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Hall, J. L.

Publications and source records attributed to Hall, J. L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

A Gas Management System for an Ultra Long Duration Titan Blimp

This paper presents analyses, designs and experimental results for the gas management system of a hydrogen-filled blimp capable of flying in the lower atmosphere of Titan for a period of one year or more. The engineering strategy has two basic elements: first, to minimize leakage rates from the blimp envelope and ballonets; and second, to provide auxiliary subsystems to mitigate the life-limiting effects resulting from those leaks. Leak minimization is achieved through use of cryogenically compatible balloon materials and adhesives, and selection of ballonet geometries that minimize pinhole generation via folding and material fatigue. Hydrogen loss to the environment through leaks in the blimp envelope is compensated for by producing new hydrogen through chemical processing of atmospheric methane. Nitrogen leaked into the blimp from the ballonets is removed by a carbon absorption system and periodically vented to the atmosphere. Data is presented on the measured leak rate from a full scale (13 m long) prototype blimp envelope and on the performance of a low mass, low power prototype device that generates hydrogen from methane. These results are factored in to an overall system design that quantifies the mass and power requirements for a minimum one year operational lifetime.

aerobot↗
NASA NTRS2008

Second Generation Prototype Design and Testing for a High Altitude Venus Balloon

This paper describes the development of a second generation prototype balloon intended for flight in the upper atmosphere of Venus. The design of this new prototype incorporates lessons learned from the construction and testing of the first generation prototype, including finite element analyses of the balloon stresses and deformations, measured leak performance after handling and packaging, permeability and optical property measurements on material samples, and sulfuric acid testing. An improved design for the second generation prototype was formulated based on these results, although the spherical shape and 5.5 m diameter size were retained. The resulting balloon has a volume of 87 cubic meters and is capable of carrying a 45 kg payload at a 55 km altitude at Venus. The design and fabrication of the new prototype is described, along with test data for inflation and leakage performance.

mobility↗
NASA NTRS2005

Dual Balloon Concept for Lifting Payloads from the Surface of Venus

Introduction: Two high-rated Venus mission concepts proposed in the National Science Foundation Decadal Survey require a balloon to lift payloads from Venusian surface to high altitudes: Venus Surface Sample Return (VESSR) and Venus In-Situ Explorer (VISE). In case of VESSR the payload is a canister with the surface sample plus a Venus ascent vehicle (VAV), which is a rocket that takes the sample into orbit for rendezvous with an Earth return vehicle. VISE is envisioned as a more limited precursor mission where the surface sample is only taken to high altitudes so that non time-critical analyses can be performed. From the balloon point of view, the only difference between these two missions is that the VESSR payload to be lifted is very much larger than VISE because of the inclusion of the VAV. A key problem is that at the time the decadal survey was published, no high temperature balloon technology existed to implement either mission. Prior technology development efforts had concentrated on a single balloon that could operate across the entire 0-60 km altitude range, tolerating both the sulfuric acid aerosols and the extreme temperatures of -10 to +460 C. However, this problem was unsolved because no combination of sufficiently lightweight balloon material and manufacturing (seaming) technology was ever found to tolerate the high temperatures at the surface.

Kerzhanovich, Viktor V.↗
NASA NTRS2005

An Approach to In-Situ Observations of Volcanic Plumes

Volcanoes have long been recognized as playing a dominant role in the birth, and possibly the death, of biological populations. They are possible sources of primordial gases, provide conditions sufficient for creating amino acids, strongly affect the heat balance in the atmosphere, and have been shown to sustain life (in oceanic vents.) Eruptions can have profound effects on local flora and fauna, and for very large eruptions, may alter global weather patterns and cause entire species to fail. Measurements of particulates, gases, and dynamics within a volcanic plume are critical to understanding both how volcanoes work and how plumes affect populations, environment, and aviation. Volcanic plumes and associated eruption columns are a miasma of toxic gases, corrosive condensates, and abrasive particulates that makes them hazardous to nearby populations and poses a significant risk to all forms of aviation. Plumes also provide a mechanism for sampling the volcanic interior, which, for hydrothermal environments, may host unique biological populations.

Smythe, W. D.↗
NASA NTRS2004

An aerobot for global in situ exploration of Titan

This paper describes the design and component testing of an aerobot that would be capable of global in situ exploration of Saturn's moon, Titan, over a 6 to 12 month mission lifetime. The proposed aerobot is a propeller-driven, buoyant vehicle that resembles terrestrial airships. However, the extremely cold Titan environment requires the use of cryogenic materials of construction and careful thermal design for protection of temperature-sensitive payload elements. Multiple candidate balloon materials have been identified based on extensive laboratory testing at 77 K.

aerobot↗
NASA NTRS2002

An overview of the aerocapture flight test experiment (AFTE)

The paper describes the technical details underlying the AFTE mission scenario and discusses how the results would benefit the future aerocapture missions and related hypersonic flight applications like precision landing.

