Quote:
Originally Posted by lemit
I noticed that every time an astronaut moved from one place to another, the NASA spokesman used the word "translate" instead of "transfer." I looked at Merriam-Webster and got the following definition of "translate:"
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I know we have some NASA people around here. Any explanation why NASA would ignore a perfectly usable word in favor of a word that's clearly out of place?
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I’m not now nor have I ever worked for NASA, but being with the terminology, can explain this.
This particular spaceflight term comes from the
conventional meaning of the term “translation” in geometry, “moving every point of a figure a constant distance in a specified direction”. The other term of importance in the geometry of rigid bodies borrow by spaceflight is “
rotation”, in which the orientation, or attitude, of a body is changed, but the location of its center of mass is unchanged, which is conventionally divided into 3 principle axes oriented on the maneuvering body: roll, pitch, and yaw.
Because, as lemit notes, translate is a
transitive verb, to be syntactically correct, “the astronaut translated from the front to the rear of the shuttle bay” should add an object to read something like “the astronaut translated
his location from the front to the rear of the shuttle bay”.
An important feature of a translation is that it assumes the body to be at rest relative to some convenient coordinate frame before and after the maneuver – a sensible practice for astronauts bopping about in shuttle bays.
In spaceflight, the term “transfer” usually refers to a specific kind of maneuver in which an orbiting craft changes from one orbit to another, as in “maneuvering thrusters were fired to transfer the satellite from a low-Earth orbit to a geostationary orbit”. The simplest such Earth-orbiting maneuvers require a change in velocity, or delta-v, at its beginning and end, with the path followed between the two called a
transfer orbit. Strictly speaking, the starting and end paths need not be orbits, but given the energies available in present-day spaceflight, every spacecraft is always orbiting some primary body.
So, in short, the difference between a translation and a transfer in spaceflight terms is that one does not, and the other does, result in a change of velocity relative to the starting reference coordinate frame.
It’s not unusual for words to have meanings different from their common ones when used in specialized technical contexts. One can avoid confusion when writing or speaking for a non-technical audience by qualifying the words – eg: “geometrically translate” for “translate” – but in talk between specialists such as heard in spacecraft radio communication, short forms are used.
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