NASA's Space Vision: Business Case for Prometheus 1 Needed to Ensure Requirements Match Available Resources
Released: 2005-03-22T00:00:00

Letter

Background

The Prometheus 1 project is part of NASA’s Prometheus Nuclear Systems and Technology program to develop nuclear power technologies capable of providing power and propulsion for a new generation of missions. The Prometheus 1 spacecraft is being designed to use nuclear power and electric propulsion technologies to explore the outer reaches of the solar system. The Jupiter Icy Moons Orbiter (JIMO) mission—a 4 to 6-year study of three of Jupiter’s moons: Callisto, Europa, and Ganymede—was the original destination identified by NASA. The JIMO mission’s overarching science objectives were to (1) investigate the origin and evolution of the three moons; (2) scout their potential for sustaining life; and (3) determine the current rate of movement of surface ice and the rates at which the moons are weathered. With an unprecedented level of power, Prometheus 1, the first in a potential series of spacecraft, is expected to support the use of high capability science instruments and high power communications systems to provide scientists with an a unprecedented amount of scientific information. Figure 1 depicts the notional Prometheus 1 spacecraft.

NASA contracted with the Jet Propulsion Laboratory (JPL) to manage the Prometheus 1 project and to manage development of the science mission payload. In turn, JPL awarded a $400-million contract for the initial development of the Prometheus 1 spacecraft to Northrop Grumman Space Technology in September 2004. NASA is collaborating with the Department of Energy’s Office of Naval Reactors to develop and handle all issues related to the spacecraft’s nuclear reactor.

The Prometheus 1 project will have to compete for funding with other NASA programs. In January 2004, the President charged NASA with implementing a new strategy for space exploration—which includes the Prometheus 1 project—while simultaneously returning the shuttle to flight status and completing the International Space Station. NASA laid out its plan for implementing the strategy in its fiscal year 2005 budget request. In essence, NASA’s implementation plan holds aeronautics, science, and other activities at near constant levels and transitions funding levels currently dedicated to the Space Station and shuttle programs to the space exploration strategy as the Space Station and shuttle programs phase out. This plan was predicated upon NASA’s annual funding level receiving increases to about $18 billion a year by fiscal year 2008 and then remaining near that level, except for inflation, through at least 2020.

Best Practices Reveal Elements of a Sound Business Case for Product Development

In the last several years, we have undertaken a best practices body of work on how leading developers in industry and government use a knowledge-based approach to develop products that reduces risks and increases the likelihood of successful outcomes. Development of a sound business case based on this best practices model enables decision makers to be reasonably certain about their products at critical junctures during development and helps them make informed investment decisions.

Our best practice work has shown that developing a sound business case based on matching requirements to resources is essential to implementing a knowledge-based approach. A sound business case includes the following elements well-defined requirements, preliminary design, realistic cost estimates, and mature technology.

A knowledge-based business case also involves the use of controls or exit criteria to ensure that the required knowledge has been attained at each critical juncture. It ensures that managers will (1) conduct activities to capture relevant product development knowledge, (2) provide evidence that knowledge was captured, and (3) hold decision reviews to determine that appropriate knowledge was captured to allow a move to the next phase. If the knowledge attained at each juncture does not confirm the business case on which the effort was originally justified, the program does not go forward.

Use of this approach has enabled leading organizations to deliver high quality products on time and within budget. Product development efforts that have not followed a knowledge-based business case approach can be frequently characterized by poor cost, schedule, and performance outcomes.

Although NASA does not require projects to develop a formal business case based on matching requirements to resources, JPL project implementation policy, which establishes JPL’s institutional structure for implementation and management of JPL flight projects in accordance with NASA policies, does require projects to develop documentation that includes elements essential to a sound business case. For example, before entering the preliminary design phase, JPL projects are required to develop preliminary requirements, a conceptual design, realistic cost estimates, and technology development plans. JPL projects are required to update and improve the fidelity of information in these documents by PDR. The information in these documents could provide NASA decision makers with the information necessary to support sound business case decisions based on matching requirements to resources at preliminary mission and systems review (PMSR) and PDR.

