lss hands-on research opportunities for students at the

48th International Conference on Environmental Systems ICES-2018-144 8-12 July 2018, Albuquerque, New Mexico

Copyright © 2018 Institute of Space Systems – University of Stuttgart

LSS hands-on research opportunities

for students at the University of Stuttgart

Gisela Detrell1, Jochen Keppler2, Harald Helisch3 and Stefanos Fasoulas4

Institute of Space Systems – University of Stuttgart, Stuttgart, D-70569 Germany

Research in the field of Life Support Systems (LSS) has been carried out at the Institute of

Space Systems (IRS) at the University of Stuttgart for over two decades, mainly focusing on

system analysis and the use of microalgae, especially Chlorella vulgaris, for space applications.

In 2017, the LSS knowledge and tools acquired during this time have been first used to provide

the aerospace engineering master students a unique opportunity to learn-by-doing. The

hands-on training starts with a series of short lectures, focusing on basic LSS concepts, ISS

technologies and potential future biological systems, such as algae, both from a biological and

engineering point of view. After the lectures, the students carry out an algae cultivation

experiment in a small flat plate photobioreactor lasting one week, taking measurements of

biomass and nutrient concentration, spectrum absorption and morphology observation. The

data obtained helps understanding and consolidating the concepts learned in the lectures.

Finally, the students use the tool “Environment for Life Support Simulation and Analysis”

(ELISSA), developed at the IRS. ELISSA is a time-step based simulation which includes

several LSS components (both currently in use or under development) allowing to evaluate

the LSS performance over time, and estimate the Equivalent System Mass. The students carry

out a trade-off of the potential physico-chemical technologies contained in ELISSA, simulate

their selected LSS configuration and finally compare the results of the pure physico-chemical

system, with a hybrid one, including a photobioreactor, such as the one they have used on the

laboratory. The combination of theoretical lectures, laboratory experiments and simulation

analysis provides them the means required to fully understand the insides and challenges of a

hybrid LSS. This paper presents the methodology used for the hands-on training as well as

the results from the 2017 session.

Nomenclature

4BMS = 4-Bed Molecular Sieve

AES = Air Evaporation System

CHX = Heat Exchanger

ECLSS = Environmental Control and Life Support System

EDC = Electrochemical Depolarized CO2 Concentrator

ECTS = European Credit Transfer and Accumulation System

ELISSA = Environment for Life-Support Systems Simulation and Analysis

ESM = Equivalent System Mass

FPA = Flat Panel Airlift

IRS = Institute of Space Systems

LSS = Life Support System

OD = Optical Density

PBR = Photobioreactor

PBR@LSR = Photobioreactor at the Life Support Rack

PC = Physico-chemical

PYRO = Pyrolysis

1 Postdoc, Institute of Space Systems, Pfaffenwaldring 29, 70569 Stuttgart, [email protected]. 2 PhD Candidate, Institute of Space Systems, Pfaffenwaldring 29, 70569 Stuttgart, [email protected]. 3 PhD Candidate, Institute of Space Systems, Pfaffenwaldring 29, 70569 Stuttgart, [email protected]. 4 Institute Director, Institute of Space Systems, Pfaffenwaldring 29, 70569 Stuttgart, [email protected].

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International Conference on Environmental Systems

R-PEM = Reversible Polymer Electrolyte Membrane

R-SOFC = Reversible Solid Oxide Fuel Cell

SAWD = Solid Amine Water Desorption

SFWE = Static Feed Water Electrolysis

SN = Supernatant

SWC = Solid Waste Compressor

SWIS = Solid Waste Incineration System

TCCS = Trace Contaminant Control System

TIMES = Thermoelectric Integrated Membrane Evaporator System

VCD = Vapor Compression Distillation

VPCAR = Vapor Phase Catalytic Ammonia Removal

I. Introduction

roviding the aerospace engineering master students hands-on training, getting them closer to the research carried

out at the institute to complement a wide range of theoretical lectures, has shown to be a success at the Institute

of Space Systems (IRS) of the University of Stuttgart. Each summer semester, the institute offers several hands-on

training options, from which students have to select two. Training options offered in the previous years include: fuel

cells and sensors workshop, rendezvous and docking training, neurofeedback-training, programming a spacecraft for

the Soyuz simulator and mission analysis workshop. After successfully demonstrating the gained knowledge through

an exam or a report, students can obtain three ECTS for the space specialization in the aerospace engineering master.

