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Interpreter Vocabulary

This web-based Science/Mathematics Sign Lexicon identifies published sources (books, CDs) where a sign may be found for a term and also includes many sign video demonstrations to assist in learning.

Science/Mathematics Sign Lexicon

The following is a list of words and abbreviations commonly used by NASA in the Space Shuttle operations at the UNITED STATES SPACE CAMP. Study them carefully and become familiar with them.

A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z

[ A ]

ABLATIVE MATERIAL: A material, especially a coating material, designed to provide thermal protection to a spacecraft speeding through the atmosphere during launch or re-entry by charring or burning away.
ABLE: Rhesus "monkeynaut" that flew with Miss Baker atop a U.S. Army Jupiter rocket on May 28, 1959. He died shortly after the flight was completed from the drugs used to sedate him.
AOA: Abort-Once-Around. A mode of launch abort which involves a landing after nearly one trip around Earth.
AOS: Acquisition of Signal. This is the point where air-to-ground communications resume after loss of signal or when communications are in operation.
APU: Auxiliary Power Unit. The orbiter has three of these that are used to generate hydraulic power for operating the Shuttle’s aerodynamic control surfaces (elevons, body flap, rudder), landing gear, and main engine gimbaling.
ATO: Abort-To-Orbit. A mode of launch abort that takes the orbiter into a lower than planned Earth orbit following the premature shutdown of a main engine.
ABORT: To cut the mission or activity short. An abort can be called by the Launch Director, Flight Director, or the Commander if a serious problem arises during the flight.
ABORT ADVISORY CHECK: This is a standard check prior to lift-off to make certain that the abort warning system is working properly.
ACQUISITION: In radar, the process of locating the orbit of a satellite or the trajectory of a spacecraft so that tracking or telemetry data can be gathered.
ACTUATOR: A device that supplies and transmits energy for the operation of other mechanisms.
AERODYNAMIC SKIP: An entry abort caused by an atmospheric impact at an excessively shallow angle resulting in a low trajectory; analogous to the skipping of a stone across the surface of a pond.
AIR DATA PROBES: Probes used to collect and send telemetry concerning air pressure, speed, and temperature during landing.
AIR-TO-GROUND: Radio voice communications between the orbiter and Mission Control.
AIRBORNE DATA: Data obtained from space systems during flight.
AIRLOCK: An airtight chamber used for passage between areas of different pressures.
ALTITUDE: The Shuttle’s vertical distance from the surface of Earth. The altitude is reported during launch, orbit, and landing.
ANGLE OF ATTACK: The angle between the chord line (i.e., straight line joining the centers of curvature of the leading and trailing edges) of an airfoil and the relative airflow, normally the immediate flight path of the aircraft.
APOGEE: The highest point of any Earth orbit; the point of any orbit farthest from Earth’s center.
APOLLO 11: The designation of the first manned mission to land on the Moon. The landing was on July 20, 1969. Apollo 11 was launched on July 16, 1969. Astronauts Neil Armstrong and Buzz Aldrin conducted the first lunar exploration for about 2.5 hours by leaving the “Eagle,” which had landed in the Sea of Tranquility. Meanwhile, Michael Collins stayed in orbit around the Moon in the Apollo Command Module.
APOLLO-SOYUZ: A joint U.S.-Russian mission from July 15 to July 24, 1975. Apollo, the three-man U.S. spacecraft, consisted of the Command Module (CM) connected to the Service Module (SM) and the docking module (DM). For two days, the CM/DM was docked with Soyuz, the two-man Russian spacecraft. The two spacecraft were in a circular orbit inclined 51.8 degrees to the equator, with a 93-minute period, 222 kilometers (138 miles) above Earth’s surface.
APOLLO SPACECRAFT: A three-man spacecraft launched by Saturn boosters, originally designed for trips to the Moon.
Asteroid: A small object that fits the definition of a planet but, it is considered too small to be called one. Astronomers prefer the terms planetoid (planet-like) or planetesimal (tiny-planet).
ASTRONAUT: One who flies, or is trained to fly, above the atmosphere.
ATMOSPHERE: An envelope of gases that surrounds a planet.
ATTITUDE: The position of the spacecraft as determined by the inclination (tilt) of its axes to some frame of reference.
AUTO-SEQUENCER: Computer controller of the countdown. At T-minus 31 seconds the Flight Director switches total control of the launch over to the auto-sequencer.
AUTOLAND GUIDANCE: A computer-generated microwave system that aids in landing the Shuttle.
AUXILIARY STAGE: A small propulsion unit used with a payload when required. One or more of these units may be used with a payload to provide the additional velocity required to place a payload in the desired orbit or trajectory. Also, a propulsion system that is used to provide midcourse trajectory corrections, braking maneuvers, and/or orbital adjustments.
AXIS: Any of three mutually perpendicular straight lines, the first running through the center of the fuselage lengthwise, the second at right angles to the first and parallel to the horizontal airfoils, and the third perpendicular to the first two at their point of intersection.
AZIMUTH: True launch heading measured clockwise from zero degrees north.