In September 2004, the Congressional Budget Office reported that if NASA’s costs for implementing the strategy were similar to prior analogous NASA programs—such as Apollo, Viking, and Mars Exploration Rover—NASA’s funding needs could increase by 15 to 23 percent—or $40 billion to $61 billion—over the 16-year estimate. The Congressional Budget Office concluded that if funding were held constant, NASA would likely have to either eliminate mission content or delay schedules.

Initial Justification for Prometheus 1 Project Could Form the Basis of a Sound Business Case

NASA is still in the process of preparing initial justification for the Prometheus 1 project to enter the preliminary design phase. Consequently, at this time the level of funding NASA needs to execute the project is not fully defined. According to project officials, however, funding levels would need to be increased to support the planned launch of Prometheus 1 to Jupiter’s Icy Moons. While NASA plans to have defined preliminary system requirements and an initial estimate of the life-cycle cost for Prometheus 1 by summer 2005—when the project enters the preliminary design phase— the agency faces significant challenges in doing so.

Project Management Believes Current Funding Is Insufficient to Support Launch of Prometheus 1

According to Prometheus 1 project management, current funding is inadequate to support a 2015 launch of Prometheus 1 as initially planned. Following small funding increases from fiscal years 2005 through 2007, the budget profile becomes relatively flat through fiscal year 2009 (see fig. 2). Project officials believe that the current profile would need to be increased beginning in fiscal year 2007 to reflect project needs of a Jupiter Icy Moons mission. Decision makers will not get their first comprehensive picture of the project’s requirements and the resources needed to meet those requirements—the first basis for funding decisions—until PMSR scheduled for summer 2005. While the fiscal year 2006 request includes an updated Prometheus 1 funding profile, a funding profile based on life-cycle cost estimates—which NASA plans to have when it enters the preliminary design phase—will not be included until NASA’s fiscal year 2007 request.

Short Time Frames and History Foretell Difficulty in Defining Requirements and Developing Life-Cycle Cost Estimates

The Prometheus 1 project office is required to develop preliminary requirements by PMSR. Defining the project’s requirements and developing life-cycle cost estimates by then could be challenging, given the short time frames and NASA’s past difficulties developing requirements and estimates. While it is not unusual for a project at this stage in acquisition to still be defining requirements, several factors could make it difficult for NASA to develop preliminary requirements by PMSR. The contractor, Northrop Grumman, was only recently selected, and according to project officials, input from both the contractor and Office of Naval Reactors is needed to finalize the preliminary ground, space, and launch systems requirements mandatory for PMSR. In addition, NASA continues to refine its requirements. For example, Prometheus 1 project management increased requirements for reactor lifetime, reactor power, and propellant tank capacity to ensure that the Prometheus 1 spacecraft and reactor designs could be used to support follow-on missions. Currently, project managers are working with broad NASA requirements for deep space exploration and more refined project requirements specific to the Prometheus 1 ground, space, and launch systems.

NASA is also required to have an initial life-cycle cost estimate for Prometheus 1 at PMSR. However, because the estimate is based on a conceptual design, preliminary system requirements, and detailed technology development plans that are not yet complete, it will be difficult for NASA to develop an estimate in the short time available by PMSR.

The project office is working with Northrop Grumman to merge and finalize the conceptual design. Once the conceptual design is finalized, the project office will update the work breakdown structure and develop a “grass roots” estimate of the spacecraft cost. However, project officials do not expect to receive cost estimates from the Office of Naval Reactors and Northrop Grumman, which are also needed to develop the estimate, until the end of February 2005. The JPL Costing Office will prepare a separate cost estimate based on its experiences with prior programs, and both JPL and NASA will contract for additional independent cost estimates.

