportional to finesse. Sometimes, however, the quality factor is more valuable. For example, inverse threshold power of intracavity hyperparametric oscillation is proportional to Q(exp 2) and efficiency of parametric frequency mixing is proportional to Q(exp 3). Therefore, it is important to know both the maximally achievable finesse and quality factor values of a resonator. Whispering gallery mode (WGM) resonators are capable of achieving larger finesse compared to FP resonators. For instance, fused silica resonators with finesse 2.3 x 10(exp 6) and 2.8 x 10(exp 6) have been demonstrated. Crystalline WGM resonators reveal even larger finesse values, F=6.3 x 10(exp 6), because of low attenuation of light in the transparent optical crystals. The larger values of F and Q result in the enhancement of various nonlinear processes. Low-threshold Raman lasing, optomechanical oscillations, frequency doubling, and hyperparametric oscillations based on these resonators have been recently demonstrated. Theory predicts a possibility of nearly 10(exp 14) room-temperature optical Q-factors of optical crystalline WGM resonators, which correspond to finesse levels higher than 10(exp 9). Experiments have shown numbers a thousand times lower than that. The difference occurs due to media imperfections. To substantially reduce the optical losses caused by the imperfections, a specific, multi-step, asymptotic processing of the resonator is implemented. The technique has been initially developed to reduce microwave absorption in dielectric resonators. One step of the process consists of mechanical polishing performed after high temperature annealing. Several steps repeat one after another to lead to significant reduction in optical attenuation and, as a result, to the increase of Q-factor as well as finesse of the resonator which demonstrates a CaF2 WGM resonator with F greater than 10(exp 7) and Q greater than 10(exp 11).

Savchenkov, Anatoliy↗