Simulation of launch and re-entry acceleration profiles for testing of shuttle and unmanned microgravity research payloads

Microgravity experiments designed for execution in Get-Away Special canisters, Hitchhiker modules, and Reusable Re-entry Satellites will be subjected to launch and re-entry accelerations. Crew-dependent provisions for preventing acceleration damage to equipment or products will not be available for these payloads during flight; therefore, the effects of launch and re-entry accelerations on all aspects of such payloads must be evaluated prior to flight. A procedure was developed for conveniently simulating the launch and re-entry acceleration profiles of the Space Shuttle (3.3 and 1.7 × g maximum, respectively) and of two versions of NASA's proposed materials research Re-usable Re-entry Satellite (8 × g maximum in one case and 4 × g in the other). By using the 7 m centrifuge of the Gravitational Plant Physiology Laboratory in Philadelphia it was found possible to simulate the time dependence of these 5 different acceleration episodes for payload masses up to 59 kg. A commercial low-cost payload device, the “Materials Dispersion Apparatus” of Instrumentation Technology Associates was tested for (1) integrity of mechanical function, (2) retention of fluid in its compartments, and (3) integrity of products under simulated re-entry g-loads. In particular, the sharp rise from 1 g to maximum g-loading that occurs during re-entry in various unmanned vehicles was successfully simulated, conditions were established for reliable functioning of the MDA, and crystals of 5 proteins suspended in compartments filled with mother liquor were subjected to this acceleration load.     

GENERATION AND APPLICATION OF UNSTRUCTURED ADAPTIVE MESHES WITH MOVING BOUNDARIES

INTRODUCTIONMany engineering applications require thenumerical prediction of strongly unsteady flowsinteracting with moving bodies.A case in pointis that the detailed calculation of sphere motionsin an unsteady field induced by blast waves is akey issue to determine the drag force exerting up-on the sphere by the surrounding gas and,inturn,to reveal the mechanism of unsteady effectson the drag coefficient.To cope with such pro-blems,one should simulate unsteady flows withmoving boundary co…     

Planar Problem of an Optimal Transfer of a Low-Thrust Spacecraft from High-Elliptic to Geosynchronous Orbit

Low-thrust flights from high-elliptic orbits are of considerable interest, since they allow one to decrease (compared to high-thrust flights) the propulsion consumption and to reduce the flight duration. At the same time, in comparison with the spiral unwinding flights from low near-circular orbits, this scheme minimizes the harmful effect of the radiation belts. Based on the maximum principle, the problem of optimization is reduced to a two-point boundary value problem, which is solved numerically using the modified Newton method. A method is suggested to obtain the initial approximation for solving the boundary value problem. The method takes advantage of the idea of transition from an approximately optimal trajectory to the optimal one. Two problems, which have different low-thrust models, are considered: one with permanently acting low thrust and the other with the possibility of turning it on/off. In both cases no restrictions are imposed on the thrust direction. A comparison of these problems is made. We investigated (i) what gain in the final mass can be attained when passing from the first to the second problem, (ii) at the cost of what loss in flight duration this can be achieved, and (iii) what changes in the optimal program of control must be done in this case.     

Estimation of plasma density from wave data of cold electron plasma

Based on the dispersion relation of electron plasma, one can expect, that the waves excited in the frequency band (f_p, f_u=sqrt(f_p^*f_p+f_c^*f_c)) should persist in experimental spectra. For wave data from a spacecraft immersed in a cold plasma such an assumption may be misleading. In measurements performed on board the INTERCOSMOS-19, ACTIVE, APEX satellites and VC36.064CE rocket the most prominent spectral structure is centered around frequency f_r fulfilling the relation f_crp and corresponds to resonant detection of Bernstein waves excited in the surrounding plasma by spacecraft systems. Input network mismatch at frequencies around fu significantly depresses natural plasma noise as well as that excited by the spacecraft. Plasma emissions in the band (f_p, f_u) are prominent if the electromagnetic excitation is preferential (topside sounders) or if the excitation introduces nonequilibrium components into the plasma e.g. particle beams or clouds. Experimental examples are presented and parameters of cold plasma spectra useful for electron density estimation are discussed. The application to other spacecraft-cold plasma configurations is suggested.     

What is the threshold amount of starch necessary for full gravitropic sensitivity?

