| Abbreviation | Definition |
|---|---|
| UR | User Room |
| URA | Uniformly Redundant Array |
| URA | Urine Receptacle Assembly |
| URAP | UARS Reference Atmosphere Project |
| URN | URiNe |
| URSA | Universal Radiation Spectrum Analyzer |
| URT | UpRighT |
| URV | Ultimate Robotic Vehicle |
| US | Ultimate Service |
| US | Upper Stage |
| US | Upravlayemyi Sputnik |
| USA | Ultra Simplified Acquisition |
| USA | United Space Alliance |
| USA | Upper Stage Adapter |
| USB | Unified S-Band |
| U-SB | Unified S-Band |
| USBE | Unified S-Band Equipment |
| USBI | United Space Boosters, Inc. |
| USBS | Unified S-Band System |
| USE | User Support Equipment |