The Soviet Luna program was the first to fly by the moon, impact land on the moon, soft land on the moon, and get photos of the far side of the moon: https://en

The Soviet Luna program was the first to fly by the moon, impact land on the moon, soft land on the moon, and get photos of the far side of the moon: https://en.wikipedia.org/wiki/Luna_programme https://en.wikipedia.org/wiki/Luna_programme It’s not that Korolev was irreplaceable necessarily, but the soviet union being what it was his death logistically derailed the space program.