University of Sydney news about the flight

School of Physics, University of Sydney news about our stratospheric flight:
http://sydney.edu.au/news/physics/1737.html?newsstoryid=10730

Launch of stratospheric balloon. Video from mini-camera installed on the cassette

The video was recorded only 21 minutes of the flight. At 5 km altitude the batteries become frozen. The highest altitude of the balloon was 27 km.

http://www.physics.usyd.edu.au/~alexey/REC_0001%20flight.AVI

It does not work in some viewers. Please, use VLC or similar. 

Snapshot: uncured prepreg in the stratospheric flight

The mini camera installed on the cassette recorded a video during the launch. The snapshot shows a part of the prepreg in the cassette over South Australia fields.

Experiment on polymerisation in stratosphere.

Last Sunday (25.11.2012) we have sent our cassette with uncured composite in stratosphere.

Konrad Schneider is holding the cassette. We tested the heater of the cassette in air and vacuum (20 Torrs) conditions.

The cassette contained uncured epoxy and polyether compositions with thermo and UV curable compounds.

The cassette was part of payload of stratospheric balloon in Horus project. 

Filling with helium.

Moving to field.

Balloon and payloads are ready. 

Three boxes of payload and the balloon in Adelaide sky.

Final altitude was about 27 km. 

Project title “Polymerisation in the Stratosphere”

We are looking for partners to make a stratospheric flight experiment

The aim: The development of polymeric material that is curable in free space environment for use as structural components in large space constructions.

Background: Future space exploration will require large light-weight structures for habitats, greenhouses, space bases, space factories and so on. A new approach enabling large-size constructions in space relies on the use of the technology of the polymerization of fiber-filled composites with a curable polymer matrix applied in the free space environment. For example, a fabric impregnated with a long-life matrix (prepreg) can be prepared in terrestrial conditions and, after folding, can be shipped in a container to orbit and unfolded there by inflating. Then the matrix polymerization reaction is initiated producing a durable composite wall or frame. Using such an approach, there are no restrictions on the frame size and form of the construction in space and the number of deployment missions is kept at a minimum.

In free space the material is exposed to high vacuum, dramatic temperature changes, plasma of free space due to cosmic rays, sun irradiation and atomic oxygen (in low Earth orbit), micrometeorite fluence, electric charging and microgravitation. The development of appropriate polymer matrix composites requires an understanding of the chemical processes of polymer matrix curing under the specific free space conditions to be encountered.

Previous studies: Our preliminary studies of the polymerization process in high vacuum, space plasma and subject to temperature variations indicate that for specific prepeg preparations the polymerization process is likely to be successful in free space and that the composite cured in a free space environment will have satisfactory mechanical properties. However, the curing processes are sensitive to free space factors such as high vacuum, flux of high energy particles and temperature variations encountered.

Particularly pertinent observations from our previous work include:

·      The evaporation of the active components can stop the curing reaction and evaporation can cause bubble formation in the curing polymer matrix and compromise the mechanical properties of the cured matrix.

·      Fluxes of high energy particles in space irradiation can destroy macromolecules and create free radicals, which can accelerate the curing kinetics and strengthen the composite.

·      Temperature variations change dramatically the curing kinetics and evaporation process.

(For details see A. Kondyurin, Curing of composite materials for an inflatable construction on the Moon, chapter in “Moon. Prospective Energy and Material Resources”, Springer-Verlag, Berlin, 2012; A. Kondyurin, M. Bilek, Ion Beam Treatment of Polymers. Application aspects from medicine to space, Elsevier, Oxford, 2008; Kondyurin A., B. Lauke, R. Vogel, Photopolymerisation of composite material in simulated free space environment at low Earth orbital flight, European Polymer Journal 42 (2006) 2703–2714; Kondyurin A., B.Lauke, E.Richter: Polymerization Process of Epoxy Matrix Composites under Simulated Free Space Conditions, High Performance Polymers. 16, 2004, p. 163 – 175; Kondyurin A.V., Building the shells of large space stations by the polymerisation of epoxy composites in open space, Int. Polymer Sci. and Technol., v.25, N4, 1998, p. 78-80).

