Engineering topics

Doherty, Michael P.

Publications and source records attributed to Doherty, Michael P..

31 records · Page 2

NASA NTRS1993

NEP Early Flight program: System performance and development considerations

A mission/system study of Nuclear Electric Propulsion (NEP) for early robotic planetary science mission applications has been conducted. Subject missions considered included a Mars orbiter with a Phobos and Deimos Rendezvous; a Comet Kopff Rendezvous; a Multiple Mainbelt Asteroid Rendezvous (MMBAR); an Asteroid (Vesta) Sample Return; a Trojan Asteroid (Odysseus) Rendezvous; and a Jupiter mini Grand Tour. The purpose of the study was to determine if 'near-term' NEP technology could be used on an early NEP flight to demonstrate the technologies while conducting a useful science mission. The analysis shows that, depending upon technology readiness date, the missions could be performed with low power NEP. The technology and system development costs associated with vehicle/stage development for a candidate mission are presented. The study assumed relatively mature space electric power and space electric propulsion technologies (more advanced technologies have been already shown by others to be enabling for many outer planetary missions). Thus, a very important first step in using NEP would be taken, which would contribute valuable solar system science, as well as reduce the risks associated with using NEP for more demanding outer planetary science mission applications.

Doherty, Michael P.↗

NASA NTRS1993

Utilization of recently developed codes for high power Brayton and Rankine cycle power systems

Two recently developed FORTRAN computer codes for high power Brayton and Rankine thermodynamic cycle analysis for space power applications are presented. The codes were written in support of an effort to develop a series of subsystem models for multimegawatt Nuclear Electric Propulsion, but their use is not limited just to nuclear heat sources or to electric propulsion. Code development background, a description of the codes, some sample input/output from one of the codes, and state future plans/implications for the use of these codes by NASA's Lewis Research Center are provided.

Doherty, Michael P.↗

NASA NTRS1993

NASA's progress in nuclear electric propulsion technology

The National Aeronautics and Space Administration (NASA) has established a requirement for Nuclear Electric Propulsion (NEP) technology for robotic planetary science mission applications with potential future evolution to systems for piloted Mars vehicles. To advance the readiness of NEP for these challenging missions, a near-term flight demonstration on a meaningful robotic science mission is very desirable. The requirements for both near-term and outer planet science missions are briefly reviewed, and the near-term baseline system established under a recent study jointly conducted by the Lewis Research Center (LeRC) and the Jet Propulsion Laboratory (JPL) is described. Technology issues are identified where work is needed to establish the technology for the baseline system, and technology opportunities which could provide improvement beyond baseline capabilities are discussed. Finally, the plan to develop this promising technology is presented and discussed.

Stone, James R.↗

NASA NTRS1993

NASA's progress in nuclear electric propulsion technology

Stone, James R.↗

NASA NTRS1993

Nuclear electric propulsion for planetary science missions: NASA technology program planning

This paper presents the status of technology program planning to develop those Nuclear Electric Propulsion technologies needed to meet the advanced propulsion system requirements for planetary science missions in the next century. The technology program planning is based upon technologies with significant development heritage: ion electric propulsion and the SP-100 space nuclear power technologies. Detailed plans are presented for the required ion electric propulsion technology development and demonstration. Closer coordination between space nuclear power and space electric propulsion technology programs is a necessity as technology plans are being further refined in light of NEP concept definition and possible early NEP flight activities.

Doherty, Michael P.↗

NASA NTRS1993

Summary and recommendations on nuclear electric propulsion technology for the space exploration initiative

A project in Nuclear Electric Propulsion (NEP) technology is being established to develop the NEP technologies needed for advanced propulsion systems. A paced approach has been suggested which calls for progressive development of NEP component and subsystem level technologies. This approach will lead to major facility testing to achieve TRL-5 for megawatt NEP for SEI mission applications. This approach is designed to validate NEP power and propulsion technologies from kilowatt class to megawatt class ratings. Such a paced approach would have the benefit of achieving the development, testing, and flight of NEP systems in an evolutionary manner. This approach may also have the additional benefit of synergistic application with SEI extraterrestrial surface nuclear power applications.

