Approaches in the determination of plant nutrient uptake and distribution in space flight conditions.

The effective growth and development of vascular plants rely on the adequate availability of water and nutrients. Inefficiency in either the initial absorption, transportation, or distribution of these elements are factors which impinge on plant structure and metabolic integrity. The potential effect of space flight and microgravity conditions on the efficiency of these processes is unclear. Limitations in the available quantity of space-grown plant material and the sensitivity of routine analytical techniques have made an evaluation of these processes impractical. However, the recent introduction of new plant cultivating methodologies supporting the application of radionuclide elements and subsequent autoradiography techniques provides a highly sensitive investigative approach amenable to space flight studies. Experiments involving the use of gel based 'nutrient packs' and the radionuclides calcium-45 and iron-59 were conducted on the Shuttle mission STS-94. Uptake rates of the radionuclides between ground and flight plant material appeared comparable.     

Programmable, multi-purpose opto-electronic sensor system

Optical fibre sensing is becoming increasingly attractive in both the smart structure sphere of interest as well as the medical and industrial concerns. Fibre-optic interferometric sensors can be designed as compact and robust transducers. In general, the transduction mechanism involves the phase modulation of coherent or monochromatic light propagating through a fibre-optic cable, and detecting the changes in the energy associated with this phase change. Sensors based on this technique can generally be configured to be quite sensitive and measurements of a wide variety of physical parameters are achievable. Intrinsic features of optical fibres, such as immunity to electromagnetic interference, flexibility, thinness, strength and weight, make this ideal for sensor technology. In the process of developing fibre-optic sensors for laboratory experimentation, as well as generalised research, an appropriate, easy to use opto-electronic drive and measurement system is required. This paper discusses the operation of a programmable opto-electronic drive and measurement system     

Advantageous Properties of Frequency Division

The performance of a wideband frequency divider with two independent sinusoidal input signals present is analyzed. Both the case of a relative low-level spurious signal and the case of a relative high-level spurious signal are considered. It is ascertained that a considerable reduction of the spurious signal is achieved and the exact nature of the improvement is dependent on the relative strength of the spurious signal.     

The detectability of molecular hydrogen in interstellar space

This review consists essentially of three parts where we consider: (1) the structure and spectrum of the hydrogen molecule; (2) the processes that in interstellar space can lead to the forma-tion and to the dissociation of the hydrogen molecule, with the aim of establishing its abundance, both on the average and in particular regions of the Galaxy; (3) the lines originating from interstellar molecular hydrogen that could be observed from the Earth. In this last Section the possible obser-vations are classified from the point of view of the height in the atmosphere from which they have to be made.     

Embedded information system re-engineering

Currently fielded embedded information systems face readiness challenges imposed by evolving missions and extended service lifespans. The ability to overcome these challenges is constrained by such factors as shrinking budgets, limited computational capacity and diminished manufacturing sources effects that impact both hardware and software options. Wholesale redevelopment is often cost prohibitive, particularly since large portions of embedded applications continue to fulfil mission requirements. Solutions must preserve prior investments while providing efficient pathways for continued technology refresh. A technology solution for affordable modernization of legacy system software is being development. The Embedded Information System Re-engineering (EISR) project is developing an automation-assisted JOVIAL-to-C re-engineering capability that permits simultaneous modernization of both the structure and source language of legacy embedded applications. Engineers will be able to apply the proven labor-saving visualization and analysis features of modern CASE tools to legacy JOVIAL applications. EISR will thus allow the DoD to recapture previous investments in proven legacy algorithms and mission capabilities while permitting the full exploitation of COTS economies of scale. This paper describes in brief the goals and objectives of the EISR project, and provides the current status of the EISR capability.     

Bipolar nickel-metal hydride batteries for aerospace applications

Electro Energy Inc. (EEI) is developing high power, long life, bipolar nickel-metal hydride batteries for aerospace applications. Bipolar nickel-metal hydride designs allow for high energy and high power designs with a 25 percent reduction in both weight and volume as compared to prismatic and/or cylindrical Ni-MH designs. Utilizing a sealed wafer cell design EEI has demonstrated a 1.2 kW/kg power capability. Prototype designs have achieved 70 Wh/kg. Designs studies show 80 Wh/kg are achievable with EEI's state-of-the-art technology. The sealed wafer cell is the building block for EEI's high power and high voltage bipolar batteries making the assembly easy and significantly lower in cost. Satellite and aircraft batteries are being developed which provide high power and long life. Sealed cells now show excellent rate capability and life. Cells tested in a low earth orbit (LEO) cycle have reached 9000 cycles and continue on test. High power, bipolar battery designs are ideal in applications where using conventional aerospace battery technology would require excessive capacity; weight and volume, thereby reducing usable payload on the vehicle     

Power management and distribution system for a more-electricaircraft (MADMEL)

A five-phase Power Management and Distribution System for a More-Electric Aircraft (MADMEL) program was awarded by the Air Force to Northrop/Grumman Military Aircraft Division in September 1991. The objective of the program is to design, develop, and demonstrate an advanced electrical power generation and distribution system for a More-Electric Aircraft (MEA). The MEA emphasizes the use of electrical power in place of hydraulics, pneumatic, and mechanical power to optimize the performance and life cycle cost of the aircraft. This paper presents an overview of the MADMEL program and a top-level summary of the program results, development and test of major components to date. In Phase I and Phase II studies, the electrical load requirements were established and the electrical power system architecture was defined for both near-term (NT-year 1996) and far-term (FT-year 2003) MEA application. The detailed design and specification for the Electrical Power System (EPS), its interface with the Vehicle Management System, and the test set-up were developed under Phase III. Phase IV, fabrication and testing of the subsystem level hardware, has been completed. Overall system level integration and testing, Phase V, is scheduled to be completed by September 1999     

An analysis of temperature fields in rotating fluid

A possible variant presented for solving the equation of motion of a rotating flow is more general with respect to the variants known in the literature. On the basis of the simultaneous solution of the equations of motion and energy, the temperature fields are determined under changes of the rotation nature.     

Aeronautical telemetry using multiple-antenna transmitters

The placement of multiple antennas on an air vehicle is one possible practice for overcoming signal obstruction created by vehicle maneuvering during air-to-ground transmission. Unfortunately, for vehicle attitudes where more than one of these antennas has a clear path to the receiving station, this practice also leads to self-interference nulls, resulting in dramatic degradation in the average signal integrity. This paper discusses application of unitary space-time codes such as the Alamouti transmit diversity scheme and unitary differential space-time codes to overcome the self-interference effect observed in such systems. The mathematical foundations of these techniques within the context of this application as well as computational performance gains associated with their implementation are provided. Issues such as the cost of channel estimation for trained techniques as well as the throughput performance of nondifferential and differential schemes for realistic air-vehicle motion are analyzed