Phoenix Entry Research Articles

CFD Analysis of Mars Phoenix Capsules at Mach Number 10

Numerical simulations are performed for flow over Phoenix entry vehicle at Mars at zero angle of Attack and Mach number 10. Flow field features like bow shock, shear layers, expansion fan and separation bubble will be captured using CFD commercial package FLUENT. The computed wall data of pressure and temperature will be compared with experimental results at Mars atmospheric conditions. This project deals with the study of flow over Phoenix entry vehicle at Mach number 10. The concept of atmospheric entry has applications in various fields. Vehicles that typically undergo this process include exo-orbital trajectories. In this project, the type of entry vehicle considered is entry capsule, which enters Mars atmosphere from an orbit. The primary design consideration of entry capsule requires large spherical nose radius of their fore body that gives high aerodynamic drag and a short body length for reducing the total structural weight and the ballistic coefficient.

Mars EXPRESS observation of the PHOENIX entry: simulations, planning, results and lessons learned

NASA’s PHOENIX spacecraft has successfully landed on Mars on 25 May 2008. ESA supported the event by recording signals from PHOENIX by the Mars EXPRESS spacecraft using its lander communication subsystem. Following numerical simulations of the probe entry plume emission, two Mars EXPRESS instruments, namely the High Resolution and Stereo Camera (HRSC) and the Ultraviolet and Infrared Spectrometer (SPICAM), were switched on in to observe the emission associated with the atmospheric entry. No positive detection was reported unfortunately. This article reports on the simulations, the planning, and the results. The non-detection by the UV spectrometer was due to a wrong instrument setting. Result for the camera is tentatively explained by the level of emission in the visible range. Lessons learned are given in the conclusions: the entry probe trajectory should be communicated as soon as possible to all interested parties, within the boundary conditions of confidentiality obviously. It is important to plan some redundancy to prevent incorrect instrument operations. A multi-instrument multi-spacecraft campaign should be encouraged by all means. Since detection of such faint signal is challenging, the integration time must be properly matched to the event duration. Payload operational (exclusion) rules should be discussed in an open way, to check whether the prudence of such measures is procedural or physical. The numerical simulations discussed in this paper have been focused on IR radiation in the lower density flow wake, using a DSMC/line-by-line method. These could be complemented with other numerical approaches more focused in the VUV–visible region in the high-pressure bow-shock region, using continuum Navier–Stokes fluid methods, which would yield information on the contribution to the emission spectrum from minor flow species such as CN, C2 and C.

Overview of the Phoenix Entry, Descent, and Landing System Architecture

Overview of the Phoenix Entry, Descent, and Landing System Architecture

Aeroheating Predictions for Phoenix Entry Vehicle

[Abstract] Aerothermal analyses of the Phoenix entry vehicle in the Martian Atmosphere are presented. Two Navier-Stokes flow solvers are used to predict the environments experienced by the vehicle along several design trajectories. The majority of the solutions are computed as axisymmetric in order to yield higher, and therefore more conservative, heating rates. Several three-dimensional cases are also computed to assess the heating enhancement caused by surface singularities and the complex aftbody vortices. When the thermal protection system was assessed in a separate analysis in response to the computed aeroheating environments, the prebuilt design is found perform successfully.

Multibody Modeling and Simulation for Mars Phoenix Entry, Descent, and Landing

A multibody flight simulation for the Phoenix Mars Lander was developed that included high-fidelity six-degreeof-freedom rigid-body models for the parachute and lander system. The simulation predicted attitude and rate histories of all bodies throughout the flight. In so doing, a realistic behavior of the descending parachute/lander system dynamics was simulated that allowed assessment of the Phoenix descent performance and identification of sensitivities for landing. This simulation provided a complete end-to-end capability of modeling the entire entry, descent, and landing sequence for the mission. The simulation was used to predict the parachute and lander aerodynamic angles during entry and the response of the lander system to various wind models and windshears. Several different wind models were analyzed to determine which was most effective at exciting vehicle attitude dynamics. The simulation was used to drive a Monte Carlo analysis that provided a statistical evaluation of the performance capability of the Phoenix landing system.

Entry, Descent, and Landing Performance of the Mars Phoenix Lander

On May 25, 2008, the Mars Phoenix Lander successfully landed on the northern arctic plains of Mars. An overview of a preliminary reconstruction analysis performed on each en-try, descent, and landing phase to assess the performance of Phoenix as it descended is pre-sented and a comparison to pre-entry predictions is provided. The landing occurred 21 km further downrange than the predicted landing location. Analysis of the flight data revealed that the primary cause of Phoenix’s downrange landing was a higher trim total angle of at-tack during the hypersonic phase of the entry, which resulted in Phoenix flying a slightly lift-ing trajectory. The cause of this higher trim attitude is not known at this time. Parachute deployment was 6.4 s later than prediction. This later deployment time was within the varia-tions expected and is consistent with a lifting trajectory. The parachute deployment and in-flation process occurred as expected with no anomalies identified. The subsequent parachute descent and powered terminal landing also behaved as expected. A preliminary reconstruc-tion of the landing day atmospheric density profile was found to be lower than the best apri-ori prediction, ranging from a few percent less to a maximum of 8%. A comparison of the flight reconstructed trajectory parameters shows that the actual Phoenix entry, descent, and landing was close to pre-entry predictions. This reconstruction investigation is currently on-going and the results to date are in the process of being refined.

