Pulsed Nuclear Thermal Propulsion

The Terran Space Academy brings you up to date on the most exciting space propulsion technology in fifty years. Pulsed Nuclear Thermal Propulsion has the potential to open the entire solar system to rapid human exploration. This course will give you an in depth look at the concepts and technology.
I had promised you an update on the best current technology for space exploration. This course will cover a very exciting technology proposed by brilliant scientists at the Polytechnic University of Catalonia in Spain.
They have recommended using a pulsed nuclear reactor to dramatically increase the performance of a nuclear reactor for space exploration.
Let’s evaluate this idea closely. As you will remember from our course on advanced ion propulsion nuclear power is the only current answer to the high power needs of advanced propulsion systems. Since fusion is not ready at this time and may not be for a long time that means fission power. We have looked at radioisotope thermal generators or RTGs. These are great for backup power with no moving parts on many of them but are insufficient for our needs. We also examined nuclear reactors. An RTG is not adjustable, It puts out a certain amount of power, slowly decreasing, for a long time. A reactor is adjustable. You can increase and decrease the power output. The carbon absorbs the neutrons and slows reactions. This, with a cooling system, is how most reactors work. The neutrons usually only contribute about 5% to the heating of the propellant that is ran through the hot core. The propellant flow rate is limited by the pump speed and something called residence time. How long does the propellant have to be in the core to absorb enough heat to give a good engine efficiency. As we discussed the specific impulse of the best chemical rocket engine is about 455 seconds in vacuum. For the NERVA program while testing the Kiwi-B reactor we get a specific impulse of about 900 seconds. Twice the efficiency of a chemical rocket with good mass fuel flow producing significant thrust. Remember that the ion engines cannot process enough propellant fast enough to produce high thrust. In fact 5 to 40 Newtons is the best they can do with a specific impulse around 5000 and a power drain of at least 200 kW to produce this anemic thrust.
What makes the pulsed nuclear thermal or pulsed neutron thermal rocket engine so important? This type of engine revs the reactor up to a sudden burst of power releasing a flood of neutrons. These neutrons react with he nuclei in the propellant and almost instantly bring it to very high temperatures. In fact, this engine can make the propellant hotter than the core itself. How is this possible? Think of the neutrons as working like microwaves in an oven. The oven itself does not get that hot but the water in the food you are cooking absorbs the microwave radiation and heats up more than the oven. This works for the neutrons also. The kinetic energy of the high speed neutrons striking the nuclei of the propellant transfers this kinetic energy from the neutrons to the propellant causing a type of flash heating. This takes a few thousands of a second rather than several seconds. The pulses can also come very frequently. Up to 10,000 pulses per second is possible. If our pump is strong enough and our residence time is only say 1/100th of a second we can get a huge mass propellant flow with extreme heat producing a specific impulse of up to 5000 with massive thrust. This could be the best of both worlds, high efficiency with high thrust. Much better than any chemical or ion engine could ever hope to achieve. What could we do with this kind of power, efficiency and thrust? Let’s build that awesome space ship we always wanted.
If we take the mass of a SpaceX Starship as about 100 tons with 80 tons of fuel and apply it to our theoretical pulse nuclear thermal engine we get a delta v of 80km per second. That will let us get up to Earth escape velocity burning only 20.5 % of our fuel assuming 11.5 km/s delta v to launch from the Earth and reach escape velocity. This leaves us with almost 80% of our fuel and a deltaV reserve of 68.5 km/s. We could go to Mars, land on Mars, launch from Mars, come back from Mars and land back on the Earth using a total of about 34km/s. Now this is a spaceship. Going to the Moon only takes a delta V of about 15.07 km/s. There and back would therefore be about 30.14 km/s.
There is nothing short of a fusion drive that can match the potential of this technology...
Gratitude to the Polytechnic University of Catalonia, Spain and Professor Francisco J. Arias for this excellent idea.

Видео Pulsed Nuclear Thermal Propulsion канала Terran Space Academy