Development of a Power Electronics Controller for the Advanced Stirling Radioisotope Generator

Under a U.S. Department of Energy program for radioisotope power systems, Lockheed Martin is developing an Engineering Unit of the Advanced Stirling Radioisotope Generator (ASRG). This is an advanced version of the previously reported SRG110 generator. The ASRG uses Advanced Stirling Convertors (ASCs) developed by Sunpower Incorporated under a NASA Research Announcement contract. The ASRG makes use of a Stirling controller based on power electronics that eliminates the tuning capacitors. The power electronics controller synchronizes dual-opposed convertors and maintains a fixed frequency operating point. The controller is single-fault tolerant and uses high-frequency pulse width modulation to create the sinusoidal currents that are nearly in phase with the piston velocity, eliminating the need for large series tuning capacitors. Sunpower supports this effort through an extension of their controller development intended for other applications. Glenn Research Center (GRC) supports this effort through system dynamic modeling, analysis and test support. The ASRG design arrived at a new baseline based on a system-level trade study and extensive feedback from mission planners on the necessity of single-fault tolerance. This paper presents the baseline design with an emphasis on the power electronics controller detailed design concept that will meet space mission requirements including single fault tolerance

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Control Electronics for Palm Power 35W Free-Piston Stirling Engine

(FPSE) with integral linear alternator, which was originally developed under a Phase II SBIR from NASA GRC, is the prime mover for this system. Due to the complexities associated with controlling a FPSE and the requirements of the Palm Power program for modulation, high efficiency, and low mass, a non-dissipative, efficient electronic control system is also being developed by Sunpower to convert the AC output voltage of the FPSE into 28Vdc for the Palm Power end user. Nomenclature P = average power pmean = mean gas pressure Xp = piston amplitude τ = acceptor to rejector temperature ratio T I

Intramolecular Exchange of Coordinated and Dangling Phosphine Groups in Pentacarbonyl[(diphenylphosphino)(di-p-tolylphosphino)methane]tungsten(0)

Equilibrium constants and rates have been determined for the isomerization of the linkage isomers (OC)5W[κ1-PPh2CH2P(p-tolyl)2] (5) and (OC)5W[κ1-P(p-tolyl)2CH2PPh2] (6). It is proposed that this intramolecular exchange involves a nucleophilic attack of the pendant phosphine on a cis carbonyl group, followed by ring opening and a 1,2-shift