Our preliminary studies show, that the curing process can proceed and a durable composite material can be polymerized under simulated free space conditions. However in a laboratory environment it is not possible to simulate accurately the combinations of factors observed in space in order to assess how the various influences couple. To develop the appropriate polymer matrix composition for use in a particular free space environment, the effects of the prevailing free space conditions acting together must be taken into account. In 2010 we carried out the flight experiment with uncured composite in stratosphere during NASA balloon mission and showed, that the effect of cosmic rays on crosslinking of the uncured composite is significant and well observed. More detailed investigations of the curing process under real free space conditions, where all these free space factors act simultaneously during the curing process are required.

Scientific goal of the stratospheric flight experiment:

The goal of the experiment is an investigation of the effect of the stratospheric conditions on the polymerization process in the polymer matrix of the composite material. Stratospheric conditions are expected to have a unique impact on chemical processes in polymer materials. The unique combination of low atmospheric pressure, high energy cosmic rays, high intensity UV radiation including short wavelength UV, diurnal temperature variations and other aspects associated with solar irradiation has strong influence on chemical processes in polymeric materials. Since such conditions can not be adequately simulated in the laboratory, it is difficult to predict the impact on curing chemistry which is particularly important in designing polymers which could be shaped and cured in space for large scale structural applications.

Project plan:

The experiment involves expositing a cassette containing polymer samples to the local environment during the stratospheric balloon flights. The samples consist of uncured polymer matrix and carbon/glass fibers. The polymer matrix is activated by stratospheric conditions (temperature and sun irradiation) and the chemical polycondensation reaction is initiated. Control samples, which have been cured or partially reacted prior to the flight will be included in the cassette. After the flight, the samples will be returned to the laboratory and analysed by spectral, chemical and mechanical methods. The concentration of active components, the stage the reaction reached in each composite, structure of the polymer, degradation of polymer macromolecules, crosslinking, oxidation and mechanical properties will be analysed. To help understand how the conditions couple, a parallel set of samples will be exposed to similar vacuum levels, UV light and temperature variations in laboratory experiments. These samples will be analysed in the same way as those exposed in the space flights and the results compared.

The cassette holding samples to be exposed in space has a mass of about 1 kg and dimensions with the cover installed of about 200x100x100 mm³. The total mass of the samples is about 100 g. The samples will be placed into the cassette before the flight and sealed by a cover. The cassette is to be placed and fixed on the external side (outside) of the balloon’s cabin, preferably on the sun irradiated side. The control cassettes with the same samples will remain on Earth in the laboratory.

During launching the cover of the cassette will be opened and the samples will be exposed to the stratospheric environment during the flight. Expected conditions are the following: a pressure of about 1-2 Torr, a temperature on the sunny side in the range of +80…90⁰C (during day light 12-14 hours) and -70…80⁰C (night time), a solar flux of 1300 W/m². The required flight time is 1 day or more.

The temperature, pressure and UV light intensity at the cassette will be recorded during the mission. For measurement, the cassette will be equipped with a thermistor, manometer, radiometer and a UV sensor. The data of temperature, pressure, radiation and UV light intensity will be recorded and sent to laboratory after landing.

After landing, the cassette with samples and the records of flight conditions are to be sent to the laboratory for analysis.

The chemically active polymer composition corresponds to safety rules for stratospheric flights: non-toxic, non-flammable and non-explosive.

Preferably, the experiment will be repeated during some flights because, the flight conditions may be different in individual flights. The deviation of flight conditions during different flights (temperature, irradiation exposure, pressure) will be used for analysis of kinetics of the chemical reactions. The cassette will be loaded with new samples for each flight.

Managing of the cassette operation and data recording during flight:

The cassette operation (opening and closing of the cover) can be done on command from Earth or automatically triggered by a pressure sensor to correlate with the altitude of the balloon flight.

The temperature, UV light intensity and pressure sensors can be installed in the cassette or data can be used from common sensors installed on the balloon. In the second case, the temperature, UV light intensity and pressure data must be recorded during the whole flight.

