Nexus - The Jupiter Incident Demo

As seen at the official Nexus site:

The Battle at Stonehenge

The Gorgs, a wild, militant warrior-race, have attacked battle station Stonehenge in the Cyrus System. You, in charge of the defenders of the battle station, are facing critical numerical superiority. Three tiny base-defending frigates and one small tactical destroyer are the remaining forces of the human fleet. Your ships only have limited weaponry; you and your fellow humans need help. Either your ships rely on their speed and succeed in breaking through the blockade, or you launch a surprise attack on the enemy and destroy the radio jamming device.

Be a part of events prior to the release of Nexus - The Jupiter Incident! Familiarize yourself with a small group of characters from the game! Lead them to victory!

The demo is one mission and can be played on three difficulty levels. With a couple of ships at your disposal you need to defend a space station while trying to get help and not be noticed by your enemies, the Gorgs. Pay close attention to all communications as you are thrown into the action immediately.

The official site lists mirrors; Blue's also has a list.