The next SpaceX commercial resupply mission (CRS-3) to the International Space Station (ISS) is now scheduled for no earlier than (NET) April 14. This mission and other launches had been delayed due to a fire at a radar site of the Air Force Eastern Range, which supports both government and commercial launches. Also affected was a ULA Atlas V launch of launch of an National Reconnaissance Office (NRO) satellite, but this is now slated for April 10.
For CRS-3, the launch vehicle is a Falcon 9 v1.1 with nine Merlin engines, generating a total of 1.3 million pounds of thrust at launch and increasing to 1.5 million has it reaches the vacuum of space.
It will launch a SpaceX Dragon capsule with 4,600 pounds of supplies and payloads to the ISS. The Dragon will later bring back 3,600 pounds of cargo to Earth. Experiments going to the station include a vegetable production system (can it produce food that is safe to eat?) and a T-cell activation study related to the human immune system in microgravity. Several CubeSats are also being delivered to the ISS for deployment into orbit.
While it is not in any of the NASA press materials, one part of the launch being watched very closely is the first stage. This Falcon 9 first stage has landing legs. After it has sent the second stage and Dragon on their way, the first stage will prepare for re-entry to the Earth’s atmosphere. At some point, a number of Merlin engines will be re-lit to forcibly bring it back to Earth. The first stage has to survive the re-entry, and the engines have to be lit again as it hurls toward the ocean below.
In an ideal case, the Falcon 9 will light up the night sky and dance above the water before the engines are shut off. But it probably will not get far this time. SpaceX acknowledges that landing the first stage on land is the eventual goal, but there are a lot of hurdles to cross. It is much more likely that this will be the first of several attempts as SpaceX discovers what the engineering issues are with re-entry, re-light before and after entry, and deploying landing legs that have been through the searing hot trip. Rocket engines naturally operate in very hot conditions, but not normally with a headwind of dense ionized plasma coming at them.