[ B ]

BACK-UP CREW: A crew that has received identical training as the prime crew in case the latter should suffer injury or illness before launch. This crew is to be available for flights on short notice.
BAKER, MISS: Squirrel monkeynaut that flew on a Jupiter rocket on May 28, 1959. Miss Baker helped pave the way for men and women to fly in space. She died in November 1985, and is buried in front of the U.S. Space and Rocket Center in Huntsville, Alabama.
BEARING: The compass direction in which the orbiter is traveling.
BETA ANGLE: Minimum angle between the Earth-Sun line and the plane of an orbit.
BIOSPHERE: The part of Earth and its atmosphere in which animals and plants live.
BOOSTER: An engine that assists the normal propulsion system of a vehicle or other systems of a vehicle.
BURNOUT: The moment at which combustion ceases in a rocket engine.

[ C ]

C&W: Caution and Warning. This system provides the crew with cues about malfunctioning systems or equipment.
CRT (CATHODE RAY TUBE): A vacuum tube in which a hot cathode emits electrons that are accelerated as a beam through a relatively high voltage anode, further focused or deflected electrostatically or electromagnetically, and allowed to fall on a fluorescent screen ( a televison screen). The orbiter has four CRTs that display information to the crew.
CALL TO STATION: The point when all personnel are required to be in place for the countdown prior to launch; in our simulation it happens only a few minutes before lift-off.
CAPSULE: A small pressurized cabin with an acceptable environment, usually for containing a man or an animal for extremely high-altitude flights, orbital space flight, or emergency escape.
CARGO: The total complement of payload (one or more) on any one flight. It includes everything contained in the orbiter cargo bay plus other equipment, hardware, and consumables located elsewhere in the orbiter that are user-unique and are not carried as part of the basic payload support.
CARGO BAY: The unpressurized middle part of the orbiter fuselage, beginning with the cabin aft bulkhead where most payloads are carried. Its maximum usable payload envelope is 4.6 meters (15 feet) in diameter and 18.3 meters (60 feet) long.
CENTRIFUGAL FORCE: A fictitious force that is directed away from the center of rotation. The sensation of centrifugal force is actually the result of a body's inertia.
CENTRIFUGE: A large motor-driven apparatus used to produce centrifugal force by spinning rapidly.
CENTRIPETAL FORCE: A force which is directed toward the center of rotation.
COMMANDER: This crewmember has ultimate responsibility for the safety of embarked personnel and has authority throughout the flight to deviate from the flight plan, procedures, and personnel assignments as necessary to preserve crew safety or vehicle integrity. The commander is also responsible for the overall execution of the flight plan in compliance with NASA policy, mission rules, and Mission Control Center directives.
CONSTELLATION: Any one of the arbitrarily identified groups of fixed stars, 88 of which are officially recognized. A division of the heavens in terms of any one of these groups.
CONSUMABLES: The food, water, gas, propellant, etc., that are used during a Shuttle mission or any activity.
Cosmology: The study of the origin, stucture, processes, and space-time relationships of the universe.
CROSSWIND: A condition where winds are blowing across the runway instead of along it. Strong crosswinds pose a hazard for Shuttle landings since the orbiter has no power of its own to fly, and last minute course corrections on landings are difficult.
CRAWLER: The huge motorized vehicle used to transport a Shuttle stack from the VAB to the launch pad - very slowly.
CUE CARD: These are small cards with procedures for the Shuttle activities written on them as a reminder and a checklist for the crew. Cue cards are used by the commander and pilot for launch, landing, and inflight maneuvers, and by the rest of the crew for each of their specialized activities.

