T-45d power armor

The T-45d Power Armor was the first version of Power Armor to be successfully deployed in battle by the United States in 2067 during the Sino-American War and is the most basic model of Power Armor in Fallout 3.

Originally developed and manufactured for the United States Army by American defense contractor West Tek, it is currently employed by several factions, including the Brotherhood of Steel and the Brotherhood Outcasts. Each of these factions have their own variants of Power Armor.

History
In 2067, the first suit of T-45d Power Armor was deployed in Alaska during the start of the Anchorage Reclamation in the midst of the Sino-American War. This Power Armor was incredibly effective against Chinese tanks and infantry. Its ability to allow a single infantryman to carry heavy ordinance that otherwise required a team of soldiers to transport and operate became key in various localized conflicts on the Alaskan front, and it allowed American soldiers wearing the armor to destroy entire towns occupied by Chinese troops without endangering themselves. In 2076, the more advanced T-51b Power Armor variant was introduced into combat duty.

Nearly two centuries later in 2277, around one hundred T-45d suits were discovered by the Capital Wasteland Brotherhood of Steel in the ruins of the Pentagon and were extensively used by Brotherhood Knights and Paladins, along with modifications and makeshift repairs. The Brotherhood lacked the technology to begin manufacturing Power Armor of their own and so had to constantly repair the suits they had recovered.

Design
The T-45d lacks the mobility of later Power Armor models (such as the T-51b Power Armor) because of its less advanced servo design; as a result it limits the wearer's agility. The first version of T-45d Power Armor deployed on the front lines against the Chinese was powered by Small Energy Cells and it burned through them at an alarming rate. Some later versions were either manufactured or retrofitted by the US Army with built-in microfusion packs, a technology that was developed later by West Tek.

While the T-45d armor is similar in its overall shape to the more advanced T-51b Power Armor, it is significantly less advanced than its later counterpart, and uses riveted steel plates instead of plastic composite materials in its construction. Various electronic and mechanical subsystems of the armor are exposed on the outside of its casing rather than sealed within as in the T-51b, making it far more susceptible to damage. In addition, a specialized body suit is required to be worn underneath the T-41b's armored shell in order to facilitate linking the armor's servos to the wearer's own motions and to make the armor more bearable because of its heat dissipation problems.

Variants
Wearing Power Armor requires the player to receive Power Armor Training by talking to Paladin Gunny in the Citadel, by completing the Anchorage Reclamation simulation (Operation: Anchorage), or having acquired Ashur's Power Armor and left The Pitt (The Pitt (add-on)). In addition, it can be unlocked via console commands in the PC version with.

T-45d Power Armor can be repaired using components from the T-51b Power Armor, but the reverse cannot be done. This might be the result of a bug or it might be the fact that the T-51b Power Armor is simply more advanced that its counterpart and uses parts that cannot be substituted with T-45d parts.

Power Armor
Regular Power Armor can be acquired from the Capital Wasteland's merchants, although they rarely appear in stock. You also receive a complete suit of Power Armor in 100% condition from Sarah Lyons at the beginning of the game's final quest, Take it Back!. It can also be acquired from some fallen Brotherhood of Steel members. Power Helmets can be found from merchants and fallen Brotherhood of Steel members.

Brotherhood Power Armor
This variant is found on most fallen Brotherhood of Steel members and has the same appearance and attributes as regular Power Armor. There are no differences other than the name and that it will not appear in a merchant's stock (This armor is very rare since most Brotherhood members' inventories are placed with "normal" T-45 Power Armour).

Outcast Power Armor
Brotherhood Outcast Power Armor can be acquired from the corpses of fallen Outcasts and from Fort Independence. However, having Outcast variants in your inventory (equipped or not) when speaking to Protector Casdin will cause him to confiscate the armor unless you have gained the Outcasts' trust. Outcast Power Helmets can be acquired from fallen Outcasts.

Lyons' Pride Power Armor
Lyons' Pride Power Armor is the same as regular Power Armor, except that the Lyons' Pride insignia is on the shoulder instead of the standard Brotherhood of Steel insignia. It can be acquired from the corpses of dead Lyons' Pride members or reverse-pickpocketing: Sentinel Lyons, Knight Captain Gallows, Paladin Vargas, Paladin Glade, Paladin Kodiak and Knight Captain Dusk.

Army Power Armor
Army Power Armor & Helmet can only be acquired on the PC version using console commands or modified save files through Hex modding. It has a US Army band on each shoulder.

Linden's Outcast Power Armor
A unique Outcast Power Armor obtained as a quest reward for completing the quest Oasis in Leaf Mother Laurel's favor.

Prototype Medic Power Armor
This is a variation of the Army Power Armor and can only be found in the Old Olney sewers. This suit automatically applies Med-X and can alert you about threats in the area.

Ashur's Power Armor
Ashur's Power Armor is a unique version of the Tribal Power Armor and is only found with The Pitt add-on. It is worn by Ashur, leader of The Pitt.

Tribal Power Armor
Tribal Power Armor is only found with The Pitt add-on. It can be acquired by giving 100 Steel Ingots to Everett for the unmarked side quest Mill Worker.

IDs
There are several variants of this armor model; each of these variants have a different Base ID as given in the following table.

Behind the Scenes

 * The history of the T-45d was mentioned in the Fallout Bible timeline, while its designation was first mentioned in the Van Buren tech demo by Corporal Armstrong who wears the armor. The armor itself is ubiquitous in the Capital Wasteland, and the Museum of Technology has a log of proposed exhibits for 2078, which includes a suit of T-45d Power Armor.
 * According to the Fallout 3 art book, the Power Armor was designed directly in 3D, skipping the concept art phase.
 * A texture for a Pink Power Armor can be found in the "Fallout - Textures.bsa" file. It has a white heart on its chest.

Quotes

 * "Though that design was intended for the "real" F3 power armor (T-51b), we wanted to have an alternate texture for the armor Armstrong describes, T-45d, which ran off small energy cells. It would only have appeared in the tutorial as a "back in the day" detail." - J.E. Sawyer
 * "I [...] have fifty three hours of field experience in the T-45d Power Armor, citizen. Most of those were during the Anchorage Reclamation.[...]This T-45d eats up small energy cells like Chans at a rice buffet!" - Corporal Armstrong