There is a photo manual for building it at the bottom of this page.
The archeologists and historians who were exploring Moon Base Bravo used a Mantax for their journey. Designed as salvage vessel, Mantax were incredibly robust, and they turned out to be very easy to maintain, operate and modify. On top of that, they packed a decent cargo hold. All in all, it was quite a versatile ship, which made it extremely successful. Besides with transport and salvage companies, they were popular with space liners and shipping companies, most navies and even asteroid miners. Then there were the treasure hunters, smugglers and space pirates. Because of their popularity and durability a blooming second-hand market had sprung up and since the explorers were not very well funded, they settled for a medium-sized second-hand that clearly had seen a lot of action.
Okay, here is the thing about Lego space ships: they are easy. Since nobody knows what a space ship should look like, anything goes, whether the design makes sense or not. Take any box or frame, add antennas, greeble bits, cockpit or bridge, guns, engines, wings and what have you, and tadaaa: space ship. Well, … unless of course they are models of existing space ship design. If you want to make the Millennium Falcon it should look like the Millennium Falcon. The Mantax is somewhere in between. I didn’t start with the idea to build a Manta-shaped space ship. I just started figuring out how the wedge and the quarter circle plate could fit together, and suddenly there was a Manta. You may not find it looking like a Manta at all. That is fine. After all, it is a space ship…
You can make the Mantax with the bricks of the Millennium Falcon Microfighter (75030)