SpaceX is back to lending a hand to Northrop Grumman with a planned launch of its Cygnus cargo spacecraft on a resupply mission to the International Space Station from Cape Canaveral Space Force Station on Saturday.

A Falcon 9 rocket topped with Cygnus is set to launch on the NG-21 mission from Canaveral’s Space Launch Complex 40 at 11:29 a.m. with a backup option on Sunday.

The booster is flying for its 10th time and will aim for a recovery landing back on land at Canaveral’s Landing Zone 1, which means the Space Coast and Central Florida could be in line for a sonic boom.

Space Launch Delta 45’s weather squadron forecasts only a 50% chance for good launch conditions, which drops to 10% in the event of a delay to Sunday because of the forecast tropical storm that will be hitting Florida. If it doesn’t fly Saturday or Sunday, teams would stand down Monday and potentially try again on Tuesday or Wednesday.

SpaceX knocks out company’s 50th Space Coast launch of the year

This is the second time SpaceX has flown the Cygnus spacecraft since Northrop Grumman stopped launching them from Virginia in 2023 on their Antares rockets. A new version of Antares with partner Firefly Aerospace is in the works that will use American engines and rocket parts in lieu of the Russian and Ukrainian-supplied parts on the version no longer flying.

It launched the NG-20 mission for Northrop Grumman in January, the first of at least three missions as the surrogate launch provider with NG-22 slated for 2025.

SpaceX has its own contract to ISS resupply missions with its cargo Dragon capsule, but it now responsible for launch service for Cygnus as well until Antares comes back online. The two companies are slated to be joined by a third resupply contract winner, Sierra Space, after its Dream Chaser spacecraft makes its initial trip to the ISS and achieves certification. Dream Chaser will fly on United Launch Alliance Vulcan Centaur rockets, but won’t make its first flight until at least 2025.

This is the 21s resupply mission for Northrop Grumman. The Cygnus spacecraft is named the S.S. Francis R. “Dick” Scobee in deference to the commander of Space Shuttle Challenger’s final mission STS 51-L, which blew up on its launch in 1986 killing Scobee and six others on board.

The capsule is filled with more than 8,200 pounds of supplies, and is slated to arrive to the ISS on Monday, when it will be grappled by the station’s robotic arm controlled by by Expedition 71 and NASA astronaut Matthew Dominick.

Some of the more than 1,700 pounds of science-related cargo arriving will be a test of some water recovery technology, a process to produce blood and immune stem cells in microgravity, studies on the effects of spaceflight on engineered liver tissue and microorganism DNA, and a balloon, penny and hex nut for a live centrifugal force science demonstration for students.

One notable item flying up is a spare pump assembly for the urine processor on board, an item that broke down before the June 6 arrival of Boeing’s Starliner, which had to shift its cargo manifest to bring up an emergency replacement. Other hardware flying up will support the rollout of the final rollout solar array and a system for a future exercise system going up in 2025.

Some of the personal items Starliner astronauts Butch Wilmore and Suni Williams had to discard to make room for the emergency urine system hardware will make its way up as well including clothing and food items.

Dominick will install Cygnus to the Unity module’s Earth-facing port where it will remain docked for nearly six months with a January 2025 planned departure, after which it will burn up on reentry into Earth’s atmosphere.

The Cygnus spacecraft has been flying for more than a decade. In recent years, the company added the capability to provide propulsive boost to the ISS as a backup to the station’s primary boost source from Russia.

When it leaves, it will haul away waste from the ISS.

The SpaceX launch will be the 55th from all launch service providers for the Space Coast, with SpaceX responsible for 51 of them.