The upgraded Falcon 9 will be slightly taller than the Falcon 9 v1.1 and have a 33-percent increase in performance, said Lee Rosen, vice president of mission and launch operations for SpaceX, in another panel session here Sept. 1. “It has the same engines that we’ve flown before, but with some upgrades and things like that to increase reliability and performance,” he said.
The first static firing of the upgraded Falcon 9's first stage with densified propellant, completed on 9/21/2015.
The updated version 1.2 engine design was already planned before the explosion, and SpaceX is taking pains to ensure that the struts don't fail again.
The new engines will boast an extra boost. According to Spaceflight Now, each of the nine engines on the Falcon 9 rocket will provide 170,000 pounds of sea level thrust—up from 147,000 on the previous version.
The new upgrades will help the rocket carry heavier cargo into space, and will hopefully leave enough propellant left over after the launch to do a controlled landing of the rocket's first stage. That would help to usher in an era of rockets that are reusable and hence, cheaper.
The Falcon 9 Upgrade involves changes throughout the rocket with the exception of the payload fairing and is not just a slightly modified Octaweb first-stage motor configuration and the increased thrust of the Merlin 1D engines.
The first stage landing legs have been upgraded and the first stage structure enhanced. The grid fins, to help guide the first stage to landing, sport a new design. The interstage structure is longer, the second stage Merlin Vacuum engine’s thrust is increased, its nozzle lengthened and the overall length of the second stage is increased.
SpaceX has said it will attempt a barge landing of the first stage used for the SES-9 launch, the first such attempt following a launch to geostationary transfer orbit, the destination of most telecommunications satellites.
SOURCES- Youtube, Spacex, Popular Science, Space News