Stargate Atlantis/Recap/S02 E19 Inferno

"Weir: I don’t see any volcano.

McKay: Because you’re standing inside it right now."

The Atlantis team answers a call for help from the world of Taranis, where the locals are having trouble with their shield generators. Taranis turns out to be protected by Ancient technology powered not by a ZPM, but by the geothermal energy of the planet iself. The Ancient base of operations is built inside the caldera of a currently inactive supervolcano for this reason. In recent days, however, there have been ever-increasing tremors causing shield failure, so McKay gets to work with hot Taranian scientist Dr. Norina Pero to help put things right.

It turns out the Taranians have more than just cool shields. The Taranian Chancellor Lycus shows a delighted Col. Sheppard the base's hangar bay - and contained within it, a battle cruiser identical to the Aurora, called the Hippoforalkus. Which of course Sheppard immediately changes to Orion. The happy christening is interrupted by urgent news from McKay - powering the shields constantly for the last year (that is, since the Wraith woke up and went on a rampage) has caused the supervolcano to come back to life several thousand years early. It could blow any time now, taking half the continent with it and filling the atmosphere with ash - which will in turn blot out the sun and choke out all life for the forseeable future. It's time to evacuate all the Taranians to Atlantis - now.

The Chancellor is understandably suspicious that impending planetary doom turned up just after he showed Sheppard an impossibly cool ship that he could desperately use - but he consents to the evacuation anyway. McKay and Norina try to get the Orion working while the rest of the population heads for the stargate. Only the first wave of Taranians is able to escape to Atlantis before another tremor opens up a fissure - and the gate is sucked down into molten lava. Being suddenly cut off from his people in a strange place makes Chancellor Lycos even more suspicious, and Weir sends the Daedalus to investigate.

The Daedalus confirms the disaster and starts to vacuum up the refugees, but life support issues will require it to make four trips to get everyone out - at 12 hours each. Sheppard does his best to motivate McKay with the threat of impending death and starts moving the remaining refugees onto the Orion - where they are unfortunately shielded from the Daedalus' beam technology. Lava covers the hangar doors, preventing their escape, and it seems impossible to get the Orion's sublight engines working anyway. When the volcano eventully blows, their shields should be able to hold for a mere 4.1 seconds before they are all horribly incinerated.

Fortunately, when the volcano does blow a few minutes later, it does so with enough force to throw the Orion up into the atmosphere - at which point McKay opens up a hyperspace window sufficient to put them into orbit before the allotted 4 seconds are up. The Daedalus is then able to ferry everyone back to Atlantis at their leisure. The Taranians are safely relocated to a non-exploding planet and in return Chancellor Lycus graciously loans Weir the Orion, to be used in the imminant fight against the Wraith.

Tropes
"McKay: I have a very firm grasp of Ancient technology.
 * Accidental Innuendo: plenty!
 * Apocalypse How: Class 5
 * Call Back: To the episode "Trinity":

Sheppard: You’ve blown up entire planets, Rodney.

McKay: That wasn’t my fault!

Sheppard: Well, it didn’t do it by itself!"

"Hermiod: Colonel. I believe the eruption will occur in fifty-two seconds.
 * Chekhov's Volcano: in fact, it's a supervolcano!
 * Exact Time to Failure: both Hermiod, with the eruption, and McKay with the shields.

Caldwell: Are you sure?

Hermiod: I would not state it if I wasn’t."


 * Hot Scientist: Norina, who has McKay and Sheppard making idiots of themselves for her benefit the whole episode through.
 * Shout-Out: The Orion is named for the protagonists' ship in the German cult Sci-Fi series Raumpatrouille - Die phantastischen Abenteuer des Raumschiffes Orion (Space Patrol - The Fantastic Adventures of the Spaceship Orion) from 1966. The 2003 special edition DVD was a gift to director Peter DeLuise from German journalist (and Stargate correspondant) Robert Vogel.
 * You Look Familiar: Chancellor Lycus is Dr. Warner, Dr. Frazier's predecessor on SG-1.