Firefly Aerospace's ( FLY) stock is sputtering, just one day after its trading debut, when enthusiasm for the new listing sent shares soaring. The space company's stock was down 13% to about $52 Friday afternoon, wiping out more than half its gains in its first day of trading yesterday.

Another space stock is going public. But this isn't just any old space stock -- this one already landed on the moon.

Firefly Aerospace, a Texas-based commercial space company known for its lunar landers, raised $868 million in an upsized IPO.Why it matters: The IPO window is open wide enough to fly a spaceship through it,