SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 3 - February 10, 2006

73 NUCLEAR PHYSICS
Includes nuclear particles; and reactor theory.

For space radiation see 93 Space Radiation.

For atomic and molecular physics see 72 Atomic and Molecular Physics.

For elementary particle physics see 77 Physics of Elementary Particles and Fields.

For nuclear astrophysics see 90 Astrophysics.

20060005028 Lockheed Martin Corp., Bethesda, MD, USA

Comparison of Direct and Indirect Gas Reactor Brayton Systems for Nuclear Electric Space Propulsion

Postlethwait, M.; DiLorenzo, P.; Belanger, S.; Ashcroft, J.; May 02, 2005; 16 pp.; In English Report No.(s): DE2005-850545; LM-05K050; No Copyright; Avail.: Department of Energy Information Bridge

Gas reactor systems are being considered as candidates for use in generating power for the Prometheus-1 spacecraft, along with other NASA missions as part of the Prometheus program.

Gas reactors offer a benign coolant, which increases core and structural materials options. However, the gas coolant has inferior thermal transport properties, relative to other coolant candidates such as liquid metals. This leads to concerns for providing effective heat transfer and for minimizing pressure drop within the reactor core.

In direct gas Brayton systems, i.e. those with one or more Brayton turbines in the reactor cooling loop, the ability to provide effective core cooling and low pressure drop is further constrained by the need for a low pressure, high molecular weight gas, typically a mixture of helium and xenon. Use of separate primary and secondary gas loops, one for the reactor and one or more for the Brayton system(s) separated by heat exchanger(s), allows for independent optimization of the pressure and gas composition of each loop. The reactor loop can use higher pressure pure helium, which provides improved heat transfer and heat transport properties, while the Brayton loop can utilize lower pressure He-Xe. However, this approach requires a separate primary gas circulator and also requires gas to gas heat exchangers.

This paper focuses on the trade-offs between the direct gas reactor Brayton system and the indirect gas Brayton system. It discusses heat exchanger arrangement and materials options and projects heat exchanger mass based on heat transfer area and structural design needs. Analysis indicates that these heat exchangers add considerable mass, but result in reactor cooling and system resiliency improvements. NTIS

Brayton Cycle; Nuclear Electric Power Generation; Nuclear Electric Propulsion; Propulsion

20060005310 Edgewood Chemical Biological Center, Aberdeen Proving Ground, MD USA

Correlation of Mass Spectrometry Identified Bacterial Biomarkers From a Fielded Pyrolysis-Gas Chromatography- Ion Mobility Spectrometry Biodetector With the Microbiological Gram Stain Classification Scheme

Snyder, A. P.; Maswadeh, Waleed M.; Wick, Charles H.; Dworzanski, Jacek P.; Tripathi, Ashish; Sep. 1, 2005; 38 pp.; In English Report No.(s): AD-A441189; ECBC-TR-415; No Copyright; Avail.: CASI: A03, Hardcopy

A pyrolysis-gas chromatography-ion mobility spectrometry (Py-GC-IMS) briefcase system can detect and classify deliberately released bioaerosols in outdoor field scenarios. The bioaerosols include Gram-positive spores and Gram-negative bacteria, the MS-2 Escherichia coliphage virus, and ovalbumin (OV) protein species. However, the origin and structural identities of the pyrolyzate peaks observed in the GC-IMS dataspace, their microbiological information content, and taxonomic importance with respect to biodetection have not been determined. The present work interrogates the identities of the peaks by inserting a time-of-flight (TOF) mass spectrometry (MS) system in parallel with the IMS detector through a Tee connection in the GC module. Biological substances, producing ion mobility peaks from the pyrolysis of microorganisms, have been identified by their GC retention times, by matching their electron ionization mass spectra with authentic standards, and by the National Institute of Standards and Technology (NIST) mass spectral database. DTIC

Bacteria; Bioinstrumentation; Biomarkers; Classifications; Detection; Gas Chromatography; Mass Spectroscopy; Microbiology; Mobility; Pyrolysis; Spectrometers

Source: NASA