An Asteroid Defense System cannon (abbreviated as ADS cannon) is a mass driver-operation delivery system, primarily used to eliminate asteroids and other hazardous objects.
A typical ADS cannon is made of two barrels that can 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 is to automatically track and destroy debris, preventing damaging collisions with the ship. The ADS can be disabled, but not if one or more of the cannons is malfunctioning. However, if it is disabled, the cannons can be manually controlled. When this occurs, the hull integrity is displayed for the person controlling the cannon. Also, the controller must be cautious when firing the cannon because, unlike the ADS, they can 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 debris from Aegis VII's Planet Crack while it regained its 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 Comm Array. Once the Slug was removed outgoing communications were restored.
- When firing at larger asteroids it is advisable to use both of the barrels to destroy the asteroids, while smaller ones can be easily destroyed with one barrel.
- Do not fire if there is nothing to fire at!
- A lot of debris that can be shot doesn't inflict damage to the hull: only the asteroids flying closer to your location seem 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 its tentacles every two seconds. If done correctly, it won't have time to hurl any explosives or debris at the Ishimura because the tentacles are constantly staggered.
- The Slug's tentacles won't last long against concentrated dual barrelled 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 does 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 has only been encountered on the PS3 version of Dead Space and is likely a bug that hasn't been patched.
- While the term "mass driver" technically describes any device used to propel a ballistic payload (that is to say, a projectile that is not self-propelled) the mass driver technology mentioned by Hammond when using the ADS presumably functions similarly to today's non-rocket spacelaunch technology.
- "Miniaturized" mass drivers can 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 is the one who turned the cannons off so he and his crew could flee from the USG Ishimura without being shot at by the cannons auto-fire mechanism, but Isaac Clarke comes back soon after to turn them back on for defense against asteroids that are hurtling towards the ship.