Emergency Boarding Procedures
From Halopedia, the Halo wiki
While entirely possible on solo, it is most easily done on co-op. Two players need to stick together while going into the Kraken, destroying its power core, and then escaping. One player should be piloting the Phaeton away fron the Kraken while the other should be standing on the Phaeton. The Phaeton's pilot must not use the teleport ability so as to not accidentally knock the other player off the vehicle. The players do not necessarily need to reach the Forerunner facility to unlock the achievement, as simply getting several hundreds of feet away from the Kraken will unlock the achievement, so long as one player is standing on the Phaeton.