Thanks for the feedback.
I chose “Bussard ramscoop” because every Trekker will presumably understand the basic meaning. However, by the time of TNG it apparently has become a colloquialism as it actually isn’t a “ramscoop” or “ramjet” in the original sense of Mr. Bussard: http://en.wikipedia.org/wiki/Bussard_ramscoop
(I have a couple of non-fiction books that discuss his proposal for sublight propulsion so the essence of this wikipedia article is genuine and authentic)
Considering he made his theoretical propulsion proposal back in 1960 and that the general “ramjet” design shares noticable similarities to a convential jet engine, I can imagine what a great time an aviatic aficionado like Matt Jefferies must have had implementing it on the USS Enterprise.
However, I believe these four rings behind the nacelle caps (these do have an alignment compliant with an intake function) is really all there is performing such a ramjet function.
In-universe these evolved
into the "Bussard ramscoops" of later starships like the Enterprise-D (IMHO, a ramjet evolution makes more sense than to start searching for rationalizations why the TMP Enterprise
and the USS Excelsior
did not have these red thingies).
Matt Jefferies’ task was to visually suggest the sheer power of these engines and I’d say these ominous red glowing and rotating caps of the TOS Enterprise still convey that feeling today (I don't feel that picking up particles of interstellar matter is remotely compatible with (t)his original design intention).
The biggest support for the deflection function comes from the spikes in front of the warp nacelle caps the pilot versions of the Enterprise had, of course.
All The Making of Star Trek
tells us is that the parabolic dish belongs to the main sensor and suggests that its spike is an “asteroid deflector”.
This does not necessarily imply that space particles ahead of the ship require additional deflection as the streamlined hull itself appears suitable to repel space particles (with the exception of one location: the main deflector...
On the contrary, it might even help to explain the function of the exterior window shutter in “The Mark of Gideon” as a physical particle shield.
The apparent problem with a deflector function of the nacelle caps (the dialogue from “The Doomsday-Machine” and its conclusions notwithstanding) is that it’s contradictory to the concept of attracting interstellar matter for fuel for the ramjet rings behind the nacelle caps: Either you deflect or
you attract, but you can’t do both at the same time (unless you have yet another and “exotic” Heisenberg compensator...).
Of course, in those theoretical concepts S.C. mentioned (thanx), there wouldn’t be the extra need to attract or ionize interstellar matter (an inevitable obstacle that needs to be overcome in Mr. Bussard’s original proposal) as reactant fuel.
Because warping space would already bring those particles close to the Enterprise. Apparently the main deflector would still need to project a protective semi-circular shield ahead of the ship – from which the interstellar matter “built-up” would be cleared by directing it towards the ramjet intakes to provide the fuel to react with the antimatter.