Space Acronyms & Terms

Following up on my reading list from last week, I thought I’d share some of the most common acronyms one sees/hears in the engineering world. Some of these are also used in other disciplines besides aerospace. Understanding the acronyms is often half the battle when it comes to “speaking geek.” I quickly became Keeper of the Acronyms wherever I went because I kept solid lists of what these things meant. It’s not just a job, it’s an adventure!

Note: The following items are known by saying the individual letters in their acronyms aloud unless otherwise noted.

Additional Note: These terms concentrate on the organizations and hardware used to performing activities in space vs. what’s actually in space (planetary science, solar science, astronomy, etc.). I work primarily with engineers and government bureaucracy, not scientists.

ASI – Italian Space Agency (in Italian, Agenzia Spaziale Italiana, pronounced AH-zee) – Italy’s civilian space agency

CDR – Critical Design Review – Final design review before an organization begins manufacturing an engineered product

CFD – Computational Fluid Dynamics – A mathematical and graphical discipline used to study and predict how air or other fluids move in and around machinery

Commercial Space – Space launch, ground operations, and space operations activities performed by and for for-profit businesses (as opposed to government or military purposes)

Continuing Resolution – A temporary or year-long budget passed by the U.S. Congress that continues to fund the entire government (or part of it) at the same levels as the previous year; usually passed when major changes could not be agreed upon by the members

Control Surfaces – Wings, fins, ailerons, or other aerodynamic surfaces used to control or stabilize a vehicle’s path through the atmosphere; not useful in space due to the lack of air

CSM – Command and Service Module – Spacecraft used to transport astronauts to and from the Moon during the Apollo program, remained in orbit during the landing phase

CNES – National Centre for Space Studies (in French, Centre national d’études spatiales pronounced KuhNESS) – Civilian space agency of France

CNSA – China National Space Administration – China’s space agency

Cryogenic – Solid, liquid, or gas super-cooled below −150 °Celsius (−238 °Fahrenheit); hydrogen, oxygen, or methane gases are refrigerated down to cryogenic temperatures to condense them into liquid form for higher energy density and easier handling/pumping in liquid-fuel rocket engines

Delta-V (also ∆v, pronounced “DEL-ta VEE”) – A change in a spacecraft’s velocity; usually expressed in meters per second (how fast and in what direction acceleration occurs), but since engines or thrusters are the primary means of changing a spacecraft’s velocity, ∆V is sometimes used as a synonym for propellant

ECB – Engineering Change Board – Committee assigned to review and approve design changes (related acronym: ERB/Engineering Review Board)

ECLSS – Environmental Control and Life Support System (pronounced “EE-cliss”) – System designed to provide breathable air and potable water for astronauts in space

EDL – Entry, Descent, and Landing – Set of activities used to bring a spacecraft from orbit down to the surface of another planet, usually (but not always) with an atmosphere

ELV/EELV – Expendable Launch Vehicle/Evolved Expendable Launch Vehicle – Multi-stage rocket system where stages are burned up/expended and dropped/crashed back on Earth after use; the U.S. Air Force has used the EELV Program to launch military, NASA, and other spacecraft since 1990

Engine – Rocket propulsion system powered by liquid propellants; differentiated from rocket motors by having valves and other safety systems that can regulate or stop thrust

EOR – Earth Orbit Rendezvous – Mission architecture that uses several launches of spacecraft and other hardware and docks or assembles them in Earth orbit before proceeding to another destination (usually the Moon)

ERV – Earth Return Vehicle – Spacecraft designed to carry astronauts to Earth from another destination in the solar system; might or might not be the same vehicle used to land on the exploratory destination

ESA – European Space Agency (pronounced EE-za) – Intergovernmental civilian space agency based in Europe, comprising 22 member nations

EVA – Extravehicular Activity – Technical for a “spacewalk” or any activity that requires an astronaut to put on a spacesuit and leave a space station, vehicle, or habitat

FRR – Flight Readiness Review – Formal review/meeting where a launch vehicle and its payload are evaluated for their suitability to fly; often conducted the day before a launch

GEO – Geosynchronous Orbit (pronounced JEE-oh) – Circular or elliptical paths spacecraft follow around 36,000 kilometers (22,300 miles) above Earth’s surface; spacecraft/satellites in this orbit are situated over the Equator and complete their orbit in one Earth day, keeping them stationary in the sky (also called geostationary orbit)

GPO – Government Publishing Office – United States Government agency responsible for setting standards for and printing hard-copy documents; maintains the GPO Style Manual

Inclination – Angle at which a spacecraft’s orbit intersects the Equator; high-inclination orbits (>70 degrees) are often used to observe or provide telecommunication services to high-latitude parts of the Earth (e.g. the Poles)

ISRO – Indian Space Research Organization (pronounced IZ-roe) – India’s civilian space agency

ITU – International Telecommunications Union – United Nations organization responsible for coordinating the use of information and communication technologies; plays a role in space by governing the use of electromagnetic spectrum (radio frequencies) by spacecraft, telescopes, and other hardware

JAXA – Japan Aerospace Exploration Agency (pronounced JACK-sah) – Japan’s national civilian space agency

Lander – Spacecraft designed to land on the surface of a celestial body besides Earth

LEO – Low Earth Orbit (pronounced LEE-oh) – Circular or elliptical paths spacecraft follow 160 to 2,000 kilometers (100-1,240 miles) above Earth’s surface

LH2 – Liquid Hydrogen – Cryogenic fuel used in liquid-fuel rockets

LM – Lunar Module (pronounced “LEM”) – Spacecraft used to land astronauts on the Moon during the Apollo program

LO2 – Liquid Oxygen (also LOX, pronounced LOCKS) – Cryogenic oxidizer used to sustain fuel combustion in liquid-fuel rocket engines

