SpaceX launches Falcon 9 on Transporter-5 Rideshare Mission

by Joseph Navin

At 18:27 UTC (2:27 p.m. EDT) on May 25, SpaceX has launched yet another Falcon 9 rocket. Lifting off from Space Launch Complex-40 (SLC-40) at Cape Canaveral Space Force Station, Falcon 9 is carrying several dozen payloads to a sun-synchronous orbit for the Transporter-5 rideshare mission. The flight featured a somewhat rare return to launch site (RTLS) landing, with the first stage touching down at Landing Zone-1 at Cape Canaveral.

Transporter-5 is the fifth dedicated rideshare mission for SpaceX. These rideshare missions are intended to compete with other smallsat launch companies in the aerospace industry such as Astra and Rocket Lab, which utilize small launch vehicles to give smallsat payloads a dedicated flight.

The Falcon 9 booster:

The Falcon 9 booster used on the Transporter-5 mission was booster 1061-8. It launched for the first time as part of the Crew-1 crew rotation flight in November 2020. It then flew on other missions including Crew-2, SXM-8, CRS-23, IXPE, Starlink Group 4-7, and most recently Transporter-4.

The eighth launch of booster 1061 marked the one-hundredth launch of a Falcon 9 Block 5 rocket. The Block 5 variant of the Falcon 9 had its maiden launch with booster 1046, which launched the Bangabandhu Satellite-1. Block 5 is set to be the last major variant of Falcon 9.

Booster 1061-8 is notable as it has supported the most NASA missions of any first stage, making up four flights of the booster.

It also was the first booster to support two missions for NASA’s Commercial Crew Program and, with this launch, will be the first to support two SpaceX Transporter missions back to back.

Launch:

Prior to launch day, the Falcon 9 atop the Transport Erector — or T/E — was rolled out from the Horizontal Integration Facility at SLC-40. It was moved to the pad and raised vertical.

The launch auto sequence started at T-35 minutes prior to launch, meaning that propellant loading operations on the Falcon 9 began with the loading of RP-1 on both stages of the rocket.

Also at the same time, the loading of Liquid Oxygen (LOX) began in the first stage. LOX loading on the second stage started later, at T-16 minutes.

A sign of an impending Falcon 9 launch — a long vent of excess oxygen from the T/E — occurred at the T-20 minute mark prior to launch. Simultaneously, the loading of RP-1 on the upper stage of the Falcon 9 was completed.

Falcon 9 rolls out to SLC-40 ahead of the first GPS-III mission. Credit: SpaceX/US Air Force

At T-4 minutes and 30 seconds prior to liftoff, the T/E retracted to the launch position. Next, the Falcon 9 entered startup a minute prior to liftoff, when the vehicle takes control of the rest of the countdown.

At T-3 seconds, the nine Merlin 1D engines on the first stage ignited. At T-0, the hold-down clamps on the reaction frame of the T/E released and the Falcon 9 lifted off from SLC-40. Soon after launch, the vehicle rolled to the proper launch azimuth and began to pitch downrange of the launch site.

While the vehicle is ascending, the Falcon 9 made a “dogleg maneuver” as it avoided overflying Florida. This launch used the polar launch corridor, which has been used by SpaceX since the SAOCOM 1B mission in 2020. The corridor had previously been unused between 1969 and 2020.

About two and a half minutes into the flight, the nine Merlin 1D engines on the first stage shut down in a milestone called main engine cutoff (MECO), and the second stage subsequently separated from the first stage. A few seconds later, the second engine start-1 (SES-1) occurred when the single Merlin Vacuum engine on the second stage ignited.

First stage booster 1061-8 then performed a flip using its onboard nitrogen gas thrusters. After this, the booster conducted a boostback burn by igniting three of its nine Merlin 1D engines. A second burn — the entry burn — occurred a few minutes later to slow the vehicle down as it began to reenter Earth’s atmosphere.

The southern trajectory of this launch took the Falcon 9 second stage close to the eastern coast of Florida. The vehicle came closest to the coastline near West Palm Beach.

At around this time, the two fairing halves on the second stage separated, exposing the plethora of payloads to the vacuum of space. The halves will later be recovered by one of SpaceX’s recovery ships after splashing down under a parachute in the Atlantic Ocean around 600 km downrange of Cape Canaveral.

Half of a payload fairing returns to Earth via parachute. Credit: Elon Musk

Prior to landing, the first stage booster used the center Merlin 1D engine to conduct a landing burn and subsequently landed at LZ-1. Upon landing, the booster becomes known as booster 1061-9.

LZ-1 was built on the former site of Launch Complex 13 at Cape Canaveral. The pad hosted test launches of the SM-65 Atlas intercontinental ballistic missile and other Atlas rockets between 1958 and 1978. The site was demolished to make way for the construction of LZ-1 and LZ-2.

Meanwhile, the second stage overflew the island of Cuba as it heads south on a near-polar launch trajectory.

After the powered flight is over, the payloads onboard the second stage began to separate. After the payload separation sequence is over, the second stage MVac engine will ignite one more time to deorbit the second stage, leading it to burn up over the South Pacific Ocean.

Payloads:

The Transporter-5 mission featured a multitude of rideshare payloads. This includes the Sherpa-AC orbital transfer vehicle from Spaceflight Inc, injected into a 525 km Sun Synchronous Orbit.

An infographic made by Spaceflight of the Sherpa-AC which will launch on the Transporter-5 mission. Credit: Spaceflight

The Sherpa-AC carries two hosted payloads from Xona Space and NearSpace Launch. Spaceflight also managed the deployment of three spacecraft for MIT Lincoln Laboratory and the Missile Defense Agency. This is the first flight of the Sherpa-AC, which is a new variant of Spaceflight’s Sherpa spacecraft that has attitude control but not propulsion.

The flight also carried the Italian space tug ION SCV-006 built by D-Orbit which will carry additional CubeSats. Another tug is the Momentus VR-3 which carried multiple CubeSats and PocketQubes.

Also onboard was NASA Ames’ Pathfinder Technology Demonstrator-3 spacecraft, which will feature the TeraByte InfraRed Delivery (TBIRD) system. This payload will demonstrate new methods in laser communication to achieve a record-breaking 200-gigabit per second data transfer rate.

Most spacecraft use radio waves to communicate, however laser (or optical) communication is a maturing technology that is planned to be used on future crewed and uncrewed missions, including the upcoming Lunar Gateway.

(Lead image: Falcon 9 launching today from SLC-40 via Julia Bergeron)

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