What they didn't say about Northrop Grumman's Cygnus XL

On Sunday evening, I mentioned watching SpaceX launch Northrop Grumman's Cygnus XL cargo transporter to the ISS.  I watched the flight without looking up anything on this cargo drone, expecting it to be a duplicate of every other mission Grumman has ever launched.  Yeah, it was launched by SpaceX but that's not new either.  

It's not like every other mission.  As Stephen Clark of Ars Technica puts it,"Northrop Grumman's new spacecraft is a real chonker."  

... This mission, known as NG-23, is set to arrive at the ISS early Wednesday with 10,827 pounds (4,911 kilograms) of cargo to sustain the lab and its seven-person crew.

By a sizable margin, this is the heaviest cargo load transported to the ISS by a commercial resupply mission. NASA astronaut Jonny Kim will use the space station's Canadian-built robotic arm to capture the cargo ship on Wednesday, then place it on an attachment port for crew members to open hatches and start unpacking the goodies inside.

It's not unusual for things discussing size to reach for strange analogies, like expressing the size in the number of giraffes, or something equally unintelligible (to most of us).  Thankfully, they don't go quite that far to silly.  

The cargo module is 5.2 feet (1.6 meters) longer on the Cygnus XL. The full spacecraft is roughly the size of two Apollo command modules, according to Ryan Tintner, vice president of civil space systems at Northrop Grumman. Put another way, the volume of the cargo section is equivalent to two-and-a-half minivans.

"The most notable thing on this mission is we are debuting the Cygnus XL configuration of the spacecraft," Tintner said. "It's got 33 percent more capacity than the prior Cygnus spacecraft had.

I feel comfortable saying it's 1-1/3 times the capacity of the original Cygnus - at least, I find that much easier to grasp than how many more bananas or giraffes it could carry.  This is the first launch of the Cygnus XL, so they're going a bit more cautiously than a "plain old" Cygnus would warrant. 

Dina Contella, NASA's deputy ISS program manager, said engineers assessed how the larger Cygnus XL might affect the space station's thermal control and life support systems. Engineers also made sure the station's robotic arm could handle the heavier spacecraft.

"The NG-23 vehicle is packed with consumables like nitrogen, oxygen, food, and toilet parts, and it has a large number of spare parts that are required for systems like, for example, our urine processor," Contella said. The station was running low on some of these space parts over the past year. "We'd like to have a good reserve for the future," she said.

For refresher (review) of the older story, until a few years ago, Northrop Grumman launched these Cygnus cargo ships on an older vehicle of theirs called the Antares.  Antares can't fly any more because parts of it were made in Russia and parts were made in the Ukraine.  When that situation started becoming apparent a couple of years ago, Grumman contracted with Firefly Aerospace to build a next version of the Antares called the Antares 330 at the same time they contracted with SpaceX to launch three Cygnus missions for them.  The original stories claimed the new Antares might fly by the end of '24.  Obviously, we're well past that and the latest estimates are it will be by the end of 2026.   

NASA has a multibillion-dollar contract with Northrop Grumman to routinely resupply the ISS. Without a rocket of its own, Northrop Grumman inked a contract with SpaceX for three Falcon 9 launches to carry the resupply missions until engineers could develop a new, all-domestic version of the Antares rocket. Sunday's launch was the last of these three Falcon 9 flights. [Emphasis added: SiG]
...
Tintner confirmed Friday that Northrop has purchased a fourth Falcon 9 launch from SpaceX for the next Cygnus cargo mission in the first half of next year, in a bid to bridge the gap until the debut of the Antares 330 rocket.

In one sense, having SpaceX launch Cygnus cargo missions is very much like "nothing much has changed" in getting cargo to the ISS.  Instead of Falcon 9s lifting Cargo Dragons and Antares rockets lifting Cygnus cargo ships, Falcon 9s are lifting everything. The important difference is the Falcon 9 can put heavier payloads in orbit than the old Antares rocket.  This allows NASA to take full advantage of the additional volume on the Cygnus XL. The combined Falcon 9 and Cygnus XL can deliver more cargo to the ISS than SpaceX's own cargo ship.  (For as long as SpaceX wants to keep the Cargo Dragon smaller).

Northrop Grumman's Cygnus XL supply ship inside the payload fairing of SpaceX's Falcon 9 rocket. Credit: SpaceX