Adding to these complexities, NASA has historically had difficulty establishing life-cycle cost estimates. In May 2004, we reported that NASA’s basic cost-estimating processes—an important tool for managing programs—lack the discipline needed to ensure that program estimates are reasonable. Specifically, we found that 10 NASA programs that we reviewed in detail did not meet all of our cost-estimating criteria—based on criteria developed by Carnegie Mellon University’s Software Engineering Institute. Moreover, none of the 10 programs fully met certain key criteria—including clearly defining the program’s life cycle to establish program commitment and manage program costs, as required by NASA. In addition, only three programs provided a breakdown of the work to be performed. Without this knowledge, we reported that the programs’ estimated costs may be understated and thereby subject to underfunding and cost overruns, putting programs at risk of being reduced in scope or requiring additional funding to meet their objectives. In this report we recommended that NASA take a number of actions to improve its cost - estimating practices. NASA concurred noting that our recommendations validated and reinforced the importance of activities underway at NASA.

Business Case Allows Match of Needs to Resources and Facilitates Informed Decision Making

By PDR—which occurs at end of the preliminary design phase and is scheduled for 2008—the fidelity of the information is expected to improve and could allow NASA to develop a business case that would match requirements with resources and provide decision makers with the information needed to determine whether continued investment in the project is warranted. However, in the past NASA has had difficulties developing the realistic requirements and cost estimates needed to develop a sound business case.

To help ensure program requirements do not outstrip resources, leading commercial firms obtain the right knowledge about a new product’s technology, design, and production at the right time. We have issued a series of reports on the success these firms have had in estimating the time and money to develop new and more sophisticated products—the kinds of results that NASA seeks. Our best practice work has shown that developing business cases based on matching requirements to resources before program start leads to more predictable program outcomes—that is, programs are more likely to be successfully completed within cost and schedule estimates and deliver anticipated system performance.

A sound business case includes the following elements—well-defined requirements, a preliminary design, realistic cost estimates, and mature technology. While NASA does not require projects to develop a formal business case based on matching requirements to resources, JPL policy, which implements NASA policy, does require projects to develop documentation that could support formulation of a sound business case. Before a JPL project enters the preliminary design phase, JPL project implementation policy requires that the project develop preliminary requirements, a conceptual design, realistic cost estimates, and technology development plans. This policy also requires that the fidelity of information in these documents improve by PDR.

The requirements and resource estimates NASA is developing for PMSR could form the basis for an initial business case based on matching Prometheus 1 requirements to available resources. However, Prometheus 1 project management plans to continue directing requirements changes to accommodate follow-on missions. While our work shows that the preliminary design phase is the appropriate place to conduct systems engineering to support requirement/cost trade-off decisions, NASA needs to remain cognizant that adding requirements could increase cost and risk. In addition, NASA has had past difficulty developing the realistic requirements and cost estimates needed to develop a sound business case. These difficulties have resulted in the termination of several major efforts after significant investment of resources. For example, in 2002 NASA terminated the Space Launch Initiative (SLI) program—a $4.8 billion, 5-year program to build a new generation of space vehicles to replace its aging space shuttle. SLI was a complex and challenging endeavor for NASA, both technically and from a business standpoint. The SLI program faced some of the same challenges that Prometheus 1 is struggling with today, such as the need to develop and advance new airframe and propulsion technologies. SLI did not achieve its goals, in part, because NASA did not develop realistic requirements and cost estimates.

NASA’s Plans to Ensure Mature Technologies Rely on Prototype Demonstrations

Leading firms make an important distinction between technology development and product development. Technologies that are not mature continue to be developed in the technology base—they are not included in a product development. Our best practices work has also shown that there is a direct relationship between the maturity of technologies and the accuracy of cost and schedule estimates. NASA’s Prometheus 1 technologies are currently immature. The Prometheus 1 project office is preparing technology development plans to guide the development of each key technology during the preliminary design phase.

Mature Technologies Are Key to Minimizing Risk

Maturing technologies during the preliminary design phase is a key element of matching needs to resources before entering the product development phase. Our best practices work has shown that technology readiness levels (TRL)—a concept developed by NASA—can be used to gauge the maturity of individual technologies (see fig. 4). (See app. I for detailed definition of TRLs.) Specifically, TRL 6—demonstrating a technology as a fully integrated prototype in a realistic environment—is the level of maturity needed to minimize risks for space systems entering product development.

