Who knows which episode of Altman this is?

According to your description, it should be the second episode of the first generation of Altman, attacking invaders.

The star Baltan appeared in the picture. It is speculated that his hometown was destroyed by a nuclear bomb, and he must find a suitable planet.

It is said that the most ironic episode is actually like that, only describing the performance of a potential fear of nuclear bombs by Japanese people at that time. After all, it has only been 20 years since the human tragedy in Hiroshima and Nagasaki, and the Japanese still have a lingering fear. Moreover, Japan was at war at that time, and there was indeed a nuclear arms race between the United States and the Soviet Union. The destruction of baltan by the nuclear bomb experiment is nothing but a reflection and vigilance on reality.

At the end of the plot, Altman used his perspective to find the baltan immigrant's boat and shot it down (direct explosion ~), killing 2.03 billion baltan people on board (which is the most ironic).

It is worth mentioning that baltan is the first cosmic man in the Altman series (and the laughter is magical). Because modeling classics have appeared in many Altmans, most of them ended in tragedy (full of loyalty)