The design and feasibility of a 10 mN chemical space propulsion thruster

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 103-108).This thesis discusses the design of a ten milli Newton chemical propulsion system for providing approximately 200 m/s delta velocity to a five kg satellite. The nozzle is the focus of the experimental work, which involves building and testing ten 20x upscale 2D nozzles. The ten nozzles involve three classes, an ideal contour for 2D expansion, a 15 degree cone, and the ideal contour widened for the displacement thickness, each cut to 25%, 50% and 100% axial lengths. The last nozzle is a 100% axial length, ideal contour class, that is twice the thickness to see the effect of end wall boundary layer growth. The nozzles are tested in the MIT Space Propulsions Lab's vacuum chamber at sub atmospheric chamber pressures to match the throat Reynolds number with the micro nozzles. For the purposes of this specific design the Reynolds number is on the order of a 1,000; however, tests are done over a range of 200-1,400 to provide additional data to the community. The nozzle's coefficient of thrust efficiency is approximately 80% for Reynolds numbers greater than a 1,000 and the data suggest the efficiency drops below 50% at 200. The error becomes significant at low Reynolds number due to pressure measurement error, which reduces the quality of the results. The entire system is compared to the state-of-the-art in milli Newton class space propulsion systems and recommendations are given for propellant choice, valve and pump designs, and thermal management. For small delta velocity missions ( 200 m/s), a monopropellant chemical propulsion system is advantageous to current electric propulsion and cold gas thrusters due to the low system mass.by Alexander Robert Bruccoleri.S.M

Fabrication of high-throughput critical-angle X-ray transmission gratings for wavelength-dispersive spectroscopy

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from department-submitted PDF version of thesis.Includes bibliographical references (p. 231-249).The development of the critical-angle transmission (CAT) grating seeks both an order of magnitude improvement in the effective area, and a factor of three increase in the resolving power of future space-based, soft x-ray spectrometers. This will enhance further studies of the universe's make-up, such as the composition of the intergalactic medium, black holes, neutron stars and other high energy sources. Conceptually, x-rays are reflected in the device off nanoscale silicon grating bars at shallow angles, such that the diffraction orders are at the specular reflection angle, which is designed to be less than the critical-angle for total external reflection. This blazing effect boosts the efficiency of the device; however, the grating bars are required to form very deep channels to reflect all the incoming x-rays at shallow angles. Previous attempts to fabricate the grating were done with wet potassium hydroxide (KOH) etching of silicon. This process successfully fabricated small areas of grating and enabled a successful demonstration of the soft x-ray diffraction efficiency. However, the open-area fraction was limited to below 20 percent for four micron-tall CAT grating bars due to diagonal etch stops in the silicon crystal lattice. This limitation prevents the past fabrication technique from achieving the desired open-area fraction for a future x-ray observatory. New nanofabrication techniques are presented that can lead to CAT gratings with an open-area fraction in excess of 50 percent. Specifically, three major nanofabrication processes were developed and are described in detail; a two-dimensional, thermal, silicon dioxide mask, an integrated plasma-etch process to create free-standing, ultra-high aspect ratio gratings, and a polishing process to smooth the grating sidewalls. The two-dimensional mask was used to develop a record-performance deep reactive-ion etch (DRIE) for ultra-high aspect ratio gratings. The mask is the integration of a 5 micron and 200 nanometer-pitch grating into a single layer of 300 nanometer-thick thermal silicon dioxide. It spans 5 centimeters on a side, with vertical sidewalls, and is cleanable which enables consistent high quality etches. Experiments with chrome and polymer masking materials for DRIE are also presented. The DRIE was critical for the integrated process, which combined two plasma-etch processes on the front and back side of a silicon-on-insulator wafer. DRIE is not significantly affected by the silicon crystal orientation and therefore avoids the open-area restrictions of wet etching. The result of the process was a free-standing grating with a period of 200 nanometers, a depth of four microns, and a span of three centimeters. These free-standing gratings exceed the state-of-the-art by more than a factor of two in aspect ratio at the nanoscale. The sidewall roughness is one shortcoming of DRIE, which is often greater than 4 nanometers RMS, and it needs to be approximately one nanometer to efficiently reflect soft x-rays. To address this, the world's first reported nanoscale polishing process has been developed to smooth the sidewalls of DRIE'd, ultra-high aspect ratio silicon. This process utilizes potassium hydroxide etching, an anisotropic etch of single crystal silicon. Specifically, the [111] planes etch approximately 100 times slower than the non-[111] planes. A novel alignment technique is presented to align the CAT grating pattern to the [111] silicon planes to within 0.2 degrees. This precise alignment enables KOH to etch away sidewall roughness and slowly widen the channels without fully destroying the structure. The result of polishing was a reduction in sidewall roughness to approximately 1 nm RMS, while decreasing the widths of the grating bars. In addition to the nanofabrication developments, this work provides a preliminary analysis of launching and deploying CAT gratings in space. The nanofabrication developments are focused towards the CAT grating; however, they have other applications as well. High quality masks have applications in MEMS structures and photonic devices. The free-standing structure as a stand-alone device has applications such as neutral mass spectroscopy, ultraviolet filtration, and x-ray phase contrast imaging. The polishing process is valuable to numerous optical applications where smooth sidewalls are critical, as well as filtration techniques which seek to maximize open-area.by Alexander Robert Bruccoleri.Ph.D