While development of Prometheus 1 critical technologies is under way, the technologies will require extensive advancement before they are mature enough to provide the revolutionary capabilities of the Prometheus 1 spacecraft. The overall technology objective for Prometheus 1 is to safely develop and operate a spacecraft with a nuclear-reactor-powered electric propulsion system. To achieve this objective, the spacecraft will require advancement in several technology areas, including, nuclear electric power, power conversion and heat rejection systems, nuclear electric propulsion, high power communications, radiation-hardened electronics, and AR&D. (See app. II for a more detailed explanation of these technologies.) NASA’s fiscal year 2005 budget request indicates that these technologies are either at TRL 3 (individual technologies have been demonstrated in a laboratory environment) or TRL 4 (system components have been demonstrated in a laboratory environment). Before NASA conducts the PDR in 2008, it will need to mature the technologies—each of which comes with a unique set of engineering challenges.

To gauge the maturation of the Prometheus 1 technologies, the Prometheus 1 project office is preparing technology development plans, which rely on the use of maturity criteria tables (MCT), a concept similar to TRLs. The specific maturation criteria for each technology vary greatly, but all technologies are to be matured by PDR to the point that developmental models are complete, all major risks to each technology are retired, all major manufacturing issues are resolved, and plans for obtaining life data that will provide confidence that the hardware will meet the mission lifetime requirements are in hand.

Prometheus 1 project officials believe these criteria roughly correspond to a TRL 5 (component and/or breadboard validation in a relevant environment) or a TRL 6 (system/subsystem model or prototype demonstration in a relevant environment). The program office’s position is that using MCTs that are equivalent to TRL 5 and TRL 6 at PDR is appropriate because the program office is both the technology developer and product developer and, as such, has a thorough understanding of how mature the technologies need to be at certain points in time as the program progresses. Nevertheless, the dual role of project office as both technology and product developer is not unique, and our best practices body of work shows that a TRL 6 is the level of maturity needed to minimize risks for space systems entering product development.

Conclusions

NASA is quickly approaching one of the most critical phases in its acquisition of Prometheus 1—the preliminary design phase. While the impetus for the changes made to the program—subsequent to our providing a draft of this report to NASA for comment—recognize the technical, schedule, and operational risk of this program, there is still much work to be done. Based on the information presented at PMSR, now scheduled for summer 2005, NASA will need to decide at what level to fund the project. However, NASA will be challenged to develop the information required at PMSR, given the compressed time frames. Although PDR is still several years out, NASA will face significant challenges in meeting this milestone, given the immaturity of the revolutionary technologies that NASA anticipates will be needed to successfully launch Prometheus 1. While NASA is developing well-defined criteria tables for maturing Prometheus 1 technologies, the many inherent unknowns in developing technologies frequently results in unanticipated difficulties and delays. NASA’s current policy does not require projects to develop knowledge-based business cases that match requirements to available resources and include controls to ensure that sufficient knowledge has been attained and therefore the agency had not planned to develop such a business case for Prometheus 1. We have found, however, that establishing a formal business case based on a knowledge-based approach that includes matching requirements and available resources— which include technical and engineering knowledge, time and funding— and controls to ensure that sufficient knowledge has been attained at critical junctures within the product development process is an essential part of any product development justification. The risk associated with failing to meet these challenges is considerable. If NASA decides to move forward without adequate information at PMSR—that matches requirements and available resources and provides NASA decision makers with a clear understanding of Prometheus 1’s potential return on investment—Prometheus 1 may be unable to compete for funding within NASA. Ultimately, NASA could find, as it has in the past, that the program must be cancelled after having invested millions of dollars.

