The Antares always was a subcontractor mashup. Not a single piece of it is actually made by Northrop Grumman, as far as I can tell.
The Castor 30XL is an ATK Thiokol product. The glue is an Elmer's product.
Russia's invasion of Ukraine is being felt at Northrop Grumman, forcing it to make alternative plans that now include asking Firefly Aerospace to build the first stage of its Antares rocket. The Antares' maiden flight was in 2013 with a first stage powered by a pair of Aerojet AJ26 rocket engines. Those engines, refurbished NK …
Think of NASA's options if a problem with Merlin engines prevents launches for a few months. Crew and cargo dragons become unavailable. If Cygnus also depended on Merlin the other operational cargo choices are a Russian Progress or a Chinese Tianzhou.
They could use a Starliner as an expensive cargo vehicle - if they can launch it. The last remaining Atlases are spoken for, Vulcan is not ready and the only other choice is Falcon 9.
A suspect NASA are only allowing Cygnus on Falcon as a temporary measure because there is nothing else available right now.
There were over 30 Falcon 9 launches last year and there have been more than 40 so far this year. That works out to 630 engine firings, and I think there have only been three issues:
1) In 2020, a single engine shut down early on ascent. The mission was successful, but the booster did not make it back for a controlled landing.
2) In 2020, a launch self-aborted when 2 engines started early. The cause was traced to contamination and processes put in place to ensure it cannot happen again.
3) In 2021, an engine shut down due to the entry of hot gasses through a damaged heat shield (not part of the engine, as such). Again, the mission was successful, but the booster did not make it back for a controlled landing.
So, there is a risk of having all your eggs in one basket, but that looks like a good basket,
A small space agency with no direct ability to launch vehicles into space.
It expands and places objects in low earth orbit with it's own reusable space craft.
It expands and sends probes that are destined to fully leave our solar system one day.
It expands and lands men on the moon, and brings them back alive.