TECHNOLOGY AREAS: Air Platform, Information Systems, Battlespace, Weapons

ACQUISITION PROGRAM: Office of Naval Research Code 352: Railgun Innovative Naval Prototype (INP)

OBJECTIVE: Develop a validated analysis software package that can be used as a system requirement estimation tool to aid the aviation/missile development community in establishing real-world probabilities of encounter various weather related events. This tool will be able to predict the probability of encounter for a wide variety of weather events and phenomena. As weather databases tend to be large and contain an extensive amount of data, the problem of data synthesis and extraction can quickly become unmanageable. The development of the global adverse weather encounter probabilities therefore needs to employ analyses techniques and innovative data extraction strategies to make the currently available satellite databases amenable for the end user. These large databases need to be distilled in such a way to create the aloft hydrometeor and sand/dust profiles that will be employed for subsequent system performance estimates. Such events/phenomena could include: rain, global cloud cover, hail, ice, sand/dust, and volcanic ash. This task will significantly enhance affordability for current and future aviation and missile systems by reducing costs due to component over-design, while simultaneously assisting in verifying the performance, versatility, and durability of materials in realistic environments. Over-testing in unrealistic weather scenarios, due to lack of understanding of the real-world events drive higher component costs for radomes, shrouds, fairings, window anti-reflection coatings and seals, helicopter blades and even booster cases. As the "all weather" Navy unfolds, research tools such as this are critical for proper in-theater all-weather capabilities for all flight systems and can provide the opportunity to hasten the availability of this new technology to the operational Navy.

DESCRIPTION: The event characterization must be global in coverage to include oceanic environments as a function of geographical latitude and altitude. This code will provide the aviation (helicopter and aircraft) and missile system integrators with an accurate tool needed to properly link weather event ground testing to real-world flight environments. This tool will also be valuable to aviation parts manufactures such as window and rotorblade designers to estimate a more realistic flight environment for their products.

In recent years we have pushed the ground test facilities that were developed in the 1960�s and 1970�s to near their limits. There currently exist significant constraints on these facilities to "match" flight test weather event levels. These limitations make it all the more important when the system integrator must extrapolate the ground test results nearly an order of magnitude to match flight test data. Because of this, understanding the real-world weather environment becomes essential if the system component is not to be significantly over-designed. Coupled to this is the speed and performance of missiles, high-speed aircraft, and helicopter rotor systems currently in development, we are pushing the performance envelope beyond what the standard materials commonly used in older systems can deliver. These legacy materials are now no longer acceptable and new materials are currently under development. Due to the lack of experience utilizing these newer materials however, it is essential that the proper flight environment be tested so that realistic flight performance can be predicted.

The definition and probability of weather events at various latitudes will form primary core of the program. Such information is calculated and measured in the meteorological community. Radar data has established both the particle size and size distribution, as functions of ground track, altitude, and precipitation type and shape. The code will be able integrate these large data structures into a compact form which can then be utilized in establishing various weather scenarios that can predict the incident mass flux and integrated mass flux for a generic flight system given the trajectory or flight plan as input. Weather encounter probabilities can be accomplished through hind-casting methods, development of archetypical weather realizations tied to ground rain fall rates, or other such methods. Methods that can extract the probabilities of cloud cover over global regions are also of interest. The code will then be able to perform numerous simulations across multiple trajectories to determine the worse case launch point or flight path for a given weather event. The code will also have a flexible output file capability such that the Navy can quickly utilize this data in various other types of system analysis software currently in use.

The code shall be able to provide various performance metrics that will enable the engineer to rapidly assess how the weather environment changes as a function of its various input parameters. The highest-level of the software architecture should be able to perform hundreds of hands-free trade studies in order to assess the most optimal path for the problem at hand. A user interface should incorporate a Graphical User Interface (GUI) for ease of use. The software needs to run on personal computers running Microsoft operating systems.

The Navy intends to promote exploration into "all-weather" system design as an enabling technology for aircraft and weapon platforms. It is also the intent to develop software technologies as innovative research tools to aid the design and testing processes for multiple air/weapon platforms across DoD and private sector agencies. Software tools provide the opportunity to improve overall platform design and experimental test validation, thus enhancing system R&D quality and platform life-cycle costs.

PHASE I: Develop a software hierarchy as to what methodologies, codes, techniques, and weather databases will be used to deliver the weather assessment and optimization software. The elements that must be present in the software include:
� Trajectory/flight path simulation (altitude, velocity, as a function of time)
� A library of weather events (example: particle type, size, distribution, as a function of altitude and ground track, etc.) developed through innovative extraction methods utilizing current databases with rigorous validation to measured weather events.
� The probabilities of encounter associated with each event as a function of latitude or global position based on novel statistical assessments of the large weather database information.
� A architecture to perform multiple runs and assess worst case launch points/flight paths with respect to given or random weather formations.
� Simplified and flexible input and output capabilities to interface with other codes.
� Output plotting routines such that large amounts of data can be quickly assessed with statistical significance.

PHASE II: Provide a completed and integrated weather encounter software package enabling more accurate definitions of the weather space enabling the end user to perform more accurate analyses and optimization of aviation components. The code shall be fully checked and benchmarked against measured storm and event data with the results presented. A full set of user documentation shall be provided which will enable end users to fully utilize the capabilities of the software. The checkout cases utilized in validating the software during the Phase I and Phase II efforts will be detailed.

