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 (opens in new tab).
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 (opens in new tab) 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 (opens in new tab)" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) or on Facebook (opens in new tab).