On 12 March the Kestrel upper stage completed a full-duration hot fire at our vertical test stand. The engine ran for the complete planned burn, held chamber pressure inside its target band from ignition to shutdown, and came off the stand ready for inspection rather than repair.
Kestrel is the upper stage our Propulsion program has been building toward for three years. It is designed for demanding orbits: high-energy insertions, multiple restarts, and long coasts between burns. A full-duration test is the point where those design goals stop being numbers on a page and start being a record.
What we tested
The test article was a flight-representative stage with production tankage, avionics, and thrust vector control. The burn profile matched a typical mission to geostationary transfer orbit, including a throttle-down near the end to simulate a precise cutoff.
The team was watching three things in particular:
- Combustion stability across the full throttle range
- Thermal margins on the nozzle extension during the longest segment of the burn
- How the thrust vector control system tracked commanded steering inputs under loadAll three came back inside predicted limits. Nozzle temperatures peaked a few percent below the model, which gives us useful margin for hotter mission profiles later.
Why it matters
Our engines are tested well past their rated limits before they fly. That is not a slogan. It is how we find the problems that only appear after minutes of continuous operation, when heat soak, vibration, and propellant behavior start to interact.
A clean full-duration run tells us the core design is sound. It also means the next tests can focus on the hard edges: restarts after long cold coasts, off-nominal propellant temperatures, and deliberate fault injection.
What comes next
Kestrel now moves into flight qualification. Over the next several months the stage will go through a series of restart tests, extended coast simulations, and environmental testing at our integration facilities. The first flight unit is scheduled to begin assembly once qualification is complete.
We will share results from the restart campaign as it progresses. Confirmed.