Redwire Corporation (NYSE: RDW) has received a $20 million contract from the Defense Advanced Research Projects Agency (DARPA) to test and fly a scaled version of its SabreSat spacecraft on a precursor mission in very low Earth orbit (VLEO), the Jacksonville, Florida, company announced on November 5, 2026. The award, issued under DARPA’s Otter program, adds a second VLEO flight to Redwire’s work on the effort.
Otter aims to develop, demonstrate and collect on-orbit data for air-breathing electric propulsion, a technology intended to keep satellites at altitudes between 90 and 450 kilometers by harvesting the thin residual atmosphere as propellant rather than relying on a finite fuel load. DARPA selected Redwire as prime contractor in June 2024, then awarded it a $44 million Phase 2 contract in November 2025 to complete manufacturing and deliver the full-scale spacecraft to launch. The new award brings Redwire’s two announced Otter contracts to $64 million and sets up what the company calls a phased flight approach toward operational use.
How the DARPA Otter Precursor Flight Buys Down Program Risk
The contract funds additional testing and experimentation on a scaled SabreSat ahead of a precursor flight test. At VLEO altitudes, atmospheric drag and gravity combine to decay an orbit within short timeframes, so a spacecraft must thrust frequently to stay aloft. DARPA has acknowledged that realistic VLEO conditions are extremely difficult to reproduce in ground facilities. For that reason, Otter is structured around a long-duration “orbiting wind tunnel” demonstration lasting more than one year, paired with ground tests of thruster and inlet hardware whose data will be compared against on-orbit results.
“This flight test allows us to gather data that cannot be fully recreated on the ground, learn faster, and reduce risk for the full Otter mission,” said Spence Wise, Redwire Senior Vice President of Missions and Platforms. Wise added that the work is intended to mature propulsion and spacecraft systems for a new class of maneuverable, energy-efficient spacecraft able to sustain persistent operations in VLEO.
Several parameters remain undisclosed. Neither Redwire nor DARPA has released the dimensions of the scaled vehicle, its target altitude, its launch date or launch provider, or whether it will carry an air-breathing thruster or a conventional electric propulsion system. DARPA has also not published a flight date for the full-scale Otter spacecraft.
SabreSat Orbital Drone Design and the Air-Breathing Propulsion Challenge
As prime mission integrator, Redwire develops and integrates the spacecraft on its U.S.-built SabreSat Orbital Drone platform. Publicly available specifications indicate SabreSat accommodates a payload envelope of 100 by 80 by 40 centimeters and roughly 200 kilograms of payload mass, provides up to 5,000 watts of orbit-average power at end of life depending on orbit and configuration, operates above 150 kilometers, and is designed for a mission life of up to seven years. Propulsion is electric, with air-breathing listed as an option. Redwire markets the platform for high-resolution intelligence, surveillance and reconnaissance (ISR), resilient communications, navigation and Earth science.
The air-breathing element is the core technical risk. In April 2024, DARPA awarded Phase Four $14.9 million to deliver an air-breathing electric propulsion system for Otter based on its radio frequency thruster, which the company describes as propellant agnostic and therefore tolerant of ingested atmospheric gases that degrade conventional electric thrusters. The system must capture sparse free-molecular flow through an inlet, ionize it and accelerate it fast enough to offset drag continuously.
Otter sits within a broader Redwire VLEO portfolio. The company is prime contractor for ESA’s Skimsat mission, built on its European Phantom platform developed in Belgium, with Thales Alenia Space in the United Kingdom selected to supply the electric propulsion subsystem. Phantom is a separate design with a total mass of up to 300 kilograms, rated for up to five years in VLEO and lacking air-breathing capability. Redwire also performs digital engineering work for DeepSat’s planned VLEO constellation.
Analysis: A second flight signals that DARPA prefers incremental on-orbit risk reduction over a single all-or-nothing demonstration for a propulsion concept that ground facilities cannot fully validate. The operational case for VLEO is clear on paper: sensors closer to targets, shorter revisit, lower latency, and an orbital layer above airborne anti-access threats yet below increasingly congested LEO shells. Every one of those advantages, however, depends on whether air-breathing thrust can match drag over long durations. Until Otter returns flight data, sustained VLEO operations remain a projection rather than a capability, and the $64 million committed to date is best read as a structured bet on retiring that single question.
The next milestones are delivery of the full-scale Otter spacecraft to launch under the Phase 2 contract, execution of the precursor flight, and the start of the planned year-long orbiting wind tunnel campaign. Flight sequencing, launch dates and the propulsion configuration of the scaled vehicle remain the open variables to watch.