A high demand each year, the favorable feedback from the participants, and the financial support from the university

has ensured the continuity and improvement of the offered hands-on training courses. A newly added example is the

Life Support System (LSS) for human spaceflight workshop, started in 2017, which is planned to take place once a

year.

A. LSS Simulation research

The research interest in LSS at the institute started in

the mid-90s, with the development of the software tool

ELISSA (Environment for Life-Support Systems

Simulation and Analysis), within the department

Astronautics and Space Stations, focused on the conceptual

design of manned missions. The LabVIEW-based tool,

Figure 1, is time-step simulation environment for LSS,

which allows analysis and comparison of different LSS

designs and optimization. For a specific mission scenario,

the user can select an LSS configuration from a wide

library of physico-chemical and biological potential

components, including technologies currently in use and in

development. Each component is modeled according to

available reference data: from specifications for existing technologies or experimental data or physical and chemical

fundamentals for those in development. As a result, the user obtains the evolution/performance of the system over

time and the overall mass, volume, required power and produced heat. Since its creation, several PhDs and

undergraduate thesis have focused on the development and improvement of ELISSA, with special focus on updating

the components with experimental data from the research carried out at the IRS laboratory.1-4 The tool has been used

several times in another hands-on training offered at the institute: the Space Station Design Workshop5. The tool can

be made available to other universities under a license agreement for student projects.

B. Hybrid LSS research

One of the system analysis carried out with ELISSA was to assess break-even times of LSS strategies involving

the use of microalgae, cultivated in photobioreactors (PBRs), to create hybrid LSS, combining physico-chemical

technologies with biological components. Results showed a break-even time of less than two years for a hybrid LSS

compared to a pure physico-chemical one.6,7 This justified and encouraged a new research line, focusing on the

application of microalgae for space applications. Microalgae, like plants, are photosynthetic organisms, able to

P

Figure 1. ELISSA current user-interface

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produce oxygen (O2) consuming carbon dioxide (CO2). Compared to higher

plants, algae offer a higher harvest index, higher biomass productivity and

require less water. However, due to its high content in proteins, algae cannot

be used as a sole nourishment source, but can reduce part of the food supply

required. In 2010, as initial step, Flat Panel Airlift (FPA) PBRs (6 and 26 L)

were set up at IRS, Figure 2, to gain knowledge on the stable and efficient

algae growth cultivation, and the influence of the cultivation parameters,

such as temperature, pH, background medium, nutrients and CO2 supply.

The selected algae species is Chlorella vulgaris, a unicellular, spherical,

immobile organism, with 2-10 µm diameter. It is cultivated in a nutrient

solution. Among other parameters, its weak colony-forming and high-value

nutrients make it a potential candidate for space applications. The same

culture has been cultivated in the IRS laboratory since 2010, in a non-axenic

manner. Besides the pure biological research, several aspects from the

engineering required to provide the algae the adequate environment have

been studied. Focusing on space application, experiments with PBR reactor

geometries, microgravity adapted sensors and automation of the cultivation

were conducted in two parabolic flight campaigns in 2010 and 2014.3,8 The

knowledge gained in both engineering and biological fields led in 2014 to a

cooperation project with DLR and Airbus Defence and Space:

Photobioreactor at the Life Support Rack (PBR@LSR), which goal is to

demonstrate the functionality of a hybrid life support system and prove that

non-axenic long-term cultivation of microalgae under space conditions is

feasible, with a 180-days experiment.9,10

The knowledge gained with the current on-going research projects, both

in LSS simulation and microalgae cultivation for space applications has

been the basis of the new hands-on training LSS for human spaceflight. This paper explains the general training

approach, the three main blocs: theory, laboratory experiment and simulation, and the results and lessons learned of

this very first edition.

II. Hands-on training approach

The hands-on training is carried out by three LSS researchers: two engineers one biologist. Its goal is to provide

the students an opportunity to learn practically how to design a LSS and the potential use of microalgae for space

applications.

The training is divided in three blocks: theoretical concepts, simulation analysis and laboratory experiment. The

theoretical part starts with a two-hours lecture, where basic concepts, required for the practical parts are explained. As

a first introduction to the subject, the students are challenged with a calculation exercise, to make a first estimation of

the design a LSS. The simulation analysis is planned to last one week and starts with an introductory two hours tutorial

to get familiarized with the simulation tool. With guidance during the week, the students use the tool to design,

simulate and compare two LSS for a specific mission, one pure physico-chemical and one containing a PBR. Finally,

the students carry out their own cultivation experiments in small groups for five days, taking measurements every day

to evaluate the performance of the algae.

