1. Which of these orbital elements determines the size of the lunar orbit?
a) Argument of periapsis
c) Semi-major axis
Explanation: The six orbital elements are used to describe the shape, size and orientation. The semi-major axis (a) is used to determine the size of the orbit. Eccentricity is is determine the orbit shape, and the argument of periapsis determines the orbit’s orientation.
2. What phenomenon allows spacecraft to achieve a speed boost by utilizing the gravitational pull of a celestial body?
a) Stellar wind acceleration
b) Orbital decay
c) Magnetic propulsion
d) Gravitational slingshot
Explanation: Gravitational slingshot, also known as gravity assist, is a technique where a spacecraft gains speed and changes its trajectory by using the gravitational pull of a celestial body (usually a planet). The spacecraft uses the body’s momentum to propel itself forward, altering its speed and direction.
3. Which of these orbital changes is required to change from an inclined orbit to an equatorial orbit?
a) Out-of-plane orbit change
b) In-plane orbit change
c) Three-dimensional orbit change
d) Inclination change
Explanation: Changing an inclined orbit to an equatorial orbit involves change in plane which is an example of a simple plane change. This is a part of out- of-plane change as it involves change in the orientation of the orbital plane.
4. In a chase maneuver, what is the term used for passive spacecraft that is being chased?
Explanation: When two spacecrafts are orbiting in a rendezvous, and one spacecraft tries to intercept the other spcecraft, the maneuvering spacecraft is known as ‘Chase’ and the one that is being chased is called ‘Target’.
5. What is the latitude of the launch site at Cape Kennedy for coplanar trajectories?
Explanation: Since it is not possible to launch satellite from Earth into an orbit whose inclination is less than the launch site, there is a possibility of coplanar trajectory launch from Cape Kennedy whose latitude 28.5° and moon is at maximum inclination of 28.5° as well.
6. In total how many orbital elements are defined to find the position and orientation of a spacecraft?
Explanation: In total, there are six orbital elements defined. Out of these 2 parameters: eccentricity and angular momentum are used to define the orbit. True anomaly is used to find the location of the object in the orbit. Three additional Euler angles are used to describe the orientation of the orbit. These are- inclination, argument of perigee and right ascension of the ascending node.
7. Which spacecraft component is responsible for altering the orientation of a spacecraft in space?
b) Solar panels
d) Heat shield
Explanation: Thrusters are used to change the orientation (attitude) of a spacecraft in space by providing controlled bursts of propulsion. They help adjust the spacecraft’s position, change its direction, and perform maneuvers necessary for navigation and docking.
8. What is the true anomaly of the spacecraft? Given, position vector 2100 i + 1850 j km.
a) 0.67 rad
b) 0.73 rad
c) 0.88 rad
d) 1.004 rad
x = 2100 km
y = 1850 km
True anomaly (θ) = atan(y/x)
= atan (1850/2100)
= 0.88 rad
9. Which of these is not the cause of orbital perturbations?
a) Asphericity of Earth
b) Climate changes
c) Aerodynamic drag
d) Atmospheric drag
Explanation: Perturbations are disturbances causing the object to deviate from the original orbit. The main reasons for perturbations are: aerodynamic drag, asphericity of earth, atmospheric drag, radiation pressure, solar wind pressure and electromagnetic effect. Climate change on the other hand is a result of orbital perturbations.
10. What term describes the process of aligning a spacecraft’s trajectory with the desired destination using minimal fuel?
a) Hohmann transfer
b) Trajectory optimization
c) Orbital inclination
d) Attitude control
Explanation: Hohmann transfer is a fuel-efficient orbital maneuver used to transfer a spacecraft between two orbits by utilizing two engine burns. It allows for the alignment of the spacecraft’s trajectory with the desired destination while minimizing fuel consumption.
11. Which of these objects is a solid debris from comet, asteroid etc. which travels to reach the surface of planet or moon?
Explanation: Meteorite is a solid debris present in the solar system which is a result of aftermath from a collision of a comet, asteroid. They tend to travel to the planet or moon’s surface by surviving through the atmosphere. While entering the planet’s atmosphere, it becomes a meteor which glows up due to the friction causing it to radiate heat and energy.
12. Which error is the miss distance at moon a function of?
a) Flight-path angle
b) True anomaly
Explanation: The miss distance at moon is a function of flight-path angle error only. For understanding, an error od about 1 deg in flight-path angle can cause the spacrcraft to miss the distance at moon by 1,300 km.