[ D ]

DAP: Digital Auto Pilot. An automatic system used to maintain a specific course or altitude on orbit.
DDU: Digital Display Unit. Computer in Spacelab that is used to control and update experiments.
DEORBIT BURN: An OMS burn to slow the Shuttle for re-entry. Fired in the direction in which the orbiter is traveling.
DEPLOYMENT: The process of removing a payload from a stowed or berthed position in the cargo bay and releasing that payload to a position free of the orbiter. Also, to place into operation the RMS or radiators.
DEPRESS OR DEPRESSURIZE: The act of releasing the atmosphere out of a container. Usually it refers to preparations to open an airlock prior to an EVA.
DOCK/UNDOCK: The process of attaching to or detaching from another object in space, most often a space station or other spacecraft.
DOCKING MODULE: A special component added to a spacecraft to allow it to join or dock with another spacecraft in space (e.g., Apollo-Soyuz, Shuttle-Space Station)
DOFF: To take off (space suit)
DON: To put on (space suit).
DOWNRANGE: Ahead of the spacecraft in the flight path.

[ E ]

EMU

The Extravehicular Mobility Unit (space suit) is a self-contained life support system (no umbilicals) and anthropomorphic pressure garment for use by crewmembers during extravehicular activities. It provides thermal, micrometeoroid, and radiation protection.

ESA

The European Space Agency, an international space organization acting on behalf of its member states: Austria, Belgium, Denmark, France, Germany, Ireland, Italy, the Netherlands, Norway, Spain, Sweden, Switzerland, and the United Kingdom. (Finland is an associate member, and Canada is a cooperating state.) ESA directs a European industrial team responsible for the development and manufacture of Spacelab.

The External Tank of the Shuttle that carries liquid oxygen and liquid hydrogen for the main engines during launch and ascent.

ET SEP

External Tank separation. The point after main engine cutoff where the External Tank is released from the orbiter; the giant tank then tumbles into the atmosphere and burns up.

EVA

Extravehicular Activity. A common NASA term for spacewalks and other journeys outside the protection of the spacecraft.

EGRESS

To exit, as from a spacecraft.

ESCAPE VELOCITY

The speed a body must attain to overcome a gravitational field, such as that of Earth; the velocity of escape at Earth’s surface is 11.2 kilometers (7 miles) per second.

EXEC OR [EXEC]

Execute. A word or symbol for pressing a button marked [EXEC] to initiate a program on the onboard computer.

EXTRAVEHICULAR

Indicates a location outside the vehicle; may be used to describe elements or activities.

[ F ]

FPS

Feet Per Second. Used to describe the motion or speed of the orbiter moving in relation to another object or the ground. May be indicated in metric units as meters or kilometers per second.

FSS

Fixed Service Structure. The gantry mounted permanently at the launch pad.

5 DF (FIVE D-F)

Five degrees of freedom. A device the helps simulate weightlessness. In simulated missions, the astronauts will often work inside a 5DF during EVAs.

FLARE

Pitching the orbiter nose up before landing. This maneuver helps change the glide slope from 22º to less than 2º.

FLIGHT CONTROL SYSTEM

A system that serves to maintain attitude stability and control during flight.

FLIGHT DIRECTOR

The individual on the ground who is in charge in Mission Control. (A Flight Director relays orders to the Commander, but the Commander can refuse these orders if he considers them a danger to his spacecraft.)

FLIGHT KIT

Optional hardware (including consumables) to provide additional, special, or extended services to payloads. Kits are packaged in such a way that they can be installed and removed easily.

FORWARD PROPELLANTS

Fuel and oxidizer for the RCS engines in the forward fuselage used to produce thrust.

FREE-FLIGHT ROCKET

A rocket without electronic control or guidance.

FUEL CELL

An electromechanical generator in which the chemical energy from the reaction of oxygen and hydrogen is converted directly into electricity and water.

FULL FLARE

Pitching the nose of the orbiter up just before touchdown to allow the main landing gear to touch first.

FULL STOP

This call comes from the Landing Director meaning that the orbiter has completely stopped moving after touchdown.

Fusion

The uniting of atomic nuclei to form heavier nuclei which results in the release of tremendous amounts of energy.

