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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.

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NASA NTRS2021

Triton: Fascinating Moon, Likely Ocean World, Compelling Destination!

Triton is an important signpost in understanding the diverse populations of both Ocean Worlds and Kuiper Belt Objects. As a likely ocean world, it is unique by virtue of its kidnapped history from the Kuiper Belt: its large orbital inclination makes it the only ocean world thought to be primarily heated by obliquity tides (Nimmo and Spencer, 2015). It is volatile-rich due to its formation in the outer Solar System and its unusual surface geology may be the product of cryovolcanism. Observations from New Horizons and Cassini motivate re-examination of Triton datasets and models, with value for comparative planetology of ocean worlds and KBOs, most notably with Europa, Enceladus, Titan, and Pluto. We re-explore old datasets with the new perspective of the importance of ocean worlds in our Solar System and the search for life.

J Castillo-Rogez↗
NASA NTRS2017

Resolution of Orbit Determination Prediction Instabilities at Titan During Cassini's Solstice Mission

The Cassini spacecraft has been in orbit about Saturn since 2004. Exploration of the Saturn system is driven by gravitational flybys of the moon Titan which alter the spacecraft trajectory. The Cassini Navigation Team receives regular updates to the Saturn satellites ephemeris from JPL's Solar System Dynamics group. The difference between subsequent ephemeris deliveries can be hundreds of meters in the position of Titan at the time of a flyby. Errors in Titan's position propagate downstream to the next flyby through the estimated spacecraft trajectory. Prior to 2013, the Cassini Orbit Determination Team estimated the Saturn satellite ephemeris parameters and used the a posteriori states and covariance of an operations arc as a priori inputs to subsequent estimation arcs. Since 2013, the OD Team has only been considering errors in the ephemeris and not estimating a correction to the satellite positions. The T119 Titan flyby exhibited a 3D miss distance of 2.44 km and the following T120 flyby yielded a smaller miss of 1.06 km at the 2.9s error level. These discrepancies between pre-flyby prediction and post-flyby trajectory reconstruction were due to errors in the Titan ephemeris. In order to improve the targeting of Titan in future flybys, the team restarted the satellite ephemeris estimation process for orbit determination solutions. Subsequent flybys had target misses of less than 1 km at the sub-3 error level. This paper describes the method of scaling the a priori satellite ephemeris covariance in the orbit determination process to allow larger corrections to the satellite system and improve the prediction of the spacecraft’s Titan-relative position at the time of encounters.

Boone, Dylan↗
NASA NTRS1992

Cassini: Mission to Saturn and Titan

The Cassini Mission to Saturn and Titan represents an important step into the exploration of the outerplanets. It will expand on the flyby encounters of Pioneer and Voyager and parallel the detailed exploration of the Jupiter system to be accomplished by the Galileo Mission. By continuing the study of the two giant planets and enabling detailed comparisons of their structure and behavior, Cassini will provide a tremendous insight into the formation and evolution of the solar system. In addition, by virtue of its focus on the Saturnian satellite Titan, Cassini will return detailed data on an environment whose atmospheric chemistry may resemble that of the primitive Earth. The scientific objectives can be divided into five categories: Titan, Saturn, rings, icy satellites, and magnetospheres. The key area of interest to exobiologists is Titan; the other four scientific categories will be discussed briefly to provide a comprehensive overview of the Cassini Mission.

