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Mission and systems parametric studies for Mars soft lander to define entry and landing capsule suitable for Mars probe in 1970 time period
Science objectives for a Mars exploration program in the 1990s, set forth by NASA's Committee on Planetary Exploration, are presented. They include: an intensive study of the Martian surface, the exploration of the structure and general circulation of the atmosphere, the exploration of the nature and dynamics of the planet's interior, the nature of Mars's magnetic field, the character of the upper atmosphere and its interaction with the solar wind, and the establishment of the global chemical and physical characteristics of the Martian surface. Several low cost missions, which have been suggested by the Committee for NASA's CORE program, such as the Mars Geoscience Climatology Observer, the Mars Aeronomy Orbiter, and the Mars Surface Network and Surface Probing missions are also covered. Direct Entry-Direct Return and Out-of-Orbit Entry-Orbital Rendezvous and Docking are two versions of a Mars Rover and Sample Return (MRSR) mission discussed in detail. It is concluded that a MRSR mission will require the combination of full Centaur capability, aerocapture at Mars and earth, and direct return to earth to meet major scientific goals. Further studies should be made in orbit assembly, fuel transfer technology, aeromaneuvering, terminal guidance, rover technology, and robotics.
Flight testing of thermal protection materials has been carried out over a two year period on the base heat shield of the Delta Clipper (DC-X and DC-XA), as well on a body flap. The purpose was to use the vehicle as a test bed for materials and more efficient repair or maintenance processes which would be potentially useful for application on new entry vehicles (i.e., X-33, RLV, planetary probes), as well as on the existing space shuttle orbiters. Panels containing Thermal Protection Systems (TPS) and/or structural materials were constructed either at NASA Ames Research Center or at McDonnell Douglas Aerospace (MDA) and attached between two of the four thrusters in the base heat shield of the DC-X or DC-XA. Three different panels were flown on DC-X flights 6, 7, and 8. A total of 7 panels were flown on DC-XA flights 1, 2, and 3. The panels constructed at Ames contained a variety of ceramic TPS including flexible blankets, tiles with high emissivity coatings, lightweight ceramic ablators and other ceramic composites. The MDS test panels consisted primarily of a variety of metallic composites. This report focuses on the ceramic TPS test results.
Samples of Interplanetary Dust Particles (IDPs) have now been collected from the stratosphere, from the Earth's ocean beds, and from the ice caps of Greenland and Antarctica. The most likely candidates for the sources of these particles are comets and asteroids. Comparison of the infrared spectra, elemental compositions, and mineralogy of the collected dust with atmospheric entry models and data obtained from cometary probes and telescopic observations has provided important constraints on the possible sources of the various types of collected dust. These constraints lead to the following conclusions. First, most of the deep sea, Greenland, and Antarctic spherules larger than 100 microns are derived from asteroids. Second, the stratospheric IDPs dominated by hydrated layer-lattice silicate minerals are also most likely derived from asteroids. Finally, the stratospheric IDPs dominated by the anhydrous minerals olivine and pyroxene are most likely from comets. The consequences of these parent body assignments are discussed.
The Mars Pathfinder Atmospheric Structure Investigation (ASI) obtained information on Martian atmospheric structure from three science accelerometers, which measured the deceleration of the probe at all levels in the atmosphere. Entry, descent, and landing occurred within 850 km of the Viking 1 landing site and somewhat later in northern summer. Pathfinder entered at 3 AME Local Mars Time (LMT), which provided the first opportunity to study Mars' nighttime atmospheric structure, and Viking 1 entered at 4:15 PME LMT. Magalhaes et al and Schofield et al have previously reported on the analysis of accelerometer measurements from the entry phase, which ended at about 8.5 km. The derived temperature profile extends from 140 km altitude down to 8.9 km, with a vertical resolution ranging from 250 meters to 50 meters, respectively. Here we report on a refined analysis of the Pathfinder entry phase ASIE data in which the effects of the small angular motions of the entry vehicle have been removed, thus enabling a search for small amplitude and small vertical wavelength structures. In addition, we will report on the atmospheric structure at altitudes below 8 km which is being derived from the accelerometer data acquired during the parachute descent phase. Additional information is contained in the original extended abstract.
