2,382 research outputs found
Investigation of a hopping transporter concept for lunar exploration
Performance and dynamic characteristics determined for hopping transporter for lunar exploratio
MIT's interferometer CST testbed
The MIT Space Engineering Research Center (SERC) has developed a controlled structures technology (CST) testbed based on one design for a space-based optical interferometer. The role of the testbed is to provide a versatile platform for experimental investigation and discovery of CST approaches. In particular, it will serve as the focus for experimental verification of CSI methodologies and control strategies at SERC. The testbed program has an emphasis on experimental CST--incorporating a broad suite of actuators and sensors, active struts, system identification, passive damping, active mirror mounts, and precision component characterization. The SERC testbed represents a one-tenth scaled version of an optical interferometer concept based on an inherently rigid tetrahedral configuration with collecting apertures on one face. The testbed consists of six 3.5 meter long truss legs joined at four vertices and is suspended with attachment points at three vertices. Each aluminum leg has a 0.2 m by 0.2 m by 0.25 m triangular cross-section. The structure has a first flexible mode at 31 Hz and has over 50 global modes below 200 Hz. The stiff tetrahedral design differs from similar testbeds (such as the JPL Phase B) in that the structural topology is closed. The tetrahedral design minimizes structural deflections at the vertices (site of optical components for maximum baseline) resulting in reduced stroke requirements for isolation and pointing of optics. Typical total light path length stability goals are on the order of lambda/20, with a wavelength of light, lambda, of roughly 500 nanometers. It is expected that active structural control will be necessary to achieve this goal in the presence of disturbances
MIT Space Engineering Research Center
The Space Engineering Research Center (SERC) at MIT, started in Jul. 1988, has completed two years of research. The Center is approaching the operational phase of its first testbed, is midway through the construction of a second testbed, and is in the design phase of a third. We presently have seven participating faculty, four participating staff members, ten graduate students, and numerous undergraduates. This report reviews the testbed programs, individual graduate research, other SERC activities not funded by the Center, interaction with non-MIT organizations, and SERC milestones. Published papers made possible by SERC funding are included at the end of the report
Active Control Stabilization of High Power Rocket
High power rockets could become dynamically unstable due to outside disturbances after takeoff. The instability is augmented when the rocket is slow off the launch rail, which happens when the thrust-to-weight ratio is less than 5:1. Due to these reasons, the objective of this project was to design and build an active control system that will make sure the rocket follows a straight path all the way to apogee. This will be done through a model-based design approach, in which a 6DOF mathematical model of the flight dynamics will be created
Modular space station phase B extension period executive summary
A narrative summary is presented of technical, programmatic, and planning information developed during the space station definition study extension period. The modular space station is emphasized, but tasks pertaining to shuttle sorties missions and information management advanced development are included. A series of program options considering technical, schedule, and programmatic alternatives to the baseline program are defined and evaluated
Passive-performance, analysis, and upgrades of a 1-ton seismic attenuation system
The 10m Prototype facility at the Albert-Einstein-Institute (AEI) in Hanover,
Germany, employs three large seismic attenuation systems to reduce mechanical
motion. The AEI Seismic-Attenuation-System (AEI-SAS) uses mechanical
anti-springs in order to achieve resonance frequencies below 0.5Hz. This system
provides passive isolation from ground motion by a factor of about 400 in the
horizontal direction at 4Hz and in the vertical direction at 9Hz. The presented
isolation performance is measured under vacuum conditions using a combination
of commercial and custom-made inertial sensors. Detailed analysis of this
performance led to the design and implementation of tuned dampers to mitigate
the effect of the unavoidable higher order modes of the system. These dampers
reduce RMS motion substantially in the frequency range between 10 and 100Hz in
6 degrees of freedom. The results presented here demonstrate that the AEI-SAS
provides substantial passive isolation at all the fundamental mirror-suspension
resonances
Digital controller design: Analysis of the annular suspension pointing system
The annular suspension and pointing system (ASPS) a payload auxiliary pointing device of the space shuttle is briefly described along with the function of the digital controller. The equations of motion of a simplified plan planar model of the ASPS are derived. Results of computer simulations are discussed
Relevance of the weak equivalence principle and experiments to test it: lessons from the past and improvements expected in space
Tests of the Weak Equivalence Principle (WEP) probe the foundations of
physics. Ever since Galileo in the early 1600s, WEP tests have attracted some
of the best experimentalists of any time. Progress has come in bursts, each
stimulated by the introduction of a new technique: the torsion balance, signal
modulation by Earth rotation, the rotating torsion balance. Tests for various
materials in the field of the Earth and the Sun have found no violation to the
level of about 1 part in 1e13. A different technique, Lunar Laser Ranging
(LLR), has reached comparable precision. Today, both laboratory tests and LLR
have reached a point when improving by a factor of 10 is extremely hard. The
promise of another quantum leap in precision rests on experiments performed in
low Earth orbit. The Microscope satellite, launched in April 2016 and currently
taking data, aims to test WEP in the field of Earth to 1e-15, a 100-fold
improvement possible thanks to a driving signal in orbit almost 500 times
stronger than for torsion balances on ground. The `Galileo Galilei' (GG)
experiment, by combining the advantages of space with those of the rotating
torsion balance, aims at a WEP test 100 times more precise than Microscope, to
1e-17. A quantitative comparison of the key issues in the two experiments is
presented, along with recent experimental measurements relevant for GG. Early
results from Microscope, reported at a conference in March 2017, show
measurement performance close to the expectations and confirm the key role of
rotation with the advantage (unique to space) of rotating the whole spacecraft.
Any non-null result from Microscope would be a major discovery and call for
urgent confirmation; with 100 times better precision GG could settle the matter
and provide a deeper probe of the foundations of physics.Comment: To appear: Physics Letters A, special issue in memory of Professor
Vladimir Braginsky, 2017. Available online:
http://dx.doi.org/10.1016/j.physleta.2017.09.02
Flight dynamics and control analysis of the centaur vehicle /atlas/centaur ac-5/
Flight dynamics and control analysis of Centaur vehicl
Design study of a device to simulate the dynamic environment encountered under condi- tions of reduced or zero gravity final report
Design study of reduced or zero gravity environment simulation devic
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