Update 4:10 p.m. EDT: SpaceX announced the reason for the launch delay was due to a helium leak on the Falcon 9 rocket.

Update 3:50 p.m. EDT: NASA announced it is has delayed Monday's SpaceX launch. The International Space Station Resupply mission has been pushed back to Friday with a launch window starting at 3:29 p.m. EDT.

The SpaceX International Space Station Commercial Resupply (CRS-3) mission is a go. The Dragon spacecraft launch live stream begins at 4 p.m. EDT while the NASA broadcast begins at 3:45 p.m. EDT. The launch window begins at 4:58 p.m. EDT.

Monday’s SpaceX launch was almost called off after NASA confirmed a backup computer aboard the ISS was unresponsive on Friday. The backup Multiplexer-Demultiplexer (MDM), located on the exterior of the ISS, was not responding to commands from ground control. The MDM faulty serves as a backup to the main computer responsible for controlling the Mobile Transporter system which is used to extend  the space station’s robotic arm, Canadarm 2, which will grapple the Dragon spacecraft and attach it to the Harmony node, notes NASA. The faulty MDM will be replaced during a spacewalk scheduled for, at the earliest, April 22.

The Dragon spacecraft, launching from Launch Complex 40 at the Cape Canaveral Air Force Station will arrive at the ISS on Wednesday and NASA is taking the necessary steps to receive the spacecraft even if the main MDM fails. The space agency will extend the Mobile Transporter on Monday and position the ISS’ solar arrays ahead of Wednesday. The CrS-3 mission has been delayed twice and was originally scheduled to launch on March 16 but was pushed back to March 30 to "resolve remaining open issue." The second delay was caused by a fire at Eastern Range which damaged radar components used to track rocket launches.



NASA has packed 3,347 pounds of cargo, supplies and scientific instruments inside the Dragon spacecraft. The payload includes a laser communications system,   Optical Payload for Lasercomm Science (OPALS), while the Vegetable Production System (Veggie) will turn the astronauts into farmers as they grow plants and lettuce from “pillows.” A smartphone controlled satellite, PhoneSat 2.5, will be included as part of the cargo and Falcon 9 will launch five CubeSats into orbit on Monday.

In addition to the scientific instruments, a pair of legs for the space station’s robotic astronaut, Robonaut 2, and a spare spacesuit will arrive at the ISS on Wednesday. For SpaceX, Monday’s Dragon spacecraft launch will also be a time for experimentation as it tries out the Falcon 9 rocket’s new landing legs.

Robonaut 2 Legs A set of legs for the space station's robotic astronaut, Robonaut 2, will launch to the International Space Station on Monday. Photo: NASA

According to SpaceX, the landing legs are the first step in their goal to create a reusable rocket. The company hopes to recover the Falcon 9’s first stage, which contains the nine Merlin engines that power the rocker, but puts the probability of success at 30 to 40 percent. SpaceX will attempt a reentry burn followed by a second, landing burn after the Dragon spacecraft has separated from the rocket. The landing legs will be deployed halfway through the procedure and, even if it fails, the company hopes to get a lot data it can use for future missions.

The SpaceX launch live stream begins at 4 p.m. EDT and can be viewed below.

The NASA live stream of the Dragon spacecraft launch begins at 3:45 p.m. EDT and can be viewed below.

The Dragon spacecraft is expected to arrive on Wednesday and will spend the next 20 to 30 days attached to the space station. During that time, the Expedition 39 crew will fill the Dragon spacecraft with science experiements and other supplies. After detaching from the ISS, the Dragon spacecraft will splash down in the Pacific Ocean.