Launch Roundup: SpaceX lands its 300th booster, NASA tests a solar sail, and China launches three more taikonauts

by Martin Smith
Render of the ACS3 Solar Sail in orbit (Credit: NASA)

During the last full week of April, planned launches include two Starlink missions and another Falcon 9 flight lifting customer satellites. The first Starlink mission of the week saw another milestone reached with the 300th landing of a Falcon 9 booster on the Group 6-53 mission. The delayed WorldView Legion 1 & 2 mission, which was originally due to fly last week and was rescheduled into this week’s plans, has since slipped out of the current schedule.

The fifth Electron to launch this year carried two demonstration missions into two notably different orbits on Wednesday. One of the two demonstrations being hoisted by Rocket Lab was a demonstration of a novel solar sail developed by NASA and powered by the pressure of sunlight acting upon the surface of the sail.

The week also delivered a crewed launch on Thursday when the Shenzhou 18 mission sent three more taikonauts to the Tianhe core module of China’s Tiangong space station.

The number 13 resonates this week, with Shenzhou 18 being the 13th crewed mission of the Chinese space program, and Falcon 9 potentially able to repeat its current record of 13 flights in a month. B1060 made its 20th and final flight on the Galileo mission on Saturday, April 27, and was the first booster to be recovered 13 times back in June 2022. This was the first time a Falcon 9 single first stage had been expended since November 2022.

The SpaceX schedule has changed as the week progressed and the Starlink Group 6-54 mission became the last for the company this week, the 13th flight of booster B1076 and the 81st orbital launch of the year. This is 17 more than the count on the equivalent date last year, and largely due to SpaceX’s remarkable Falcon 9 launch cadence.

Coincidentally 13 years ago this week Shuttle Endeavour was also ready on the pad for its final mission (STS-134), and the penultimate one for the Shuttle program. A malfunction on one of the auxiliary power units caused the launch to be scrubbed and delayed into May, however.

This time last year there had also been the same number of Starship launches for the year so far — it’s been over a year now since Starship’s maiden flight back on April 20, 2023, on the IFT-1 mission. It is also ten years this week since the company achieved the first successful propulsive ocean touchdown of a liquid rocket engine orbital booster on the CRS-3 mission and the first Falcon 9 which flew with landing legs.

Booster B1076-12 landed on droneship Just Read the Instructions, during Eutelsat 36D mission in March 2024 (Credit - SpaceX)

Booster B1076-12 landed on droneship Just Read the Instructions, during the Eutelsat 36D mission in March 2024. (Credit: SpaceX)

Falcon 9 Block 5 | Starlink Group 6-53

The first Starlink mission of the week launched from SLC-40 at the Cape Canaveral Space Force Station on Monday, April 22 at 6:17 PM EDT (22:17 UTC). The payload was another batch of 23 Starlink v2 Mini satellites massing around 16,800 kilograms and heading into an initial 285 by 293-kilometer orbit, inclined by 43 degrees.

The booster for this mission was B1078 on its ninth flight, which landed on the autonomous droneship Just Read the Instructions around 604 kilometers further downrange, while support ship Bob recovered the fairings. Significantly this was the 300th landing of a Falcon 9 booster, and the 226th since the last unsuccessful one.

These Group 6 missions continue, at least for the time being, to launch in numerical order except the missing Group 6-50 mission which remains unscheduled at present. This will be the 158th launch dedicated to Starlink overall and the 84th for the Gen2 series.

SpaceX has successfully launched 24 Starlink satellites in a single batch in the past and has declared a desire to extend this number further to 28 in a single batch by the end of the year. Starlink launches from the east coast are expected to focus on this pad soon while LC-39A is prepared for the GOES-U launch on Falcon Heavy in June.

As the week begins and before this flight, SpaceX has launched a total of 6,258 Starlink satellites, of which 406 have re-entered and 5,206 have moved into their operational orbit.

Electron / Curie | Beginning of the Swarm

Rocket Lab launched the fifth Electon of the year and its 47th mission overall on Wednesday, April 24 for the Beginning of the Swarm mission. Lift-off took place at the start of an 85-minute window at 09:32 NZST (21:32 UTC on the 23rd) from pad LC-1B in the Mahia Peninsula of New Zealand.

