The development of test beds to support the definition and evolution of the Space Station Freedom power system

Since the beginning of the Space Station Freedom Program (SSFP), the Lewis Research Center (LeRC) and the Rocketdyne Division of Rockwell International have had extensive efforts underway to develop test beds to support the definition of the detailed electrical power system design. Because of the extensive redirections that have taken place in the Space Station Freedom Program in the past several years, the test bed effort was forced to accommodate a large number of changes. A short history of these program changes and their impact on the LeRC test beds is presented to understand how the current test bed configuration has evolved. The current test objectives and the development approach for the current DC Test Bed are discussed. A description of the test bed configuration, along with its power and controller hardware and its software components, is presented. Next, the uses of the test bed during the mature design and verification phase of SSFP are examined. Finally, the uses of the test bed in operation and evolution of the SSF are addressed

Nutrient Losses From Conventional and No-Till Cornfields

Farmers must be concerned about both the monetary loss and the threat of groundwater and surface water pollution associated with the loss of plant nutrients from their fields. There is also an increasing public concern about pollution and the role of agriculture in nonpoint-source pollution. Movement of water over the surface of the soil as well as through the soil profile increases the potential for loss of water-soluble nutrients, especially nitrates

Effects of Tillage and Grass Filter Strips on Surface Runoff of Water, Nitrate, Sediment, and Atrazine

The contamination of streams and other natural bodies of water through agricultural runoff has become a very important environmental issue. Surface water runoff can contain heavy loads of sediment and/or agricultural chemicals, such as nitrogen and atrazine. Conservation tillage methods with vegetative filter strips downslope from cropped fields help· to combat this problem. Conservation tillage has proven effective in decreasing erosion by decreasing exposure of the soil surface to rainfall. Vegetative filter strips provide an area where sediment and agricultural chemicals from cropland can be deposited before the runoff reaches a body of water

What Happened with No-Till in 1988

No-till (NT) received some bad publicity in 1988 in Kentucky and throughout the Midwest,especially during the early part of last summer\u27s drought. Some farmers found that corn yields were lower with NT than with conventional tillage (CT). However, others observed that the NT corn recovered faster and grew better than CT corn following the rains. Data from Kentucky and Nebraska tend to support this latter observation

Urease Inhibitor Reduces Ammonia Loss from Surface-Applied Urea

Urea is the world\u27s leading N fertilizer, and its use continues to grow. In the USA, for example, the use of urea increased 50 fold from 1955 to 1986. During that same time, its use in Kentucky increased from 214 to more than 112,000 tons per year, which was 28% of the N used in Kentucky in 1986. The increasing popularity of urea is due to advantages over other N fertilizers in its manufacture and to its use in making most N solutions, another rapidly growing form of N fertilizer. Desirable qualities of urea include the highest N content of all solid N fertilizers (45-46%), excellent handling properties, and dissolves readily in water. There is, however, a serious agromonic management problem with urea