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Ultralight materials present an opportunity to dramatically increase the efficiency of load-bearing aerostructures. To date, however, these ultralight materials have generally been confined to the laboratory bench-top, due to dimensional constraints of the manufacturing processes. We show a programmable material system applied as a large-scale, ultralight, and conformable aeroelastic structure. The use of a modular, lattice-based, ultralight material results in stiffness typical of an elastomer (2.6 MPa) at a mass density typical of an aerogel (5.6 [Formula: see text]). This, combined with a building block based manufacturing and configuration strategy, enables the rapid realization of new adaptive structures and mechanisms. The heterogeneous design with programmable anisotropy allows for enhanced elastic and global shape deformation in response to external loading, making it useful for tuned fluid-structure interaction. We demonstrate an example application experiment using two building block types for the primary structure of a 4.27m wingspan aircraft, where we spatially program elastic shape morphing to increase aerodynamic efficiency and improve roll control authority, demonstrated with full-scale wind tunnel testing.

We describe the design and analysis of an androgynous fastener for autonomous robotic assembly of high performance structures. The design of these fasteners aims to prioritize ease of assembly through simple actuation with large driver positioning tolerance requirements, while producing a reversible mechanical connection with high strength and stiffness per mass. This can be applied to high strength to weight ratio structural systems, such as discrete building block based systems that offer reconfigurability, scalability, and system lifecycle efficiency. Such periodic structures are suitable for navigation and manipulation by relatively small mobile robots. The integration of fasteners, which are lightweight and can be robotically installed, into a high performance robotically managed structural system is of interest to reduce launch energy requirements, enable higher mission adaptivity, and decrease system life-cycle costs.

Robotic in-space assembly of large space structures is a long-term NASA goal to reduce launch costs and enable larger scale missions. Recently, researchers have proposed using discrete lattice building blocks and co-designed robots to build high-performance, scalable primary structure for various on-orbit and surface applications. These robots would locomote on the lattice and work in teams to build and reconfigure building-blocks into functional structure. However, the most reliable and efficient robotic system architecture, characterized by the number of different robotic ‘species’ and the allocation of functionality between species, is an open question. To address this problem, we decompose the robotic building-block assembly task into functional primitives and, in simulation, study the performance of the the variety of possible resulting architectures. For a set consisting of five process types (move self, move block, move friend, align bock, fasten block), we describe a method of feature space exploration and ranking based on energy and reliability cost functions. The solution space is enumerated, filtered for unique solutions, and evaluated against energy and reliability cost functions for various simulated build sizes. We find that a 2 species system, dividing the five mentioned process types between one unit cell transport robot and one fastening robot, results in the lowest energy cost system, at some cost to reliability. This system enables fastening functionality to occupy the build front while reducing the need for that functional mass to travel back and forth from a feed station. Because the details of a robot design affect the weighting and final allocation of functionality, a sensitivity analysis was conducted to evaluate the effect of changing mass allocations on architecture performance. Future systems with additional functionalities such as repair, inspection, and others may use this process to analyze and determine alternative robot architectures.

Here we present the design and ground testing for a nanosatellite mission that will demonstrate terrestrial-to-space clock synchronization using a pulsed optical link to a low Earth orbiting nanosatellite. The 1 kg, 1 L nanosatellite payload comprises fully redundant chip-scale atomic clocks, microprocessor-based clock counters, picosecond event timers, and avalanche photodetectors. During flight operations, an experimental satellite laser ranging facility, located at the Kennedy Space Center in Florida, will emit nanosecond optical pulses of infrared laser light towards the nanosatellite. By reflecting the emitted pulses off of a retroreflector array mounted on the nadir face of the nanosatellite and returning the pulses back to the ground, the laser ranging facility will record the round-trip light-travel time of the laser pulses. At the same time, one of the avalanche photodetectors will record the arrival time of the pulses at the nanosatellite. By combining these data, the discrepancy between the ground and space clocks can be determined, in addition to the range to the satellite. Laboratory testing of the space instrument indicates a short term time-transfer precision of less than 200 ps, equivalent to a range accuracy of 6 cm. This flight instrument will comprise roughly 1U of a 3U CubeSat mission manifested for launch in the Fall of 2017 through NASA’s CubeSat Launch Initiative program.

Digital material structures are lattices composed of discrete elements that are connected to create assemblies that can exhibit high performance mechanical characteristics. This paper presents the development and robustness characterization of a system, called Gantry Autonomous Robotic Integrator (GARI), which is designed to automatically assemble these structures. The relative positioning tolerance for connecting elements and methods to increase the reliability of automated assembly of these structures are specifically described. A compact end-effector design is presented, which shows high precision and adjustability, and calibration procedures for the build plate are defined. The bolting reliability for this end-effector is analyzed to identify tolerance requirements and establish performance benchmarks for component feed stations. Two extremal cases to test the bolting reliability of the end-effector are explored, one case with a well-constrained target voxel and the other case with a minimally constrained target voxel. The resulting bolting success tolerance maps are described, which indicate greater than 95% successful bolting probability within 0.254 mm in all directions from nominal target placement.

We describe analytic methods for the design of the discrete elements of ultralight lattice structures. This modular building block strategy allows for relatively simple element manufacturing as well as relatively simple robotic assembly of low mass-density structures on orbit, with potential for disassembly and reassembly into highly varying and large structures. This method also results in a structure that is easily navigable by relatively small, mobile robots. The geometry of the cell can allow for high packing efficiency to minimize wasted payload volume while maximizing structural performance and constructability. We describe the effect of geometry choices on the mechanical properties and automated robotic constructability of a final system. Geometric properties considered include number of attachments per voxel, number of attachments per coefficient of volume, and effects of vertex, edge, and face connectivity of the unit cell. Mechanical properties considered include strength scaling, modulus scaling, and packing efficiency of the lattice. Automated constructibility metrics include volume allowance for an end-effector, strut clearance angle for an end-effector, and packing efficiency. These metrics were applied to six lattice unit cell geometries: cube, cuboctahedron, octahedron, octet, rhombic dodecahedron, and truncated octahedron. A case study is presented to determine the most suitable lattice system for a specific set of strength and modulus scaling requirements while optimizing for ease of robotic assembly.

This paper reviews the development of the Mission Adaptive Digital Composite Aerostructures Technologies (MADCAT) v0 demonstrator aircraft, utilizing a novel aerostructure concept that combines advanced composite materials manufacturing and fabrication technologies with a discrete construction approach to achieve high stiffness-to-density ratio ultra-light aerostructures that provide versatility and adaptability. This revolutionary aerostructure concept has the potential to change how future air vehicles are designed, built, and flown, with dramatic reductions in weight and manufacturing complexity the number of types of structural components needed to build air vehicles while enabling new mission objectives. We utilize the innovative digital composite materials and discrete construction technologies to demonstrate the feasibility of the proposed aerostructure concept, by building and testing a scaled prototype UAV, MADCAT v0. This paper presents an overview of the design and development of the MADCAT v0 flight demonstrator.