NASA is again considering whether to launch a public competition to develop large stratospheric airships, a capability that has eluded the US military despite several costly attempts.

The agency is currently gauging interest in such a challenge and seeking feedback on a list of rules for the potentially three-year competition.

The proposed list calls for interested teams to first develop a “tier 1” airship that can lift a 20kg (44lb) payload to 65,000ft, hold within a 20km radius while under control for at least 20h and successfully return the payload to the ground. The rules note that the airship itself is not required to return, allowing designers to use expendable vehicles with recoverable payloads.

Successful designs are eligible to claim up to $1 million in prize money during the first phase. But the ultimate goal is to scale up the technology for the tier 2 competition. Instead of a 20kg payload, NASA wants a designer to loft a 200kg payload into the stratosphere for 200h, or more than eight days.

If a team succeeds at the tier 1 requirement, NASA’s challenge would have achieved a technological breakthrough. Weather balloons are now able to ascend to stratospheric altitude, but they lack powered controls to remain on station. In the last decade, the US military funded development of two stratospheric airship projects ­– Lockheed Martin’s high altitude airship and the integrated sensor is structure (ISIS) airship – but neither proved successful.

NASA first floated the idea of a stratospheric airship challenge in 2014. The agency had commissioned a study by the Keck Institute, which showed strong interest from the academic community in using stratospheric airships for scientific experiments and astronomical observation.

The agency also sees commercial interest in the technology. Google, for example, is developing Project Loon, which is aimed at providing regional telecommunications. Google’s concept launches thousands of networked weather balloons into the air. Although they are unpowered, the balloons are able to remain on station by using wind currents at different altitudes to keep them from drifting. According to NASA officials, Google has expressed interest in acquiring any designs that meet the agency’s tier 2 requirements.

NASA has been flirting with such a proposal for several years, as part of the agency’s public challenge to develop airships that can remain at 65,000ft for long periods, serving as scientific laboratories or providing commercial services at far less expense than satellites and longer duration than heavier-than-air vehicles.