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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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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Effect of a finite ionization rate on the radiative heating of outer planet atmospheric entry probes

The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiation heating of probes entering the hydrogen helium atmospere of the major planets was investigated. At the present time, there is disagreement as to whether the radiative flux increases or decreases relative to its equilibrium value when finite rate ionization is considered. Leibowitz and Kuo content that the finite rate ionization in the hydrogen gas just behind the shock wave reduces the radiative flux to the probe, whereas Tiwari and Szema predict that it increases the radiative flux. The radiation modeling used in the calculations of both pairs of these investigators was reviewed. It is concluded that finite rate ionization in the inviscid region of the shock layer should reduce the cold wall radiative heating below the values predicted by equilibrium chemistry assumptions.

Nelson, H. F.↗
NASA NTRS1982

Effect of a finite ionization rate on the radiative heating of outer planet atmospheric entry probes

The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiative heating of probes entering the hydrogen-helium atmosphere of the major plants was investigated. Two opposing conclusions were reached as to how the ionization rate assumption affects the radiative transfer. Hydrogen-helium shock waves with a cold nonblowing wall boundary condition at the probe heat shield are emphasized. The study is limited to the stagnation shock layer.

Nelson, H. F.↗
NASA NTRS1982

Anomalous behavior of the Pioneer Venus entry probes during lower descent

Four Pioneer Venus Probe spacecraft entered the Venusian atmosphere on December 9 1978, and descended to the surface while making in situ measurements of chemical composition, structure, and radiative balance. In the lower Venusian atmosphere, a number of anomalous events were noted in some of the scientific instruments and Probe engineering data. Many of these anomalies occurred on each of the Probes at approximately the same altitude. The anomalies are thought to be the result of some unexpected electrical interaction between the Probe and the Venusian atmosphere. This conclusion is based on analysis and testing of similar Probe hardware on the ground. However, the possibility that some anomalies were a result of latent design of manufacturing flaws cannot be ruled out.

Polaski, L. J.↗
NASA NTRS1986

A gas chromatograph experiment for a Titan entry probe

Development of a gas chromatographic technique for analysis of aerosols and volatile organics from a Titan probe is now in progress. Preliminary investigations of aerosol collectors have shown that an electrostatic device should be the most efficient for the particle sizes expected in Titan's atmosphere. Such a device particularly lends itself to development of a simple pyrolyzer which can be used to break down any collected organic conglomerate structures into volatile fragments. Those fragments can subsequently be analyzed by GC providing information about the original chemical structure of the aerosols. Studies show that as little as 1 to 5 micrograms of model aerosol can be successfully analyzed. High altitude atmospheric gas sampling will also be important on Titan due to the great depth of the atmosphere. Studies show that a GC analysis of model Titan atmospheres at pressures approximating this altitude can be made with a sensitivity of a few ten's of parts-per-billion for the trace gases of interest.

Carle, G. C.↗
NASA NTRS1985

Thermal net flux measurements on the Pioneer Venus entry probes

Corrected thermal net (upward minus downward flux) radiation data from four Pioneer Venus probes at latitudes of 4 deg and 60 deg N, and 27 deg and 31 deg S, are presented. Comparisons of these fluxes with radiative transfer calculations were interpreted in terms of cloud properties and the global distribution of water vapor in the lower atmosphere of Venus. The presence of an as yet undetected source of IR opacity is implied by the fluxes in the upper cloud range. It was also shown that beneath the clouds the fluxes at a given altitude increase with latitude, suggesting greater IR cooling below the clouds at high latitudes and a decrease of the water vapor mixing ratios toward the equator.