Kerridge, Stuart J.↗
NASA NTRS1985

Volatiles on satellites of the outer solar system

Molecules of cosmochemically abundant elements can act as volatiles and hence play a dominant role in the climatic and surficial evolution of solid bodies. Examples on terrestrial planets are H2O on Earth and H2O and CO2 on Mars. Analogous processes in the outer solar system focussing on CH4, its associated hydrocarbons, and N2 on Titan and Triton, the large moons of Saturn and Neptune were explored. A kilometer-deep C2H6-CH4 ocean was proposed for the surface of Titan to reconcile data on the lower atmosphere with understanding of the photochemical conversion of methane to heavier hydrocarbons. If such ocean exists, then it has dissolved in it an amount of N2 equal to the present atmospheric abundance. Since N2 contributes with CH4 a substantial greenhouse effect, the atmospheric physical and chemical characteristics are strongly coupled to those of the ocean, which change with time as methane is photolyzed in the stratosphere. Some relationship exists to the runaway greenhouse model for primordial Venus and the possible climatic implications of the buffering of Earth's atmospheric CO2 by the oceans. Two important diagnostics, measurable in Titan's atmosphere, of the conditions under which icy satellites formed are the abundances of noble gases and the CHd/CH4 radio. Both of these indicators have been altered during the evolution of Titan's surface-atmosphere system, the former by interaction with the ocean and the latter by progressive photolysis of methane into heavier hydrocarbons. The physical state and composition of volatiles on the surface of Triton is controversial, but plausibly could include CH4 N2 and perhaps CO. If condensed CH4 and N2 are widespread, their transformation to and from the vapor phase dominates the surface energy balance with sunlight. The extreme seasonal modulation of subsolar latitude on Triton is thus primarily expressed by volatile transport rather than large teperature changes, with possibly drastic observational consequences. The presence of two volatile species differing greatly in their vapor pressures make Triton a crude analog of Mars. Triton might be more appropriately regarded as a deep-freeze version of Titan.

Lunine, J. I.↗
NASA NTRS1991

Titan aerosol and gas experiment for the Huygens Probe

The Cassini Mission is a joint undertaking of NASA and the European Space Agency (ESA) to explore the Saturnian System with a Saturn Orbiter and a Titan Probe. The launch vehicle and the Saturn Orbiter are the responsibility of NASA while the Huygens Probe (detachable Titan Probe) is the responsibility of ESA. The spacecraft will be launched in 1996 and the Huygens Probe will arrive at Titan in 2003. The Cassini Mission-Huygens Probe provides a unique opportunity to obtain detailed information about the atmosphere and, possibly, the surface of Titan. Titan possesses a substantial nitrogen atmosphere containing methane and many other organic compounds. Aerosols play an important role in the atmospheric processes on Titan. The Huygens Probe offers an opportunity to determine how organic particles are formed and grow which will clarify their role on Earth. A powerful analytical instrument, capable of addressing the above technology and other science questions, was recently proposed for the Huygens Probe. It is comprised of an aerosol and gas sampler and processor, and a gas chromatograph-ion mobility spectrometer. The instrument will be able to measure complex organics that make up the collected aerosols to the approximate 1 ppm level. Gases will be measured to approximately 10 ppb. Because the Titan atmosphere is expected to be quite complex, a gas chromatograph-ion mobility spectrometer is used to provide unequivocal identification of the components of the analytes. Further details of the science question to be investigated and the proposed instrument are described. The expected results and their implications are also addressed.

Carle, G. C.↗
NASA NTRS1992

Mass loading at Titan and comets

Present understanding of the cometary mass loading process (the addition of newborn ions to high speed magnetized plasma flows) is explored and the cometary lesson is applied to the environment of Titan. Mass loading is the dominant physical process controlling the interaction of the solar wind with comets, and it might play an important role in the interaction of Titan's neutral torus and exosphere with Saturn's magnetosphere. Freshly born ions follow cycloidal trajectories, resulting from the superposition of gyration and E/B drift. In the plasma frame, the resulting velocity space distribution is a ring beam distribution at comets and a ring distribution at Titan. This difference in free energy is expected to generate significantly different levels of low frequency broad band electromagnetic turbulence and, thus, result in important differences in the implanted ion distributions. It is predicted that mass loading creates a hot, equatorially trapped plasma population at Titan.

Gombosi, Tamas I.↗
NASA NTRS1986

The Cassini mission

An assessment study of a Saturn-Orbiter plus Titan-probe mission was made. The NASA Solar System Exploration Committee (SSEC) had recommended two separate missions to the Saturn system, in keeping with its charter to design low-cost, dedicated planetary missions. These were a Titan probe, to be carried by a small spacecraft that would include some type of radar mapping device, and a Saturn Orbiter that would be a more sophisticated spacecraft, to be launched separately. A Saturn orbiter and a Titan probe are combined in a single mission that would be carried out in collaboration with NASA. It is this proposal, called the Cassini Project, which was approved by NASA and ESA for an assessment study to be carried out over the next year and a half. Details of the Cassini mission are discussed.

