DRDO Moves to Develop Air-Breathing Electric Propulsion for Long-Endurance VLEO Satellites
DRDO is pushing into one of the most challenging areas of space propulsion: keeping satellites operational just above Earth’s atmosphere. A new RFP seeks an indigenous air-breathing electric propulsion system that could reshape the future of VLEO satellites.
DEFENCE NEWS
The Defence Research and Development Organisation (DRDO) has issued a Request for Proposal (RFP) for the development of an indigenous Air-Breathing Space-Based Electric Propulsion System for Very Low Earth Orbit (VLEO) satellites. The project is being pursued under the Technology Development Fund (TDF) and is aimed at developing an advanced propulsion capability for spacecraft operating much closer to Earth than conventional low-Earth-orbit satellites.
According to the tender, the proposed system is intended to operate between 180 km and 230 km altitude, generate 12–25 millinewtons of thrust, consume less than 1,500 watts of power, weigh below 40 kg and have an operational life of at least three years. DRDO has also specified a minimum 75% indigenous content, making the project relevant not only to space propulsion but also to the development of a domestic industrial ecosystem around advanced spacecraft technologies.
Why Operating Satellites At 180–230 km Is Difficult
Very Low Earth Orbit offers an attractive proposition for Earth-observation and other missions because a satellite operating closer to the surface can potentially achieve higher imaging resolution with a smaller or less powerful payload. Shorter distances between the spacecraft and ground can also provide advantages for communications and sensing applications.
The problem is atmospheric drag.
Although space at 180–230 km is extremely thin compared with the atmosphere at the Earth's surface, it is still dense enough to exert significant aerodynamic drag on a spacecraft. As altitude decreases, this drag becomes increasingly important. A satellite operating in this region continuously loses orbital energy and would gradually descend unless propulsion is used to compensate for the drag.
This creates a fundamental problem for conventional satellites: the spacecraft has to carry enough propellant to continuously counter atmospheric drag.
Research into VLEO spacecraft has shown that conventional electric propulsion can become increasingly demanding at these altitudes because the amount of stored propellant ultimately limits mission duration. Studies have found that air-breathing electric propulsion can become particularly attractive for long-duration missions at lower VLEO altitudes.
How Air-Breathing Electric Propulsion Works
The basic idea behind Air-Breathing Electric Propulsion (ABEP) is relatively straightforward, although implementing it is extremely difficult.
Instead of carrying all of its propellant from Earth, a spacecraft operating in VLEO collects the extremely thin atmospheric gases surrounding it. An intake captures incoming particles and directs them into the propulsion system. These particles can then be ionised and accelerated using an electric thruster to generate thrust.
In effect, the spacecraft uses the atmosphere it is flying through as its propellant source.
This changes the conventional propulsion equation. A traditional electric-propulsion spacecraft has a finite quantity of xenon or another propellant stored onboard. An air-breathing spacecraft can theoretically continue collecting atmospheric particles for propulsion as long as it remains in an appropriate orbital environment.
However, this does not mean that the spacecraft gets unlimited propulsion for free. The intake itself creates drag, while collecting, compressing, ionising and accelerating the incoming gas requires electrical power. The system therefore has to maintain a delicate balance between the drag created by the spacecraft, the efficiency of atmospheric collection and the thrust generated by the electric propulsion system.
DRDO's RFP appears to address this challenge through a system capable of using atmospheric air while also incorporating xenon as a supplementary propellant.
Why A Hall-Effect Thruster Is Significant
DRDO has indicated a preference for a Hall-effect thruster configuration for the project.
Hall-effect thrusters are a form of electric propulsion in which an electric field accelerates ionised propellant to produce thrust. They offer high exhaust velocities and comparatively high propellant efficiency, making them suitable for applications where a spacecraft needs relatively small but sustained thrust over long periods.
That characteristic is particularly relevant to VLEO.
A VLEO satellite does not necessarily require the large instantaneous thrust associated with launch vehicles or conventional rocket engines. Instead, it needs a propulsion system capable of continuously or frequently producing small amounts of thrust to compensate for aerodynamic drag and maintain its orbit.
DRDO's specified 12–25 mN thrust range therefore needs to be understood in this context. The objective is sustained orbital maintenance rather than rapid manoeuvring.
The Engineering Challenge Is Bigger Than The Thruster
Developing the thruster itself is only one part of the problem.
An operational air-breathing propulsion system needs an atmospheric intake capable of capturing sufficient particles at orbital velocity without producing excessive additional drag. The collected gas must then be transported into the propulsion system, processed and converted into a usable propellant stream.
