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Jacobs, S.

Publications and source records attributed to Jacobs, S..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Martian Dust Particle Size During the 2018 Planet-Encircling Dust Storm as Measured by the Curiosity Rover

We present retrievals of dust particle effective radius during the 2018 planet-encircling dust storm from the Mars Science Laboratory Curiosity rover. Four independent observations with three of the rover's instruments were used for retrievals. We find dust particle radii exceeded 4 m and possibly 5 m during the height of the storm, which represent the largest dust particles yet seen in the martian atmosphere.

Guzewich, S. D.↗
NASA NTRS2002

Rapid bottom melting widespread near Antarctic ice sheet grounding lines

As continental ice from Antartica reaches the grounding line and begins to float, its underside melts into the ocean. Results obtained with satellite radar interferometry reveal that bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed.

glaciology↗
NASA NTRS1993

Dimensional Stability of High Purity Invar 36

High performance requirements for the Imaging Science Subsystem (ISS)/Narrow Angle Camera (NAC) instrument on the NASA/Jet Propulsion Laboratory (JPL) Cassini spacecraft impose very stringent demands for dimensional stability of metering rods in the camera's athermalizing system.

imaging↗
NASA NTRS1992

Anodized aluminum coatings for thermal control. I - Coating process and stresses

Anodized aluminum is a candidate material for use as a thermal radiator surface on Space Station Freedom. Here, results of measurements of coating stress at room temperature are presented. The effects of coating process conditions and also subsequent exposure to different humidities, from above ambient to vacuum, are reported. The most important observation with regard to space applications is that the coating stress is very dependent on humidity, changing from compressive at ambient humidity to strongly tensile in 10 exp -6 torr vacuum. The increase in stress is accompanied by loss of water from the coating, and the process is reversible.

Alwitt, R. S.↗
NASA NTRS1992

Anodized aluminum coatings for thermal control. II - Environmental effects and cracking

The environmental effects of thermal cycling and humidity on coating cracking are examined. Experimental measurements of thermal deflection were used to calculate values for the thermal expansion coefficient and the in situ elastic modulus of an anodized aluminum. The thermal expansion coefficient is found to be approximately the same as for alumina in bulk form. The modulus in atmospheres with less than 100 ppm water is about 12,500 ksi. Two sets of experiments are used to study cracking directly during thermal excursions: one determines the minimum temperature (Tc) at which cracks first appear during a single heating cycle and the other involves rapid thermal cycling (RTC) between fixed T max and T min values. Fatigue models for describing initiation of the first crack and the development of multiple cracking are presented, which can be used as the basis for prediction of LEO cracking.

Mcclung, R. C.↗
NASA NTRS1986

Space station contamination considerations

The external induced environment generated by space station activity, or more specifically by gases, particles, and light background is discussed. These contaminant species must be controlled if sensitive systems, such as solar energy collectors or science experiments exposed to the external environment are to function properly. The requirements generally set limits on the level of gas species, matter deposited on surfaces and light background levels over various spectral regions. They also address environment monitoring and contamination controls during manufacturing. Limits on effluent release and system leakages are in turn derived from these requirements.

Leger, L.↗
NASA NTRS1985

Shuttle on-orbit contamination and environmental effects

Ensuring the compatibility of the space shuttle system with payloads and payload measurements is discussed. An extensive set of quantitative requirements and goals was developed and implemented by the space shuttle program management. The performance of the Shuttle system as measured by these requirements and goals was assessed partly through the use of the induced environment contamination monitor on Shuttle flights 2, 3, and 4. Contamination levels are low and generally within the requirements and goals established. Additional data from near-term payloads and already planned contamination measurements will complete the environment definition and allow for the development of contamination avoidance procedures as necessary for any payload.

Leger, L. J.↗
NASA NTRS1983

Space Shuttle contamination measurements from flights STS-1 through STS-4

Results of contamination measurements performed on the initial four flights of the Space Shuttle Orbiter are summarized and compared with requirements contained in the Space Shuttle Flight and Ground System Specifications and those formulated by the Contamination Requirements Definition Group. In general, the results of measurements carried out with the induced environment contamination monitor indicate that molecular fluxes, deposition rates, and average counts of particulates are within the requirements and close to predicted values. Among the exceptions, were such special circumstances as water dumps, payload bay door closures, and RCS engine, APU, and flash evaporator operations which led to molecular and particulate contamination levels exceeding the limits. In cases where these circumstances would interfere with sensitive payload operations, careful mission planning to preclude a contamination source by operational limitation should be done to avoid losses.

