NASA Re-thinks Nuclear, Solar Routes

[ErnstBlofeld]

Aviation Week and Space Technology:

Novel nuclear and solar space propulsion concepts could receive long-awaited development opportunities as part of NASA’s evolving exploration road map.

Proponents of both technologies believe conventional chemical rockets are reaching their performance limits and that the requirement for faster transit times should drive the exploitation of more advanced systems. Although neither nuclear nor solar electric propulsion (SEP) concepts are new, recent developments mean variations of both could see realistic chances for “prime time” application for the first time as part of a human Mars mission, or other space transportation project.

Nuclear concepts are centered on two main fission-based methods: nuclear electric propulsion (NEP) and nuclear thermal propulsion (NTP). Both are suitable for unrestricted deep-space missions because of high thrust per unit mass of propellant consumed (specific impulse or ISP). For outer solar system exploration, where sunlight intensity is weaker, nuclear-based options are also capable of producing more power than SEP systems.

Nuclear electric propulsion takes heat from a reactor and converts it to electrical power, which then drives an ion or plasma thruster. In contrast, NTP uses reactor heat to drive propellant out of the engine in place of a chemical reaction. The electric option has higher ISP but produces tiny amounts of thrust, so must operate continuously for months or years; nuclear rockets have relatively lower ISP but much higher thrust.

Both nuclear electric and thermal concepts form part of NASA’s Enabling Technology Development and Demonstration (ETDD) study, which is identifying “game-changing” exploration technologies for eventual ground and flight-test experiments. The study has already identified high-power electric propulsion and fission-power systems as candidates for proposed initial demonstrations. In addition, nuclear thermal is identified as one of 10 “foundational technology domains” that should be developed to feed future demonstration projects.