Start delay includes the time taken to _________

close valves

lower the flow

terminate combustion

raise chamber pressure

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.

Recently Updated in Rocket Propulsion Questions

A tactical missile is not used for _________

decoy flare

attacking ground troops

defending ground troops

attacking military aircrafts

Correct Answer : Option (A) : 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.

Propellants that are thick or viscous under static conditions, but flow through valves, injectors, pipes or pumps when adequate shear stress is applied are called __________ propellants.

Dilatant

Thixotropic

Newtonian fluid

Non-Newtonian fluid

Correct Answer : Option (B) : 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).

Which of the following will not happen if small aluminum particles are suspended in the fuel or if small inert solid particles are suspended in the oxidizer?

Increase in propellant density

Decrease in density impulse

Reduction in tank and vehicle size

Increase in speed and range of atmospheric rockets or missiles

Correct Answer : Option (B) : 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.