Craig E. Peterson

Multi-mission radioisotope thermoelectric generator (MMRTG) program overview

Future NASA missions require safe, reliable, long-lived power systems for surface exploration of planetary bodies such as Mars as well as exploration of the solar system in the vacuum of space beyond Earth orbit. To address this need, the Department of Energy and NASA have initiated the development of radioisotope power systems, including the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). In June of 2003, the Department of Energy (DOE) awarded the MMRTG system design, development, test and integration contract to a team led by the Boeing Companys Rocketdyne Propulsion and Power Division. Boeing and Teledyne Energy Systems collaborated on an MMRTG design concept based on heritage, SNAP 19, thermoelectric converter design utilized by Teledyne for previous space exploration missions. Boeing subsequently awarded a major subcontract to Teledyne Energy Systems to design and produce the thermoelectric converter system for the MMRTG. The MMRTG is designed to operate on planetary bodies as well as in the vacuum of space. At beginning of mission, the MMRTG is designed to generate a minimum of 110 Watts of power at 28 volts DC, and to have a design life of at least 14 years. The power level was selected to afford the capabilities of meeting the potential needs of a wider variety of planetary lander and deep space missions. Potential mission concepts that could benefit from use of the MMRTG include a Titan Biological Explorer - with both a balloon mission and a rover mission, the Mars Science Laboratory (MSL), with a follow-on Astrobiology Field Laboratory mission and finally a Neptune/Triton Orbiter mission.

The Zeus Mission Study — An application of automated collaborative design

Abstract The purpose of the Zeus Mission Study was threefold. As an element of a graduate course in spacecraft system engineering, its purpose was primarily educational — to allow the students to apply their knowledge in a real mission study. The second purpose was to investigate the feasibility of applying advanced technology (the power antenna and solar electric propulsion concepts) to a challenging mission. Finally, the study allowed evaluation of the benefits of using quality-oriented techniques (Quality Function Deployment (QFD) and Taguchi Methods) for a mission study. To encourage innovation, several constraints were placed on the study from the onset. While the primary goal was to place at least one lander on Europa, the additional constraint of no nuclear power sources posed an additional challenge, particularly when coupled with the mass constraints imposed by using a Delta II class launch vehicle. In spite of these limitations, the team was able to develop a mission and spacecraft design capable of carrying three simple, lightweight, yet capable landers. The science return will more than adequately meet the science goals established QFD was used to determine the optimal choice of instrumentation. The lander design was selected from several competing lander concepts, including rovers. The carrier design was largely dictated by the needs of the propulsion system required to support the mission, although the development of a Project Trades Model (PTM) in software allowed for rapid recalculation of key system parameters as changes were made. Finally, Taguchi Methods (Design of Experiments) were used in conjunction with the PTM allowing for some limited optimization of design features.

Evaluating Low Concept Maturity Mission Elements and Architectures for a Venus Flagship Mission

NASA’s Planetary Science Division recently commissioned a Science and Technology Definition Team to design a potential Venus Flagship mission. The team developed a list of various mission elements that could serve as parts of an overall mission architecture, including orbiters, balloons at various altitudes, and landed platforms of varying number and lifetime. In order to determine the mission architecture that provided the best science within the desired cost range, teams of scientists developed priorities for the science investigations previously detailed by the Venus Exploration Assessment Group (VEXAG). By categorizing the suitability of mission elements to achieve the science investigations, it was possible to construct a Science Figure of Merit (FOM) that could be used to rate the mission elements in terms of their overall science capability. Working in parallel, a team of technologists and engineers identified the technologies needed for the different mission elements, as well as their technology readiness. A Technology FOM was then created reflecting the criticality of a specific technology as well as its technology readiness level. When the Science and Technology FOMs were combined with a rapid costing approach previous developed, it became possible to rapidly evaluate not only individual mission elements, but also their combinations into various mission architectures, accelerating the convergence on a flagship mission architecture that provided the best science within the flagship mission budget, as well as reducing reliance on unproven technology..

