Comprehensive Study Guide on Planetary Science, Orbital Mechanics, and Spacecraft Systems

Glossary and Acronyms

• General Acronyms

  • SSSB: Small Solar System Bodies.

  • TNO: Trans-Neptunian Objects (bodies located beyond the planets).

  • AU: Astronomical Unit.

  • LEO: Low-Earth Orbit.

  • MEO: Medium-Earth Orbit.

  • GEO: Geostationary Orbit.

  • SOI: Sphere of Influence.

  • PVA: Photovoltaic Assembly.

• Spacecraft Systems and Life Support (ECLSS)

  • ACS: Atmospheric Control System (manages pressure).

  • ARS: Air Revitalization System.

  • CDRA: Carbon Dioxide Removal Assembly.

  • ACLS: Advanced Closed Loop System (an improved version of the CDRA).

  • TCCS: Trace Contaminant Control System.

  • MCA: Major Constituent Analyzer.

  • THC: Temperature Humidity Control.

  • IMV: Intramodule Ventilation.

  • CCAA: Common Cabin Air Assembly.

  • WRM: Water Recovery Management.

  • UPA: Urine Processing Assembly.

  • VS: Vacuum System.

  • LSS: Life Support System.

• Communication, Guidance, and Power

  • DSN: Deep Space Network.

  • CRONUS: Communication Radiofrequency Operating Network Utilization Specialist.

  • MCC: Mission Control Center.

  • WSTF: White Sands Test Facility.

  • TDRS: Tracking Data Relay Satellite.

  • GNC: Guidance, Navigation, and Control (alternatively Alt Tracking & Determination).

  • CMG: Control Movement Gyroscopes (used for attitude determination).

  • C & W: Caution and Warning system.

  • EPS: Electric Power System.

  • SAWs: Solar Array Wings.

  • SARJ: Solar Array Rotating Joint.

  • PBA: Portable Breathing Apparatus.

  • PFE: Portable Fire Extinguisher.

• Rocketry and Operations

  • VTHL: Vertical Take-off, Horizontal Landing.

  • ALHL: Air Launch, Horizontal Landing.

  • VTVL: Vertical Take-off, Vertical Landing.

  • SMRPESA: Station modes (Station keeping, Microgravity operation, Reboost, Proximity operations, External, Standard, Assured safe crew return).

The Solar System and Planetary Science

• Formation: The solar system consists of the Sun, eight planets, moons, asteroids, and SSSBs. It is established that planets and stars are formed through the same general process.

• Terrestrial Planets: Characterized by rocky surfaces and solid cores.

  • Mercury:

    • Distance: $55 \times 10^6\,\text{km}$ from the Sun.

    • Density: $5.43\,\text{g/cm}^3$.

    • Atmosphere: None.

    • Moons: None.

    • Orbital Period: $88\,\text{days}$.

    • Unique Feature: Closest planet to the Sun.

  • Venus:

    • Distance: $165 \times 10^6\,\text{km}$.

    • Density: $5.29\,\text{g/cm}^3$.

    • Atmosphere: Yes (Thick atmosphere, extreme surface pressure of $92\,\text{bars}$).

    • Moons: None.

    • Orbital Period: $225\,\text{days}$.

    • Unique Feature: Known as the "Hottest Planet."

  • Earth:

    • Distance: $150 \times 10^6\,\text{km}$.

    • Density: $5.51\,\text{g/cm}^3$.

    • Atmosphere: Yes.

    • Moons: $1$.

    • Unique Feature: Only planet currently known to be habitable.

  • Mars:

    • Distance: $227 \times 10^6\,\text{km}$.

    • Density: $3.93\,\text{g/cm}^3$.

    • Atmosphere: Yes (thin).

    • Moons: $2$ (Phobos and Deimos).

    • Orbital Period: $687\,\text{days}$.

    • Unique Feature: Only planet with exactly two moons.

• Asteroid Belt: Located between Mars and Jupiter.

• Gas and Ice Giants: Primarily composed of hydrogen and helium (gas) or water, ammonia, and methane ices.

  • Jupiter:

    • Distance: $5.2\,\text{AU}$.

    • Density: $1.3\,\text{g/cm}^3$.

    • Atmosphere: Yes.

    • Moons: $101$.

    • Orbital Period: $12\,\text{year}$.

    • Unique Feature: Largest planet by volume.

  • Saturn:

    • Distance: $9.5\,\text{AU}$.

    • Density: $0.7\,\text{g/cm}^3$ (lower than water density).

    • Atmosphere: Yes.

    • Moons: $279$.

    • Unique Feature: Most moons in the solar system; notable ring system.

  • Uranus:

    • Distance: $19\,\text{AU}$.

    • Density: $1.2\,\text{g/cm}^3$.

    • Atmosphere: Yes.

    • Moons: $29$.

    • Orbital Period: $84\,\text{year}$.

    • Unique Feature: Lowest density of an ice planet.

  • Neptune:

    • Distance: $30\,\text{AU}$.

    • Distance: $1.6\,\text{g/cm}^3$.

    • Atmosphere: Yes.

    • Moons: $16$.

    • Orbital Period: $164\,\text{year}$.

    • Unique Feature: Farthest from the Sun.

Orbital Mechanics and Maneuvers

• Kepler’s Laws: Planetary orbits are elliptical and governed by gravity.

• The Six Orbital Elements (Keplerian Elements):

  • Semi-major axis ($a$): Defines the size of the orbit.