Publications about polymerisation in space environment

The idea of the direct curing in space environment came to me about 18 years ago. At that time, I was not sure, if it was done or it is impossible. All these years have been spent to get clear answer: yes, it is possible, but no, it is not done.

I met these two comments as reaction on my presentations and publications. People, who are far from space business, say, “it is done, and even ISS is done by this way!” People, who work in space industry, say, “this is impossible, but I do not know why?” All of these comments are not true.

During these years, I was carrying out a number of investigations, including experiments and theoretical calculations. Part of the results have been published and presented on conferences in different auditoriums and countries.

First time, a general way of direct curing was discussed in Russian journal “Plastic mass” (1997, No.8) and republished in English in “International Polymer Science and Technology”: Kondyurin A.V., Building the shells of large space stations by the polymerisation of epoxy composites in open space, Int. Polymer Sci. and Technol., v.25, N4, 1998, p. 78-80.

After that the further results have been published in a number of journals:

Kondyurin A., G.Mesyats, Yu.Klyachkin, Creation of High-Size Space Station by Polymerisation of Composite Materials in Free Space, J. of the Japan Soc. of Microgravity Appl., v.15, Suppl.II, 1998, p.61-65.

Kondyurin A., Kostarev K., Bagara M.V., Polymerization processes of epoxy plastic in free space conditions, Paper IAF-99-I.5.04, 50th International Astronautical Congress 4-8- Oct., 1999, Amsterdam, The Netherlands.

Briskman V., A.Kondyurin, K.Kostarev, V.Leontyev, M.Levkovich, A.Mashinsky, G.Nechitailo, T.Yudina, Polymerization in microgravity as a new process in space technology, Paper № IAA-97-IAA.12.1.07, 48th International Astronautical Congress, October 6-10, 1997, Turin Italy

Kondyurin A., High-size space laboratory for biological orbit experiments, Advanced space research, v.28, N4, 2001, pp.665-671

Kondyurin A., Kostarev K., Bagara M., Polymerization processes of epoxy plastic in simulated free space conditions, Acta Astronautica, vol.48, N2-3, 2001, pp.109-113

Briskman V.A., Yudina T.M., Kostarev K.G., Kondyurin A.V., Leontyev V.B., Levkovich M.G., Mashinsky A.L., Nechitailo G.S., Polymerization in microgravity as a new process in space technology, Acta Astronautica, vol.48, N2-3, 2001, pp.169-180.

Kondyurin A., Lauke B., Polymerisation processes in simulated free space conditions, Proceedings of the 9th International Symposium on Materials in a Space Environment, Noordwijk, The Netherlands, 16-20 June, 2003, ESA SP-540, September 2003, pp.75-80

Kondyurin A., B. Lauke, I. Kondyurina and E. Orba, Creation of biological module for self-regulating ecological system by the way of polymerization of composite materials in free space, Advances in Space Research, 2004, v. 34/7, p. 1585-1591.

Kondyurin A., B.Lauke, E.Richter: Polymerization Process of Epoxy Matrix Composites under Simulated Free Space Conditions, High Performance Polymers. 16, 2004, p. 163 – 175.

Kondyurin A., B.Lauke: Curing of liquid epoxy resin in plasma discharge, European Polymer Journal. 40/8, 2004, p. 1915 – 1923.

Kondyurin A., B. Lauke, R. Vogel, Photopolymerisation of composite material in simulated free space environment at low Earth orbital flight, European Polymer Journal 42 (2006) 2703–2714.

Kondyurina I., A. Kondyurin, B. Lauke, L. Figiel, R. Vogel, U. Reuter, Polymerisation of composite materials in space environment for development of a Moon base, Advances in space research, 37, 2006, p.109-115.

A. Kondyurin, B. Lauke, R. Vogel, G. Nechitailo, Kinetics of photocuring of matrix of composite material under simulated conditions of free space, Plasticheskie massi, 2007, v.11, pp.50-55.

