Beta 0.5 is the first public demo of Sigma released.
Beta 0.5 features the V.R.A. as a playable race add on for Star Trek: Armada II.
Beta 0.5 requires a fresh install of stock A2 and both the 1.1 and 1.25 patch.
Beta 0.5 released on May 31st, 2009 and can be downloaded here: http://armada2.filefront.com/file/Sigma_Demo_The_VRA;100001