aerocapture aeroshell flight test↗
NASA NTRS2002

Titan airship explorer

The aerobots can be used for in situ studies of the surface while landing or winching down an instrumented surface platform.

planetary aerobots Titan↗
NASA NTRS2000

A Contaminant Ice Visualization Experiment in a Glass Pulse Tube

Results are presented from pulse tube experiments designed to investigate the effect of 400 parts per million water vapor contamination of the helium working gas. The experiments were conducted in a glass pulse tube to enable visualization of ice formation on internal surfaces. Photographs of this ice formation were taken along with simultaneous coldtip temperature and compressor power measurements. Four types of regenerator elements were tested in various combinations: 200- and 400-mesh stainless steel screens, 1.6 mm diameter glass beads, and 1.6 mm thick perforated plastic plates. Internal spacers were also used to provide clear fields of view into the regenerator stack. Substantial water-ice formation was observed at the cold end of the regenerator and on the inside wall of pulse tube; it appeared to be highly porous, like snow, and was seen to accumulate only in a very localized region at the coldest end, despite changing the cold tip temperature across a range of 150 to 235 K. Ice formation degraded pulse tube thermal performance only in cases where screen regenerators were used at the regenerator cold end. It was concluded that flow blockage was the mechanism by which contaminants affected performance; coarse regenerator elements were largely immune over the tested time scale of a few days. Substantially reduced ice formation and minimal performance loss were also observed in repeated tests where the contaminated gas was reused after warming up and melting of the accumulated internal ice. Significant adsorption of the liquid water onto the regenerator was inferred, a process that depleted the gas phase concentration of water.

Hall, J. L.↗
NASA NTRS1999

MABVAP: One Step Closer to an Aerobot Mission to Mars

Lighter-than-air planetary missions continued attract growing interest in Mars exploration due to unique combination of proximity to the surface and mobility that far surpasses capability of surface vehicles. Following the experience with the Sojourner rover and subsequent development of powerful rovers for Mars 2003 and 2005 missions it became clear that on Mars surface rover mobility is quite restricted. Realistic travel distances may be limited to tens of kilometers per year on relatively obstacle-free plains and a few kilometers or less on the more rugged terrains. Many areas on Mars will be inaccessible to rovers. Several concepts for a Mars aerobot (robotic balloon) mission have been pursued in the last decade. Additional information is contained in the original extended abstract.

Kerzhanovich, V. V.↗
NASA NTRS1990

Improved Kennedy-Thorndike experiment to test special relativity

A modern version of the Kennedy-Thorndike experiment was carried out by searching for sidereal variations between the frequency of a laser locked to an I2 reference line and a laser locked to the resonance frequency of a highly stable cavity. No variations were found at the level of 2 x 10 to the -12th. This represents a 300-fold improvement over the original Kennedy-Thorndike experiment and allows the Lorentz transformations to be deduced entirely from experiment at an accuracy level of 70 ppm.

Hils, Dieter↗
NASA NTRS1990

Microwave and optical lunar transponders

The scientific areas which used data from the Lunar Laser Ranging Experiment, collected from measurements to the Apollo 11, 14, and 15 and Lunakhod 2, include lunar science (i.e., studies of variations in the lunar angular orientation from that for uniform rotation, lunar tidal displacements, and the lunar mass distribution), geodynamics, astrometry, and gravitational physics. This paper argues that the placement of microwave and optical transponders on the moon would improve the accuracy of laser range measurements by nearly two orders of magnitude and would simplify the measurements. The K-band microwave transponders would be operated at the lunar base and at two remote sites on the moon surface, yielding much improved lunar libration and tidal displacement measurements. A two-wavelength laser transponder also would be operated at the lunar base, allowing accurate tropospheric propagation corrections to be made. This would introduce major improvements in measurements of the lunar orbit and of the earth's rotation, and in tests of general relativity.

Bender, P. L.↗
NASA NTRS1989

Optical interferometer in space

The present design concepts for a Laser Gravitational Wave Observatory in Space are described. Laser heterodyne distance measurements are made between test masses located in three spacecraft separated by roughly 10(exp 6) km. The major technology issues are: the reduction of spurious acceleration noise for the test masses to below 2 x 10(exp -15) cm/sq sec/Hz(0.5) from 10(exp -5) to 10(exp -3) Hz; and the measurement of changes in the difference of the antenna arm lengths to 5 x 10(exp -11) cm/Hz(0.5) from 10(exp -3) to 1 Hz with high reliability. The science objectives are: to measure discrete sinusoidal gravitational wave signals from individual sources with periods of 1 second to 1 day; to measure the stochastic background due to unresolved binaries; and to search for gravitational wave pulses with periods longer than 1 sec from possible exotic sources such as gravitational collapse of very massive objects.

Bender, Peter L.↗