Alexander Hoehn

• PhD Aerospace (1993)
• Research Associate at University of Colorado Boulder

The Freezer / Refrigerator / Incubator Device for Galley and Experimentation (FRIDGE) is a middeck locker-sized unit developed by BioServe Space Technologies for use within the Galley rack of the International Space Station (ISS) for food storage as well as in the EXPRESS rack for science experiment support. FRIDGE was optimized to provide a large...

Algal-based photobioreactors offer a promising bioregenerative technology that can perform the functions of air revitalization, water recycling, and food production in a human spacecraft life support system. In order to assess their performance in this context, this study exposed a non-axenic green algal culture (Chlorellacea) to an atmospheric pre...

The project CopKa at the Technical University of Munich investigates the possibilities of enhancing the situation awareness during emergency and rescue situations (both routine and major incidents) in a coordination centre, while decreasing the workload of the rescue crew. In the envisioned CopKa scenario, video and telemetry data from different da...

The platform for resource observation and in situ prospecting for exploration, commercial exploitation, and transportation (PROSPECT) instrument package is under development by the European Space Agency for the upcoming Luna-27 mission to the lunar south pole. The purpose of the instrument is to detect and quantify volatiles on the lunar surface wi...

Several promising multi-junction solar cell concepts for space applications are currently under development worldwide. On-Orbit Verification on CubeSats is a cost-efficient method to gain data on critical hardware early in the design validation process. The MOVE-II CubeSat will be used for the verification of novel 4-6 junction solar cells. With a...

This paper presents the on-orbit results and the lessons learned from First-MOVE (Munich Orbital Verification Experiment), the first CubeSat mission of the Institute of Astronautics (LRT) at the Technische Universität München (TUM). The development of the satellite started as a student project in 2006. First-MOVE was launched on November 21st 2013....

This paper presents the simulation results for a phased antenna array with novel liquid crystal phase shifters (LCPSs). This work investigated the usability of this electronically steerable antenna technology in an inter-satellite link using a geostationary satellite. Due to the design of the LCPS and the aperture of the antenna, communication over...

This paper reports on a series of experiments that were conducted on a partial-g parabolic flight campaign to determine key parameters of hoppers, designed for regolith sampling, science experiments, or in situ resource utilization (ISRU) processes on Moon or Mars. A major problem related to these applications is the clogging of feeding and conveyi...

A strong impetus for the elaboration of a conceptual framework for integrative research under space conditions is clearly noticeable. A group of space-experienced investigators forwarded explicitly a request to the scientific community for such a conceptual framework [Goswami et al., 2012]. The EU funded THESEUS project (Towards Human Exploration o...

The goal of this work was to (1) evaluate different gear concept for spaceflight application with minimum backlash, (2) design a test setup to test the most promising concepts, and (3) conduct preliminary validation tests. The evaluation focused on the primary possibilities to influence the behavior of gear performance: variation of material and va...

As part of the Rodent Habitat project being planned to enable physiological research onboard the ISS, live rodents (mice and rats) shall be transported in the sealed pressurized environment of commercial cargo resupply carriers such as SpaceX’s Dragon or Orbital’s Cygnus. The previously flown Animal Enclosure Module (AEM) has been upgraded by NASA...

Modern high data rate satellite communication systems increasingly utilize the Ka-band due to its ability to support higher bandwidth. Prior research work presented a copper-galvanically produced Ka-band horn array antenna and associated waveguide distribution network, mounted on a two axes mechanical steerable mechanism (LISAMS) for use aboard fas...

The goal of this work was to (1) define parameters to characterize a pointing mechanism, (2) design a setup to test these parameters and, (3) verify the test methods by comparing the results to the theoretically calculated or independently verified numbers. The verification of the test results was conducted with an in-house built Antenna Pointing M...

Plants with different abilities for osmotic adjustment (cowpea, bean, and sugarbeet) were subjected to gradually decreasing soil water content. During the development of water deficit stress, various plant water parameters were measured to characterize their relationship to the near infrared R 1300/R 1450 leaf water index, which is based on the mea...

This study identifies transcriptional regulation of stress response element (STRE) genes in space in the model eukaryotic organism, Saccharomyces cerevisiae. To determine transcription-factor dependence, gene expression changes in space were examined in strains bearing green fluorescent protein-tagged (GFP-tagged) reporters for YIL052C (Sfp1 depend...

