JNTU B.Tech III SPACE PROPULSION Previous Question Paper (February/March - 2022 - R18)

Orbital elements are the set of six parameters required to uniquely define the size, shape, and orientation of an orbit in space. These elements are essential for mission planning, satellite tracking, and orbital determination.

1. Semi-major axis (a): Defines the size of the orbit and the orbital period.
2. Eccentricity (e): Describes the shape of the orbit, ranging from a perfect circle (e=0) to an elongated ellipse.
3. Inclination (i): The angle between the orbital plane and the Earth's equatorial plane, determining the satellite's latitudinal coverage.
4. Right Ascension of the Ascending Node (Ω): The angle from a reference direction to the point where the orbit crosses the equator moving north.
5. Argument of Perigee (ω): The angle from the ascending node to the point of closest approach (perigee), defining the orbit's orientation within its plane.
6. True Anomaly (ν): The angular position of the satellite in its orbit relative to the perigee at a specific time.

These elements allow engineers to predict the future position of a spacecraft and ensure it remains within its designated operational envelope.

Reaction Control Systems (RCS) are propulsion systems used for attitude control and station-keeping in spacecraft and high-altitude vehicles where aerodynamic surfaces are ineffective.

Applications:

• Attitude control for pointing sensors, antennas, or solar arrays.
• Station-keeping to maintain a satellite's precise orbital position against perturbations.
• Docking and rendezvous maneuvers between two spacecraft.
• De-tumbling a spacecraft after deployment from a launch vehicle.
• Providing small delta-v adjustments for orbital corrections.

Limitations:

• Propellant Mass: RCS requires carrying dedicated chemical propellant, which limits the mission lifespan based on the fuel budget.
• Complexity: Requires pressurized tanks, valves, and thrusters, increasing the risk of mechanical failure.
• Contamination: Exhaust plumes from chemical thrusters can contaminate sensitive optical or thermal surfaces on the vehicle.
• Response Time: While fast, there is a finite latency in valve actuation and combustion initiation compared to reaction wheels.