The combination of the three blocks should allow the students to have a critical thinking spirit when looking at

theoretical/simulation/laboratory obtained results. For the initial calculation “ideal data” (assuming the optimization

of the system) is used. The comparison of this ideal data with “real” laboratory obtained results raises questions: why

is it different? How can I improve the parameters of my experiment to get closer to “ideal” conditions?

The evaluation of each student is based on a report, of maximum 10 pages. The objective of the report is to get the

students used to a typical format/length of a scientific publication/paper.

The students are allowed to work in small groups during the training and share results. The evaluation focus does

not lay on who obtained the best cultivation results or the most optimized simulation, but on a concise but complete

discussion and reasoning of the results obtained.

To ensure a dedicated guidance and tutoring, in 2017, the number of participants was limited to 9.

Figure 2. FPA from Subitec©

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III. Theoretical concepts

The two-hours lecture covers basic LSS concepts, the current state of physico-chemical systems, and an

introduction to biological systems both from a biological and engineering point of view. This chapter summarizes the

contents of this lecture and the calculation exercise proposed to the students.

A. LSS Basics

The LSS is the subsystem in charge to maintain

in an isolated volume an environment suitable for the

well-being of astronauts and systems during the

mission. Humans require a breathable atmosphere,

water and food. For an initial design of the LSS, the

human can be treated as a black-box, with oxygen,

drinking water, food and hygiene/wash water as

inputs, and carbon dioxide, condensate water, urine,

feces, dirty hygiene/wash water and heat as outputs.

The tasks of the life support system, which deal with

these inputs and outputs, can be divided in four

subgroups: atmosphere, water, food and waste

management, Figure 3. LSS can be divided in open

systems (all inputs fresh supplied) and regenerative

systems (recycling of the outputs to produce new

inputs). Phyisico-chemical or biological principals,

or a combination of both can be used for

recycling.11,12

Figure 3. LSS tasks division in four subgroups

B. Physico-chemical components – ISS example

The International Space Station (ISS) uses physico-chemical components: molecular sieves for CO2 removal, water

electrolysis for O2 generation, a Sabatier reactor for CO2 reduction, multifiltration for water recycling and Vapor

Compression Distillation (VCD) for urine. Food is supplied from Earth and waste is treated and disposed (burned up

through a controlled reentry into the Earth‘s atmosphere).13 Other physico-chemical technologies are currently under

development and might play an important role in future missions.

C. Biological components – from an engineering point of view

The main advantage of biological components is their capability to close the carbon loop producing food. When

talking about biological components, most people only consider plants, but another candidate for space application

are algae. Compared to higher plants, algae provide a higher harvest index, higher biomass productivity, higher light

exploitation and require less water14,15. However, due to its high content of proteins, a maximum of approximately

30% of the daily consumption could be substituted by algae. To use algae for space applications, not only biological

aspects are crucial, but also the engineering to develop the equipment that provides the right environment for the algae

in space.

The experiment PBR@LSR16,17, Figure 4, is used as example

to explain the required research and hardware selection for a µg

PBR, which includes: reactor design to ensure the well-being and

circulation of the algae; selection of the appropriate pump to

ensure the algae do not get damaged; selection of the proper

illumination, combining blue and red LEDs; design of a gas

handling and humidity control, to supply the required CO2 and

extract the produced O2 and humidity; a thermal control, to ensure

the algae stay in an appropriate temperature range, which is

controlled through the ISS cooling system, requiring proper

interfaces; a liquid exchange system, to introduce nutrients and

extract produced biomass; and a monitoring/control/DAQ, with

the proper sensors, actuators and data processing.

Figure 4. PBR@LSR ©Airbus

Food Management

WaterManagement

WasteManagement

p, Tr.h.

Air Management

O2, CO2

CO2

O2, N2

O2

Food Feces

H2OSludge

Fertilizer

H2O, Fertilizer

H2O

Pot. Water

Hyg. Water

Urine

Condensate

ΔpQ

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D. Biological components – the biology concepts behind them

Microalgae are uni- or multi-cellular, aquatic, eukaryotic microoganisms. For photoautotrophic growth, they perform

photosynthesis, eq. 1, which is a key ability for production of O2 and edible biomass (glucose, C6H12O6) from CO2

and water (H2O) by using light energy.