A.V.Kondyurin, G.S.Nechitailo, Composite material for Inflatable Structures Photocured under Space Flight Conditions, Cosmonautics and rockets, 3 (56), 182-190, 2009.

A.V.Kondyurin, L.A.Komar, A.L.Svistkov, Modelling of curing of composite materials for the inflatable structure of a lunar space base, Journal on Composite Mechanics and Design, 15 (4), 512-526, 2009.

A.V.Kondyurin, L.A.Komar, A.L.Svistkov, Modelling of curing reaction kinetics in composite material based on epoxy matrix, Journal on Composite Mechanics and Design, vol. 16, no. 4, pp. 597-611, 2010.

A. Kondyurin, M. Bilek, Etching and structure transformations in uncured epoxy resin under rf-plasma and plasma immersion ion implantation, Nuclear Instruments and Methods in Physics Research, B 268, 1568–1580, 2010.

A. Kondyurin, Direct Curing of Polymer Construction Material in Simulated Earth’s Moon Surface Environment, Journal of spacecraft and rockets, V. 48, No. 2, pp.378-384, 2011.

A.V.Kondyurin, L.A.Komar, L.A. Svistkov, Modeling of the kinetics of the curing reaction of the epoxy binder-based composite material, Nanomechanics science and technology: An international journal, vol.2, issue 2, 167-183, 2011.

A. Kondyurin, L.A. Komar, A.L. Svistkov, Combinatory model of curing process in epoxy composite, Composites, part B, 43, 616–620, 2012.

In my two books:

A. Kondyurin, Curing of composite materials for an inflatable construction on the Moon, chapter in “Moon. Prospective Energy and Material Resources”, Springer-Verlag, Berlin, 2012, p. 503-518.

A. Kondyurin, M. Bilek, Ion Beam Treatment of Polymers. Application aspects from medicine to space, Elsevier, Oxford, 2008

In Cornell University Arxiv.org site:

A. Kondyurin, I. Kondyurina, M. Bilek, Composite materials with uncured epoxy matrix exposed in stratosphere during NASA stratospheric balloon flight, http://arxiv.org/pdf/1008.5236

A. Kondyurin, I. Kondyurina, M. Bilek, Radiation damage of polyethylene exposed in the stratosphere at an altitude of 40 km, http://arxiv.org/pdf/1109.5457v1

The recent experiment has been done on the curing in stratosphere. First time, it was shown, that cosmic rays play role of additional hardener for the polymer. Space makes polymer harder. This real flight experiment supported previous laboratory investigations and made me sure, that it will work in real space flight.

If you are interested in and do not have subscription for these journals, please, ask me, I will send you a copy. 

Curing at space temperatures

Well, go to next problem. Temperature.

The temperature in space is tricky. Usual imagination, what we have on Earth, does not work there. Imagine: there are no walls, furniture, ground, neighbours, friends and wind (air) surrounded your body. Temperature depends on the irradiation from the Sun and on internal sources. All bodies irradiate following Stefan–Boltzmann law. 

If no irradiations from neighbours, your temperature goes to absolute zero, well, not zero, because of space irradiations. But anyway, it comes to very low temperature; the space flight measurements give temperatures about -150 C. If you are irradiated by the Sun, your sun-side will be heated up in dependence on reflectivity of your surface, thermocapacity, thermoconductivity and geometry of your body. Very quickly you start to feel, that one side of you is burning (can be +150 C and more), while the other side is still frozen. You will want to turn. If you turn quickly enough, your temperature will be more or less steady. So, the rotation of the body is very important.

Now let’s remember, how the chemical reaction depends on temperature. At first approximation, the rate of reaction follows Arrhenius law: the rate increases with temperature. Usually, the curing system is selected to be non-reacting at storage temperatures so, that uncured material can be kept in container at transportation without the reaction. Therefore, the temperature at curing should be higher than on Earth and at transportation.

There are some ways to get it. First of all, rotation of the construction side by side to the Sun should be so, that each part of the construction will be heated enough to be cured completely. It does not need massive efforts, because no friction there, and if the construction is accelerated it will rotate forever. You have to be smart enough to calculate the rotation speed and direction. It can be calculated, measured, compared with experiments on orbit. The regime of rotation can be optimised to get complete curing in all sides and parts of the construction.

But what can you do on the Moon or on an asteroid? You cannot rotate the Moon of asteroid as we want. If you are settled down on equator of the Moon, you can expect heating enough with the turning of the Moon. But if your construction has to be placed on polar, what is more likely because of found water there, there is no way to get a heat enough. You have to heat it with internal sources, for example, with internal electrical heaters. And you have to be ready to spend a lot of energy during curing reaction. It is not a huge amount of energy: ISS astronauts spend a comparable amount of energy to support life there. The construction can be heated partially: sector by sector, that can decrease an amount of power, you have to apply.

Another way is to use photocuring reaction. There are compositions that can be cured under UV light. That’s nice way if you need to cure quickly, on command after storing long time in the container. In such case, the curing reaction is not so sensitive to the storage temperature, while the rate of curing anyway depends on temperature. Such photocuring systems can be suitable for repairmen set. But the photocured materials have usually lower mechanical strength, lower radiation stability, shorter life-time and narrower diapason of exploitation conditions, than thermocured materials. These two kinds of materials (photocured and thermocured) are specialised for different constructions. You can choose one of them for particular construction and exploitation conditions.

However, there is a serious problem with the temperature in space: thermostresses. This problem needs attention. Usually, on Earth the prepreg (uncured material) is placed into curing oven, heated slowly with optimised rate of the temperature increase, cured at uniformly distributed temperature, and cooled slowly. The heating/cooling process is optimised to avoid the thermostresses in the construction. In space, when the construction is irradiated from one side, the Sun irradiation creates a temperature gradient. The curing reaction follows to the temperature gradient in the construction. Therefore, the different parts of the construction will be cured at different temperature and will keep memory of the temperature gradient. When the cured construction changes an orientation, the temperature gradient changes and it generates the stresses. As higher temperature gradient is at curing, as higher stresses appear. The stresses deform your construction and decrease the mechanical strength of the construction.

Because no one large curing oven with temperature stabilisation is installed in Earth orbit, where you can put your construction for precise curing, the temperature regime of the construction should be precisely calculated and the flight regime should be optimised to get completely cured material of the construction without significant stresses.

Curing in free space plasma

Free space plasma, deadly space irradiations, burning Sun light. Who can live there? What material can survive there? For how long? – Hopeless questions. That’s enemy environment for all Earth-born stuffs.

All materials, including polymers, degrade in space environment under high energy cosmic rays, Sun wind, atomic oxygen of residual Earth atmosphere (if Low Earth Orbit). Since first space flights, engineers worry about degradation of the materials used for space ships, satellites, stations. A number of experiments have been done, when different kinds of materials were exposed on Low Earth Orbits. Then the materials were delivered on Earth, to laboratories for an investigation. The structure changes in all polymer materials have been observed, described, calculated and simulated in laboratory experiments.

First of all, this is an effect of etching. The materials disappear with time: layer-by-layer. You can find a rate of etching in literature for different kinds of materials. There are handbooks, database, standards and recommendations how to choose a right material based on mission, orientation, lifetime and functionality of materials in particular space construction.

At second, the materials become brittle, cracked, and finally broken under space conditions. The molecular structure changes significantly: polymers become crosslinked, depolymerised and oxidised in dependence of kind of polymer. All these effects in polymers can be observed in laboratory under plasma and high energy particles. The chemistry of these processes is based on generation of free radicals, when a high energy particle hits a macromolecule and forms free radicals. The free radicals are very active and start to react with neighbour macromolecules. These chemical reactions transform the initial macromolecules dramatically.

The same radiation effects are observed in macromolecules when uncured polymer with liquid matrix is exposed in UV light, g-irradiation, X-ray beam, plasma and ion beam. 

