MIT engineers have developed a hybrid propulsion system that combines the raw push of chemical thrusters with the fuel efficiency of electric propulsion — a pairing that could change what small satellites are capable of in orbit.

The system is designed for CubeSats and other small satellites roughly the size of a briefcase, a class of spacecraft that has grown rapidly in commercial and scientific deployment but has long been constrained by the limitations of single-mode propulsion.

Two propulsion modes, one system

Conventional chemical thrusters generate high thrust quickly by combusting or decomposing a propellant, making them suited for rapid orbital changes. Electric thrusters — such as ion or Hall-effect engines — expel ionized propellant at high velocity using electromagnetic fields, consuming far less fuel per unit of thrust but producing much lower force levels.

The MIT system, according to researchers, operates across both regimes from a shared propellant supply. When a fast orbital maneuver is needed — dodging debris or executing a rapid repositioning — the system draws on its chemical mode. For slower, fine-grained adjustments such as station-keeping or formation flying, it switches to electric mode to conserve propellant.

The ability to switch between modes without carrying two separate propellant tanks is the core engineering challenge the team addressed. Fitting that capability into a volume suitable for small satellites makes the design particularly constrained.

Why propulsion is a bottleneck for small satellites

Small satellites in low Earth orbit face a specific set of orbital mechanics problems. Atmospheric drag at altitudes below roughly 600 km (373 miles) is sufficient to decay an orbit within months or years without periodic re-boost burns. Simultaneously, precision formation flying — required for distributed sensing or synthetic aperture radar arrays — demands fine thrust control that chemical systems struggle to deliver cleanly.

Until now, operators have generally had to choose one capability or the other, or accept the mass and complexity of carrying two separate propulsion subsystems. For a spacecraft that may weigh only a few kilograms, that tradeoff has real consequences for mission design.

Research into restartable solid rocket motor concepts represents a parallel line of inquiry into more flexible small-spacecraft propulsion, though that work focuses on solid-propellant systems rather than the liquid or electrospray approaches more common in CubeSat platforms.

Testing and technical parameters

MIT’s team is currently conducting ground-based testing of the prototype. The researchers have not yet published full specific impulse figures or thrust measurements for each mode in publicly available documentation at this stage, but the project is framed around demonstrating that a single-propellant architecture can support the impulse requirements of both operational regimes.

Specific impulse — a measure of propellant efficiency analogous to fuel economy in a car, expressed in seconds — is the central tradeoff being managed. Chemical thrusters typically achieve specific impulse values in the range of 150–300 seconds. Electric thrusters can reach 1,000–3,000 seconds or higher, depending on the design. A hybrid system necessarily operates at intermediate values in chemical mode, meaning the efficiency gains in electric mode must offset propellant spent during high-thrust burns.

The propellant selection also matters for safety and handling at launch. Many small satellite operators prefer non-toxic, storable propellants that do not require special handling on the launch pad — a constraint that narrows the chemical options available to the system designers.

Implications for small satellite mission design

If the propulsion architecture proves out in orbit, it could make small satellites viable for mission profiles currently reserved for larger, more expensive spacecraft. Rapid debris avoidance, responsive repositioning over a target area, and long-duration formation maintenance are all maneuver types that require the kind of thrust flexibility the MIT system aims to provide.

The commercial small satellite sector has been growing in part because launch costs have dropped, but propulsion constraints have kept mission ambition in check. A propulsion system that removes that bottleneck without adding prohibitive mass or complexity would expand the design space considerably.

Materials durability in the space environment is a separate engineering variable — work such as Georgia Tech’s ISS-based testing of space-resilient satellite polymers reflects how much engineering attention goes into ensuring small spacecraft components survive long enough to justify the maneuverability the propulsion system enables.

The MIT team has not announced a target launch date for an orbital demonstration, and the system remains at the ground-testing phase. Moving from a laboratory prototype to a flight-qualified unit that can survive launch vibration, thermal cycling, and the vacuum of low Earth orbit is a development path that typically spans several years for propulsion hardware.