The Huygens Probe descended through Titan s atmosphere on January 14, 2005. The Descent Imager/Spectral Radiometer (DISR) instrument made optical measurements which constrain the nature and vertical distribution and of the aerosols in the atmosphere.
The radiative heating environment for the Huygens probe near peak heating conditions for Titan entry is investigated in this paper. The task of calculating the radiation-coupled flowfield, accounting for non-Boltzmann and non-optically thin radiation, is simplified to a rapid yet accurate calculation. This is achieved by using the viscous-shock layer (VSL) technique for the stagnation-line flowfield calculation and a modified smeared rotational band (SRB) model for the radiation calculation. These two methods provide a computationally efficient alternative to a Navier-Stokes flowfield and line-by-line radiation calculation. The results of the VSL technique are shown to provide an excellent comparison with the Navier-Stokes results of previous studies. It is shown that a conventional SRB approach is inadequate for the partially optically-thick conditions present in the Huygens shock-layer around the peak heating trajectory points. A simple modification is proposed to the SRB model that improves its accuracy in these partially optically-thick conditions. This modified approach, labeled herein as SRBC, is compared throughout this study with a detailed line-by-line (LBL) calculation and is shown to compare within 5% in all cases. The SRBC method requires many orders-of-magnitude less computational time than the LBL method, which makes it ideal for coupling to the flowfield. The application of a collisional-radiative (CR) model for determining the population of the CN electronic states, which govern the radiation for Huygens entry, is discussed and applied. The non-local absorption term in the CR model is formulated in terms of an escape factor, which is then curve-fit with temperature. Although the curve-fit is an approximation, it is shown to compare well with the exact escape factor calculation, which requires a computationally intensive iteration procedure.
Blunt body probes are the primary design for atmospheric entry. The blunted capsule shape, while desirable for the decreased forebody heating, typically experiences dynamic instability at low supersonic and transonic flight. At moderate to low supersonic conditions, the unsteady wake begins to adversely interact with the vehicle in free-flight resulting in attitude oscillations which can grow in time and result in tumbling. Understanding vehicle dynamics is thus important when considering vehicle entry design and guidance navigation and control (GN&C) considerations. Historically, dynamic stability has been carried out exclusively using experimental techniques. The wide range of experimental approaches provide reasonable coverage in Mach and dynamic pressure space for a given trajectory, however achieving flight similitude is often difficult or impossible. Advancements in Computational Fluid Dynamics (CFD) techniques allow for dynamic motion of the vehicle surface during the simulation with either forced/prescribed motion or free motion in response to fluid forces. Several examples of CFD software with the ability to simulate fluid dynamics and vehicle motion are available in literature. The Free-Flight CFD (FF-CFD) capability developed by NASA Ames within the US3D flow solver has shown extensive validation and verification (V&V) efforts from moderate to low supersonic flow across a range of vehicle architectures. The solver is able to simulate full rotational and translation motion resulting in full 6 degrees-of-freedom (DoF) motion. The validation and verification efforts the solver's ability to predict the motion of a ballistic range model as compared to experimental results. Similar to other computational capabilities in literature, FF-CFD relied on heritage data reduction methodologies and processes for reducing dynamic data into aerodynamic coefficients intended for use in design and trajectory codes. These heritage approaches, initially developed with the assumptions (and restrictions) of ground test facilities, resulted in the significant culling of the full 6-DoF dynamic data set to discrete values which are then fit using an aerodynamic model. Recent development of simulation and data reduction methodologies has resulted in an improved approach to FF-CFD simulations of vehicle dynamics which leverage the control of dynamic constraints within a simulation set-up. The presentation of this work will cover the constrained dynamic simulation approach for deriving dynamic coefficients for a Genesis capsule. The methodology will be outlined and a discussion of implications in motion restriction will be discussed. Finally, reconstructed vehicle trajectories using FF-CFD derived aerodynamic coefficients will be presented.
