Correct Answer : Turbopump
Explanation : Turbopump is an arrangement with a turbine and one or more pumps. An alternative to turbopump would be the gas pressure feed system. Both of them have varying applications and are employed depending upon the scenario under consideration, e.g. a long-duration mission to the outer space or a missile within the earth’s atmosphere.
Correct Answer : inducer
Explanation : Inducer can be thought of as a special impeller where the pressure of the propellant is raised by a small amount, typically 5-10% of the total pressure rise. The propellants enter through this inducer to reach the impeller.
Correct Answer : increase the pressure of flowing propellant
Explanation : A turbopump helps in the increase of pressure of the flowing propellants. To initiate the flow of propellants from their storage tanks to the combustion chamber, the propellants must traverse a path of favorable pressure gradient.
Correct Answer : Maximum shaft speed
Explanation : Maximum shaft speed is a key pump parameter. It is restricted by the need to avoid excessive cavitation.
Correct Answer : higher
Explaination : Pump head refers to the difference between discharge and suction head of the pump. It is measured in meters or feet. It is much higher for the lower density propellant if the propellant combination used in an engine has a noticeable difference in their densities.
Correct Answer : equal to; equal to
Explaination : Mass flow rate remains constant. Hence the total propellant flow will be the same for the pump outlet as well as in the combustion chamber. Favorable pressure difference should be present for the flow to take place. The chamber pressure will be different from the nozzle pressure, but the discharge pressure is kept to be the same as the chamber pressure.
Correct Answer : Higher efficiency and lower mass
Explanation : From the design perspective, the reliability of a turbopump with higher efficiency and lower mass will be low. The reason is that by selecting such stringent criteria for efficiency and mass acts as restricted design margins.
Correct Answer : hydrostatic pressure
Explanation : It is converted to hydrostatic pressure in the diffuser. Part of this conversion will also take place in the volute.
Correct Answer : part of the propellant flow
Explanation : Parts of the propellant flow is used for cooling of bearings and shaft seals. The heat absorbed by the propellants make it more energetic which can be later used during the combustion and expansion processes in the thrust chamber.
Correct Answer : higher; higher
Explanation : Because of the gear system, the two-stage turbine speed is higher than the shaft speed of the pumps and turbine is smaller. It will lead to higher turbine efficiency and higher pump efficiency.
Correct Answer : 3706 m/s
Explaination : Payload ratio λ = 1000/(15000 – 1000) = 0.0714.?V = Ueqln((1+λ)/(ε+λ))= 3000 x ln(1.0714/0.3114)= 3706 m/s.
Correct Answer : r = λ + δ
Explaination : Inert mass fraction is given by the formula δ = min/mo, where min denotes inert mass and mo denotes initial mass of the rocket. Payload mass fraction is λ = mpl/mo, where mpl is the payload mass. Parametric mass ratio is the sum of both the above ratios.
Correct Answer : nozzle area ratio and chamber pressure
Explanation : In addition to the influence of nozzle area ratio and chamber pressure, the overall engine specific impulse also depends on the engine cycle and mixture ratio on a lesser extent.
Correct Answer : ZPP
Explanation : ZPP is Zirconium Potassium Perchlorate. It is one of the most common initiators and called NASA Standard Initiator. ZHPP is a metal hydride-oxidizer, HMTD is a highly explosive organic compound and Nickel-aluminum laminates are used in electrically initiated pyrotechnic igniters.
Correct Answer : spark igniter
Explanation : Pyrotechnic igniter and pyrotechnic initiator are same. Spark igniter is capable of multiple restarts while the other two – hypergolic and pyrotechnic igniters are single use ignition systems.
Correct Answer : Japan
Explanation : LE-5A and its derivatives were designed by Japan. It was designed to meet the upper stage requirements of H-I and H-II series of launch vehicles.
Correct Answer : 4-7
Explanation : All of the engines use LOX and LH propellants. Mixture ratio for SSME, RS-68, LE-5A and Vulcan are 6, 6, 5, 6 and 5.35 respectively.
Correct Answer : 400-500 s
Explanation : Major LOX and LH propellant engines like SSME, RS68 and LE-5A produce specific impulses of 452.5s, 415s and 452s respectively. All of such engines are capable of producing specific impulse values above 400s.
Correct Answer : Vulcain
Explanation : Ariane 5 uses Vulcain engine. The engine makes use of a gas generator cycle. RS-68 (Rocket System 68) was used in the first stage of the Delta IV rocket. HM7 was used as an upper stage engine in Ariane 1. RL 10-B2 was used in Delta 3 and Delta IV launch vehicles.
Correct Answer : Long March
Explanation : YF 73 was used by the Long March vehicle. LE-5A and LE-7 were used in HII and SSME was used for Space Shuttle.
Correct Answer : 2-10% of the total load
Explaination : 2-10% of the total load is used for contingency. Total load Is the sum of propellant amount used for main thrust chamber, flight control function and mission margin. Contingency amount of propellant is reserved for a possible scenario that cannot be predicted with certainty.
