Building worlds and colonies whilst re-supplying the frontline for the United Federation of Planets.
The Starfleet Corps of Engineering helped to build the United Federation of Planets. This aspect of Starfleet covers the shipyards and Advance Starship Design Bureau that breathes new life into the latest starship designs; it also covers the construction and upgrading of the colonies and starbases of Starfleet and the Federation; finally it also covers the logistical and re-supply aspect of Starfleet.
The Starfleet Corps of Engineering has specialised ships for carrying fuel, solids, liquids and passengers; amongst these classes are the Ptolemy, Dollond, Doppler, Ragnok, Independence, Sherman, Deneva and Mughi classes.
Refits and upgrades:
The Starfleet Corps of Engineering worked on the New Technology refits of the late-2260s and early-2270s. Vessels of frigate size and larger are refit with the new technology: LN-52 SCNN and LN-64 warp nacelles. Smaller ships and tugs are upgraded on an ad hoc basis, smaller vessels of the scout and destroyer size are replaced as the shipyards built new models based on the new technology.
Whilst Constitution class became Constitution (II) class and later Enterprise class refits, Doppler and Dolland class are refurbised with LN-52 SCNN nacelles and their hulls upgraded to take on the new stress loads. Older models like the original Hermes, Saladin and Ptolemy classes were given slap-dash interior upgrades whilst retaining their older PB-47 circumferential warp drives and hulls. The Corps of Engineering has to deal with a range of technology from legacy equipment from the 2260s and 70s up to the modern transwarp-derivative technology of the Excelsior and Ingram class era. Even the Enterprise refit legacy helped to forge new designs in the form of Levant and Constellation class.
It is the Advanced Starship Design Bureau subsidiary of Starfleet Research and Development that prototypes and tests new starship technology and classes. Constellation, Levant, Excelsior, Ingram and Apollo classes are just some of the recent designs tested by the ASDB.
Here is a description of the different nacelle types taken from Nacelles Monthly (Author note: taken from online discussion on Ships of the Starfleet nacelle designations):
PB-31- First Pilot style. Actually the Potemkin's is still a
PB-31 even though the spire in front is reduced to a nub by 2290
PB-32 - Second Pilot style.
PB-47 - Franz Joseph Design.
LN-52 - from a Mike Minor painting that became a logo for the
Star Trek revival (as is the Endeavor class). Taller than it is
wide, it can easily be recognized from a side view, as it tapers
down for most of its length until near the back where it abruptly
drops off to form a short "tail."
LN-60 - Unused TMP design. This is from the Brick Price
miniature build when it was a proposed television series. (The
Constitution II class and the Tikopai class incorporate elements
of this design.) The nacelle is roughly TMP shape, but thinner
(less buildup around the coils?) and has a smooth front (was a
red effect to be projected on/generated in here?)
LN-64 - TMP design
LN-68 - Seen on the Belknap-class U.S.S. Raan. Movie style, but
the top, from the "collar" forward, slopes down.
LN-72 - They refer to the Ingram (competitor to the Excelsior design)
being refitted with LN-72 warp engines to replace the transwarp
Koeller UTI K27 engines, and that the Excelsior will also be
refitted. The seem to prefer the Excelsior eventually be made to
look more like their Ingram, but movie events have overtaken the
book, and we can probably take the LN-72 to fit inside the
Excelsior's original transwarp nacelles.
Starfleet Dynamics calls the type seen on the Grissom a
"SW27/1-4K Warp Drive nacelle."
LN-76: Designed for the Apollo class
LN-83: Cancelled nacelle for Akyazi-class, larger tham final design.
LN-90: Used on Akyazi class first batch.
LN-91: Used on Arbiter sub-class of Akyazis.
LN-94: Used on Akula sub-class of Akyazis.
Logistics, Construction and Support:
The Corps of Engineering are responsible for the transportation of materials, fuels, armaments, parts and personnel within the Federation and its colonies. Freighters and tankers are the responsibility of this part of Starfleet, along with the storage and refinery facilities. Starship resupplying missions, colonial construction and maintainance are all conducted by the Corps of Engineering. Specialist ships like Mughi class support starships, whilst over half a dozen classes of tug, freighter and tankers support the colonial aspects.