Recommendations for Executive Action

We recommend that the NASA Administrator take the following two actions: identify at PMSR the level of resources the agency is committing to the project and direct project officials to develop project requirements based on this resource constraint and ensure that prior to proceeding beyond PDR (currently planned for 2008) a sound business case is established which includes confirmation that (1) critical technologies have been successfully demonstrated as mature, (2) systems engineering has been conducted to support requirements/cost trade-off decisions, (3) requirements and resource estimates have been updated based on the results of the preliminary design phase, (4) knowledge based criteria are established at each critical juncture to ensure that relevant product development knowledge is captured, and (5) decision reviews are held to determine that appropriate knowledge was captured to allow a move to the next phase.

Agency Comments

In written comments on a draft of this report, NASA’s Deputy Administrator stated that the agency concurs with the recommendations, adding that the recommendations validate and reinforce the importance of activities underway at NASA to improve NASA’s management of complex technical programs.

Subsequent to our draft report being provided to NASA for comment, significant changes were made to the Prometheus 1 project. NASA’s fiscal year 2006 budget request includes changes to the Prometheus 1 project that directly address the recommendations in this report. According to NASA’s budget justification, the agency is planning a less complex mission than the original JIMO mission. According to program officials who we consulted with following the release of the budget, eliminating the long reactor lifetime, stringent radiation hardening, multiple launches, and AR&D required for the JIMO mission will allow NASA “to walk before it runs” and significantly reduce cost and technical risks. As a result, NASA has delayed PMSR until summer 2005 and is conducting an analysis of alternatives to identify a relevant mission with reduced technical, schedule, and operational risk. The fiscal year 2006 budget request also reshapes the Prometheus 1 funding profile to provide an orderly increase in developmental activities.

Notwithstanding agreement with our recommendations, the Deputy Administrator stated that NPR 7120.5B requires projects to develop a business case. As we noted in this draft report, we recognize that NASA policy requires the development of elements that could support the formulation of a knowledge-based business case. However, we found no explicit requirement within NPR 7120.5B for NASA projects to develop a business case of any kind. More importantly, while NPR 7120.5B does require that projects establish controls to monitor performance against cost, schedule, and performance baselines and to conduct reviews throughout the project’s lifecycle, it does not establish specific knowledge- based controls to ensure that the knowledge necessary to match resources to requirements is in hand before moving forward. For example, whereas NPR 7120.5B requires projects to conduct a preliminary design review before entering NASA’s implementation phase, i.e., product development, it does not establish knowledge-based criteria to ensure that technologies needed to meet essential product requirements have been demonstrated to work in a realistic environment. Likewise, NASA policy requires a critical design review during a project’s implementation phase but does not include knowledge-based criteria to ensure the design is stable. We have found that such knowledge-based criteria, when tied to major events on a program’s schedule, can disclose whether gaps or shortfalls exist in demonstrated knowledge, which can presage future cost, schedule and performance problems.

In his comments, the Deputy Administrator also noted that the Exploration Systems Mission Directorate is in the process of initiating a number of reforms to its project management policies and specified formulation dates in the coming months. He outlined these reforms and explained how they will allow NASA to address the recommendations in our report. We are encouraged by these planned changes. If properly implemented, they could be positive steps toward implementing a knowledge-based approach to project management.

The Deputy Administrator also requested that the relationship between JPL and NASA project management requirements be explicitly stated in the report. We moved the information from a footnote into the body of the report to clarify that relationship. We also addressed NASA’s technical comments as appropriate throughout the report.

Scope and Methodology

To determine whether NASA is establishing justification for the project and ensuring critical technologies are mature, we conducted interviews with NASA Exploration Systems Mission Directorate and Prometheus 1 project officials at NASA Headquarters, Washington, D.C.; Marshall Space Flight Center, Huntsville, Ala.; and the Jet Propulsion Laboratory, Pasadena, Calif. We obtained and reviewed pertinent documents from the agency. We conducted quantitative and qualitative analyses of project schedules, risk assessments, budget documentation, technology maturity assessments and technology development plans. We compared these documents to criteria established in JPL and NASA policies governing developmental programs and to criteria for a knowledge based approach to acquisition described in GAO’s best practices body of work. We discussed key project challenges with Prometheus 1 project officials, and conducted GAO team meetings to discuss analyses and developing issues. Our audit work was completed between April 2004 and January 2005.

