As SpaceX resumes Falcon launches after Starship’s exhilarating first orbital flight test last week, the company will conclude a series of three scheduled launches in less than 30 hours with the O3b mPOWER 3 & 4 mission on Friday. Liftoff of the Falcon 9 rocket from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Space Force Station is currently scheduled for an 88-minute launch window opening at 5:12 pm EDT (21:12 UTC).
Weather is currently predicted to have a 20% chance of being acceptable for launch on Friday, with the primary violation concerns being cumulous clouds, surface electric field rule, and lightning. Should the launch be delayed to a backup opportunity on Saturday, the weather improves only slightly to a 30% chance of acceptable conditions with concerns being cumulous clouds, surface electric fields rule, and anvil clouds.
O3b mPOWER is a Medium Earth Orbit (MEO) satellite constellation owned and operated by Luxembourg-based satellite telecommunications network provider, SES. The constellation provides high-throughput low-latency data and internet services to a variety of commercial and government customers.
The mPOWER satellites will form a second-generation constellation of O3b satellites, with O3b mPOWER 3 and 4 the second pair of satellites in this generation. The first pair was successfully launched aboard a Falcon 9 in December 2022.
The company’s original constellation consists of 20 satellites, all located in MEO, which were launched aboard five Soyuz-ST-B/Fregat-MT missions between June 2013 and April 2019. O3b was originally owned by the company O3b Networks before being acquired by SES in 2016.
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The satellites making up this second-generation constellation are built by Boeing and are based on the Boeing 702X satellite bus. This platform was announced in 2019 and is known as a software-defined satellite, and it gives greater flexibility and capabilities to the operator of the satellite.
Once launched, the satellites will spend around six months using their onboard electric propulsion system to slowly raise their orbits until they each reach the planned operational equatorial orbit of the constellation at an altitude of 8,000km (4,970 miles).
During this time, the satellites will also perform various checks to ensure all systems onboard are working as intended before being commissioned as part of the overall constellation.
The mPOWER 3 and 4 satellites that will be launched on Friday’s mission were delivered to Cape Canaveral on April 11 to begin their pre-launch processing, having already completed assembly and testing.
O3b mPOWER 3 & 4 before being encapsulated inside of Falcon 9’s payload fairing. (Credit: SpaceX)
Once unloaded from their transport container, the satellites were attached to Falcon 9’s payload adaptor. They were then encapsulated between the two halves of the rocket’s 5.2 m (17ft) diameter, 13.1m (43 ft) tall payload fairing.
The completed fairing section was then rotated horizontally and integrated with the rest of the Falcon 9 launch vehicle inside the Horizontal Integration Facility (HIF) at SLC-40 before the completed rocket was rolled out to the launch pad.
The booster being used on this mission is B1078-2. This booster is very new to the fleet, having recently conducted its maiden launch on March 2, where it launched Crew Dragon Endeavour on its fourth flight to the ISS as part of the Crew-6 mission.
While the satellites and their launch vehicle were being prepared for the mission, SpaceX’s recovery fleet also began to head downrange to support the mission.
On April 23, SpaceX’s Autonomous Spaceport Drone Ship (ASDS) Just Read The Instructions (JRTI) was towed out of Port Canaveral by tug Nicole Foss to begin heading 688km downrange to the landing zone for the booster. Two days later, SpaceX’s recovery vessel Bob also departed port to support the mission and possibly recover the two halves of the payload fairing, which will attempt a parachute-assisted splashdown in the Atlantic Ocean after separating from the rocket.
On launch day, as with other Falcon 9 missions, a go/no-go poll will be conducted at T-38 minutes to ensure everything remains “go” for propellant loading.
Now you see me…now you don't! More #O3bmPOWER satellites inside the fairing and getting ready for launch at the end of this week. @SES_Satellites pic.twitter.com/K9nDPsZd9b
— Steve Collar (@steviecSES) April 23, 2023
If no issues are reported, at T-35 minutes, liquid kerosene — or RP-1 — and liquid oxygen (LOX) will begin to flow into the first stage’s tanks. At the same time, RP-1 will also begin loading onto the second stage.
This will continue until around the T-20 minute mark, at which time RP-1 loading will be completed on the second stage and the transporter/erector (T/E) will purge its propellant lines. At T-16 minutes LOX loading on the second stage will begin.
As fueling of Falcon 9 continues, the vehicle will begin to chill down the nine Merlin 1D engines on its first stage at around T-7 minutes to ensure the engines are at the correct operating temperature before ignition.
At T-1 minute, the vehicle will enter startup and begin going through its various automated pre-launch checks, as well as pressurizing the propellant tanks to flight pressure ahead of liftoff. If all remains nominal the launch director will give a final “go” for launch around T-45 seconds.
First stage engine ignition will occur at T-3 seconds, with liftoff expected at T0. Shortly afterward, the rocket will begin a gravity turn. For this mission, the vehicle will slowly pitch over and begin to head due east from Cape Canaveral in order to achieve the equatorial orbit needed for the satellites.
Around two-and-a-half minutes after launch, the first stage will reach main engine cutoff (MECO) and shut down all nine of its engines. Shortly afterward, it will separate from the second stage and begin its usual landing sequence.
December’s Falcon 9 launch with the first pair of O3b mPOWER satellites (Credit: Stephen Marr for NSF)
After separating, the first stage will coast until around six-and-a-half minutes after liftoff before performing a 1-3-1 entry burn where one engine will ignite followed shortly after by two more — for a total of three — before dropping back down to a single engine. In total, this burn is expected to last about 20 seconds and helps to protect the booster as it passes back into the denser regions of Earth’s atmosphere.
About eight-and-a-half minutes after launch, as it approaches the drone ship, the first stage will begin its landing burn. This will help to guide it to a soft touchdown on the deck of Just Read The Instructions, which will then return it to Port Canaveral ready to be turned around for its next mission.
While the first stage is making its return to Earth, Falcon 9’s second stage will be continuing with the primary mission of delivering the O3b satellites to orbit. A few seconds after stage separation, its Merlin Vacuum (MVac) engine will ignite and start its first burn of the mission.
Fairing deployment will occur around three-and-a-half minutes after liftoff and will expose O3b mPOWER 3&4 to the vacuum of space for the first time. The two halves of the payload fairing will fall away from the rocket to begin their own descent back to Earth, where they will parachute into the ocean to be recovered.
The second stage will continue burning until just over eight minutes after launch, after which the MVac engine will shut down with the vehicle in a low parking orbit around Earth. After an approximately 20-minute coast, the MVac will restart, firing for about 40 seconds burn to raise the apogee — or the highest point in the vehicle’s orbit — to just under 7,000km (4,349 miles) above the Earth.
With the second burn complete, the second stage and satellites will coast until they reach apogee, at which point the MVac engine will ignite for one final time, making a 30-second burn to circularize the orbit. After one more brief coast phase, lasting just a few minutes, the satellite in the upper position will be deployed from the second stage. The satellite in the lower position will follow about seven minutes later.
Render of the O3b mPOWER constellation in orbit (Credit: SES)
Friday’s launch brings the strength of the O3b mPOWER constellation up to four of the planned 11 satellites. Although the constellation is not planned to be completed until 2024, SES expects to begin rolling out service in the latter half of 2023, using the satellites that will already be in service at this time.
Another pair of O3b mPOWER satellites are currently scheduled to fly aboard a Falcon 9 mission from SLC-40 in May, with SpaceX contracted to deploy all 11 spacecraft.
(Lead image: Falcon 9 at SLC-40 ahead of December’s O3b mPOWER 1/2 mission. Credit: Stephen Marr for NSF/L2)
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