This set of Rocket Propulsion Interview Questions and Answers for Experienced people focuses on “Chemical Rocket Propellant – Analysis of Chamber or Motor Case Conditions”.
1. The heat created by the combustion in the thrust chamber of a chemical rocket engine equals the change in enthalpy of the gases.
Explanation: The heat generated during combustion of the propellants is the heat that is necessary to raise the resulting gases to their final temperature adiabatically. This follows from the conservation of energy.
2. If the energy balance in the chemical reaction within the thrust chamber is thought of as a two-step process, what is the initial step in the process?
a) Isothermal chemical reaction at the reference temperature
b) Isentropic chemical reaction at the reference temperature
c) Adiabatic chemical reaction at the reference temperature
d) Heating of gases with the energy release from the chemical reaction
Explanation: The energy balance can be thought of as a two-step process. The first step involved in the isothermal chemical reaction of the propellants at the reference temperature. The second step involves the resultant gases having their temperature raised by the heat released from the previous chemical reaction.
3. Out of the following products of the reaction of hydrogen and oxygen, which of them is unstable?
b) Hydrogen peroxide
Explanation: Theoretically, the reaction between hydrogen and oxygen can give rise to H2O2 and O3 too. But these are unstable materials and they do not readily exist at high temperatures.
4. Energy release efficiency is also called as ___________
a) isentropic efficiency
b) polytropic efficiency
c) propulsive efficiency
d) combustion efficiency
Explanation: Energy release efficiency is also called as combustion efficiency. It is the ratio of actual change in enthalpy of the unit propellant mixture to the theoretical change in enthalpy necessary to transform the propellants from the initial conditions to the products at the chamber pressure and temperature.
5. Combustion efficiency in liquid propellant rocket engines __________ with an increase in combustion temperature.
c) doesn’t change
Explanation: Combustion efficiency increases with increased combustion temperature. It is also depended on the method of injection and mixing.
6. What is the approximate number of species or compounds present in the exhaust for a solid propellant rocket engine?
Explanation: The number of compounds present in the exhaust for a solid propellant rocket engine or a liquid propellant rocket engine with additives can be 50 or more. But many of these chemical species are present in negligible amounts and can be ignored.
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