# Non-Coplanar Interplanetary Trajectories Questions and Answers

This set of Spaceflight Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Non-Coplanar Interplanetary Trajectories”.

1. Which of these planets have the highest inclination to the ecliptic plane?
a) Mars
b) Jupiter
c) Mercury
d) Saturn

Explanation: Out of all the planets, Mecury has the highest inclination to the ecliptic plane. It is 7° .004 compared to Mars having 1° .850, Jupiter having 1° .306 and Saturn having 2° .489. Although, Pluto is not considered as a planet, it is worth nothing that it has the highest inclination of 17° .136 to the Earth’s ecliptic plane.

2. How is the spacecraft launched to a planet which lies above or below the ecliptic plane?
a) Launch into transfer orbit in ecliptic plane followed by plane change maneuver
b) Carry a simple plane change maneuver
c) Launch into transfer orbit in ecliptic plane
d) Launch into a transfer orbit perpendicular to the ecleptic plane

Explanation: When launching spaceraft in an interplanetary trajectory where the planet’s orbit lies above or below the ecleptic plane, we first launch it in the transfer orbit in the same ecleptic plane. After that, a simple plane change maneuver is performed mid-course.

3. When is the plane change maneuver performed in case of interplanetary trajectory with the planet’s orbit lying at an angle to the ecliptic plane?
a) 45 deg prior to the intercept
b) 90 deg prior to the intercept
c) 180 deg prior to the intercept
d) 60 deg prior to the intercept

Explanation: In case of interplanetary trajectories with planet’s orbit at an angle to the ecliptic plane, there has to be a plane change maneuver to be carried out. This is done 90 deg prior to the intercept to minimize the plane change requirements.

4. What is the formula used to compute the delta-v required to perform plane change maneuver?
a) Δv = 2v sin $$\frac{i}{2}$$
b) Δv = 2v cos $$\frac{i}{2}$$
c) Δv = v sin $$\frac{i}{2}$$
d) Δv = v cos $$\frac{i}{2}$$

Explanation: In order to reach the planet which is at an angle to the ecliptic plane, a simple plane change maneuver has to be performed by the spacecraft involving delta-v. The formula used is:
Δv = 2v sin $$\frac{i}{2}$$
Where, v is the velocity of the spacecraft
i is the angle of inclination with the ecliptic plane.

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