Two different payloads were sharing a ride for this mission. Firstly, NeonSat-1 is a demonstration mission ahead of the planned constellation of high-resolution optical satellites which would begin to launch from 2026 onward. The satellite was developed by the Korea Advanced Institute of Science and Technology and its Satellite Technology Research Center which launched Korea’s first satellite (KITSAT-1) 32 years ago.

This Earth observation satellite will monitor natural disasters along the Korean peninsula, applying artificial intelligence to its high-resolution imagery. It was deployed 50 minutes into the mission into a circular orbit at 520 kilometers in altitude. Electron’s Kick Stage then lit its Curie engine to raise its altitude to 1,000 kilometers, with a second burn to then circularize the orbit where a second payload was scheduled to be deployed one hour and 45 minutes into the mission.

Render of NASA's ACS3 Solar Sail in orbit (Credit - NASA)

Render of NASA’s ACS3 Solar Sail in orbit. (Credit: NASA)

This is another technology demonstration, developed by NASA’s Ames and Langley Research Centers. This Advanced Composite Solar Sail System (or ACS3) technology demonstration will deploy a solar sail from a cubesat using lightweight booms made from composite materials. As the name implies, this sail will leverage light from the sun and will be propelled by the pressure of sunlight acting upon it.

The spacecraft will spend a couple of months in an initial flight and checkout phase before deployment of the booms and reflective sail. The craft needs to be at a sufficient altitude for the tiny force of sunlight that will be applied to the sail to overcome atmospheric drag. At this altitude, this force is said to be roughly equivalent to the weight of a paperclip resting on your palm. The craft will then perform a series of pointing maneuvers to demonstrate orbit raising and lowering which will span weeks, so it could be July or later before any results are known.

It is intended that the data from this mission informs the creation of larger solar sails that could efficiently propel satellites for several usages such as communications relays on future crewed exploration missions, early warning satellites, or reconnaissance missions such as to near-Earth asteroids. Reducing mass could help to eliminate heavy propulsion systems and make longer-duration missions more efficient in both energy and cost.

Electron is prepared at LC-1 in Mahia Peninsula (Credit: Rocket Lab)

Electron is prepared at LC-1 in Mahia Peninsula. (Credit: Rocket Lab)

The kick stage will fire its engine retrograde one final time to lower its orbit, enabling atmospheric drag to eventually complete the task of deorbiting it, where it will burn up on re-entry. This mission required the addition of extra propellant tanks, extra batteries, and larger gas bottles for the reaction control system on the kick stage.

Rocket Lab is moving closer toward the reuse of a recovered Electron first stage. The company announced in early April that the carbon composite first-stage Electron recovered from the Four of a Kind mission in January has entered the production line for final acceptance testing and qualification ahead of a reflight.

Chang Zheng 2F/G | Shenzhou 18

China sent three more taikonauts from the People’s Liberation Army Astronaut Corps to the Tianhe core module of China’s Tiangong space station on Thursday, April 25. Lift-off took place near the start of a 40-minute launch window at 12:59 UTC from Site 901 (SLS-1) at the Jiuquan Satellite Launch Center. The crew arrived at the space station around six and a half hours later, docking at the nadir port at 19:32 UTC and entering the station around 21:04 UTC.

Shenzhou 18 is the 18th mission of the Shenzhou (“divine craft”) program and the 13th of these to be crewed. As with other missions in this series, the vehicle will be the Chang Zheng 2F which is a human-rated two-stage version of the 2E, which itself was derived from the 2C. The vehicle was rolled to the pad last week on April 17.

Shenzhou 18 CZ-2F/G rolled out to the pad - April 2024 (Credit - CCTV)

Shenzhou 18 CZ-2F/G rolled out to the pad – April 2024: (Credit: CCTV)

Active since October 2011, the Chang Zheng 2F/G first launched crew for Shenzhou 8 and this vehicle is flying for the first time this year. It has been over 20 years since Shenzhou 5 launched the first crewed mission for the Chinese space program, becoming the third country in the world to achieve independent human spaceflight.

