Siegfried W. Janson

Direct-write UV-laser microfabrication of 3D structures in lithium-aluminosilicate glass

The direct-write laser machining technique has been used to process a lithium-alumosilicate glass (FoturanTM) for an application which requires 3D patterned microstructures. Using two UV laser wavelengths (248 nm and 355 nm), microcavities and microstructures have been fabricated for the development of microthrusters for attitude and orbit control of a 1 kg class (10 cm diameter) nanosatellite. In addition, experiments have been conducted to define the processing window for the laser patterning technique. The results include a measure of the change in Foturan strength after a required program bake cycle plus HF etching rates as a function of the laser repetition rate for the two UV wavelengths.

Fabrication of true 3D microstructures in glass/ceramic materials by pulsed UV laser volumetric exposure techniques

A pulsed UV laser based technique has been developed which permits the transfer, by direct-write exposure, of 3D image into a photosensitive glass/ceramic material. The exposed latent image volume is developed via temperature programmed bake process and then etched away using HF in solution. The height of the 3D microstructures is controlled by the initial laser wavelength used during the exposure and the time duration of the etching cycle. Using this technique we have fabricated large arrays of microstructures which have applications to microfluidics, microelectromechanical systems and optoelectronics. The resulting master copy can be used either as is or by use standard injection modeling techniques converted into a metallic or plastic copies. We present these results and others which have specific applications to miniature 1Kg class satellites - nanosatellites.

Development of a 100-gm-class inspector satellite using photostructurable glass/ceramic materials

A pulsed UV laser volumetric direct-write patterning technique has been used to fabricate the structural members and key fluidic distribution systems of a miniature 100 gm mass spacecraft called the Co-Orbital Satellite Assistant (COSA). A photostructurable glass ceramic material enables this photo-fabrication process. The COSA is a miniature space vehicle designed to assist its host ship by serving as a maneuverable external viewing platform. Using orbital dynamics simulation software, a minimum (Delta) V solution has been found that allows a COSA vehicle to eject from the host and maneuver into an observation orbit about the host vehicle. The result of the simulant show that a cold gas propulsion system can adequately support the mission given a total fuel volume of 5 cm3. A prototype COSA with dimensions of 50 X 50 X 50 mm has been fabricated and assembled for simulation experiments on an air table. The vehicle is fashioned out of 7 laser patterned wafers, electronics boards and a battery. The patterned wafers include an integrated 2-axis propulsion system, a fuel tank and a propellant distribution system. The electronics portion of the COSA vehicle includes a wireless communication system, 2 microcontrollers for system, 2 microcontrollers for system control and MEMS gyros for relative attitude determination. The COSA vehicle is designed to be mass producible and scalable.

Time‐resolved mass and energy analysis by position‐sensitive time‐of‐flight detection

We describe a method for time‐resolved mass and kinetic energy analysis of ionic or neutral species (1–150 amu, 0.5–500 eV) in diagnostic measurements on spacecraft electric thrusters. Time‐of‐flight mass spectrometry is combined with position‐sensitive detection to measure energy spectra for multiple masses at sampling rates as high as 50 kHz. A rectangular microchannel plate detector with a 96‐element metal anode array is read out by fast analog‐to‐digital converters or by discriminators and scalers. The ion drift time varies as the square root of the mass‐to‐charge ratio, and the displacement along the detector varies as the square root of the energy‐to‐charge ratio. The energy resolution is enhanced by minimizing the field distortion near grid wires.

Nanosatellites and MEMS fabrication by laser microprocessing

By definition Nanosatellites are space systems that can weigh 1010 kg and can perform unique missions (e.g. global cloud cover monitoring, store-and-forward communications) acting either in constellation of distributed sensor-nodes or in a many-satellite platoon that flies in formation. The Aerospace Corporation has been exploring the application of microelectronics fabrication and advanced packaging technology to the development of a mass-producible nanosatellite. Particular attention is being directed at M3 (Micromachining/MEMS/Microsystems) technology which appears to be important in the integration and manufacturing of these satellites. Laser direct-write processing techniques are being applied for rapid prototyping and to specific 3D fabrication steps where conventional microelectronics fabrication techniques fall short. In particular, a laser based technique has been developed that combines the rapid prototyping aspects of direct-write and the low cost/process uniformity aspects of batch processing. This technique has been used to develop various fluidic components and a microthruster subsystem in a photostructurable glass/ceramic material.

LEO to ground optical communications from a small satellite platform

A pair of 2.2 kg CubeSats using COTS hardware is being developed for a proof-of-principle optical communications demo from a 450-600 km LEO orbit to ground. The 10x10x15 cm platform incorporates a 25% wall-plug efficient 10-W Yb fiber transmitter emitting at 1.06 μm. Since there are no gimbals on board, the entire spacecraft is body-steered toward the ground station. The pointing accuracy of the LEO craft, which governs the data rate capability, is expected to be ~ 0.1-0.2 deg. Two optical ground stations, located at the Mt. Wilson observatory, have receiver apertures of 30 and 80 cm. Launch of the CubeSat pair is anticipated to be mid to late 2015.

Big benefits from tiny technologies: micro-nanotechnology applications in future space systems

An overview of the micro-nanotechnology field is presented with application toward future space systems. Specific discussions are presented on the insertion of MEMS, MOEMS and quantum effect nanoelectronic devices into both current and future space systems. Silicon satellites, based on batch-fabricated microengineered systems are also discussed.

Microengineered cold gas thruster system for a co-orbiting satellite assistant (COSA)

Miniaturization technologies such as Micro-Electro-Mechanical Systems (MEMS) have been used to fabricate a prototype 100-gm class cold gas propulsion system suitable for use on a Co-Orbiting Satellite Assistant (COSA). The propulsion system is fabricated from bonded layers of photostructurable glass (Foturan glass; the design is based on fabricating integrated modular parts. Thus, the propulsion system is mass producible, expandable, expendable (low unit cost), and highly integrated.

Aerospace applications of MEMS

MEMS offer ultra-low mass, low-power components which may integrated into a variety of aerospace systems. Aerospace-specific MEMS are limited by the relatively small size of the aerospace vehicle market compared to traditional MEMS markets such as automobiles and home computers. Nevertheless, significant applications such as inertial guidance, micro-vehicle propulsion, and active antennas will drive evolution of existing MEMS technologies to meet these needs. MEMS enable many near-term micro-vehicle concepts, and possible mid-to-far term applications such as aerodynamic skin flow control and active aerospace structures.

Reduction in ignition energy for single-shot microthrusters using pulsedlaser excitation

An experiment has been conducted to compare the ignition energy of an existing digital thruster design between a pulsed electrical and laser excitations. A 355nm Nd-YAG pulsed laser is used to ignite the stored lead styphnate propellant charge. Given the device design, roughly 800 μJ is necessary to ignite a 180 μg charge volume with a 90% probability of ignition. This energy value is considered an upper limit. Under equivalent conditions, roughly 2.4mJ of electrical energy is required to ignite the same volume. The digital thruster concept is one approach to provide a valveless, slap-on propulsion capability for small (1kg mass class) and large satellites (1000kg mass class) to help maintain attitude or control the damping of low frequency oscillations in extended surfaces.