Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Earth gravity”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

OSIRIS-REx Conjunction Screenings: Earth Gravity Assist and Earth Return Analysis and Results

The NASA OSIRIS-REx asteroid sample return mission performed an Earth gravity assist on September 22, 2017, and returned to Earth to drop off the sample on September 24, 2023. In each case, the NASA Conjunction Assessment Risk Analysis (CARA) team screened the OSIRIS-REx trajectories against the satellite catalog in search of high-risk close approaches. This paper describes the preparation for collision avoidance and screening results, along with lessons learned, providing a baseline for support of future missions in this category, particularly as space traffic around the Earth and in cis-lunar space continues to rapidly expand.

Dolan E. Highsmith↗
NASA NTRSDate not supplied

OSIRIS-REx Conjunction Screenings: Earth Gravity Assist and Earth Return Analysis and Results

The NASA OSIRIS-REx asteroid sample return mission performed an Earth gravity assist on September 22, 2017, and returned to Earth to drop off the sample on September 24, 2023. In each case, the NASA Conjunction Assessment Risk Analysis (CARA) team screened the OSIRIS-REx trajectories against the satellite catalog in search of high-risk close approaches. This paper describes the preparation for collision avoidance and screening results, along with lessons learned, providing a baseline for support of future missions in this category, particularly as space traffic around the Earth and in cis-lunar space continues to rapidly expand.

Dolan Highsmith↗
NASA NTRS1976

Out of ecliptic missions using Venus or earth gravity assists

Multiple Venus or earth gravity-assist flybys are investigated as a means of producing trajectories that are inclined to the solar equator at low cost in total delta V. There are three phases to such trajectories: (1) production of a high flyby speed at the planet encounter, (2) attainment of one-to-one resonance by orbit pumping, and (3) deflection to high inclination by orbit cranking. Flybys are restricted to occur at the node of the planet orbit and the solar equator so as to take advantage of the natural inclination of the solar equator. For Venus flybys, the high approach speed is inherent in the earth to Venus trajectory. For earth flybys, the production of high approach speed can be accomplished by a VEGA (Venus-earth-gravity assist) trajectory or by a delta V-EGA trajectory. The general result is that moderate inclinations to the solar equator can be obtained at moderate total delta V cost, but at flight times which rise to five years for an inclination of 37 deg and to 13 years for an inclination of 54 deg.

Bender, D. F.↗
NASA NTRS2021

Effect of V-infinity Leveraging with Lunar-earth Gravity Assist on Interplanetary Trajectories

This work evaluates the effects of Lunar-Earth Gravity Assist on mission design and DV budget for interplanetary trajectories using Earth flybys and V1 Leveraging Maneuvers. The use of the Moon flyby, in combination to the Earth flyby, provides additional deviation of the hyperbolic excess velocity with respect to the Earth, also modifying its magnitude, and hence increases the overall flyby performance. The Lunar-Earth Gravity Assist has been evaluated for Exterior and Interior Leveraging, as well as for Short and Long transfers. A sample Jupiter mission is showcased, and the results suggest that the Moon effect during the flyby can reduce the total DVtot by 6.4% and the leveraging DVVILM by 21.06%.

Campagnola, Stefano↗
NASA NTRS2022

Flow Visualization, Heat Transfer, and Critical Heat Flux of Flow Boiling in Earth Gravity with Saturated Liquid-Vapor Mixture Inlet Conditions – In Preparation for Experiments Onboard the International Space Station

This study investigates flow boiling of n-Perfluorohexane with saturated two-phase mixture inlet in a rectangular channel of dimensions 114.6-mm heated length, 2.5-mm width, and 5 mm-height. The experiments were performed as part of the Mission Sequence Testing of the Flow Boiling and Condensation Experiment’s (FBCE) Flow Boiling Module (FBM) in the vertical upflow configuration in Earth gravity using the same experimental system that was launched to the International Space Station (ISS) in August 2021. The operating parameters varied are heating configuration (single- and double-sided), mass velocity (380 – 2400 kg/m2s), inlet quality (0.011 – 0.519), and inlet pressure (120 – 179 kPa). High-speed video photographs are presented to explain the two-phase flow patterns within the channel’s heated length. Flow patterns are constituted by low-density and high-density fronts moving along the channel, with the high-density fronts gradually reducing in length due to evaporation. Heat transfer results in terms of flow boiling curves, streamwise wall temperature profiles, streamwise heat transfer coefficient profiles, and average heat transfer coefficients are presented and trends discussed. CHF data from the present experiments are combined with prior databases to compile a consolidated FBCE-CHF database for saturated inlet to expand the ranges of operating conditions and include other flow orientations in Earth gravity. Experimental CHF trends are also discussed. The interfacial lift-off model shows a good CHF predictive accuracy evidenced by a mean absolute error of 11.97% for this consolidated database after constraining it to mass velocities greater than or equal to 500 kg/m2s. Finally, this study confirmed reliability of the upcoming ISS experiments for saturated inlet conditions and the collected Earth-gravity data will be compared to ISS microgravity data.

