Fallout Wiki
Fallout Wiki

Archimedes I activated

Archimedes I is a land-based directed energy weapon created by Poseidon Energy at HELIOS One, appearing in Fallout: New Vegas. It is the predecessor of the space-based Archimedes II.


Established before the Great War as a next generation solar power plant, hailed as the Dawn of a Golden Age, HELIOS One was more than just a renewable source of energy. It doubled as a research and development facility for the U.S. Army's top secret energy weapons: Archimedes I and Archimedes II. The military side of affairs was handled by Brigadier General Scott Lowe, who oversaw the testing of the weapon on site.[1]

Tests of the weapons conducted on February 16, 2077, were less than pleasing: While both weapons proved functional and successful, several minor systems were overloaded despite all precautions taken, and the entire plant shut down for two and a half minutes. Nearby facilities also experienced system-frying power fluctuations at the time of the test, to include the Black Mountain communications array and the military bunkers at Hidden Valley. The team decided to focus on minimizing collateral damage and reducing downtime under the oversight of Brigadier General Scott Lowe, but further development was precluded by the Great War.[2][3]

When the Mojave chapter of the Brotherhood of Steel occupied HELIOS One, Elder Elijah attempted to reactivate Archimedes I and use it to defend the facility from the NCR forces during Operation: Sunburst. However, he was unsuccessful, only getting as far as reactivating the security systems to prevent the Republic from continuing his work before disappearing entirely.


Archimedes I was a proof of concept for Poseidon Energy's new energy weapon design. The most revolutionary element of its design was the method of power transfer: Using microwave radiation to transfer energy from the solar plant to a remote receiver and converting it back into a usable form.[4] The weapon was designed to act as a Plant Defense System and integrated into the solar collection tower, together with autonomous targeting routines that would acquire any hostile targets without the need for a human operator.

The player character can activate the Archimedes plant defense system from HELIOS One's observation deck at any time upon accessing the solar collection tower. The test fire will wipe out NCR forces outside, resulting in a severe reputation drop with the Republic (though no Karma loss). If Arcade Gannon is present, he will immediately leave one's party and attack, in a desperate attempt to deactivate the system. If the system is activated during That Lucky Old Sun, the Legion will subsequently occupy the plant. Sending power across the Mojave Wasteland at emergency power levels will disable the plant defense system.


It should be distinguished from Archimedes II, the second iteration of the system, which is an orbital based laser system and can target any outdoor location in the Mojave Wasteland.


Reflector warning

Warning 1

Warning 2

Countdown warning

Countdown concluded


  • It is not necessary to divert power to Archimedes II during That Lucky Old Sun in order to activate Archimedes I. Archimedes I can be activated after selecting any of the first four power options from the HELIOS One mainframe terminal (any of them but the "Full Region, Emergency Power Level" option).
  • Archimedes I can be activated (once) at any time after HELIOS One comes back online unless as mentioned above the player character has selected "Full Region, Emergency Power Level".
    • If activated after the quest has been completed, Caesar's Legion will not take over HELIOS One even if all NCR soldiers are dead.
    • This will not activate Euclid's C-Finder, which requires diverting power to Archimedes II during That Lucky Old Sun.

Behind the scenes

Archimedes is a reference to the real world Archimedes, a mathematician, physicist, engineer, inventor, and astronomer in Ancient Greece. He devised the "Archimedes heat ray" which used mirrors to focus sunlight onto approaching enemy ships, causing them to catch fire.