History Recap / StarTrekVoyagerS4E22Demon

* DeathWorld[=/=]IDontLikeTheSoundOfThatPlace: The "Demon-class" planet.

* TormentByAnnoyance: Neelix and the Doctor have a back-and-forth where the Doctor does his work in sickbay while singing opera to annoy Neelix and three other sleeping crew members out of sick bay. [[DreadfulMusician Neelix]] responds by getting his bunkmates to participate in a multi-cultural sing-a-long -- to which the Doctor responds by relenting.

* CloningBlues

''Voyager'' is desperately low on fuel and Captain Janeway orders all nonessential systems to be shut down. Seven of Nine uses the astrometric sensors to detect a planet with deposits of deuterium, but the planet is a "Class Y" or "demon" planet, extremely hostile to humanoid life. When the initial effort to transport some deuterium to the ship fails, Harry Kim and Tom Paris go down in a shuttlecraft to retrieve some. There they discover that the deuterium is in a liquid form and somehow is able to stay in a very cool temperature. Unfortunately, their environmental suits start to fail, and both Tom and Harry run out of oxygen before they could reach the shuttle.

* SciFiWritersHaveNoSenseOfScale: So ''Voyager'' is down to sublight speed, yet they find a deuterium-rich planet less than a week away at one-quarter lightspeed. If it's that close, shouldn't they have already detected it? And when their first attempt to mine the planet fails, why would Janeway consider resuming course when they wouldn't make it to anywhere else?

* ArtisticLicensePhysics: Deuterium is an isotope of hydrogen, having one neutron in its nucleus where protium has none; a standard warp core combines it with {{antimatter}} to get energy. While deuterium accounts for only 0.02% of hydrogen in the naturally-occurring world, hydrogen itself is ''74%'' of the mass of the observable universe; the glowing red things on the front of a Starfleet vessel's engines are called "{{Ramscoop}}s," are used to pull protium out of, literally, the vacuum of space, and have been there since ''The Original Series''; and "heavy water," which contains man-made deuterium, was first created in ''1932''. ''Voyager'''s ability to make its own deuterium has been canonical since 1967. (The later episode ''[[Recap/StarTrekVoyagerS7E14TheVoid The Void]]'' actually made a crack about this before they find out it's ''actually rare'' in the titular void.) Additionally, it can only exist as a liquid at extremely low temperatures or very high pressures.

* ArtisticLicensePhysics: Deuterium is an isotope of hydrogen, having one neutron in its nucleus where protium has none. While deuterium accounts for only 0.02% of hydrogen in the naturally-occurring world, hydrogen itself is one of the most abundant things in the physical universe; the glowing red things on the front of ''Voyager'''s nacelles are called "{{Ramscoop}}s" and are used to pull protium out of, literally, the vacuum of space; and "heavy water," which contains man-made deuterium, was first created in ''1932''. (The later episode ''[[Recap/StarTrekVoyagerS7E14TheVoid The Void]]'' actually made a crack about this before they find out it's ''actually rare'' in the titular void.) Additionally, it can only exist as a liquid at extremely low temperatures or very high pressures.

* TormentByAnnoyance: Neelix and the Doctor have a back-and-forth where the Doctor does his work in sickbay while singing opera to annoy Neelix and three other sleeping crew members out of sick bay. [[DreadfulMusician Neelix]] responds by getting his bunkmates to participate in a multi-cultural sing-a-long -- to which the Doctor responds by relenting.

* ArtisticLicensePhysics: Deuterium is an isotope of hydrogen, having one neutron in its nucleus where protium has none. While deuterium accounts for only 0.02% of hydrogen in the naturally-occurring world, hydrogen itself is one of the most abundant things in the physical universe; and "heavy water," which contains man-made deuterium, was first created in ''1932''. (The later episode ''The Void'' actually made a crack about this before they find out it's ''actually rare'' in the titular void.) Additionally, it can only exist as a liquid at extremely low temperatures or very high pressures.

* ArtisticLicensePhysics: Deuterium is only rare in comparison to protium, the other isotype of hydrogen. It is literally one of the most abundant things in the physical universe. The later episode ''The Void'' actually made a crack about this before they find out it's ''actually rare'' in the titular void. Additionally, it can only exist as a liquid at extremely low temperatures or very high pressures.

* ArtisticLicensePhysics:
** Deuterium is only rare in comparison to protium, the other isotype of hydrogen. It is literally one of the most abundant things in the physical universe. The later episode ''The Void'' actually made a crack about this before they find out it's ''actually rare'' in the titular void. Additionally, it can only exist as a liquid at extremely low temperatures or very high pressures.

* InsaneTrollLogic: While Tom and Harry are trapped on the planet and they can't wait for them too long, as the ship is slowly running out of energy and just staying in orbit of the planet is dangerous, Chakotay suggest taking a shuttle and go look for them. Janeway dismisses this as too dangerous-so she decides to land the whole ship on the planet, which will take big amount of energy and the ship might not even survive landing due to its weakened shields.

* ExtremophileLifeforms: he Silver Blood, a deuterium-based race encountered on a Class Y planet. The episode takes its name from the fact that Class Y planets are sometimes termed "demon" worlds because they're basically FireAndBrimstoneHell (start with temperatures averaging 500 Kelvin and go downhill from there).

** The "demon planet" is mentioned to have temperatures of 500 Kelvin, which is just shy of the melting point for tin. Yet, the soft polyester interior of the shuttle is exposed to such an environment through an open hatch and is completely fine.