Mars Phoenix Entry, Descent, and Landing Simulation Design and Modeling Analysis

The 2007 Mars Phoenix Lander was launched in August of 2007 on a ten month cruise to reach the northern plains of Mars in May 2008. Its mission continues NASA s pursuit to find evidence of water on Mars. Phoenix carries upon it a slew of science instruments to study soil and ice samples from the northern region of the planet, an area previously undiscovered by robotic landers. In order for these science instruments to be useful, it was necessary for Phoenix to perform a safe entry, descent, and landing (EDL) onto the surface of Mars. The EDL design was defined through simulation and analysis of the various phases of the descent. An overview of the simulation and various models developed to characterize the EDL performance is provided. Monte Carlo statistical analysis was performed to assess the performance and robustness of the Phoenix EDL system and are presented in this paper. Using these simulation and modelling tools throughout the design and into the operations phase, the Mars Phoenix EDL was a success on May 25, 2008.

Mars Phoenix Entry, Descent, and Landing Trajestory and Atmosphere Reconstruction

Mars Phoenix Entry, Descent, and Landing Trajestory and Atmosphere Reconstruction

Analysis of Effectiveness of Phoenix Entry Reaction Control System

Interaction between the external flowfield and the reaction control system (RCS) thruster plumes of the Phoenix capsule during entry has been investigated. The analysis covered rarefied, transitional, hypersonic and supersonic flight regimes. Performance of pitch, yaw and roll control authority channels was evaluated, with specific emphasis on the yaw channel due to its low nominal yaw control authority. Because Phoenix had already been constructed and its RCS could not be modified before flight, an assessment of RCS efficacy along the trajectory was needed to determine possible issues and to make necessary software changes. Effectiveness of the system at various regimes was evaluated using a hybrid DSMC-CFD technique, based on DSMC Analysis Code (DAC) code and General Aerodynamic Simulation Program (GASP), the LAURA (Langley Aerothermal Upwind Relaxation Algorithm) code, and the FUN3D (Fully Unstructured 3D) code. Results of the analysis at hypersonic and supersonic conditions suggest a significant aero-RCS interference which reduced the efficacy of the thrusters and could likely produce control reversal. Very little aero-RCS interference was predicted in rarefied and transitional regimes. A recommendation was made to the project to widen controller system deadbands to minimize (if not eliminate) the use of RCS thrusters through hypersonic and supersonic flight regimes, where their performance would be uncertain.

Expected atmospheric environment for the Phoenix landing season and location

The Phoenix mission, launched on 4 August 2007, landed in the far northern plains of Mars on 25 May 2008. In order to prepare for the landing events and the 90‐sol mission, a significant amount of work has gone into characterizing the atmospheric environment at this location on Mars for northern late spring through midsummer. In this paper we describe the motivation for the work and present our results on atmospheric densities and winds expected during the Phoenix entry, descent, and landing, as well as near‐surface pressure, temperature, winds, surface temperature, and visible optical depth expected over the course of the science mission.

Validation of Mars Global Reference Atmospheric Model (Mars-GRAM 2001) and planned new features

For altitudes below 80 km, Mars Global Reference Atmospheric Model (Mars-GRAM 2001) is based on output climatology from NASA Ames Mars General Circulation Model (MGCM). At COSPAR 2002, results were presented of validation tests of Mars-GRAM versus data from Mars Global Surveyor Thermal Emission Spectrometer (TES) and Radio Science (RS) experiment. Further validation tests are presented comparing Mars-GRAM densities with those from the European Mars Climate Database (MCD), and comparing densities from both Mars-GRAM and MCD against TES observations. Throughout most of the height and latitude range of TES data (0–40 km and 70S to 70N), good agreement is found between atmospheric densities from Mars-GRAM and MCD. However, at the season and latitude zone for Mars Phoenix arrival and landing ( L s = 65°–80° and latitude 65N to 75N), Mars-GRAM densities are about 30%–45% higher than MCD densities near 40 km altitude. Further evaluation is warranted concerning potential impact of these model differences on planning for Phoenix entry and descent. Three planned features for Mars-GRAM update are also discussed: (1) new MGCM and Thermospheric General Circulation Model data sets to be used as a revised basis for Mars-GRAM mean atmosphere, (2) a new feature to represent planetary-scale traveling waves for upper altitude density variations (such as found during Mars Odyssey aerobraking), and (3) a new model for effects of high resolution topographic slope on winds near the surface (0–4.5 km above Mars Orbiter Laser Altimeter topography level). Mars-GRAM slope winds will be computed from a diagnostic (algebraic) relationship based on Ye et al. [Ye, Z.J., Segal, M., Pielke, R.A., A comparative study of daytime thermally induced upslope flow on Mars and Earth, J. Atmos. Sci. 47(5), 612–628, 1990]. This approach differs from mesoscale models (such as Mars Regional Atmospheric Modeling System and Mars Mesoscale Model Version 5), which use prognostic, full-physics solutions of the time- and space-dependent differential equations of motion. As such, slope winds in Mars-GRAM will be consistent with its “engineering-level” approach, and will be extremely fast and easy to evaluate, compared with mesoscale model solutions. Mars-GRAM slope winds are not being suggested as a replacement for sophisticated, full-physics Mars mesoscale models, but may have value, particularly for preliminary screening of large numbers of candidate landing sites for future Mars missions, such as Phoenix and Mars Science Laboratory. Test output is presented from Mars-GRAM slope winds in the area of Gusev Crater and Valles Marineris.