In fission propulsion, fission reaction is used to generate energy. This energy is used to heat the propellants forming gaseous products. The gases are forced out through a nozzle, thus producing thrust.
Keeping this principle in mind, we will see how fission propulsion is used to generate thrust.
As said earlier, in fission propulsion, fission reaction is used to generate energy. Now, what is nuclear fission reaction?
Nuclear fission is a type of nuclear reaction in which heavy atoms like U-135 (heavier than iron) is split into number of fragments of much smaller mass, by bombardment with suitable sub-atomic particles. This results in liberation of huge amounts of energy.
Now, when we add the actual masses of reactants and products, we will find that mass of reactants is greater than the mass of products.
This difference in the masses, called mass defect, is converted to energy according to mass energy equivalence relation i.e.
E = mc2
E = amount of energy.
m = mass.
c = velocity of light.
Consider the reaction,
92U235 + 0n1 ® 56Ba19 + 36Kr114 + 2 0n1
One U atom can liberate 208MeV, which is a very large value. It is sufficient to boil any rocket propellant.
Thus, the application of nuclear fission reaction in propulsion is called fission propulsion technique. Let us see how fission reaction could be implemented for propelling the rockets.