SpaceX’s 20th mission of the year is set to launch this Friday, March 24, sending another batch of Starlink satellites into low Earth orbit (LEO). The mission, named Starlink Group 5-5, is scheduled for liftoff at 11:43 AM EDT (15:43 UTC) from Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station, in Florida.
The weather forecast released by the Space Launch Delta 45’s Weather Squadron calls for a greater than 95% chance of favorable weather during the primary launch window. 24 hours later, during the backup launch window, the weather forecast is slightly worse with the chances of favorable weather dropping to 85%.
Coming right on the heels of the debut flight of Starlink v2 Mini satellites, this mission will also be launching into Starlink’s second-generation constellation (Starlink Gen 2). However, the satellites on this mission are the older version 1.5 satellites that have also been launched on the four previous Group 5 missions.
As part of the launch preparations, SpaceX conducted a static fire test of the rocket on Thursday, March 23–a rarity these days. These pre-launch static fire tests are becoming less common as Falcon flies more and gains experience and reliability. The booster for this mission, B1067, is flying for a tenth time on Friday, marking the seventh booster to fly up to ten times.
The reason for a static fire before launch is not known, but SpaceX officials have claimed in the past these tests are usually performed only when refurbishment of the booster has shown the need for the extra data before launch. This may come as a result of engine swaps or fixes that need to be corroborated.
The countdown sequence for this mission will follow the usual 35-minute-long propellant load sequence. This will begin with RP-1 (a refined form of kerosene) being loaded onto both stages and liquid oxygen (LOX) being loaded onto the first stage.
Loading of RP-1 on the second stage will wrap up 15 minutes later and chill down of the LOX umbilicals for the second stage will begin, creating the now-famous “T-20 minute vent.” This vent should last approximately four minutes, after which liquid oxygen load on the second stage will begin.
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Nine minutes later, the chill down on the nine first stage Merlin 1D (M1D) engines will begin. In this process, a small amount of liquid oxygen is let to flow through the oxygen turbopump to lower its temperature ahead of engine ignition. This avoids the formation of bubbles of gaseous oxygen during engine startup and initial operation when the highest flow of liquid oxygen is present in the oxygen turbopump. About a minute later, RP-1 load will be completed on the booster.
At T-3 minutes and T-2 minutes, LOX load will wrap up on the first and second stages respectively. From that point, the ground systems will initiate the purge of all the propellant lines ahead of liftoff.
One minute before liftoff, the ground computers will hand off command to Falcon 9’s onboard computers. These will begin a number of system checks on the vehicle and will initiate the pressurization of the tanks for flight.
Three seconds before liftoff, the engine controller will initiate the engine start sequence on all nine M1D engines on the first stage. These will ignite in a staggered manner, taking about two seconds to reach full power. During the last second of the count, vehicle computers perform health checks on all engines before commanding the ground clamps to release the rocket for liftoff.
Friday’s launch will follow a southeasterly trajectory with Falcon 9 grazing the northern parts of the Bahamas as it goes into orbit. The first stage nine engines are set to burn for approximately two minutes and 27 seconds. Four seconds later, the two stages will separate via four pneumatic pushers on the interstage, three on the perimeter and another one in the center.
Six seconds after that, the Merlin 1D Vacuum (MVacD) engine on the second stage will ignite and initiate the approximate six-minute long burn to put itself and the satellites into an elliptical parking orbit.
While the second stage powers itself to orbit, the first stage will return itself down to a powered landing on SpaceX’s autonomous spaceport drone ship A Shortfall Of Gravitas, which will be stationed 660 kilometers downrange.
LHA map for #Starlink Group 5-5 from CCSFS SLC-40 NET 24 Mar 15:33 UTC, alternatively 25 to 30 Mar based on issued NOTAM/NOTMARs. B1067.10 planned landing with estimated fairing recovery ~660km downrange. S2 debris reentry area south of Cape Town. https://t.co/BpJZ15cY0J pic.twitter.com/fO231VKdtb
— Raul (@Raul74Cz) March 23, 2023
Eight seconds after MVacD ignition, the fairing halves will separate and perform a parachute-assisted splashdown in the Atlantic Ocean. SpaceX’s multi-purpose recovery vessel Doug will be waiting downrange for the retrieval of both halves.
Once in the initial elliptical parking orbit, the second stage will coast for about 45 minutes to arrive at its apogee. Then, it’ll briefly relight its engine for orbit circularization.
Ten minutes after MVacD’s second burn of the mission, the Starlink satellites will separate and SpaceX teams will begin checkouts and on-orbit testing processes. The satellites will later raise their orbits to their operational altitude, which for this shell is a circular 530 km orbit.
After satellite separation, the second stage will perform a third and final burn for deorbit and disposal over the western Indian Ocean.
Friday’s launch will carry 56 Starlink v1.5 satellites into Starlink Gen 2’s 43-degree inclination shell. This will bring the total of Starlink satellites launched into orbit to 4,161, of which 302 no longer remain in orbit.
Starlink Gen 1
Starlink Gen 2
Missions
v1.0
Group 2
Group 3
Group 4
Group 5
Group 6
Orbit
550 km at 53º
570 km at 70º
560 km at 97.6º
540 km at 53.2º
530 km at 43º
Satellites launched
1,665
305
197
1,637
274
21
Satellites reentered
162
2
10
65
1
0
Satellites in operational orbit
1,436
57
184
1,514
74
0
(Status of Starlink constellation from Jonathan McDowell as of March 23)
This Starlink Gen 2 mission comes a few weeks after the debut of Starlink v2 Mini: a downsized version of the Starlink v2 satellite bus sized for Falcon 9’s fairing envelope. Orbital tracking data has shown that the first batch of v2 Mini satellites has had issues during their checkout phase and they’ve experienced orbital decay as a result of this.
In response to these observations, SpaceX’s CEO Elon Musk confirmed on Wednesday that these satellites are experiencing issues and some of them will be deorbited as a consequence. Sources indicate these issues are not affecting all satellites in the same manner and are of varying natures. Some of these issues are related to power or communications dropouts, and some may be experiencing sporadic attitude control issues as well.
Lot of new technology in Starlink V2, so we’re experiencing some issues, as expected.
Some sats will be deorbited, others will be tested thoroughly before raising altitude above Space Station.
— Elon Musk (@elonmusk) March 22, 2023
These issues are currently being identified and fixes are underway for future satellites. As a consequence, an upcoming launch of Starlink v2 Mini satellites, Starlink Group 6-2, has been delayed from March 29 into April.
To occupy the leftover gap in the schedule, the company has brought forward the Starlink Group 5-10 mission, which is now scheduled to launch on that date. That launch, just like Friday’s mission and prior Group 5 missions, will send Starlink v1.5 satellites into orbit instead of Starlink v2 Mini satellites.
(Lead image: B1067 on SLC-4E ahead of the O3b mPOWER mission. Credit: Stephen Marr for NSF)
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