Flow boiling↗
NASA NTRS2022

Experimental Heat Transfer Results and Flow Visualization of Vertical Upflow Boiling in Earth Gravity with Subcooled Inlet Conditions – In Preparation for Experiments Onboard the International Space Station

Since 2012, researchers at the Purdue University Boiling and Two-Phase Flow Laboratory (PU-BTPFL) and NASA Glenn Research Center have been collaborating on a long-term effort to study flow boiling and condensation in microgravity. The ultimate goal has been to develop the Flow Boiling and Condensation Experiment (FBCE) for the International Space Station (ISS). Based on the findings from prior flow boiling experiments both at different orientations in Earth gravity and onboard parabolic flights simulating short durations of microgravity, a final refined experiment design, construction, and operating procedure have been arrived at for long-duration microgravity flow boiling experiments onboard the ISS. This study investigates flow boiling of n-Perfluorohexane with subcooled inlet in a rectangular channel of dimensions 114.6 mm heated length, 2.5 mm width, and 5 mm height. These pre-launch experiments (Mission Sequence Testing) were conducted in vertical upflow orientation in Earth gravity using the same experimental rig that was launched to the ISS in August 2021. The various operating parameters varied are heating configuration (single- and double-sided), mass velocity (180 – 3200 kg/m2s), inlet subcooling (+0 – 32°C, encompassing both highly subcooled and near-saturated inlet conditions), and inlet pressure (119 – 191 kPa). High-speed video flow visualization images are presented to explain the two-phase interfacial physics within the channel’s heated section. Heat transfer results in terms of flow boiling curves, streamwise profiles of wall temperature and heat transfer coefficient, and averaged heat transfer coefficients are analyzed and parametric effects elucidated. Severe temporal thermodynamic equilibrium is observed for near-saturated inlet at very low velocities. Nucleate boiling degradation starts at larger heat fluxes for single-sided heating than double sided at low mass velocities with highly subcooled inlet, and conversely at high mass velocities with near-saturated inlet. Nucleate boiling degradation can be delayed to higher heat fluxes by highly subcooling the inlet and increasing mass velocity. The entire local heat transfer coefficient profiles are degraded at higher heat fluxes for near-saturated inlet, but only the downstream part for highly subcooled inlet. This study also confirmed reliability of the upcoming ISS experimental data for subcooled inlet conditions and the collected Earth-gravity data will be used for comparison against the ISS data.

flow boiling↗
NASA NTRS2001

Scalar Measurements and Analysis of Helium Jets in Earth Gravity and Microgravity using Rainbow Schlieren Deflectometry

Recent experiments have shown that low-density gas jets injected into a high-density gas undergo an instability mode leading to highly periodic oscillations in the flow field. The transition from laminar to turbulent flow in these jets is abrupt, without a gradual change in scales. Although this type of instability at high Richardson numbers has been attributed to buoyancy, direct physical evidence was not acquired through experiments. In this study, several experiments were conducted in Earth gravity and microgravity to acquire qualitative data on near field flow structure of helium jets injected into air. Microgravity conditions were simulated in the 2.2-second drop tower at NASA Glenn Research Center. The operating parameters of this study included the tube inside diameter, the jet Reynolds number, and the jet Richardson number. Tubes with inside diameters of 19.05 mm and 31.75 mm were used in the experiments conducted in the drop tower. The jet flow was analyzed using quantitative rainbow schlieren deflectometry, a non-intrusive line of sight measurement technique for the whole field. The flow structure was characterized by distributions of angular deflection and the resulting helium mole fraction obtained from color schlieren images taken at 60 Hz. Three sets of experimental data with respect to three schlieren fields of view were acquired for each tube. Results show that the jet in microgravity was up to 70 percent wider than that in Earth gravity. The global jet flow oscillations observed in Earth gravity were absent in microgravity, providing direct experimental evidence that the flow instability in the low-density jet was buoyancy-induced. This study provides quantitative details of temporal flow evolution as the experiments undergo change in gravity in the drop tower.

Yep, Tze Wing↗
NASA NTRS1976

Solar electric propulsion combined with earth gravity assist - A new potential for planetary exploration

The need to shorten mission time (travel time to target planet) in missions to the outer planets prompts a search for alternatives to one-way minimum-energy transfers while continuing to minimize on-power thrusts. Gravity assists via swing-bys of inner planets are examined, with emphasis on a projected Venus-earth gravity assist (VEGA) and a combined solar electric propulsion and earth gravity assist (SEEGA). Gravity assists are also examined as essential for missions with sample returns back to earth. Possible use of such techniques in the Shuttle Interim Upper Stage (IUS) program is considered. Various SEEGA and VEGA trajectories are discussed and charted, and time lost in the launch orbit to earth re-encounter time is weighed against time gained by faster speed toward the mission destination.

