The RX-78-4 Gundam Unit 4, more commonly referred to as "G04", was more advanced in many ways than its more famous predecessor. The Federation decided to convert the Gundam units 4 and 5, which were already in development, into space combat versions for use as main forces in the invasion of Solomon, A Baoa Qu, and then Zeon itself. These machines based on the RX-78-2, and the replacement of the backpack and the addition of thrusters and propellant raised their mobility by roughly 40 percent. Their operating time was also extended, and it was anticipated that they would produce great combat results during lengthy battles, especially in attacks on space fortresses.
The biggest change was the elimination of the core block system. The space freed up was used for cooling systems, thus increasing the generator output and enabling the use of more powerful beam weapons. As a result, the armament was upgraded to include a hyper beam rifle, and one beam gun was installed in each forearm. Plans were also made to equip unit 4 with a powerful, long range mega beam launcher.