SPHERES Tethered Formation Flight Testbed: Application to NASA's SPECS Mission

by on 9 June 2015in Technology Development & Demonstration No comment

This paper elaborates on theory and experiment of the formation flight control for the future space-borne tethered interferometers. The nonlinear equations of multi-vehicle tethered spacecraft system are derived by Lagrange equations and decoupling method. The preliminary analysis predicts unstable dynamics depending on the direction of the tether motor. The controllability analysis indicates that both array resizing and spin-up are fully controllable only by the reaction wheels and the tether motor, thereby eliminating the need for thrusters. Linear and nonlinear decentralized control techniques have been implemented into the tethered SPHERES testbed, and tested at the NASA MSFC's flat floor facility using two and three SPHERES configurations. The nonlinear control using feedback linearization technique performed successfully in both two SPHERES in-line configuration and three triangular configuration while varying the tether length. The relative metrology system, using the ultra sound metrology system and the inertial sensors as well as the decentralized nonlinear estimator, is developed to provide necessary state information.

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Propellant-Free Control of Spinning Tetherd Formation Flight, Part 2: Nonlinear Underactuated Control

by on 9 June 2015in Technology Development & Demonstration No comment

This is the second in a series of papers that exploit the physical coupling of tethered spacecraft to derive a propellant-free spin-up and attitude control strategy. We take a nonlinear control approach to underactuated tethered formation flying spacecraft, whose lack of full state feedback linearizability, along with their complex nonholonomic behavior, characterizes the difficult nonlinear control problem. We introduce several nonlinear control laws that are more efficient in tracking time-varying trajectories than linear control. We also extend our decentralized control approach to underactuated tethered systems, thereby eliminating the need for any intersatellite communication. To our knowledge, this work reports the first nonlinear control results for underactuated tethered formation flying spacecraft. This article further illustrates the potential of the proposed strategy by providing a new momentum dumping method that does not use torque-generating thrusters.

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Perspectives of Bar Telemetric Means Utilization for Leakage Detection and Monitoring of the ISS Construction Conditions

by on 9 June 2015in Technology Development & Demonstration No comment

The set of telemetric means for prompt leakage detection on the ISS modules in the orbit was developed in course of preparation of BAR space experiment on the Russian Segment of the ISS. The set of instruments to be accommodated in pressurized volume is aimed at leakage points detection as well as solving some fundamental problem such as: - early detection and preventing leakage from habitable modules of the ISS resulting from biological degradation of construction elements; - analysis of ultrasonic atmospheric oscillation intensity in the modules’ pressurized volume as a source of adverse crew effect. That pressurized equipment set for leakage detection in the ISS modules can be used together with SSRMS manipulator that gives the following opportunities: - to detect promptly air leakage from the ISS modules; - to monitor results of unknown factors and objects impact on the modules for contingency prediction; - to monitor the ISS outer surface elements conditions. The most important task is to support the manipulator control and image obtaining by the operators of the Mission Control Center.

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Space radiation damage to HDTV camera CCDs onboard the international space station

by on 9 June 2015in Technology Development & Demonstration No comment

The image quality of high-definition television (HDTV) cameras and camcorders for space activity is degraded by the presence of permanent bright pixels (so-called “white defects”) due to space radiation. We studied the space radiation damage to HDTV charge-coupled devices (CCDs; 2 × 106 pixels per chip) loaded in the Russian service module (SM) of the International Space Station (ISS) for 71 days, 256 days and 446 days. We used the “Passive Dosimeter for Lifescience Experiments in Space” (PADLES), which consists of CR-39 plastic nuclear track detectors (PNTDs) and thermoluminescent dosimeters, to measure space radiation doses received by the HDTV CCDs in the SM during loading periods. The average production rates of white defects for output voltage greater than 0.5 mV were 2.366 ± 0.055 pixels/day in Si and 5.213 ± 0.071 pixels/mGy in Si. We also investigated the correlation between the position of the white defects and tracks of high-energy particles with LET∞,Si of approximately 300 keV/μm or more using stacks of CR-39 PNTDs and the HDTV CCD chips. We found that approximately 30% of these high-energy high-LET particles coincided with the position of white defects on the HDTV CCDs in the SM.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S135044871000380X

