An Asteroid Defense System cannon (Abbreviated as ADS cannon) was a mass driver-operation delivery system, primarily used to eliminate asteroids and other hazardous objects.
A typical ADS cannon was made of two barrels that could be fired separately. These cannons are usually put on Planet Cracker class ships in a large fixed array called an Asteroid Defense System or ADS. The primary goal of this system was to automatically track and destroy debris, preventing damaging collisions with the ship. The ADS could be disabled, but not if one or more of the cannons was malfunctioning. However, if it was disabled, the cannons could be manually controlled. When this occurred, the hull integrity was displayed for the person controlling the cannon. Also, the controller must be cautious when firing the cannon because, unlike the ADS, they could potentially overheat the barrels preventing the cannon from functioning until cooled down.
There are two known instances on board the USG Ishimura of the ADS Cannons being manually controlled:
- ADS Cannon 47: Isaac Clarke used this Cannon to defend the Ishimura against the debris from Aegis VII's Planet Crack while it regained it's orbit. He only had to hold out until Zach Hammond fixed the automatic targeting.
- ADS Cannon 48: Isaac used this Cannon to defeat the Necromorph known as the Slug which was covering the Communications Array. Once the Slug was removed, communications are restored.
- When firing at larger asteroids, it was advisable to use both of the barrels to destroy the asteroids while smaller ones could be easily destroyed with one barrel.
- Do not fire if there was nothing to fire at!
- A lot of debris that could be shot did not inflict damage to the hull. Only the asteroids flying closer to your location seemed to hit the Ishimura.
- Try to take small breaks between firing. This will decrease the chance of a barrel overheating.
- When fighting The Slug, try and hit all five of it's tentacles every two seconds. If done correctly, it will not have time to hurl any explosives or debris at the Ishimura because the tentacles are constantly staggered.
- The Slug's tentacles will not last long against the concentrated dual barreled fire.
- Three Achievements and Trophies are associated with ADS Cannons:
- "Don't get cocky, kid" - Survive the ADS cannon mission with over 50% shield strength remaining.
- "Get off my ship!" - Kill The Slug boss.
- "Slugger" - Kill The Slug boss with more than 50% shield strength remaining.
- While firing a single cannon did not cause the cannon battery to overheat, firing ADS Cannon 47 the same way during the Chapter 4 sequence will gradually make it heat up. This was only encountered on the PS3 version of Dead Space and was likely a bug that was not patched.
- While the term "mass driver" technically described any device used to propel a ballistic payload (That was to say, a projectile that was not self-propelled) the mass driver technology mentioned by Hammond when using the ADS presumably functioned similarly to today's non-rocket spacelaunch technology.
- "Miniaturized" mass drivers could also be used as weapons in a similar manner as classic firearms or cannons by using electromagnetism to function instead of chemical combustion.
- Nathan McNeill was the one who turned the cannons off so he and his crew could flee from the USG Ishimura without being shot at by the cannon's auto-fire mechanism, but Isaac Clarke came back soon after to turn them back on for defense against the asteroids that are hurling toward the ship.