The spacecraft also has to deal with the harsh VLEO environment.
At these altitudes, residual atmospheric particles can produce substantial aerodynamic drag and atomic oxygen can cause material degradation. The spacecraft therefore requires an aerodynamic design, appropriate surface materials and coatings, efficient power generation and thermal management in addition to the propulsion system.
Research into ABEP has identified intake efficiency, thrust-to-power ratio, spacecraft geometry, solar-array performance and low-drag materials among the major factors determining how low a spacecraft can sustainably operate.
This means DRDO's programme is effectively a systems-engineering challenge rather than simply the development of another electric engine.
DRDO's Key Requirements
The RFP sets several demanding parameters for the proposed system:
Operating altitude: 180–230 km
Thrust: 12–25 mN
Power consumption: below 1,500 W
System mass: below 40 kg
Operational life: minimum three years
Indigenous content: minimum 75%
The tender was published on 8 September 2026, with a pre-bid meeting scheduled for 15 September and bid submission scheduled to close on 5 October 2026. The contract period specified in the tender is 1,095 days.
The 75% indigenous-content requirement is particularly important. It indicates that DRDO is not simply looking for an imported propulsion architecture to be integrated into an Indian satellite. The objective is to create domestic capability across multiple elements of the system.
Building An Indian Supply Chain For Space Propulsion
A successful programme could create demand for technologies including high-performance ceramics, electrodes, cathodes, anodes, power-processing units, miniaturised electric thrusters, atmospheric intake systems and associated control electronics.
This is significant because electric propulsion is becoming increasingly important as spacecraft become smaller, missions become longer and satellite constellations expand.
DRDO's own technology-foresight material already identifies Air Breathing Electric Propulsion for Very Low Earth Orbit as an electric-propulsion technology area.
The current RFP therefore represents a move from identifying the technology requirement toward seeking an industry-developed system.
India Is Not Starting From Zero
India is entering a field that is already attracting significant international interest.
Indian space startup Bellatrix Aerospace, for example, has been developing air-breathing propulsion concepts for ultra-low-orbit spacecraft. The company has also entered into collaborations focused on VLEO satellite systems, highlighting the growing Indian interest in operating spacecraft closer to Earth.
Internationally, organisations and research groups have spent years investigating ABEP. European research programmes have examined atmospheric intakes and plasma thrusters, while missions such as ESA's GOCE and Japan's SLATS demonstrated the broader feasibility of maintaining spacecraft in unusually low orbits using electric propulsion.
The important distinction is that conventional electric propulsion still carries its propellant. ABEP attempts to eliminate or dramatically reduce that constraint by sourcing propellant directly from the surrounding atmosphere.
Why VLEO Could Matter For Defence
For defence applications, the attraction of VLEO is particularly strong.
A satellite operating significantly closer to Earth can potentially achieve higher-resolution observation with a smaller optical system than a comparable satellite operating at a higher altitude. Lower orbital altitude can also reduce signal propagation distance, potentially benefiting certain communications and sensing applications.
For intelligence, surveillance and reconnaissance missions, long-endurance VLEO spacecraft could therefore become an attractive complement to conventional Earth-observation satellites.
The challenge has always been endurance.
Without an efficient method of continuously compensating atmospheric drag, operating at 180–230 km is difficult to sustain. An indigenous air-breathing propulsion system could potentially remove one of the biggest constraints on such spacecraft.
However, it is important not to interpret the current RFP as confirmation of a future operational military satellite. The programme is still at the technology-development stage, and significant engineering, ground testing and eventually flight validation would be required before the capability could be considered operational.
A Potential New Class Of Indian Spacecraft
The significance of DRDO's programme extends beyond the propulsion unit itself.
If the technology reaches the required performance levels, it could enable a new class of Indian spacecraft designed specifically around VLEO operations. Such spacecraft could combine aerodynamic optimisation, high-efficiency solar power, advanced materials, compact sensors and air-breathing electric propulsion to remain operational at altitudes that are difficult for conventional satellites.
The long-term objective would not simply be to build a more efficient satellite engine. It would be to make persistent operation in an orbital regime previously constrained by atmospheric drag more practical.
For India, the programme also fits into a broader shift toward indigenous development of advanced space technologies involving government laboratories, established aerospace companies, startups and research institutions.
DRDO's RFP is therefore significant not because India has already fielded an air-breathing satellite propulsion system, but because it is now seeking an industry-developed indigenous solution for one of the most technically demanding areas of spacecraft propulsion.
If successful, the technology could give India another tool for developing long-endurance VLEO platforms for Earth observation, communications, scientific missions and potentially defence applications.