Ehlers, H. K. F.↗
NASA NTRS1982

Space Shuttle preliminary. Contamination assessment from STS-1 and STS-2

A preliminary assessment of the space shuttle contamination environment was made using data from the first two orbital flight tests, STS-1 and STS-2. Data sources consisted of crew observations during flight, postflight vehicle inspection, and the induced environment contamination monitor which was used on STS-2 and consists of 10 instruments. These instruments are used to measure gas phase contaminants, particle population, humidity, and molecular deposition in the orbiter payload bay during ascent and descent and particle population, molecular deposition, and gas cloud during orbital flight. Results of the measurements described are presented in summary form and indicate low molecular deposition rates for both pressurized and orbital flight.

Leger, L. J.↗
NASA NTRS1982

Shuttle payload integration - Contamination aspects

As part of the development of the Space Shuttle, a payload integration system has been established. This integration system or process encompasses several technical disciplines, one of which is concerned with the control of molecular and particulate contamination. Specific integration procedures and documentation have evolved that reflect the incorporation of payload/Space Transportation System contamination requirements and capabilities. Of the 38 payloads in the payload integration system currently, about 20% are considered sensitive to contamination in that special precautions must be taken to ensure that contamination from the Space Shuttle Orbiter does not impair payload function. Most of these payload requirements have been satisfied by the incorporation of controlled ground operations discipline and installation of a payload bay liner, which isolates the payload from the Orbiter systems. Some payloads, however, provide covers for sensitive payload instrumentation.

Jacobs, S.↗
NASA NTRS1980

STS-1 mission contamination evaluation approach

The space transportation system 1 mission will be the first opportunity to assess the induced environment of the orbiter payload bay region. Two tools were developed to aid in this assessment. The shuttle payload contamination evaluation computer program was developed to provide an analytical tool for prediction of the induced molecular contamination environment of the space shuttle orbiter during its onorbit operations. An induced environment contamination monitor was constructed and tested to measure the space shuttle orbiter contamination environment inside the payload bay during ascent and descent and inside and outside the payload bay during the onorbit phase. Measurements are to be performed during the four orbital flight test series. Measurements planned for the first flight are described and predicted environmental data are discussed. The results indicate that the expected data are within the measurement range of the induced environment contamination monitor instruments evaluated, and therefore it is expected that useful contamination environmental data will be available after the first flight.

Jacobs, S.↗
NASA NTRS1978

Space Shuttle contamination overview

Consideration is given to particle and gaseous contamination associated with Shuttle payload orbital delivery. An approach to control contamination is discussed which consists of analytical environment assessment, vehicle design optimization, and flight environment measurement. The analytical assessment of orbital contamination source characteristics and their effects on the Shuttle orbital environment has resulted in vehicle design changes and a detailed understanding of system operational flexibility. Verification of resulting Shuttle contamination performance will be made by the Induced Environment Contamination Monitor.

Leger, L.↗
NASA NTRS1975

Skylab parasol material evaluation

Results of experimental work to evaluate the degradation rate of a parasol that was used as a means of alleviating thermal problems encountered soon after the launch of the Skylab 1 space vehicle are presented. Material selection criteria are discussed; the material chosen is described, and results of tests performed after environmental exposure at five facilities are given. The facilities used for exposure to ultraviolet radiation/thermal-vacuum environments and the equipment used for testing physical properties before and after exposure are described. Comparisons of ground test and flight test data are included.

Jacobs, S.↗
NASA NTRS1975

Skylab parasol material evaluation

Results of experimental work to evaluate the degradation rate of a parasol that was used to alleviate thermal problems encountered soon after the launch of the Skylab 1 space vehicle are presented.

Jacobs, S.↗
NASA NTRS1972

Introduction

The rationale and objectives for landing an Apollo mission near a Surveyor spacecraft on the moon are discussed. Surveyor 3 and the planning of the Apollo 12 flight are considered. Mission operations and returned material, including material handling, are reviewed. The analysis of the returned parts, soil, and photographs is considered.

Carroll, W. F.↗