Rocket propulsion, Self assesments|2023 LATEST UPDATE|GUARANTEED SUCCESS

What is the reason for multi-staging compared to single stage rockets? 1. Higher payload ratio for same velocity increment 2. Higher attainable velocity for same payload ratio Which forces need to be taken into account to calculate a launch vehicles trajectory at lift-off? 1. Atmospheric drag force 2. Gravitational force 3. Thrust Force Why is the Hohmann transfer orbit considered most fuel efficient to go from Earth orbit to Mars orbit? Velocity increments are collinear to object trajectory The dimensioning factor for the combustion chamber length is related to 1. The size of the injected droplets 2. The vaporization process of the liquid drops Which of the following parameter changes will increases the wall heat flux per unit area? 1. Reduced molecular weight of the exhaust gas 2. Increased chamber pressure 3. Reduced throat diameter What is a correct statement concerning dissociation? 1. Dissociation is associated with a state of chemical equilibrium 2. Product dissociation shifts the maximum ISP to non-stoichiometric oxidizer-fuel mass ratios 3. Product dissociation usually occurs at high temperature levels Several propellants have theoretical exhaust velocities of over 3000 m/s. If the initial entalphy of the propellants is zero, what is the minimum amount of chemical energy that must be added to the propellant to attain this velocity? 45*10^5 J/kg Which of the following alternative will increase the vacuum specific impulse of a rocket nozzle? 1. Increased chamber temperature 2. Increased chamber pressure 3. Increased area ratio Which are the principle loss mechanisms that should be minimized when searching for an optimum nozzle configuration? 1. Divergency Loss 2. Viscous drag loss 3. Chemical kinetic loss What is required to achieve a constant thrust level for solid-propellant boosters? 1. The burning rate needs to remain constant 2. The burning charge area has to remain constant Metal powders are added to solid propellants to... 1. Increase the specific weight of the propellant 2. Increase the ISP 3. Increase the thrust A large pressure drop over the injector nozzle of a combustion chamber.. 1. Enables good atomization of the fuel 2. Increases the propellant inlet velocities Which of the following aspects are important for the dimensioning of rocket engine nozzles with respect to heat transfer? 1. Radiative heat transfer to the outside 2. Film cooling effectiveness 3. The conductivity of the wall material Why are the turbines typically supersonic in open cycles ? The turbine pressure ratio is higher Why is particularily the Oxygen pump turbine prone to be low in efficiency ? The turbine speed is limited by the pump What are the characteristics of turbines for stage combustion cycles ? 1. Extremely high power 2. The pressure levels are above 150 bar What properties are important for the turbopump design ? 1. The shaft speed limitation 2. The target combustion chamber pressure 3. The propellant densities Why is the turbine often of impulse type in liquid rocket propulsion ? 1. In order to reduce the stage count 2. The flow velocities are very high compared to mechanical limits Which of the following statement is correct regarding electrical propulsion? 1. Propulsion energy is only limited by the size of the power plant i.e. electrical rockets are power limited 2. In ion rockets, a separate electrical energy source is used to accelerate charged propellant particles in order to create thrust In what specific-impulse range operate arcjet propulsion devices most efficiently? 1000s to 2000s What are the main concepts for electrical propulsion? 1. Electrothermal 2. Electrostatic 3. Electromagnetic What are the main properties of electrical propulsion? 1. Low thrust level 2. High specific impulse 3. Low propellant mass consumption On what physical principle is the 'Basic Rocket Equation' based on? 1. Conservation of momentum 2. Newton's laws of motion-2nd law Which physical quantities determine the Total Impulse, I_tot (Ns) delivered by a propulsion system? Total mass of propellant expelled and its speed of expulsion Which of the following wall parameters are the most important in the design of the coolant channels to a regenerative cooled thrust chamber? 1. Wall thickness between hot and cold gas 2. Wall material thermal conductivity What is the main reason that the oxygen pump run at a slower speed than the hydrogen pump in an LH2/LO2 rocket engine ? The density is lower in the H2 pump