Nephele [1] is a descent probe concept with a unique combination of entry (3D-CC+HEEET), sampling (flow-through passive impactors), and optics (laser-induced breakdown spectroscopy, or LIBS, and surface-enhanced Raman spectroscopy, or SERS), technologies with two key innovations (Figure 1). The first is the integration of the aerosol sampling inlet into the aeroshell body, allowing the possibility of sampling during passive descent without separation. The second is the use of the aerosol capture surface as an optical analysis substrate, allowing fast-cadence aerosol analysis via a dual optical spectrometer instead of mass spectrometry. Although this concept shares some features with other efforts such as Cupid’s Arrow [1] (single-body sample capture system), DAVINCI [2] and Venera-D [3] (use of an optical spectrometer), Nephele is unique in its physical integration of the sonde body, aerosol and gas sampler, and analysis instrumentation. This innovation is designed to eliminate the need for a controlled descent to achieve a detailed atmospheric aerosol transect, which offers in situ planetary science in a small spacecraft envelope. Aeroshell designs with inlets for free-falling sondes are well-understood, though not yet assessed for aerosol capture efficiency. A HEEET aeroshell with a specialized nose inlet material comprised of Carbon-Carbon is proposed for this mission concept.
Nephele is a descent probe concept with a unique combination of entry (3D-CC+HEEET), sampling (flow-through passive impactors), and optics (laser-induced breakdown spectroscopy, or LIBS, and surface-enhanced Raman spectroscopy, or SERS), technologies with two key innovations. The first is the integration of the aerosol sampling inlet into the aeroshell body, allowing the possibility of sampling during passive descent without separation. The second is the use of the aerosol capture surface as an optical analysis substrate, allowing fast-cadence aerosol analysis via a dual optical spectrometer instead of mass spectrometry. Although this concept shares some features with other efforts such as Cupid’s Arrow (single-body sample capture system), DAVINCI and Venera-D (use of an optical spectrometer), Nephele is unique in its physical integration of the sonde body, aerosol and gas sampler, and analysis instrumentation. This innovation is designed to eliminate the need for a controlled descent to achieve a detailed atmospheric aerosol transect, which offers in situ planetary science in a small spacecraft envelope. Aeroshell designs with inlets for free-falling sondes are well-understood, though not yet assessed for aerosol capture efficiency. A HEEET aeroshell with a specialized nose inlet material comprised of Carbon-Carbon is proposed for this mission concept.
Recent magnetometry data received from Galileo indicate that the most likely explanation for the magnetic signature there is indeed a global conducting layer below the surface. This conducting layer is well matched by a salty, mineral rich strata beneath the Europan ice crust or a salt water ocean. Galileo imaging results show a variety of terrain types thought to contain young material; for example, lineaments, chaotic terrain, and eruption features. Additionally, Galileo images have shown indications of areas of up-welling where subsurface material periodically gets pushed to the surface due to the forces of fracturing, butting, and refreezing of the ice sheet. While Europa Orbiter will provide close-flyby high resolution images, as well as magnetometry, spectroscopy and other remote sensing data of the surface, it will not be able to provide essential engineering data like surface hardness and surface ice structure needed to support eventual landed missions. Additionally, ice chemical composition at microscopic scales can only be studied in detail through in situ instrumentation. Seismoball is a small probe designed to be injected into a surface intersect orbit around Europa. Using small reverse thrusters, the probe will be capable of nulling the high horizontal injection velocity as it approaches the 2 km surface injection altitude, thus allowing it to fall to the surface at an impact velocity of < 100m/sec (much less than the DS-2 impact velocities). The external breakaway thruster structure and crushable exterior shell absorb the impact energy while allowing the science instrument suite to remain intact. JPL has already started analyzing the entry dynamics and designing/building a small, low mass probe which will withstand the impact g-forces and fit as a 'carry-on' on board the Europa Orbiter. The probe will carry a suite of 5-6 micro-instruments for imaging the surface (both microscopic and far-field), surface and shallow subsurface ice temperatures, surface hardness, crustal dynamics and periodicity, and compositional chemistry. If selected, this flight development activity will provide a unique science opportunity and adjunct to the primary Orbiter science mission. The final flight system will be designed to accommodate orbiter mass, volume, and power interface constraints, as well as entry dynamics, g-load mitigation, and arbitrary landing orientation.
