Spaceship
Space Shuttle, Starship, Ufo, Spacecraft, Flying Saucer
You know how 宇宙 is outer space and how 船 is ship, right? Well, put those together and you have an outer space ship (better known as a space ship).
うちゅうせん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. It will help to know the word 宇宙 beforehand as well.
十六台の宇宙船のほとんど全てが、保持され改装されました。
Nearly all of the sixteen space ships were retained and refurbished.