The transport has six engines that power its flight down the tunnel- and the Dominion quickly breach the tunnel walls, sending in various airborn transports and fighters to shoot at its engines. You will need to keep an eye on the radar screen in the bottom-left corner of your monitor and respond to each approaching enemy. Generally, you should save Sarah's Kinetic Blast for the enemy troop transports, though you can occasionally splurge thanks to the recharging aid stations present on the transport. Keeping Sarah near the center of the platform when you're not having her shoot something is generally a good idea, making it easier to respond to any given part of the transport more quickly.
Presently, the transport will leave the tunnel, which is the start of the harder portion of the mission, when enemies will fly in more frequently. Try to limit your use of the aid stations, since they only recharge after a set time period- leaning too hard on them may mean not having access when you really want it. Later medevacs may drop in siege tanks, so be ready for that as well.
Once the transport finally arrives, a marine approaches Jim and Sarah to tell them that the Dominon has landed some kind of a 'mech in the shuttle bay, so you're going to need to have the two follow that squad in to take out the very last block to their departure.
When you arrive, a medic will heal Jim and Sarah, but then you're going to have to deal with a serious issue- the strange 'mech is some kind of super-viking, able to attack both on land and with aerial strafing runs- and it's huge, as are its shots. When Kerrigan moves in to help shoot down the 'mech- named Archangel- its bombardment destroys not only the defending siege tanks, but also the bridge, stranding Jim away from his ship and Kerrigan on the dock with the massive machine. The thing always makes its attacks obvious before they land, so it's relatively easy to avoid most, if not all, of the damage and wear the thing away with successive Kinetic Blasts, particularly given the aid stations present.
Once the Archangel is destroyed, there's a conversation between the three main characters thus far- Jim can't reach the dock, and Valerian is sending a team to help Jim out- but they wind up cut off by a Dominion team. Jim says he'll find his own way out, telling Valerian to head off without him. Unfortunately, just after that Nova shows up, prepared to take Jim down....
