XECF nuclear rocket engine asembly, Nevada, USA, 1 December 1967.

Installation of the first ground experimental nuclear rocket engine (XE) asembly, in a 'cold flow' configuration, Nuclear Rocket Development Station, Nevada. The Experimental Engine Cold Flow (XECF) engine was part of a project whose objective was to develop a thermodynamic nuclear rocket engine. The US Atomic Energy Commision had initially wanted a nuclear engine for misile use. Cold flow experiments use an asembly identical to that used in power tests, but contain no fisionable material nor produce a nuclear reaction, so no fision power is generated. Nixon cut funding in response to a lack of public interest in human spaceflight, the end of the space race, and the use of robotic space probes.