Number 1 Ionium Jet

The #1 Ionium Jet is a ship part in Pikmin. This is a jet that the S.S. Dolphin needs to propel itself through deep space. Olimar is worried that it is damaged and notes to run a system check as soon as he can. After being collected, this Ionium Jet is placed on the ship's hull, to starboard at the main hatch's level (behind and to the right of Captain Olimar when he is seated).

Although there is no part with this name in Olimar's Shipwreck Tale in, the Ionium Jet in the Sun-Speckled Terrace is analogous to the #1 Jet in appearance and function.

Collecting the part
This ship part is found in The Forest Navel. Take at least fifteen Blue Pikmin and go south from the landing site; there will be a pool of water. Face to the right and go down the cliff with the pipe with bomb-rocks inside of it and look to the right, where it will be sitting in the water. Proceed to carry it back to the ship. A gate in the path of the ship part will also have to be broken down, as the Pikmin will refuse to carry it off the ledge facing the gate.

An alternative way to obtain the piece is to build the climbing stick at the north of the area, and have some Blue Pikmin climb it. Group moving can then be used to control the Pikmin from below and direct them from that pool to the one to its west, where the jet is. Dismissing when they're close to the part will make them go towards it and start carrying it.

Trivia

 * In real life, ionium is a radioactive isotope of, with a mass number of 230.