Last Voyage of the U.S.S. Constitution

Last Voyage of the U.S.S. Constitution is a side quest in Fallout 4. The Sole Survivor has been drafted by Ironsides to assist him and his robot crew in their quest to return the USS Constitution to the Atlantic Ocean.

Detailed walkthrough

 * 1) Head to the USS Constitution (east of Bunker Hill). As the player character approaches the ship, Lookout will meet and tell them to head up into the ship and meet Ironsides on top of the USS Constitution.
 * 2) * A 100 caps pre-reward can be bargained at this point.
 * 3) After talking to Ironsides, scavengers will attack and the player character will need to deal with them.
 * 4) * OPTIONAL: Fire the cannons.
 * 5) * Hitting the robot allies with stray fire or any AoE weapon (such as the missile launcher, grenades or the Fat Man) will result in the entire crew turning hostile and therefore failing this quest; however the cannons are safe to fire as they do not affect the robots.
 * 6) Talk with Bosun on the third deck inside the USS Constitution.
 * 7) He will ask that the three power cables inside the ship be repaired or replaced. It requires INT 3+ to repair the power cables or grab the new power cables. (OPTIONAL: Grab power cables in a metal box near Bosun.)
 * 8) Look for yellow utility boxes to replace the power cables. One can be found not far from Bosun on the floor up against the outer ship wall. The other two can be found one deck down one in the middle of the floor and the other on the outer ship wall.
 * 9) Return to Bosun and talk with him again.
 * 10) He will ask the player character to repair or buy a replacement power relay coil. It requires INT 5+ to repair the power relay coil.
 * 11) The power relay panel can be found on the same deck as Bosun, on the righthand side of the ship in the wall.
 * 12) Next, the player character will need to find Mr. Navigator and offer their assistance.
 * 13) Mr. Navigator will ask that the player character recover the guidance chip for the ship from the scavengers.

Acquiring the guidance chip

 * 1) Head back towards Bunker Hill and talk to Mandy Stiles. At this point, the Sole Survivor will have to at least claim to choose to help the scavengers destroy the robot crew or side with Ironsides. Both paths follow the same pattern, but with a few differences. MacCready, Piper, Hancock, Strong and Cait dislike it if the Ironsides path is chosen, but Codsworth, Deacon, Curie, Paladin Danse, Nick Valentine and Preston like it.
 * 2) * If siding with the scavengers, they will give up the guidance chip for free and ask for any equipment the ship requires so they can sabotage it, along with a warning not to double-cross them.
 * 3) * If choosing to ally with Ironsides, the chip must be stolen from the scavengers' camp. (Note: some companions such as John Hancock, Nick Valentine, Preston Garvey, Codsworth, Curie, Danse and Piper dislike stealing the chip. Deacon likes siding with Ironsides and does not object to stealing the chip.) Stealing the guidance chip will turn the local scavengers hostile, even if undetected.
 * 4) * Note: If the Sole Survivor tells Mandy Stiles they need to think about the deal instead of choosing immediately, and provided they can sneak into the base of scavengers, they can steal the chip undetected. If they can then leave without being detected on the way out, they can run back to Ironsides without tripping the mines in the back alley, and then can sneak away without getting attacked.
 * 5) Head back to the USS Constitution and install the guidance chip on the main deck.
 * 6) Now return to Mr. Navigator and talk with him (he should have moved up onto the main deck near where the guidance chip was installed).
 * 7) Mr. Navigator will now ask the Sole Survivor to repair or retrieve the Poseidon radar transmitter. It requires INT 9+ to repair the radar transmitter or a replacement can be retrieved from Poseiden Energy Turbine 18-F, northwest of the BADTFL regional office. Alternatively, the player may also be sent to the Poseidon reservoir, south of Fort Hagen, to retrieve the replacement part.
 * 8) After repairing the guidance systems, talk to Mr. Navigator again and receive instructions to talk with Ironsides again.
 * 9) Ironsides will ask the player character to retrieve FLL3 turbopump bearings from a specific location. Known locations for this part of the quest are: the Corvega assembly plant south of Lexington, Fort Hagen at the west edge of the map inside a military trunk and General Atomics factory northwest of the Castle.
 * 10) Return to the USS Constitution and head into the captain's quarters on the second deck, then install the FLL3 turbopump bearings.
 * 11) Return to Ironsides on the main deck and talk to him; while doing so the scavengers will attack the ship again. Eliminate them. If the scavengers reach the top deck, the quest will fail, so a quick save is recommended before doing this part.
 * 12) Head back up to Ironsides, to be rewarded with the Broadsider and be asked to complete a final task of firing up the auxiliary power to launch the ship.
 * 13) Activate the auxiliary power circuit and watch the ship take off. The switch for the auxiliary power is not on the ship. Head to the building across from where the scavengers are set up (You can see the blasted open top floor from the ship deck, with a broken Mr. Handy). Take the stairs all the way to the top floor to find a small generator. The switch is through the door on a power pylon. The quest is complete after the ship crashes.
 * 14) Afterwards, if the player character reaches the tower in which the ship crashes (near Faneuil Hall) using two elevators on the east side of the ship at ground level, Ironsides will name them honorary lieutenant and grant use of the captain's quarters as well as the Lieutenant's hat.

Siding with the scavengers
There is no difference between siding with Ironsides or the scavengers up until the Sole Survivor is told to get and install the guidance chip and radar transmitter, as is mentioned above.
 * 1) Once the FLL3 turbopump bearings are retrieved, take them to Mandy instead of Ironsides. Davies will sabotage them so that the ship will explode when the rockets are fired up.
 * 2) Install the sabotaged turbopump bearings and talk to Ironsides again. Go ahead and agree to turn on the auxiliary power.
 * 3) Meet up with Mandy (optional) in the building across from where the scavengers are hiding out. She will also tell the player to start up the power. The switch for the auxiliary power is not on the ship. It is on the top floor of the building where Mandy currently is. Take the stairs all the way to the top floor to find a small generator. The switch is through the door on a power pylon.
 * 4) After the rockets fail, the ship will remain landlocked and the robot crew will turn hostile. Storm the boat with the scavengers and defeat Ironsides.
 * 5) Meet up with Mandy after claiming the ship, she has wandered away to near Cabot House, to find out the scavengers held a vote and are not going to split the cut and have, in fact, voted to kill the Sole Survivor.
 * 6) Regardless of what dialogue option is chosen, the scavengers must be defeated to complete the quest. NOTE: They seem to be very slow to turn hostile if they turn hostile at all, and there's only four of them (one on the ship, one by the scavenger claim, Davies, and Mandy). Even if Mandy and Davies do not turn hostile, killing them will complete the quest. Killing them while they are not hostile will count as murder.

Behind the scenes
This quest was created and designed by Ferret Baudoin. He performed research related to rockets and how to tamper with them, which he later joked about, saying that he was likely put on a watchlist.