P54A-01
Development of Advanced Radioisotope Power Systems for NASA's Future Science Missions
This presentation will provide an overview of NASA's current efforts on development of advanced radioisotope power systems (RPS) for future science missions. The current efforts include development of flight qualified Multimission Radioisotope Thermoelectric Generator (MMRTG) and Stirling Radioisotope Generator (SRG) systems with nominal 100 watts power level and capability to operate in both deep space and planetary environments. In addition, advanced technology development efforts are being conducted to increase the specific power of both RTG and SRG systems to enable future science missions. The efforts also include new technologies that have the potential to provide significant increases in specific power of RPS system. A notional RPS technology development roadmap will be presented and various potential mission opportunities identified.
P54A-02
Use of an MMRTG for the 2009 Mars Science Laboratory Mission
NASA is considering the use of a nuclear power source for the 2009 Mars Science Laboratory (MSL) mission. The system under consideration is an MMRTG (Multi-Mission Radioisotope Thermoelectric Generator). The MSL mission would place a rover on Mars between latitudes +/- 60 degrees. The MMRTG is being considered for this mission because it can produce adequate power for mobility and for science investigations regardless of landing site latitude and season on Mars. MSL would be about three times as massive as the Mars Exploration Rovers now active on Mars; it would carry an extensive complement of science instruments, including a coring drill. The MMRTG is one of two new radioisotope power systems (RPSs) currently being developed for space missions, and is capable of operating in a range of planetary atmospheres and in deep space. It has a mass of approximately 45 kg and produces more than 110We at beginning of mission (BOM), with a design lifetime of two years on the surface of Mars and fourteen years in deep space. Power is produced by PbTe thermoelectric elements heated by General Purpose Heat Source (GPHS) "bricks." The complete system is packed into a cylindrical container that is approximately 305 mm in diameter and 630 mm long (not including the fins). The MMRTG is being designed in 3 stages: Engineering Model, Qualification Unit, and Flight Unit. At the time of this submission, the Engineering Model was being assembled and will complete environmental testing near May, 2006. Completion of testing of the Qualification Unit is slated for December, 2007. The current plan would call for delivery of a flight unit and a spare to the Kennedy Space Center in March of 2009, well ahead of the September, 2009 launch opportunity. This development is being performed by Pratt and Whitney Rocketdyne (formerly Boeing Rocketdyne) and Teledyne Energy Systems under contract to the Department of Energy. Portions of this work were performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.
P54A-03
Europa Geophysical Explorer Mission Concept Studies
The Strategic Road Map for Solar System Exploration recommended in May 2005 that NASA implement the Europa Geophysical Explorer (EGE) as a Flagship mission early in the next decade. This supported the recommendations of the National Research Council's Solar System Decadal Survey and the priorities of the Outer Planets Assessment Group (OPAG). The Europa Geophysical Explorer would: (1) Characterize tidal deformations of the surface of Europa and surface geology, to confirm the presence of a subsurface ocean; (2) Measure the three-dimensional structure and distribution of subsurface water; and (3) Determine surface composition from orbit, and potentially, prebiotic chemistry, in situ. As the next step in Europa exploration, EGE would build on previous Europa Orbiter concepts, for example, the original Europa Orbiter and the Jupiter Icy Moons Orbiter (JIMO). As well, a new set of draft Level One Requirements, provided by NASA sponsors, guided the concept development. These requirements included: (1) Earliest Launch: 2012; (2) Launch Vehicle: Delta IV Heavy or Atlas V; (3) Primary Propulsion: Chemical; (4) Power: Radioisotope Power System (RPS); (4) Orbital Mission: 30 days minimum to meet orbital science objectives; and (5) Earth Gravity Assists: Allowed. The previous studies and the new requirements contributed to the development of several scientifically capable and relatively mass-rich mission options. In particular, Earth-gravity assists (EGA) were allowed, resulting in an increased delivered mass. As well, there have been advances in radiation-hardened components and subsystems, due to the investments from the X-2000 technology program and JIMO. Finally, developments in radioisotope power systems (RPS) have added to the capability and reliability of the mission. Several potential mission options were explored using a variety of trade study methods, ranging from the work of the JPL EGE Team of scientists and engineers in partnership with the OPAG Europa Sub-Group Advisory Team, JPL's Team X, and parametric modeling and simulation tools. We explored the system impacts of selecting different science payloads, power systems, mission durations, Deep Space Network (DSN) architectures, trajectory types, and launch vehicles. The comparisons show that there are feasible mission options that provide potentially available mass for enhanced spacecraft margins and science return, in addition to a 150-kg orbiter science instrument payload mass. This presentation describes high-priority science objectives for an EGE mission, results of the recent studies, and implementation options.
P54A-04 INVITED
Exploration of Titan by Balloon or Airship
Titan's surface is recognized as a focus for future exploration, yet Cassini shows it to be incredibly diverse - landers or even rovers to a handful of sites will not capture the range of phenomena and materials in this exotic landscape. Thus a platform able to access many widely-spaced locations on Titan is essential. Fortunately, Titan's low gravity and thick atmosphere lends itself to exploration by airborne vehicles such as balloons, airplanes, helicopters and airships. The latter vehicle type has received particular attention, since it combines 'go to' ability to traverse to and stationkeep at targets of interest, while being, unlike heavier-than-air vehicles, 'fail-safe' in terms of floating passively in an unpowered condition. In-situ analysis of surface chemistry can be performed using a tethered sampler. An airship or similar mission at Titan could be augmented by an orbiter, by remote sensing for mission planning and scientific context, by acting as a navigation beacon, and as a communications relay. However, none of these are essential. First, Cassini data allows the identification of target regions of interest at a level of a few kilometers - enough to know where the airship should explore further. Second, clear infrared windows in Titan's atmosphere permit the use of the Sun, Saturn and other targets as beacons for autonomous optical navigation at a large scale : optical odometry, correlation of landscape features with Cassini data, and the impressive Very Long Baseline Interferometry demonstrated by radio astronomers supporting Huygens may permit kilometer-scale location. Finally, while orbiter relay can increase the number of communication opportunities (depending on latitude) and the total data return, tens of megabits per day can be returned with direct-to-Earth communication. A portfolio of mission options therefore exists with a tradeoff of capability versus cost, from a passive balloon with direct-to-Earth only, to an airship with surface-sampling capability and a supporting orbiter. All of these options offer substantial scientific and public appeal, over a mission of genuine exploration that could last years at Titan.
P54A-05
The DOE/NASA SRG110 Program Overview
The Department of Energy is developing the Stirling Radioisotope Generator (SRG110) for NASAs Science Mission Directorate for potential surface and deep space missions. The SRG110 is one of two new radioisotope power systems (RPSs) currently being developed for NASA space missions, and is capable of operating in a range of planetary atmospheres and in deep space environments. It has a mass of approximately 27 kg and produces more than 125We(dc) at beginning of mission (BOM), with a design lifetime of fourteen years. Electrical power is produced by two (2) free-piston Stirlings convertor heated by two General Purpose Heat Source (GPHS) modules. The complete SRG110 system is approximately 38 cm x 36 cm and 76 cm long. The SRG110 generator is being designed in 3 stages: Engineering Model, Qualification Generator, and Flight Generator. Current plans call for the Engineering Model to be fabricated and tested by October 2006. Completion of testing of the Qualification Generator is scheduled for mid-2009. This development is being performed by Lockheed Martin, Valley Forge, PA and Infinia Corporation, Kennewick, WA under contract to the Department of Energy, Germantown, Md. Glenn Research Center, Cleveland, Ohio is providing independent testing and support for the technology transition for the SRG110 Program.
