Saucer separation on a Galaxy class starship.

Saucer separation is an emergency manuever performed on some Federation starships. It involves the complete disconnection of the primary hull and the secondary hull. Prior to the 24th century, separation was used as a means of abandoning either hull in the event of a catastrophic emergency. It was a one-time only event, and the hulls could not be reconnected without external support. (TOS: "The Apple") By the 24th century, separations were designed to be more routine with some classes being designed with reconnection abilities. Both components contain essential systems, allowing each to be independently operable for extended periods. (TNG: "Encounter at Farpoint")

Classes capable of separation

In the 23rd century, most classes with the saucer/engineering hull layout were capable of separation, including the Constitution class. Separations were only for emergency purposes; the two sections could not reconnect easily following a separation. (TOS: "The Apple")

By the 24th century, starship classes were designed to routinely separate into one or more components. The Galaxy class is one such example (TNG: "Encounter at Farpoint"), as is the Prometheus class. (VOY: "Message in a Bottle")

A saucer separation involving the refit Constitution class USS Enterprise was storyboarded by Andrew Probert for a possible scene at the end of Star Trek: The Motion Picture. Features such as a separation line were intentionally designed into the filming model by Probert, and are good indications that the ship can separate just like its earlier form.
Design sketches John Eaves produced for Star Trek: First Contact seem to imply that the Sovereign class has routine saucer separation capabilities, and separation lines plus a battle bridge are evident on the master systems display on the Enterprise-E bridge. However, this has not been confirmed in dialogue; furthermore, the stardrive section seems to be missing impulse engines.
The Excelsior class may be capable of separation; docking latches and a battle bridge were seen on the Enterprise-B master systems display, and the yoke of the ship has several potential separation lines. Similarly, the miniature of the Ambassador class shows striping which suggests a separation point. Like the Sovereign class, there do not appear to be impulse engines in both parts of those ships, however, which may suggest that they cannot separate.

Separation sequence

On the Galaxy class, saucer separation was primarily designed as a way for the civilian and nonessential crew complement to escape in the saucer section, while the senior staff and essential personnel engage a threat or enter a potentially dangerous situation in the stardrive section.

In a starship separating due to these circumstances, the separation command is issued by the commanding officer from the main bridge. The CO, along with most of the senior staff, transfers to the battle bridge on the stardrive section via a dedicated emergency turbolift, while a junior officer is typically left in command of the saucer module. The saucer is almost always given the directive to seek safety by retreating to a starbase or other allied territory. (TNG: "Encounter at Farpoint", "The Arsenal of Freedom")

Evacuation of nonessential personnel from the stardrive section is conducted by security staff. (TNG: "Encounter at Farpoint") Audio warnings are given to the crew to alert them of the pending event and how much time is remaining to vehicle separation. (Star Trek: Generations)


Docking latches.

During the actual separation event, the docking latches, on the stardrive side of the ship, collapse and retract into the hull of the stardrive section. An autoseparation is generally used to separate the two components of the ship (TNG: "The Best of Both Worlds, Part II") although a manual option is also available. (TNG: "Encounter at Farpoint") The separation is monitored from the main bridge and battle bridge by the Conn and Ops officers. (TNG: "Encounter at Farpoint", "The Arsenal of Freedom") Staff in Main Engineering can also provide support during a separation. (TNG: "The Best of Both Worlds, Part II")

The drive section, containing the ship's warp drive and the majority of weapons systems, is then free to confront danger without endangering the lives of nonessential crew.

Following the crisis, the two sections can rendezvous and rejoin. Connection is generally the reverse process of separation, again with automated and manual options.

Separation can also be performed at warp speeds, although it is much safer at lower warp velocities due to the fact that the saucer is not equipped with warp drive, only impulse engines. During a high warp separation, the stardrive section would need to slow down just long enough for the saucer, still riding the decaying warp energy, to clear. Otherwise, there would be risk of the stardrive section slamming into the rapidly slowing saucer. The procedure is extremely risky, and there is no margin for error. A high warp separation was never attempted prior to 2364.(TNG: "Encounter at Farpoint")

Emergency landing of saucer section


The saucer module of the USS Enterprise-D, landed on Veridian III.

The saucer sections of many starship classes are designed to make planetfall on a suitable planetary surface, preferably Class M. The saucer must be making a level approach and heading towards the ground at a shallow angle. The area chosen for landing must be smooth and relatively free of obstruction. The great structural stresses placed on the spaceframe of a landing saucer section would most likely prevent it from being returned to spaceflight. (Star Trek: Generations)

The Enterprise-D saucer landing sequence was conceived in 1991 for the Star Trek: The Next Generation Technical Manual. Writers Ronald D. Moore, Brannon Braga, and Jeri Taylor were inspired by that information and wanted to use a crash as a cliffhanger for the sixth season of TNG, but producer Michael Piller did not like the idea. Furthermore, it would have been too costly to film on a television budget with the VFX technology available at the time. Moore and Braga later wrote the scene into Generations.
According to fandom sources, the original Enterprise had landing gear stored underneath the two triangle-shaped hatches on the ventral side of the saucer. A third leg popped out from the cavity where the secondary hull connected to the saucer. Similar shapes were placed on the saucer of the Enterprise-E as a homage to the original ship, although designer John Eaves did not realize the fandom history behind those objects.
For the refit Enterprise, Andrew Probert purposefully designed landing gear into the saucer, hidden behind the four square panels located on the saucer's concave underside. The panels were also carried over to many TMP-era designs, including the USS Reliant and USS Excelsior. Probert had intended to place landing gear on the Enterprise-D saucer as well, but became distracted by other elements and never returned to the landing gear concept. As he recalled several years later, the poor ship eventually paid the price for that oversight!

