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Wide-angle Fizeau interferometer spacecraft testbed
Future spaceborne interferometric arrays must meet stringent optical performance and tolerance requirements while exhibiting modularity and acceptable manufacture and integration cost levels. The Massachusetts Institute of Technology (MIT) Adaptive Reconnaissance Golay-3 Optical Satellite (ARGOS) is a wide-angle Fizeau interferometer spacecraft testbed designed to address these research challenges. Designing a space-based stellar interferometer, which requires tight tolerances on pointing and alignment for its apertures, presents unique multidisciplinary challenges in the areas of structural dynamics, controls, and multiaperture phasing active optics. In meeting these challenges,emphasis is placed on modularity in spacecraft subsystems and optics as a means of enabling expandability and upgradeability. A rigorous theory of beam-combining errors for sparse optical arrays is derived and flown down to the design of various subsystems. A detailed elaboration on the optics system and control system is presented based on the performance requirements and beam-combining error tolerances. The space environment is simulated by floating ARGOS on a frictionless airbearing that enables it to track both fast and slow moving targets.
Electromagnetic Formation Flight
Using electromagnetics for relative spacecraft formation flight
Electromagnetic Formation Flight (EMFF) investigates the concept of using electromagnets coupled with reaction wheels in place of more traditional propulsion systems to control the positions and attitudes of a number of spacecraft in close proximity. Unlike traditional propulsion systems, which use exhaustible propellants that often limit lifetime, the EMFF system uses solar power to energize a magnetic field. The Space Systems Laboratory is exploring this concept by developing dynamics and control models as well as an experimental testbed for their validation. The magnetic fields for EMFF are generated by sending current through coils of wire. The interaction between the magnetic dipoles created is easily understood with a far-field approximation where the separation distance between two vehicles is large compared to the physical size of the dipole. By controlling the dipoles on various vehicles, attraction, repulsion, and sheer forces can be created. Combined with reaction wheels, any desired maneuver can be performed as long as the formation’s center of mass is not required to change. The MIT-SSL has constructed two EMFF testbed vehicles for demonstrating controllability of 2-D formations on a large flat floor. Vehicles are suspended on a frictionless air carriage and are completely self-contained using RF communications, microprocessors, and a metrology system. Liquid Nitrogen maintains cryogenic temperatures and batteries provide the power to the HTS coils. The testbed has demonstrated control of the relative DOFs in open loop and closed loop control using linearized controllers and a nonlinear sliding mode controller. Future tests planned include spin up, steady-state spin and spin down states. Logical follow-on efforts consist of flight tests of EMFF hardware in low Earth orbit.
Exploration of Neighboring Planetary Systems
Optimal design and construction of the Terrestrial Planet Finder
NASA recently issued "A Road Map for the Exploration of Neighboring Planetary Systems (ExNPS)," a study which examined using space interferometry to detect extra-solar Earth-like planets. One of the proposed initiatives in the report is the Terrestrial Planet Finder, an infrared interferometer consisting of a rotating 75 m truss with four linked telescopes. However, long trusses of this sort are notably difficult to deploy and difficult to control. The MIT Space Systems Lab (SSL) is presently investigating various designs of the Terrestrial Planet Finder, most notably a configuration using multiple free-flying independent spacecraft. Such a design avoids the difficult control issues of a structurally-connected interferometer, while adding the advantage of a wide range of variable optical baselines, which would improve detection accuracy. However, independent control of free-flying spacecraft to the required centimeter or lower precision of an interferometer is a daunting issue. Plus, the added mass of propulsion systems and control and power buses make a multiple spacecraft design bigger and more expensive to launch. In cooperation with the TPF team assembled by NASA, SSL is actively comparing the two high-level configurations to determine the optimal for the eventual design and construction of the Terrestrial Planet Finder. In addition, the study provides relevant information to other future space interferometers by assembling a design framework in which design considerations and trade space restraints may be examined early in the design process, thereby saving both time and money.
Interferometry Program Experiment
Investigating the microdynamic behavior of a representative deployable space truss, including the effects of thermally induced disturbances.
IPEX is a NASA Jet Propulsion Laboratory flight experiment which investigates the microdynamic behavior of a representative deployable space truss, including the effects of thermally induced disturbances. It flew on STS-85 on the Space Shuttle Discover in early August 1997, as a secondary payload on the ASTRO-SPAS free-flying telescope carrier. IPEX consists of a 2.3 m long deployable boom, one end of which is fixed by six struts directly to the structural nodes of ASTRO-SPAS. On-orbit, the truss will undergo microdynamic modal tests. In addition, its accelerometer sensors will "listen" for potential thermal snaps, as the structure flies in and out of Earths shadow. The objectives of the experiment are to assess whether thermal snap will occur for a preloaded jointed structure, and whether such a boom will satisfy the dynamic and thermal stability requirements for precision interferometry. Other main goals of the IPEX project are to validate ground test and modeling techniques. The MIT SSLs work to date on IPEX has focused on predicting the boom response to the disturbance from the Astro-SPAS carriers background noise levels, and to a potential thermal creak disturbance. JPL has a web page with more information about IPEX.
