Which of the following studies usually result in a small improvement in vehicle performance?

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.

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).

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.