DMF | Deployable Modular Frame

Inflatable Space Modules for space exploration are now a reality. In 2016, Bigelow Aerospace tested the first inflatable module Bigelow Expandable Activity Module (BEAM) on the International Space Station (ISS), achieving success. This technology has higher volume limits than other launchers, substantially changing the previous concepts of construction and life in space. Nevertheless, inflatable modules technology lacks a reliable and functional platform to efficiently use all this space. Due to its limited dimension, the International Standard Payload Rack (ISPR), currently used on ISS, is not suitable for this purpose. The project aims at developing a new standard for payload rack in the inflatable space modules: the Deployable Modular Frame (DMF). The DMF expands itself radially from the center of the module, starting from four structural pylons. It creates a solid infrastructure allowing for the configuration of a variety of spaces, including storage space, laboratories, workstations and living quarters. The DMF consists of two main parts: the Deployable Frame (DF) and the Modular Rack (MR). Once the frame is deployed, it provides four linear slots suitable to install the modular racks. The rack is the basic element that allows for the storage of equipment inside the frame. Once they are installed, the racks can slide on the frame’s rails, dynamically changing the space inside the module. This system, inspired by the Random Access Frame Random Access Frame (RAF) designed by A. Scott Howe for the Jet Propulsion Laboratory (JPL), achieves a high deployability through the use of constant force springs, deploying a radial rail system which reduces the work load of the astronauts on the rack. This asset reverses the internal configuration proposed by the Bigelow Aerospace. The frame includes a stereo-vision camera system to verify the correct deployment of the inflatable modules and the frame itself. The stereo-vision system checks whether the correct shape is constantly maintained.

Inflatable technologies for Space applications are not a new asset, but recent R&D provided by the private sector (e.g. Bigelow Aerospace ltd, Sierra Nevada Corp.)has demonstrated that these structures are a viable solution. Inflatable structures have larger diameter limits than commercial rocket fairings, thereby allowing current launchers to bring structures of much larger volume into orbit. They represent a change of paradigm in manned space exploration and a flight-proven technology for the next generation of orbital, deep space, and planetary habitats. However, the adoption of this new architecture for space modules brings with it a set of challenges in human integration design. Themainchallengeisrepresentedby the outfit of equipment and instrumentation inside a soft-based architecture. Until now, for this purpose, we relied on modular racks such as the ISPR, still used on theISS and derived from the Space Shuttle program. However, without a rigid infrastructure with which to outfit the racks, inflatable modules need a new standard infrastructure that allows for the efficient use of the space post inflation. Proposed architectures for commercial modules such as the Bigelow B2100 or the Sierra Nevada make use of non-standardized assemblies, that require a lot of effort from astronauts to perform their functions. The aim of this paper is to explore a possible configuration to outfit standard racks inside an inflatable module. This standard will be used to configure laboratories, storage space, living quarters, and other instrumentation in a modular and scalable architecture specifically designed for inflatable modules.

The DMF exploits one of the most common configurations for inflatable modules, using the existing structural beams that provide structural rigidity between the two main airlocks.DMF adds a deployable sub-structure in which it is possible to safely outfit the equipment and instrumentation.DMFshare the same flexibility of a standard rack module such as the ISPR, enabling the development of standardized equipment shared between inflatables of different sizes and configurations. The internal outfit of equipment still relies on the work of astronauts, but the pre-deployed infrastructure mitigates the general effort needed for in-space assembly. The racks are set perpendicular to the corridor, dividing the dynamics pace from the working surfaces. After the assembly phase, the system provides a dynamic asset to configure the internal space at will, sliding the outfitted racks onto the deployed rails. This feature, shared with the mobile shelving systems from contemporary libraries, allows for a working surface 4 times bigger than those of traditional architecture. Although the racks cannot all be accessed at the same time, multiple experiments and equipment can run simultaneously, even in a compressed configuration, since all the submodules stay connected to the external interfaces (placed in the pylons). The Bigelow AerospaceB330 has been chosen as a testbed for the proposed technology. In order to demonstrate the system capabilities, the B330 design provided in this paper can be different from the last one proposed by Bigelow Aerospace, based on the last public design iterations.2.1 mechanical subsystemsTheDMF module is composed of two subsystems: the DF and the MR. The two systems are complementary and, with minor adjustments, can be adapted to different inflatable module configurations. While the dynamic phase oftheDFtakesplaceonlyinthedeploymentphase of the system, the MR maintains its dynamic capabilities during its entire lifetime. ThefunctionoftheDFistoprovidethein-frastructurefortheMR, and the only effort needed to keep it in working conditions to verify that the deployed shape is maintained. TheMR is the substructural unit that allows for the outfitting of equipment. Each rack is standardized and is made of structural profiles and joints. Aminimumof2racksisneededtoassembleasubmodule, in which install the equipment. The dynamic component of MR is composed by five four-wheeled, greaseless sliders, that allow each rack to slide onto the DF rails.

The MR is assembled from commercial, off-the-shelves, structural profiles (40x40mm and 40x80mm),joined on each side by a bolted plate on the profiles. Eachrack comes assembled, and can slide on the rails using tofive sliders with 4 wheels each. Each slider includes amanual block system to fix the rack on the rails once thefinal position is set. A single rack can be interfaced withmore of it to create more complex structures.The equipment stored in the sub-modules are poweredthrough the main pylons, and can still slide on the framewithout being disconnected them from the power source. The maximum distance to create a connection betweentwo racks is settled at 1.1m due to the dimensions of thepanels. The sub-module allows for the maximal distancetobesetto8framesinab330module,resultinginasingle-structure module with a maximum length of 7.58m. Sincethe static loads on the frame are lower in space than onearth, and do not need to bear launch forces, the racks canbe manufactured directly on board, utilizing manufactur-ing techniques such as 3d printing, resulting in a muchlighter total weight of the structure.

The submodule is the basic unit of theDMF system.Each submodule has functions comparable to anISPRmodule but with 3 times the available surface. As statedabove, a submodule is composed by twoMR and a set ofpolimeric enclosure panels to join the two racks. Whileone single module can provide the working surfaces tooperate experiments and scientific equipment, more sub-modulescanbejoinedtooutfitclosedsubspacesinsidethemodule, such as crew quarters, greenhouses or environ-mental controlled spaces. The submodules are connectedthrough flexible cabling with the interfaces placed in thestructural pylons, that provides power, controlled atmo-sphere, water and data. Thanks to this feature, the mod-ulecanbecompressedontotheDFrailswithoutinterrupt-ing any functions. All the components and the equipmentneeded to outfit the submodules can be stored in the cen-tral hallway during the launch phase.