Deep-Space Positioning System (DPS)
JPLs deep-space positioning system consists of narrow- and wide-angle cameras, a coelostat, an S- or X-band receiver and patch antenna, and a central processor that hosts the navigation computations and controls the coelostat. The DPS instrument determines the location of the hosting spacecraft via images of solar system objects and, optionally, via one-way radio to the Earth or another known object from which Doppler observables are extracted. To make the instrument as small and lightweight as possible, the pointability of the coelostat is combined with that of the antenna into a single mechanism. Additional mass and volume are saved through the placement of the wide-angle camera behind the secondary reflector of the narrow-angle camera such that the wide-angle camera shares the precise field of the narrow-angle camera and can provide accurate pointing information for the narrow-angle camera. The DPS is also advantageous because the coelostat can be used to relieve the pointing requirements of the host spacecraft with respect to navigation imaging and radiometric link closure. (Most missions require either a reorientation of the spacecraft or a cessation of science activities in order to obtain navigation data when the desired science and navigation targeting are different.)
materials and coatings
Creating Low Density Flexible Ablative Materials
The low density flexible ablator can be deployed by mechanical mechanisms or by inflation and is comparable in performance to its rigid counterparts of the same density and composition. Recent testing in excess of 400W/cm2 demonstrated that the TPS char has good structural integrity and retains similar flexibility to the virgin material, there by eliminating potential failure due to fluttering and internal stress buildup as a result of pyrolysis and shrinkage of the system. These flexible ablators can operate at heating regimes where state of the art flexible TPS (non-ablative) will not survive. Flexible ablators enable and improve many missions including (1) hypersonic inflatable aerodynamic decelerators or other deployed concepts delivering large payload to Mars and (2) replacing rigid TPS materials there by reducing design complexity associated with rigid TPS materials resulting in reduced TPS costs.
materials and coatings
A New Family of Low-Density, Flexible Ablators
The low-density, flexible ablators are comprised of a polymer resin embedded in a fibrous substrate, with a density range of 0.2g/cm cube-0.6 g/cm cube to date. The polymer resin thermally decomposes during ablation. The resin can be a thermo setting resin, athermoplastic polymer, or alternatively, a co-cured mixture. The fibrous substrate is flexible or conformable to a curved surface, with high thermal stability. The thickness of the fibrous substrate is between 1.3 and 7.6 cm, where the diameters of the fiber are between 7 and 25 micrometer. Embodiments of the fibrous substrates can include various woven, stitched or loosely packed carbon, polymer and ceramic felts as high-temperature substrates. One feature of this innovation is that it can withstand a range of heating rates with the upper limit approaching that of NASA rigid ablators. The amount and composition of polymer resin can be readily tailored to specific mission requirements. This technology offers a simple and versatile manufacturing approach to produce large areas of heat shields that can be relatively easily attached on the exterior of spacecraft.
Lens-Coupled Dielectric Waveguides
Conventional interconnects consist of tapering the extremities of the dielectric waveguide that are inserted directly in the metallic waveguides, using long waveguide transition to reduce coupling loss (radiation at the dielectric-metallic interface). With JPL's novel interconnect solution, a lens couples the power from the metallic waveguide to the dielectric waveguide. (This lens can be fabricated inexpensively from the same dielectric material as the dielectric waveguide.) The ellipsoid geometry of the lens is designed to maximize the coupled power into the dielectric waveguide, resulting in only a small fraction of the coupled power radiating at the interface (14 to 20 dB). A small stepped impedance at the input of the lens and inserted in the waveguide provides a better matching impedance network at the discontinuity. Unlike conventional interconnects, the lens-coupled dielectric waveguide does not depend on physics contact; this improves reliability, reduces packaging complexity, and allows for added vibration/stress immunity.
materials and coatings
New Resin Systems for Thermal Protection Materials
This method produces a low density ablator similar to Phenolic Impregnated Carbon Ablator (PICA) using a cyanate ester and phthalonitrile resin system, rather than the heritage phenolic resin. Cyanate ester resin systems can be cured in a carbon matrix and generate high surface area structure within the carbon fibers. This helps to reduce the thermal conductivity of the material which is one of the key requirements of thermal protection system (TPS) materials. The material has densities ranging from 0.2 to .35 grams per cubic centimeter. NASA has successfully processed the cyanate ester and phthalonitrile resins with a morphology similar to that of the phenolic phase in PICA, but with more advanced properties such as high char stability, high char yield, and high thermal stability. This new generation of TPS materials has the same microstructure as heritage PICA, but improved characteristics of PICA such as increased char yield, increased char stability, increased thermal stability and increased glass transition temperature.
