Two hot
Russian rocket engines had recently become available, the NK - 33 and NK - 43.
Not exact matches
That's been done before on some
Russian rockets, but what's unusual in this case is that the
engines will be mounted on a disk that spins at 720 revolutions per minute.
Complicating matters, both the Boeing and Sierra designs rely on Atlas 5
rockets to get to orbit, which in turn rely on
Russian - made RD - 180
engines, Handberg notes.