Free drift mode refers to the state of
motion of an object in
orbit whereby constant
attitude
Attitude may refer to:
Philosophy and psychology
* Attitude (psychology), an individual's predisposed state of mind regarding a value
* Metaphysics of presence
* Propositional attitude, a relational mental state connecting a person to a prop ...
is not maintained. When attitude is lost, the object is said to be in free drift, thereby relying on its own
inertia 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. 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 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 absorb and ...
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 stor ...
, requiring the
conservation of energy
In physics and chemistry, the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be ''conserved'' over time. This law, first proposed and tested by Émilie du Châtelet, means th ...
. 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 mass, second moment of mass, or most accurately, rotational inertia, of a rigid body is a quantity that determines the torque needed for a desired angular acceler ...
,
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
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