6 CO2 + 12 H2O + Δ𝐻hν → C6H12O6 + 6 H2O + 6 O2 (1)

(where ΔHhν = 2870 kJ mol-1 glucose)

The eukaryotic green algae Chlorella vulgaris is an immotile single cell organism of spherical shape with a

diameter of 2-10 µm18. C. vulgaris shows a wide temperature and pH tolerance19 and grows within a wide range of

CO2 concentrations20, which makes it a potential candidate for space applications. Due to high resistance to cross

contamination the cultivation process can be performed in a non-axenic manner21. Biomass from C. vulgaris is also a

nutritive food source containing 7.3% carbohydrates, 48.2% proteins and 15.9% fats with addition of several vitamins,

minerals and mono-/polyunsaturated fatty acids22.

E. First estimation of system sizing

After the theoretical lecture, a design calculation exercise is assigned to the students, which consists on sizing an

air management physico-chemical system and a biological one using a PBR and compare them.

The physico-chemical system is based in current existing technologies, composed by a CO2 concentrator, a Sabatier

reactor and water electrolysis. The PBR design includes all required hardware to cultivate the algae, the consumables

required and a post-processing unit to make the algae edible.

The goal is not only to get a first feeling on the sizing process and an idea of the order of magnitude of the size of

a LSS, but also to wonder about the design drivers, the advantages/disadvantages of each option and how the systems

could be improved.

IV. Laboratory experiment

For the practical approach C.vulgaris

suspension was cultivated in a diluted sea water

nitrogen medium (DSN) in three identical airlift

flat plate photobioreactors, Figure 5 (designed

and constructed at IRS). The cultures were

inoculated with an identical starter culture. Used

macronutrients were phosphate (PO43-) and

ammonium (NH4+) in concentrations of 200

mg/l - 1000 mg/l. The photosynthetic reaction

was driven by red/blue LED panels (designed

and constructed at IRS) with a mean

photosynthetic photon flux density

PPFD=200 µmol photons/m²/s for five days.

Temperature was regulated to 26°C (+/-2°C)

with a cooling/heating bath. CO2 was set to 6-8

Vol.%.

Figure 5. Flat plate PBR used for the laboratory

Physiological performance was determined by calculation of specific growth rates (µ), and uptake rates for NH4+

and PO43-, eq. 2 and eq. 3.

µ = ln((X1) − ln(X0))/(t1 − t0) [1/d] (2)

ΔX/Δt = (X1 − X0)/(t1 − t0) [g/L/d] (3)

with X = biomass in g/L and t = time in days

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During the five-days experiment students take samples and analyze them visually in a microscope, analyzing the

distribution and homogeneity of the individual microalgae cells within the suspension, and the presence of bacteria or

other foreign objects, such as nutrient crystals.

Besides visually analyzing the microalgae samples using the microscope, the absorbance spectrum of C. vulgaris

was also analyzed, using the educational-purpose spectrometer SpectroVis Plus from Vernier Software & Technology,

which was specifically procured for this training, thanks to the financial support of the University. The goal is to

identify the absorbance maxima of C. Vulgaris.

The Optical Density (OD) at 680 nm wavelength is measured every day, to see the evolution of the cell density.

The students use the correlation between OD680 and dry biomass made for C. vulgaris according to Helisch et al.23 to

determine the dry biomass of the individual samples.

Finally, the students also measure the macro nutrient concentration within their PBR on days one, three and five.

To determine the macro nutrient concentration, the cell suspension is centrifuged (4000 rpm, 4 min) and the

supernatant (SN) is separated. SN samples are prepared according to manufacturer protocols (Hach GmbH, Berlin,

Germany) and NH4+ and PO43- concentrations are measured in test cuvettes (NH4+ in LCK 303 at 694 nm, PO43-

in LCK 049 at 435 nm).

The educational goal of the experimental part is to allow students to carry out their own experiment, producing

their own data, which can be used for the calculation of potential carbon fixation due to algal biomass formation.

Moreover, the experience should serve to identify potentials and limitations of the cultivation system/environment, as

well as the defined bioprocess parameters.

V. Simulation analysis

The proposed mission scenario for the simulation analysis is a permanent base on the Mars surface, for a crew of

6 astronauts, with a resupply mission option every two years. It assumes that the technologies for in-situ resources

utilization are still not available at the beginning of the mission. The goal of the analysis is to evaluate how many

missions should take place, for a PBR to be beneficial in terms of Equivalent System Mass (ESM).

