Rocketman

The Rocket Man was Tom's prototype Sea Train. The Straw Hats used it temporarily to travel from Water 7 to Enies Lobby.

Ship Design and Appearance
The Rocket Man is a gray locomotive with a shark's face painted on the front, though the shark was commented on to not have much significance. It consists of the locomotive itself and one passenger car. Like the Puffing Tom, it has a 4-4-0 wheel arrangement and is capable of traversing across water as well as on land. The Rocket Man was considered by all who worked on it an experimental failure as the train could only travel at dangerously high speeds, had no means of braking, and lacked the momentum to plow though obstacles without getting derailed. This meant that once Rocket Man reached its top speed, it would continue going forward with no ability to stop itself, making it far too dangerous to be used commercially.

In Pursuit of the Puffing Tom
After surviving the onslaught of the Aqua Laguna, Monkey D. Luffy and company decided to pursue the Puffing Tom in order to rescue the captured Robin. However, two major factors were stopping them: the Aqua Laguna was raging on, meaning that no ship available was suitable to travel under such conditions, and the Puffing Tom was the only known Sea Train built to travel under them.

It was then that Kokoro revealed the Rocket Man in an abandoned warehouse. Fixed up by Iceburg, the Rocket Man was all ready to go. It was then when the Franky Family begged to join Luffy in order to save Franky, at which Luffy accepted.

After setting off into the storm, the Franky Family latched their Franky Houseboat onto the Rocket Man. Later its revealed that several stowaways had snuck on-board: Chimney, Gonbe, and most notably the Dock One foremen now reduced to three due to the treacherous circumstances.



During the pursuit of the Puffing Tom, several events happened. These included Luffy and Roronoa Zoro being able to break through the Aqua Laguna, Yokozuna joining the apparent army and, Zoro defeating T-Bone of the Marines. The most notable however of them all was when the Straw Hats, the Galley-La foremen, and the Franky Family decided to put aside their differences in order to ally themselves against a common enemy as presented when Luffy, Paulie, and Zambai crossed their arms together in a sign of allegiance. This moment was a vital turning point between the three groups as the alliance would prove instrumental in the upcoming battle.

Despite all its speed, the Rocket Man was not able to catch up to the Puffing Tom to prevent it from reaching it's destination. It was however able carry the Straw Hats and their allies through the storm to the aforementioned destination, the never night island, Enies Lobby.

Invasion at Enies Lobby
The Rocket Man was very instrumental during the invasion, aiding the Straw Hats and their allies in the battle in ways that left onlookers stunned.



After waiting the agreed five minutes, the Rocket Man was steered into the direction of the Enies Lobby front gate. However, as the gate was closed by some Marines and Government Agents who noticed the speeding Sea Train, a drastic alternative was devised by Zoro. With Yokozuna's strength, a ramp was created out of the fence in front of the speeding train which enabled the Rocket Man to be flung over the first and second gates and crash into Oimo. This act apparently made all efforts of the Franky Family and Galley-La in opening those gates useless.

After crashing into the isle of Enies Lobby and being hit with a cannon shell, the Rocket Man was fixed up and put to use again. It then sped across the island to the court house where it barged in and apparently ran over Baskerville. Using the halfway extended broken draw bridge as a ramp, it made another momentous jump across the waterfall gap separating Enies Lobby and the Tower of Justice, carrying the Straw Hats along with it, and crashed into the tower. After that the Rocket Man was apparently beyond repair and abandoned in the tower. It was thus left behind in the tower during the escape from the Buster Call attack where it is presumed to have been destroyed by the hellish onslaught of the Buster Call.

Despite all its flaws, the Rocket Man proved to be a very useful instrument to the Straw Hats during their raid on Enies Lobby.

Trivia

 * The Rocket Man appeared as an attack used by Green Generals in the game One Piece: Unlimited Adventure.
 * The painted fangs and eyes are similar to the faces often painted on old war planes.
 * The Rocket Man's name can come from a variety of locomotives, all called Rockets, some of which were renowned for their great speed.
 * As Kokoro pointed out, once it reached its top speed she would no longer be able to control it. In real world terms it would essentially be considered at this point a "runaway train". This is a term applied to operating trains that continue along on a track with humans being unable to control its path or speed leaving the train at the mercy of whatever lies ahead of it.