For the second time in 2024, Northrop Grumman’s Cygnus spacecraft delivered a bounty of science experiments and cargo to the crew aboard the International Space Station (ISS). The CRS NG-21 mission dodged the weather that scrubbed it on Saturday, with a Sunday lift off on a Falcon 9 from Space Launch Complex 40 (SLC-40) at the Cape Canaveral Space Force Station in Florida.
Cygnus’ ride to space was on SpaceX’s workhorse two-stage Falcon 9 launch vehicle, utilizing a flight-proven first stage. The launch sent the spacecraft into low-Earth orbit on a trajectory inclined 51.6 degrees to the equator, putting it in the same orbital plane as the ISS. After stage separation, the booster returned to the launch site (RTLS) for landing, culminating in a soft touchdown at Cape Canaveral’s Landing Zone 1.
For SpaceX, this launch was the second in the month of August, and the 75th for the company in 2024 so far. NG-21 was also the first customer mission flown by SpaceX since the Starlink 9-3 launch failure that occurred on July 11.
Cygnus displays its circular solar arrays while attached to the Canadarm2 robotic arm. (Credit: NASA)
The NG-21 mission marks the second of three Cygnus cargo flights that will launch aboard SpaceX Falcon 9 rockets, having previously used the now-retired Antares 230+ launch vehicle as its main method of travel. These three missions will help Northrop Grumman continue to fulfill its ISS cargo resupply contract obligations until the upgraded Antares 330 enters service.
Cygnus’ rocket-agnostic design enables this capability, much like how it was utilized for three missions spanning from 2015 to 2017 after the failed launch of Antares during the CRS Orb-3 mission in October 2014. While Antares was grounded for modifications, Cygnus was able to fly on United Launch Alliance’s (ULA) Atlas V rocket to maintain its cargo quota.
After launch, the Cygnus NG-21 spacecraft began its chase of the ISS, taking a day and a half before arriving for capture by the Station’s Canadarm2. The cargo ship was captured at 3:11 AM EDT (07:11 UTC) on Tuesday, Aug. 6, after which Cygnus was berthed to the nadir (Earth-facing) port of the Unity module at 5:33 AM EDT (09:33 UTC). NASA astronaut Matthew Dominick performed the capture.
Honoring the late STS-51-L commander, Francis R. “Dick” Scobee. (Credit: NASA)
The Cygnus NG-21 craft has been christened the S.S. Francis R. “Dick” Scobee, in honor of the fallen commander of the ill-fated Challenger STS-51-L mission. This aligns with a tradition in which the spacecraft is named after deceased astronauts or other prominent figures in spaceflight. The tradition was started by Orbital Sciences (who originally developed Cygnus) and carried on by Northrop Grumman.
The S.S. Francis R. “Dick” Scobee will be delivering around 3,843 kg (8,472 lb) of cargo to the orbiting outpost. This cargo includes numerous scientific experiments, such as tests of water recovery technologies, a process to produce blood and immune cells in microgravity, and a demonstration of centripetal force for STEM engagement.
In addition to the experiments, food, and supplies, the S.S. Francis R. “Dick” Scobee will carry an iROSA solar array upgrade kit — the eighth such kit needed for the installation of the final set of upgraded arrays. Furthermore, Cygnus will deliver spare water tanks and pump assemblies for Station maintenance.
Preview of the cargo manifest that will be delivered to the ISS during the NG-21 mission. (Credit: NASA)
Cygnus will remain berthed to the ISS for five and a half months, during which time it can provide an orbital reboost capability. Once it nears the end of its stay, it will be loaded with trash from the Station before unberthing and departure.
Afterward, Cygnus will be commanded to make a destructive reentry into Earth’s atmosphere over the southern Pacific Ocean, marking the end of its mission.
Alongside the NG-20 and NG-21 flights, the NG-22 mission is also slated to launch on Falcon 9 from Cape Canaveral with a tentative February 2025 date. NG-23 will be the first Cygnus mission to utilize the Antares 330, flying on its debut launch no earlier than the third quarter of 2025.
From left to right: cosmonaut Alexander Gorbunov, astronaut Nick Hague, astronaut Zena Cardman, and astronaut Stephanie Wilson undergo training for the SpaceX Crew-9 mission. (Credit: SpaceX)
The month of August is lining up to be a somewhat busy period for the ISS, with multiple incoming and departing vehicles. The arrival of Cygnus NG-21 is scheduled to be followed a few days later by the departure of the Russian Progress MS-26 cargo ship and the launch and arrival of the SpaceX Crew-9 crew rotation mission. The departure of Boeing’s Starliner spacecraft as part of the CFT mission is also in flux, with no definite return date set at this time.
(Lead image: Falcon 9 launches NG-21. By Julia Bergeron for NSF/L2)