LCH4 – Liquid Methane (also LNG, Liquefied Natural Gas) – Cryogenic fuel used to power liquid-fuel rocket engines

LOR – Lunar Orbit Rendezvous – Mission architecture that uses a single “stack” of spacecraft to reach the Moon but uses only part of that stack to land on and return to lunar orbit, with the rest of the stack remaining in orbit

LV – Launch Vehicle – Rocket used to launch payloads into Earth orbit or beyond (as opposed to a missile, which is usually suborbital and designed to impact a payload/warhead onto a specific target on Earth)

MEO – Medium Earth Orbit (pronounced MEE-oh) – Circular or elliptical paths spacecraft follow 2,000 to 36,000 kilometers (1,240 to 22,300 miles) above Earth’s surface

Mission Creep – A gradual expansion of the activities performed requirements demanded of program, vehicle, or specific use of a vehicle

Motor – Rocket propulsion system powered by solid propellants; differentiated from an “engine” by having few moving parts to produce thrust; once most solid motors are fired,  they cannot be shut off

NASA – National Aeronautics and Space Administration (pronounced NAH-sa) – The United States’ government civilian space agency; for more details on NASA, see here and here

NOAA – National Oceanographic and Atmospheric Administration (pronounced NO-ah) – U.S. Government agency responsible for monitoring natural conditions in Earth’s oceans and atmosphere; often charged with developing (sometimes in cooperation with NASA) Earth observation satellites

Orbit – A curved, repeating path (trajectory) followed by one object around another (usually larger) object determined by gravity; the radius of an orbit is determined by a number of factors, including the relative size and density of the objects

OMS – Orbital Maneuvering System (pronounced OHMS) – Small rocket engines/thrusters used to raise or lower a spacecraft’s orbit

PBAN – Polybutadiene Acrylonitrile (pronounced polly-BYOU-ta-deen ah-crill-o-NIGH-trial) – Solid, rubber-like material mixed with aluminum powder fuel, ammonium perchlorate oxidizer, and other materials used in solid rocket motors (esp. the Space Shuttle and Space Launch System SRBs)

PDR – Preliminary Design Review – Early-phase design review used to evaluate whether the design of an engineered product will meet its mission requirements

Personal Spaceflight – Another name for space tourism, i.e., private citizens visiting suborbital, orbital, or other parts of space for personal experience as opposed to advancing mission objectives of a nation or business

Propellant – Energetic mixture used to produce thrust, a liquid or solid fuel combined with oxidizer to enable combustion/burning in the vacuum of space; liquid fuel and oxidizer are mixed through a series of pumps and valves; solid propellants are a premixed material containing both fuel and oxidizer

Range – Designated space on Earth over and through which rockets bound for space are launched; scheduled in advance to inform the general public (especially commercial air and shipping traffic) that it will be cleared of unauthorized personnel, ground vehicles, and ships prior to and during any launch attempt; U.S. launch ranges are usually enforced by the Department of Defense (Air Force, Navy, or Coast Guard)

RCS – Reaction Control System – Smaller set of thrusters used by spacecraft to perform fine-tuning a spacecraft’s orientation once in orbit (e.g., imparting or dampening out spin)

RF – Radio Frequency – Specific electromagnetic wavelength used by a spacecraft to receive/transmit commands, data, voice, or video

RLV – Reusable Launch Vehicle – Rocket which has one or more stages capable of soft-landing on Earth (or remaining in orbit) to be reused after flight

Roscosmos State Corporation for Space Activities (pronounced ross-KOZ-mose) – Russia’s civilian space agency

RP-1 – Rocket Propellant One – Refined form of kerosene fuel used to power liquid-fuel rocket engines

SE&I/SEI – Systems Engineering and Integration – Engineering discipline charged with understanding how the various subsystems of a larger system work and interact and with recommending or preventing changes that create problems for the design

SMC – U.S. Air Force Space and Missile Systems Center – Department of Defense center (located at Los Angeles AFB) charged with developing, acquiring, fielding and sustaining U.S. military space systems

SRB – Solid Rocket Booster – Solid-propellant (as opposed to liquid) motor used to help accelerate a rocket/launch vehicle upon liftoff

Solar Array – Passive material used to convert solar radiation into electrical power

Spacecraft – Vehicle or machine used to traverse outer space; includes satellites, planetary explorers, and crewed vehicles

Specific Impulse (also known as ISP) – Measure of a rocket’s efficiency (amount of thrust provided for a given amount of propellant); when all of the units are canceled out in the equation, ISP is measured in seconds

Stage – Segment of a rocket consisting of enough engines or motors to help the vehicle achieve a particular altitude and speed (velocity); stages are dropped from a rocket as it ascends to reduce the weight (mass) that needs to be propelled by the engines/motors

T-0 – Time Zero (pronounced Tee-zero) – Precise time for a scheduled liftoff

TEI – Trans-Earth Injection – Propulsive maneuver (“burn” if using rocket engines/motors) used by a spacecraft to depart its current location and head toward Earth

TLI – Trans-Lunar Injection – Propulsive maneuver (“burn”) used by a spacecraft to depart Earth orbit and head toward the Moon

TRL – Technical Readiness Level – Scale used to measure a given technology’s readiness to be used in the real world; a technology at TRL1 is still in the theoretical stage; tech with a TRL of 9 is already well understood and in the field

USAF – United States Air Force – United States armed service primarily responsible for air-based national defense; responsible for launch systems at U.S. Government space facilities

There are others…but these should get you started. Welcome to the space business!

Thanks to Hal Fulton, Angela Peura, Erin Shoemate

About Bart Leahy

Freelance Technical Writer, Science Cheerleader Event & Membership Director, and an all-around nice guy. Here to help.
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