The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) are studying how samples might be brought back to Earth from Mars safely. Backward planetary protection is key in this complex endeavour, as it is required to prevent potential adverse effects from returning materials to Earth's biosphere. As the question of whether or not life exists on Mars today or whether it ever did in the past is still unanswered, the effort to return samples from Mars is expected to be categorized as a ‘Restricted Earth Return’ mission, for which NASA policy requires the containment of any unsterilized material returned to Earth. NASA is investigating several solutions to contain Mars samples and sterilize any uncontained Martian particles. This effort has significant implications for both NASA's scientific mission, and the Earth's environment; and so special care and vigilance are needed in planning and execution in order to assure acceptance of safety to Earth's biosphere. To generate a technically acceptable sterilization process across a wide array of scientific and other stakeholders, on 30–31 January 2019, 10–11 June 2019 and 19–20 February 2020, NASA informally convened a Sterilization Working Group (SWG) composed of experts from industry, academia and government to assess methods for sterilization and inactivation, to identify future work needed to verify these methods against biological challenges, and to determine their feasibility for implementation on robotic spacecraft in deep space. The goals of the SWG were: (1)Understand what it means to sterilize and/or inactivate Martian materials and how that understanding can be applied to the Mars Sample Return (MSR) mission.(2)Assess methods for sterilization and inactivation, and identify future work needed to verify these methods.(3)Provide an effective plan for communicating with other agencies and the public.This paper provides a summary of the discussions and conclusions of the SWG over these three workshops. It reflects a consensus position based on qualitative discussion of how agencies might approach the problem of sterilization of Mars material. The SWG reached a consensus that sterilization options can be considered on the basis of biology as we know it, and that sterilization modalities that are effective on terrestrial materials and organisms should be part of the MSR planetary protection strategy. Conclusions pointed to several industry standards for sterilization to include heat, chemical, UV radiation and low-heat plasma. Technical trade-offs for each sterilization modality were discussed while simultaneously considering the engineering challenges and limitations for spaceflight. Future work includes more in-depth discussions on technical trade-offs of sterilization modalities, identifying and testing Earth analogue challenge organisms and proteinaceous molecules against chosen modalities, and executing collaborative agreements between NASA and external working group partners to help close data gaps, and to establish strong, scientifically grounded sterilization and inactivation standards for MSR.

Multiple metal alloys, that is, Ti‐6Al‐4 V, 316 L stainless steel, MS1 maraging steel, A2 tool steel, Inconel 625 with TiC and TiB2 reinforcement, and AMZ4 bulk metallic glass, were additively manufactured through laser powder bed fusion and tested as potential excavating tools for future robotic spacecraft landing on icy planetary bodies. Mechanical specific energy as a function of blade hardness was measured for each excavating tool as it trenched through soft and hard salt, where the salt is a regolith simulant for extraterrestrial ice. A2 tool steel, MS1 maraging steel, and bulk metallic glass cutting tools were shown to perform well in the experiments. A method for using the cutting tool as a sensor was also demonstrated.

This article discusses the experience of the US Navy with Synchro-Self-Shifting (SSS) clutches. The US Navy has nearly 40 years of experience using SSS clutches in main reduction gears of gas-turbine-driven ships and propulsion systems with combinations of gas turbines and diesel engines or electric motors, and in steam-turbine propulsion plants for use with electric motor drives. Over 900 SSS clutches have been installed in 14 different classes of US Navy ships, with some having been in service for over 30 years. SSS clutches have accumulated approximately 15,278,000 hours of operation. Mean Time Between Failures in Hours for US Navy clutch applications is relatively high (271,550 hours) based on the operational hours accumulated and the total number of failures that have occurred. The maintenance and repair strategy used for US Navy SSS clutches is similar to a Performance Based Logistics arrangement, where the Navy maintains a rotatable pool of ready-for-issue clutches, and in the event of a problem or failure, the clutch is changed out with an available spare.

This paper will describe how a generator of a peak load turbine, when operated as a synchronous condenser, can help improve electrical system power factor and therefore help maintain reactive power balances between sources of generation and demand points. It is particularly appropriate to use peak load plant with either industrial or aero-derivative gas turbines for synchronous condensing. By using a clutch to disconnect the turbine from the generator, losses from the turbine are avoided enabling more efficient synchronous condensing operation. Details of specific clutch designs for turbine generator synchronous condenser applications and experience at various B.C. Hydro installations are provided.

The Synchro-Self-Shifting (SSS) overrunning clutch is well known, particularly in the Naval Marine field. This paper reviews the clutch operating principle, then outlines some of the service experience since 1962, particularly in naval main propulsion drives beginning with CODOG, CODAG, COGOG and COGAG plant, and then the experience with more recent applications such as combined electric motor propulsion with either gas turbines or diesel engines and hybrid electric plants. Extra features are then described such as a lock-out control as is usually necessary for turbine applications to permit turbine testing, e.g., when in harbor; also a lock-in control as is essential when the clutch has to transmit power in both directions of rotation. Various clutch mounting arrangements will be presented with respective advantages. The paper concludes with information regarding reliability during many years of service experience.