Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Orbital Decay and Lifetime

Description

This lecture covers the concept of orbital decay in Low Earth Orbit (LEO), discussing the factors influencing a satellite's lifetime, such as drag, atmospheric density, and orbital speed. It explains the drag equations and the role of the ballistic coefficient in prolonging a satellite's orbital lifetime. The lecture also presents data on various satellites, their mass, shape, cross-sectional areas, and drag coefficients, highlighting the importance of the ballistic coefficient in determining a satellite's orbital decay. Additionally, it explores different types of missions and their corresponding ballistic coefficients.

In MOOC

Space Mission Design and Operations

Official source

Related concepts (32)

Low Earth orbit

A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never more than about one-third of the radius of Earth. The term LEO region is also used for the area of space below an altitude of (about one-third of Earth's radius). Objects in orbits that pass through this zone, even if they have an apogee further out or are sub-orbital, are carefully tracked since they present a collision risk to the many LEO satellites.

Drag coefficient

In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag. The drag coefficient is always associated with a particular surface area. The drag coefficient of any object comprises the effects of the two basic contributors to fluid dynamic drag: skin friction and form drag.

Orbital decay

Orbital decay is a gradual decrease of the distance between two orbiting bodies at their closest approach (the periapsis) over many orbital periods. These orbiting bodies can be a planet and its satellite, a star and any object orbiting it, or components of any binary system. If left unchecked, the decay eventually results in termination of the orbit when the smaller object strikes the surface of the primary; or for objects where the primary has an atmosphere, the smaller object burns, explodes, or otherwise breaks up in the larger object's atmosphere; or for objects where the primary is a star, ends with incineration by the star's radiation (such as for comets).

Drag (physics)

In fluid dynamics, drag (sometimes called fluid resistance) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or between a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, the drag force depends on velocity. Drag force is proportional to the velocity for low-speed flow and the squared velocity for high speed flow, where the distinction between low and high speed is measured by the Reynolds number.

Geocentric orbit

A geocentric orbit, Earth-centered orbit, or Earth orbit involves any object orbiting Earth, such as the Moon or artificial satellites. In 1997, NASA estimated there were approximately 2,465 artificial satellite payloads orbiting Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. More than 16,291 objects previously launched have undergone orbital decay and entered Earth's atmosphere. A spacecraft enters orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the horizontal component of its velocity.

Related lectures (32)

Earth Orbits

Explores various Earth orbits, historical space missions, and solar system exploration.

Hohmann Transfer: Small AV MOOC: Space Mission Design and Operations

Discusses the Hohmann transfer for small AV and orbital parameters at different altitudes.

Space Debris: A Growing Threat MOOC: Space Mission Design and Operations

Explores the challenges posed by space debris accumulation in different orbits and the measures taken to prevent collisions.

Satcom Performances and Constraints MOOC: New Space Economy

Explores Satcom performances, bandwidth, orbits, and radio spectrum utilization in satellite communications.

Nodal Regression and Sun-synchronous Orbits MOOC: Space Mission Design and Operations