The ESM, eq. 4, considers, for a specific LSS, not only the mass (𝑀) of the system itself, but the influence of its

volume (V), power demand (𝑃), heat generated (𝐶) and required crew time (𝐶𝑇). Equivalency factors for volume (𝑉𝑒𝑞),

power (𝑃𝑒𝑞), heat (𝐶𝑒𝑞) and crew time (𝐶𝑇𝑒𝑞), which depend on the characteristics of the mission, are used to transform

these parameters into a mass unit. These parameters can be found in the literature24. The duration of the mission (𝐷)

is also required, as the crew time is defined as hours required per hours of mission. For a preliminary design phase,

the crew-time parameters are not defined with enough accuracy to allow comparison between different components,

and compared to the others, much lower. Thus, in this case, it will not be used.

𝐸𝑆𝑀 = 𝑀 + (𝑉 · 𝑉𝑒𝑞) + (𝑃 · 𝑃𝑒𝑞) + (𝐶 · 𝐶𝑒𝑞) + (𝐶𝑇 · 𝐷 · 𝐶𝑇𝑒𝑞) (4)

For the simulation task, the first step is the selection of a PC system as a baseline, secondly, the simulation of both

PC and hybrid (baseline + PBR). The analysis of the results should allow the estimation of the ESM in two-years

intervals for both designs and finally, estimate the mission duration at which the use of a PBR starts being beneficial.

The selection of a PC components is restricted by the options available in ELISSA, Table 1. Several combinations

are possible and depending on the evaluation criteria used (component mass, required resources, technology readiness

level, etc.), a different combination will be the most adequate. For this task, no specific requirements were provided

to the students, giving them completely freedom to be more conservative or risk-taking in the design of the PC system.

Before starting to use ELISSA, students are encouraged to draw a sketch of the system they have selected with the

required mass flows, to easily identify the tanks and consumables that might be needed, and obtain a better

understanding of the system they are going to simulate.

For the PC simulation, the students need to select for air, water, food and waste management the type of

components to be used, defining the number of units required and in some cases the processing level of the component.

The atmosphere conditions inside the vehicle (total pressure, percentage of oxygen, temperature and relative humidity)

also need to be defined. The program also requires information regarding the storage system: which tanks should be

included, its capacity and its initial level.

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Table 1. ELISSA library options. *also extract CO2 and produce O2

Air Management Water Management Waste Management Food Management

CO2

extraction

4BMS Waste Water

recycling

Multifiltration CO2

reduction

Bosch Algae*

SAWD VPCAR Sabatier Salad machine*

EDC

Urine

Pretreatment

AES CH4

reduction Pyrolysis

O2

production

SFWE TIMES

R-PEM VCD Solid Waste

SWIS

R-SOFC VPCAR SWC

CHX Brine

treatment AES

TCCS

For the hybrid simulation the user will need to select parameters regarding the PBR: how much food should be

substituted by the algae and if laboratory data or “ideal” data should be used for the PBR model. The ideal data is a

realistic optimization of the system, based on the combination of several experiments carried out in the IRS laboratory.

As a result of each simulation, the program provides at each step inputs/outputs, power and heat requirement of

each component, the state of the atmosphere and tank levels. This data allows evaluating of the program has behaved

as expected and identifying potential design problems. For the ESM calculation, ELISSA provides a file with a

summary of mass and volume of each tank and component, the consumables used, power used and heat produced.

With this data, students can estimate the ESM for an initial mission of two years, and calculate the required resupply

for the subsequent missions.

VI. 2017 Experience

The hands-on training took place at the IRS in May 2017. Lectures, simulation sessions and laboratory experiments

took place in consecutive weeks. The students had three extra weeks to process the data and prepare the report. This

chapter presents a summary of the laboratory results, the simulation results and an overview of the students’ feedback

and lessons learned.

A. Laboratory results

For the practical work in the laboratory, the students were divided into three groups, each responsibile for one flat

plate PBR, Figure 5, for a duration of five days. During the practical approach, the students took daily an algae sample

from their PBR and analyzed it.

The first analysis was the observation with a microscope, analyzing the distribution and homogeneity of the

individual microalgae cells within the suspension, and the presence of bacteria or other foreign objects, such as nutrient

crystals. As an example, Figure 6 shows a sample of cultivation day two, with a very homogeneous distribution of

microalgae cells and no foreign objects present. Figure 7, shows a sample of cultivation at day five from the same

reactor, where nutrient crystal and some microalgae cell clusters can be observed.

