Glossary — I
10 terms
Inclination
The angle between an orbit's plane and the equatorial reference plane, measured in degrees.
Example: Launching from Cape Canaveral restricts achievable inclinations to at least 28.5 degrees.
Inertial navigation system
A navigation system using gyroscopes and accelerometers alone.
Example: The inertial navigation system tracked position without GPS.
Interplanetary mission
A mission traveling between planets.
Example: Interplanetary missions rely on gravity assists to save fuel.
Inertial measurement unit
A sensor suite measuring acceleration and rotation for navigation.
Example: The inertial measurement unit tracked velocity changes during the burn.
Instantaneous window
A launch window with no flexibility; launch must occur at one moment.
Example: Rendezvous missions often have an instantaneous launch window.
Igniter
The device that initiates combustion in a rocket engine.
Example: The igniter sparked the main engine moments before liftoff.
Inspection mission
A mission that approaches another object to examine or monitor it.
Example: An inspection mission examined the damaged solar array.
Impulse
The total change in momentum delivered by a burn, force integrated over time.
Example: Total impulse measures how much a solid motor moves the vehicle overall.
Ignition sequence
The choreographed startup of engines before release.
Example: The ignition sequence built thrust over several seconds.
Ionosphere
An upper atmospheric layer rich in ions, affecting radio signals.
Example: The ionosphere refracts signals from navigation satellites.