If you can get to the center, plant your one bomb and try to find your way out. The object of Cosmic Chasm is to complete each Mission by destroying the power source at the center of a planet. When a Mission starts, you are shown a map indicating your ship's position on the planet. You have to quickly figure out the fastest route to the octagon in the center of the map, which represents the power source. Each diamond on the path represents a cavern you must fight your way through to reach the power source.
All caverns look similar.
In the center is an core that continually expands. If you don't get out of the cavern quickly enough, you'll be crushed against the core or the cavern walls, either of which will destroy you. You also have to contend with the eight Planet Protectors, diamond-shaped ships that home in on you. Blast the Planet Protectors with your dual cannon, which fires missiles that fan out from the sides of your ship. You can fire multiple salvos at once, and while you can blanket the screen with firepower, the Protectors are so small that they have a tendency to squeeze between your missile spreads and ram your ship.