Overview of the NASA MARIAH Project and summary of technical results

Abstract

During the period April 1995 to October 1997, the National Aeronautics and Space Administration (NASA) sponsored the Magnetohydrodynamics Accelerator for Research Into Advanced Hypersonics (MARIAH) Project. The objective of the project was to evaluate MHD as a driver technology for hypersonic ground test facilities. Test requirements developed in consultation with NASA specified that the technology should be capable of supporting near full-scale engine testing at dynamic pressures up to 2,000 lbf/ft2 and free stream Mach numbers up to 16. Test durations of tens of seconds to minutes were also specified. The near full-scale requirement implies large test section areas, large flow rates, and extremely high electric power. A technology evaluation included a review of past United States and Russian magnetohydrodynamics (MHD) technology development, detailed analysis and computational simulation of several configurations of MHD accelerators, and two major experimental efforts directed at measurement of electrical conductivity in seeded and unseeded high pressure air. One of the significant findings of the MARIAH Project is that MHD accelerators, which rely on thermal ionization of an alkali metal to achieve the requisite conductivity, have a restricted pressure-temperature range of operation. Pressures of at least 100 atm and temperatures of 2,500 K or higher are required for this mode of MHD channel operation, irrespective of seed material. This is due in part to constraints on entropy dictated by the targeted test section conditions. The minimum temperature requirement of 2,500 K is determined by electrical conductivity considerations. This temperature-pressure range is difficult to achieve using conventional arc heaters as primary drivers. Consequently, alternative nonequilibrium schemes for creating and sustaining the electrical conductivity were investigated. Unconventional drivers in the form of ultrahigh pressure (UHP) gas piston drivers were also evaluated. This paper discusses the major activities and technical findings, concluding with specific recommendations for future research.