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A reliable nutrient delivery system is essential for long-term cultivation of plants in space. At the Kennedy Space Center, a series of ground-based tests are being conducted to compare candidate plant nutrient delivery systems for space. To date, our major focus has concentrated on the Porous Tube Plant Nutrient Delivery System, the ASTROCULTURE™ System, and a zeoponic plant growth substrate. The merits of each system are based upon the performance of wheat supported over complete growth cycles. To varying degrees, each system supported wheat biomass production and showed distinct patterns for plant nutrient uptake and water use.

Most of the neutrons seen in the habitable environment of spacecraft in LEO are produced in local materials of the spacecraft structures by the impact of the LEO radiation environment. There are two components of the neutron spectra: one produced near the forward direction and a diffuse isotropic component. The forward component satisfies a Volterra equation and is solved by standard marching procedures. The diffuse component is generally of lower energy and nearly isotropically scattered as they diffuse through the spacecraft structures. Leakage at near boundaries marks the diffusion process and solutions are strongly dependent on forward and backward boundaries with minor contributions from lateral diffusion along spacecraft wall structures. The diffuse neutron equation is solved using multigroup methods with impressed forward and backward boundary conditions.

Over the last couple decades, there has been a growing interest in incorporating commercial off-the-shelf (COTS) technologies and open standards in the design of human-rated spacecraft. This approach is intended to reduce development and upgrade costs, lower the need for new design work, eliminate reliance on individual suppliers, and minimize schedule risk. However, it has not traditionally been possible for COTS solutions to meet the high reliability and fault tolerance requirements of systems implementing critical spacecraft functions. Byzantine faults are considered particularly dangerous to such systems because of their ability to escape traditional means of fault containment and disrupt consensus between system components. In this paper, we discuss the design of a voting protocol using Time-Triggered Ethernet capable of achieving data integrity in the presence of a single Byzantine fault.

Conceptual designs for a space suit Personal Life Support Subsystem (PLSS) were developed and assessed to determine if upgrading the system using new, emerging, or projected technologies to fulfill basic functions would result in mass, volume, or performance improvements. Technologies were identified to satisfy each of the functions of the PLSS in three environments (zero-g, Lunar, and Martian) and in three time frames (2006, 2010, and 2020). The viability of candidate technologies was evaluated using evaluation criteria such as safety, technology readiness, and reliability. System concepts (schematics) were developed for combinations of time frame and environment by assigning specific technologies to each of four key functions of the PLSS -- oxygen supply, waste removal, thermal control, and power. The PLSS concepts were evaluated using the ExtraVehicular Activity System Sizing Analysis Tool, software created by NASA to analyze integrated system mass, volume, power and thermal loads.

A small team of NASA engineers has been assembled at the Johnson Space Center, with the goal of developing an inexpensive space-capable vehicle. In order to minimize cost and development time of the experimental vehicle, it was desirable to build upon a previously-developed vehicle shape. The basic shape of the X-24A experimental lifting body was chosen for several reasons, and in the case of the Environmental Control and Life Support (ECLS), the de-orbit cross-range capability of this shape provides for a minimal on-orbit time while waiting for landing opportunities, which in turn simplifies the ECLS. Figure 1 shows the X-38 vehicle body shape. In keeping with the goal of rapidly developing an inexpensive and reliable vehicle, the ECLS was developed using simple, passive systems where practical. This paper provides an overview of the ECLS mission requirements and design, with emphasis on the philosophy used in its development.

In planning for Exploration missions and developing the required suite of environmental monitors, the difficulty lies in down-selecting a multitude of technology options to a few candidates with exceptional potential. Technology selection criteria include conventional analytical parameters (e.g., range, sensitivity, selectivity), operational factors (degree of automation, portability, required level of crew training, maintenance), logistical factors (size, mass, power, consumables, waste generation) and engineering factors such as complexity and reliability. Other more subtle considerations include crew interfaces, data readout and degree of autonomy from the ground control center. We anticipate that technology demonstrations designed toward these goals will be carried out on the International Space Station, the end result of which is a suite of techniques well positioned for deployment during Exploration missions.

The wonder of space exploration is a sure way to catch the attention of students of all ages, and space biology is one of many sciences critical to understanding the spaceflight environment. Many systems used in the past for space-to-classroom biology activities have required extensive crew time and material resources, making space-linked education logistically and financially difficult. The new Education Payload Operations Kit C (EPO Kit C) aims to overcome obstacles to space-linked education and outreach by dramatically reducing the resources required for educational activities in plant space biology that have a true spaceflight component. EPO Kit C is expected to be flown from STS-118 to the International Space Station in June 2007. NASA and several other organizations are currently planning an outreach program to complement the flight of EPO Kit C.

NASA-JSC is evaluating planetary mission scenarios where plants will provide the majority of the diet for the crew. The requirements of both plants and crew diet need to be integrated in the development of the final food system. Plant growth has limitations in type and quantity of crops to be produced while diets must meet palatability and nutritional requirements as well as limited processing labor, equipment and power. A plan is presented for the development of a food system based heavily on grown crops. Although the steps taken in the development are applicable to the design of any long duration flight food system. The process begins with the development of a food list, followed by preliminary menu design, nutritional analysis and finally menu testing.

Automatic thermal comfort control for the minimum consumables PLSS is undertaken using several control approaches. Accuracy and performance of the strategies using feedforward, feedback, and gain scheduling are evaluated through simulation, highlighting their advantages and limitations. Implementation issues, consumable usage, and the provision for the extension of these control strategies to the cryogenic PLSS are addressed.

A noncontacting clearance seal consists of a series of centrifugal air pumps and oil/air separators for air turbine starters on the BR710 and the CFM56-5 engines. Conventional contacting seals for rotating shafts are limited in life due to the formation of oxidized oil coke buildup on the sealing surfaces. The clearance seal directly addresses the problem of viscous heat generation in carbon face and lip seals by eliminating contact. Standard contacting seals typically have local temperature increases of 50 to 75 °F higher than the gearbox sump oil. Heat generation by the clearance seal is minimized, resulting in a significant increase in reliability compared to a standard contacting seal. The reliability increase is estimated for various flight-hour-to-start-cycle ratios in air turbine starter gearboxes.