A SpaceX representative told Business Insider, "We do not comment on missions of this nature, but as of right now reviews of the data indicate Falcon 9 performed nominally".

Last May was the first time SpaceX launched its first satellite for the US military with its Falcon 9 rocket.

"Falcon Heavy has been rolled out to launchpad LC-39A for a static fire later this week, to be followed shortly thereafter by its maiden flight", SpaceX president and COO Gwynne Shotwell said in a statement released yesterday.

A spokesman for Northrop Grumman Corp., which built the satellite, said Monday: "This is a classified mission". On Monday, Ars began to hear discussion from sources that the mysterious Zuma spacecraft-the objective of which was never specified, nor which U.S. military or spy agency had backed it-may not have survived. The satellite was lost, one of the congressional aides said, and the other said both the satellite and the second-stage satellite fell into the ocean after the failure. When SpaceX has had mishaps in the past, it's grounded the company for months.

Zuma was initially scheduled to launch in November but was delayed until the rocket and satellite were declared "healthy" for launch last week.

This was SpaceX's third classified mission for the USA government, a lucrative customer. The satellite could have stopped working on orbit - or, if it failed to separate from the second stage because of a problem, it could have tumbled back toward Earth, she said. The sources would not confirm what exactly the payload was, saying it was classified. The company has recently ramped up its launch pace, even launching two missions from opposite coasts within about 48 hours.

SpaceX competes for military launches with United Launch Alliance, a joint venture of Boeing and Lockheed Martin Corp., which was the sole provider for the Pentagon until Musk launched a campaign in Congress and the courts challenging what he called an unfair monopoly.

In 2015, SpaceX was certified by the U.S. Air Force to launch national security satellites.

If the test is successful, SpaceX can firm up a date for the first launch of the rocket it plans to use for commercial and military missions - and eventually for travel to the moon and Mars. The company later said it had cleared the issue.

"I don't think we can know", Ketcham said.

On its website, SpaceX says it has more than 70 upcoming missions on its launch manifest, which could take several years. In the static fire test, SpaceX engineers will ignite all 27 of the heavy-lift rocket's engines almost simultaneously for the first time, holding the rocket down on the launch pad while they do.

This article was originally published at 10:20 a.m.