I've been looking for a way to take down a UFO without doing any (or little damage) to it as possible. I haven't found any research that would help me either. My question is, is there some weapon that I can research that will act like an EMP against UFOs? It's quite difficult to get Elerium-115 in the game and I was hoping that I could just EMP or do something that can take it down without destroying all of the Elerium-115.
In original version of UFO Enemy Unknown/ Defense there is no EMPs. Best strategy to get UFO without damage is raid them when landed. You can send Skyranger, Avenger or Lightning to purse UFO but minimize the fight screen when you catch the UFO. So your ship will follow them and if landed the UFO Mission will start right away.
Using weaker fire power weapons could also help you to more likely get UFOs down without blowing up their Power Sources. This if of course against smaller UFOs. Larger UFOs still might have some intact power sources even if some of them are blown up. *Note: No resarch done, just my own intuation from years of playing*
Like Nurkka mentioned it is not possible to crash an UFO undamaged. Personally i never noticed any relation between weapon types and damage. If you have the ability yo identify what type of ship it is you can tell if it will land in a random location (scouts), create a terror site (terror ship) or dock in an alien base (supply ship).
Always crash a supply ship or it will disappear in an alien base, you can also tell if there is a base if these ships suddenly disappear of radar.
Terror sites can yield a good amount of points so it is your choice to down a terror ship or not.
Scouts will most likely land somewhere so you could just chase them with a "crew" ship and once they land you enter the site.
Other then that, if you are after huge amount of alien supplies you can build a base fairly close to one of the alien bases. You will pickup all there supply ships and they offer tons of goodies for you.