The Deployable Extra-Vehicular Activity Platform (DEVAP) is a staging platform for egress and ingress attached to a lunar, Mars, or planetary surface habitat airlock, suitlock, or port. The DEVAP folds up into a compact package for transport, and deploys manually from its attached location to provide a ramp and staging platform for extravehicular activities (see figure).

Photo of DEVAP system.
Habitat pressure vessels are generally designed to be as structurally efficient as possible to save mass by conforming to curvatures and contours that optimize the tensile strength of the material making up the primary structure wall. Whenever a port or penetration is needed in the wall of the pressure vessel, the location is dictated by the areas of least tensile strain, and in such a way that allows the port to be constructed most efficiently with minimal mass penalty. Ingress/egress ports tend to be higher up on the side of the volume, rather than close to the ground where it would be convenient for suited crewmembers to step out onto the planetary surface. A platform, stair, and/or ramp structure is needed to allow crewmembers to descend from the high location of the egress/ingress port down to the planetary surface. The egress structure must be portable, of minimal mass, easy to transport and deploy, and adjustable to variations in the natural terrain.

The DEVAP consists of a fixed mounting frame that remains permanently attached to the ingress/egress port of the habitat, a deployable subframe that hinges off the mounting frame and folds down to self-level itself on the planetary surface, and a multi-sectional deck with folding handrails that folds down to rest on the secured subframe to become a level porch with adjustable ramp. The operation of the DEVAP begins with the lowering of the deployable subframe. Once the subframe is lowered, the supporting legs are adjusted to conform to deviations in the natural terrain. The subframe will then transfer all moment forces of the deploying deck through itself to the ground, rather than through the habitat wall. Next, the multisectional deck is unfolded, with the section nearest to the ingress/egress port remaining as a level porch, and the subsequent sections allowed to slope down to the planetary surface. After all decks have been secured, the side handrails are lifted into place from their folded configurations, completing the deployment of the DEVAP. Once the deployment sequence is complete, suited crewmembers can use the platform to ingress/egress the habitat, stage for EVAs, prepare tools, and remove dust from environmental suits.

The DEVAP system is designed to be robust in a highly abrasive, lunar dust environment, and to protect the ingress/egress port as much as possible from dust incursion. Joints and components on flight versions of the DEVAP will be designed to be particularly reliable under these conditions.

This work was done by Alan Howe of NASA’s Jet Propulsion Laboratory; and Adam Dokos, David Rowell, Adam Cofield, Jerad Merbitz, and Jeremy Parr of Kennedy Space Center. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact KSC-DLTechnologyTransfer@ mail.nasa.gov. KSC-13673


NASA Tech Briefs Magazine

This article first appeared in the May, 2016 issue of NASA Tech Briefs Magazine.

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