Robert D. Abelson

Exploring Europa with an RPS-powered orbiter spacecraft

The National Research Councils solar system exploration decadal survey identified Jupiters moon Europa as its highest-priority destination for near-term exploration. Voyager and Galileo missions to the Jupiter system provided evidence consistent with a subsurface ocean on Europa, which is of great interest as a potential abode for extraterrestrial life. This paper describes a conceptual flagship-class Europa orbiter concept that was assumed to launch as early as 2012, arriving at Europa approximately 8 years later using inner solar system gravity assists to reach Jupiter. Jupiters intense radiation environment limits the mission duration at Europa to 30 days for this study, though the duration is a result of multiple trades and is by no means fixed. The Europa subgroup of the outer planets assessment group identified six primary science objectives for this concept. An ~150-kg instrument suite selected for the study addresses those objectives. Large heliocentric distances, high power levels required, and especially the harsh Jovian radiation environment drove the selection of radioisotope thermoelectric generators (RTGs) for all onboard electrical power, with the excess heat aiding spacecraft thermal control. Mass and architecture trades were performed using different spacecraft trajectories, launch vehicle types, radioisotope power systems, and mission durations. The study shows that new mission constraints allow a scientifically compelling Europa orbiter mission that might also deliver a Europa lander

Exploring Europa with a Surface Lander Powered by a Small Radioisotope Power System (RPS)

Europa is a high‐priority target for future exploration because of the possibility that it may possess a subsurface liquid ocean that could sustain life. Exploring the surface of this Galilean moon, however, represents a formidable technical challenge due to the great distances involved, the high ambient radiation, and the extremely low surface temperatures. A design concept is presented for a Europa Lander Mission (ELM) powered by a small radioisotope power system (RPS) that could fly aboard the proposed Jupiter Icy Moons Orbiter (JIMO). The ELM would perform in‐situ science measurements for a minimum of 30 Earth days, equivalent to approximately 8.5 Europa days. The primary science goals for the Europa lander would include astrobiology and geophysics experiments and determination of surface composition. Science measurements would include visual imagery, microseismometry, Raman spectroscopy, Laser Induced Breakdown Spectroscopy (LIBS), and measurements of surface temperature and radiation levels. The ELM...

Preliminary Analysis of the 30-m Ultraboom Flight Test Article

Future NASA missions require long, ultra-lightweight booms to enable solar sails, large sunshields, and other gossamer-type spacecraft structures. The space experiment discussed in this paper will flight validate the non-traditional ultra lightweight rigidizable, inflatable, isogrid structure utilizing graphite shape memory polymer (GR/SMP) called UltraBoom™. The focus of this paper is the analysis of the 3-m ground test article. The primary objective of the mission is to show that a combination of ground testing and analysis can predict the on-orbit performance of an ultra lightweight boom that is scalable, predictable, and thermomechanically stable.

The Europa Explorer — A Fresh Look at Exploring Europa with an RPS‐Powered Spacecraft

An orbital mission to Europa has been identified as a high priority by the science community for several years. The difficulty of this type of mission, primarily due to the propulsive requirements and Jupiter’s trapped radiation, led to many studies which investigated various approaches to meeting the science goals. A flagship‐class Europa orbiting mission, which performs a multi‐year study of the Jupiter system, can now be envisioned relying on existing technologies, having significantly more capability and returning considerably more science data than previous conventional propulsion mission concepts. This study resulted in several mission concept designs ranging significantly in capability and commensurate cost. The concept discussed herein returns three year’s worth of Cassini data (∼3 Tbit) in approximately 90 days around Europa. During its 3 month (90 day) Europa Prime Mission, the spacecraft would orbit Europa over 1000 times and provide three orders of magnitude more close (<5000 km altitude) Euro...

A Saturn Ring Observer Mission Using Multi-Mission Radioisotope Power Systems

Saturn remains one of the most fascinating planets within the solar system. To better understand the complex ring structure of this planet, a conceptual Saturn Ring Observer (SRO) mission is presented that would spend one year in close proximity to Saturn’s A and B rings, and perform detailed observations and measurements of the ring particles and electric and magnetic fields. The primary objective of the mission would be to understand ring dynamics, including the microphysics of individual particles and small scale (meters to a few kilometers) phenomena such as particle agglomeration behavior. This would be accomplished by multispectral imaging of the rings at multiple key locations within the A and B rings, and by ring‐particle imaging at an unprecedented resolution of 0.5 cm/pixel. The SRO spacecraft would use a Venus‐Earth‐Earth‐Jupiter Gravity Assist (VEEJGA) and be aerocaptured into Saturn orbit using an advanced aeroshell design to minimize propellant mass. Once in orbit, the SRO would stand off fr...

