I will interpret "Nuclear Thermal Propulsion" to including LENR... 5 years would not be too bad for something not on the near horizon 1 year ago. Hopefully we can have a residential HVAC/Generator before that or at least something to heat our coffee.
http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=13354 -- radiation mitigation for human spaceflight; -- guidance, navigation, and control; -- optical systems; -- long-duration crew health; -- solar power generation; -- high-contrast imaging and spectroscopy technologies; -- environmental control and life support systems; -- electric propulsion; -- detectors and focal planes; -- instruments and sensors; -- fission power generation; -- lightweight and multifunctional materials and structures; -- nuclear thermal propulsion; -- entry, descent, and landing thermal protection systems; -- active thermal control of cryogenic systems; and
