Questions tagged [terminology]

Questions regarding words and abbreviations used in the fields of spaceflight and space exploration, and their meaning when used in those contexts.

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Why do Russian rocket engineers call C₂H₈N₂ "heptyl"?

Unsymmetrical dimethlyhydrazine or "UDMH" is a propellant which has been used by Russian, American, European, Chinese, and Indian rockets. Russian rocket engineers nickname it "heptyl". Why was this ...
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How old is the use of "L minus" to denote the number of days before launch?

In the SpaceX Inspiration4 Launch broadcast at about T-01:31:05 (91 minutes before launch) the term "L minus five" is used. While "T-minus" is a ...
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What is the difference between these various spacecraft pyrotechnics?

The following terms have been used in various Space Exploration StackExchange questions and answers. What are the differences (if any) between these various terms? detonating cord detonating fuse (...
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What do the RD numbers of Russian rocket engines mean?

Most Russian rocket engines have a name on the form of for example RD-107 (РД-107). But apart from different engines having different numbers, how is the number chosen? All RD-2xx engines appears to ...
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What is the official etymology of the term "service" module?

Are there any reputable sources about how the word "service" was chosen for the Apollo service module? (This is a question about how the term was chosen, not about what the term means. ...
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Is there a canonical definition of the term "block" as used in "Falcon 9 block 5"?

I gather this has a meaning related to "version". However, I have seen this term used for military and commercial aircraft and other products (generally connected to government or aerospace)...
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what is the relevance of ion cyclotron and ion collision frequency ratio

On earth, the ion cyclotron and ion collision frequency ratio is 1 at roughly 118 km, and this is used as one of the definitions of the limit to space. What are ion cyclotron frequency and ion ...
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First instance of a frangible nut in space? Which space-nut was first successfully "franged"?

Wikipedia's Frangible nut begins: Not to be confused with Explosive bolt. The frangible nut is a component used in many industries, but most commonly by NASA[citation needed], to sever mechanical ...
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Does NASA use any of the twilight designations?

Do the differences in civilian, nautical, and astronomical twilight have any technical relevance to NASA either on Earth or any other object in the solar system where a probe has landed? Does NASA ...
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Is there an equivalent term for average altitude like semi-major axis?

So if we have a satellite in a non circular orbit, can't state a time independent altitude (we can only state the altitude at a given time). We can however state a constant value for the semi-major ...
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What are non-rocket-based reaction mass drives called?

There's plenty of talk out there about a certain type of propulsion system, but I don't know the proper name for it. You gather up / buy / otherwise acquire some kind of non-rocket material, like ...
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Are there now established classes of solar-electric powered spacecraft?

The NASA.gov press release NASA Awards Contract to Launch Initial Elements for Lunar Outpost says: NASA has selected Space Exploration Technologies (SpaceX) of Hawthorne, California, to provide ...
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What terminology is used to describe spacecraft in stationkeeping?

Forgive any inaccurate wording of this question. If a Soyuz craft which had been docked at the Zvezda module backed away from the ISS and remained at stationkeeping, would NASA, Roscosmos, or the ESA ...
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Official terminology for non osculating orbital elements

When I need to talk about an orbital element that is not osculating and that it is the true/actual element at a given instant, I use the term "actual": actual perigee, actual eccentricity, actual semi-...
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Is there a term for the activity of weightless astronauts hanging out on walls or ceilings?

Weightless astronauts often sit, stand, walk, or sleep on (or near) surfaces that (with gravity) we would normally call walls or ceilings. I reference such a phenomenon in my comment here: I would ...