EtherealX Pushes Indian Rocket Reusability With Novel Engine Cycle

Bengaluru-based space startup EtherealX is advancing an unconventional rocket-engine architecture as it works toward building a launch vehicle in which both the booster and upper stage can eventually be recovered and reused.

At the centre of the programme is the company’s proprietary Full-flow Segregated Cooling Cycle, or FSCC, being developed for the upper stage of its Razor Crest Mk-1 medium-lift launch vehicle. The architecture is intended to address one of the hardest problems in reusable upper stages: managing the extreme thermal loads encountered when a stage returns through the atmosphere.

Instead of treating the engine only as a propulsion system, EtherealX is designing the propulsion and thermal-management systems to work together. Propellants circulating through the engine can absorb heat and transfer energy through the system while also supporting the turbomachinery. The company believes this approach can reduce the additional thermal-protection mass normally associated with bringing an orbital upper stage back through the atmosphere.

The engine associated with the upper-stage programme is Pegasus. EtherealX has previously demonstrated test-ready thrust-chamber hardware and has also developed its own turbopump technology. The production engine is being designed around an approximately 80-kN dual-thrust-chamber configuration using the company’s FSCC architecture.

The next major milestone will be hardware validation. EtherealX is targeting the first hot-fire of the engine around November 2026. Until that test is completed, FSCC remains an ambitious propulsion concept rather than a flight-proven engine cycle. A successful firing would therefore represent an important step toward demonstrating that the architecture works under real operating pressures, temperatures and propellant flows.

EtherealX ultimately intends to use the technology aboard Razor Crest Mk-1, which is being designed as a fully reusable medium-lift launch vehicle. Its proposed configuration combines a reusable booster with a reusable upper stage, going beyond the partial-reuse model in which only the first stage is recovered.

The company is also developing the much larger Stallion, a roughly 1.2-meganewton semi-cryogenic booster engine, for the first stage. Earlier disclosed plans envisage nine Stallion engines on the booster and multiple Pegasus engines powering the upper stage.

The significance of the programme will ultimately depend on testing rather than design claims. Recovering an orbital upper stage places demanding requirements on propulsion, thermal protection, guidance and structural durability. The November engine firing will therefore be an important early indication of whether EtherealX’s indigenous FSCC architecture can progress from an innovative engineering concept into a practical reusable-spaceflight system.