First Ever Flight Demonstration of Zero Propellant Maneuver(TM) Attitude Control Concept

by on 9 June 2015in Technology Development & Demonstration No comment

This paper presents the results for the first ever flight demonstration of the Zero Propellant Maneuver (ZPM) TM attitude control concept. On November 5, 2006, the ZPMTM was used to reorient the International Space Station by 90 degrees without using any propellant. By maneuvering along a pre-planned trajectory which was optimized to take advantage of naturally occurring environmental torques, the Space Station CMGs were maintained within operational limits. The trajectory was obtained from a PseudoSpectral solution to a new optima attitude control problem. With the flight test, the breakthrough capability to simultaneously perform large angle attitude maneuver and momentum desaturation without the need to use thruster was established. The flight implementation did not require any modification to flight software. The approach is applicable to any spacecraft that are controlled by momentum storage devices.

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http://dx.doi.org/10.2514/6.2007-6734

Autonomous docking algorithm development and experimentation using the SPHERES testbed

by on 9 June 2015in Technology Development & Demonstration No comment

The MIT Space Systems Laboratory (SSL) has developed a testbed for the testing of formation flight and autonomous docking algorithms in both 1-g and microgravity environments. The SPHERES testbed consists of multiple micro-satellites, or Spheres, which can autonomously control their position and attitude. The testbed can be operated on an air table in a 1-g laboratory environment, in NASA"s KC-135 reduced gravity research aircraft and inside the International Space Station (ISS). SPHERES launch to the ISS is currently manifested for May 19 2004 on Progress 14P. Various types of docking maneuvers, ranging from docking with a cooperative target to docking with a tumbling target, have been developed. The ultimate objective of this research is to integrate the different algorithms into one program that can assess the health status of the target vehicle, plan an optimal docking maneuver while accounting for the existing constraints and finally, execute that maneuver even in the presence of simulated failures. In this paper, results obtained to date on the ground based air table using the initial version of the program will be presented, as well as results obtained from microgravity experiments onboard the KC-135.

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http://dx.doi.org/10.1117/12.547430

Demonstration of Electromagnetic Formation Flight and Wireless Power Transfer

by on 9 June 2015in Technology Development & Demonstration No comment

The Resonant Inductive Near-Field Generation System uses a single set of hardware to perform both electromagnetic formation flight and wireless power transfer operations in a six-degree-of-freedom microgravity environment. The system serves primarily as a test bed for control algorithms, and operation onboard the International Space Station allows for more complicated and realistic algorithms to be tested. This offers an advantage compared with the restrictive, dynamic environment of flat floor facilities on the ground or the limited duration of reduced-gravity flights. The hardware attaches to the formation flight-test facility inside the International Space Station referred to as the Synchronized Position Hold, Engage, Reorient, Experimental Satellites. Design and development of the support hardware and electronics, as well as some test results from ground testing, a parabolic flight campaign, and preliminary test sessions on the International Space Station are presented. Ground tests and the parabolic flight campaign results include preliminary inertia and thruster characterization of the combined Resonant Inductive Near-field Generation System/Synchronized Position Hold, Engage, Reorient, Experimental Satellites assembly. Preliminary on-orbit test results include data demonstrating wireless power transfer of approximately 30% and qualitative observations of electromagnetic formation flight with one Resonant Inductive Near-Field Generation System unit restrained and the other unit free floating.

Related URLs:
http://dx.doi.org/10.2514/1.A32940

A miniature microcontroller curve tracing circuit for space flight testing transistors

by on 9 June 2015in Technology Development & Demonstration No comment

This paper describes a novel miniature microcontroller based curve tracing circuit, which was designed to monitor the environmental effects on Silicon Carbide Junction Field Effect Transistor (SiC JFET) device performance, while exposed to the low earth orbit environment onboard the International Space Station (ISS) as a resident experiment on the 7th Materials on the International Space Station Experiment (MISSE7). Specifically, the microcontroller circuit was designed to operate autonomously and was flown on the external structure of the ISS for over a year. This curve tracing circuit is capable of measuring current vs. voltage (I-V) characteristics of transistors and diodes. The circuit is current limited for low current devices and is specifically designed to test high temperature, high drain-to-source resistance SiC JFETs. The results of each I-V data set are transmitted serially to an external telemetered communication interface. This paper discusses the circuit architecture, its design, and presents example results.

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http://scitation.aip.org/content/aip/journal/rsi/86/2/10.1063/1.4908163

Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule

by on 9 June 2015in Technology Development & Demonstration No comment

Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/20364264