Harvesting and re-using valuable components from retired, nonworking satellites in GEO
The goal of the Phoenix program is to develop and demonstrate technologies to cooperatively harvest and re-use valuable components from retired, nonworking satellites in GEO and demonstrate the ability to create new space systems at greatly reduced cost. Phoenix seeks to demonstrate around-the-clock, globally persistent communication capability for warfighters more economically, by robotically removing and re-using GEO-based space apertures and antennas from de-commissioned satellites in the graveyard or disposal orbit. The Phoenix program envisions developing a new class of very small ‘satlets,’ similar to nano satellites, which could be sent to the GEO region more economically as a “ride along” on a commercial satellite launch, and then attached to the antenna of a non-functional cooperating satellite robotically, essentially creating a new space system. A payload orbital delivery system, or PODS, will also be designed to safely house the satlets for transport aboard a commercial satellite launch. A separate on-orbit ‘tender,’ or satellite servicing satellite is also expected to be built and launched into GEO. Once the tender arrives on orbit, the PODS would then be released from its ride-along host and link up with the tender to become part of the satellite servicing station’s ‘tool belt.’ The tender plans to be equipped with grasping mechanical arms for removing the satlets and components from the PODS using unique space tools to be developed in the program.
The mission of Skolkovo Tech (SkTech) will be to educate students, advance knowledge, and foster innovation in order to address critical scientific, technological, and innovation challenges and gaps facing Russia and the world. MIT will provide assistance in the creation of the initial academic Master’s and PhD degree programs, in each of the Science and Technology Programs. The second major component of the SkTech concept besides education is the establishment of Research Centers (RCs) in the five following areas: Biomedical Science and Technology, Space Science and Technology, Nuclear Science and Technology, Energy Science and Technology, Information Science and Technology. Finally, the third core element of SkTech will be an integral structure to foster and link research and education with innovation and entrepreneurship through the establishment of the Center for Entrepreneurship and Innovation (CEI), which MIT will also assist in creating. Within this initiative, the MIT SSL will propose a mission concept study for a lunar far-side radio observatory optimized to observe the neutral hydrogen 21-cm emission from the intergalactic medium during the dark ages of cosmic structure formation and the early stages of cosmic reionization.
Space Logistics Project
Research on lifecycle impacts of resource logistics on space exploration.
The Space Logistics Project broadly researches the lifecycle impacts of resource logistics on space exploration. Future beyond low-Earth orbit exploration is expected to follow an integrated campaign model involving the reuse of elements over long durations with limited resupply opportunities, a significant change from the single-mission model of Apollo. Planning for this type of exploration requires advancements in both the macro-logistics of mission design and the micro-logistics of managing resources at the exploration site. Past efforts within the Space Logistics Project include a field study to the Haughton-Mars Project Research Station in the high Canadian Arctic to investigate logistics in an analog extreme environment, development of Rule-Based Analytic Asset Management for Space Exploration Systems (RAMSES) - an RFID tagging system for micro-logistics successfully evaluated in a micro-gravity test flight, an architectural study for in-situ resource utilization (ISRU) systems for oxygen production on the lunar surface, and development of SpaceNet - an open source simulation tool to evaluate logistics in exploration campaigns ranging from the International Space Station, near-Earth asteroid missions, lunar outpost build-up, and flexible exploration of Mars. Present and future efforts seek to extend simulation and planning tools to capture independent actors of multi-national and commercial partnerships in collaborative exploration architectures and a focused study of sustainable habitation with high loop closure Environmental Control and Life Support Systems (ECLSS) as a key driver of logistics demands.
A prototype vehicle to develop hopping GNC software and operational experience, as part of a Google Lunar X-Prize (GLXP) collaboration with Draper Laboratory.
The Terrestrial Artificial Lunar And Reduced gravIty Simulator (TALARIS) project has designed, built, and tested a prototype lunar hopping vehicle, which operates in an Earthside lab facility using dual propulsion systems. An air-breathing propulsion system uses electric ducted fans to offset Earth's high gravity by delivering thrust equal to 5/6 of the vehicle's weight, and provides an environment dynamically similar to the one encountered on the Moon. The second propulsion system uses nitrogen thrusters to emulate the behavior of impulsive engines, such as would be used on a space vehicle. This arrangement allows for testing of GNC technologies and operational methods on the Earth. The TALARIS project is a collaboration between Draper Laboratory and MIT as part of the Google Lunar X-Prize (GLXP). Hopping technology and techniques developed as part of this project have the potential to be game-changers in the exploration of planetary surfaces. After the GLXP concludes, the technology will be extended to applications on other planetary surfaces, including potentially Mars, Europa, Titan, and some large asteroids.