R3 and R4-series schematics
The R4 had the same outward appearance of an R2 or R3 droid below the dome, but to save money on production, items such as the video display screen and miniature fire extinguisher were omitted. The holographic projector/recorder unit was retained, but relocated to the top of the head dome to allow for use of a cheaper, less miniaturized unit with a smaller rotational axis. The droid's Intellex VI computer was advanced, but geared toward common repulsorcraft designs and specs for commercially available space transports. The computer brain was designed with more space between the components, lowering production costs, but requiring a larger head dome, and likewise eliminated many of the function indicators and gadgetry found on other R-series head domes. The R4 was unsuited to the task of starfighter astromech; it could only hold the coordinates for a single hyperspace jump in its astrogation buffer, a one way trip for any fighter jock.
The droids were rugged; able to shrug off the nicks and dents common to a working garage environment as well or better than other R-droids. IA was pleased to discover that, with regular maintenance checks, the R4 outlasted its design parameters for operational life, weather endurance, personality matrix stability, and time elapsed between recharge sessions.
R4-T8
Because of their increased durability, R4s were the preferred "mech" droids used by the Jedi. Given the interstellar nature of their work, however, most of the R4 droids purchased for the Jedi were modified to include the more expensive R2 style head. This gave them many of the best features of the R2 and R4 series. Many of these droids were further modified by mechanics in the Jedi Temple to permanently interface with the Delta-7 Aethersprite-class light interceptor, until the Jedi moved on to the Delta-7B and Eta-2 Actis-class interceptor. Even so, pilots retained R4 units in the Eta-2 interceptor.
Mass-market buyers liked the R4, as did the freedom fighters of the Alliance to Restore the Republic. They reasoned that no one would be suspicious of a mass purchase of astromech droids, the way they would be of starfighter-ready copilots like the R2. The model's low cost and knowledge of general-purpose vehicles were also greatly appreciated by the resource-strapped Rebels, and soon the droids' conical heads were familiar sights in Alliance bases and Mon Calamari hangar bays. A few R4s, equipped with non-standard magnetic fault sensors, were used by the Galactic Empire to detect flaws and weaknesses in the atmospheric containment fields in hangar bays on board both Death Stars and on Star Destroyers.
- LEGO Star Wars: The Video Game
- LEGO Star Wars: The Complete Saga
- LEGO Star Wars: The Yoda Chronicles video game
- LEGO Star Wars: Revenge of the Brick
- Star Wars: Visions of the Blade
- Star Wars: The Force Unleashed video game
- † Tag & Bink Are Dead
- "Ghosts of Hoth" — Star Wars Tales 17
- "Skreej" — Star Wars Tales 10