[AIP SPACE TECHNOLOGY AND APPLICATIONS INTERNAT.FORUM-STAIF 2004: Conf.on Thermophys.in Microgravity; Commercial/Civil Next Gen.Space Transp.; 21st Symp.Space Nuclear Power & Propulsion; Human Space Explor.; Space Colonization; New Frontiers & Future Concepts - Albuquerque, New Mexico (USA) (8-11 February 2004)] AIP Conference Proceedings - Estimation of Specific Mass for Multimegawatt NEP Systems Based on Vapor Core Reactors with MHD Power Conversion