Correct Answer : 0.25-1% of the total load
Explaination : Allowance for off-nominal performance is 0.5-1% of the total load. But allowance for of-nominal operations is 0.25-1% of the total load.
Correct Answer : Filling more propellant than needed into a tank
Explanation : Incorrect filling of propellant into the tank than needed, adjusting regulators or control valves, etc. falls under the category of operational factors. For a carefully calibrated and tested engine, this factor is usually small, ranging from 0.1 to 1%.
Correct Answer : Extra propellant to be used to allow for mixture ratio variations
Explanation : Extra propellant needs to be tanked for allowing mixture ratio variations. It can even be as high as 2% of one of the propellants.
Correct Answer : Off-nominal performance
Explanation : Off-nominal performance is due to variations in hardware manufacturing and it varies from one engine to another. It can occur due to slightly different losses in a cooling jacket, in injectors and valves or due to different pump characteristics.
Correct Answer : 0.5-2% of the total load
Explaination : 0.5-2% of the total propellant load is that of the residual propellant. At the period of thrust termination, it increases the vehicle mass and slightly reduces the flight vehicle velocity.
Correct Answer : 0.1 to 4%
Explaination : The amount of propellants required in this scenario is determined from the mission requirements and the TVC duty cycle. The amount of propellants required may range from 0.1 to 4% of the total propellant.
Correct Answer : 70-90%
Explaination : Main thrust chamber uses the propellants in increasing the velocity of a stage or a vehicle. It is the most important constituent of propellant budget. Its contribution ranges from 70-90%. It is determined from mission analysis and system engineering.
Correct Answer : Reuse of a decommissioned engine
Explanation : Reuse of a decommissioned engine isn’t part of the degree of novelty. It doesn’t involve any new design procedure and it is not recommended.
Correct Answer : Power balance
Explanation : A power balance is a simulation of the steady-state, internal conditions and functioning of an engine. It may require varying levels of complexity to model a power balance, ranging from the use of a simple spreadsheet to the use of complicated computer programs.
Correct Answer : Engine balance program
Explanation : Engine balance program balances the pressure drops in oxidizer and fuel. It also balances pressurizing gas flow systems. It is a kind of computer program that specifically operates on a particular engine cycle.
Correct Answer : Optimization studies
Explanation : Optimization studies lead to small improvements in vehicle performance. This process is sometimes completed even before identifying a suitable engine.
Correct Answer : Mission duration
Explanation : Chamber pressure, nozzle area ratio, thrust, mixture ratio etc are optimized in the optimization studies. It results in small improvements in propellant fraction, engine volume, cost and vehicle performance.
Correct Answer : Preliminary engine performance estimates
Explanation : Preliminary engine performance estimates involves obtaining data from existing similar models. When they are not readily available, then theoretical performance values calculated by incorporating correction factors, experimentation or simulation methods are adapted.
Correct Answer : Full-fledged simulations
Explanation : Since the decisions to be made are tentative, a full-fledged simulation will most likely result in a waste of time and resources. Making logical decisions backed by mission requirements, customer preferences and past experiences is more sensible approach.
Correct Answer : Consultancy experts
Explanation : Experts from the fields of manufacturing, stress analysis, field service and safety are important in making appropriate decisions on behalf of the rocket engine design.
Correct Answer : Both Inert mass and center of gravity
Explanation : Both inert mass of the engine and other mass properties like center of gravity or moment of inertia are key parameters to the customer as well as the vehicle designer. They are used both in the preliminary and final design.
Correct Answer : development; testing new components and engines
Explanation : The engine selection decisions are validated in the development stage. In the development stage, new components and new engines are tested.
Correct Answer : 3-15 ms
Explanation : It takes about 3-15 ms for starting small thrusters with a pressurized feed system. For a turbopump-fed system, this time can be about 1-5 s.
Correct Answer : Turbopump system
Explanation : For the same kind of rocket engine, turbopump system will require more time to start. This is because of an additional time delay involved in such systems for starting the gas generator or preburner and for bringing the turbopumps up to speed.
Correct Answer : raise chamber pressure
Explanation : Start delay is the time required to do a number of operations. This involves the time to purge the system if required, open valves, initiate combustion, and raise the flow and chamber pressure to their rated values.
Correct Answer : Liquid flow system in general are inherently stable
Explanation : The liquid flow systems used in liquid propellant rocket engines are inherently stable. This means that when there is a disturbance in the hydraulic system (like a sudden increase or decrease of flow), the system tries to reduce the effect of disturbance on its own.
Correct Answer : Checkout controls
Explanation : In some rocket engines, there are provisions for actuation of principal valves without having propellant or pressure in the system. Check-out controls enables such a provision to be executed.
Correct Answer : mission
Explanation : The mission determines how complex the engine system will be. If the mission is to reach Mars and deploy a rover, the level of complexity involved will be more compared to a mission to launch a rocket to intercept a missile above the atmosphere.