In preparation for microgravity experiments, we studied the kinetics of gravitropism in seedlings of wild-type (WT) Arabidopsis and three starch-deficient mutants. One of these mutants is starchless (ACG 21) while the other two are intermediate starch mutants (ACG 20 and ACG 27). In root cap cells, ACG 20 and 27 have 51% and 60% of the WT amount of starch, respectively. However, in endodermal cells of the hypocotyl, ACG 20 has a greater amount of starch than ACG 27. WT roots and hypocotyls were much more responsive to gravity than were the respective organs of the starchless mutant, and the intermediate starch mutants exhibited reduced gravitropism but had responses that were close to that of the WT. In roots, ACG 27 (more starch) was more responsive than ACG 20 (less starch), while in hypocotyls, ACG 20 (more starch) had a greater response than ACG 27 (less starch). Taken together, our data are consistent with the starch-statolith hypothesis for gravity perception in that the degree of graviresponsiveness is proportional to the total mass of plastids per cell. These results also suggest that (in roots) 51-60% starch is close to the threshold amount of starch needed for full gravitropism and that the gravity sensing system is "overbuilt."     

Interstellar Mapping and Acceleration Probe (IMAP): A New NASA Mission

The Interstellar Mapping and Acceleration Probe (IMAP) is a revolutionary mission that simultaneously investigates two of the most important overarching issues in Heliophysics today: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. While seemingly disparate, these are intimately coupled because particles accelerated in the inner heliosphere play critical roles in the outer heliospheric interaction. Selected by NASA in 2018, IMAP is planned to launch in 2024. The IMAP spacecraft is a simple sun-pointed spinner in orbit about the Sun-Earth L1 point. IMAP’s ten instruments provide a complete and synergistic set of observations to simultaneously dissect the particle injection and acceleration processes at 1 AU while remotely probing the global heliospheric interaction and its response to particle populations generated by these processes. In situ at 1 AU, IMAP provides detailed observations of solar wind electrons and ions; suprathermal, pickup, and energetic ions; and the interplanetary magnetic field. For the outer heliosphere interaction, IMAP provides advanced global observations of the remote plasma and energetic ions over a broad energy range via energetic neutral atom imaging, and precise observations of interstellar neutral atoms penetrating the heliosphere. Complementary observations of interstellar dust and the ultraviolet glow of interstellar neutrals further deepen the physical understanding from IMAP. IMAP also continuously broadcasts vital real-time space weather observations. Finally, IMAP engages the broader Heliophysics community through a variety of innovative opportunities. This paper summarizes the IMAP mission at the start of Phase A development.     

Reactant jetting in unstable detonation

We note the common existence of a supersonic jet structure locally embedded within a surrounding transonic flow field in the hitherto unrelated phenomena of unstable gaseous detonation and hypervelocity blunt body shock wave interaction. Extending prior results that demonstrate the consequences of reduced endothermic reaction rate for the supersonic jet fluid in the blunt body case, we provide an explanation for observations of locally reduced OH PLIF signal in images of the keystone reaction zone structure of weakly unstable detonations. Modeling these flow features as exothermically reacting jets with similarly reduced reaction rates, we demonstrate a mechanism for jetting of bulk pockets of unreacted fluid with potentially differing kinetic pathways into the region behind the primary detonation front of strongly unstable mixtures. We examine the impact of mono-atomic and diatomic diluents on transverse structure. The results yield insight into the mechanisms of transition and characteristic features of both weakly and strongly unstable mixtures.     

Theoretical prediction of thermal diffusion coefficients for ternary hydrocarbon mixtures based on the irreversible thermodynamics theory

An accurate thermodiffusion model is of paramount importance to the petroleum industry for the prediction of the compositional variation in hydrocarbon reservoirs. Several theoretical models have been developed. Kempers and Firoozabadi models are the latest two models, which are not only applicable for binary mixtures but also for multi-component mixtures. In this paper, we applied the Firoozabadi model to a ternary hydrocarbon mixture of n-Dodecane, n-Butane and Methane with different mass fraction. It reveals that the accuracy of the thermal diffusion coefficients for a specific mixture of interest relies on the accuracy of the thermodynamic properties from equations of state, corresponding Fick's diffusion coefficients, and the thermal diffusion modeling.     

Lunar Exploration Neutron Detector for the NASA Lunar Reconnaissance Orbiter

The design of the Lunar Exploration Neutron Detector (LEND) experiment is presented, which was optimized to address several of the primary measurement requirements of NASA’s Lunar Reconnaissance Orbiter (LRO): high spatial resolution hydrogen mapping of the Moon’s upper-most surface, identification of putative deposits of appreciable near-surface water ice in the Moon’s polar cold traps, and characterization of the human-relevant space radiation environment in lunar orbit. A comprehensive program of LEND instrument physical calibrations is discussed and the baseline scenario of LEND observations from the primary LRO lunar orbit is presented. LEND data products will be useful for determining the next stages of the emerging global lunar exploration program, and they will facilitate the study of the physics of hydrogen implantation and diffusion in the regolith, test the presence of water ice deposits in lunar cold polar traps, and investigate the role of neutrons within the radiation environment of the shallow lunar surface.