3.2 Effects of atmospheric drag and solar radiation pressure
3 min read•august 7, 2024
Atmospheric drag and solar radiation pressure are crucial forces affecting objects in orbit. These phenomena can alter trajectories, cause orbit decay, and even lead to deorbit. Understanding their impact is vital for predicting satellite lifetimes and managing space debris.
The effects vary based on factors like altitude, object shape, and area-to-mass ratio. Lower orbits experience more drag, while solar radiation pressure becomes significant for high orbits and lightweight objects. These forces shape the long-term behavior of orbiting bodies.
Atmospheric Drag Effects
Factors Influencing Atmospheric Drag
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- Atmospheric drag is a force that opposes the motion of an object moving through the atmosphere, causing it to slow down and lose altitude over time
- The magnitude of atmospheric drag depends on factors such as the object's velocity, , and the at its altitude
- Atmospheric density decreases exponentially with increasing altitude, meaning objects in lower orbits experience more drag than those in higher orbits
- The shape and orientation of the object also affect the amount of drag it experiences, with more aerodynamic shapes and orientations minimizing drag
Ballistic Coefficient and Area-to-Mass Ratio
- The ballistic coefficient is a measure of an object's ability to overcome atmospheric drag, calculated as the object's mass divided by its cross-sectional area and a
- Objects with higher ballistic coefficients experience less drag and maintain their orbits for longer periods
- The area-to-mass ratio of an object is another key factor in determining the effect of atmospheric drag, with objects having a high area-to-mass ratio (large surface area relative to mass) being more susceptible to drag
- Examples of objects with high area-to-mass ratios include solar sails and large, lightweight debris fragments
Orbit Decay and Deorbit
- Orbit decay is the gradual decrease in an object's orbital altitude due to atmospheric drag, which causes the object to spiral inward towards the Earth
- The rate of orbit decay depends on the object's initial altitude, ballistic coefficient, and the atmospheric conditions it encounters
- As an object loses altitude, it experiences increasingly dense atmosphere, leading to more rapid decay and eventually deorbit (reentry into the Earth's atmosphere)
- Deorbit can be intentional (controlled reentry) or unintentional (uncontrolled reentry) depending on the object's size, composition, and operational status
Solar Radiation Pressure Effects
Solar Radiation Pressure
- Solar radiation pressure is the force exerted on an object by the photons emitted by the Sun, which can alter the object's orbit over time
- The magnitude of solar radiation pressure depends on factors such as the object's surface area, reflectivity, and distance from the Sun
- Solar radiation pressure is generally much weaker than atmospheric drag but can have significant effects on objects with high area-to-mass ratios (solar sails) or those in high Earth orbits (geostationary satellites)
- The force of solar radiation pressure can be harnessed for propulsion, as demonstrated by solar sail technology
Poynting-Robertson Effect
- The Poynting-Robertson effect is a drag force caused by the interaction between solar radiation and an object's motion, causing the object to spiral inward towards the Sun
- This effect is the result of the Doppler shift of the solar radiation, which causes the object to absorb more energy from the direction of its motion and re-radiate that energy isotropically
- The Poynting-Robertson effect is most significant for small particles (dust grains) in interplanetary space, as they have a high area-to-mass ratio and are more susceptible to radiation pressure
- Over long timescales, the Poynting-Robertson effect can cause dust particles to migrate from the outer Solar System to the inner Solar System, contributing to phenomena such as the zodiacal light
Yarkovsky Effect
- The Yarkovsky effect is a force caused by the asymmetric emission of thermal radiation from an object's surface, which can alter the object's orbit over time
- This effect arises from the uneven heating and cooling of an object's surface as it rotates, causing a net force that can either accelerate or decelerate the object depending on its rotation direction
- The Yarkovsky effect is most significant for small asteroids (10 meters to 10 kilometers in diameter), as they have a high surface area to volume ratio and can experience rapid temperature changes
- The Yarkovsky effect can cause asteroids to migrate from the main asteroid belt to Earth-crossing orbits, making it an important consideration in asteroid impact risk assessment
Key Terms to Review (16)
Analytical models: Analytical models are mathematical representations used to describe and predict the behavior of physical systems through equations and formulas. These models are crucial for understanding complex phenomena, such as the effects of atmospheric drag and solar radiation pressure on satellites and other space debris. By utilizing analytical models, researchers can simulate the forces acting on objects in space, which helps in predicting their trajectories, lifetimes, and potential collisions with other debris.
Coronal Mass Ejections: Coronal mass ejections (CMEs) are large expulsions of plasma and magnetic field from the sun's corona into space, which can significantly impact the solar system, including Earth's atmosphere. These massive bursts can disturb the Earth's magnetic field and lead to various space weather phenomena, affecting satellite operations and space debris behavior through changes in atmospheric drag and radiation pressure.
