Ikar (rocket stage)
The Ikar was a Russian rocket upper stage introduced by TsSKB Progress in 1999 for use with its Soyuz-U rocket. It was derived from the propulsion module which had been used successfully on more than 30 Yantar reconnaissance satellites, leveraging existing equipment and subsystems to minimize new development. Modifications were limited to updates in command and control systems and adjustments to mechanical and electrical interfaces with payloads.Soyuz-U / Ikar" />
Weighing, the Ikar was situated beneath the payload fairing. It featured an in-flight restart capability of up to 50 times, enabling the deployment of multiple satellites into different orbits. The stage could operate autonomously or be controlled from the ground. It was powered by S5.144 engine, delivering a vacuum thrust of, supported by 16 vernier thrusters for precise flight control. The propulsion system used unsymmetrical dimethylhydrazine fuel and dinitrogen tetroxide as its oxidizer.
The Ikar could deliver payloads of to orbits between in altitude. While its performance was lower than that of the competing Fregat upper stage, the Ikar offered more precise maneuvering capabilities and a longer autonomous operation time.
The Ikar was used in six launches in 1999, each carrying four GlobalStar satellites. It was replaced by the improved Volga upper stage, which remains in use on the Soyuz-2 rocket.