Search Results

A three-year program to develop a Direct Drive Hall Effect Thruster (D2HET) system began 15 months ago as part of the NASA Advanced Cross-Enterprise Technology Development initiative. The system is expected to reduce significantly the power processing, complexity, weight, and cost over conventional low-voltage systems. The D2HET will employ solar arrays that operate at voltages greater than 300V, and will be an enabling technology for affordable planetary exploration. It will also be a stepping-stone in the production of the next generation of power systems for Earth orbiting satellites. This paper provides a general overview of the program and reports the first year's findings from both theoretical and experimental components of the program.

Five type 4 all-composite compressed natural gas (CNG) fuel tanks produced in 1994 were acquired to study the effects of time and environmental exposure. Tank durability was demonstrated by the ability of the tanks to meet or exceed the ANSI/CSA NGV2-20001 standards after 9 years of field service. All tanks passed the NGV2-2000 standard production test requirements, including hydrostatic pressurization testing and standard leak testing. NGV2-2000 design qualification tests were performed on three of the tanks. Design qualification testing included liner and composite mechanical properties, cyclic pressurization, burst testing, and permeation testing as defined by NGV2-2000. All tanks exceeded the NGV2-2000 test requirements and exhibited no adverse effects from time, environment, and cyclic pressurization.

Information on icing flight tests as conducted by the US Army Aviation Engineering Flight Activity is presented. A quick review is conducted of organizations within the US Army that become involved with icing tests. Icing flight test techniques and hardware are shown and discussed. Natural and artificial icing test results are compared. Results and conclusions from previous icing evaluations are shown. The capabilities and limitations of current techniques and systems are discussed. And finally, the process for establishing an airworthiness qualification allowing Army aircraft to fly into a forecast icing environment is presented.

Powder metallurgy (P/M) technology has been identified as a major means for reducing critical element usage for superalloy turbine engine hardware. Utilizing quality and process control, a P/M process has been successfully developed and applied to producing hardware for General Electric's T700 engine used in the Army's Blackhawk helicopter. Utilizing the process, a cost saving of approximately $3000 per engine has been realized and a weight reduction of 40 lbs of superalloy starting material per engine has been achieved. Over 6000 parts have been produced to date and more than 800 engines have been delivered. The high time engine has achieved over 1900 hours operating time. A total of over 200,000 engine operating hours have been accumulated by as-HIP turbine hardware. This engine experience and mechanical property data show that the P/M process is capable of producing high quality reliable hardware for turbine engine applications.

A new generation of Army helicopter crew station is being developed today to meet the challenges of missions required by Army Aviation. The scout mission exemplifies the demands that can be placed upon the aircraft and crew. Scout missions require nap-of-the-earth (NOE) flight during day, night, and adverse weather conditions. Such a requirement demands the highest degree of compatibility between aircraft systems and crew. To meet this challenge, the US Army is currently developing an improved scout helicopter called the Army Helicopter Improvement Program (AHIP). Several enhancements and innovations in crew station design are an integral part of the program. Improvements in the AHIP control/display system reduce head-down cockpit activities allowing more time for head-up flight of the aircraft; especially important during NOE flight.

Off-road vehicle operation requires constant decision-making under great uncertainty. Such decisions are multi-faceted and range from acquisition decisions to operational decisions. A major input to these decisions is terrain information in the form of soil properties. This information needs to be propagated to path planning algorithms that augment them with other inputs such as visual terrain assessment and other sensors. In this sequence of steps, many resources are needed, and it is not often clear how best to utilize them. We present an integrated approach where a mission’s overall performance is measured using a multiattribute utility function. This framework allows us to evaluate the value of acquiring terrain information and then its use in path planning. The computational effort of optimizing the vehicle path is also considered and optimized. We present our approach using the data acquired from the Keweenaw Research Center terrains and present some results.

An automobile seat’s thermal performance can be challenging to quantify since it requires comprehensive human subject testing. Seat manufacturers must rely on subjective ratings to understand how the construction of a seat and its underlying heating and cooling technology may compare to other seats. Other factors may influence seat ratings published by global marketing information services companies (e.g., JD Power and Associates). In particular, occupants may be biased by the vehicle class in which a seat is installed and by how much the contribution of a specific vehicle’s HVAC system performance affects the perception of seat thermal comfort. Therefore, there is a need for an objective testing methodology that does not rely on human participants but is still capable of producing a thermal performance rating in terms of established thermal comfort scales.