Controlled atmospheric re-entry is a crucial strategy for safely disposing of spacecraft at the end of their missions. This process involves carefully planning and executing the spacecraft's descent through Earth's atmosphere to minimize risks to people and property on the ground.
Re-entry techniques include propulsive methods using thrusters and passive systems relying on natural forces. The dynamics of re-entry, including the and breakup process, are key factors in ensuring a safe disposal of space debris.
De-orbit Techniques
Propulsive De-orbit Methods
Top images from around the web for Propulsive De-orbit Methods
Spacecraft electric propulsion - Wikipedia View original
Is this image relevant?
8.7 Introduction to Rocket Propulsion – College Physics: OpenStax View original
Is this image relevant?
File:Apollo Spacecraft diagram.jpg - Wikipedia View original
Is this image relevant?
Spacecraft electric propulsion - Wikipedia View original
Is this image relevant?
8.7 Introduction to Rocket Propulsion – College Physics: OpenStax View original
Is this image relevant?
1 of 3
Top images from around the web for Propulsive De-orbit Methods
Spacecraft electric propulsion - Wikipedia View original
Is this image relevant?
8.7 Introduction to Rocket Propulsion – College Physics: OpenStax View original
Is this image relevant?
File:Apollo Spacecraft diagram.jpg - Wikipedia View original
Is this image relevant?
Spacecraft electric propulsion - Wikipedia View original
Is this image relevant?
8.7 Introduction to Rocket Propulsion – College Physics: OpenStax View original
Is this image relevant?
1 of 3
Deorbit maneuvers involve changing the orbit of a spacecraft to cause it to re-enter the Earth's atmosphere
Propulsive de-orbit uses thrusters or engines to perform a retrograde burn, reducing the spacecraft's velocity and lowering its perigee into the dense atmosphere
Requires the spacecraft to have sufficient remaining propellant and functional propulsion system at the end of its mission
Commonly used for large spacecraft (International Space Station modules) and those in higher orbits (geostationary satellites)
Passive De-orbit Systems
Passive de-orbit systems rely on natural perturbations and forces to gradually lower the spacecraft's orbit over time
Atmospheric is the primary passive de-orbit mechanism for low Earth orbit (LEO) satellites
As the spacecraft encounters drag forces from the thin upper atmosphere, its orbit decays until it re-enters
Effectiveness depends on factors such as the spacecraft's altitude, cross-sectional area, and mass
Other passive de-orbit techniques include using deployable structures (drag sails or balloons) to increase the spacecraft's area-to-mass ratio and accelerate orbital decay
Re-entry Dynamics
Re-entry Corridor and Breakup
The re-entry corridor is the range of angles and velocities at which a spacecraft can enter the atmosphere to ensure a controlled and safe re-entry
Too steep of an angle can cause excessive heating and dynamic pressure, leading to disintegration
Too shallow of an angle may result in the spacecraft skipping off the atmosphere and failing to re-enter
Ablation is the process of the spacecraft's surface material vaporizing and eroding away due to extreme heat during re-entry, acting as a protective
Breakup altitude is the point at which the spacecraft or its components disintegrate due to re-entry forces, typically around 40-80 km altitude depending on the vehicle's design and re-entry conditions
Re-entry Survival Analysis
Re-entry survival analysis assesses the likelihood of spacecraft components or debris surviving the re-entry process and reaching the ground
Factors influencing survival include the material properties, size, shape, and mass of the components
Dense, high-melting-point materials (titanium or stainless steel tanks) are more likely to survive than lightweight, low-melting-point materials (aluminum or plastic)
Smaller, more aerodynamic shapes are more likely to burn up completely compared to larger, blunt objects
Surviving debris poses risks to people and property on the ground, necessitating careful design and disposal planning to minimize hazards
Risk Assessment
Ground Track Prediction and Casualty Risk
Ground track prediction involves modeling the spacecraft's re-entry trajectory and determining the potential impact locations of any surviving debris
Takes into account factors such as the spacecraft's orbit, attitude, and breakup characteristics
Uncertainties in the prediction arise from limitations in atmospheric density models, solar activity effects, and the complex dynamics of the disintegrating spacecraft
Casualty risk assessment quantifies the probability of a person being struck by re-entering debris based on the predicted ground track and population density data
Typically expressed as the expected number of casualties per re-entry event
International guidelines recommend limiting the casualty risk to less than 1 in 10,000 for controlled re-entries
Mitigation strategies to reduce casualty risk include performing controlled re-entries over uninhabited areas (oceans), designing spacecraft for more complete breakup, and scheduling re-entry events during times of low population density along the ground track