The US Army's Aviation Applied Technology Directorate is asking industry to submit proposals for a research and development effort called the Alternative Engine Conceptual Design and Analysis.
The research project would set the foundations for a future Alternative Concept Engine programme, which could potentially power next-generation aircraft developed as part of the service's Future Vertical Lift (FVL) programme.
The army says it has not set the requirements for the FVL family of systems, but that whatever aircraft emerges from the development effort will have hover, speed, range, payload and fuel efficiency characteristics "beyond any current rotorcraft". Those requirements might call for FVL aircraft to hover at 10,000ft (3,050m) and cruise at altitudes of 30,000ft.
"With such a wide array of missions under consideration for future rotorcraft, a robust, innovative propulsion system design is necessary to meet these versatile, wide operating range requirements," the army solicitation reads. "Moreover, a significant technological advancement in engine/power systems is envisioned to affordably provide the needed performance capability of FVL platforms."
The army is also looking at what kind of propulsion systems a future unmanned aircraft might need. "It is anticipated that future [unmanned aircraft] platforms will require alternative, advanced engine/power system configurations that enable enhanced mission capability, such as improved time on station, increased mission radius and quieter operation," the service says.
The army says it recognises that different technologies or configurations may be needed for a given engine size class. Therefore it will study configurations ranging in output from 40shp (29kW) to 10,000shp. The service, in its solicitation, says that there are many potential avenues to explore, including variable speed power turbines and other technologies.
Bidders should provide a detailed technology maturation plan for their conceptual designs in support of the army's plan to start a demonstration programme in fiscal year 2017.
The army says it intends to award at least one $1.2 million contract, but could bestow up to four. It expects all work to be completed within 18 months.