Astronauts are employees of the government and are thus barred from suing in lieu of receiving the government equivalent of worker's compensation. This wouldn't bar a suit against a third-party contractor who made a defective product, but I suspect that their contracts contain a waiver of liability for negligence or defective products given that this is highly experimental technology.
Certainly, it would not be homicide as it was an accidental death of someone who consented to the high risk of accidental death involved.
The dog would have been the property of the government, and the government wouldn't sue itself for damages to the dog. The harm that comes to animals in legitimate scientific research is not considered cruelty to animals as it is justified by a higher legitimate purpose and not for the intent of gratification of someone who enjoys torturing animals and would have been cleared by a scientific ethics committee in advance.