This was the 84th flight for an Atlas rocket since 2002.
The X-37B is the newest and most advanced re-entry spacecraft.
"It's a classified mission, and what is classified about it as the details of the vehicle itself, the mission it will do on orbit and where it will do that", he said. There has not been much information provided by the U.S. government or by the authorities in the past.More news: CarryMinati's 'YouTube vs TikTok
"This X-37B mission will host more experiments than any prior missions", said Barrett, who is also the chief of the recently created U.S. Space Force.
The U.S. Space Force will conduct the secret mission, although the vehicle will remain an asset of the U.S. Air Force.
Raymond called the module "a trailer ... behind the truck that provides added capacity for experiments", but didn't want to elaborate on the size of the module or how the X-37 was modified to incorporate that upgrade.
The newly launched has an additional compartment for experiments, including several for NASA and the US Naval Research Laboratory. It's deploying a small satellite (FalconSat-8), two NASA projects studying the effects of radiation on seeds and other materials and an experiment that uses microwave energy to beam power.More news: Mysterious Children’s Disease Linked to COVID-19 and Kawasaki Disease
One question that has loomed over the X-37 is whether it has counterspace capabilities and could be used to test offensive technologies.
"Congratulations on the 6th mission of the X-37B reusable spacecraft", Defence Secretary Mark Esper tweeted shortly after the launch. Japan and China also aim to pursue the capability.
That's the sixth mission of this device in the space.
Taking to micro-bloging site Twitter, the ULA said, "An updated briefing from Launch Weather Officer Jessica Williams says that current conditions are violating launch commit criteria rules for cumulus clouds and the electrical potential in the air".More news: Afghanistan defends fresh offensive against Taliban after 2 terror attacks