[ G ]

G (OR G-FORCE): Force exerted upon an object by gravity, or by reaction to acceleration or deceleration, as in a change in speed or direction; one G is the measure of the gravitational pull required to accelerate a freely-falling body at the rate of 9.8 meters per second squared (32.16 feet per second squared).
GPC: General Purpose Computer. These computers provide control for the Shuttle, and in some cases, payloads.
GALAXY: (1) The vast assemblage (group) of stars, star clusters, nebulae, etc., to which the Earth’s sun belongs; (2) Any of the many similar groups of stars forming isolated units in the universe; (3) A closed gravitational system of stars and their satellites, nebulae, and dust that is both spinning and traveling through space.
GEAR: (1) The landing gear of the orbiter; (2) Equipment used in experiments or other activities.
GLIDE SLOPE: The angle of the Shuttle’s descent to Earth during final approach.
GO: A term granting permission to proceed with an activity; also used to signify that a system is operating normally.
GRAVITATION: Force of attraction that exists between all particles of matter everywhere in the universe.
GRAVITY: The force which tends to pull bodies toward their center of mass; that is, to give bodies weight; i.e., the mutual attraction between any two or more bodies by virtue of their mass.
GREEN: A term meaning that conditions are good or acceptable.
GUIDANCE SYSTEM: A system which measures and evaluates flight information, correlates this with target data, converts the results into the conditions necessary to achieve the desired flight path, and communicates this data in the form of commands to the flight control system.
GYROSCOPE: A device consisting of a wheel so mounted that its spinning axis is free to rotate; once set in rotation, its axis will maintain constant direction, even when Earth is turning underneath. When its axis is pointed due north, it may be used as a gyro compass.

[ H ]

H2 (“H” TWO): Molecular Hydrogen. It is used in liquid form (LH2) to power the main engines and the power generators (fuel cells) on the Shuttle.
HEAT TILE: A tile specially made to protect the Space Shuttle orbiter and crew from the heat of re-entry into Earth’s atmosphere. Its primary ingredient is silica fiber. The tile can withstand repeated heating and cooling, possibly for as many as 100 space flights without replacement.
HOLOGRAM: A 3-D image produced by a laser.
HOOD: Cover that protects satellites from direct sunlight. They are opened and closed by mission specialists during deployment.
HYDRAULIC PRESSURE: Liquid pressure produced by the APUs used to power the landing gear and aerodynamic control surfaces on the orbiter on launch and landing. Also used to gimbal the main engines and SRB nozzles (separate hydraulic power units are used for the SRBnozzles). If pressure is too low, the equipment will not swivel properly.
HYDRAZINE(Monomethyl Hydrazine): Fuel used by OMS and RCS engines. Also used to power the APUs.

[ I ]

IUS: Inertial Upper Stage. Solid propulsive stage designed to place spacecraft in high-Earth orbits and on deep space missions (such as the Magellan Probe).
IVA: Intravehicular Activity. Work and operations performed inside the spacecraft.
IGNITION: The moment when an engine or rocket starts combustion.
INCLINATION: The angle of an orbit relative to the equator; more properly, the angle between the plane of the orbit and the equatorial plane.
INERTIA: The tendency of an object at rest to stay at rest; and if moving to continue moving.
INGRESS: To enter something, such as a spacecraft.
IONIZATION: The buildup of ions around the orbiter as it re-enters Earth’s atmosphere. Often an orange-red glow is seen around the Shuttle as the ionization buildup occurs.
IONIZATION BLACKOUT: When ionization builds up, it can block out all radio communication with the orbiter causing a temporary LOS. This is no longer a problem for the Shuttle crew because of TDRSS.
ITEM OR [ITEM]: A word or symbol for a function in a computer program. Each item, when entered into the keypad, will produce a special action.

[ J ]

JPL: The NASA Jet Propulsion Laboratory near Pasadena, California.
JSC: The NASA Lyndon B. Johnson Space Center in Houston, Texas.
JOYSTICK: Either of the controls in front of the commander and pilot (or at the aft flight station) used to maneuver the orbiter. Only one astronaut can control the joystick at a time. Technically known as the rotational hand controller (RHC). Named for its inventor, British Flt. Ltnt. Rupert Joyce.

[ K ]

KSC: The NASA John F. Kennedy Space Center in Cape Canaveral, Florida.
KEYPAD: The computer keyboard used to enter programs and accompanying items into the flight computers.