Figure 8 shows the absorbance spectrum recorded by Group 3 on the first day of cultivation. The absorbance

maxima of C. vulgaris observed are in the blue (435-455 nm) and in the red (660-680 nm) range of light.

The next measure carried out was the optical density OD680 (at a wavelength of 680 nm) of the suspension. Figure

9 summarizes the OD680 measurement data from all three groups over the whole cultivation duration of five days. An

initial drop in OD680 can be observed in the measurement data of all groups. This behavior could be explained by an

adaption phase needed by the microalgae cells, already observed in previous experiments. For all groups, the minimum

measured OD680 was reached on day two (24h into the cultivation). After this minimum, a continuous, microalgae

growth could be observed. At the end of the cultivation, on day five (96h into the cultivation), the measured OD680

data was higher than the initial value for all groups.

The students used the correlation between OD680 and dry biomass. The highest growth rates could be observed

between day four (72h into the cultivation) and day five (96 hours into the cultivation). The highest growth rates were:

0.275 g/L/d for Group 1, 0.315 g/L/d for Group 2 and 0.204 g/L/d for Group 3.

Finally, the students also measured the macro nutrient concentration within their PBR on days one, three and five.

The measurement data for the macro nutrients is shown in Figure 10 and Figure 11. For all groups, the NH4+

concentration decreased throughout the cultivation. The NH4+ values measured by the individual groups did not differ

much. For PO43-, all groups could determine a significant decrease on day three compared to their initial value. The

PO43- concentration did not show a significant change from day three to day five.

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Figure 6. Microscopic view of C. vulgaris

(400x) of Group two on day two.

Figure 7: Microscopic view of C. vulgaris

(400x) of Group two on day five.

Figure 8: Absorbance spectrum of

C.vulgaris of Group 3 on day 1.

Figure 9. OD measurement data from all groups.

Figure 10. NH4+ measurement data

Figure 11. PO43- measurement data

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In conclusion, the students were able to see, even if only for a limited period of time, the process usually carried

out to cultivate and monitor the algae in a laboratory research project.

B. Simulation results

The first step for the simulation part was the definition and simulation of the PC baseline design. For the O2

generation, all students have selected the SFWE. For the CO2 extraction, some students have selected the technology

currently in use, the 4BMS, others a potential future alternative, the EDC. Similarly, for CO2 processing, some students

have selected the Sabatier reactor, in use in the ISS (in some cases with pyrolysis, to recover the H2), while others a

potential alternative, the Bosch reactor. For the water management system, some students have decided to use the

VPCAR + AES, to avoid the resupply required by the multifiltration. For waste management, some students have

selected incineration for biological solid waste, and/or a solid waste compressor for plastics/clothes, even if such

technologies have not been used so far. As a result, nine different designs have been analyzed, some more conservative

using technologies in use, and other more innovative. The system ESM for a two-years mission range from 12 to 20

tonnes. The lower results are in accordance with the values of the studies carried out at the institute4,6. The upper range

values can be explained as in some cases, the students have oversized the technologies, the tanks or the resources

required.

The second step was to size the PBR and simulate the hybrid system. The students could select to use laboratory

data or and optimized PBR (realistic design, based on laboratory experience). The students that have selected the

laboratory data PBR model have obtained a much higher ESM for the hybrid system, than for the PC. As a result, the

hybrid system would first be useful after 8 to 16-years mission. The students that have used the optimized PBR,

already see an advantage after 1.5-2.5 years, which are similar results than the ones obtained by the research carried

out.

The students have observed in all cases, that at some point the system with PBR will present an advantage, due to

the reduction of food supply, which is time dependent. The students using the laboratory data, have obtained results

that match the data observed in the laboratory, but not with the calculation, which assumes an optimized system. On

the other hand, the students using the optimized version in ELISSA, have obtained similar values than in the manual

calculation, but far away from the observations in the laboratory. In both cases, the question raises, what should change

in the laboratory experiment, to get closer to the optimized values?

C. Students and staff feedback

After the hands-on training took place, students were asked to provide feedback regarding organization, content

and learning teaching methodology. For each question the students had to provide a score from 1 (best) to 5 (worst).