A heatshield performance assessment is made for extraterrestrial entry into the atmosphere of the planet Jupiter. A rigorous determination of the potential ablation and thermostructural failure mechanisms for a candidate carbon-phenolic heatshield is made. The thermostructural integrity of the char layer is addressed in detail with the total response phenomenology involving char layer formation, stress under aerodynamic and thermodynamic loads, and points of stress concentration under the high radiative heat rates and severe temperature gradients encountered in the Jovian atmosphere. An alternate material concept in the carbon-carbon generic material class is examined to assess the viability of this material class for application to the Jupiter Probe Heatshield.
Aerodynamic characteristics of an aerocapture system intended to deliver a flagship-class orbiter and probe planetary science mission to Uranus are presented. The aeroshell of the Mars Science Laboratory and Mars 2020 entry vehicles is proposed as a baseline for this system to reduce the amount of necessary technology development. Direct Simulation Monte Carlo and Navier-Stokes computational fluid dynamics solutions are used to characterize the aerodynamic performance of the Mars-heritage vehicle for aerocapture flight at Uranus. These results are incorporated into an aerodatabase for use in six degree-of-freedom trajectory studies and mission design. Updates are made to the Mars-heritage aerodynamic uncertainty model based on observations in the Uranus-specific computational data to ensure the model is conservatively bounding for the proposed flight space. Necessary modifications to the aeroshell for system packaging are found to have minimal effect on aerodynamic performance. The resulting aerodatabase and uncertainty model are used to show the existing Mars-heritage entry vehicles have sufficient aerodynamic performance to achieve required control margin for Uranus aerocapture.
Aerodynamic characteristics of an aerocapture system intended to deliver a flagship-class orbiter and probe planetary science mission to Uranus are presented. The aeroshell of the Mars Science Laboratory and Mars 2020 entry vehicles is proposed as a baseline for this system to reduce the amount of necessary technology development. Direct Simulation Monte Carlo and Navier-Stokes computational fluid dynamics solutions are used to characterize the aerodynamic performance of the Mars-heritage vehicle for aerocapture flight at Uranus. These results are incorporated into an aerodatabase for use in six degree-of-freedom trajectory studies and mission design. Updates are made to the Mars-heritage aerodynamic uncertainty model based on observations in the Uranus-specific computational data to ensure the model is conservatively bounding for the proposed flight space. Necessary modifications to the aeroshell for system packaging are found to have minimal effect on aerodynamic performance. The resulting aerodatabase and uncertainty model are used to show the existing Mars-heritage entry vehicles have sufficient aerodynamic performance to achieve required control margin for Uranus aerocapture.
Introduction: The Decadal Strategy for Plane-tary Science and Astrobiology prioritized a Uranus Orbiter and Probe (UOP) as the highest-priority new Flagship mission for the 2023 – 2032 decade. Missions to the outer solar system require significant interplanetary cruise durations on the order of 12 – 15 years while carrying propellant to reduce velocity by several km/s to achieve a desired orbit. Parasitic mass and travel time can be traded where faster arrival velocities require more mass expensive capture burns. Recent advancements in Thermal Protection Systems (TPS) for planetary entry enable mass-efficient designs for atmospheric probes and missions that apply aerocapture for orbit insertion.
Entry systems used in unmanned planetary exploration are discussed in terms of future missions and more complex demands made upon the design configurations of orbiters and atmospheric space probes. The presently on-going Galileo project involving a Jupiter orbiter and a probe of the Jovian atmosphere is mentioned, and the difficult entry requirements at a velocity of 48 km/sec and an angle of minus seven to minus 10 degrees into an atmosphere composed largely of hydrogen, are described. Re-entry parameters determined by the respective entry environment, type of entry approach (hyperbolic or elliptical orbit) entry velocity, and guidance technology are given attention. Aerobraking, involving relatively slow circularization of an initial elliptical orbit by repeated passes through the atmosphere, is investigated. Aerocapture, by which vehicles using controlled flight paths through the atmosphere, can go directly from a hyperbolic flyby trajectory to low circular orbit is described. Major attractions of aerobraking and aerocapture are analyzed in terms of modest technology needs and relatively small impact on spacecraft design.
