Code UG Weekly Notes 5-30-02


Physical Sciences Division
Weekly Highlights for Week Ending 5/30/2002

*** Indicates item is appropriate for the HQ senior staff and may appear on the OBPR Web site: http://spaceresearch.nasa.gov

GENERAL

***WAS EINSTEIN WRONG? SPACE STATION RESEARCH MAY FIND OUT: Ultra-precise clocks on the International Space Station and other space missions may determine whether Albert Einstein's Special Theory of Relativity is correct and could dramatically change our understanding of the universe.

This fundamental Physics Press Release was issued on 5/29 and appears on the spaceresearch.nasa.gov web site.

EDUCATION AND OUTREACH

FREE FALL PHYSICS AT THE AMUSEMENT PARKS: In May, microgravity demonstrations were conducted at 3 physics days at the Cedar Point Amusement Park and Six Flags Worlds of Adventure, which are both near the Glenn Research Center. Given the outdoor setting, the primary demonstrations are the (leaking bottle) Weightless Water, and the ever-popular Balloon Buster. A special demonstration at the amusement parks is the Stomach Simulator, where the Microgravity Demonstrator's capillary experiment is used to show what happens to your stomach's contents during the microgravity portion of the rides. For about 10 years, rain or shine, Microgravity Man and his assistants from NASA Glenn and NCMR have annually participated in these informal education opportunities. This year, Microgravity Man was assisted by Eric Baumann, Dick DeLombard, Carol Hodanbosi, John McQuillen, Charles Niederhaus, Dennis Stocker, and co-op Alisha Vachhani.

ISS FLIGHT PROGRAM

TRANSITION FROM IGNITION TO FLAME GROWTH UNDER EXTERNAL RADIATION (TIGER-3D): The purpose of this effort, directed by Dr. T. Kashiwagi of the NIST, is to determine the chemical and physical mechanisms driving the transition of localized ignition to stable flame growth in microgravity. The information obtained will be used for application to fire safety issues in the Space Station. The analysis of data for the eleven experiments conducted in the JAMIC 10 s droptower in November 2001 is recently completed. The effects of the sample thickness on the transition and subsequent flame growth (ignited by a small CO2 laser) were explored with three different thicknesses of the paper sample (60 g/m2, 120 g/m2, and 240 g/m2) and with two PMMA samples (0.2 mm and 0.8 mm). All paper samples ignited and flame growth was observed over both sides of the sample (laser irradiated surface and back side surface). Both PMMA samples were ignitted by pasting a small amount of nitroacetate glue on the irradiated area of the sample surface. However, flame growth was observed only over the irradiated side of the thicker PMMA sample during 10 s test time. Feasibility of the formation of line shaped flame across the sample width shortly after the spotted ignition by the laser was tested for the paper sample and the thin PMMA sample by pasting narrow strips of thin cellulose nitrate across the sample width. The results show that it needs more refinement to generate a line shape flame. Towards designing planned experiments in ISS, a new series of calculations have focused on the effects of external wind velocity on the flame growth pattern from the line-shaped ignition across the sample width initiated at the center part of the paper sample. It is found that four different flame growth patterns depending on the wind velocity ranges. At low velocity (for example, less than 2 cm/s), the initial line shape flame could not be sustained, in particular at its center portion, due to a lack of oxygen support to the flame and eventually two separate small flames traveling upstream along the edges of the sample. The survival of the two edges flames are due to enhanced oxygen transport rate by diffusion from the outer flow to the edge flames. Increasing wind velocity (for example, from 2 cm/s to 8 cm/s), a line shape flame across the sample remains and travels upstream. At a next higher wind velocity (for example, from 8 cm/s to 10 cm/s), three separate flames are formed; one line shape flame traveling upstream and two separate small flames along the sample edges traveling downstream. In the high wind velocity (for example, from 10 cm/s to 20 cm/s), two separate line shaped flames are formed; one travels upstream and the other travels downstream simultaneously. Each wind velocity range to generate the four flame growth patterns would depend on oxygen concentration in the wind, sample type, and sample thickness. Experimentally, the second regime flame pattern of one line shape upstream flame and the fourth regime flame pattern of the two simultaneous line shape flames were observed. However, the first and the third regimes of flame patters have not been observed yet due to a limited number of tests conducted in microgravity.


LTMPF MOCK-UP COMPLETED FOR SIZING ELECTRONIC CABLES: The LTMPF dewar actual-size mock-up has been completed by the electronics contractor Design-Net. This mock-up will be used to fashion cable runs on the dewar to build the correct size of each cable.

SCIENCE HIGHLIGHTS

COMBUSTION SCIENCE:

DETECTING ONSET OF FIRE IN AIRCRAFT BY EMPLOYING CORRELATION SPECTROSCOPY: This effort is a Small Business Innovation Research (SBIR) Phase II project led by Dr. Kisholoy Goswami of Intelligent Optical Systems, Inc. The objective is the development of fiber-optic based sensors employing correlation spectroscopy for the sensitive detection of marker species indicative of cabin fires. The technique uses Fiber Bragg Gratings (FBGs) to simulate the spectra of marker species and provide the reference for correlation with observed spectra in the probe region. Though submitted to the Aviation Safety subtopic this project is of value to spacecraft fire safety as well. The Principal Investigator recently constructed an FBG modulator which allows tuning the grating to within 5 nm, and also constructed an Erbium-doped fiber laser suitable for detection of CO spectral lines. Four laser lines were selected for CO detection. A multipass cell was constructed for testing the optical system, and using this cell, CO was detected originally at 250 ppm without using modulation or lock-in detection. More recently, the PI used this fiber laser with several different FBGs of varying reflection/transmission ratios and bandwidths. An optimal combination of properties was determined, which now allowed CO detection in a multi-pass cell at about 100 ppm.

FUNDAMENTAL PHYSICS:

FRACTIONS OF ATOMS?: Juha Javanainen and his coauthors have found a remarkable situation that a two-species mixture of cold Fermi-Dirac atoms can obtain. As described recently in the Physics Review Focus on-line news magazine (http://focus.aps.org/v9/st21.html), ultra-cold atoms placed in a periodic confining lattice can have partial numbers of atoms at places in the lattice where 'phase kinks' occur. Studying a two-species FD gas in a 1-D optical lattice coupled to an electromagnetic field with a phase kink, they show that fractional number of atoms will be located at the nodes in the potential. The paper describes how experimenters can set up the experiment and detect the fractional number of atoms at the unique sites in the lattice. The calculation results apply to 2-D and 3-D lattices, as well. Details can be found in the authors' article in Physical Review Letters

UPCOMING EVENTS

Additional meetings and symposia can be found at: http://microgravity.grc.nasa.gov/ugml/ugmltext.htm

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