Benjamin Dolgin | RAYTHEON - Academia.edu (original) (raw)

Uploads

Papers by Benjamin Dolgin

Materials and structures technology covers a wide range of technical areas. Some of the most pert... more Materials and structures technology covers a wide range of technical areas. Some of the most pertinent issues for the Astrotech 21 missions include dimensionally stable structural materials, advanced composites, dielectric coatings, optical metallic coatings for low scattered light applications, low scattered light surfaces, deployable and inflatable structures (including optical), support structures in 0-g and 1-g environments, cryogenic optics, optical blacks, contamination hardened surfaces, radiation hardened glasses and crystals, mono-metallic telescopes and instruments, and materials characterization. Some specific examples include low coefficients of thermal expansion (CTE) structures (0.01 ppm/K), lightweight thermally stable mirror materials, thermally stable optical assemblies, high reliability/accuracy (1 micron) deployable structures, and characterization of nanometer level behavior of materials/structures for interferometry concepts. Large filled-aperture concepts will require materials with CTE's of 10(exp 9) at 80 K, anti-contamination coatings, deployable and erectable structures, composite materials with CTE's less than 0.01 ppm/K and thermal hysteresis, 0.001 ppm/K. Gravitational detection systems such as LAGOS will require rigid/deployable structures, dimensionally stable components, lightweight materials with low conductivity, and high stability optics. The Materials and Structures panel addressed these issues and the relevance of the Astrotech 21 mission requirements by dividing materials and structures technology into five categories. These categories, the necessary development, and applicable mission/program development phasing are summarized. For each of these areas, technology assessments were made and development plans were defined.

Infrared Technology Xvii, Dec 1, 1991

Future NASA missions such as the Great Observatories of the 21st Century, will require high dimen... more Future NASA missions such as the Great Observatories of the 21st Century, will require high dimensional stability (i.e., the system's ability to retain geometrical properties related to the system's performance) which will have to be maintained with micron to nanometer accuracy over the 5 to 10 years of mission lifetime. This paper examines the thermodynamic and other mechanisms which limit the dimensional stability of a space system. It is shown that the space system's performance will be limited below 0.1 per million dimensional stability.

Proceedings of Spie the International Society For Optical Engineering, Feb 1, 1992

Calculations are presented of the coefficient of thermal expansion (CTE) of the radius of curvatu... more Calculations are presented of the coefficient of thermal expansion (CTE) of the radius of curvature of the reflector face sheets made of a quasi-isotropic composite. It is shown that, upon cooling, the change of the CTE of the focal distance of the mirror is equal to that of the radius of the curvature of the reflector face sheet. The CTE of the radius of the curvature of a quasi-isotropic composite face sheet depends on both the in-plane and the out-of-plane CTEs. The zero in-plane CTE of a face sheet does not guarantee mirrors with no focal length changes.

Optomechanics and Dimensional Stability, 1991

Infrared Technology XVII, 1991

Concepts and Approaches For Mars Exploration, Jul 1, 2000

The proposed Mars Sample Transfer Chain Architecture provides Planetary Protection Officers with ... more The proposed Mars Sample Transfer Chain Architecture provides Planetary Protection Officers with clean samples that are required for the eventual release from confinement of the returned Martian samples. At the same time, absolute cleanliness and sterility requirement is not placed of any part of the Lander (including the deep drill), Mars Assent Vehicle (MAV), any part of the Orbiting Sample container (OS), Rover mobility platform, any part of the Minicorer, Robotic arm (including instrument sensors), and most of the caching equipment on the Rover. The removal of the strict requirements in excess of the Category IVa cleanliness (Pathfinder clean) is expected to lead to significant cost savings. The proposed architecture assumes that crosscontamination renders all surfaces in the vicinity of the rover(s) and the lander(s) contaminated. Thus, no accessible surface of Martian rocks and soil is Earth contamination free. As a result of the latter, only subsurface samples (either rock or soil) can be and will be collected for eventual return to Earth. Uncontaminated samples can be collected from a Category IVa clean platform. Both subsurface soil and rock samples can be maintained clean if they are collected by devices that are self-contained and clean and sterile inside only. The top layer of the sample is removed in a manner that does not contaminate the collection tools. Biobarrier (e.g., aluminum foil) covering the moving parts of these devices may be used as the only self removing bio-blanket that is required. The samples never leave the collection tools. The lids are placed on these tools inside the collection device. These single use tools with the lid and the sample inside are brought to Earth in the OS. The lids have to be designed impenetrable to the Earth organisms. The latter is a well established art.

Future NASA missions in astrophysics, Earth observation, and solar system exploration that requir... more Future NASA missions in astrophysics, Earth observation, and solar system exploration that require optical communication, optical and infrared imaging, or high precision astrometric measurements impose very stringent demands for the dimensional stability of precision structures and science instrument components. The objective of this paper is to identify the major mechanisms that influence the dimensional behavior of common optomechanical materials, to identify the mechanisms that are important for the proposed missions with critical dimensional stability requirements, and to compare the mission requirements with state-of-the- art material and measurement technologies. This paper discusses the tradeoffs of passive vs. active means of achieving the dimensional stability requirements. The reduction of power consumption and mass, the reliability improvements as a function of the dimensional stability of the structural materials for a typical interferometer are calculated.

Solid State reacton as a new method of amorphous film fabrication was introduced by R. Schwartz a... more Solid State reacton as a new method of amorphous film fabrication was introduced by R. Schwartz and W. L. Johnson in 1983. A thermodynamic explanation for the process given by the original article provides a clue to understanding the forces making the reaction possible. This thesis emphasizes the kinetic approach to the description of the reaction. The movements of the interfaces as a fundamental mechanism of the reaction is suggested. The reaction in La-Au and Ni-Hf multilayers is described. Resistance measurements, TEM and SIMS techniques, and Rutherford backscattering are used to study the process. The thesis contains a proof that the final product of the Solid State Reaction is amorphous. It describes the morphology of the reacting multilayers. The one-dimensional and multi-dimensional processes taking place during the growth are separated. The thesis connects the properties of the reaction with known properties of the "fast diffusion." The phenomenological model for the reaction is introduced. The model consists of a diffusion equation with a new set of boundary conditions. The amorphous layer growth rate in the limit of short time is found to be X = 1-exp(-At) and X = -1/(A-1) + (2at)(' 1/2) in the limit of long time. The "steady state" approximation as a solution to the diffusion equations in the limit of long time is found. to be incorrect. The model shows excellent agreement with the experimental data. *All degree requirements completed in 1984, but degree will be granted in 1985.

National Aeronautics and Space Administration Report, Jun 1, 1993

A superconductive load bearing support without a mechanical contact and vibration damping for cry... more A superconductive load bearing support without a mechanical contact and vibration damping for cryogenic instruments in space is presented. The levitation support and vibration damping is accomplished by the use of superconducting magnets and the 'Meissner' effect. The assembly allows for transfer of vibration energy away from the cryogenic instrument which then can be damped by the use of either an electronic circuit or conventional vibration damping mean.

Robotic drilling and autonomous sample acquisition are considered as the key technology requireme... more Robotic drilling and autonomous sample acquisition are considered as the key technology requirements in future planetary or small body exploration missions. Core sampling or subsurface drilling operation is envisioned to be off rovers or landers. These supporting platforms are inherently flexible, light, and can withstand only limited amount of reaction forces and torques. This, together with unknown properties of sampled materials, makes the sampling operation a tedious task and quite challenging. This paper highlights the recent advancements in the sample acquisition control system design and development for the in situ scientific exploration of planetary and small interplanetary missions.