The Dragonfly mission will send a rotorcraft lander to the surface of Saturn’s moon Titan as part of the New-Frontiers program. This will be the first spacecraft to land on Titan since the Huygens probe’s descent in January of 2005 and only the second spacecraft to enter Titan’s atmosphere. The Dragonfly entry capsule is significantly larger than the Huygens probe and will experience higher aerothermal environments. This poster will provide an overview of the aerothermodynamic models used in the Dragonfly aeroshell design process. Titan provides a unique entry environment that has several fundamental differences from the environments at the more common entry destinations of Earth and Mars. The lack of atmospheric oxygen significantly reduces heatshield recession (expected to be negligible), which simplifies material response analysis but also reduces the efficiency of the thermal protection system. The atmos-phere is composed of mostly nitrogen and trace amounts of methane. During hypersonic entry this methane dissociates and leads to the formation of the molecule CN, which is known to radiate strongly in the shock layer. Current Dragonfly heating predictions estimate that radiation contributes about 50% of the total heat flux along the forebody and up to 90% on the aftbody, making radiation a key element of aerothermal analysis. To properly address the importance of radiation, a unique radiative-heating correlation was developed that incorporates normal-shock equilibrium chemistry predictions based on work from the Mars 2020 program. These new heating correlations agree well with Computational Fluid Dynamics (CFD) predictions and enable large-scale trajectory analyses by providing rapid heating predictions along candidate trajectories. Dragonfly aerothermal environments are generated with the Data Parallel Line Relaxation (DPLR) finite-volume Navier-Stokes solver alongside the Nonequilibrium Radiative Transport and Spectra (NEQAIR) radiation transport code. DPLR produces shock-aligned flowfields that incorporate the effects of both chemical and thermal nonequilibrium while NEQAIR solves the radiation transport equations along lines-of-sight through the flowfield solutions to predict the radiative heating on the aeroshell. Titan’s atmosphere produces complex thermal and chemical nonequilibria and so classical radiation approximations that extrapolate from a single line-of-sight, such as the Tangent-Slab method, were found to overpredict peak radiative heat fluxes by 10-20%. Therefore, all radiative heating is directly calculated using 3-D transport for both the forebody and aftbody to reduce unnecessary conservatism. A 21-species finite-rate chemistry model, including electrons and ionized species, is used in the CFD to ensure accurate vehicle heating predictions (the level of ionization is particularly for accurate radiative flux predictions). This poster will cover: 1) The models and assumptions used to simulate entry into Titan’s atmosphere, 2) Dragonfly aerothermal engineering correlations alongside statistical heating values, and 3) Driving aerothermal considerations for a Titan entry such as CN formation and radiation-flowfield coupling.
The NASA Ames Research Center (Thermal Protection Materials and Systems Branch) is investigating new ceramic materials for the thermal protection of atmospheric entry vehicles. An incremental approach to proving the capabilities of these materials calls for a lifting entry flight test of a sharp leading edge component on the proposed SHARP (Slender Hypervelocity Aerothermodynamic Research Probe) vehicle. This flight test will establish the aerothermal performance constraint under real lifting entry conditions. NASA Ames has been developing the SHARP test flight with SSDL (responsible for the SHARP S I vehicle avionics), Montana State University (responsible for the SHARP S I vehicle airframe), the Wickman Spacecraft and Propulsion Company (responsible for the sounding rocket and launch operations), and with the SCU Intelligent Robotics Program, The SCU team was added well after the rest of the development team had formed. The SCU role was to assist with the development of a real-time video broadcast system which would relay onboard flight video to a communication groundstation. The SCU team would also assist with general vehicle preparation as well as flight operations. At the time of the submission of the original SCU proposal, a test flight in Wyoming was originally targeted for September 2000. This date was moved several times into the Fall of 2000. It was then postponed until the Spring of 2001, and later pushed into late Summer 2001. To date, the flight has still not taken place. These project delays resulted in SCU requesting several no-cost extensions to the project. Based on the most recent conversations with the project technical lead, Paul Kolodjiez, the current plan is for the overall SHARP team to assemble what exists of the vehicle, to document the system, and to 'mothball' the vehicle in anticipation of future flight and funding opportunities.