Revercomb, H. E.↗
NASA NTRS1990

Measurement of a zonal wind profile on Titan by Doppler tracking of the Cassini entry probe

A program, called the Cassini mission, intended to study the Saturn system by utilizing a Saturn orbiter and a probe descending to the surface of Titan, is discussed. Winds are expected to cause perturbations to the probe local horizontal velocity, resulting in an anomalous drift in the probe location and a shift in the frequency of the probe telemetry, due to the Doppler effect. By using an iterative algorithm, in which the time variation of the probe telemetry frequency is monitored throughout the descent, and the probe trajectory is updated to reflect the effect of wind on the probe location, a highly accurate relative wind profile can be recovered. By adding a single wind velocity, measured by independent means, an absolute wind profile can be obtained. However, the accuracy of the zonal winds recovery is limited by errors in trajectory, and frequency.

Atkinson, D. H.↗
NASA NTRS1979

Modeling of Radiative Heating in Base Region of Jovian Entry Probe

A theoretical model is derived to determine the average thermodynamic properties in the expanding region, recirculating region, recompression region, and neck region through application of one-dimensional conservation equations. Radiative transfer is calculated using spectrally detailed computer codes accounting for nonequilibrium. The results show that the most severe heating occurs immediately behind the frustum, and that the recompression and neck regions are the major sources of radiation that heats the base stagnation point, The radiation flux to the base point is slightly stronger with ablation than without. Its value is 0.11(43 P(sub b)/P(sub s))(sup 2) times that to the front stagnation point where the base pressure P(sub b) is defined as the average pressure in the recirculating region and P(sub s) is the front stagnation-point pressure. The time-integrated heat load to the base point is 18(43 P(sub b)/P(sub s))(sup 2) kJ/sq cm.

Park, Chul↗
NASA NTRS2001

Saturn Deep Atmospheric Entry Probes Delivered by INSIDE Jupiter Derivative Spacecraft

In situ probes are the most reliable means for sampling composition and conditions deep in giant planet atmospheres. Deep constituent abundances at the giant planets offer clues to conditions in the solar systems protoplanetary disk and variations with heliocentric distance. Currently in situ atmospheric data are available from only one giant planet, Jupiter, and probes that penetrate deeper than the Galileo probe are needed there to measure the deep abundances of such important species as H2O and H2S. Deep probes at Saturn would extend the sampled heliocentric range to Saturn, providing important constraints on the conditions and variability of the protoplanetary disk, and would provide significant new information about Saturn and its evolutionary processes. Such a probe mission could be implemented using a derivative of the INSIDE Jupiter mission's spacecraft as the Carrier/Relay Spacecraft (CRSC), with probes per JPL/Team X and other design studies. Additional information is contained in the original extended abstract.

Spilker, T. R.↗
NASA NTRS1997

Review of Galileo Probe Entry Technology

This talk is a review of the Galileo entry mission with a focus on entry technology, not planetary science. A general description of the mission, entry parameters, and entry vehicle are provided, followed by a more detailed description of the vehicle heatshield shape, size, materials, and instrumentation. The heat shield design tools and process are discussed wish emphasis on the issues and challenges which were faced and the role of ground test facilities. Flight data are compared with the preflight predictions. What have we learned?

Milos, Frank S.↗
NASA NTRS2005

First Results from the Descent Imager/Spectral Radiometer (DISR) Experiment on the Huygens Entry Probe of Titan

The Cassini-Huygens mission was launched on October 15, 1997, and arrived in Orbit around Saturn in July, 2004. The Huygens Probe was released from the Cassini Orbiter on December 24, 2004 and entered Titan s atmosphere on January 14, 2005. Here we give the first results from the Descent Imager/Spectral Radiometer (DISR) instrument aboard the Huygens Probe during its descent into the atmosphere of Titan. Measurements were made by several different optical systems and sensors.

Tomasko, M. G.↗
NASA NTRS2005

The Instrumented Frisbee(Registered TradeMark) as a Prototype for Planetary Entry Probes

A Frisbee has been equipped with sensors, batteries and micro-controllers for data acquisition to record its translational accelerations and attitude motion. The experiments explore the capabilities and limitations of sensors on a rapidly-rotating platform moving in air, and illustrate several of the complex gyrodynamic aspects of frisbee flight. The experiments constitute an instructive exercise in aerospace vehicle systems integration and in attitude reconstruction.

Lorenz, Ralph D.↗