Owen, Tobias↗
NASA NTRS2021

Convex Optimization Guidance for Precision Landing on Titan

Precision landing is an anticipated technology for future interplanetary missions. Autonomous spacecraft Entry, Descent and Landing (EDL) on the surface of a planetary body with a degree of precision in the order of meters is highly challenging. In this paper, a successive convexification guidance algorithm is utilized to simulate autonomous precision landing sequences on Saturn’s moon Titan. Due to its unique geophysical features, studying the science of matter within Titan’s atmosphere and beneath its surface is one of NASA’s most important planetary science objectives. As part of the Space Exploration Technology Directorate, a parafoil is proposed for landing on Titan due to its cost effectiveness, ease of deployment, low mass compared to the prospective payload and capabilities of precise autonomous delivery. This paper focuses on path optimization and guidance law development for high-fidelity dynamics parafoil tuning in the dense and adverse wind atmosphere of Titan, defined as a nonlinear and nonconvex optimal control problem. The powerful successive convexification method is used to solve the problem accordingly. The algorithm is designed such that the converged solution adheres to the nonlinear dynamics and kinematics in accordance with the original formulation, while respecting the state and control constraints. The six-degree-of-freedom (6DoF) simulations results show that this robust method is suitable for autonomous interplanetary applications.

Mooij, Edwin↗
NASA NTRS1977

Using the Shuttle for future advanced planetary missions

Advantages of using the STS for advanced planetary missions are considered. Several factors are analyzed with relation to a proposed exploration of the Jupiter System. Information relating to a Martian expedition for retrieving surface samples and also calculations pertaining to a landing on Titan are presented. The components of the suggested Jupiter System exploration facility include an orbiter, subsatellite, deep probes, Callisto lander, Io lander, and rough landers. Data concerning the STS injection mass possibilities and Ganymede orbiter mass potential are provided.

Friedman, L. D.↗
NASA NTRS2009

Broad Search Solar Electric Propulsion Trajectories to Saturn with Gravity Assists

Solar electric propulsion (SEP) trajectories to Saturn using multiple gravity assists are explored for the joint NASA and ESA Titan Saturn System Mission study. Results show that these new trajectories enable greater performance compared to chemical propulsion with similar gravity assists or SEP without gravity assists. This paper describes the method used in finding these interplanetary trajectories and examines variations in the performance for different SEP systems, flight times, and flyby sequences. The benefits of the SEP trajectories for a mission to Saturn are also discussed.

Titan↗
NASA NTRS1993

Summary of Cassini Acoustic Criteria Development Using Titan IV Flight Data

The Cassini spacecraft is being developed by the Jet Propulsion Laboratory (JPL) for theNational Aeronautics and Space Administration (NASA) to orbit and explore the planet Saturn, itsrings and satellites. Cassini will be launched on a Titan IV and boosted out of earth orbit by aCentaur. This paper discusses the development of Cassini acoustic criteria using Titan IV flight data. The Titan IV flight acoustic measurements and the different flight data processing techniquesemployed by Martin Marietta and The Aerospace Corporation are described in Reference 1, as wellasthe methods employed by JPL for identifying and correcting for instrumentation system transients.