Leaf water indices based on leaf reflectance may depend not only on the variable of interest, leaf water content, but may also be influenced by a variety of extraneous variables, leading to considerable data variability if such extraneous variables are not eliminated or taken into account. Here, we examined the nature of three potential extraneous...

The common features of spectral reflectance from vegetation foliage upon leaf dehydration are decreasing water absorption troughs in the near-infrared (NIR) and short-wave-infrared (SWIR). We studied which leaf water index in the NIR and SWIR is most suitable for the assessment of leaf water content and the detection of leaf dehydration from the la...

Remote sensing leaf water indices depend on two variables: the relative water content (RWC) of leaf cells, which may serve as an indicator for water deficit stress in plants, and leaf thickness. The measurement of leaf water thickness (LWT) appears to be an experimental method that can be well correlated with leaf water indices. We studied how leaf...

MDA is designed as a test bed for an astrobiology field instrument to detect microbial metabolic activity in terrestrial or extraterrestrial geological soil samples. MDA employs electrochemical sensors in a unique differential chamber configuration, able to detect minute changes in the chemical composition between the two otherwise identical chambe...

Several small life sciences research modules were designed to accommodate both scientific research and K-12 educational objectives on the same spaceflight mission. The K-12 educational objectives are accomplished by participating students around the globe and complimented by ground experiments conducted in their own classrooms. The spaceflight rese...

We describe an instrument and methodology for definitive detection of microbial life via metabolic growth activity, with minimal assumptions using an array of metabolism-sensitive sensors and an advanced sample handling system.

It is proposed to employ a greenhouse for life support on the Martian surface to reduce the equivalent system mass (ESM) penalties encountered with electrical crop lighting. The ESM of a naturally lit plant growth system compares favorably to an electrically lit system when corrections for area are made based on available light levels. A transparen...

This paper reports on the approach and progress to refine the estimates of the Mars surface photosynthetically active radiation (PAR) on a global scale that is averaged over a longer time period. While the PAR on Mars has been evaluated previously, the results have been limited in scope either temporally or spatially, such as only at a particular l...

Thin films continue to play an ever-increasing role in high performance structures for space exploration. Membrane structures have been developed or envisioned for such applications as scientific balloons, deep space antennas, Earth radiometers, radars, concentrators, telescopes, sun shields, solar sails, solar arrays, spacecraft booms, and planeta...

Small spaceflight life science experiments, such as plant growth chambers and animal habitats, operate in unique environments. The experiments are often sealed systems that control atmospheric constituents, temperature, and humidity. Chemical scrubbers can be an efficient and reliable way to actively remove carbon dioxide for shorter experiment dur...

This study investigated the possibility of detecting water deficit stress in plants by using optical signals collected from leaves. Two theoretical approaches have been investigated. In principle, chlorophyll fluorescence can be used to measure generally stressful situations in plants. Our review, however, found that simple ratios of coarsely time-...

BioServe Space Technologies, a NASA Research Partnership Center (RPC), has developed and operated various middeck payloads launched on 23 shuttle missions since 1991 in support of commercial space biotechnology projects. Modular cell culture systems are contained within the Commercial Generic Bioprocessing Apparatus (CGBA) suite of flight-qualified...

PGBA, a 0.08m 2 / 27 liter spaceflight plant chamber payload employs two temperature-controlled liquid coolant loops to control the temperature and humidity of the sealed plant chamber independently. Cabin-air cooled thermoelectric heat pumps control the temperature of the water-alcohol coolant fluid in each loop, which is circulated by small, low-...

Porous plate dehumidifiers (PPD) and porous tube nutrient delivery systems (PTNDS) are designed to provide a means for accurate environmental control, and also allow for two-phase flow separation in microgravity through surface tension. The technological challenges associated with these systems arise from the requirement to accurately measure and c...

Long distance/duration human space missions demand economical, regenerative life support systems. With naturally available light and low atmospheric pressures, missions to the surface of Mars might employ higher plants in a bioregenerative life support systems housed within a transparent inflatable greenhouse. The primary advantages of an inflatabl...

The increased demand in the area of space life sciences necessitates the need for more experimentation hardware with increased capabilities. Due to the high cost of hardware development for space based research, new hardware should be modular in design and suited to handle a variety of different experiments. The fluid handling systems found in expe...

BioServe Space Technologies, a NASA-sponsored Commercial Space Center, began a new era of space flight research with the launch of the Commercial Generic Bioprocessing Apparatus payload to the International Space Station (ISS) in April 2001 on STS-100. Prior to this launch, BioServe’s industry partners had been limited to relatively infrequent and...

In traditional applications in soil physics it is convention to scale porous media properties, such as hydraulic conductivity, soil water diffusivity, and capillary head, with the gravitational acceleration. In addition, the Richards equation for water flux in partially saturated porous media also contains a gravity term. With the plans to develop...

Accurate root zone moisture control in microgravity plant growth systems is problematic. With gravity, excess water drains along a vertical gradient, and water recovery is easily accomplished. In microgravity, the distribution of water is less predictable and can easily lead to flooding, as well as anoxia. Microgravity water delivery systems range...

Spaceflight plant growth chambers require an atmosphere control system to maintain adequate levels of carbon dioxide and oxygen, as well as to limit trace gas components, for optimum or reproducible scientific performance. Recent atmosphere control anomalies of a spaceflight plant chamber, resulting in unstable CO2 control, have been analyzed. An a...

Aeroponics is the process of growing plants in an air/mist environment without the use of soil or an aggregate media. Aeroponics has contributed to advances in several areas of study including root morphology, nutrient uptake, drought and flood stress, and responses to variations in oxygen and/or carbon dioxide root zone concentrations. The adaptab...

During the past three decades, both the Russian and American space programs have demonstrated that human presence in space can be sustained for either short or long durations as long as essential life support expendables are regularly resupplied from Earth. In the last decade, increasing attention has been placed on the development of bioregenerati...

An experimental study examined the relevance of membrane surface properties to the overall performance of hydrophilic membrane-based dehumidifiers (membrane condensers). Specifically, this study examined a model for the overall mass transfer coefficient derived from surface-science sticking-coefficient arguments, which states that performance is a...

Future long duration, manned space flight missions will require life support systems that minimize resupply requirements and ultimately approach self-sufficiency in space. Bioregenerative life support systems are a promising approach, but they are far from mature. Early in the development of the NASA Controlled Ecological Life Support System Progra...

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 t...

Technology for microgravity plant growth has matured to a level which allows detailed gravitational plant biology and commercial plant biotechnology studies. Consequently, plants have been shown to adapt to the space flight environment, which validates their use in advanced life support applications. However, the volume available for plant growth i...

Improvements in plant illumination, irrigation, and thermal control systems have led to significant progress in the cultivation capability of space flight plant growth facilities. An area that has received little attention, however, is the on-orbit ability to sow and initiate the germination of seed within these facilities. In addition to the need...

A dehumidification system for low gravity plant growth experiments requires the generation of no free-liquid condensate and the recovery of water for reuse. In the systems discussed in this paper, the membrane is a barrier between the humid air phase and a liquid-coolant water phase. The coolant water temperature combined with a transmembrane press...

The Plant Generic BioProcessing Apparatus (PGBA), a plant growth facility developed for commercial space biotechnology research, has flown successfully on 3 spaceflight missions for 4, 10 and 16 days. The environmental control systems of this plant growth chamber (28 liter/0.075 m2) provide atmospheric, thermal, and humidity control, as well as lig...

Recently, NASA requested proposals for the Mars Surveyor 2001 Orbiter, Lander, and Rover. The University of Colorado's BioServe Space Technologies Center and several industrial affiliates proposed a Mars soil toxicity instrument, BioTox, for the Lander's "soil box." The purpose of the BioTox experiment is to assess the overall toxicity of Mars soil...

The application of bioregenerative life support systems provides an attractive approach to minimize resupply requirement and ultimate self-sufficiency on long duration manned missions in space. The on-board cultivation of salad-type vegetables for crew consumption has been proposed as a first step approach towards reducing a total reliance on the r...

Products derived from plants, such as foods, pharmaceuticals, lumber, paper, oils, etc., are pervasive in everyday life and generate revenues in the hundreds of billions of dollars. Research on space-grown plants has the potential to alter quantities, properties and types of plant-derived products in beneficial ways. Research on space grown plants...

PGBA, a plant growth facility developed for commercial space biotechnology research, successfully grew a total of 30 plants (6 species) for 10 days on board the Space Shuttle Endeavour (STS-77) and is scheduled for reflight on board MSL-1 (STS-83) for a 16 day flight. The PGBA life support systems provide atmospheric, thermal, and humidity control...

