Elon Musk, the founder and CEO of SpaceX, said his rocket company’s toughest mission yet has arrived — and you can watch it live online.
Sometime between 11:30 p.m. ET on June 24, 2019, and 2:30 a.m. ET on June 25, 2019, a Falcon Heavy rocket will try to lift off from Cape Canaveral, Florida.
Tonight’s launch attempt marks SpaceX’s third-ever with Falcon Heavy. The rocket design debuted in February 2018, has three reusable boosters, and is considered the planet’s most powerful launch system in use today.
“This will be our most difficult launch ever,” Musk tweeted on June 19, 2019.
What makes this mission, called Space Test Program-2 (STP-2), so challenging is what’s stacked inside the rocket’s nose cone: 24 government and commercial satellites that together weigh about 8,150 pounds (3,700 kilograms). When fully fueled, a Falcon Heavy rocket weighs about 1,566 tons (1,420 metric tons), or more than 300 adult elephants’ worth of mass.
An 8,150-pound (3,700-kilogram) stack of 24 government and commercial satellites inside the nose cone of SpaceX’s Falcon Heavy rocket in June 2019.
After getting its behemoth rocket off the pad at Launch Complex 39-A, SpaceX has to deploy the two dozen spacecraft into multiple orbits around Earth over several hours. To do this, it must shut down and reignite the engine of an upper-stage rocket four times, according to the company.
One satellite holds NASA’s Deep Space Atomic Clock, which may change the way robots and astronauts navigate space. Another spacecraft is the Planetary Society’s LightSail, an experiment that could change how vehicles propel themselves to a destination. The National Oceanic and Atmospheric Administration is also launching six small weather satellites built in partnership with Taiwan.
There’s even a spacecraft holding the ashes of 152 people, and it will orbit Earth for about 25 years before careening back as an artificial meteor.
But SpaceX will also be attempting to land all three of the rocket’s 16-story boosters back on Earth for reuse in future launches. The two attached to the side of the Falcon Heavy rocket are set to touch down on land a few minutes after liftoff.
Meanwhile, the central or core booster — which will fire longer and disconnect from the upper-stage rocket later in the flight — will try to land on a drone ship sitting about 770 miles (1,240 kilometers) off the coast of Florida in the Atlantic Ocean.
Watch SpaceX’s launch attempt live on Monday night
There’s a 20% chance that SpaceX will delay its launch because of thunderstorms, according to a forecast issued by the US Air Force on Monday morning. If the launch is pushed to its backup window 24 hours later, there’s a 30% chance of delay.
If you want to follow the launch and deployment events, we’ve included a detailed timeline below the YouTube embed.STP-2 Mission
Launch events and timing relative to the moment Falcon Heavy lifts off the pad are outlined below and come from SpaceX’s press kit for the STP-2 mission.
-53:00— SpaceX launch director verifies go for propellant load
-50:00— First-stage RP-1 (rocket grade kerosene) loading begins
-45:00— First-stage LOX (liquid oxygen) loading begins
-35:00— Second-stage RP-1 (rocket grade kerosene) loading begins
-18:30— Second-stage LOX loading begins
-07:00— Falcon Heavy begins prelaunch engine chill
-01:30— Flight computer commanded to begin final prelaunch checks
-01:00— Propellant tanks pressurize for flight
-00:45— SpaceX launch director verifies go for launch
-00:02— Engine controller commands engine-ignition sequence to start
-00:00— Falcon Heavy liftoff
Once the rocket lifts off, Falcon Heavy hardware and its payload will go through a series of crucial maneuvers. The side boosters and core booster will try to separate and land. Following that, the rocket’s upper or second stage will propel into orbit, then attempt to deploy its 24 satellites from a device called the Integrated Payload Stack over several hours.
The timing and events below are also relative to liftoff, in hours, minutes, and seconds.
00:00:42— Max Q (moment of peak mechanical stress on the rocket)
00:02:27— Booster engine cutoff (BECO)
00:02:31— Side boosters separate from center core
00:02:49— Side boosters begin boost-back burn
00:03:27— Center core engine shutdown/main engine cutoff (MECO)
00:03:31— Center core and 2nd stage separate
00:03:38— 2nd stage engine starts (SES-1)
00:04:03— Fairing deployment
00:07:13— Side boosters begin entry burn
00:08:41— Side booster landings
00:08:38— 2nd stage engine cutoff (SECO-1)
00:08:53— Center core begins entry burn
00:11:21— Center core landing
00:12:55— Spacecraft deployments begin
01:12:39— Second-stage engine restart (SES-2)
01:13:00— Second-stage engine cutoff (SECO-2)
02:07:35— Second-stage engine restart (SES-3)
02:08:04— Second-stage engine cutoff (SECO-3)
03:27:27— Second-stage engine restart (SES-4)
03:28:03— Second-stage engine cutoff (SECO-4)
03:34:09— Final spacecraft deployment
This article originally appeared on Business Insider. Follow @BusinessInsider on Twitter.