The Nakai mothership is a carrier vessel in the Nakai fleet.
Nakai motherships are large, boxy vessels, similar in appearance to a three-dimensional trapezoid. The ship is mostly gray with red highlights. Hangar bays jut out from either side, and the engine mechanism dominates the rear of the ship. Its primary and only apparent weapon rests on the nose, identified by a large, red-orange dish.
The mothership carries a large compliment of fighters, with which to board other vessels. Its main weapon fires a yellow energy pulse which is not very effective against the shields of the Ancient vessel Destiny on its own, but can be far more dangerous in groups. Its firing rate is somewhat slow. The ship possesses shielding which was able to resist sustained fire from Destiny's main cannon; the damage caused, if any, is unknown. A mothership retreated from battle with Destiny after taking multiple hits, but Destiny itself would likely have been destroyed had it continued firing.
These spacecraft use an unknown form of hyperdrive very different to that used by any other known species. They are most likely slower than Tau'ri ships as it took the Nakai three weeks to catch up to Destiny in the void between galaxies while a Daedalus-class ship can travel from Earth to Atlantis in that amount of time. (SGU: "Space", "Sabotage", "Trial and Error", "Deliverance")
This type of starship was first encountered by the Destiny expedition in 2009, when it began an unprovoked attack on Destiny. It launched fighters to attack and board Destiny, kidnapping Chloe Armstrong. Colonel Everett Young used the Long-range communication device to commandeer the body of one of the aliens aboard the ship. During his search for Chloe, he discovered and freed Dr. Nicholas Rush, who had been kidnapped by the aliens after being left on another planet. Rush would go on to free Chloe and escape the ship with her, after which it retreated. (SGU: "Space")
After Destiny entered the void between galaxies, the Nakai were able to sabotage the Faster-Than-Light engine by using the communication device to take over Lt. Vanessa James. Two motherships mounted an attack and attempted to board Destiny, but Dr. Jeremy Franklin managed to bypass the damage and take the ship to FTL, leaving them behind. (SGU: "Sabotage")
In the next galaxy, Destiny began running a battle simulation in Young's dreams, in which nine motherships would surround the ship and demand the surrender of Chloe. In the first iteration, Young ordered the crew to fire back. The combined fire from the nine ships overwhelmed the shields and caused an overload in the sublight drives, destroying Destiny. The second iteration had Young attempt to divert all power to shields. Six additional motherships arrived and the scenario played out the same. In the final iteration, Young did as they asked and turned over Chloe. This allowed them to shut the shields off completely, enabling a full-fledged invasion which succeeded in taking over the ship, killing everyone on board. (SGU: "Trial and Error")
During the Drone attack on Destiny, Chloe sent a signal that summoned three motherships to the battle. She did so knowing that the Nakai had followed Destiny to the next galaxy and planning to use them as a distraction. The plan worked: most of the drones attacked the motherships instead of Destiny, allowing Destiny to destroy the Control Ship while two motherships were destroyed and the third severely damaged. The mothership threatened the shuttle when it collected one of the drones, but a deal was struck: in return for the expedition dealing with the drones, the aliens would remove their pathogen from Chloe and release her. The mothership allowed Lt. Matthew Scott and Chloe to board their ship and honored their end of the deal. When the second cluster of drones arrived, the mothership escaped into hyperspace. (SGU: "Deliverance")