The scope of the analysis was to determine the capability of the Michigan Aerospace Corporation (MAC) Autonomous
Docking Satellite System II (referred to as 'ASDS' for the remainder of this paper), and to develop and mature the concept.
The integrated system model included detailed subsystem models. A cable model was developed from the test data that resulted in good correlation. A high fidelity subsystem model of the cam resistance force was modeled. The integrated system model also includes contact definitions, final latching/locking definition, and various sensors.
Over 3,000 cases were analyzed to identify areas where the MAC docking concept can be improved. Sensitivity and Monte Carlo studies were completed to understand the mechanism’s capture capability, determine subsystem requirements, and evolve the design for improved performance.
We describe the design of novel fuel atomizers with a unique internal spiral-conical structure for turbine engines and other propulsion systems. The atomizers are developed using a unique combination of two recently developed technologies: polymer-derived ceramics and an invert microstereolithography process. The polymer-derived ceramics are stable up to high temperatures (1500~1800ºC) and have excellent mechanical and thermal properties. Thus, fuel atomizers made from these materials can be used at high temperatures and have higher corrosion resistance. Invert microstereolithography is a recently developed 3-D microfabrication process that enables complex 3-D structures to be built with high dimensional precision (1µm). The resulting atomizers have many advantages, including stability at high temperatures, high resistance to corrosion, a unique structure for efficient sprays, low cost and amenability to batch manufacturing. With the success of our earlier investigation and recent development, we are able to develop novel atomizers that will fill an immediate need for propulsion systems and many other high-temperature applications. In the future, we will integrate the atomizers into combustion systems and perform physical demonstration of the complete fuel injection system on a representative engine platform for a range of operating conditions.
During the development of an autonomous spacecraft docking mechanism, one of the primary areas of interest in the way the mechanism will behave in a micro-gravity environment. This issue is of particular interest when a flexible soft-dock cable is used to make initial capture, because ground-based testing does not adequately represent the environmental conditions that will be seen on orbit. To this end, Michigan Aerospace Corporation has recently conducted flight tests of its prototype autonomous satellite docking system in a micro-gravity environment on the KC-135 in conjunction with the Air Force Research Laboratory Space Vehicles Directorate and Microcosm, Inc. Though the first flight was primarily for the purpose of testing the core operating principles of the docking mechanism, several lessons were learned that will be applied toward developing a second, more advanced prototype and experimental setup intended for a second series of flights on the KC-135. Areas of improvement for the new flight test will be in the physical operation of the experimental apparatus and the data collection methods used. The use of redundant sensors as a means of eliminating noise will be explored, as will the merits of using a combination of coarse and fine sensors to collect data over a broader measurement range.
The past five years has witnessed a significant increase in the attention given to on-orbit satellite docking and servicing. Recent world events have proven how we have come to rely on our space assets, especially during times of crisis. It has become abundantly clear that the ability to autonomously rendezvous, dock, inspect and service both military and civilian assets is no longer a nicety, but a necessity. Reconnaissance and communications satellites, even the space shuttle and International Space Station, could benefit from this capability. Michigan Aerospace Corporation, with funding from the Defense Advanced Research Projects Agency (DARPA) and the Air Force Research Laboratory (AFRL), has been refining a compact, light, compliant soft-docking system. Earlier prototypes have been tested on the Marshall Space Flight Center (MSFC) flat-floor as well as on the Johnson Space Flight Center (JSC) KC-135 micro-gravity aircraft. Over the past year, refinements have been made to the mechanism based on the lessons learned from these tests. This paper discusses the optimal design that has resulted.
Michigan Aerospace Corporation has developed a mechanism for microsatellite docking, which has been successfully demonstrated in a microgravity environment. This docking mechanism is specifically designed for soft-docking capability, tolerance to misalignment, and scalability. The current Autonomous Microsatellite Docking System (AMDS) design resulted from modifications to an earlier docking mechanism prototype that was tested at the Marshall Space Flight Center (MSFC) Flat Floor Facility.
The AMDS was tested in a microgravity environment through the NASA JSC Reduced Gravity Program, where a KC-135 turbo jet flies a series of parabolic maneuvers. The test objectives of the KC-135 flight were to determine the docking mechanism cable assembly behavior in zero-g, test the full range of the docking envelope in a six degree of freedom test setup and determine the undocking capability and stability. The nature of the Michigan Aerospace docking mechanism enabled the entire docking cycle, including soft dock, auto-alignment and hard dock, to be completed within the 20 seconds of 'zero-g' time. Complete end-to-end docking and undocking was performed under a variety of initial conditions and docking parameters. The data collected during the KC-135 testing will be used to validate dynamic simulation models of the docking mechanism. The intent of these dynamic models is to examine a number of docking scenarios between a chaser and target satellite. This paper will discuss the results of the KC-135 docking tests and docking simulations.
In recent years, Michigan Aerospace has approached the problem of gentle autonomous spacecraft rendezvous and docking using a flexible soft-dock cable that is extended from the docking spacecraft to the target spacecraft. Because of the nature of a soft-dock cable, testing and validation of the technology is difficult in normal gravity. To properly emulate the behavior of this soft-dock cable, we have performed dynamic computer simulations so that the effects of micro-gravity could be simulated. The Autonomous Satellite Docking System (ASDS) was initially prototyped and tested at Marshall Space Flight Center’s air-bearing floor facility. The test data was compared to the simulations and used to validate the model. Once a good correlation between the simulation’s predicted results and the actual data was shown, the model was used to predict future performance of the ASDS mechanism on several potential spacecraft for the Orbital Express program. A new dynamic simulation model was created and compared to test data from a recent KC-135 flight test to further validate the modeling approach used. This paper will describe the methodology used in modeling and simulating the ASDS mechanism. Correlation between the models and the test data will be discussed.