13. Which of these trajectories is followed by the ballistic missile?
a) Aft-crossing trajectory
b) Planetary trajectory
c) Ballistic trajectory
d) Orbital trajectory
Explanation: A ballistic missile trajectory is used by missiles for warfare purposes. It is different from the orbit followed by the satellite as the ballistic missile trajectory intersects the Earth’s surface. The trajectory comprises of three portions-powered flight regime, free flight regime and the re-entry regime.
14. What is the mean distance between center of both earth and moon?
a) 400,000 km
b) 398,600 km
c) 360,000 km
d) 382,400 km
Explanation: Earth and moon revolve around a common center of mass. The mean distance between the centers of these two is 382,400 km. This value can often vary over the course of the orbit so the mean value of 382,400 km is considered. 398,600 km3 s is the gravitational parameter of the Earth.
15. When the change in velocity represents a change in direction, what kind of maneuver is it called?
a) Pumping maneuver
b) Cranking maneuver
c) Orbital lowering maneuver
d) Orbital raising maneuver
Explanation: Each impulsive maneuver results in a velocity change of the spacecraft. This velocity change yield both magnitude and direction change of the velocity vector. When Δv represents a change in direction it is referred as a cranking maneuver.
16. What is the orbital inclination of International Space Station?
Explanation: The orbital inclination of ISS is 52° and it orbits around the Earth from west to east. 98° is the orbital inclination of Mapping and 0° is for Geostationary satellites.
Chapterwise Multiple Choice Questions on Spaceflight Mechanics
- Planetary Atmosphere
- Attitude and Kinematics of Coordinate Frames
- Two-Body Mechanics
- Two-Body Orbital Mechanics
- Basic Orbital Maneuvers
- Orbital Maneuvers
- Orbit Determination from Observation
- Position & Velocity as a Function of Time
- Interplanetary Trajectories
- Lunar Trajectories
- Ballistic Missiles Trajectories
- Rocket Propulsion
1. Spaceflight Mechanics MCQ on Planetary Atmosphere
The section contains multiple choice questions and answers on planetary and standard atmosphere.
2. MCQ on Attitude and Kinematics of Coordinate Frames
The section contains spaceflight mechanics questions and answers on coordinate systems like eci coordinate system, azimuth elevation system, ecliptic coordinate system and transformation.
3. Spaceflight Mechanics Multiple Choice Questions on Two-Body Mechanics
The section contains spaceflight MCQs on two-body mechanics and n body problems.
4. MCQ on Two-Body Orbital Mechanics
The section contains orbital mechanics multiple choice questions and answers on two body problems, motion and conservation equations, celestial sphere concept, orbital elements, orbits, elliptical orbits, circular orbits, and hyperbolic orbits.
5. Basic Orbital Maneuvers
The section contains orbital mechanics MCQs on orbital maneuvers, hohmann transfer, in-plane and out-of-plane orbit changes, impulsive and non-impulsive maneuvers.
6. Orbital Mechanics MCQs on Orbital Maneuvers
The section contains multiple choice questions and answers on phasing and chase maneuvers, non-hohmann and bi-elliptical transfers, single and multi impulse orbital maneuvers.
7. Orbit Determination from Observation
The section contains questions and answers on orbit determination observations like ground tracks and time systems, space surveillance, sensors types and locations.
8. Orbital Mechanics MCQs on Position & Velocity as a Function of Time
The section contains MCQs on time of flight.
9. Spaceflight Mechanics Multiple Choice Questions on Perturbations
The section contains spaceflight mechanics multiple choice questions and answers on perturbations, third body perturbations, perturbations due to earth’s oblateness and atmospheric drag.
10. Interplanetary Trajectories
The section contains questions and answers on interplanetary trajectories like j2 and j3 effects, two impulse rendezvous maneuvers, interplanetary travel basics, critical inclination & special orbit types.
11. Lunar Trajectories
The section contains MCQs on earth moon system, moon orbital elements, seleno-centric trajectories, lunar trajectories important parameters, minimum energy trajectory, patched conic approximations, non-coplanar lunar and interplanetary trajectories, gravity assist maneuver, seleno-centric orbit launch, heliocentric approaches, launching opportunities, planets location and fast interplanetary trajectories.
12. MCQ on Ballistic Missiles Trajectories
The section contains spaceflight mechanics multiple choice questions and answers on ballistic missiles trajectories and its path, launching errors and earth’s rotation effects.
13. Spaceflight Mechanics Questions on Rocket Propulsion
The section contains questions and answers on rocket engine, single and multi stage rocket engines, parallel staging, mission trade-off and optimal rockets.
Wish you the best in your endeavor to learn and master Spaceflight Mechanics!