Atkins, K. L.↗
NASA NTRS1975

Multi-asteroid flyby trajectories using Venus-earth gravity assists

The feasibility of using Venus and earth gravity assists for delivering spacecraft to the asteroid belt with a low launch energy but with the additional flight time from earth to Venus and back to earth. A numerical investigation for this kind of trajectory reveals a wide range of possibilities. Energy gain tables and synodic and resonance interval tables are presented for the gravity-assist trajectories. Tables are presented for the first twenty asteroids on the trajectories. These gravity-assist flybys are compared to direct launch multi-asteroid flybys, illustrating the advantage of the gravity-assist type in launch energy requirements.

Bender, D. F.↗
NASA NTRSDate not supplied

Flow Boiling & Condensation Experiment (FBCE): Flow Boiling in Earth Gravity and Onboard the International Space Station

Two phase thermal management systems that capitalize on both latent and sensible heats of the working fluid can yield orders of magnitude enhancements in flow boiling and condensation heat transfer coefficients and reduce size and weight of future space systems. Because the understanding of microgravity influences on two-phase flow and heat transfer is quite limited, there is presently an urgent need for a new experimental microgravity facility to enable investigators to perform long-duration flow boiling and condensation experiments in pursuit of reliable databases. This presentation will discuss results from the Flow Boiling and Condensation Experiment (FBCE), a collaborative effort between Purdue University and NASA Glenn Research Center. Experiments have been performed using the final system with the Flow Boiling Module (FBM) in vertical orientation in Earth gravity (Mission Sequence Tests, MST) and in microgravity onboard the International Space Station (ISS). High-speed-video flow visualization, heat transfer, and critical heat flux (CHF) results from the MST are presented for both subcooled liquid and saturated liquid-vapor inlet conditions. CHF predictions made using the Interfacial Lift-off Model are compared with a consolidated database made by compiling FBM datasets obtained in prior years for different orientations in Earth gravity and on parabolic flights. New explicit correlations for CHF and subcooled flow boiling heat transfer coefficient are developed and shown to be excellent in their predictive accuracies against consolidated experimental databases. Computations are performed for flows in microgravity and horizontal flows in Earth gravity, the results of which show a good predictive accuracy for both void fraction and wall temperature. Finally, similar preliminary results from the recent ISS experiments are presented.

Issam Mudawar↗
NASA NTRS2003

Scaling of Two-Phase Flows to Partial-Earth Gravity

A report presents a method of scaling, to partial-Earth gravity, of parameters that describe pressure drops and other characteristics of two-phase (liquid/ vapor) flows. The development of the method was prompted by the need for a means of designing two-phase flow systems to operate on the Moon and on Mars, using fluid-properties and flow data from terrestrial two-phase-flow experiments, thus eliminating the need for partial-gravity testing. The report presents an explicit procedure for designing an Earth-based test bed that can provide hydrodynamic similarity with two-phase fluids flowing in partial-gravity systems. The procedure does not require prior knowledge of the flow regime (i.e., the spatial orientation of the phases). The method also provides for determination of pressure drops in two-phase partial-gravity flows by use of a generalization of the classical Moody chart (previously applicable to single-phase flow only). The report presents experimental data from Mars- and Moon-activity experiments that appear to demonstrate the validity of this method.

Hurlbert, Kathryn M.↗
NASA NTRS1979

Solar electric earth gravity assist /SEEGA/ missions to the outer planets

The optimization of solar electric propulsion earth-gravity-assist trajectories to the outer planets is presented. Included in the optimization is both earth swingby velocity and swingby date. Mission modes with and without optimal post swingby thrust are compared. Performance suitable for preliminary mission studies is presented for the four major outer planets using circular-coplanar planetary orbits and additional performance is presented for a Saturn Orbiter-Dual Probe mission.

Sauer, C. G.↗
NASA NTRS1989

Thermal re-design of the Galileo spacecraft for a Venus-earth-earth-gravity assist (VEEGA) trajectory

The cancellation of the Centaur upper stage program in the aftermath of the Challenger tragedy forced a redesign of the flight trajectory of the Galileo spacecraft to Jupiter, i.e., from a direct trajectory to the Venus-earth-earth-gravity-assist (VEEGA) trajectory on the lower energy two-stage inertial upper stage (IUS), with the result that the spacecraft would be exposed to more than twofold increase in peak solar irradiance. This paper describes the general system-level thermal redesign effort for the Galileo spacecraft, from the start of feasibility studies to its final implementation. Results indicate that the addition of sunshades and the generous utilization of second-surface aluminized Kapton surface material for reflecting high percentages of incident solar irradiation would 'harden' the spacecraft's existing thermal protection system adequately, provided that sun-pointing at the relatively higher solar irradiance levels could be maintained. The final miximum flight temperature predictions for the spacecraft's subsystem thermal designs are given.

Reeve, R.↗