Live Countdown Coverage Begins for SpaceX’s CRS-21 Mission

SpaceX's CRS-21 mission.
A SpaceX Falcon 9 rocket, with the upgraded cargo Dragon spacecraft atop, stands ready for liftoff at NASA Kennedy Space Center’s Launch Complex 39A in Florida on Dec. 5, 2020, ahead of the company’s 21st Commercial Resupply Services (CRS-21) launch. Liftoff of the Falcon 9 is scheduled for 11:17 a.m. EST on Sunday, Dec. 6. Photo credit: SpaceX

Hello, and good morning from NASA’s Kennedy Space Center in Florida! Live countdown coverage for the launch of SpaceX’s 21st resupply services (CRS-21) mission to the International Space Station has begun – watch now on NASA TV or the agency’s website.

SpaceX's Cargo Dragon spacecraft and Falcon 9 rocket stand ready for liftoff for CRS-21.
The upgraded SpaceX Cargo Dragon spacecraft and Falcon 9 rocket stand ready for liftoff at NASA Kennedy Space Center’s Launch Complex 39A in Florida after being raised to a vertical position on Dec. 2, 2020, ahead of the company’s 21st Commercial Resupply Services (CRS-21) launch. Liftoff of the Falcon 9 is scheduled for 11:17 a.m. on Sunday, Dec. 6. Photo credit: SpaceX

The uncrewed cargo Dragon spacecraft and Falcon 9 rocket are scheduled to lift off from Kennedy’s Launch Complex 39A in just about 30 minutes, at 11:17 a.m. EST. The mission will deliver more than 6,400 pounds of supplies, equipment, and critical materials to support dozens of science and research experiments that will take place during Expeditions 64 and 65.

About 12 minutes after today’s launch, Dragon will separate from the Falcon 9 rocket’s second stage, beginning a series of carefully choreographed thruster firings to reach the orbiting laboratory. Here’s a full look at today’s countdown and ascent milestones. All times are approximate:

COUNTDOWN
Hour/Min/Sec – Events
-00:38:00 – SpaceX Launch Director verifies go for propellant load
-00:35:00 – RP-1 (rocket-grade kerosene) loading begins
-00:35:00 – 1st stage LOX (liquid oxygen) loading begins
-00:16:00 – 2nd stage LOX loading begins
-00:07:00 – Falcon 9 begins pre-launch engine chill
-00:05:00 – Dragon transitions to internal power
-00:01:00 – Command flight computer to begin final prelaunch checks
-00:01:00 – Propellant tanks pressurize for flight
-00:00:45 – SpaceX Launch Director verifies go for launch
-00:00:03 – Engine controller commands engine ignition sequence to start
-00:00:00 – Falcon 9 liftoff

LAUNCH, LANDING AND DRAGON DEPLOYMENT
Hour/Min/Sec – Event
00:01:18 – Max Q (moment of peak mechanical stress on the rocket)
00:02:30 – 1st stage main engine cutoff (MECO)
00:02:34 – 1st and 2nd stages separate
00:02:41 – 2nd stage engine starts
00:06:37 – 1st stage entry burn begins
00:08:38 – 2nd stage engine cutoff (SECO)
00:08:38 – 1st stage landing
00:11:49 – Dragon separates from 2nd stage
00:12:35 – Dragon nosecone open sequence begins

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