Why are Starfleet vessels designed with nacelles so far away from the hull?

Question

Based on the film and television events, it seems early shows had Klingon, Romulan, Vulcan, Breen, and Starfleet ships having nacelles placed far away from the hull on struts or wings. On the other hand, Ferengi and Cardassian ships have their warp coils in or near the ship's hull.

Note this question asks about distance, like "why not put nacelles close to the body" rather than the number of nacelles used. Why do most Starfleet ships stick their nacelles out so far. Please avoid answers talking about counting engine parts unless somehow the number of nacelles requires them to be far apart.

Aside from "coolness," why are nacelles kept away from the hull in Starfleet vessels? Some races can incorporate the nacelles within the hull, others agree with Human design. I'm interested if anything in-universe (not extended universes) gives us an explanation for the way we see these ships on screen.

I grant that even in the real world some engineers disregard safety. That would be my blind guess. It just sort of looks vulnerable.

Answer 1

Apart from simple narrative necessity, I think we can extrapolate from the original Enterprise blueprints (Sheet 11, Paramount 1975) that radiation is the answer.

When we look at the plan for the Support Pylon (where the famous Jeffries Tube is located), we see two safety locks located in the pylon. There are notations for each. The lower safety lock:

Warning: Entry beyond this safety lock permissible only with anti-radiation suits.

The upper safety lock:

Warning: Entry beyond this safety lock permissible only with environmental suits and entire main propulsion unit shut down.

Presumably, if you wander far enough up the Jeffries Tube without proper safety equipment, you're not going to be coming back down again, except in a body bag.

Answer 2

Not all Starfleet vessels have nacelles far away from the hull (think shuttles), but that main thing that was taken into consideration is that the nacelles needed to "see" each other. This would require the spacing to be farther apart on larger ships.

It seems this was something Andrew Probert (the concept artist for TOS) decided on during conversations with Gene Roddenberry on the matter.

As far as the line-of-sight requirement, that was my edict, that, in order to be codependent, the warp engines had to "see" each other, totally. I'm taking about the power combs, not necessarily the Bussard collectors but the bulk of those combs have an energy path between them. And then for other starships, just like in World War II, where all the nations had fighter aircraft that all looked different -- you know, a cultural distinction between, say, a German aircraft and an American aircraft or a Japanese aircraft -- they all operated in the same way having the same basic components of wings, body, and engine, so I applied that thinking to the alien ships I designed as well, so the Ferengi ships, and Romulan Warbirds, have twin warp engines that have to see each other in order to operate. Even my shuttlecraft having a very shallow clearance, still see each other. That's why designs like the Romulan scout ship, where the engines cannot see each other, aren't consistent. There are also some cool Starfleet designs like the Nebula Class ships, but their warp engines cannot see each other. Even those runabouts ignore that ruling which messes up the continuity. Science fiction in particular NEEDS to be consistent. If you negate that,...it all falls apart.

_{Source: "An Exclusive Interview with Andrew Probert", Interview conducted face-to-face on May 28, 2005 at Wonderfest, and revised via email in June 2005 (posted on trekplace.com)}

This also confirms why "Klingon, Romulan, Vulcan, Breen, and Starfleet ships" have such similar designs. Probert also does not seem to be a fan of designs that break this rule stating science fictions needs to be consistent.

Answer 3

Gene Roddenberry's concept of the warp field was that it was symmetrical and needed to be in open space. That's why the nacelles are not in direct line with the hull of the ship - it wouldn't be possible to create a stable warp field with bits of ship in the way!

You can see the same design concept in Klingon, Romulan, and Ferengi ships to name a few. This design was not universally followed by all Star Trek ships, but many or most of the ships in the original series and the Next Generation did follow this design principle.

Voyager can't go to warp until the nacelles have direct line of sight with each other. I can only imagine that the Defiant has a big, open space inside the ship for the warp field, which contributed to the ship being so cramped!

From An Exclusive Interview with Andrew Probert:

Tyler: Do you know the origin of what have become known as "Roddenberry's Rules of Starship Design" -- the idea that warp nacelles have to be in pairs, and things of that sort. I understand that there were a set of guidelines. Do you recall the origin of those?

Probert: Gene specified to me, in fact, that starship warp engines operate in pairs... only in pairs because they're codependent. If you had one warp engine, you'd probably go in a circle, I don't know... (laughs) So in the same breath he negated the three-engined dreadnoughts along with the single-engined destroyers, on the edict simply that, to achieve warp drive, you had to have codependent warp engine pairs. As far as the line-of-sight requirement, that was my edict, that, in order to be codependent, the warp engines had to "see" each other, totally. I'm taking about the power combs, not necessarily the Bussard collectors but the bulk of those combs have an energy path between them. And then for other starships, just like in World War II, where all the nations had fighter aircraft that all looked different -- you know, a cultural distinction between, say, a German aircraft and an American aircraft or a Japanese aircraft -- they all operated in the same way having the same basic components of wings, body, and engine, so I applied that thinking to the alien ships I designed as well, so the Ferengi ships, and Romulan Warbirds, have twin warp engines that have to see each other in order to operate. Even my shuttlecraft having a very shallow clearance, still see each other. That's why designs like the Romulan scout ship, where the engines cannot see each other, aren't consistent. There are also some cool Starfleet designs like the Nebula Class ships, but their warp engines cannot see each other. Even those runabouts ignore that ruling which messes up the continuity. Science fiction in particular NEEDS to be consistent. If you negate that,...it all falls apart.

(emphasis mine)

Answer 4

One question is why the nacelles have empty space between them. Others have answered because Gene Rodenberry.

A second question is why the nacelles are so far apart. One answer given -- which is excellent -- is safety. The nacelles are far apart by necessity in early starfleet designs because they have to be far apart from the hull.

The raditiation problem is eventually solved. So the question becomes if there is an engineering reason to keep the nacelles far apart. The answer is to use energy efficiently.

The warp nacelles create a subspace bubble. The nacelles are long, so they create elliptical bubbles of nearly constant width in the middle. To create a larger field, it uses less energy to overlap two medium size bubbles to make one to encompass the ship. Consider that two overlapping fields half the width is roughly 1/4 the size of a field with the full width. This suggests to me that there is minimum distance required between the hull and the bubble edge. To achieve this with the least amount of power, you would want the nacelles to be as far apart as possible.

People have commented about the Defiant's unique design. I have a theory, but one that I think may be inconsistent with canon. I don't recall if any characters said "nacelles" (plural) when referring to the Defiant.

It's possible that the defiant uses a single nacelle design; to weather battle a singular set of warp coils could be in the center of the ship. We know the defiant has a power core comparable in size to the Enterprise-D, yet it is much smaller. The loss in efficiency would be a trade off that is of negligible impact.

The warp flash when a ship "accelerates to warp speed" is vented excess energy during start. (I am not sure I am 100% correct on that point.) It makes sense that the warp flash would then come from the sides of the Defiant, as the energy is dumped to space.