Editing Fission-fragment rocket (section)

===Rotating fuel reactor===
[[Image:Fission fragment propulsion.svg|thumb|right|Fission-fragment propulsion concept{{ordered list|type=lower-alpha|fissionable filaments arranged in disks|revolving shaft|reactor core|fragments exhaust}}]]

A design by the [[Idaho National Engineering Laboratory]] and [[Lawrence Livermore National Laboratory]]<ref>{{cite conference |last1= Chapline |first1=G. |last2=Dickson |first2=P. |last3=Schnitzler |first3=B. |url=http://www.osti.gov/bridge/servlets/purl/6868318/6868318.pdf |title=Fission fragment rockets: A potential breakthrough |conference=International reactor physics conference |location=Jackson Hole, Wyoming, USA |date=18 September 1988 |osti=6868318}}</ref>  uses fuel placed on the surface of a number of very thin [[carbon]] fibres, arranged radially in wheels. The wheels are normally sub-[[Critical mass (nuclear)|critical]]. Several such wheels were stacked on a common shaft to produce a single large cylinder. The entire cylinder was rotated so that some fibres were always in a reactor core where surrounding moderator made fibres go critical. The fission fragments at the surface of the fibres would break free and be channeled for thrust. The fibre then rotates out of the reaction zone to cool, avoiding melting.

The efficiency of the system is surprising; specific impulses of greater than 100,000&nbsp;s are possible using existing materials. This is high performance, although the weight of the reactor core and other elements would make the overall performance of the fission-fragment system lower. Nonetheless, the system provides the sort of performance levels that would make an interstellar precursor mission possible.