Doherty, Michael P.↗

NASA NTRS1993

Nuclear electric propulsion systems overview

The topics are presented in viewgraph form and include the following: nuclear propulsion background; schedule for the nuclear electric propulsion (NEP) project; NEP for the Space Exploration Initiative; NEP on-going systems tasks; 20KWe mission/system study; and agenda.

Doherty, Michael P.↗

NASA NTRS1992

NEP systems engineering efforts in FY-92: Plans and status

A system engineering effort has been initiated by NASA in FY-92 to define, address, and resolve issues associated with the use of Nuclear Electric Propulsion (NEP) for megawatt (MW) space propulsion applications associated with the Space Exploration Initiative (SEI). It is intended that key technical issues will be addressed by activities conducted in the early years of a project in NEP, with the objective of resolving such issues. Also, in response to more recent programmatic direction, a concept definition activity for 100 kilowatt NEP is being initiated. This paper will present key issues associated with megawatt NEP, and the plans and status for their resolution, and present the scope and rationale for the 100 kilowatt concept definition activity.

Doherty, Michael P.↗

NASA NTRS1992

Nuclear Electric Propulsion Technology Panel findings and recommendations

Summarized are the findings and recommendations of a triagency (NASA/DOE/DOD) panel on Nuclear Electric Propulsion (NEP) Technology. NEP has been identified as a candidate nuclear propulsion technology for exploration of the Moon and Mars as part of the Space Exploration Initiative (SEI). The findings are stated in areas of system and subsystem considerations, technology readiness, and ground test facilities. Recommendations made by the panel are summarized concerning: (1) existing space nuclear power and propulsion programs, and (2) the proposed multiagency NEP technology development program.

Doherty, Michael P.↗

NASA NTRS1992

Blazing the trailway: Nuclear electric propulsion and its technology program plans

An overview is given of the plans for a program in nuclear electric propulsion (NEP) technology for space applications being considered by NASA, DOE, and DOD. Possible missions using NEP are examined, and NEP technology plans are addressed regarding concept development, systems engineering, nuclear fuels, power conversion, thermal management, power management and distribution, electric thrusters, facilities, and issues related to safety and environment. The programmatic characteristics are considered.

Doherty, Michael P.↗

NASA NTRS1992

NASA/DOE/DOD nuclear propulsion technology planning: Summary of FY 1991 interagency panel results

Interagency (NASA/DOE/DOD) technical panels worked in 1991 to evaluate critical nuclear propulsion issues, compare nuclear propulsion concepts for a manned Mars mission on a consistent basis, and to continue planning a technology development project for the Space Exploration Initiative (SEI). Panels were formed to address mission analysis, nuclear facilities, safety policy, nuclear fuels and materials, nuclear electric propulsion technology, and nuclear thermal propulsion technology. A summary of the results and recommendations of the panels is presented.

Clark, John S.↗

NASA NTRS1991

Blazing the trailway - Nuclear electric propulsion and its technology program plans

An overview is given of the plans for a program in nuclear electric propulsion (NEP) technology for outer space applications being considered by NASA, DOE, and DOD. Possible missions using NEP are examined, and NEP technology plans are addressed regarding concept development, systems engineering, nuclear fuels, power conversion, thermal management, power management and distribution, electric thrusters, facilities, and issues related to safety and environment. The programmatic characteristics are considered.

Doherty, Michael P.↗

NASA NTRS1990

Finite element analysis of thermal distortion effects on optical performance of solar dynamic concentrator for Space Station Freedom

An analysis was performed to predict the thermal distortion of the solar dynamic concentrator for Space Station Freedom in low earth orbit and to evaluate the effects of that thermal distortion on concentrator on-orbit performance. The analysis required substructural finite element modeling of critical concentrator structural subsystems, structural finite element modeling of the concentrator, mapping of thermal loading onto the structural finite element model, and the creation of specialized postprocessors to assist in interpreting results. Concentrator temperature distributions and thermally induced displacements and slope errors and the resulting receiver flux distribution profiles are discussed. Results determined for a typical orbit indicate that concentrator facet rotations are less than 0.2 mrad and that the change in facet radius due to thermal flattening is less than 5 percent. The predicted power loss due to thermal distortion effects is less than 0.3 percent. As a consequence the thermal distortions of the solar dynamic concentrator in low earth orbit will have a negligible effect on the flux distribution profiles within the receiver.

Doherty, Michael P.↗