Inertial Upper Stage
Solid-fueled upper stage for Titan and Shuttle missions.
The Inertial Upper Stage (IUS) was a two-stage, solid-fueled space launch system developed by Boeing for the United States Air Force beginning in 1976. Originally designated the Interim Upper Stage, it was used to raise payloads from low Earth orbit to higher orbits or interplanetary trajectories. The IUS could be launched aboard a Titan 34D or Titan IV rocket as an upper stage, or from the payload bay of the Space Shuttle as a space tug.
Quick Facts
- Manufacturer
- Boeing; United Technologies
- Country-origin
- United States
- Rockets
- Space Shuttle
- Titan 34D
- Titan IV
- Derivatives
- TOS
- Height
- 5.2 m / 17 ft 1 in
- Diameter
- 2.8 m / 9 ft 2 in
- Mass
- 14,700 kg / 32,408 lb
- Launches
- 24
Facts from the source article.
Did You Know?
- The solid rocket motor on both stages had a steerable nozzle for thrust vectoring.
- The second stage had hydrazine reaction control jets for attitude control while coasting and for separation from payload.
- Depending on mission, one, two or three 120 lb tanks of hydrazine could be fitted.
Development
Candidates included the liquid-hydrogen/liquid-oxygen Centaur, the hypergolic-propellant Transtage, and the solid-propellant Interim Upper Stage. Development proceeded on both Centaur and IUS, and a second stage was added to the IUS design, usable as an apogee kick motor for direct geostationary insertion or to increase payload mass to escape velocity. Boeing was the primary contractor, and United Technologies' Chemical Systems Division built the solid rocket motors. The first IUS launch occurred in 1982 on a Titan 34D shortly before the STS-6 Shuttle mission. Development of Shuttle-Centaur halted after the Challenger disaster, and the Interim Upper Stage became the Inertial Upper Stage.
Applications
On Titan launches, the booster placed the IUS and payload into low Earth orbit, where the IUS separated and ignited its first stage to enter an elliptical transfer orbit. On Shuttle launches, the orbiter's payload bay opened, the IUS and payload were raised to a 50-52° angle and released; after the Shuttle moved to a safe distance, the first stage ignited for a transfer orbit. At apogee, the first stage and interstage structure were jettisoned, and the second stage fired to circularize the orbit, then released the satellite and performed a retrograde maneuver to avoid collision. For planetary missions, the second stage ignited immediately after first-stage burnout at low altitude to provide extra velocity for Earth escape. The IUS could not impart as much velocity as Centaur would have: for example, Centaur could have launched Galileo directly on a two-year trip to Jupiter, while the IUS required a six-year voyage with multiple gravity assists. The final IUS flight occurred in February 2004.
More in Space Shuttle Program
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced