Update for Dec. 7, 6 am ET: The United Launch Alliance's Atlas V rocket has successfully launched NASA's Laser Communications Relay Demonstration satellite and Space Force payloads on the STP-3 mission. Read our launch wrap story here.
A U.S. military mission will get off the ground Tuesday morning (Dec. 7) after a two-day delay, and you can watch the liftoff live.
A United Launch Alliance (ULA) Atlas V rocket is scheduled to launch the Space Test Program-3 (STP-3) mission at 4:04 a.m. EST (0904 GMT) Tuesday from Cape Canaveral Space Force Station in Florida. You can watch the launch live here at Space.com, courtesy of ULA, or directly via the company.
STP-3 was originally supposed to launch on Sunday (Dec. 5), but that plan was nixed after crews discovered a leak in the ground system that stores rocket propellant at Cape Canaveral. Fixing the leak and verifying that all is now well with the system resulted in a 48-hour delay, ULA representatives explained via Twitter over the weekend.
Related: The history of rockets
STP-3 will launch two satellites that carry a variety of technology-demonstrating payloads, most of them sponsored by the Department of Defense's Space Test Program. Many of the payloads are classified, but we know a bit about a few of them.
For example, the larger of the two satellites, called STPSat-6, carries a new NASA laser-communication system and a National Nuclear Security Administration payload designed to detect the detonation of nuclear bombs from space.
The STP-3 launch will kick off a very busy three-day stretch in spaceflight. A Russian Soyuz rocket is scheduled to launch billionaire Yusaku Maezawa and two other people toward the International Space Station early Wednesday morning (Dec. 8), for example, and a Rocket Lab Electron booster will send two commercial Earth-observation satellites to orbit that same evening.
Thursday (Dec. 9) will see the launch of NASA’s Imaging X-ray Polarimetry Explorer satellite atop a SpaceX Falcon 9 rocket as well as the liftoff of Blue Origin's NS-19 space tourism mission. NS-19 will send six people — including Good Morning America host and former NFL star Michael Strahan and Laura Shepard Churchley, the eldest daughter of first American in space Alan Shepard — on a brief trip to suborbital space.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook.