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The VEGGIE unit is a deployable, low-resource plant growth system that can provide a source of fresh food and crew recreation on long duration space missions. VEGGIE can be stowed in 10% of its deployed volume; a single middeck locker equivalent can stow 1.0m2 of growing area. To reduce complexity, VEGGIE utilizes the ambient environment for temperature control and as a source of CO2. The lighting subsystem uses LEDs that provide a minimum light level of 300 µmol m−2s−1, spectral quality control, and a long operating life in a low profile package. The root zone is a compressible fabric mat. Each VEGGIE module has 0.17 m2 of growing area and can be varied in height from 5 to 45 cm. The mass, including the lighting subsystem and root mat, is 4.7 kg. On the ISS, VEGGIE can mount in the aisle, or in an EXPRESS rack.

The objective of the BPS Technology Validation Test (TVT) flown on the ISS as part of Increment 4 was to verify the functionality of environmental control subsystems and to measure the ability of the BPS to support plant growth and development in microgravity. Additional TVT objectives included validation of information acquisition systems, operations and support systems, and component performance. All TVT objectives were successfully addressed. Most evaluation criteria stipulated pre-flight were met. When there were deviations from pre-mission requirements, root causes were identified and subsystem configurations modified to eliminate these problems. Results from the TVT have been applied to the Plant Research Unit development to reduce technical risks and increase reliability. INTRODUCTION

Orbital Technologies Corporation (ORBITEC) utilizes a variety of in-house testing capabilities (vibration, shock, acoustic loads, space vacuum, temperature cycling, humidity, burn-in, etc.) for qualification and screening of flight components. A lunar dust chamber was designed and constructed to include exposure to lunar regolith and dust simulants. A full factorial design of experiment (DOE) was used to investigate the failure modes of electric fans when exposed to airborne JSC-1AF lunar regolith simulant. This type of testing provides valuable insight into reliability predictions, planned maintenance of a system, and component design improvements to mitigate the effects of lunar dust. Incorporating lunar dust exposure testing at an early stage in the design process will help ensure proper system performance and reliability.

The design of reliable systems is especially important when they are intended for use on the International Space Station (ISS). Limits on crew time and the sensitive nature of experiments being performed require that the systems used to support those experiments have a very low probability of failure. The Plant Research Unit (PRU) has very strict reliability requirements and thus provides a good example of how the challenge of designing reliable systems can be met.

High reliability and system flexibility are driving factors in the Plant Research Unit development. Proper selection of the unit electrical and software control architecture is fundamental to achieving these goals. Key features of the PRU control design include the use of a real time operating system for main process control, dynamic power management, a distributed control architecture and subsystem modularity. The chosen approach will allow future modifications and improvements to be incorporated at the subsystem level with minimal impact to the unit overall. Hardware fault tolerance and redundancy enhance system reliability.