Isar Aerospace's LOX/propane regeneratively-cooled rocket engine family powering the Spectrum launch vehicle first and second stages.
Aquila Engine
Isar Aerospace's LOX/propane regeneratively-cooled rocket engine family powering the Spectrum launch vehicle first and second stages.
Description
Aquila is Isar Aerospace's proprietary rocket engine, developed in-house at the company's Munich facility. The engine burns LOX/propane (LPG) using a regenerative cooling cycle and turbopump-fed propellant delivery. Propane was selected as the fuel for several advantages over kerosene: cleaner combustion with less soot formation (important for engine reuse and turbomachinery), slightly higher specific impulse, and wider availability.
The Aquila engine family includes the sea-level variant (nine engines cluster the Spectrum first stage) and a vacuum-optimized variant (single engine for the Spectrum second stage). Each sea-level Aquila engine produces approximately 25 kN of thrust. The engines are manufactured at Isar's Munich facility and tested at Kiruna, Sweden (suborbital test stand).
Isar conducted a successful full-duration static fire test of the complete Spectrum first stage (9 Aquila engines) in 2024, validating the propulsion cluster ahead of an inaugural orbital launch from Andøya Space Center, Norway. The Aquila engine architecture is designed with future reusability in mind, although Spectrum's first flights will be expendable.
Specifications
| Propellants | LOX/Propane (LPG) |
|---|---|
| Thrust (sea-level) | ~25 kN per engine |
| Configuration | 9× (first stage), 1× vacuum variant (second stage) |
| Cooling | Regenerative |
| Propellant feed | Turbopump-fed |
| Test milestone | 9-engine cluster static fire (2024) |
| Launch vehicle | Spectrum (Isar Aerospace) |
