Glossary — O
15 terms
Oxidizer
The propellant component that supplies oxygen to support combustion in a vacuum.
Example: Liquid oxygen is the most common oxidizer for cryogenic stages.
Orbiter
A spacecraft designed to enter orbit around a target body.
Example: The orbiter studied Mars for several years.
Orbital period
The time a body takes to complete one full revolution around its primary.
Example: The ISS completes an orbital period in about 92 minutes.
Orbital velocity
The speed needed to remain in a stable orbit at a given altitude.
Example: Low Earth orbit requires an orbital velocity of roughly 7.8 km per second.
Observatory mission
A mission carrying telescopes to observe the universe.
Example: The observatory mission imaged the first galaxies.
Open-loop control
Control acting on precomputed commands without feedback.
Example: Open-loop timing fired separation pyros at fixed times.
Orbital elements
The set of parameters that uniquely describe an orbit's shape, size, orientation, and timing.
Example: The six classical orbital elements fully define a Keplerian orbit.
Orbital decay
The gradual lowering of an orbit due to atmospheric drag, eventually leading to reentry.
Example: Without reboost, the station would suffer orbital decay and reenter the atmosphere.
Orbital mission
A flight that achieves a full orbit of Earth.
Example: The orbital mission deployed three satellites.
Onboard computer
The flight computer that executes commands and manages subsystems.
Example: The onboard computer autonomously executed the stored sequence.
Orbital plane
The flat geometric plane containing an orbit.
Example: A plane-change maneuver rotates the orbital plane at high fuel cost.
Orbital insertion
The maneuver that places a spacecraft into its intended orbit.
Example: The loss of telemetry during orbital insertion triggered an anomaly review.
Orbital maneuver
Any deliberate change to a spacecraft's velocity to modify its orbit.
Example: Routine orbital maneuvers correct drift and station-keeping errors.
Ozone layer
A stratospheric region rich in ozone that absorbs ultraviolet light.
Example: The ozone layer shields the surface from harmful UV.
Oxidizer-rich
A combustion mixture with excess oxidizer, used to drive turbopumps in some cycles.
Example: Oxidizer-rich preburners feed hot gas to the oxidizer turbopump.