Data for EMSL Project 50414 from May 2024
Explore the source record for details and available documents.
Valiev, Marat↗
Engineering topics
Baker, David
Publications and source records attributed to Baker, David.
Top-down Atmospheric Inventories of CO2 and CH4 to Support the Global Stocktakes
No abstract provided
Tanimoto, Hiroshi↗
Is There an Optimal CO2 Partial Column for Flux Inversions?
The fidelity of flux estimates from an atmospheric inversion depends on the ability of atmospheric transport models to simulate the measured quantity. For species such as CO2, with surface fluxes and a large network of surface measurements, this means correctly simulating the dynamics of the planetary boundary layer (PBL), which is one of the most uncertain aspects of atmospheric transport modeling. In contrast, the simulated total column average mole fraction of CO2 (XCO2) is largely insensitive to simulated PBL dynamics. Therefore, measurements of XCO2 provided by current and future short wave infrared (SWIR) greenhouse gas (GHG) satellites such as GOSAT and the OCO family would seem to be more appropriate to flux inversions, as far as minimizing transport model errors (the "noise") is concerned. Unfortunately, the flux-induced variation of CO2 (the "signal") is the largest within the PBL and smallest in XCO2. Therefore, assimilating XCO2 as opposed to PBL CO2 need not give us the strongest "signal to noise" in flux inversions. Recent work on GOSAT and OCO2 retrievals suggest that SWIR satellite spectra may be used to estimate a lower partial column CO2, which could be assimilated in a flux inversion, instead of XCO2.Here we report on a study to assess whether there is an optimal partial column average CO2, intermediate between PBL CO2 and XCO2, whose assimilation might yield the best signal to noise in flux inversions, where (as before) "signal" is the flux-induced variation and "noise" is the error in transport modeling. We simulate atmospheric CO2 with five different global transport models and a common surface CO2 flux over ten years. We consider the spread across the five models to be a proxy for transport model error (the "noise"), and the common variation of CO2 in all five models to be a proxy for the "signal". We compare these signals and noises at different spatiotemporal scales for different partial column specifications to investigate whether there exists an optimal partial column that has large surface flux-driven variations and yet is relatively insensitive to errors in transport models. Finally, we comment on the feasibility of estimating such a partial column from current and future SWIR GHG satellites in the light of recent work on vertically resolved CO2 from current SWIR GHG satellites.
Basu, Sourish↗
Hypergol Systems: Design, Buildup, and Operation
This course was developed by personnel at the NASA JSC White Sands Test Facility in conjunction with the NASA Safety Training Center (NSTC). The NSTC was established in May 1991 by the NASA Headquarters Safety Directorate to provide up-to-date, high-quality, NASA specific safety training on location at NASA centers, or simultaneously to multiple centers over the Video Teleconferencing System (ViTS). Our desire is to establish and maintain a strong, long-lasting relationship with all NASA centers in order to fulfill your safety training needs on a cost-effective basis. Our ultimate goal is to provide a positive contribution to safe operations at NASA. NSTC Course 055 is a 2-day course discussing the safe usage of hypergols (hydrazine fuels and nitrogen tetroxide). During the course we will identify the hazards associated with hypergols including toxicity, reactivity, fire, and explosion. Management of risk is discussed in terms of the primary engineering controls design, buildup, and operation; and secondary controls personal protective equipment and detectors/monitors. The emphasis is on the design and buildup of compatible systems and the safe operation of these systems by technicians and engineers.
Baker, David↗
Fuel Oxidizer Reaction Products (FORP) Contamination of Service Module (SM) and Release of N-nitrosodimethylamine(NDMA)in a Humid Environment from Crew EVA Suits Contaminated with FORP
The Service Module (SM) is an element of the Russian Segment of the International Space Station (ISS). One of the functions of the SM is to provide attitude control for the ISS using thrusters when the U.S. Control Moment Gyros (CMG's) must be desaturated. Prior to an Extravehicular Activity (EVA) on the Russian Segment, the Docking Compartment (DC1) is depressurized, as it is used as an airlock. When the DC1 is depressurized, the CMG's margin of momentum is insufficient and the SM attitude control thrusters need to fire to desaturate the CMG's. SM roll thruster firings induce contamination onto adjacent surfaces with Fuel Oxidizer Reaction Products (FORP). FORP is composed of both volatile and non-volatile components. One of the components of FORP is the potent carcinogen N-nitrosdimethylamine (NDMA). Since the EVA crewmembers often enter the area surrounding the thrusters for tasks on the aft end of the SM and when translating to other areas of the Russian Segment, the presence of FORP is a concern. This paper will discuss FORP contamination of the SM surfaces, the release of NDMA in a humid environment from crew EVA suits, if they happen to be contaminated with FORP, and the toxicological risk associated with the NDMA release.
