DRDO's Air-Breathing Electric Propulsion: India's Bid for Indigenous VLEO Satellite Technology

Background

Satellites are conventionally parked in Low Earth Orbit (LEO, roughly 300-2,000 km) because lower altitudes offer better resolution but come at a cost: residual atmospheric molecules exert drag, pulling a satellite down and burning up its orbit within days or weeks unless it is repeatedly reboosted. This is why Very Low Earth Orbit (VLEO), broadly below 450 km and sometimes classified below 300 km, has stayed largely unexploited despite its obvious payoff of sharper imaging and lower signal latency. Reboosting with conventional chemical thrusters is propellant-hungry and shortens a mission's usable life drastically, which is precisely the bottleneck that air-breathing electric propulsion (ABEP) is designed to remove.

ABEP works by ingesting the thin residual atmosphere at these extreme altitudes, ionising it, and expelling it as thrust, in effect turning the very drag that threatens the satellite into its own fuel source. It is a genuinely frontier technology, with only a handful of agencies worldwide, including the US DARPA-backed Otter programme with Redwire Space, actively developing it.

Recent Development — and Why It Matters for UPSC

DRDO has issued a Request for Proposal under its Technology Development Fund (TDF) scheme seeking an indigenous Air-Breathing Space-Based Electric Propulsion system for VLEO operations. The specifications are unusually concrete for a defence R&D solicitation: the system must function at orbital altitudes of 180-230 km, sustain thrust levels of 12-25 mN, and preferably use a Hall-effect thruster configuration, a design already proven in conventional electric propulsion but now being adapted to run on scooped-in atmospheric gas rather than stored propellant. The stated objective is to cut India's dependence on foreign propulsion suppliers while enabling long-duration surveillance, communication, and scientific missions from an orbital band that offers reduced latency and higher-resolution imaging at a fraction of the cost of traditional higher-altitude constellations.

This is exam-relevant on three counts. First, it is a live example of the government's push to indigenise critical and emerging defence technologies rather than import them, a recurring Prelims and Mains theme. Second, it gives aspirants a concrete, testable data set, altitude range, thrust range, thruster type, funding vehicle, that examiners like to convert into factual MCQs. Third, it sits at the intersection of two GS themes, space technology and defence self-reliance, that the UPSC has repeatedly tested together in recent years.

Historical Parallel

The current push echoes India's cryogenic engine story from the early 1990s. When the United States pressured Russia's Glavkosmos to withhold cryogenic upper-stage technology from India in 1992-93, citing missile technology control concerns, ISRO had no choice but to develop cryogenic propulsion indigenously. That effort eventually matured into the CE-20 engine that now powers the GSLV Mark III. The lesson repeats itself here: external technology denial or unavailability has historically pushed India's space and defence establishment toward sustained indigenous R&D, and the DRDO's current ABEP solicitation follows the same template, this time proactively rather than under external pressure.

Links to the GS Syllabus

Under GS Paper III, this development feeds directly into Science and Technology, developments and their applications in everyday life, achievements of Indians in science and technology, and the indigenisation of technology. It also connects to the broader Defence and Security portfolio, since the Technology Development Fund is a DRDO instrument specifically meant to draw private industry and MSMEs into defence R&D. Under GS Paper II, it ties into government policies for self-reliance in defence production, part of the wider Atmanirbhar Bharat framework being applied across strategic sectors.