Bengaluru, India: Indian space startup EtherealX is advancing an ambitious plan to develop a fully reusable medium-lift rocket, with newly disclosed details about its Pegasus upper-stage engine offering a glimpse into the technology behind the company’s long-term launch ambitions.

The startup is developing the Razor Crest Mk-1, a 71-metre launch vehicle designed to recover both its booster and upper stage. If the architecture performs as intended, it would represent a major step beyond the partial reusability used by many existing launch systems. EtherealX itself describes Razor Crest as a fully reusable medium-lift vehicle.

Pegasus Engine at the Center of the Design

One of the most notable elements of the program is the Pegasus upper-stage engine.

EtherealX has described Pegasus as an 80-kilonewton engine, with a reported chamber pressure of around 100 bar and a vacuum specific impulse of approximately 323 seconds. The engine is designed to use liquid oxygen and RP-1, a kerosene-based rocket propellant.

The company is pursuing an unusual propulsion architecture called the Full Flow Segregated Cooling Cycle, or FSCC.

Rather than relying on a conventional preburner arrangement, EtherealX’s concept uses regenerative cooling and the thermal energy generated by the engine as part of its propulsion system.

Turning Heat Into a Resource

The central idea behind the design is to make better use of heat generated during operation.

Rocket engines normally have to manage extremely high temperatures to prevent damage to their combustion chambers and other components. Regenerative cooling systems circulate propellant through channels around hot engine components, transferring heat away before the propellant enters the combustion process.

EtherealX’s FSCC concept seeks to push this principle further by using heated propellant as part of the turbomachinery process.

The approach is technically ambitious, and its practical performance will ultimately depend on testing and flight validation.

A Different Approach to Upper-Stage Reuse

Recovering an upper stage is considerably more challenging than recovering a first-stage booster.

An upper stage reaches orbital velocity and subsequently has to survive atmospheric re-entry before returning for another mission. The extreme thermal environment is therefore one of the biggest obstacles to repeated reuse.

EtherealX’s concept aims to reduce the amount of dedicated thermal-protection hardware required by integrating thermal management more deeply into the propulsion architecture.

According to the company’s design concept, heat encountered during atmospheric return could be managed through the vehicle’s cooling system and used as part of the energy available for a controlled braking maneuver.

If successfully demonstrated, such an approach could reduce the amount of hardware that has to be carried solely for thermal protection.

Razor Crest Mk-1 Targets Two-Stage Recovery

The company’s flagship vehicle is designed around a more ambitious form of reusability.

Razor Crest Mk-1 is planned to use nine Stallion engines on its booster and 15 Pegasus engines on its upper stage. The vehicle is being developed in expendable, partially reusable and fully reusable configurations.

In the fully reusable configuration, the company has indicated a payload capacity of roughly 8 tonnes to low Earth orbit, compared with a substantially higher capacity when the vehicle is not required to recover both stages.

That trade-off illustrates a central challenge of reusable launch systems: recovering hardware generally requires additional mass, fuel and complex flight operations.

Commercial Interest Before First Flight

EtherealX has attracted significant commercial interest despite remaining in the development and testing phase.

The company has reported approximately $130 million in launch agreements or memoranda, involving customers including Japan’s Space BD and Taiwan’s space agency, TASA. These agreements were secured before the company’s first orbital launch.

The company has also raised substantial venture funding to advance engine qualification, testing infrastructure and vehicle development.

Current reporting indicates that EtherealX’s first technology demonstration flight is planned for 2027, while the full-scale Razor Crest Mk-1 is targeted for a later flight program.

Testing Will Be the Critical Test

Despite the impressive specifications, none of the vehicle’s most ambitious capabilities can be considered operational until they have been demonstrated through rigorous testing and flight.

Engine performance must be verified under increasingly demanding conditions. The company must also demonstrate reliable stage separation, guidance, re-entry, thermal management, landing and refurbishment.

The upper-stage recovery concept will be particularly challenging because it combines orbital flight with atmospheric return and controlled propulsion.

India’s Private Space Sector Expands

EtherealX is part of a broader expansion of India’s private space industry.

Indian startups are increasingly developing launch vehicles, propulsion systems, satellite technologies and other space infrastructure. The country’s regulatory reforms and growing commercial space market have created new opportunities for private companies to develop technologies that were historically dominated by government organizations.

EtherealX’s focus on reusable launch systems places it among the companies attempting to address one of the biggest challenges in the global space economy: reducing the cost and increasing the frequency of access to orbit.

Aiming for a New Reusability Model

The company’s long-term vision goes beyond simply recovering a booster.

SpaceX’s Falcon 9 has demonstrated the commercial value of first-stage reuse, but its conventional missions generally expend the upper stage. EtherealX is attempting to design a system in which both major stages can return for future missions.

That ambition could potentially reduce manufacturing requirements and improve launch cadence if the system proves reliable.

However, achieving full two-stage reuse remains an extremely demanding engineering problem.

Conclusion

EtherealX’s latest propulsion disclosures highlight an unconventional attempt to make full rocket reusability more practical.

The Pegasus engine, FSCC architecture and proposed thermal-management system are designed around the idea of turning some of the heat associated with atmospheric return from a problem into a useful part of the vehicle’s energy system.

The concept remains under development, and its ultimate significance will depend on testing and successful flight demonstrations. But with a planned two-stage reusable architecture, substantial commercial interest and a growing Indian private-space ecosystem behind it, EtherealX is positioning the Razor Crest Mk-1 as an ambitious contender in the next generation of reusable launch vehicles.