What is sphere of influence of a planet?

Fictitious boundary where there is atmosphere

Fictitious boundary for 2-body motion about a planet

Fictitious boundary where there is presence of gravity

Fictitious boundary for N-body motion about a planet

Correct Answer : Fictitious boundary for 2-body motion about a planet

Explanation : Sphere of Influence is a fictitious boundary where when the satellite enters, its orbit can be approximated by the two-body problem with the planet as the central body. It cannot be used to represent the motion of N-body gravity field.

Recently Updated in Spaceflight Mechanics Questions

In the heliocentric phase of the patched conic method, which orbit is followed by the spacecraft?

Circular

Parabolic

Elliptic

Hyperbolic

Correct Answer : Option (C) : Elliptic

Explanation : In the heliocentric phase of the patched conic method, the spacecraft follows the elliptical transfer orbit where sun is considered as the primary gravitational body. The interplanetary cruise is analyzed by two-body mechanics in heliocentric0ecliptic coordinate frame.

According to Laplace, how is the sphere of influence defined?

Ratio of central- body acceleration and perturbing acceleration

Ratio of gravitational field of the planet to the potential field of the object

Ratio of perturbing acceleration and central-body acceleration

Ratio of the potential field of the object to the gravitational field of the planet

Correct Answer : Option (C) : Ratio of perturbing acceleration and central-body acceleration

Explanation : According to Laplace, Sphere of Influence (SOI) is described as the ratio of perturbing acceleration and central-body acceleration.

In order to arrive from the Earth to the target planet for example Venus, which of these arrival orbits it used?

Hyperbolic

Circular

Elliptical

Parabolic

Correct Answer : Option (A) : Hyperbolic

Explanation : The arrival trajectory inside the target planet’s sphere of influence is done using a hyperbolic orbit which is analyzed in inertial planet-centered frame. As soon as the spacecraft enters the target planet’s sphere of influence, the sun’s gravity is turned off and planet’s gravity is turned on.