As agreed with your office, unless you announce its contents earlier, we will not distribute this report further until 30 days from its issuance date. At that time, we will send copies to the NASA Administrator and interested congressional committees. We will make copies available to others upon request. In addition, the report will be available at no charge on the GAO web site at http://www.gao.gov.

If you or your staff have any questions concerning this report, please contact me at (202) 512-4841 or lia@gao.gov. Key contributors to this report are acknowledged in appendix IV.

Appendix I: Technology Readiness Levels Definitions

Lowest level of technology readiness. Scientific research begins to be translated into applied research and development. Examples might include paper studies of a technology’s basic properties.

None (Paper studies and analysis)

Invention begins. Once basic principles are observed, practical applications can be invented. The application is speculative and there is no proof or detailed analysis to support the assumption. Examples are still limited to paper studies.

None (Paper studies and analysis)

Active research and development is initiated. This includes analytical studies and laboratory studies to physically validate analytical predictions of separate elements of the technology. Examples include components that are not yet integrated or representative.

Analytical studies and demonstration of nonscale individual components (pieces of subsystem).

Basic technological components are integrated to establish that the pieces will work together. This is relatively “low fidelity” compared to the eventual system. Examples include integration of “ad hoc” hardware in a laboratory.

Low fidelity breadboard. Integration of nonscale components to show pieces will work together. Not fully functional or form or fit but representative of technically feasible approach suitable for flight articles.

Fidelity of breadboard technology increases significantly. The basic technological components are integrated with reasonably realistic supporting elements so that the technology can be tested in a simulated environment. Examples include “high fidelity” laboratory integration of components.

High fidelity breadboard. Functionally equivalent but not necessarily form and/or fit (size weight, materials, etc.). Should be approaching appropriate scale. May include integration of several components with reasonably realistic support elements/ subsystems to demonstrate functionality.

Lab demonstrating functionality but not form and fit. May include flight demonstrating breadboard in surrogate aircraft. Technology ready for detailed design studies.

Representative model or prototype system, which is well beyond the breadboard tested for TRL 5, is tested in a relevant environment. Represents a major step up in a technology’s demonstrated readiness. Examples include testing a prototype in a high fidelity laboratory environment or in simulated operational environment.

Prototype—Should be very close to form, fit and function. Probably includes the integration of many new components and realistic supporting elements/subsystems if needed to demonstrate full functionality of the subsystem.

High-fidelity lab demonstration or limited/restricted flight demonstration for a relevant environment. Integration of technology is well defined.

Prototype near or at planned operational system. Represents a major step up from TRL 6, requiring the demonstration of an actual system prototype in an operational environment, such as in an aircraft, vehicle or space. Examples include testing the prototype in a test bed aircraft.

Prototype. Should be form, fit and function integrated with other key supporting elements/subsystems to demonstrate full functionality of subsystem.

Flight demonstration in representative operational environment such as flying test bed or demonstrator aircraft. Technology is well substantiated with test data.

Technology has been proven to work in its final form and under expected conditions. In almost all cases, this TRL represents the end of true system development. Examples include developmental test and evaluation of the system in its intended weapon system to determine if it meets design specifications.

Actual application of the technology in its final form and under mission conditions, such as those encountered in operational test and evaluation. In almost all cases, this is the end of the last “bug fixing” aspects of true system development. Examples include using the system under operational mission conditions.

Appendix II: Prometheus 1 Critical Technologies

Nuclear Reactor

The nuclear reactor is the key element of the Prometheus 1 spacecraft. Without the power levels supplied by the reactor, the proposed propulsion, science, and communication systems are not feasible. Designing, constructing, and utilizing highly reliable, safe, portable nuclear reactors is not new—nuclear reactors have been used in submarines for almost 50 years. However, the United States has very little experience operating nuclear reactors in a space environment and tackling space unique nuclear application issues. The Office of Naval Reactors, the organizational unit in the Department of Energy responsible for developing nuclear reactors for the Navy, will be responsible for all portions of the Prometheus 1 reactor development effort.

