The Y-Rack is a "Y"-shaped launcher mounted on the Powered armor.
Starship Troopers novel
The Y-Rack was frequently mentioned in use during Raid on Skinnie Homeworld.
Starship Troopers anime
The Y-Rack is an optional equipment of the Soldier Suit. It can shoot a high explosive shell via the electrical magnetic catapult.
Because the launcher is shaped like "Y", the shell can be shot in three directions. In addition, the shell spins while been launched, so it can travel steadily without aiming.
The equipment can carry 18 shells. The power of each shell can reach 5 to 10 times of a hand grenade. The shooting range can reach 1.2 to 1.5 times of a hand grenade.
In the early design sheet, the Y-Rack was originally going to be mounted on the back of the Powered Suit instead on the left shoulder. 
Starship Troopers: The Miniatures Game & The Roleplaying Game
The M-4A1 Grizzly Exosuit is equipped with the Y-Rack.
- In Starship Troopers: Traitor of Mars, though not specific, a Power Suit has an optional hardpoint able to be mounted with Gatling gun, which can shoot backward like a Y-Rack.
- Starship Troopers (novel)
- Starship Troopers (anime)
- Starship Troopers: Terran Ascendancy
- Starship Troopers: The Miniatures Game
- Starship Troopers: The Roleplaying Game
- Starship Troopers: Dominat Species
- Page 74, Starship Troopers Memorial Handbook