1. By George Taktikos

2. Overview Process differs from conventional rocket engines Process differs from conventional rocket engines Uses nuclear reaction to heat propellant Uses nuclear reaction to heat propellant Useful for upper rocket stages Useful for upper rocket stages Able to attain higher transfer orbits faster Able to attain higher transfer orbits faster Critical for manned exploration of other planets Critical for manned exploration of other planets Higher specific impulse (Isp) Higher specific impulse (Isp) The higher the specific impulse, the less propellant is needed to gain a given amount of momentum. The higher the specific impulse, the less propellant is needed to gain a given amount of momentum.

3. Basic Design

4. Advantages Greater specific impulse (drastically increased thrust) Greater specific impulse (drastically increased thrust) Can carry a larger payload into space Can carry a larger payload into space Accomplish its missions in a reduced time span Accomplish its missions in a reduced time span Can attain higher transfer orbits Can attain higher transfer orbits Minimizes travel time to the destination Minimizes travel time to the destination Able to use propellants with low molecular weight Able to use propellants with low molecular weight Increases the propulsive force per unit propellant flow Increases the propulsive force per unit propellant flow Greater proportion of the total weight composed of the actual payload Greater proportion of the total weight composed of the actual payload

5. Disadvantages Radioactive Contamination Radioactive Contamination Fallout Fallout Contamination of wide areas Contamination of wide areas Expensive Expensive Nuclear fuel difficult to obtain Nuclear fuel difficult to obtain Engine design and manufacturing difficulties Engine design and manufacturing difficulties

6. Design Limitations Maximum Operating Temperature Maximum Operating Temperature Only limiting factor in thermal nuclear rocket propulsion is the melting point of the materials constituting the reactor. Only limiting factor in thermal nuclear rocket propulsion is the melting point of the materials constituting the reactor. Various design types attempt to mitigate this limitation to increase operating temperature and specific impuse Various design types attempt to mitigate this limitation to increase operating temperature and specific impuse

7. Types of Nuclear Rocket Motors Solid Core Solid Core Nuclear reactor running at high temperatures heats hydrogen moving through the reactor core. Nuclear reactor running at high temperatures heats hydrogen moving through the reactor core. Simplest design Simplest design Liquid Core Liquid Core Nuclear fuel mixed into hydrogen allowing the reaction to take place in the liquid mixture itself Nuclear fuel mixed into hydrogen allowing the reaction to take place in the liquid mixture itself Gas Core Gas Core Rapid circulation of the hydrogen to create a pocket of gaseous uranium fuel in the middle of the reactor, surrounded by hydrogen Rapid circulation of the hydrogen to create a pocket of gaseous uranium fuel in the middle of the reactor, surrounded by hydrogen

8. Solid Core Simple Design Simple Design Few moving parts, little to go wrong Few moving parts, little to go wrong Limited by maximum temperature of reactor stack Limited by maximum temperature of reactor stack 800 to 900 Isp 800 to 900 Isp

9. Liquid Core Complex Design Complex Design Difficult to maintain Difficult to maintain Much can go wrong Much can go wrong Higher thrust than solid core Higher thrust than solid core 1300 to 1500 Isp 1300 to 1500 Isp

10. Gas Core Allows for higher temperatures Allows for higher temperatures Nuclear fuel never touches chamber walls Nuclear fuel never touches chamber walls Significant loss of nuclear fuel Significant loss of nuclear fuel 3000 to 5000 Isp 3000 to 5000 Isp Nuclear light bulb design superior Nuclear light bulb design superior Limited only by melting point of quartz approx. 25,000°C Limited only by melting point of quartz approx. 25,000°C 1500-2000 Isp 1500-2000 Isp

11. Summary Shorter mission time Shorter mission time Reduces travel time to Mars by 2/3 Reduces travel time to Mars by 2/3 Makes manned space exploration feasible Makes manned space exploration feasible Less weight devoted to propellant Less weight devoted to propellant Greater payloads delivered into orbit Greater payloads delivered into orbit Lower operating costs Lower operating costs Less launches needed overall Less launches needed overall

12. Sources http://www.zamandayolculuk.com/cetinbal/H TMLdosya1/PropulsionChemical.htm http://www.zamandayolculuk.com/cetinbal/H TMLdosya1/PropulsionChemical.htm http://www.zamandayolculuk.com/cetinbal/H TMLdosya1/PropulsionChemical.htm http://www.zamandayolculuk.com/cetinbal/H TMLdosya1/PropulsionChemical.htm http://library.thinkquest.org/12145/propul5.ht m http://library.thinkquest.org/12145/propul5.ht m http://library.thinkquest.org/12145/propul5.ht m http://library.thinkquest.org/12145/propul5.ht m http://en.wikipedia.org/wiki/Nuclear_Thermal _Rocket http://en.wikipedia.org/wiki/Nuclear_Thermal _Rocket http://en.wikipedia.org/wiki/Nuclear_Thermal _Rocket http://en.wikipedia.org/wiki/Nuclear_Thermal _Rocket http://en.wikipedia.org/wiki/NERVA http://en.wikipedia.org/wiki/NERVA http://en.wikipedia.org/wiki/NERVA http://en.wikipedia.org/wiki/Specific_impulse http://en.wikipedia.org/wiki/Specific_impulse http://en.wikipedia.org/wiki/Specific_impulse