[ L ]

LDEF: Long Duration Exposure Facility. A free-flying payload (satellite) used to test the effects of long-term space exposure on various materials. It stayed in orbit for almost six years before being retrieved by the crew of STS-32 (1990).
LAUNCH CONTROL: The room where the launch is supervised. Generally this is a separate facility from Mission Control (JSC), located either at Kennedy Space Center or at Vandenberg Air Force Base. In our simulations, both Mission Control and Launch Control are in the same room.
LAUNCH PAD: The area at which the stacked Space Shuttle undergoes final pre-launch checkout and countdown, and from where it is launched.
LAUNCH WINDOW: A specific time frame during which a rocket or satellite must be launched in order to achieve the desired orbital position.
LIFTOFF: The moment in the launch where the Space Shuttle begins moving up off the launch pad.
LIGHT YEAR: Distance travelled in one year by light, which covers 299,728 kilometers (186,282 miles) in one second; equal to 5.88 trillion miles.
LOAD: (1) The process of putting a program into a computer; (2) The process of placing fuel into a rocket's tanks.
LOS: Loss of Signal. This occurs when the orbiting spacecraft moves out of range of Earth-based or space-based communications. (This interruption in mission communications occurs briefly when the orbiter is over the Indian Ocean.) With the addition of TDRSS, the amount of LOS during a typical mission has been greatly reduced. LOS also occurs, due to ionization blackout, upon re-entry.
LOX: Liquid Oxygen. Used as an oxidizer for the orbiter’s three main engines and stored in the ET (-298º F). Also used as a reactant for the orbiter's fuel cells.
LUNAR BASE: A proposed installation on the surface of the Moon for use as a base in scientific or military operations.
LUNAR GRAVITY: The attraction of particles and masses towards the gravitational center of the Moon, about one sixth of Earth's gravitational pull.
LUNAR ROVER: A vehicle used by Apollo 15, 16, and 17 astronauts. This vehicle enabled astronauts to explore a much greater area on the Moon.

[ M ]

MET: Mission Elapsed Time. The running time from lift-off through the entire mission. During simulated missions, MET is used as a guide to perform duties at the right time.
MMU: Manned Maneuvering Unit. A personal spacecraft (gas-powered backpack) that can be used to catch disabled satellites and move astronauts around to make untethered repairs from the spacecraft.
MSFC: The NASA George C. Marshall Space Flight Center in Huntsville, Alabama.
MACH (1, 2, 3, etc.): Mach 1 is the speed of sound; Mach 2 is double the speed of sound; Mach 3 is triple, etc.
MAINS: Short for three main engines which are used to help propel the orbiter into space.
MANEUVER: Moving the spacecraft or another object.
MARSHALL OPERATIONS/OPS: The ground operations for a Spacelab mission, controlled by the Marshall Space Flight Center.
MASS: A measure of the quantity of matter in a body. This is a fundamental property that (at slow speeds) does not change. (However, a rocket loses mass as its propellant is consumed, causing its acceleration to increase.)
MAX Q: Period of maximum aerodynamic pressure on the Shuttle during a typical launch.
Mastif: Multiple-Axis Space Test Inertia Facility.
MECO: Main Engine Cut-Off. This occurs when the orbiter is at the right altitude and is travelling fast enough to achieve orbit.
METEOROID: A solid particle of matter travelling in space at a considerable speed.
MISSION: The performance of a coherent set of investigations or operations in space to achieve program goals. A single mission might require more than one flight, or more than one mission might be accomplished on a single flight.
MISSION CONTROL: The center where all operations of the orbiter are coordinated during the mission. It is located at JSC (Houston), for most missions, and at MSFC for Spacelab missions.
MISSION SPECIALIST: This crewmember is responsible for coordination of overall payload/STS interaction and, during the payload operations phase, directs the allocation of the STS and crew resources for the accomplishment of the combined payload objectives. The Mission Specialist has prime responsibility for experiments to which no payload specialist is assigned, and/or assists the payload specialist when appropriate. May also assist with navigation and satellite deployment and perform EVAs.
MODULE: A separate unit of the spacecraft or space station, usually pressurized (command module, Spacelab, etc.).
MOON: An object that orbits a planet and reflects the light of a star. The celestial body that orbits as a natural satellite above the Earth, revolving around it once every 29 1/2 days, and reflecting sunlight. The Moon’s average distance from Earth is 384,321 kilometers (238,857 miles) and its diameter is 3,476 kilometers (2,160 miles). The Moon has a mass and a volume of about 1/81 and 1/49 that of Earth, respectively.

