Free drift mode refers to the state of

motion In physics, motion is when an object changes its position with respect to a reference point in a given time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed, and frame of reference to an o ...

of an object in

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

whereby constant

attitude Attitude or Attitude may refer to: Philosophy and psychology * Attitude (psychology), a disposition or state of mind ** Attitude change * Propositional attitude, a mental state held towards a proposition Science and technology * Orientation ...

is not maintained. When attitude is lost, the object is said to be in free drift, thereby relying on its own

inertia Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newto ...

to avoid attitude drift. This mode is often engaged purposefully as it can be useful when modifying, upgrading, or repairing an object in space, such as the

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

. Additionally, it allows work on areas near the thrusters on the ISS that are generally used to maintain attitude. While in free drift it is not possible to fully use the

solar arrays A photovoltaic system, also called a PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to abs ...

on the ISS. This can cause a drop in

power generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its stora ...

, requiring the

conservation of energy The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be Conservation law, ''conserved'' over time. In the case of a Closed system#In thermodynamics, closed system, the principle s ...

. This may affect many systems that otherwise require a lot of energy.Bertels, 2006. The amount of time that an object such as the ISS can remain safely in free-drift varies depending on

moment of inertia The moment of inertia, otherwise known as the mass moment of inertia, angular/rotational mass, second moment of mass, or most accurately, rotational inertia, of a rigid body is defined relatively to a rotational axis. It is the ratio between ...

, perturbation torques, tidal gradients, etc. The ISS itself generally can last about 45 minutes in this mode.

Notes

References

Bertels, Gaston. November 10, 2006
''Commander Michael Lopez-Alegria talks to Belgian schoolchildren''
ARISS. Retrieved on April 26, 2006. Malik, Tariq. January 21, 2005

Space.com. Retrieved on April 26, 2008. Malik, Tariq. October 26, 2006

Space.com. Retrieved on April 26, 2008.
Celestial mechanics Orbits {{space-stub