The Beam Rocket is a tall rocket craft powered by two pairs of rocket engines. It is composed of three sections with a cockpit set on top. The cockpit is guarded with a sparkling, possibly electric spiked ball that changes shape while hovering above it. The top and center sections have two laser beam cannons rotating around the sides.
The Beam Rocket is the second of three bosses fought at the end of Launch Base Zone Act 2, and takes nine hits to be destroyed. The boss battle takes place on a platform suspended below the Death Egg as it gets re-launched. If playing Sonic the Hedgehog 3 and not the full game Sonic the Hedgehog 3 & Knuckles, the Big Arm boss is fought immediately afterwards as the final boss (the boss is removed from Sonic and Tails' playthrough and is instead fought by Knuckles).
During gameplay, the Beam Rocket will either come down from above or rise up from below on the sides of the screen. The primary weapons it uses are the laser cannons, which will fire twice each time Dr. Robotnik passes across the screen. The craft is most easily attacked when it is rising up from below the floor, as the only part of it that is vulnerable to attacks is the cockpit. However, the player must watch out for the morphing spiked ball that orbits above the cockpit.
Unlike other regular bosses, nine hits are required to defeat the Beam Rocket - four hits destroys the top part of the rocket, another four destroys the middle section, and the ninth hit destroys the whole craft.
If the player is playing Sonic the Hedgehog 3 the final boss battle takes place directly afterwards. Dr. Robotnik's Egg Mobile will rise up and attach itself to the Big Arm as the sky darkens ominously. In the locked-on version, Sonic the Hedgehog 3 & Knuckles, Sonic completes Launch Base Zone after defeating the Beam Rocket, while the cutscene showing the score results afterward is the same. Sonic and Tails will end up in the Mushroom Hill Zone after staying on the platform.
In Knuckles' scenario, Knuckles fights this boss in a different upper section due to the Death Egg being relaunched and destroyed before Knuckles' storyline. EggRobo controls the craft, while the tactics remain unchanged except that the morphing spiked ball starts at a different position for Knuckles, leaving slightly less opportunities for attacking the boss. After nine hits, EggRobo will fly up from the destroyed Beam Rocket to take control of the Big Arm.
In Sonic the Hedgehog 3, if the player controls Sonic along with Tails as a partner, Tails does not appear during this boss battle nor in the Big Arm fight, as he was left behind after the battle against the Ball Shooter. However, he appears alongside Sonic in Sonic the Hedgehog 3 & Knuckles.
In the locked-on version, Launch Base Zone is the only Zone in the game that does not have any Capsule to open after fighting this boss as Sonic or Tails.
This boss does not have an individual name in English sources; however, the three-tier boss structure of Sonic the Hedgehog 3 is known as Doctor Robotnik’s Final Challenge.