[ N ]

NASA: National Aeronautics and Space Administration. Headquarters are located in Washington, DC.
NAUTICAL MILE (NM): Used to measure distance traveled by a spacecraft. Equal to 1,853.2 meters (6,080 feet or 1.15 statute miles). Defined as the length of one minute of arc on Earth’s surface.
Nebula: A cloud of gases and dust in space.
NEUTRAL BUOYANCY: The state of neither rising nor sinking when in a fluid.
NOSE CONE: The shield that fits over, or is, the nose of a spacecraft.

[ O ]

O2 (OH-TWO): Oxygen.
OMS(RHYMES WITH HOMES): Orbital Maneuvering System. The two engines on the orbiter used to lower or raise its orbit during a mission. It is also used to slow the orbiter down for re-entry.
OPF: Orbiter Processing Facility. Hangar-like building at KSC where orbiters are serviced prior to flight.
ONE-G (1-G): The downward acceleration of gravity at Earth’s surface: 9.81 meters per second squared (32.2 feet per second squared).
ORBIT: The path or trajectory followed by a moving object in a gravitational field. It may be incomplete, as for a model rocket; closed, as for an orbiting moon or Shuttle; or open, as in a gravity-assist maneuver.
ORBITAL INSERTION: Entering the desired orbit.
ORBITER: An airplane-like spacecraft that has the capability of going into space like a rocket and landing like an airplane.
“OTHER SIDE OF THE HILL” or "OVER THE HILL": An expression used for describing the acquisition of signal after loss of signal.
OZONE LAYER: Layer of heavy oxygen in Earth’s atmosphere, about 32 kilometers (20 miles) above sea level, that strongly absorbs ultraviolet radiation.

[ P ]

PAM: Payload Assist Module. A solid propulsion stage designed to place a spacecraft into a high Earth orbit.
POCC: Payload Operations Control Center. Control center for Spacelab payloads.
PSIA: Pounds per square inch atmospheric. A measurement of liquid pressure used to tell how much fuel or other material is used or stored when volume and temperature are known. The metric equivalent is the kiloPascal (kPa).
PALLET: An unpressurized platform designed for installation in the orbiter payload bay, used for mounting experiments and equipment requiring direct space exposure. Can be a portion of Spacelab.
PAYLOAD: The total complement of instruments, space equipment, support hardware, and consumables carried in the orbiter to accomplish a specific activity in space.
PAYLOAD SPECIALIST: This crewmember, who is not a career astronaut, is responsible for the operation and management of the experiments or other payload elements that are assigned to him or her, and for the achievement of their objectives. The payload specialist is an expert in experiment design and operation.
PERIGEE: The lowest point of an Earth orbit; the point of any orbit closest to Earth’s center.
PILOT: This crewmember is second in command of the flight and assists the commander as required in the conduct of all phases of orbiter flight.
PITCH: Up/Down rotation of the nose of the craft.
Planet: A relatively large, spheroidal object that orbits a star and reflects the light of a star.
POWER UP/DOWN: Terms used to describe activation or deactivation of equipment and instruments.
PRESS OR PRESSURIZE: The act of allowing a vacuum to fill with air, such as an airlock, when an EVA is completed.
PRESS TO MECO: This is the call from Mission Control to the Shuttle telling the crew they can continue main engine cut-off, even if one or two of the main engines fail.
PRINCIPAL INVESTIGATOR (PI): The lead scientist in charge of the development of a space experiment and the analysis and report of the results; usually does not fly.
PRO or [PRO]: A word or symbol describing the key punched to enter a specific program into the onboard computer; means proceed.
PROBE: A device used in docking and landing as a guide and latching mechanism. It engages with a hollow drogue to facilitate mating of two spacecraft.
PROPULSION: The act of driving forward or propelling; to give an impulse or push. In the case of a rocket, the propulsion is provided by the rocket engine in accordance with Newton's Law of Action and Reaction.
Pulsar: A rapidly rotating neutron star which emits radio waves; one of the possible remnants of a dying giant star.