Model-based spacecraft and mission design for the evaluation of technology

In order to meet the future vision of robotic missions, engineers will face intricate mission concepts, new operational approaches, and technologies that have yet to be developed. The concept of smaller, model driven projects helps this transition by including life-cycle cost as part of the decision making process. For example, since planetary exploration missions have cost ceilings and short development periods, heritage flight hardware is utilized. However, conceptual designs that rely solely on heritage technology will result in estimates that may not be truly representative of the actual mission being designed and built. The Laboratory for Spacecraft and Mission Design (LSMD) at the California Institute of Technology is developing integrated concurrent models for mass and cost estimations. The purpose of this project is to quantify the infusion of specific technologies where the data would be useful in guiding technology developments leading up to a mission. This paper introduces the design-to-cost model to determine the implications of various technologies on the spacecraft system in a collaborative engineering environment. In addition, comparisons of the benefits of new or advanced technologies for future deep space missions are examined

Engineering data re-use at JPL: promise and perils

Previously, a new approach to sharing engineering data using a JPL developed Product Attribute Database (PAD) was described. Since its development the PAD has been used on several projects at JPL with mixed results. The lessons learned in its implementation have wider implications for engineering processes and the associated data that is produced and consumed during a projects life cycle. In addition to the normal resistance of personnel to adopt a new tool whos benefits are not yet quantified in practice, the need to spend substantial effort early on to establish and promulgate a common understanding of the data has impeded acceptance and use of the PAD. The limitations of the original user interface and the lack of existing project data (either in template or detailed form) has also played a role in delaying widespread user acceptance. Despite these drawbacks, the initial use of the PAD has highlighted misunderstandings regarding definition of engineering data and has led to numerous fruitful discussions among engineering disciplines. Even apparently intuitively obvious data such as the total flight system mass or the spacecraft mechanical configuration coordinate system have required refinement to eliminate the natural ambiguity that engineers routinely accommodate, but that leads to confusion when automated modeling tools are the creators and consumers of the data. These discussions have led to increased insight into engineering processes, particularly those using the model based design approach that is now being implemented at JPL.

Overview of NASA's 2006 SSE Strategic Roadmap

In the 2003 solar system exploration (SSE) decadal survey, the national research council (NRC) prioritized scientific targets and recommended missions to explore them. Taking these into account, NASAs 2006 solar system exploration (SSE) strategic roadmap (SRM) identified a set of large flagship, medium new frontiers (NF) and small discovery class missions, addressing key exploration objectives. Discovery and NF missions are competed, and due to their lower cost caps, address fewer science objectives than the large missions, while mostly utilizing existing technologies. Directed flagship class missions are considered necessary to answer some of the most important questions on solar system formation and habitability. They also provide drivers for technology development, which in turn would benefit all mission classes. Additionally, this SSE SRM offers a comprehensive discussion on science objectives for solar system exploration, and technologies enabling these missions. It outlines research and analysis (R&A), which is required to maintain the proposed program, and to post process scientific data. Education and public outreach (E/PO) communicates NASAs activities to the public of all ages, and as discussed, is considered an important part of the agencys programs. These elements are connected through interdependencies and links to other programmatic activities, including the mars and new millennium programs. The roadmap also explores potential implementation trades, suggesting multiple ways to execute a balanced program that consist of all mission classes and supported by technology development, R&A, and E/PO, while staying within a projected budget allocation for SSE. In this paper we outline this proposed SSE strategic roadmap, representing NASAs exploration plans for the next three decades.

Overview of High Priority Technologies for Solar System Exploration

During the past two years, a new solar system exploration roadmap has been developed, supplanting the previous 2003 version. This roadmap identifies a number of high priority technology developments that will be essential to the success of several of the roadmap missions. These technologies include advanced radioisotope power systems (RPS), aerocapture systems and advanced propulsion, numerous technologies capable of surviving the extreme environments encountered in many of these missions, and improved capabilities for both forward and back planetary protection. These key technologies and the missions that require them are described, along with the estimated timeline for their development as laid out in the exploration roadmap.