The space environment places significant weight constraints on the reactor design and requires semi-autonomous control. Unlike submarines and aircraft carriers, all spacecraft have serious weight constraints driven by the cost of launching payloads into orbit. Consequently, spacecraft designers put great effort into eliminating weight. Further, where conventional reactors have hands on operators, the Prometheus 1 reactor must be remotely controlled. NASA estimates that control communications will take about 40 minutes to travel one way between Earth and the Jovian system.

Power Conversion

A power conversion system accepts the thermal energy from the reactor and converts it to useful electrical power for the spacecraft. Power conversion is an integral part of any power generation system taking the form of steam turbine generators in terrestrial utility plants and nuclear submarines. NASA is considering two types of power conversion systems—dynamic and static. According to NASA, the dynamic systems under consideration offer the benefits of increased efficiency, reduced weight and mass, and decreased nuclear fuel requirements. The static systems, however, have a technology heritage in prior spacecraft and could offer increased reliability because they have no moving parts.

Heat Rejection

Since the conversion process in a fission reactor is never 100 percent efficient, heat rejection is required to dissipate waste energy. This is usually accomplished with large pumped-water cooling systems on earth. Space based power conversion would require a large radiator system to dissipate the waste heat in the vacuum of space. The requirement to fold the large radiator system into the launch vehicle fairing and deploy it after launch complicates the radiator system design. (See fig. 1.)

Nuclear Electric Propulsion

Operating electric propulsion systems in space applications, including deep space, is not new. There is extensive experience with electric propulsion systems on satellites. In addition, NASA’s Deep Space 1 spacecraft was propelled using an electric propulsion ion thruster, similar in nature to the concept being developed for Prometheus 1. The thruster power levels required by Prometheus 1 have been demonstrated in a laboratory environment. The lifetime required by Prometheus 1, however, has not been demonstrated. Furthermore, lifetime testing of existing ion thrusters has demonstrated that these thrusters were approaching “wear out failure” after 30,352 hours. The Prometheus 1 thrusters will need to be qualified for operational durations approaching 120,000 hours. NASA recognizes that they will have to develop models and accelerated aging techniques to demonstrate the lifetime requirement.

Radiation Hardening

High Power Communications

The nuclear reactor will provide increased electrical power for communications. This translates to increased bandwidth and data rates. The high power communications system onboard the Prometheus 1 spacecraft, will provide tens of compact disks full of data back to earth. Analogous missions such as Cassini provide only a couple of floppy disks full of data. (A floppy disk typically holds about 1.44 MB of data. A compact disk typically holds about 700 MB of data.) According to project officials, the higher power communications system on the Prometheus 1 spacecraft will require upgrades to the Deep Space Network, which are out of the purview of the Prometheus 1 project.

Autonomous Rendezvous and Docking

There is no launch vehicle in the present or proposed U.S. inventory capable of launching the Prometheus 1 spacecraft, conceived for a mission to Jupiter’s Icy Moons, into orbit in one piece. The conceptual design currently shows the Prometheus 1 spacecraft to weigh between 29 and 36 metric tons and be about 58 meters in length. The current concept is to use multiple launches, 2 to 5, to place the spacecraft components in orbit and to use AR&D technology to assemble the spacecraft in orbit. Prometheus 1 is relying on NASA’s Demonstration Autonomous Rendezvous Technology and Hubble Robotic Servicing Mission, and the Defense Advanced Research Projects Agency’s Orbital Express programs for AR&D technology. These programs use different sensors and approaches to AR&D thereby providing Prometheus 1 with various options for consideration.

Appendix III: Comments from the National Aeronautics and Space Administration

Appendix IV: GAO Contact and Staff Acknowledgments

GAO Contact

Acknowledgments

In addition to the contact named above, James Morrison, Jerry Herley, John Warren, Tom Gordon, Ruthie Williamson, Karen Sloan and Sylvia Schatz made key contributions to this report.

GAO Related Products

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