materials and coatings
Multifunctional Ablative Thermal Protection System
The initial compression pad design for Orion was complex and limited to Earth orbit return missions, such as the 2014 Exploration Flight Test-1 (EFT-1). The 2-D carbon phenolic material used for EFT-1 has relatively low interlaminar strength and requires a metallic sheer insert to handle structural loads. There are few options for materials that can meet the load demands of lunar return missions due to performance or part-size limitations. The 3DMAT material is a woven fiber preform fully densified with cyanate ester resin. It produces a large composite with significant structural capabilities and the ability to withstand high aerothermal heating environments on its outer surface while keeping the inner surface cool and protected from the aerothermal heating. The robustness of the 3DMAT material is derived from high fiber volume (>56%), 3-D-orthoganol architecture, and low porosity (0.5%). Orion has adopted 3DMAT for all future MPCV missions, including EM-1 schedule to launch in 2018.
Far-Infrared Microwave Kinetic Inductance Detector (FIR MKID) Array
The FIR MKID consists of the two major components: (1) the metal pattern for FIR absorption, and (2) the microwave transmission line resonator for RF readout. The cross bar metal pattern on the membrane provides identical power absorption for both horizontal and vertical polarization signals. The metal patterns are placed on both the top and bottom of the membrane to create a parallel-plate-coupled transmission line that acts as a half-wavelength resonator at readout frequencies. The parallel-plate transmission line in the membrane area is connected to a low impedance micro-strip line at the detector edges to form a stepped impedance. The parallel-plate transmission line on the membrane is split into four sections in a meandering cross pattern. At IR frequencies, the detectors superconducting metal pattern acts as an absorber. It is designed to have the effective area match with the characteristic impedance of free space, resulting in minimum return loss at the center of the operating frequency. This maximizes the power absorption in the metal pattern, causing the temperature of the metal to increase. This enables detection of very low power far infra-red frequency signals that has both horizontal and vertical polarizations.
information technology and software
The system consists of a central server and a collection of client libraries that provide different levels of functionality. The server is a standalone application that acts as the central hub of communication for one or more busses. Functionality levels currently include: Base Layer implements the ITCSB core. All other layers are built on top of this one. 1553 is an implementation of the MIL-STD-1553B specification in which the hardware is replaced by an interface to the ITCSB Base Layer. SpaceWire (SPW) is an implementation of the SPW bus. Time Sync provides a way for multiple simulation components to synchronize on an arbitrary time frame. The layered architecture separates the protocol-specific implementation from the core implementation. Additional utilities include a 1553 user interface and SpaceWire interface. The user interfaces provide visual representations of the data and provide the capability to intercept and modify data being passed by the system.
SpaceCube Demonstration Platform
The HST SM4 SpaceCube flight spare was modified to create an experiment called the SpaceCube Demonstration Platform (SC DP) for use on the MISSE7 Space Station payload (in collaboration with NRL). It is designed to serve as an on-orbit platform for demonstrating advanced fault tolerance technologies. With the use of Xilinx commercial Virtex4 FX60 FPGAs, the fault tolerant framework allows the system to recover from radiation upsets that occur in the rad-soft parts (Virtex4 FPGA logic, embedded PPCs in Virtex4 FPGAs, SDRAM and Flash), the C&DH system that runs simultaneously on both Virtex4 FPGAs that uses a robust telemetry packet structure, checksums, and the rad-hard service FPGA to validate incoming telemetry. The ability to be reconfigured from the ground while in orbit is a novel benefit, as well as is the onboard compression capabilities that allow compressed files from the ground to be uploaded to the SpaceCube.
information technology and software
Radiation Hardened 10BASE-T Ethernet Physical Interface
Currently there is no radiation hardened Ethernet interface device/circuit available commercially. In this Ethernet solution, the portion of the PHY in the FPGA is responsible for meeting the IEEE 802.3 protocol, decoding received packets and link pulses, and encoding transmitted data packets. The decoded payload data is sent to a user interface internal to the FPGA which sends data for transmission back to the FPGA PHY. The transmit portion is composed of two AD844 op amps from Analog Devices with appropriate filtering. The receive portion is composed of a transformer, an Aeroflex Low-Voltage Differential Multi-drop device, and appropriate filtering.