Since you possibly have a Xeno character, starting either with the crew already assembled on the ship, space station, world in the Koronus Expanse, etc., is the best idea. This can allow you to go two routes: Lets the players decide the back story for how, when, why, and where they all met, to include the ork; or allows you the opportunity to decide how, when, why, and where they all meet to include plot devices for latter.
Example: The Ork player was left for dead on planet 3432Xy by a random NPC RT. The ork PC later rescues PC RT from a Clawed Fiend on said planet, while looking for a way off.
Another option, though it will be hard to do, is to have the RT receive his Warrant, ship, and crew at a certain location, and this is where they all meet for the first time.
Example: RT's father was killed during a boarding action involving DE while scouting solar system R6545Z. The ship is receiving repairs at a dockyard near Footfall along with fresh crew. The PC's are transported (or some were already there) for the Ceremonial ship launching, indoctrination of the new command crew, and void burial of the recently departed. The reasons why the PC's were picked were because that is who the Warrant backers chose to accompany the RT (they were the best of the best, the past RT owed them a favor, a "trust worthy" friend recommended them, etc. etc.). The Ork PC was already part of the original crew, but was severally wounded prior to the DE boarding and killing the RT's father. Seeing a challenge opportunity missed and not wanting to miss further ones (and maybe feeling remorseful), the Ork PC has agreed to another term of service to help the RT seek revenge. And also the shadier Power Backers for the Warrant want to see if this new upstart RT will continue the Cold Trade his father had started. While at the "Christening" of the ship, other merchants, traders, men for hire, and maybe more xenos, see an opportunity for more coin and business and will likely be present. To include a few fellow NPC RT's who want to say their condolences.
Obviously, this doesn't have to happen at Footfall. It could happen at Damaris, hours before the orks invade (hehe), at Svard prior to it becoming "infected," or another other place in the Koronus Expanse. The only reason why I suggest it's a place in the Koronus area, is because of the Xeno PC, other wise I would suggest it happening in the Calaxis Sector.
These are just ideas off the top of my head. Hope it helps some.