The commander for this mission is Ye Guangfu who has 182 days of experience in space and previously flew on Shenzhou 13. He was accompanied by Operator Li Cong and System Operator Li Guangsu. The taikonauts from Shenzhou 17 have been on the station since last October. They are expected to return to Earth on April 30, following a handover ceremony and after sharing the station with the new crew for around four days.

Falcon 9 Block 5 | Galileo FOC FM25 & FM27

In the wake of Starlink Group 6-53 delivering SpaceX’s 300th booster landing earlier this week, this mission did not attempt a landing and expended booster B1060 on its 20th and final flight. This booster has supported numerous Starlink missions into Groups 4, 5, and 6 as well as Transporter 6, Galaxy 33 & 34, and the IM-1 mission launching the Nova-C lander, Odysseus.

With the company’s continual increase in both launches and recoveries, expending boosters have become rarer. Four months ago, the Falcon Heavy center core B1084 was the last for which there was no recovery attempt on the USSF-52 mission in late December. The last time a single Falcon 9 first stage was expended dates further back to late November 2022 when B1049 was expended on the Eutelsat 10B mission. Booster B1051, which coincidentally launched Galaxy 31 & 32, was also expended just 11 days prior and had continually set milestones as the first booster to be recovered eight, nine, ten, 11, and 12 times. Support ship Bob headed north to recover the fairings, however, and was already at sea having already recovered the fairings from the Starlink Group 6-53 mission earlier this week.

Lift-off for this mission took place at 8:04 EDT on Saturday, April 27 (00:34 UTC on April 28) from LC-39A at the Kennedy Space Center in Florida. The payload was a pair of satellites massing 1,603 kilograms for the European Space Agency’s (ESA) Galileo constellation targeting a medium-Earth orbit at 23,616 km altitude, inclined 56 degrees. Initially expected to be launched on a Soyuz, then moved to the delayed Ariane 6, ESA finally contracted SpaceX to lift this long-delayed payload.

Rubidium Atomic Clock development at Leonardo's headquarters in Nerviano, Milan (Credit: ESA)

Rubidium Atomic Clock development at Leonardo’s headquarters in Nerviano, Milan. (Credit: ESA)

This global navigation satellite system is named after Italian astronomer Galileo Galilei and went live in 2016 with the intention that European nations do not have to rely on the US GPS or Russian GLONASS platforms. Usage of the lower precision services is open and free to access, while the higher-precision services have 1-meter precision for positioning and are a paid-for service. These satellites begin to build the next generation of the constellation which will replace older equipment, with the completed constellation hosting 10 satellites in each of three planes.

Atomic clocks are a critical pillar in satellite navigation and are already utilized on satellites in this constellation. ESA recently signed a €12 million contract with Leonardo S.p.A to design, develop, and qualify a new technology for pulsed optically pumped rubidium atomic clocks. These experimental models will fly alongside the currently operational clocks used for Galileo services while they undergo in-orbit verification.

This could be the last or the penultimate launch from LC-39A before it is reconfigured for Falcon Heavy which is expected to lift the GOES-U mission in late June. These preparations can typically leave a gap of around 40 to 50 days between the previous use of the pad and a Falcon Heavy launch.

Falcon 9 Block 5 | Starlink Group 6-54

The second Starlink mission of the week was originally scheduled to launch from SLC-40 at the Cape Canaveral Space Force Station on Friday but was then shifted to Sunday, April 28. Lift-off occurred at 5:50 PM EDT (21:50 UTC) at the start of a typically four-and-a-half-hour window. The payload was another 23 Starlink v2-Mini satellites.

The booster B1076 was on its thirteenth flight and landed perfectly on the autonomous droneship Just Read the Instructions which was waiting further downrange. This booster has previously supported six other missions launching Starlink satellites into this same Group 6 shell, as well as Eutelsat 36D less than a month ago.  On its maiden voyage, it lofted the CRS-26 cargo resupply mission to the International Space Station in Nov. 2022.

(Lead image: Render of NASA’s ACS3 Solar Sail render in orbit with sunrise. Credit: NASA)

Related Articles