Examples of separation

Tactical uses

The USS Enterprise-D used saucer separation as a way to confront the Q entity on its first mission in 2364. Captain Picard left Lieutenant Worf in charge of the saucer section. The separation was the first to be conducted at high warp.

During the reconnection of the ship, Picard ordered new first officer William Riker to conduct the docking manually. The bridge crew were somewhat apprehensive about the plan, but Riker performed well. He safely rejoined the two sections without any automated assistance, proving himself to Picard. (TNG: "Encounter at Farpoint")

Commander Riker suggested a saucer separation shortly before the Enterprise was sent to investigate possible Romulan activity later that year, although Picard felt it was too early to justify such an action.

The Klingon criminals Korris and Konmel were fascinated by the stardrive section of the Enterprise and were excited at the prospect of hijacking it for their use in battle. They attempted to get Worf to assist them in accessing the battle bridge and separating the ship, but fortunately Worf was loyal to the Enterprise crew. (TNG: "Heart of Glory")

Also that year, acting captain Geordi La Forge separated the ship to return and fight the automated weapons drones on planet Minos. Chief Engineer Logan was ordered to take command of the saucer section and take it to Starbase 103. (TNG: "The Arsenal of Freedom")

In 2366, Commander Shelby suggested separating the ship and using the saucer to create a distraction for the Borg. Commander Riker rejected the idea, feeling the saucer's impulse engine power would be of use in the battle. Shelby briefed Picard on her plan despite Riker's objections. (TNG: "The Best of Both Worlds, Part I") Later, Riker used Picard's knowledge of the plan to his advantage during a rescue attempt to retrieve Picard, assimilated as Locutus. Following the devastating Battle of Wolf 359, the Enterprise caught up to the Borg cube, then engaged the vessel and separated. As expected, the Borg focused their attack on the stardrive section, ignoring the saucer module. This allowed the saucer to launch a shuttlecraft, masked in an antimatter spread, to the cube. Commander Data and Lieutenant Worf successfully transported aboard the cube and abducted Locutus, which was a crucial event leading to the defeat of the Borg in orbit of Earth. (TNG: "The Best of Both Worlds, Part II")

This use of saucer separation was perhaps inspiration for the multi-vector assault mode of the USS Prometheus, launched in 2374. (VOY: "Message in a Bottle")

Emergency uses

The only use for saucer separation in early starship classes was for emergency purposes related to crew survival. In 2267, Captain James T. Kirk ordered chief engineer Montgomery Scott to jettison the nacelles and escape in the saucer section when the original USS Enterprise was threatened by Vaal at Gamma Trianguli VI. Ultimately, the separation was never ordered. (TOS: "The Apple")

Obviously, the Galaxy class could also use saucer separation as a way to ensure crew safety. In 2365, saucer separation was considered in order to quarantine the cargo bay of the Enterprise-D when it was feared that a plasma plague strain had escaped a containment facility. (TNG: "The Child")

When Ansata terrorists planted an implosion device on the warp core of the Enterprise-D during an attack in 2366, Captain Picard ordered a saucer separation. Fortunately, Commander La Forge was able to remove the device and beam it into space before it detonated. (TNG: "The High Ground")

In 2367, Dr. Noonien Soong used a signal to temporarily cause Data to use any means necessary in order to return to Soong's home planet. He caused an environmental system failure on the bridge, then locked himself on the bridge and severed all command functions. Data then plotted a course to Soong's planet at high warp. Picard and the senior staff, in Main Engineering, attempted to separate the saucer in order to restore computer control to the stardrive section. The plan was to then incapacitate the saucer with a tractor beam once the separation was complete. However, Data was able to discover the separation command and cancel it before it could be carried out. (TNG: "Brothers")

The Enterprise struck a quantum filament in 2368, disabling most of the ship's systems and causing a gradual failure in antimatter containment. Ensign Ro Laren pushed for a saucer separation to protect survivors in the saucer section, but doing so would condemn those in the stardrive section to certain death when the core breached. Deanna Troi, the senior officer on the bridge at the time, decided to delay separation and use power from the bridge to activate crucial displays in Engineering. Commanders Riker and Data saw the displays right before the ship was to separate, averting the containment breach. (TNG: "Disaster")

Unfortunately, the Enterprise-D was required to separate for the same reason three years later, in 2371. Serious damage was inflicted to the ship as a result of an ambush by the Duras sisters, and the warp containment system was mortally wounded. The entire ship's complement was evacuated to the saucer and it reached safety just as the drive section exploded. The shockwave from the blast shoved the saucer section into the atmosphere of planet Veridian III, where the ship was forced to make a crash landing. There were light casualties, although the ship was deemed unsalvageable. (Star Trek: Generations)

Saucer separation was planned as a regular feature during the early days of Star Trek: The Next Generation. Several storylines, including a B-plot for "When the Bough Breaks," were to use saucer separation. However, budget limitations at the time did not allow for extensive footage of the separated components to be shot, and it was also felt that separation slowed the progress of the story. Unfortunately, this meant that the Enterprise was sent into a number of dangerous situations with saucer separation never being mentioned as an option.
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