[ R ]

RCS: Reaction Control System. This is a series of 44 thrusters in various locations around the orbiter, used for maneuvering in space.
RMS: Remote Manipulator System. The robot arm on the Shuttle, also known as the Canadarm.
RSS: Rotating Service Structure. A movable, protective structure attached to the FSS. Provides protection and access to the orbiter payload bay.
RTLS: Return-to Launch-Site Abort. A mode of launch abort that requires a 180º turn around and return to the launch site for landing.
RADIO COMMAND: A radio signal to which a guided missile, drone, etc., responds.
RADIO TELESCOPE: A radio receiving station for detecting radio waves emitted by celestial bodies or by probes (telemetry) in space.
RANGE: The horizontal distance between two objects. In the Shuttle program, it is used to describe the ground distance of the orbiter from the launch pad after lift-off and also to describe the distance between the orbiter and other objects such as the Space Station.
REACTION: Involving chemicals, a change that occurs when thechemical’s state is altered, usually upon exposure to energy, or when combined with a different chemical.
RE-ENTRY: The return of a spacecraft through the atmosphere after a space flight.
REHYDRATABLE FOOD: Dehydrated food that is prepared for consumption by adding water.
RENDEZVOUS: Two objects brought into the immediate vicinity of each other (e.g., CSM to Skylab).
RETRIEVAL: The process of utilizing the remote manipulator system (RMS), and/or other handling aids, to capture and return a payload to a stowed or berthed position. No payload is considered retrieved until it is fully stowed for safe return, or berthed for repair and maintenance tasks.
RETROROCKET: A rocket engine that gives thrust in a direction opposite to the direction of the object’s motion.
REVERSE THRUST: Thrust applied to a moving object in a direction opposite to the direction of the object’s motion.
ROBOTICS: The study and application of the use of robots. Robotics is growing into a major scientific application for the immediate future.
ROCKET: A projectile, pyrotechnic device, or flying vehicle, propelled by one or more liquid or solid propellant engines. NASA normally refers to their rockets as launch vehicles, to emphasize peaceful purposes. The Department of Defense calls its rockets missiles, since they are directed at the enemy.
ROCKET ENGINE: A reaction engine that contains within itself all the hardware necessary for its operation or combustion of its propellants, not requiring intake of any outside substances such as air or oxygen.
ROGER: A word used to confirm that the message has been received and understood.
ROLL: Rotation around the X-axis from nose to tail.

[ S ]

STS: The Space Transportation System. An integrated system consisting of the Space Shuttle, upper stages, Spacelab, launch and landing facilities, and any associated flight hardware or software.
S-TURN: A roll maneuver performed during atmospheric entry to help slow the orbiter before landing. It also helps cool the tiles.
SAFE/SAFING: The process of neutralizing any dangerous and/or explosive gases around the orbiter after touchdown, to ensure the crew’s safety.
SATURN V: The giant launch vehicle that propelled the Apollo three-man crews to lunar orbit. The Saturn V is 111 meters (363 feet) high and weighs, at lift-off, more than 2,721,600 kilograms (6 million pounds), requiring a take-off thrust of 33.84 million Newtons (7.6 million pounds). It consists of three propulsive stages.
SCRUB: To cancel a scheduled launch either before or during the countdown.
SIDEREAL: Having to do with the stars; using the stars as a frame of reference. A sidereal day, for example, is the time it takes Earth to make a complete rotation about its axis with respect to the stars. The Moon’s sidereal period of revolution about Earth is 27.3 days.
SIMULATOR: Any device used to simulate or approximate the sensation of movement and control capability for an aircraft or spacecraft.
SKYLAB: A large space workshop that NASA put into orbit on May 14, 1973. It was visited by three astronaut crews of three people each, who worked on scientific experiments in space for a total of 171 days (the last crew for 84 days).
SOLAR ARRAY: Solar cells wired and mounted into an array to provide electrical power to the spacecraft, using energy from the Sun.
SOLAR CELL: A small “sandwich” unit for converting light to electrical energy.
SOLAR DISC: The entire visible surface of the Sun .
SOLAR LIMB: The edge of the Sun’s disc. It appears less bright than the central regions (limb darkening).
SOUNDING ROCKET: A scientific research rocket used to obtain data on the upper atmosphere or to carry a science instrument above the atmosphere.
SPACE BIOLOGY: A branch of biology concerned with life as it may have come to exist in the universe; also called “exobiology.”
SPACE SHUTTLE: A reusable spacecraft consisting of the orbiter, External Tank, and two solid rocket boosters.
SPACELAB: A flexible laboratory system that features several interchangeable elements (modules and pallets) that can be put together in a variety configurations to meet the particular needs of a given mission.
SPEED BRAKE: The rudder on the orbiter is split down the middle and when the speed brake is activated, the two halves fan out to help slow the spacecraft with extra drag during the landing approach.
SPINOFF: An unexpected benefit that is developed as a result of space research.
SRB: Solid Rocket Booster. Each of two slender rockets, attached to the side of the external tank, that give the Shuttle immediate power for lift-off and first stage ascent. They exhaust all of their solid propellant in about two minutes.
SRB SEP: The moment in the launch where the boosters separate from the rest of the Shuttle. They then parachute back to Earth and are recovered in the ocean, to be reused.
SSME: Space Shuttle Main Engine. The orbiter has three main engines that burn liquid hydrogen and liquid oxygen from the ET.
Star: A luminous ball of gases which generates heat and light by the process of nuclear fusion.
STOW/UNSTOW: The act of taking out or putting away gear or equipment.
STRATOSPHERE: A calm region of the upper atmosphere characterized by little or no temperature change with changes in altitude.