Correct Answer : devices which are deployed only once
Explanation : Single-shot devices are those which are deployed once. An example would be Rocketdyne’s X-1.
Correct Answer : liquid rocket engines
Explanation : Valves, regulators and pressure switches are required for controlling and regulating the flow of liquid propellants in rocket engines which use them. The use of such equipment adds to the complexity of liquid propellant rocket engines compared to other types.
Correct Answer : Safety controls
Explanation : Safety controls are maintained in a rocket with the special intention of protecting personnel and equipment in case of its malfunction. When a situation arises where we need to choose as to give weightage to safety or improve the performance and efficiency of a device, the preference will always be towards safety.
Correct Answer : Nonhazardous shutdown
Explanation : A failure in electrical power supply may lead to a nonhazardous shutdown in a rocket. In such a case, all the electrical valves return to their normal configuration.
Correct Answer : complex
Explaination : The use of an automatic feedback system employing a digital computer is complex compared to static calibration. The error in static calibration indicates a deviation from a linear response of the system. Dynamic measurements may incur appreciable errors because of the nonlinear response.
Correct Answer : regulated pressure
Explanation : The gas pressure in the propellant tank is regulated pressure Pgas. It is diminished by the pressure losses in the gas line denoted by ?Pgas. This gas pressure is augmented by the static head of the liquid.
Correct Answer : regulator
Explanation : The pressurizing gases first passes through a regulator for pressurization of both the fuel and the oxidizer. Regulators in general, can be used for both liquid and gases and may contain its own restrictor or pressure sensor.
Correct Answer : more
Explanation : The calibration curves cannot be estimated readily without the use of good test data. Hence the calibration procedure for turbopump is more complex.
Correct Answer : pressure balance
Explanation : Pressure balance is the term used for denoting the balancing process. The pressure is supplied to the engine by pumps or pressurized tanks. This is an important part of engine calibration for it to operate at desired flow rate and mixture ratios.
Correct Answer : Thrust load
Explanation : Thrust load is the most significant. The vehicle structure must be able to withstand this load for its successful operation. It is also called axial load and acts parallel to the vehicle’s longitudinal axis. With variable thrusters, this direction can also be manipulated.
Correct Answer : fuel-rich
Explanation : Operating mixture ratio is usually fuel-rich and the value is determined by optimum specific impulse. This is done because fuel-rich mixtures typically have lower molecular weight. It might also help in afterburning which can improve the overall rocket performance.
Correct Answer : Equal to
Explanation : The ratio of rated flows should be equal to the desired mixture ratio under ideal operating conditions. Ratio of the rated flows is given by m?o/m?f. One way of doing this is to add pressure drops with appropriately placed orifices, or changing valve positions or regulator setting.
Correct Answer : Increase in dripping flow
Explanation : Improper starting control design may or may not lead to an increase in dripping flow. But it can lead to the accumulation of unburned propellants in the combustion chamber, chances of explosion upon ignition and eventual damage to a rocket engine.
Correct Answer : photocell; pyrometer
Explanation : Bolometer is used for measuring radiant energy, whereas load cells act as transducers which converts force into measurable electrical output. Photocell is used for visual detection, while pyrometer for heat detection.
Correct Answer : chemical
Explanation : Because of the simplicity in logistics and its ability to be launched quickly, military missiles are typically chemical rocket engines. Most of the time, they employ solid rocket propellants for similar reasons.
Correct Answer : Injecting liquid into the gas streams before injection
Explanation : Injecting gas into liquid streams before the injection is a method for achieving a variable thrust but not vice versa. Varying injection element area can be done via selectable manifolds and movable injector elements.
Correct Answer : Increase in specific impulse
Explanation : Depending upon the gelling agent, specific impulse might change. Because of the dilution of the propellants with a gelling agent, there is generally a small decrease in specific impulse. It will also lead to less efficient atomization or combustion.
Correct Answer : Decrease in density impulse
Explaination : Density impulse is the specific impulse of the propellants multiplied by its density. Addition of small inert solid particles will increase the density of the propellant and hence lead to improved impulse density. This also means that the volume required to store the propellants is lesser and the rocket size becomes smaller. It will lead to drag reduction (since the surface area is lesser) under atmospheric operating conditions and improve speed and range of the vehicle.
Correct Answer : Thixotropic
Explaination : Thixotropic fluids become thinner (or less viscous) over time when adequate shear stresses are applied on it. A dilatant material has increasing viscosity with the rate of shear strain. A Newtonian fluid is a fluid in which the viscous stresses arising from its flow is linearly proportional to the local strain rate. Non-Newtonian fluids are those fluids that doesn’t obey Newton’s law of viscosity (which states that the shear stress between two adjacent fluid layers is proportional to the negative value of velocity gradient between those two layers).
Correct Answer : decoy flare
Explanation : Decoy flare is an infrared countermeasure taken by airborne vehicles against homing infrared missiles to divert its attention from its target. It is not a kind of tactical missile.
