SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 44, ISSUE 14 - JULY 18, 2006

20 SPACECRAFT PROPULSION AND POWER
Includes main propulsion systems and components, e.g., rocket engines; and spacecraft auxiliary power sources.

For related information see also 07 Aircraft Propulsion and Power, 28 Propellants and Fuels, 15 Launch Vehicles and Launch Operations, and 44 Energy Production and Conversion.

20060019404 Air Force Research Lab., Edwards AFB, CA USA

Health Management Issues and Strategy for Air Force Missiles (POSTPRINT)

Ruderman, Gregory; Nov 2005; 11 pp.; In English Contract(s)/Grant(s): Proj-1011 Report No.(s): AD-A446283; AFRL-PR-ED-TP-2005-272; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446283; Avail.: CASI: A03, Hardcopy

As so-called 'wooden rounds,' which are intended to sit stably in storage for extended periods and then function precisely as desired, at a moment's notice, Air Force missiles would appear to be an ideal application for health monitoring. However, solid rocket motors that serve as the propulsion system for these missiles present a number of unique challenges for the development of integrated vehicle health monitoring systems. Mechanical and chemical complexity, long service lives, aging materials, and designs with small margins are typical for solid motors. But the payoff for health monitoring is extreme as well. Maintaining a healthy and capable fleet-ensuring the viability of the missiles in the fleet while not retiring or destroying good assets before it is necessary could save as much at 50% in costs over a 50-year life cycle. In this paper, a number of the unique aspects of solid rocket motors will be explored, the difficulties and successes in development of sensors and diagnostic systems will be discussed, and a path to further continue development of these systems will be proposed. DTIC

Health; Life (Durability); Missiles; Solid Propellant Rocket Engines

20060019520 Michigan Univ., Ann Arbor, MI USA

Review of Micro-Propulsion Ablative Devices

Keidar, Michael; Boyd, Iain D; Jun 21, 2004; 31 pp.; In English; Original contains color illustrations Contract(s)/Grant(s): F49620-02-1-0084 Report No.(s): AD-A446450; No Copyright; ONLINE: http://hdl.handle.net/100.2/ADA446450; Avail.: CASI: A03, Hardcopy

OUTLINE: * Examples of micro propulsion ablative devices * Fundamentals of ablation * Detailed analysis of specific devices: Micro-Pulsed Plasma Thruster -- Micro-Laser Plasma Thruster -- Micro-Vacuum Arc Thruster * SUMMARY: * Various microthruster technologies based on ablative mechanism were developed. * Self-consistent modeling approach for ablative micro-thrusters was formulated based on a kinetic ablation model and particle plume simulation. * Most extensive validation of the modeling approach was performed for micro-pulsed plasma thruster. Plasma density, surface temperature, ablation rate, ablation profile were compared with experiment. Optimization criteria were formulated for some devices, such as microPPT. DTIC

Ablation; Ablative Materials; Propulsion

20060020274 NASA Langley Research Center, Hampton, VA, USA

Fracture Mechanics Analysis of LH2 Feed Line Flow Liners

James, Mark A.; Dawicke, David S.; Brzowski, Matthew B.; Raju, Ivatury S.; Elliott, Kenny B.; Harris, Charles E.; [2006]; 15 pp.; In English; 47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 1-4 May 2006, Newport, RI, USA; Original contains color and black and white illustrations Contract(s)/Grant(s): WBS 23-104-08-01 Report No.(s): AIAA Paper 2006-1782; Copyright; Avail.: CASI: A03, Hardcopy

Inspections of the Space Shuttle Main Engine revealed fatigue cracks growing from slots in the flow liner of the liquid hydrogen (LH2) feed lines. During flight, the flow liners experience complex loading induced by flow of LH2 and the resonance characteristics of the structure. The flow liners are made of Inconel 718 and had previously not been considered a fracture critical component. However, fatigue failure of a flow liner could have catastrophic effect on the Shuttle engines. A fracture mechanics study was performed to determine if a damage tolerance approach to life management was possible and to determine the sensitivity to the load spectra, material properties, and crack size. The load spectra were derived separately from ground tests and material properties were obtained from coupon tests. The stress-intensity factors for the fatigue cracks were determined from a shell-dynamics approach that simulated the dominant resonant frequencies. Life predictions were obtained using the NASGRO life prediction code. The results indicated that adequate life could not be demonstrated for initial crack lengths of the size that could be detected by traditional NDE techniques. Author

Fracture Mechanics; Crack Propagation; Linings; Failure; Tolerances (Mechanics); Space Shuttle Main Engine; Liquid Hydrogen

Source: NASA