DRDO Seeks Indigenous Air-Breathing Electric Propulsion for Satellites in Very Low Earth Orbit

The Defence Research and Development Organisation has issued a Request for Proposal under its Technology Development Fund for an indigenous air-breathing, space-based electric propulsion system meant to keep satellites aloft in Very Low Earth Orbit — an altitude band so thin on atmosphere, and so thick with drag, that ordinary satellites cannot survive there for long without being constantly pushed back up.

What DRDO Is Actually Asking For

The specification is unusually precise for an early-stage RfP. The system must operate between 180 and 230 kilometres altitude, sustain a thrust of 12 to 25 millinewtons, and do it all on a power budget under 1,500 watts while weighing less than 40 kilograms. It has to keep working for a mission duration of three years, and at least 75 percent of its content must be indigenous — a threshold well above what most Indian space hardware programmes have historically required at this stage. DRDO has indicated a preference for a Hall-effect thruster configuration, a mature but still nontrivial electric propulsion architecture, and — the genuinely difficult part — the propellant is meant to be a dual-source mix of ambient atmospheric air and xenon rather than xenon alone.

That combination is the whole point of "air-breathing" propulsion. A conventional electric thruster carries its propellant gas onboard in a tank that eventually runs out, which is exactly what limits how long a satellite can fight atmospheric drag at very low altitudes. An air-breathing thruster instead scoops up the trace amounts of atmosphere still present at 180-230 km, ionises it, and uses it as propellant, in principle allowing a satellite to stay in VLEO indefinitely rather than for as long as its tank lasts.

Why Very Low Earth Orbit Is Worth the Trouble

VLEO sits below the altitudes where most Earth-observation and communication satellites operate. Flying there brings a satellite's sensors much closer to the ground, which translates directly into sharper imagery and lower-latency links without changing the sensor itself — the same logic that makes a longer camera lens less necessary when you can simply stand closer to the subject. The trade-off is atmospheric drag intense enough that an unpowered satellite would deorbit within weeks or months rather than years. Solving the propulsion problem is therefore the precondition for using the orbit at all, which is why DARPA has been pursuing a near-identical capability in the United States — funding contractor Phase Four roughly $14.9 million for a comparable air-breathing electric propulsion system, and separately backing Redwire's Otter satellite for the same purpose. DRDO's RfP places India in direct pursuit of the same still-unproven capability.

Strategic Framing

DRDO has tied the programme explicitly to reducing dependence on foreign propulsion suppliers, and to enabling long-duration surveillance, communication and scientific missions that would otherwise require frequent orbit-raising manoeuvres or shorter mission lifetimes. The 75 percent indigenous-content floor mirrors a pattern visible across several of DRDO's other 2026 initiatives — including its opening of TAPAS drone technologies to private industry and its wider push to transfer conventional missile technology out of government labs — of setting local-content requirements high enough to force genuine domestic supply chains rather than assembly-and-badge arrangements.

If it works, the propulsion system would be a building block rather than a satellite in itself: the kind of component DRDO could hand off to ISRO, NewSpace India Limited, or a private satellite manufacturer for integration into an actual VLEO mission, in much the same way it has been transferring completed missile and radar technologies to industry over the past year.

What Happens Next

An RfP is a request for proposals, not a contract award — DRDO is asking industry and research partners to demonstrate they can meet the specification, not confirming that anyone yet has. No timeline for down-selection or a demonstration mission has been disclosed. Given how tightly specified the requirements are — down to the exact thrust band and power ceiling — the program appears to be past the conceptual stage internally, even if the public RfP process is only now beginning. Whichever combination of thruster design, power system and propellant-intake mechanism DRDO eventually selects will be one of the more closely watched space-propulsion programmes to come out of Indian defence R&D this year, if only because almost no country has yet made air-breathing electric propulsion work reliably outside a lab.

The Hard Engineering Problem Hiding Inside the Spec

Air-breathing electric propulsion sounds simple in concept — collect the thin atmosphere at very low altitude and use it as propellant instead of carrying a tank — but every part of that sentence is difficult in practice. The intake has to collect gas from an atmosphere so rarefied that "air" at 200 km is really a handful of molecules per cubic centimetre, moving past the spacecraft at orbital velocity rather than sitting still to be scooped up. That gas then has to be compressed, ionised and accelerated by a Hall-effect thruster designed and calibrated for a very different, denser propellant like xenon, without simply choking the intake or destabilising the plasma discharge the thruster depends on. DRDO's own specification, by asking for a dual-source design that can run on xenon as well as ambient air, hints at how unproven the pure air-breathing mode still is: a xenon backup gives the satellite a way to maintain orbit even if the atmospheric intake underperforms, rather than betting the entire three-year mission life on a mechanism nobody has flown operationally.

How This Compares Internationally

DRDO's approach mirrors, almost specification-for-specification, what the United States has been funding through DARPA's Otter programme, where contractor Phase Four received a $14.9 million award to build a comparable system and Redwire was separately tapped to build the satellite bus around it. The European Space Agency has also funded air-breathing electric propulsion research for years without yet flying an operational mission using it. That DRDO is entering the field at roughly the same technological maturity as these programmes — rather than years behind, as has often been the case in space propulsion — suggests VLEO is one of the few genuinely open technology races left in satellite propulsion, with no country yet holding a large operational lead.

What Success Would Actually Enable

If DRDO's programme succeeds, the immediate beneficiary is not likely to be a single flagship satellite but a new category of persistent, close-range Earth observation and signals-intelligence platforms that India's defence and civilian space establishment could deploy without the orbital decay problem that has kept most satellites well above 300 km. A working air-breathing thruster removes the single biggest obstacle to operating there long-term, which is why DRDO's Technology Development Fund — the same mechanism it has used to open up drone technologies and conventional missile systems to private industry — is treating this as foundational infrastructure rather than a one-off research exercise.

Sources

• DRDO Issues RfP For Indigenous Air Breathing Space-Based Electric Propulsion In VLEO | Indian Defence News
• DRDO Seeks Air-Breathing Propulsion for VLEO Satellites - idrw.org
• Exclusive: Phase Four Secures a $14.9M DARPA Contract for an Air-Breathing VLEO System - Payload Space