For all generic questions (i.e. satisfaction with the course, I am motivated to participate, this course promotes my

interest in the subject, I have learned a lot by attending this course, etc.) scores from 1 to 1.3 were obtained.

Since the hands-on training goals are learning-by-doing and to motivate the critical thinking of students, specific

questions were asked in that direction: “I am motivated to think along”, “practical work in the lab helps me to better

understand theoretical issues” and “the discussions contribute to a deeper understanding on the content”. In all

questions a 1.1 was obtained (eight of nine students provided the maximum score). But it is important to remark, that

it is not only a feeling of the students, as the results and discussions in the reports show that in most cases it has been

achieved.

Another interesting focus for the organization staff, was to get the students used to writing technical reports, as a

first step to write their master thesis. For that, students were given some guidelines to follow, and once the report was

corrected had the opportunity to get feedback from the teaching staff. The students have evaluated with a 1.6 the fact

of writing a report, as preparation for their master thesis. From the staff point of view, the students have improved

their technical documentation capabilities and learned in the processes.

The students have provided positive feedback on doing practical work, being able to carry out an experiment by

their own, and monitor it themselves during one week. Even if the students answered unanimously that the amount of

work was comparable to other subjects, and did not overload or underload them, students suggested for future editions

to have more ECTS (in some cases, also increasing the time in the laboratory).

The teaching staff considers this first edition a success, for the positive feedback obtained, the discussions during

the training and the results produced by the students. As a result, a group of nine motivated students have obtained a

deep training on LSS, have learn to critically look at the results obtained theoretically, in simulations and in the

laboratory, and have gained experience in preparing a technical report. That provides them a solid base, for example,

to pursue a master thesis in the LSS field.

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If the required means are available to carry out the hands-on training in 2018 and beyond, the training will continue

to take place, and if possible, the equipment will slowly be improved. In 2018, since the project PBR@LSR will be

about to fly to space, a special focus will be made to get the students as close as possible to a real flight experiment.

VII. Conclusions

The LSS working group of the IRS at the University of Stuttgart has been carrying out research on the field of LSS

for future human spaceflight for two decades. In 2017, for the first time, a hands-on training on LSS was offered to

the aerospace engineering master students. The objective of the training is to allow the students, through the research

done at the institute, to better understand and provide a deeper knowledge on LSS, than the one provided by regular

lectures. The training is included in a IRS hands-on training module, which has been offered several years at the

institute. The students need to take part in two different hands-on training options (i.e. fuel cells and sensors workshop,

rendezvous and docking training, mission analysis workshop, etc.).

The main two areas of research on LSS at the institute are the analysis of LSS for long duration missions through

simulation and the cultivation of micro-algae for space applications. Both aspects, together with some basic theoretical

lectures, are the base of the new hands-on training.

The training starts with theory lectures, including basic LSS concepts, current status of physico-chemical

components, and an introduction to biological components, both from an engineering and a biological point of view.

The lectures also included a manual design task, where students had to size an air management subsystem, using PC

technologies and a PBR.

The second part of the training is a 1-week cultivation experiment on the laboratory, making regular observations

of the algae suspension in the microscope, taking measures of the optical density (to evaluate biomass production),

the macronutrients concentration (to evaluate nutrients consumption) and the absorbance spectrum (to evaluate which

light algae require).

Finally, the software ELISSA is used to compare a PC system, designed by the students, with a hybrid system, for

a Mars surface mission with 6 astronauts. The students have simulated both designs and have evaluated the minimum

required mission time, to observe an ESM advantage of including the PBR. Depending on the technologies uses, that

range from a couple of years (for optimized systems) to 10 years (using non-optimized systems with current laboratory

data).

The evaluation was done through a max. 10-page report. The students not only have presented the results obtained,

but in most cases, also discussed critically the results obtained. The main “problem” the students had to face is that

the results from the three tasks did not match. In the manual calculation a realistic but optimized PBR system is

considered, which is not necessarily the case of the laboratory experiment carried out by the students.

Students have evaluated very positively the hands-on training, its organization and content. From the staff point

of view, the experience has been very satisfactory and as a good opportunity to prepare students for a master thesis

within the research group. The training will continue to take place in the coming years, if the required means are

available.

Acknowledgments

The authors of this paper would like to thank the University of Stuttgart, which through the

“Studienkomissionsmitteln” (SKM) has provided the required budget to carry out this hands-on training in the summer

semester 2017.

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lss hands-on research opportunities for students at the

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