>>12436587 lb
A smooth stone is one coming from where a source of water runs.
It's made smooth by the force of water.
They are otherwise known as "river rocks".
https://builderssandandgravelinc.com/4-reasons-landscaping-with-river-rocks-is-eco-friendly/
So the smooth stone analogy seems to be pointing to how it was used, perhaps?
The stone was slung.
The stone hit him between the eyes.
Are the "eyes" the satellites?
Maybe something to think about.
And here's another thought.
What about the saying about waiting until you see the whites of their eyes?
Satellites are called "eyes of the sky":
https://www.cnet.com/news/eye-in-the-sky-behind-the-amazing-satellite-photos-you-see-on-google-and-instagram/