Hello! Here are my nitpicking suggestions based on a version that says it was edited 5 days ago:
First sentence: Think about how many actions happen at once here. Salute, stand, machine opens.
“a slight smirk on his face”: “with”. And whose face, Michaels’ or the officer’s?
“The scientist behind him muttering”: Not quite grammatical as worded. I’d say “was muttering” or “muttered”.
“sleep, and possibly death”: Try adding a comma after “death”.
We see “the machine” three times but without description. It would help to have some detail, or another word. I’m being silly here, but you could say “transmogrifier” for instance to replace one instance of “machine”. More seriously, something like “the titanium sphere” or “the bio-chamber”.
“tried not to laugh”: Sounds like a POV shift as worded. Try “stifled a laugh”, since that suggests he’s doing something Michaels might see/hear instead of sort of showing us the general’s thoughts.
Also, would a general be friends with a private? That’d be an unusual relationship.
“once we’re sure”: Of what? I’m reminded of a “chakat” transformation story wtih someone waking up similarly shackled. The military types explained and apologized: “We just want to make sure you won’t attack anybody. Will you agree to walk into the prison cell over there for long enough that we can observe you and confirm you’re still sane?”
“a small wag at the idea of being”: Being what?
“Dmitri nods and gives a low sigh”: This is a tense change. Also there’s no blank line before this paragraph.
“tail down and eyes defiant”: Inconsistent attitude with the purring in the paragraph before.
“The door was opened”: The passive voice isn’t necessary here.
Overall:
Interesting, and it’s a good start, but for me it felt like the story wasn’t complete. My problem with it is that the main character doesn’t go through any conflict. We’re told there’s some problem that could end humanity as we know it, and that Michaels is some sort of ambassador/test subject for living as an anthro among other anthro creatures, but we don’t get to see what trouble he has with this new life. We’re told his father’s upset and that some of the anthros will be too. It would be nice to see that “on stage”. You can address these things with a longer story. The potential for conflict is there, which is good; we’re just not seeing it yet.