Question

Which of the following is not used as a rocket fuel?
A. Synthetic rubber
B. Liquid hydrogen
C. Paraffin
D. Liquid nitrogen

Answer 1

Fuel can be defined as any solid, liquid or gas which upon burning gives us heat. Commonly used fuels in our homes are Liquified petroleum Gas or wood or kerosene oil. Now to send rockets into the space we need to overcome the gravitational pull of the earth. We know in order to escape from the earth, a body must be projected with a speed equal to or greater than escape velocity on the earth, which is 11.2 km/s.

Complete answer:
The liquid or gas, used as rocket fuels are highly combustible and must burn rapidly. Let us find out the properties of each of the options.Synthetic rubber burns rapidly and gives fumes of gases and hence it is one of the best rocket fuels. We know hydrogen is highly combustible, and it is used as a rocket fuel.

Paraffin wax is solid not a liquid and when it burns it does not give enormous amounts of heat in a short span of time and as such is not desirable at all to be used as a rocket fuel when compared with hydrogen and synthetic rubber. Liquid nitrogen is very difficult to store and to keep nitrogen in liquid state is a humongous task. Also, upon increasing the temperature there runs a risk of explosion and as such it does not qualify to be a rocket fuel at all.

So, the correct option is (D).

Note: Thus, we have seen that there are many constraints for any fluid to qualify as a rocket fuel. Once fuel starts burning, it does not stop until all is burnt out. It can’t be throttled as to control the thrust. Some common notable rocket fuel examples are Unsymmetrical Di-Methyl Hydrazine, which is being used by ISRO in its Chandrayan missions. Other cleaner fuels used are liquid methane and cryogenic propellants.