Ames Research Center

About: Ames Research Center is a facility organization based out in Mountain View, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Planet. The organization has 13766 authors who have published 35830 publications receiving 1350076 citations. The organization is also known as: ARC & NASA Ames.

A new study of the chemical structure of the Horsehead nebula: the influence of grain-surface chemistry

Abstract: A wide variety of molecules have recently been detected in the Horsehead nebula photodissociation region (PDR) suggesting that: (i) gas-phase and grain chemistries should both contribute to the formation of organic molecules; and (ii) far-ultraviolet (FUV) photodesorption may explain the release into the gas phase of grain surface species. In order to tackle these specific problems and more generally in order to better constrain the chemical structure of these types of environments we present a study of the Horsehead nebula gas-grain chemistry. To do so we used the 1D astrochemical gas-grain code Nautilus with an appropriate physical structure computed with the Meudon PDR code and compared our modeled outcomes with published observations and with previously modeled results when available. The use of a large set of chemical reactions coupled with the time-dependent code Nautilus allows us to reproduce most of the observations well, including those of the first detections in a PDR of the organic molecules HCOOH, CH2 CO, CH3 CHO and CH3 CCH, which are mostly associated with hot cores. We also provide some abundance predictions for other molecules of interest. Understanding the chemistry behind the detection of these organic molecules is crucial to better constrain the environments these molecules can probe.

Mars 2020 Entry, Descent and Landing Instrumentation (MEDLI2)

Abstract: This paper will introduce Mars Entry Descent and Landing Instrumentation (MEDLI2) on NASA's Mars2020 mission. Mars2020 is a flagship NASA mission with science and technology objectives to help answer questions about possibility of life on Mars as well as to demonstrate technologies for future human expedition. Mars2020 is scheduled for launch in 2020. MEDLI2 is a suite of instruments embedded in the heatshield and backshell thermal protection systems of Mars2020 entry vehicle. The objectives of MEDLI2 are to gather critical aerodynamics, aerothermodynamics and TPS performance data during EDL phase of the mission. MEDLI2 builds up the success of MEDLI flight instrumentation on Mars Science Laboratory mission in 2012. MEDLI instrumentation suite measured surface pressure and TPS temperature on the heatshield during MSL entry into Mars. MEDLI data has since been used for unprecedented reconstruction of aerodynamic drag, vehicle attitude, in-situ atmospheric density, aerothermal heating, transition to turbulence, in-depth TPS performance and TPS ablation. [1,2] In addition to validating predictive models, MEDLI data has highlighted extra margin available in the MSL forebody TPS, which can potentially be used to reduce vehicle parasitic mass. MEDLI2 expands the scope of instrumentation by focusing on quantities of interest not addressed in MEDLI suite. The type the sensors are expanded and their layout on the TPS modified to meet these new objectives. The paper will provide key motivation and governing requirements that drive the choice and the implementation of the new sensor suite. The implementation considerations of sensor selection, qualification, and demonstration of minimal risk to the host mission will be described. The additional challenges associated with mechanical accommodation, electrical impact, data storage and retrieval for MEDLI2 system, which extends sensors to backshell will also be described.

Model Reference Adaptive Fight Control Adapted for General Aviation: Controller Gain Simulation and Preliminary Flight Testing On a Bonanza Fly-By-Wire Testbed

Abstract: Model reference adaptive flight control (dynamic inverse with adaptation) methodology is adapted for use for a general aviation Hawker Beechcraft Bonanza fly-by-wire testbed. The control method is based on the work of Calise and the NASA Integrated Resilient Aircraft Control project. A derivation of the simplified inverse controller and adaptive elements is presented. The controller is a longitudinal flight controller that tracks pilot inputs of velocity and flight path angle. An L2 tracking error metric is used in a study to tune the outer controller loop gains by introducing artificial time delays in the control signals to determine the time delay margin. Results of this study are presented. Hardware in the loop control software ground testing followed by flight testing of this baseline controller have been completed. Flight test cards are presented in this paper as well as desktop simulation and flight test results.

Evaluation of the Terminal Sequencing and Spacing system for Performance-Based Navigation arrivals

Abstract: NASA has developed the Terminal Sequencing and Spacing (TSS) system, a suite of advanced arrival management technologies combining time-based scheduling and controller precision spacing tools. TSS is a ground-based controller automation tool that facilitates sequencing and merging arrivals that have both current standard ATC routes and terminal Performance-Based Navigation (PBN) routes, especially during highly congested demand periods. In collaboration with the FAA and MITRE's Center for Advanced Aviation System Development (CAASD), TSS system performance was evaluated in human-in-the-loop (HITL) simulations with currently active controllers as participants. Traffic scenarios had mixed Area Navigation (RNAV) and Required Navigation Performance (RNP) equipage, where the more advanced RNP-equipped aircraft had preferential treatment with a shorter approach option. Simulation results indicate the TSS system achieved benefits by enabling PBN, while maintaining high throughput rates-10% above baseline demand levels. Flight path predictability improved, where path deviation was reduced by 2 NM on average and variance in the downwind leg length was 75% less. Arrivals flew more fuel-efficient descents for longer, spending an average of 39 seconds less in step-down level altitude segments. Self-reported controller workload was reduced, with statistically significant differences at the p<;0.01 level. The RNP-equipped arrivals were also able to more frequently capitalize on the benefits of being “Best-Equipped, Best-Served” (BEBS), where less vectoring was needed and nearly all RNP approaches were conducted without interruption.