Glossary

H

Hall effect The development of a transverse electric field in a solid material when it carries an electric current and is placed in a magnetic field perpendicular to the current

heliosphere The region of the Sun's influence, including the Sun and the interplanetary medium

high-alpha High angle of attack

high-bypass engine A turbo-engine having a bypass ratio of more than four to one, the bypass ratio being the proportion of air that flows through the engine outside the inner case to that which flows inside that case

HIV Human immunodeficiency virus

HPCC High Performance Computing and Communications

HSCT High-Speed Civil Transport

HSR High-Speed Research (program)

HST Hubble Space Telescope

HT/MT Heavy Terminal/Medium Terminal (program)

hypersonic Faster than Mach 4; faster than "high speed"

hyper-spectral Having many very narrow frequency bands (1,000 or more), enabling a satellite to monitor specific sites instead of wide swaths