Following an ontime liftoff at 10:21am on Sunday morning, a SpaceX Falcon 9 rocket carrying an unmanned Dragon cargo vehicle broke apart over the Atlantic Ocean. Falcon’s first two minutes of its flight to the International Space Station were flawless; however, approximately 139 seconds into the mission and just prior to the first stage separation, the vehicle disintegrated.

This is the first failure of the Falcon 9 for the California-based SpaceX. Since its maiden liftoff in 2010, the company has celebrated a total of 18 successful launches. The Falcon 9 rocket is composed of two stages, with the first stage shut down—also known as main engine cutoff (MECO)—occurring approximately 159 seconds into the flight. However, approximately 20 seconds before that, the vehicle experienced an anomaly.

SpaceX CEO Elon Musk posted an update soon after saying, “Falcon 9 experienced a problem shortly before the first stage shutdown. There was an overpressure event in the upper stage liquid oxygen tank.”

In a post-incident press briefing, SpaceX President Gwynne Shotwell told members of the media, “We do not expect this to be a first stage issue. We saw some pressurization indications in the second stage which we will be investigating.”

On screen telemetry posted during the live webcast showed the vehicle reached an altitude of 45 kilometers and traveled approximately 4,700 kilometers per hour. The launch footage appears to show the Dragon separating from the Falcon following the anomaly. Shotwell added, “We did receive telemetry from Dragon after the anomaly occurred.”

Dragon was loaded with more than 4,000 pounds of cargo, including research experiments, crew supplies, and hardware for the space station. In Dragon’s unpressurized trunk was a key piece of hardware: the first of two International Docking Adaptors (IDAs). The IDA is part of a station reconfiguration essential for enabling multiple vehicles to use the same docking ports on the orbiting outpost—including SpaceX’s crewed Dragon and Boeing’s CST-100 spacecraft. A second, identical IDA is slated to go up on a future SpaceX mission.

In a post-launch briefing, William Gerstenmaier, NASA’s human exploration division associate administrator told reporters, "This is not really where I wanted to be on a Sunday afternoon. But spaceflight is not easy, and we don’t want to make light of this. We lost a lot of important research and equipment on this flight. We lost the IDA, a water purifier, and a spacesuit. We have to see how we can recover from that.”

The Dragon is the third ISS-bound cargo vehicle lost in the past eight months. In October 2014, an Orbital-ATK Antares rocket exploded just after liftoff. Exactly six months later, in April 2015, a Russian supply vehicle failed to make it to orbit.

"There's really no commonality across these three events," Gerstenmaier said, "other than the fact space is difficult. This shows the difficulty and challenges we face every day going to space. SpaceX and the ISS team performed everything exactly right. Space is a demanding environment and we are pushing the vehicles to the limit every time we launch.”

ISS program manager Mike Suffredini told members of the press, “We’ve always assumed we would lose cargo vehicles along the way, as getting to low-Earth orbit is challenging. We just didn’t expect we would have three losses in one year.”

Right now, the space station has enough provisions to support a crew of six until October, even if no other supply ships make it there. The next supply ship, a Russian Progress, is scheduled to launch on July 3, with a Japanese HTV vehicle to follow in August. There are only three crew members currently on station—NASA astronaut Scott Kelly and Russian cosmonauts Gennady Padalka and Mikhail Korneinko—with the next trio set to launch on July 23.

SpaceX is currently partnering with the FAA for a mishap investigation to determine what exactly caused this anomaly. When asked about what went wrong, Shotwell said, “I don’t want to speculate as to what happened, because we haven’t pinpointed what happened yet. I’m sure we will determine what happened, and will return to flight as safely and reliably as possible.” Pending the outcome of the investigation, all future flights on the Falcon 9 have been grounded until crews can get to the root of the problem and address it.

NASA Administrator Charlie Bolden issued a statement following the launch, stating, “SpaceX has demonstrated extraordinary capabilities in its first six cargo resupply missions to the station, and we know they can replicate that success. We will work with and support SpaceX to assess what happened, understand the specifics of the failure and correct it to move forward. This is a reminder that spaceflight is an incredible challenge, but we learn from each success and each setback. Today's launch attempt will not deter us from our ambitious human spaceflight program.” Both SpaceX and NASA expect to recover from the failure and return to flight quickly.