SDRS—an algorithm for analyzing large-scale dose–response data

Summary: Dose–response information is critical to understanding drug effects, yet analytical methods for dose–response assays cannot cope with the dimensionality of large-scale screening data such as the microarray profiling data. To overcome this limitation, we developed and implemented the Sigmoidal Dose Response Search (SDRS) algorithm, a grid search-based method designed to handle large-scale dose–response data. This method not only calculates the pharmacological parameters for every assay, but also provides built-in statistic that enables downstream systematic analyses, such as characterizing dose response at the transcriptome level

Decatransin, a novel natural product inhibiting protein translocation at the Sec61/SecY translocon

A new cyclic decadepsipeptide was isolated from Chaetosphaeria tulasneorum with potent bioactivity on mammalian and yeast cells. Chemogenomic profiling in S. cerevisiae indicated that the Sec61 translocon, the machinery for protein translocation and membrane insertion at the endoplasmic reticulum, is the target. The profiles were similar to those of cyclic heptadepsipeptides of a distinct chemotype (HUN-7293/cotransin) that had previously been shown to inhibit cotranslational translocation at the mammalian Sec61 translocon. Unbiased, genome-wide mutagenesis followed by full-genome sequencing in both fungal and mammalian cells identified dominant mutations in Sec61p/Sec61α1 to confer resistance. Most, but not all, of these mutations affected inhibition by both chemotypes, despite an absence of structural similarity. Biochemical analysis confirmed inhibition of protein translocation into the endoplasmic reticulum of both co- and posttranslationally translocated substrates by both chemotypes, demonstrating a mechanism independent of a translating ribosome. Most interestingly, both chemotypes were found to also inhibit SecYEG, the bacterial Sec61 homolog. We suggest "decatransin" as the name for this novel decadepsipeptide translocation inhibitor

The First Flight of the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS)

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) sounding rocket experiment launched on July 30, 2021 from the White Sands Missile Range in New Mexico. MaGIXS is a unique solar observing telescope developed to capture X-ray spectral images, in the 6 - 24 Angstrom wavelength range, of coronal active regions. Its novel design takes advantage of recent technological advances related to fabricating and optimizing X-ray optical systems as well as breakthroughs in inversion methodologies necessary to create spectrally pure maps from overlapping spectral images. MaGIXS is the first instrument of its kind to provide spatially resolved soft X-ray spectra across a wide field of view. The plasma diagnostics available in this spectral regime make this instrument a powerful tool for probing solar coronal heating. This paper presents details from the first MaGIXS flight, the captured observations, the data processing and inversion techniques, and the first science results.Comment: 20 pages, 18 figure

Transcriptional Profiling of the Dose Response: A More Powerful Approach for Characterizing Drug Activities

The dose response curve is the gold standard for measuring the effect of a drug treatment, but is rarely used in genomic scale transcriptional profiling due to perceived obstacles of cost and analysis. One barrier to examining transcriptional dose responses is that existing methods for microarray data analysis can identify patterns, but provide no quantitative pharmacological information. We developed analytical methods that identify transcripts responsive to dose, calculate classical pharmacological parameters such as the EC50, and enable an in-depth analysis of coordinated dose-dependent treatment effects. The approach was applied to a transcriptional profiling study that evaluated four kinase inhibitors (imatinib, nilotinib, dasatinib and PD0325901) across a six-logarithm dose range, using 12 arrays per compound. The transcript responses proved a powerful means to characterize and compare the compounds: the distribution of EC50 values for the transcriptome was linked to specific targets, dose-dependent effects on cellular processes were identified using automated pathway analysis, and a connection was seen between EC50s in standard cellular assays and transcriptional EC50s. Our approach greatly enriches the information that can be obtained from standard transcriptional profiling technology. Moreover, these methods are automated, robust to non-optimized assays, and could be applied to other sources of quantitative data

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS)

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket instrument that flew on July 30, 2021 from the White Sands Missile Range, NM. The instrument was designed to address specific science questions that require differential emission measures of the solar soft X-ray spectrum from 6 – 25[Formula: see text]Å(0.5 – 2.1[Formula: see text]keV). MaGIXS comprises a Wolter-I telescope, a slit-jaw imaging system, an identical pair of grazing incidence paraboloid mirrors, a planar grating and a CCD camera. While implementing this design, some limitations were encountered in the production of the X-ray mirrors, which ended up as a catalyst for the development of a deterministic polishing approach and an improved meteorological technique that utilizes a computer-generated hologram (CGH). The opto-mechanical design approach addressed the need to have adjustable and highly repeatable interfaces to allow for the complex alignment between the optical sub-assemblies. The alignment techniques employed when mounting the mirrors and throughout instrument integration and end-to-end testing are discussed. Also presented are spatial resolution measurements of the end-to-end point-spread-function that were obtained during testing in the X-ray Cryogenic Facility (XRCF) at NASA Marshall Space Flight Center. Lastly, unresolved issues and off-nominal performance are discussed

The First Flight of the Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS)

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) sounding rocket experiment launched on 2021 July 30 from the White Sands Missile Range in New Mexico. MaGIXS is a unique solar observing telescope developed to capture X-ray spectral images of coronal active regions in the 6–24 Å wavelength range. Its novel design takes advantage of recent technological advances related to fabricating and optimizing X-ray optical systems, as well as breakthroughs in inversion methodologies necessary to create spectrally pure maps from overlapping spectral images. MaGIXS is the first instrument of its kind to provide spatially resolved soft X-ray spectra across a wide field of view. The plasma diagnostics available in this spectral regime make this instrument a powerful tool for probing solar coronal heating. This paper presents details from the first MaGIXS flight, the captured observations, the data processing and inversion techniques, and the first science results