The motor will eventually be on display as part of a planned Future of Spaceflight gallery devoted to commercial ventures beyond Earth. You'll have to wait a while to see it, though -- the exhibit isn't slated to open until 2024. It's not clear which other companies will find their way into the museum, although we wouldn't be surprised if SpaceX, Blue Origin and other well-known private outfits make the cut.

There's no doubt that this represents a marketing opportunity for Virgin. It's putting its name in the spotlight even though it has yet to fly a single commercial flight into orbit. If you can get past the grandstanding, though, the donation is still significant. It shows how private spaceflight has evolved from early concepts into something very real, even if there's still a lot of work left to be done.