P54A-06
A Venus Rover Capable of Long Life Surface Operations
Access to the surface of Venus would allow planetary scientists to address a number of currently open questions. Among these are the elemental and mineralogical composition of the surface; the interaction of the surface with the atmosphere; the atmospheric composition, especially isotope ratios of key species; the nature of the planetary volcanism (present activity, emissions to the atmosphere, and composition); planetary seismicity; the local surface meteorology (winds and pressure variability); and the surface geology and morphology at particular locations on the surface. A long lived Venus rover mission could be enabled by utilizing a novel Stirling engine system for both cooling and electric power. Previous missions to the Venus surface, including the Pioneer Venus and Venera missions, survived for only a few hours. The rover concept described in the present study is designed for a surface lifetime of 60 days, with the potential of operating well beyond that. A Thermo-Acoustic Stirling Heat Engine (TASHE) would convert the high-temperature (~1200 °C) heat from General Purpose Heat Source (GPHS) modules into acoustic power which then drives a linear alternator and a pulse tube cooler to provide electric power and remove the large environmental heat load. The "cold" side of the engine would be furnished by the ambient atmosphere at 460 °C. This short study focused on the feasibility of using the TASHE system in this hostile environment to power a ~650 kg rover that would provide a mobile platform for science measurements. The instrument suite would collect data on atmospheric and surface composition, surface stratigraphy, and subsurface structure. An Earth-Venus-Venus trajectory would be used to deliver the rover to a low entry angle allowing an inflated ballute to provide a low deceleration and low heat descent to the surface. All rover systems would be housed in a pressure vessel in vacuum with the internal temperature maintained by the TASHE below 50 °C. No externally deployed or articulated components would be used and penetrations through the pressure vessel are minimized. Science data would be returned direct to Earth using S-Band to minimize atmospheric attenuation.
P54A-07 INVITED
Enabling Solar System Exploration with Small Radioisotope Power Systems
The increased use of smaller spacecraft over the last decade, in combination with studies of potential science applications, has suggested that a wide range of low power missions and applications could be enabled by a new generation of conceptual small radioisotope power systems with power levels in the range of 20 mW to a few 10's of watts. Such systems have the potential to extend the capability of small science payloads and instruments, and to enable applications such as long-lived meteorological/seismological stations broadly distributed across planetary surfaces, navigational beacons, small landers or rovers at extreme latitudes or in regions of low solar flux, surface and atmosphere-based mobility systems, subsurface probes, including autonomous boring devices, and deep space micro-spacecraft and sub-satellites. Such units could also find application in future human exploration missions involving use of monitoring stations and autonomous devices, similar to the ALSEP units deployed on the Moon during the Apollo program. We present descriptions and performance predictions of conceptual milliwatt and multi-watt class small RPS designs. Our team has performed a number of mission studies to evaluate the potential contributions of small RPS systems. Among these are a long-duration Europa lander; MER-class Lunar and Mars rovers; small seismic monitoring stations; and an adjunct satellite for performing deep space fields and particles measurements. Although flight-qualified small RPS units do not presently exist, their potential to support a broad range of exploration tasks has led NASA and the Department of Energy (DOE) to consider their development such that they might be available for missions by the early part of next decade.
P54A-08
Europa Small Lander Design Concepts
Title: Europa Small Lander Design Concepts Authors: Wayne F. Zimmerman, James Shirley, Robert Carlson, Tom Rivellini, Mike Evans One of the primary goals of NASA's Outer Planets Program is to revisit the Jovian system. A new Europa Geophysical Explorer (EGE) Mission has been proposed and is under evaluation. There is in addition strong community interest in a surface science mission to Europa. A Europa Lander might be delivered to the Jovian system with the EGE orbiter. A Europa Astrobiology Lander (EAL) Mission has also been proposed; this would launch sometime after 2020. The primary science objectives for either of these would most likely include: Surface imaging (both microscopic and near-field), characterization of surface mechanical properties (temperature, hardness), assessment of surface and near-surface organic and inorganic chemistry (volatiles, mineralogy, and compounds), characterization of the radiation environment (total dose and particles), characterization of the planetary seismicity, and the measurement of Europa's magnetic field. The biggest challenges associated with getting to the surface and surviving to perform science investigations revolve around the difficulty of landing on an airless body, the ubiquitous extreme topography, the harsh radiation environment, and the extreme cold. This presentation reviews some the recent design work on drop-off probes, also called "hard landers". Hard lander designs have been developed for a range of science payload delivery systems spanning small impactors to multiple science pods tethered to a central hub. In addition to developing designs for these various payload delivery systems, significant work has been done in weighing the relative merits of standard power systems (i.e., batteries) against radioisotope power systems. A summary of the power option accommodation benefits and issues will be presented. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract from NASA,