Davis, G. L.↗
NASA NTRS2007

Electronics for Low Temperature Space Exploration Missions

Exploration missions to outer planets and deep space require spacecraft, probes, and on-board data and communication systems to operate reliably and efficiently under severe harsh conditions. On-board electronics, in particular those in direct exposures to the space environment without any shielding or protection, will encounter extreme low temperature and thermal cycling in their service cycle in most of NASA s upcoming exploration missions. For example, Venus atmosphere, Jupiter atmosphere, Moon surface, Pluto orbiter, Mars, comets, Titan, Europa, and James Webb Space Telescope all involve low-temperature surroundings. Therefore, electronics for space exploration missions need to be designed for operation under such environmental conditions. There are ongoing efforts at the NASA Glenn Research Center (GRC) to establish a database on the operation and reliability of electronic devices and circuits under extreme temperature operation for space applications. This work is being performed under the Extreme Temperature Electronics Program with collaboration and support of the NASA Electronic Parts and Packaging (NEPP) Program. The results of these investigations will be used to establish safe operating areas and to identify degradation and failure modes, and the information will be disseminated to mission planners and system designers for use as tools for proper part selection and in risk mitigation. An overview of this program along with experimental data will be presented.

Patterson, Richard L.↗
NASA NTRSDate not supplied

OceanWATERS Lander Robotic Arm Operation

Ocean Worlds Autonomy Testbed for Exploration Research and Simulation (OceanWATERS) is an open-source simulator for developing onboard autonomy software for robotic exploration of ocean worlds, such as Europa, Enceladus, and Titan, built on the Robot Operating System (ROS) and Gazebo simulation environment. Inevitable ground communication delays increase demand for a high degree of autonomy during excavation, collection and transfer of samples to scientific instruments for in-situ analysis. This paper offers a detailed discussion of the robotic arm design and operation for such autonomous surface exploration, taking as reference the Europa Lander mission. The lander arm, which is designed primarily to acquire icy surface and subsurface samples within the arm’s workspace, is a 6-degree-of-freedom manipulator with two end effectors: a sample excavation tool and a trenching end-effector. The robotic arm’s modes and operations can be summarized as follows: stowed arm, intended as the lander arm default configuration characterized by zero-power consumption; un-stowed arm, target arm configuration after its first deployment; selection and deployment of the end-effector to use next; guarded move, to detect ground level at the desired trenching location; drill ice using the grinder; dig trench at a particular location using the scoop; deliver sample to the sample transfer dock; discard redundant samples. The motion planning tool used for the lander arm is MoveIt, a ROS package. MoveIt uses sampling-based planning and collision checking libraries to determine safe paths. The Rapidly Exploring Random Trees* (RRT*) has been chosen as default planning algorithm as it provides optimal plans with an exponential speed and is guaranteed to find a solution, if feasible solutions exist. Furthermore, this work quantifies and discusses the energy requirements for excavating and collecting samples. In OceanWATERS, force feedback from the terrain, which influences the arm dynamics, is modelled using a discrete element method (DEM) simulation. The DEM and Gazebo software run in parallel and communicate through a co-simulation plugin. This paper presents an analysis and comparison of three DEM open source software (YADE, ESyS-Particle, Project Chrono) for implementation in OceanWATERS and motivates the choice of YADE as most suitable candidate.

Damiana Catanoso↗
NASA NTRS2005

Thermal Protection of the Huygens Probe During Titan Entry: Last Questions

CASSINI-HUYGENS mission is a cooperation between NASA and ESA, dedicated to the exploration of the Saturnian system. In the framework of this mission, the entry of the HUYGENS probe in the atmosphere of TITAN will be of major scientific interest. One of the essential points of the HUYGENS mission is therefore the good behavior of the thermal shield designed to maintain the aerodynamic shape and to protect the probe from excessive heating during the atmospheric entry on TITAN. The design and the qualification of this thermal shield were carried out between 1992 and 1995 (development phase). Currently, the final definition of mission parameters is being completed. As the performance of the thermal shield is one of all the parameters considered at system level, it is therefore necessary to reassess the thermal response of the TPS, taking into account some updated information that was not yet available during the development phase. After some recall of the results of 1992 to 1995, the paper will present a status of the current work on TPS.