Schmidl, William↗
Hydrogen Peroxide - Material Compatibility Studied by Microcalorimetry
Environmental and toxicity concerns with current hypergolic propellants have led to a renewed interest in propellant grade hydrogen peroxide (HP) for propellant applications. Storability and stability has always been an issue with HP. Contamination or contact of HP with metallic surfaces may cause decomposition, which can result in the evolution of heat and gas leading to increased pressure or thermal hazards. The NASA Johnson Space Center White Sands Test Facility has developed a technique to monitor the decompositions of hydrogen peroxide at temperatures ranging from 25 to 60 C. Using isothermal microcalorimetry we have measured decomposition rates at the picomole/s/g level showing the catalytic effects of materials of construction. In this paper we will present the results of testing with Class 1 and 2 materials in 90 percent hydrogen peroxide.
Homung, Steven D.↗
Scientific American Inventions From Outer Space: Everyday Uses For NASA Technology
The purpose of this book is to present some of the inventions highlighted in the yearly publication of the National Aeronautics and Space Administration (NASA) Spinoff. These inventions cover a wide range, some of which include improvements in health, medicine, public safety, energy, environment, resource management, computer technology, automation, construction, transportation, and manufacturing technology. NASA technology has brought forth thousands of commercial products which include athletic shoes, portable x-ray machines, and scratch-resistant sunglasses, guidance systems, lasers, solar power, robotics and prosthetic devices. These products are examples of NASA research innovations which have positively impacted the community.
Baker, David↗
Pump, and earth-testable spacecraft capillary heat transport loop using augmentation pump and check valves
A spacecraft includes heat-generating payload equipment, and a heat transport system with a cold plate thermally coupled to the equipment and a capillary-wick evaporator, for evaporating coolant liquid to cool the equipment. The coolant vapor is coupled to a condenser and in a loop back to the evaporator. A heated coolant reservoir is coupled to the loop for pressure control. If the wick is not wetted, heat transfer will not begin or continue. A pair of check valves are coupled in the loop, and the heater is cycled for augmentation pumping of coolant to and from the reservoir. This augmentation pumping, in conjunction with the check valves, wets the wick. The wick liquid storage capacity allows the augmentation pump to provide continuous pulsed liquid flow to assure continuous vapor transport and a continuously operating heat transport system. The check valves are of the ball type to assure maximum reliability. However, any type of check valve can be used, including designs which are preloaded in the closed position. The check valve may use any ball or poppet material which resists corrosion. For optimum performance during testing on Earth, the ball or poppet would have neutral buoyancy or be configured in a closed position when the heat transport system is not operating. The ball may be porous to allow passage of coolant vapor.
Baker, David↗
Optimal attitude maneuver execution for the Advanced Composition Explorer (ACE) mission
The Advanced Composition Explorer (ACE) spacecraft will require frequent attitude reorientations in order to maintain the spacecraft high gain antenna (HGA) within 3 deg of earth-pointing. These attitude maneuvers will be accomplished by employing a series of ground-commanded thruster pulses, computed by ground operations personnel, to achieve the desired change in the spacecraft angular momentum vector. With each maneuver, attitude nutation will be excited. Large nutation angles are undesirable from a science standpoint. It is important that the thruster firings be phased properly in order to minimize the nutation angle at the end of the maneuver so that science collection time is maximized. The analysis presented derives a simple approximation for the nutation contribution resulting from a series of short thruster burns. Analytic equations are derived which give the induced nutation angle as a function of the number of small thruster burns used to execute the attitude maneuver and the phasing of the burns. The results show that by properly subdividing the attitude burns, the induced nutation can be kept low. The analytic equations are also verified through attitude dynamics simulation and simulation results are presented. Finally, techniques for quantifying the post-maneuver nutation are discussed.
Woodard, Mark A.↗
Humans to Mars in 1999
A set of vehicle designs and a mission architecture that was developed to send humans to Mars in the 1990's are discussed. Launching, landing, a 500 day stay on Mars, and a return to Earth are discussed. The plan is not merely a one shot expedition, but puts into place immediately an economical method of Earth-Mars transportation, real surface exploratory mobility, and significant base capabilities that can rapidly evolve into a mostly self-sufficient Mars colony. Since the plans call for the use of a combination of off the shelf technology and new technology that can be easily developed, the authors argue that there is no reason to postpone the exploration of Mars until several decades after a lunar base build-up.
Zubrin, Robert↗