SpaceX is ready to launch two Starlink missions from both coasts within the week. The first launch, Starlink Group 2-10 will launch aboard a Falcon 9 from Space Launch Complex 4E (SLC-4E) located on the Vandenberg Space Force Base (VSFB) in California with a T0 of 11:02 PM PDT Tuesday, May 30 (06:02 UTC May 31).
The next launch, Starlink Group 6-4 is currently scheduled to launch from Space Launch Complex 40 (SLC-40) on the Cape Canaveral Space Force Station Thursday, June 1 at 7:04 AM EDT (11:04 UTC), but this is expected to be delayed by a few days.
Both missions will continue to grow SpaceX’s internet satellite network in low-Earth orbit. Earlier this month, SpaceX surpassed 4,000 of these satellites in orbit, with that number growing continually.
There will be two different variants of satellites launching.
The first mission, Group 2-10, will be using a slightly older variant of satellites known as v1.5. It is still using some of the features in the upgraded v2 satellites, including laser-link communications between satellites. They do, however, use a hall effect thruster powered by krypton and each satellite only masses approximately 300 kilograms. For comparison, the new v2 Mini satellites have a mass of over 800 kilograms.
The 6-4 mission will be launching the aforementioned “v2 Mini” satellites because the expected full-sized upgraded satellites were meant to fly on Starship. With only one test flight of Starship currently under its belt, SpaceX worked with the Federal Communications Commission to allow smaller versions to be launched inside the fairing of the Falcon 9. With these still being quite large, fewer v2 mini satellites are launched at once.
The v2 Mini variants still contain most of the upgrades that will fly on the standard v2 satellites. These include providing four times more capacity than the earlier v1.5 satellites as well as using argon for the hall effect thrusters aboard each satellite. SpaceX adds that each new v2 Mini launch will introduce more capacity into the overall system.
The first launch, Group 2-10, carrying 52 v1.5 satellites, will fly aboard booster B1061-14, which previously flew on Crew-1, Crew-2, SXM-8, CRS-23, IXPE, Transporter-4, Globalstar FM15, Eros-C3, and four Starlink missions. This mission will launch on a southern trajectory, including a slight curve to go around populated areas such as Los Angeles.
As with other group two launches from VSFB, the satellites will deploy at an initial 222 by 333 kilometers orbit inclined 70 degrees, eventually using its thrusters to end in a 530-kilometer circular orbit also inclined 70 degrees.
Meanwhile, the first stage is expected to land back on the drone ship Of Course I Still Love You shortly after its launch. The drone ship is positioned along the western side of the Baja Peninsula.
The second launch just one day later will be the Group 6-4 mission from Florida. The 22 Starlink v2 Mini satellites are scheduled to launch aboard B1078, which has flown two previous flights including Crew-6 in March sending astronauts to the International Space Station and O3b mPOWER 3 & 4 which launched in late April.
This mission will be launching in a southeastern direction, with an expected circular orbit of 530 kilometers inclined 43 degrees. The expected initial parking orbit is 365 by 373 kilometers inclined 43 degrees as we’ve seen during previous v2 Mini launches from SLC-40 and these satellites will use their argon hall effect thrusters to enter their final orbit.
This booster is expected to land on the drone ship A Shortfall of Gravitas, which is located approximately 640 kilometers downrange.
The countdown procedure for both launches is very similar. 35 minutes before liftoff, equipment at the launch pad begins to load the Falcon 9 with RP-1 fuel, a type of refined kerosene. At the same time, liquid oxygen (LOX), the oxidizer for the Falcon fleet of rockets, begins loading into the first stage.
Sixteen minutes until liftoff, LOX load gets underway on the second stage. Seven minutes before launch, the engines are chilled to prime them ahead of the supercooled cryogenics that flows through them at liftoff. This prevents a potentially dangerous shock at ignition.
There’s a slight difference at this point. The transporter erector (T/E) used at SLC-4E is an older variant. As a result, it retracts 13 degrees away from the rocket minutes before liftoff and remains there through the launch. However, at SLC-40 the T/E is retracted a few degrees prior to launch before it “throws back” as Falcon 9 lifts off.
At T-1 minute, Falcon 9 goes into “startup,” meaning the onboard computers have full control of the countdown as the propellant tanks are pressurized for flight. At T-3 seconds, the command is given to ignite the nine Merlin 1-D engines at the base of the first stage followed by liftoff at T0.
About two and a half minutes into flight, major events will happen in quick succession for both flights. The first stage engines will shut down and then separate from the second stage. That’s followed by the ignition of the single Merlin Vacuum engine which will burn until it places the satellites in their initial parking orbit.
Meanwhile, the boosters will execute a set of multiple burns, landing them on their respective drone ships just minutes after launching.
These launches will mark the 36th and 37th orbital launch attempts by SpaceX so far this year, including Falcon 9 and Falcon Heavy.
(Lead image: A SpaceX Falcon 9 rocket waits to launch the Tranche 0 mission. Credit: Jack Beyer for NSF)