Bouilly, Jean-Marc↗
NASA NTRS2008

Europa Explorer Operational Scenarios Development

In 2007, NASA conducted four advanced mission concept studies for outer planets targets: Europa, Ganymede, Titan and Enceladus. The studies were conducted in close cooperation with the planetary science community. Of the four, the Europa Explorer Concept Study focused on refining mission options, science trades and implementation details for a potential flagship mission to Europa in the 2015 timeframe. A science definition team (SDT) was appointed by NASA to guide the study. A JPL-led engineering team worked closely with the science team to address 3 major focus areas: 1) credible cost estimates, 2) rationale and logical discussion of radiation risk and mitigation approaches, and 3) better definition and exploration of science operational scenario trade space. This paper will address the methods and results of the collaborative process used to develop Europa Explorer operations scenarios. Working in concert with the SDT, and in parallel with the SDT's development of a science value matrix, key mission capabilities and constraints were challenged by the science and engineering members of the team. Science goals were advanced and options were considered for observation scenarios. Data collection and return strategies were tested via simulation, and mission performance was estimated and balanced with flight and ground system resources and science priorities. The key to this successful collaboration was a concurrent development environment in which all stakeholders could rapidly assess the feasibility of strategies for their success in the full system context. Issues of science and instrument compatibility, system constraints, and mission opportunities were treated analytically and objectively leading to complementary strategies for observation and data return. Current plans are that this approach, as part of the system engineering process, will continue as the Europa Explorer Concept Study moves toward becoming a development project.

Lock, Robert E.↗
DOE OSTI2022

Typical Neutron Emission Spectra for Multi-Mission Radioisotope Thermoelectric Generator Fuel

The Dragonfly rotorcraft currently being designed by the Johns Hopkins Applied Physics Laboratory (APL) is a mission destined to explore, via autonomous flight, the Saturnian moon of Titan and currently scheduled to launch in 2027. This largest moon of Saturn contains a thick, dense atmosphere, that when coupled with the remote distance to the Sun, requires the use of a radioisotope power system (RPS). The multi-mission radioisotope thermoelectric generator (MMRTG) fueled at Idaho National Laboratory is currently the only flight-certified RPS still in production within the Department of Energy complex, thus, an MMRTG was chosen for the Dragonfly mission.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS1988

Space station heavy lift launch vehicle utilization

The use of Heavy Lift Launch Vehicles (HLLVs) for Space Station assembly, logistics. and resupply is explored. Potential HLLVs, including those based on the Titan, and Shuttle-derived vehicles (SDV), are discussed. The baseline Critical Evaluation Task Force (CETF) Space Station assembly sequence is described and compared with assembly options made possible through the use of HLLVs. The issues of cost, dual compatibility with the Space Shuttle Space Transportation System (STS), co-manifesting of payloads with other science missions cargo return, and ground handling and launch facilities are also considered. The main advantage achieved by using HLLVs are simplification of assembly procedures, added resupply capability, and increased assured access to space. The major disadvantages are increased orbital flight operations complexity, higher logistics costs, and additional ground handling/launch facility requirements. Also, there will not be any improvement in return cargo capacity, nor any addition to crew transport capabilities. Finally, the dual STS/HLLV compatibility should be maintained to minimize program risk. HLLV and Orbital Maneuvering Vehicle design must parallel that of the Space Station.

Deryder, L. J.↗
NASA NTRS2005

2nd International Planetary Probe Workshop

Included are presentations from the 2nd International Planetary Probe Workshop. The purpose of the second workshop was to continue to unite the community of planetary scientists, spacecraft engineers and mission designers and planners; whose expertise, experience and interests are in the areas of entry probe trajectory and attitude determination, and the aerodynamics/aerothermodynamics of planetary entry vehicles. Mars lander missions and the first probe mission to Titan made 2004 an exciting year for planetary exploration. The Workshop addressed entry probe science, engineering challenges, mission design and instruments, along with the challenges of reconstruction of the entry, descent and landing or the aerocapture phases. Topics addressed included methods, technologies, and algorithms currently employed; techniques and results from the rich history of entry probe science such as PAET, Venera/Vega, Pioneer Venus, Viking, Galileo, Mars Pathfinder and Mars MER; upcoming missions such as the imminent entry of Huygens and future Mars entry probes; and new and novel instrumentation and methodologies.

Venkatapathy, Ethiraj↗