New Andromeda Engine Introduced by Stoke Space
Fully Reusable Upper Stage Motor Features Design Upgrades
The next iteration of the Stoke Space Andromeda engine has been announced by the company. Built on lessons from earlier variants, Andromeda’s new design (called Andromeda2) brings major improvements to performance, simplicity, and rapid reusability, the company says.
Stoke says it has created a system that can not only robustly survive the environments of orbital reentry by integrating a metal heat shield with the engine, and by actively cooling it with liquid hydrogen. The design means it can be ready to fly again immediately without inspection or refurbishment, according to information provided by the company.
The number of thrusters on Andromeda2 has been reduced from 30 to 24, their individual size has been increased. Simplified flow circuits reduce the number of parts and save weight without compromising thrust precision or thrust vector control. The thruster injector design has also been improved, which now delivers better performance and further improves engine efficiency
Andromeda2’s thruster nozzles are now designed to operate in two different modes: one in the vacuum of space and one inside the atmosphere. The vacuum nozzle produces a high expansion ratio for improved performance in space, and the sea-level nozzle is designed to produce stable plume expansion inside the pressure of the atmosphere during propulsive landing maneuvers.
The second-stage base heat shield serves not just as armor, but as an integral part of the Andromeda engine. By applying regenerative cooling—a technology proven to work for rocket engine chambers in which the thermal environment is about 20 times more intense—Stoke says it has created a heat shield that can readily handle atmospheric reentry and be ready for the next flight without refurbishment.
While these fundamentals remain unchanged, the new design features a different form factor. Andromeda2’s base shape returns to one of the earliest concepts, featuring a continuously curved contour across the entire base of the vehicle, and the thruster nozzles fully embedded along the outer circumference. This geometry reduces weight compared to Andromeda1, increases downmass capacity, and together with the new thruster nozzles, enables a more definitive qualification program in which thruster ignition and operation in vacuum conditions can be evaluated at ground test facilities. This mitigates a big risk ahead of the first orbital launch.
There has also been a concerted effort put into the stage-to-stage interface. The result ties Andromeda’s heat shield to Stage 1 during ascent and effectively eliminates the need for the interstage volume (and mass) that accommodates the large bell nozzles on typical upper-stage engines. When fixed to Stage 1 during ascent, Andromeda’s thrusters are positioned outboard of the Stage 1 outer diameter. This allows Andromeda to ignite while still attached to the first stage without causing damage to the base of Stage 2, and without the need for a heavy one-time-use interstage shield to protect Stage 1. This “hot staging” operation reduces gravity losses from the flight profile, eliminates the need for stage separation pushers, and overall significantly improves Nova’s mass capacity to orbit.