Cross-sectional area: Cross-sectional area is the area of a particular section of an object that is perpendicular to the direction of flow or movement, which plays a critical role in understanding how objects interact with forces such as atmospheric drag and solar radiation pressure. This measurement helps quantify how much of an object is exposed to these forces, impacting its behavior and stability in space. In the context of space, cross-sectional area influences the drag force experienced by satellites and other objects as they travel through the atmosphere and also affects how they respond to solar radiation.
De-orbiting: De-orbiting is the process of deliberately bringing a satellite or space debris back into the Earth's atmosphere, leading to its re-entry and eventual disintegration. This action helps manage space debris and mitigate the risks associated with defunct satellites and fragments in orbit. Effective de-orbiting is influenced by factors such as atmospheric drag and solar radiation pressure, which play crucial roles in determining the trajectory and timing of re-entry, as well as compliance with national space agency standards aimed at responsible space operations.
Density of the atmosphere: The density of the atmosphere refers to the mass of air per unit volume, typically expressed in kilograms per cubic meter (kg/m³). This density decreases with altitude due to the decreasing pressure and temperature, affecting how objects move through the air, especially at higher altitudes where space debris operates. The density plays a critical role in determining the amount of atmospheric drag experienced by satellites and other objects in low Earth orbit, as well as their interaction with solar radiation pressure.
Drag Coefficient: The drag coefficient is a dimensionless number that quantifies the drag or resistance of an object in a fluid environment, such as air. This coefficient is crucial for understanding how atmospheric drag impacts the motion of objects in space, especially for satellites and space debris, as it helps predict the deceleration due to air resistance and the effects of solar radiation pressure on their trajectories.
End-of-life disposal: End-of-life disposal refers to the processes and methods used to manage spacecraft and satellite systems when they reach the end of their operational lifespan. This includes strategies to ensure that defunct satellites do not contribute to space debris, which can pose risks to active spacecraft and the sustainability of space activities.
Force on Spacecraft: The force on spacecraft refers to the net external forces acting on a spacecraft, which can significantly impact its trajectory, orientation, and operational capabilities. This includes the effects of gravitational forces from celestial bodies, as well as forces due to atmospheric drag and solar radiation pressure, both of which can alter a spacecraft's path and speed in orbit or during atmospheric re-entry.
Numerical simulations: Numerical simulations are computational techniques used to model and analyze complex systems by solving mathematical equations numerically rather than analytically. They play a critical role in understanding the behavior of physical phenomena, allowing researchers to predict outcomes based on varying conditions, especially in fields such as aerospace engineering and space science. By simulating real-world processes, numerical simulations help in evaluating the effects of atmospheric drag and solar radiation pressure on objects in orbit.
Orbital altitude reduction: Orbital altitude reduction refers to the decrease in the altitude of a satellite's orbit due to various forces acting on it, primarily atmospheric drag and solar radiation pressure. This reduction can lead to changes in the satellite's orbital parameters, affecting its operational lifetime and increasing the risk of reentry or collision with other space debris. Understanding these forces is crucial for predicting satellite behavior and planning effective debris mitigation strategies.
Passivation: Passivation refers to the process of making a spacecraft component inactive or inert after its operational lifetime to minimize the potential for creating space debris. This involves depleting remaining fuel, discharging batteries, and ensuring that no unintentional explosions or fragmentation can occur, thereby contributing to efforts aimed at responsible space debris management.
Radiation Pressure Force: Radiation pressure force is the pressure exerted by electromagnetic radiation on surfaces due to the transfer of momentum from photons when they strike an object. This force plays a critical role in the dynamics of space debris and satellites, especially in low Earth orbit, where the effects of solar radiation pressure can influence their trajectories and stability over time.
Re-entry: Re-entry refers to the process where an object from space, such as a satellite or spacecraft, returns to the Earth's atmosphere. During this phase, the object encounters atmospheric drag and solar radiation pressure, which significantly affect its trajectory and speed, ultimately determining whether it will burn up upon re-entry or successfully land on the surface.
Shielding: Shielding refers to the protective measures implemented to reduce the effects of external factors, such as radiation or impact from space debris, on spacecraft and their components. This concept is crucial in the context of space operations, where the harsh environment of space can pose significant risks to equipment and human safety. Effective shielding can help mitigate damage from high-velocity impacts and minimize radiation exposure, thereby ensuring the longevity and reliability of missions.
Solar Flux: Solar flux is the amount of solar energy received per unit area at a given distance from the Sun, typically expressed in watts per square meter (W/m²). This measurement plays a crucial role in understanding how solar radiation influences objects in space, particularly in relation to atmospheric drag and solar radiation pressure that affects satellites and space debris.
Trajectory alteration: Trajectory alteration refers to the intentional or unintentional change in the path of an object in space, which can occur due to various forces acting on it. This term is closely linked to the influences of atmospheric drag and solar radiation pressure, which can significantly modify the orbits of satellites and space debris over time. Understanding how these forces impact trajectory alteration is crucial for predicting the behavior of objects in orbit and for developing effective mitigation strategies.