SpaceX inserts Starlink into higher orbit on Group 4-8 mission

by Trevor Sesnic

SpaceX has launched 46 Starlink internet satellites to low Earth orbit on the Starlink Group 4-8 mission. Launching from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Space Force Station, Falcon 9 took to the skies at 9:44 AM EST (14:44 UTC) on Monday, February 21.

This mission marked SpaceX’s seventh launch of 2022, averaging a launch every 7.2 days so far.

The 46 Starlink satellites will be placed into an initial 53.22º, 337 km x 325 km low Earth orbit. In a process that takes months, the satellites will slowly raise their orbit to a 53.2º, 540 km circular orbit using their onboard krypton-propelled ion engines.

Thanks to flying on the descending Starlink node – flying southeast out of the Cape, as opposed to the usual northeast – SpaceX’s drone ship A Shortfall of Gravitas (ASOG), tugged by Zion M. Falgout, is positioned in calmer seas 636 km downrange. Due to the calmer seas near the Bahamas – compared to the rough seas off the Eastern coast – the 45th Space Wing has cited that the booster recovery risk is moderate.

In hopeful prevention of a repeat of Starlink Group 4-7, where SpaceX lost at least 37 out of 49 satellites launched to a geomagnetic solar storm, Space Launch Delta 45 has deemed that solar activity risk is low. On top of this, SpaceX is inserting the Starlink satellites into a significantly higher initial orbit to reduce drag. The perigee was increased from 210 km on Starlink Group 4-7 to 325 km on this mission.

The booster supporting this mission, B1058-11, was the second booster to fly for the 11th time. B1058 reached this flight mark significantly faster than B1051; B1051 flew its 11th flight 1,022 days after its initial flight compared to B1058, which will reach this feat just 632 days after its first launch.

B1058’s missions Launch Date (UTC) Turnaround Time (Days)
SpaceX Demo-2 May 30, 2020 19:22 N/A
ANASIS-II July 20, 2020 21:30 51.09
Starlink v1.0 L12 October 6, 2020 11:29 77.58
CRS-21 December 6, 2020 16:17 61.20
Transporter-1 January 24, 2021 15:00 48.95
Starlink v1.0 L20 March 11, 2021 08:13 45.72
Starlink v1.0 L23 April 7, 2021 16:34 27.35
Starlink v1.0 L26 May 15, 2021 22:56 38.27
Starlink Group 4-1 November 13, 2021 12:19 181.56
Transporter-3 January 13, 2022 15:25 61.13
Starlink Group 4-8 February 21, 2022 14:44 38.97

Both fairing halves on this mission have supported three previous missions. About 45 minutes after launch, these fairing halves will be recovered from the water by SpaceX’s ship Doug 640 km downrange.

Starlink Progress:

As the name implies, this mission targeted the fourth shell of Starlink phase one. The shell that a certain Starlink launch is targeting can be found inside of the mission name: the first number – in this case “4” for Starlink Group 4-8 – is the shell that the satellites will be inserted into.

Inclination (°) Orbital Altitude (km) Planes Satellites per Plane Number of Satellites Currently Working Satellites
Shell 1 53.0 550 72 22 1,584 1,538
Shell 2 70.0 570 36 20 720 51
Shell 3 97.6 560 6 58 348 3
Shell 4 53.2 540 72 22 1,584 260
Shell 5 97.6 560 4 43 172 0

Starlink orbital shell data. (Currently Working Satellites. Credit: Jonathan McDowell)

SpaceX is hoping to launch on the order of 40 Starlink missions in 2022, which would complete the fourth shell. It is expected that upon the fourth shell’s completion, SpaceX will start filling the second shell.

Render of Starlink satellites in orbit (Credit: SpaceX)

Falcon 9 launch:

Ahead of launch, the rocket rolled out of the Horizontal Integration Facility (HIF) at SLC-40 where it was then made vertical thanks to the transporter erector (T/E), also known as the strongback. The T/E is used to load propellants into the second stage of the vehicle, provide structural support while vertical (hence the name strongback), provide power and air conditioning to the payload, and take the Falcon 9 from its horizontal position to its vertical position.

B1058 did not perform a static fire prior to this mission, which is not uncommon to see for flight-proven boosters.

At T-38 minutes, the launch director will verify that the vehicle is GO for propellant loading. Pending all teams being GO, 3 minutes later, at T-35 minutes, SpaceX will begin loading subcooled RP-1 onto both the first stage and the second stage. At the same time, chilled liquid oxygen (LOX) begins loading onto the first stage. The Falcon 9 uses RP-1 that is cooled to -7° C and LOX that is cooled to -205° C.

By further chilling – and therefore increasing the density of – propellants, SpaceX is able to get more performance out of the Falcon 9 — something that is crucial for reuse. This also comes with the trade-off that SpaceX is unable to hold the countdown once fuel loading has started.

At T-1 minute, Falcon 9 will enter startup and begin pressing its tanks for flight. At this time, the Falcon 9 is in charge of the launch countdown — all technical aborts from this point forward will be handled by the vehicle itself, and not the ground operators. However, even during this period, the ground operators are still able to scrub the launch in case of either a range or weather violation.

Liftoff of Falcon 9 on the NROL-87 mission (Credit: SpaceX)

At T-3 seconds, the booster’s flight computer will command the ignition of the first stage’s nine Merlin 1D engines. The engines on the first stage ignite in pairs to reduce startup transients and loads on the vehicle. 

Once the vehicle has ensured that all systems are nominal, the hydraulic clamps at the base of the vehicle will release, letting the rocket lift off from the pad.

Launch Ascent Profile:

00:01:12 Max Q (moment of peak mechanical stress on the rocket)
00:02:32 1st stage main engine cutoff (MECO)
00:02:35 1st and 2nd stages separate
00:02:43 2nd stage engine starts
00:02:49 Fairing deployment
00:06:49 1st stage entry burn start
00:07:10 1st stage entry burn complete
00:08:25 1st stage landing burn start
00:08:47 2nd stage engine cutoff (SECO-1)
00:08:49 1st stage landing
00:56:38 2nd stage engine starts
00:56:39 2nd stage engine cutoff (SECO-2)
01:02:55 Starlink satellites deploy

This launch will require two burns of the second stage to reach the final orbit.

Rendering of Starlink satellites deploying from the second stage. (Credit: Mack Crawford for NSF)

Once the satellites have deployed from the second stage, the second stage will perform a third burn to deorbit itself. After a period of checkouts, the satellites will then propel themselves to their operational orbit.

SpaceX is expected to have two more Starlink launches in February. Starlink Group 4-9 will launch late February from LC-39A and Starlink Group 4-11 will launch late February from SLC-4E, at the Vandenburg Space Force Base.

(Lead Image: Falcon 9 launches the a Starlink Group 4-8 mission. Credit: Stephen Marr for NSF)

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