A deployable raceway harness assembly for use with a multi-stage rocket includes a first cable bundle configured to extend across a second stage of a multi-stage rocket from a guidance unit to a first stage of the rocket. The deployable raceway harness assembly includes a deployable raceway cover configured for detachable coupling with the multi-stage rocket. The deployable raceway cover extends over at least the first cable bundle and a second cable bundle. The first cable bundle is fastened to the deployable raceway cover. The second cable bundle is configured to extend from the guidance unit to the second stage and is shorter than the first cable bundle. An in-flight deployment mechanism is configured to detach the deployable raceway cover and the first cable bundle extending across the second stage from the multi-stage rocket in-flight leaving the second cable bundle extending to the second stage in place.