Wikia

The Thruster-Pack is a special rocket upgrade to Clank. It was fitted at Bob's Roboshack on planet Pokitaru for 2,000 bolts.

In addition to all of the Heli-Pack's basic moves, the Thruster-Pack had a built-in power-slam to open special locks in the ground. Furthermore, it also allowed Ratchet to hover above ground, giving the Lombax the capability of straifing and also a mid-air long-jump that could be used after high-jumping. These three functions were removed in all future games, though Ratchet instead strafed on his own. Aside from these features, it was able to perform high jumps and long jumps faster, though it had a faster rate of descent while gliding .

In Going Commando, the Thruster-Pack lost its power-slam function after Ratchet obtained Clank on Endako in the Bogon Galaxy. Due to both of its features that made it different from the Heli-Pack being removed, the Thruster Pack served absolutely no purpose in any game aside from Ratchet & Clank, other than being an aestetic choice for the player and also having a faster thrust. The Thruster Pack was, for some reason, absent in both Size Matters and A Crack in Time.