PHASE III: Enable Government, major aviation/missile system integrators, and subsystem component developers to produce superior aviation and flight systems with sufficient design margin to make advanced systems "all-weather" capable. The completed software package could be marketed as an enabling technology to predict realistic flight environments for suppliers of aviation parts to verify/validate their part�s performance. Products that would derive benefit from this technology include but are not limited to: helicopter blades, missile radomes, aircraft antennas, aircraft windows, seals, infrared windows, and anti-reflection and radar absorbing coatings. The resulting weather definitions as integrated into analysis software would provide significant benefit to commercial aviation systems and military planners if the final system was linked to real-time meteorological databases providing up to the minute situational awareness. These benefits could be recognized in subsonic flight environments to support erosion and impact damage assessments on coatings, optical windows, aircraft wing/blade leading edges, as well cockpit canopies/windows.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: It is anticipated that the weather definition capability developed under this program will directly lead to the development of real-time vehicle assessments for flight operations through adverse weather conditions. The commercial applicability of this technology will have directly applicable to missiles, aircraft, rotorcraft, and unmanned aerial systems (UAS). Organizations such as the Federal Aviation Administration (FAA), all elements of the Department of Defense (DoD), and the National Oceanic and Atmospheric Administration (NOAA), would all directly benefit from this technology. The ability to estimate the impact of weather on any flight system, to include both real-time data and weather forecasting, will enable just-in-time estimation of potential flight hazards including the likelihood of wind shear and atmospheric turbulence required by both commercial aviation and UAS vehicles. The product developed under this program will also enable a significant advancement to radar and seeker designs as it can be utilized in order to understand the power requirements to operate in adverse conditions. Currently the power requirements for these systems high, therefore producing a significant cost driver to the overall system designs. By utilizing high-fidelity 3D weather realizations validated by both ground and satellite truth data, the seeker and imaging requirements are expected to be appreciably reduced resulting in significant system cost and weight savings.

REFERENCES:
1. Microphysics of Clouds and Precipitation (Atmospheric and Oceanographic Sciences Library) by H.R Pruppacher, J.D. Klett, publisher: Springer; 1 edition (December 31, 1996), ISBN: 079234409X

2. Short Course in Cloud Physics, Third Edition (International Series in Natural Philosophy) by M.K. Yau, R.R. Rogers, publisher: Butterworth-Heinemann; 3 edition (January 1, 1989), ISBN: 0750632151

3. Murray, A. L., Russell, G. W., "Coupled Aeroheating/Ablation Analysis for Missile Configurations," Journal of Spacecraft and Rockets, Vol. 39, No 4, April 2002.

4. A. L. Murray. User�s Manual for the Aeroheating and Thermal Analysis Code (ATAC05). ITT Industries Document Number ATAC-05-001, January 2005, pg 34-35.

5. Marshall, T. S., Palmer, W. M. K., "The Distribution of Raindrops With Size," J. Meteor. 5, 165-166, 1948.

6. Harris, Daniel C., "Materials for Infrared Windows and Domes," SPIE Optical Engineering Press, Bellingham, Washington, 1999.

7. W. G. Reinecke and G. D. Waldman. Shock Layer Shattering of Cloud Drops in Reentry Flight. Technical Report 75-152, AIAA, January 1975.

8. A. A. Ranger and J. A. Nicholls., Aerodynamic shattering of liquid drops. AIAA Journal, 7(2):285-290, February 1969.

9. N. A. Jaffe. Particle Deceleration and Heating in a Hypersonic Shock Layer. Technical Report TN-73-18, Acurex, February 1973.

10. Letson, K.N., "Influence of Fiber Loading on the Rain Erosion Behavior of Polytetraflourethylene (PTFE)," Proceedings of the 5th International Conference on Erosion by Solid and Liquid Impact, 16-1, 3-6, September 1979.

11. Grantham, D.D., Gringorten I.I., et. al., "Water Vapor, Precipitation, Clouds and Fog: Chapter 16, 1983 Revision, Handbook of Geophysics and Space Environments," AFGL-83-0181, Environmental Research Papers, No. 845, 18 July 1983, Meteorology Division, Project 6670, Air Force Physics Laboratory, Hanscom AFB, Massachusetts 01731.

12. Tattleman, P., Grantham, D.D., "Northern Hemisphere Atlas of 1-Minute Rainfall Rates, " AFGL-TR-83-0267, Air Force Surveys in Geophysics, No. 444, Air Force Geophysics Laboratory, Air Force Systems Command, U.S. Air Force, Hanscom AFB, Massachusetts, October 4, 1983.

13. Tattleman, P., Grantham, D.D., "Southern Hemisphere Atlas of 1-Minute Rainfall Rates, " AFGL-TR-83-0285, Air Force Surveys in Geophysics, No. 443, Air Force Geophysics Laboratory, Air Force Systems Command, U.S. Air Force, Hanscom AFB, Massachusetts, October 21, 1983.

14. MIL-HDBK-310, Global Climatic Data for Developing Military Products, 23 June 1997. pp 70-71.

15. Willis, P.T., Tattleman, P., Drop-Size Distributions Associated with Intense Rainfall, Journal of Applied Meteorology, Volume 28, January 1989.

KEYWORDS: Weather definition; meteorology; optimization software; Monte Carlo simulations; particle demise; rain/snow/ice encounters; trajectory shaping; graphical user interface

Questions may also be submitted through DoD SBIR/STTR SITIS website.