Deployable Mini-Payload Missions Enabled by Small Radioisotope Power Systems (RPSs)

Deployable mini‐payloads are envisioned as small, simple, standalone instruments that could be deployed from a mother vehicle such as a rover or the proposed Jupiter Icy Moons Orbiter to key points of interest within the solar system. Used in conjunction with a small radioisotope power system (RPS), these payloads could potentially be used for long‐duration science missions or as positional beacons for rovers or other spacecraft. The RPS power source would be suitable for deployable mini‐payload missions that would take place anywhere there is limited, intermittent, or no solar insolation. This paper introduces two such concepts: (1) a seismic monitoring station deployed by a rover or aerobot, and (2) a passive fields and particles station delivered by a mother spacecraft to the Jupiter system.

Ultra Lightweight Isogrid Boom Space Experiment (UltraBoom) Systems Design

The purpose of the Ultra-Lightweight Isogrid Boom Space Experiment is to flight validate the non-traditional ultra lightweight rigidizable-inflatable, isogrid structure utilizing a composite graphite/shape memory polymer called UltraBoomTM. The goal of the flight experiment is to raise the technology readiness level of this enabling technology from 4 (i.e. component validated in a laboratory environment) to 7 (i.e. system demonstrated in a space environment) and to reduce risks for future missions. The UltraBoom Flight System envisioned for NASA’s New Millennium Program (NMP) Space Technology 8 (ST-8) project consists of two 30-meter long UltraBooms integrated onto a common honeycomb composite baseplate that also support the metrology system, inflation system, and avionics equipment. The system design of the flight experiment is currently at the preliminary design review (PDR) level and is ready to move into the refinement phase. The focus of this paper is on the systems design of the flight experiment and how it will meet the mission objectives.

Multi‐Watt Small Radioisotope Thermoelectric Generator Conceptual Design Study

A need has been identified for a small, light‐weight, reliable power source using a radioisotope heat source, to power the next generation of NASA’s small surface rovers and exploration probes. Unit performance, development costs, and technical risk are key criteria to be used to select the best design approach. Because safety can be a major program cost and schedule driver, RTG designs should utilize the DOE radioisotope safety program’s data base to the maximum extent possible. Other aspects important to the conceptual design include: 1) a multi‐mission capable design for atmospheric and vacuum environments, 2) a module size based on one GPHS Step 2 module, 3) use of flight proven thermoelectric converter technologies, 4) a long service lifetime of up to 14 years, 5) maximize unit specific power consistent with all other requirements, and 6) be ready by 2013. Another critical aspect of the design is the thermal integration of the RTG with the rover or probe’s heat rejection subsystem and the descent vehicle’s heat rejection subsystem. This paper describes two multi‐watt RTG design concepts and their integration with a MER‐class rover.A need has been identified for a small, light‐weight, reliable power source using a radioisotope heat source, to power the next generation of NASA’s small surface rovers and exploration probes. Unit performance, development costs, and technical risk are key criteria to be used to select the best design approach. Because safety can be a major program cost and schedule driver, RTG designs should utilize the DOE radioisotope safety program’s data base to the maximum extent possible. Other aspects important to the conceptual design include: 1) a multi‐mission capable design for atmospheric and vacuum environments, 2) a module size based on one GPHS Step 2 module, 3) use of flight proven thermoelectric converter technologies, 4) a long service lifetime of up to 14 years, 5) maximize unit specific power consistent with all other requirements, and 6) be ready by 2013. Another critical aspect of the design is the thermal integration of the RTG with the rover or probe’s heat rejection subsystem and the descent veh...

A Conceptual Titan Orbiter with Probe Mission Using Advanced Radioisotope Power Systems

With the remarkable success of the Cassini‐Huygens mission, considerable new knowledge has been obtained regarding the surface topography, composition and atmospheric characteristics of Titan. However, Cassini‐Huygens represents only a bold beginning for the exploration of Titan, as high resolution mapping will have been performed for only a small fraction of the surface of Titan by the end of the nominal mission. Large gaps in knowledge will remain in key scientific areas including global surface topography, atmospheric and surface composition, precipitation rates, and the density, thickness, and formation processes of clouds. This study details a conceptual follow‐on Titan orbiter mission that would provide full global topographic coverage, surface imaging, and meteorological characterization of the atmosphere over a nominal 2‐year science mission duration. The reference power requirement is ∼1 kWe at EOM and is driven by a high power radar instrument that would provide 3‐dimensional measurements of atm...

A Conceptual Venus Rover Mission Using Advanced Radioisotope Power Systems

This concept study demonstrates that a long lived Venus rover mission could be enabled by a novel application of advanced RPS technology. General Purpose Heat Source (GPHS) modules would be employed to drive an advanced thermoacoustic Stirling engine, pulse tube cooler and linear alternator that provides electric power and cooling for the rover. The Thermoacoustic Stirling Heat Engine (TASHE) is a system for converting high‐temperature heat into acoustic power which then drives linear alternators and a pulse tube cooler to provide both electric power and coolin6g for the rover. A small design team examined this mission concept focusing on the feasibility of using the TASHE system in this hostile environment. A rover design is described that would provide a mobile platform for science measurements on the Venus surface for 60 days, with the potential of operating well beyond that. A suite of science instruments is described that collects data on atmospheric and surface composition, surface stratigraphy, and...