  • Eccentricity ($e$): Defines the shape of the orbit (circular vs. elliptical).

  • Inclination ($i$): Defines the orientation of the orbit relative to the Earth's equator.

  • Argument of Perigee ($\omega$): Defines the location of the orbit's low point (perigee) relative to the Earth's surface.

  • Right Ascension of the Ascending Node ($\Omega$): Defines the location of the ascending node relative to the equatorial plane.

  • True/Mean Anomaly ($\nu$): Defines the satellite's specific position within the orbit at a given time.

• Common Orbit Types:

  • LEO, MEO, GEO.

  • Polar Orbit.

  • Sun-synchronous Orbit.

  • Molniya Orbit: A highly elliptical, high-inclination orbit, utilized for communication at high latitudes.

• Transfers and Maneuvers:

  • Hohmann Transfer: The primary method to move a spacecraft between two circular orbits of different radii.

  • Gravity Assists: Using planet gravity to change the path/speed of a spacecraft.

  • Escape Velocity: The speed needed to break free from a gravitational field.

  • Sphere of Influence (SOI): The region around a celestial body where its gravity is the primary influence on an object.

Flagship Exploration Missions

• Cassini: Explored Saturn, its rings, and moons (Titan and Enceladus).

• New Horizons: Explored the "Frontier Worlds," Pluto, and the Kuiper Belt.

• James Webb Space Telescope (JWST): A premier deep-space observatory.

• Perseverance: Part of the Mars 2020 mission; currently exploring the Martian surface.

Spacecraft Systems: Life Support (ECLSS)

• Mass Balance: This tracks the weight of essentials for each crewmate daily. Total consumables amount to approximately $5\,kg$ per crew member per day ($5\,kg/C.M./D$).

  • Oxygen ($O_2$): $840\,g$.

  • Carbon Dioxide ($CO_2$): $1\,kg$.

  • Food: $640\,g$.

  • Water: $3.5\,kg$.

• Atmospheric Control & Revitalization (ACS & ARS):

  • Includes pressure management.

  • CO2 Removal: Handled by the Carbon Dioxide Removal Assembly (CDRA) or the improved Advanced Closed Loop System (ACLS).

  • Catalysts: The process produces methane as a byproduct, which can be potentially repurposed as fuel.

  • MCA: Monitors major constituents of the air.

  • TCCS: Manages trace contaminants.

• Temperature and Humidity Control (THC):

  • Comfort Box: The target environmental range is between $18\,^\circ\text{C}$ and $26\,^\circ\text{C}$.

  • Averages: Target temperature is $21.5\,^\circ\text{C}$; target humidity is $30\%$ (range of $25\text{--}75\%$).

  • Components: Intramodule Ventilation (IMV) and Common Cabin Air Assembly (CCAA).

• Water Recovery Management (WRM) & Vacuum System (VS):

  • Recycles approximately $93\%$ of water.

  • UPA: Urine Processing Assembly.

• Fire Detection and Suppression (FDS):

  • Uses Portable Fire Extinguishers (PFE) and Portable Breathing Apparatus (PBA).

Spacecraft Systems: Navigation, Comms, and Power

• Guidance, Navigation, and Control (GNC):

  • Guidance: Defining the path.

  • Navigation: State determination (position and velocity).

  • Control: Executing maneuvers such as Reboost.

  • Attitude Determination: Uses Control Movement Gyroscopes (CMGs).

  • Thrusters & Gyrodynes: Used for pointing and support.

• Communications Network:

  • S-Band: Lower frequency.

  • Ku-Band: Composite/higher frequency.

  • Deep Space Network (DSN): Three sites separated by $120\,^\circ$ to provide continuous coverage:

    • Goldstone, California.

    • Madrid, Spain.

    • Canberra, Australia.

  • Network Flow: Mission Control Center (MCC) \rightarrow White Sands Test Facility (WSTF) \rightarrow Tracking Data Relay Satellite (TDRS) \rightarrow International Space Station (ISS).

• Caution and Warning (C & W):

  • Class 1 (Emergency): Beeping sound.

  • Class 2 (Warning): Siren sound.

  • Class 3 (Caution): Tone sound.

  • Class 4 (Advisory): No sound.

• Electrical Power System (EPS):

  • Collects, converts, manages, and distributes power.

  • SAWs: Solar Array Wings.

  • SARJ: Solar Array Rotating Joint.

  • Power Levels: Produces between $54\,kW$ (during eclipse) and $120\,kW$ (in full light).

• Thermal Control System:

  • Passive Control: Coasting insulation, sun shields, louvers, blankets, and specialized paint.

  • Active Control: Active mechanical systems.

Rocketry and Launch Vehicles

• Rocket Systems:

  • Structural: Includes the nose cone, frame, and fins.

  • Propulsion: Includes fuel, oxidizer, pumps, and the nozzle.

  • Payload: The intended cargo.

  • Guidance: Uses gimbaled thrust (changing the angle of the thrust to steer).

• Flight Phases:

  1. Launch.

  2. Powered Flight.

  3. Staging.

  4. Cut-off.

• Performance Metrics:

  • Rocket acceleration: $0$ to $28,000\,km/hr$.

  • Considerations: Fuel flow rate, exhaust gas velocity, and pressure differential.

• Types of Launch Vehicles:

  • VTHL: Vertical Take-off, Horizontal Landing.

  • ALHL: Air Launch, Horizontal Landing.

  • VTVL: Vertical Take-off, Vertical Landing.

  • Historical Note: Early launch vehicles were functionally similar to missiles.