I saw this thing on the Military Channel and I thought it looked cool. But the question is have is, why do they have 3 different versions of it? Wouldn't it make more sense to have all the services using a vertical takeoff jet? I know nothing about this, so I'm just curious.

i think ur reffereing to the f-35 and if so the reason is (im pretty sure) that they have the 3 different versions of the plane is purely for the fact they need to perform different roles... e.g the airforce (i think thats the one with out vertical takeoff) version probably doesnt need vertical takeoff because it would be unnessecary due to the plane always being used from air bases, with long runways... it would just be an extra unused part that could stuff up... but this is just my opinnion from what ive hear and read about the f-35 lightning...

The more payload on the plane the more space needed for take-off.

So if the plane is fully loaded, it probably needs a rolling take-off.

I think the Marines are the only service that is getting the verticle take off version.

Here is a link with more info

http://en.wikipedia.org/wiki/F-35_Lightning_II

th f35 lighning 3 varrients are

f35-A airforce varrient

f35-B marine varrient has STOVL abilities because the marines always need a aircraft that can take off from assault ships and close in areas.(the marines need it for close airsupport because they are always in or two steps away from the fight)this also will be bought by the royal navy to replace harriers

f35-C navy's carrier varrient it has a larger wing area and span for carrier landing.
the A varrient has a internal 25mm cannon, while as the B and C has a gunpods, the B model can't carry as heavy ordanace as the A and C. i think i might be wrong but they also can mount exterior weapons pylons at the expense of stealth.