The first stage of SpaceX's Falcon 9 rocket had a "rapid unscheduled disassembly" on a floating barge following the successful launch of two satellites Wednesday.

SpaceX chief executive Elon Musk said the crash may be the "hardest impact to date," but that the barge or "droneship," nicknamed "Of Course I Still Love You," is okay. He added that the (crash) landing video will be posted later today.

Ascent phase & satellites look good, but booster rocket had a RUD on droneship —@elonmusk

Landing video will be posted when we gain access to cameras on the droneship later today. Maybe hardest impact to date. Droneship still ok. —@elonmusk

The failed landing of the reusable booster rocket follows three successful "droneship" landings in a row and one landing on land, an easier feat.

Prior to that, several SpaceX rockets had crashed and exploded during landing attempts on barges.

Musk said that it looked like the thrust was low on one of the three landing engines today, and such landings are very sensitive to all engines operating at maximum thrust. But he said SpaceX is working on upgrades to enable a rocket to compensate for a thrust shortfall on one landing engine.

The company has been trying to develop rockets with a reusable first stage in order to save on launch costs.

A commentator on SpaceX's launch livestream noted that today's unsuccessful landing highlights the fact that the technology is still experimental.

The launch did successfully deliver commercial communications satellites from Paris-based Eutelsat and Bermuda-based ABS into orbit.

Second of two satellites being deployed into proper orbit with today's launch <a href="https://t.co/XcHFBPEyfk">https://t.co/XcHFBPEyfk</a> —@SpaceX

SpaceX says it plans to re-launch one of its successfully landed booster rockets this fall.