[ T ]

TAL (RHYMES WITH PAL): Trans-oceanic Abort Landing. This is an abort procedure used when it is no longer possible to return to the launch site (RTLS), but the Shuttle has sufficient altitude and speed to make it to Africa or Europe.
TDRSS (TEE-DRESS): Tracking and Data Relay Satellite System. NASA’s current link for communications and space travel. Using TDRSS, most Shuttle flights are in constant contact with the ground more than 80 percent of the time in orbit.
TELEMETRY: A system for taking measurements in the spacecraft or satellites and transmitting them to ground stations.
THROTTLE (UP/DOWN): The procedure of increasing/decreasing the power output of the Shuttle’s three main engines during Max Q. Typical engines range between 65 and 109 percent rated power. They are reduced at Mach 1 and brought back up again until just before MECO. They are controlled by the onboard computers.
TRAJECTORY: The path of a spacecraft or rocket during ascent, orbit, or landing.

[ U ]

UMBILICAL LINE: A cable fitted to a vehicle with a quick-disconnect plug, through which electrical power, oxygen, etc., is transmitted.
Universe: The entire celestial cosmos which is an orderly and harmonious system, but also characterized by extremely violent events such as supernova explosions.

[ V ]

VAB: Vehicle Assembly Building. A large building where ET/SRB/orbiter stacking is done prior to movement of the assembled Shuttle to the launch pad.
VAN ALLEN RADIATION BELTS: Two doughnut-shaped belts of high energy particles (protons and electrons), trapped in Earth’s magnetic field, that surround Earth. They were first reported by Dr. James A. Van Allen of the University of Iowa using data from the Explorer 1 satellite.
VELCRO: Space-age material used plentifully inside spacecraft to secure objects, especially cue cards, in microgravity.
VELOCITY: Distance traveled per unit of time.
VON BRAUN, WERNHER: Famous rocket pioneer who was the leader of the rocket team responsible for the development of America’s space program. This group of scientists grew into one of the most influential technological forces of the century. In a ten-year period, Dr. Von Braun and his team developed and built the huge Saturn rocket that sent man to the Moon.

[ W ]

WEIGHT: A measure of how strong the force of gravity pulls on a body. This property varies depending on the distance from the attracting body.
WEIGHTLESSNESS: A state or condition in which the pull of gravity is effectively neutralized, as when a body undergoes free fall. When in orbit, gravity is countered by a spacecraft’s forward momentum (inertia), resulting in continual free fall and weightlessness. See ZERO-G.
WALLOPS ISLAND: A NASA installation on the Virginia coast used for satellite tracking and sounding rocket launches.
WORK STATION: A facility or functional area where organizational level operations and maintenance tasks are performed in direct support of a turnaround cycle, or where intermediate and depot level maintenance tasks on the Shuttle are performed.

[ Y ]

YAW: The sideways rotation of the spacecraft on an axis going vertically through the middle of the ship.

[ Z ]

ZERO-G: The condition of free fall or weightlessness. When there are no forces on objects in a spacecraft, they are said to be in zero-g (actually microgravity).

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