A 10,000-hr life test of an engineering model resistojet

One of the major issues associated with using resistojet thrusters on Space Station Freedom is the long life required. An engineering model resistojet was life-tested to determine if it was capable of meeting that requirement. This thruster, which was designed for 10,000 hr of operation at 2552.4 F (1400 C) or less under cyclical thermal conditions, successfully operated for 10,036 hr at 1836 F (1002 C) while undergoing 141 thermal cycles

Concentrator of laser energy for thin vapour cloud production near a surface

A novel scheme is presented for production of a thin ($<1$ mm) uniform vapor layer over a large surface area ($>100$ cm$^2$) by pulsed laser ablation of a solid surface. Instead of dispersing the laser energy uniformly over the surface, a modified Fabry-Perot interferometer is employed to concentrate the laser energy in very narrow closely-spaced concentric rings. This approach may be optimized to minimum total laser energy for the desired vapor density. Furthermore, since the vapor is produced from a small fraction of the total surface area, the local ablation depth is large, which minimized the fraction of surface contamination in the vapor. Key words: laser evaporation, thin gas layer formation.Comment: 8 pages, 2 figure

Data Mining the SDSS SkyServer Database

An earlier paper (Szalay et. al. "Designing and Mining MultiTerabyte Astronomy Archives: The Sloan Digital Sky Survey," ACM SIGMOD 2000) described the Sloan Digital Sky Survey's (SDSS) data management needs by defining twenty database queries and twelve data visualization tasks that a good data management system should support. We built a database and interfaces to support both the query load and also a website for ad-hoc access. This paper reports on the database design, describes the data loading pipeline, and reports on the query implementation and performance. The queries typically translated to a single SQL statement. Most queries run in less than 20 seconds, allowing scientists to interactively explore the database. This paper is an in-depth tour of those queries. Readers should first have studied the companion overview paper Szalay et. al. "The SDSS SkyServer, Public Access to the Sloan Digital Sky Server Data" ACM SIGMOND 2002.Comment: 40 pages, Original source is at http://research.microsoft.com/~gray/Papers/MSR_TR_O2_01_20_queries.do