The Collapsible Grenade Launcher was a custom-built pump-action grenade launcher used by the crew of the Betty in the 24th century. Like all of the weapons utilized by the Betty crew, it was chiefly designed with concealment in mind, and it could be easily smuggled through military checkpoints undetected. When not in use, its disassembled parts were concealed about Vriess' P.T.V..
The Collapsible Grenade Launcher, as its name implies, could be easily disassembled into its constituent parts. When not in use, these parts were hidden on the P.T.V. used by the paraplegic Vriess, thereby allowing the weapon to be smuggled past security checkpoints.
Behind the Scenes
Like all of the weapons created for Alien Resurrection, the Collapsible Grenade Launcher was not built around any existing firearm but was fabricated completely from scratch. This was a markedly different approach when compared to the fictional weapons that had appeared in the film series previously, all of which were constructed around functional, real-world weapons. In fact, the Collapsible Grenade Launcher props contained no genuine firearm components whatsoever. Instead, a combination of CGI and practical effects were used to simulate the weapon firing.