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Wolf (Canis lupus) predation on livestock and management methods used to mitigate conflicts are highly controversial and scrutinized especially where wolf populations are recovering. Wolves are commonly removed from a local area in attempts to reduce further depredations, but the effectiveness of such management actions is poorly understood. We compared the effects of 3 management responses to livestock depredation by wolf packs in Montana, Idaho, and Wyoming: no removal, partial pack removal, and full pack removal. We examined the effectiveness of each management response in reducing further depredations using a conditional recurrent event model. From 1989 to 2008, we documented 967 depredations by 156 packs: 228 on sheep and 739 on cattle and other stock. Median time between recurrent depredations was 19 days following no removal (n = 593), 64 days following partial pack removal (n = 326), and 730 days following full pack removal (n = 48; recurring depredations were made by the next pack to occupy the territory). Compared to no removal, full pack removal reduced the occurrence of subsequent depredations by 79% (hazard ratio [HR] = 0.21, P

NASA’s modern vision for the manned exploration of Mars will require nuclear propulsion. Ongoing mission trade studies indicate that a combination of chemical propulsion, nuclear electric propulsion (NEP), and nuclear thermal propulsion (NTP) will most effectively meet those requirements. During the Apollo era of the 1960’s, NASA and the Atomic Energy Commission jointly conducted the NERVA program (Nuclear Engine for Rocket Vehicle Application). Aerojet was the prime contractor and, together with Westinghouse, developed a flight-like nuclear thermal rocket engine. The development concluded in 1971 with the successful completion of flight-like engine system tests conducted at the Nevada Test Site, ETS. One of the key development successes of the NERVA program was the demonstration of a high performance, low Net Positive Suction Pressure (NPSP) liquid hydrogen turbopump. An important aspect of the NERVA program was the validation of key system and component design tools, including the engine system analysis code, called the Common Digital Model (CDM), which was capable of both transient and steady-state analysis of NTP systems. This paper describes the capabilities of the analysis code, its applicability to other engine systems and the results of recent upgrades of the model to a modern computer format. It also describes the benefits of modernizing this validated code and applying it to support efforts stemming from NASA’s rekindled interest in NTP systems. The NERVA Common Digital Model is America’s only transient nuclear thermal engine simulation tool that has been anchored to actual hot-fire test data.