The Noah Unit Cannon Experimental Unit Cannon is a UEF major experimental structure. It's a combined factory and artillery installation (range equal to the Long Range Artillery) which launches the units it constructs across the map. It manufactures them into shells which are stored in large magazines (it can hold a total of 21 units at a time). When launched, the "projectiles" fly in a ballistic arc to just above the target location, then break open and deploy the unit contained unharmed.
Units produced with this structure are built with a third of the cost and 1/7th of the buildtime. This means that it should be utilized over factories for unit production, as it can take the place of several land factories..
It is a very common mistake to fire the Unit Cannon into a protected base. It cannot be stressed enough: field your army outside of your enemies base! Only fire into a defended base if the point defense is already occupied. Similiarly, if the enemy's point defense is occupied (you or a team mate is attacking the base), then launch the unit cannon there for maximum effect.
The units can be fired through shields without a problem. However since the units are fired in sequence it is best to not launch them directly into the field of fire of a large number of enemy defenses. Scout an enemy base before launching, to find the ideal landing point.
Coincidentally, loading a single unit into the Unit Cannon then firing, over and over, can be an effective way of scouting.
The Unit Cannon can block your opponent from escaping. Fire units behind an aggressive force and snare them in the cross-fire between the launched units and your base defenses.
Build and simultaneously employ multiple Unit Cannon's once you are able. 21 Land Units launched into an enemy base may destroy a number of defenses and factories before being destroyed, but 42 or 63 can overwhelm most defenses and may even end the game should they land near the enemy ACU.
Use Launched units to destroy all anti-missile defenses in an enemy base, then deliver the finishing blow with a Nuke.
It is worth utilizing the Unit Cannon instead of factories only in the latter stages of a game. The Unit cannon requires a total of 28 research points to unlock. Some may not consider this worth doing, as you are sacrificing valuable points which would normally be used to put into basics such as land Training I/II etc. Use your early points on standard unlocks. If you manage to get comfortable later in the game, only then is it worth unlocking. Not putting points into standard Training etc. may be so detrimental in early battles, that you would likely get defeated before having the chance to unlock the Unit Cannon.
As mentioned earlier, the Unit Cannon builds all standard land units at 1/3 the cost, and 1/7 of the time. Therefore, in theory, one Unit Cannon can field an army nearly seven times faster than one factory.
The Unit Cannon requires significantly more micro-management than a land factory. Unit cannons can have a unit queue on repeat (exactly like a land factory), however once a Unit Cannon has build its 21 units and is at capacity, units will not automatically be fired. You must manually instruct the Cannon to fire on a specific area.
The Unit Cannon pays for itself (mass saved exceeds mass invested) by the end of the third full volley of rock heads.
Keep in mind that relying purely on 1 or 2 Cannons can be detrimental, as if you lose one of two Cannons, you've instantly lost 50% of your unit building capacity. Although once the unit Cannon is built, it's advisable to strike your opponent as soon as possible, to avoid your Cannons ever being under threat.
Engineers can be placed to assist Unit cannons just like factories. It takes 57 seconds to fill with rock heads, but only 43 seconds with a single engineer assisting. A second engineer decreases the time to only 40 seconds, and anymore is useless. Keep in mind that because units must be launched (which has an unmitigatible time) engineer assistance is slightly less useful then it may appear on paper (though still a good idea).
A novel strategy is to load it with Field Engineers and deploy them to your army if things aren't going so well for a quick repair boost, or to shore them up during a break in the fighting. Particularly useful if you have some Fatboys or Kriptors to keep alive during an important assault.
Anti-air can hit units before they hit the ground, so it's best to launch units away from even anti-air defenses.
The barrel of the unit cannon takes some time to turn towards its target. Take this into consideration if trying to synchronize several unit cannons. (additionally, the launch time of each unit is about 0.2 seconds, iirc)
Noah Unit Cannons are fantastic attrition units. Because you can land in the rear of your opponent's base instead of the front, you are almost guaranteed to destroy a sizeable number of buildings before your forces are eliminated. By the time your attack force is eliminated (especially with 3+ Noahs working together), you'll have another one.
Protect your base from unexpected attacks. Because of the unit cannon (and space temple) an enemy army can arrive anywhere, any time. Utilize power detonate and electroshock to mitigate the threat of this.
If your base is under attack, you can use the Noah to launch units behind the enemy forces. Just be wary of some units with anti-air.
The tips above are also useful for the one on the opposing end of a Noah.
Be aware if a Noah's being used. If you see a seamless line of enemy units travelling in a arc to your base by your radar, truth to behold, the enemy is DEFINETLY not using transports.
The Noah has impressive range and a constant user can be a threat to your base's security. To prevent 'back-stab' attacks by it. Construct point defenses at vulnerable areas and assign some patrolling engineers or Engineering Tower upgraded Power Plants to maintain the defence.
The thing itself is quite a large target. Send a scout in before relaying any long range artillery to start bombarding it. It should remove the threat altogether.
As mentioned above, mid-air units are vulnerable to AA defenses. Have some fighters intercept the incoming units or set up AA guns at heated drop-zones.