UFO Behaviour<title> <head></head> <body> <h1>UFO Behaviour</h1> <br> To begin, UFOs have the following mission types: <li>Alien Harvest</li> <li>Alien Research</li> <li>Alien Abduction</li> <li>Alien Infiltration</li> <li>Alien Terror</li> <li>Alien Supply</li> <li>Alien Base</li> <li>Alien Retaliation</li> <br> The <b>Harvest</b>, <b>Research</b> and <b>Abduction</b> missions are similar. <li>UFO starts at a random location on the globe</li> <li>UFO proceeds to target site</li> <li>At target site, UFO lands, and waits for a bit. (How long is "a bit"?)</li> <li>UFO takes off again, moves short, random distance away</li> <li>Lands and waits for a bit.</li> <li>Steps 4 and 5 are repeated a number of times</li> <li>UFO moves to departure point</li> <li>UFO leaves Earth</li> <li>If UFO is disturbed at a landing site, it will proceed to departure point and leave earth.</li> <li>If UFO is attacked while in the air, and not destroyed, it will continue on its mission.</li> <br> Notes: <li>The number of landings is variable. Usually either 0, 1, 2, or 3 times</li> <li>The UFO never starts it’s mission at an Alien base</li> <li>The only time a UFO ends at an alien base is when it is a supply mission.</li> <li>Once the Supply Ship finishes stocking the base, it immediately leaves.</li> <li>Departure/start points are random points on the globe and AFAIK they never are the same.</li> <br> The <b>Alien Infiltration</b> mission is: <li>UFO starts at a random location on the globe</li> <li>UFO proceeds to target site</li> <li>If UFO reaches target site, UFO disappears.</li> <li>If UFO is attacked while in the air, and not destroyed, it will continue on its mission.</li> <br> The <b>Alien Terror</b> mission is: <li>UFO starts at a random location on the globe</li> <li>UFO proceeds to target site</li> <li>If UFO reaches target site, it lands, and landing zone becomes a terror site.</li> <li>After a period of time, UFO takes off, moves to departure point and leaves Earth.</li> <li>If UFO is attacked while in the air, and not destroyed, it will continue on its mission.</li> <br> The <b>Alien Supply</b> mission is: <li>UFO starts at a random location on the globe</li> <li>UFO proceeds to target location. Usually beside, but not IN, an Alien Base</li> <li>If UFO reaches target site, it lands.</li> <li>After a period of time (how long?), UFO takes off, moves to departure point and leaves Earth.</li> <li>If UFO is attacked while in the air, and not destroyed, it will continue on its mission.</li> <br> The <b>Alien Base</b> (construction) mission is: <li>Scout UFO starts at a random location on the globe</li> <li>UFO proceeds to target site</li> <li>At target site, UFO behaves like a research mission.</li> <li>After a while, UFO leaves</li> <li>Steps 1 to 4 are repeated for a number of “surveying” UFOs</li> <li>A little later, a Battleship UFO starts at a random location on the globe </li> <li>Battleship proceeds to target site</li> <li>At target site, UFO lands.</li> <li>After 4 to 10 days, UFO leaves, and an Alien base is left at the site.</li> <br> The <b>Alien Retaliation</b> mission is: <li>“Scouting” UFO starts at a random location on the globe</li> <li>UFO proceeds to target site (somewhere near when Alien thinks X-Corp base might be.)</li> <li>At target site, UFO starts searching the area for a base.</li> <li>If scout is destroyed mission ends.</li> <li>If scout fails to locate base, mission ends.</li> <li>If a base is found, scout leaves area, and</li> <li>Battleship UFO starts at a random location on the globe</li> <li>UFO proceeds to target site (the base)</li> <li>If attack on base is successful, UFO flies to departure point and leaves Earth.</li> <br> Other notes: <li>UFO's never directly attack X-COM craft. X-COM is always the initiator of air-to-air attacks.</li> <li>Non-Retaliation UFOs do not detect the presence of X-COM bases (it's not their job). Retaliation scouts do the actual detecting, and according to the OSG have a detection range of 240 nautical miles.</li> <li>UFO crash sites last anywhere from 1-4 days on a map.</li> <li>Landed UFOs stick around for 4-12 hours, but this number is highly variable and probably depends on mission type and previous X-COM activity on the mission.</li> <li>Terror sites last anywhere from 4-10 hours, ut there is a bug in the game allowing you to extend the time-frame to infinity by always having at least one ship headed to the site at all times.</li> <li>Technically, on infiltration/base building excercises, the alien base is constructed before the Battleships arrive.</li> <h1>Multiple UFO behaviour</h1><br> According to MISSIONS.DAT in UFOpedia, UFOs generally don't work in isolation.<br> As discussed in the terror and alien base missions above, a a "mission" (or as shown in AIandCraftClasses.png, an "Invasion Task" involves a number of UFOs over a period of time.<br> <br> So, the sequences are:<br> <h3>Research</h3> <li>small scout</li> <li>1 week later, a medium scout</li> <li>1 week later, a large scout</li> <li>3 days later, a large scout</li> <br> <h3>Harvest</h3> <li>s.Scout</li> <li>3d s.Scout</li> <li>1w s.Scout</li> <li>3d l.Scout</li> <li>3d l.Scout</li> <li>1w Harvester</li> <li>3d Harvester</li> <li>1d Battleship</li> <br> <h3>Abduction</h3> <li>s.Scout</li> <li>1w m.Scout</li> <li>2w l.Scout</li> <li>3d Abductor</li> <li>3d Abductor</li> <li>1h Battleship</li> <br> <h3>Infiltration</h3> <li>s.Scout</li> <li>2w m.Scout</li> <li>2w m.Scout</li> <li>2w l.Scout</li> <li>3d l.Scout</li> <li>1h Terrorship</li> <li>1h Battleship</li> <li>1h Supply</li> <li>1h Battleship</li> <br> <h3>Base</h3> <li>s.Scout</li> <li>m.Scout</li> <li>l.Scout</li> <li>Supply</li> <li>Supply</li> <li>Battleship</li><br> if you shoot down the supplys the battleship will not come for several weeks and a retaliation mission is started. <br> <h3>Terror</h3> <li>m.Scout</li> <li>1w l.Scout</li> <li>1w Terrorship</li> <li>1w Terrorship</li><br> Each Terrorship will cause one terror mission, if it is not shot down before it lands. <br> <h3>Retaliation</h3> <li>s.Scout</li> <li>? m.Scout</li> <li>32h* m.Scout (<i>add 146.5h* if 1/0 shot down at first turning point</i>)</li> <li>52h* l.Scout (<i>add 3d if 1/1 shot down at first turning point</i>)</li> <li>? l.Scout</li> <li>? Battleship</li> <li>? Battleship</li> </body>