PGBA, a plant growth facility developed for space flight biotechnology research, successfully grew a total of 30 plants in a closed, multi-crop chamber for 10 days aboard the Space Shuttle Endeavor (STS-77). {ital Artemisia annua, Catharanthus roseus, Pinus taeda, Spinacia oleracea and Trifolium repens} were the five species studied during this mis...

The final space flight version of a new plant growth chamber is presented. This plant growth chamber has been designed to maintain adequate light levels, to control temperature and humidity levels, and to control chamber atmospheric composition. This plant research facility has been integrated into a Space Shuttle payload designated PGBA (Plant Gen...

A system to mix, carbonate, and dispense carbonated beverages in the microgravity environment is presented. This beverage technology has been integrated into a Space Shuttle payload designated FGBA2 (Fluid Generic Bioprocessing Apparatus 2), which flew on STS-77 May 19-29,1996. This payload incorporates facilities to examine changes in cardiac perf...

The Animal Module for Autonomous space Support (A-MASS) was developed to enable 30-day spaceflight for mice on the first Commercial Experiment Transporter mission. Because space hardware did not previously exist to support mice without astronaut intervention, the A-MASS presented considerable technical and animal care challenges. The technical chal...

Photoprotective energy dissipation activity, that was largely associated with the de-epoxidation of the xanthophyll cycle, was examined in spinach leaves grown outside during the winter versus leaves that had developed at moderate temperatures in a glasshouse. On a leaf area basis the rates of photosynthesis were higher in leaves from the field at...

A wide variety of technical and science questions arise when attempting to envision the long-term support of plants, algae and bacteria in space. Currently, spaceflight data remain elusive since there are no U.S. carriers for investigating either the germane technical or scientific issues. The first flight of the Commercial Experiment Transporter (...

Plant growth, and especially plant performance experiments in microgravity are limited by the currently available plant growth facilities (low light levels, inadequate nutrient delivery and atmosphere conditioning systems, insufficient science instrumentation, infrequent flight opportunities). In addition, mission durations of 10 to 14 days aboard...

Dedicated electronic hardware has been constructed to monitor fluid distributions inside a plant rooting/nutrient substrate (Rockwool). With this hardware the effect of dynamically varying gravity states, from enhanced 2g to reduced 0.01g, on solution distributions inside a cube of substrate was monitored aboard the NASA KC-135 reduced gravity rese...

The paper describes the design and the operation principles of the Plant Module for Autonomous Space Support (P-MASS), designed to provide life support for a variety of plants, algae, and bacteria in low earth orbit during the maiden flight of COMET-1, scheduled for 1993. During flight (scheduled to continue for 30 days), both color video images an...

Leaves from two species, Euonymus kiautschovicus and Arctostaphylos uva-ursi, with a variety of different orientations and exposures, were examined in the field with regard to the xanthophyll cycle (the interconversion of three carotenoids in the chloroplast thylakoid membranes). East-, south-, and west-facing leaves of E. kiautschovicus were sampl...

The evolutionarily-developed Lunar Controlled Ecological Life Support System (CELSS) Test Module presented can address questions concerning long-term human presence-related issues both at LEO and in the lunar environment. By achieving well-defined research goals at each of numerous developmental stages (each economically modest), easily justifiable...

Previous design efforts of a cost effective and reliable regenerative life support system (RLSS) provided the foundation for the characterization of organisms or 'biological processors' in engineering terms and a methodology was developed for their integration into an engineered ecological LSS in order to minimize the mass flow imbalances between c...

The autonomous lunar precursor mission presently proposed for low cost manned revisits to the lunar surface, designated 'Lunar Oasis by Automation and Robotics', employs two self-similar robotic vehicles, and three experimental 'biovolumes' which are directly derived from the lunar landers that are initially entrusted with fulfilling mission hardwa...

Continuing its emphasis on the creation of a cisluar infrastructure as an appropriate and cost-effective method of space exploration and development, the University of Colorado explores the technologies necessary for the creation of such an infrastructure, namely (1) automation and robotics; (2) life support systems; (3) fluid management; (4) propu...

Technologies necessary for the creation of a cis-Lunar infrastructure, namely: (1) automation and robotics; (2) life support systems; (3) fluid management; (4) propulsion; and (5) rotating technologies, are explored. The technological focal point is on the development of automated and robotic systems for the implementation of a Lunar Oasis produced...