At first, the etching rate is higher. The uncured polymer degrades quicker than the hard polymer. We measured it. But the difference is only 2 times. Is it significant? Yes, for first two-three hours. But then the polymer becomes hard and stays 15-20 years. Therefore, the contribution of high etching rate, when the polymer was liquid, is neglectable in comparison of low etching rate at the rest of life. 

At second, the radiation damaging of the macromolecules is the same. The generated free radicals in matrix can cause two kinds of reactions: crosslinking and depolymerisation. If right composition is selected, the crosslinking reactions proceed and the polymer matrix becomes hard. The same effect as in curing reaction, but without any hardener! Therefore, the free space environment can play a role of additional initiator of the crosslinking reaction. 

"The space makes polymer hard", as the journalist wrote about our investigations. That’s true, in the case of uncured composite the enemy space environment helps us to get durable material. Let’s use this help smartly. 

About curing in vacuum

Well, let’s consider the problems of polymerisation in space: first of all is vacuum.

Low pressure of free space environment is a problem for all materials, constructions and human during a space flight. This is unusual in comparison what we have on the “bottom” of our air “ocean”.

At first, the residual gases can inflate the shell of the construction shortly after launch, when the container with folded shell is lifted to space. The inflation pressure is very low, if outer pressure becomes neglectable. This was a reason of some failed space flight missions when large shell was inflated in Earth orbit, but the uncontrolled inflation broke the shell. The inflating pressure is close to vapour pressure of cured (hard) polymer materials, which always contain some dissolved gases, low molecular fractions and residual solvents. The presence of residual gases is so dangerous, that the polymer shell can inflate spontaneously after opening of the container.

What will be, if a liquid resin with high vapour pressure will be placed into the hermetic shell? Explosion. This is why most projects on inflation space construction with uncured material inside are not realized. No one of material experts in space agencies agrees to sign permission, that the shell with liquid resin inside will be deployed under control.

Can we manage it? Yes, we can.

The prepreg with liquid resin should be placed on external side of the inflating shell. In such case, the evaporation of liquid resin will be into space. The inflation process of the shell remains dangerous due to shell vapour pressure, but with special ventilation we can decrease the pressure caused by evaporation of low molecular components from the shell material. And the high vapour pressure of the uncured resin will be not important for the inflation.

You can ask me:

- wait a minute, it means, that the uncured liquid resin will be placed directly into space?

- Yes!

- But the resin components will evaporate and disappear with time. Nothing will remain for curing!

- Yes, if a composition of the resin is wrong. Some people from ESA tried it, failed and said: “curing in vacuum is impossible”. However, if the composition is right, the evaporation of components is not a problem.

How can we select a right composition?

Look, if you put a glass of water in vacuum chamber and pump it, after some time you will see, the water evaporated completely. If you put a glass of ethylene diamine (the hardener for epoxy resin) into vacuum chamber and pump it, the ethylene diamine will evaporate too. However, if you look at the door of vacuum chamber, you can see a rubber O-ring. It is used for hermetisation of the vacuum chamber door to prevent air coming. This O-rig does not disappear after long pumping at extremely low pressure and temperature. You see, there are soft substances that can survive in vacuum. Actually, all materials evaporate in vacuum including metals, the question is: how fast? We must select substances suitable for the curing (active) and survival in low pressure (slow evaporation).

To estimate the dangerous of evaporation, we have to consider a curing reaction of the polymer matrix together with evaporation. In literature you can find plenty information about kind of curing reaction, some of active compositions are certified by space agencies to be used in space for construction materials. All of these materials consist of minimum two components: resin and hardener. The reaction of polycondensation is mostly used for curing of such kind of materials. It means, that the ratio of resin and hardener is usually optimised to get durable composite after curing. If one component is lost, the composition remains uncured and the material lost mechanical characteristics.

Therefore, the right composition should provide low evaporation rate for both active components: hardener and resin, and the rates of evaporation should be similar for all active components.

The second problem is cavitation. When uncured liquid composition contains a lot of low molecular fractions (it does not matter, if they are active or not) and these fractions evaporate fast, the composition becomes bubbled in vacuum. These low molecular fractions evaporate too fast and the vapours are collected into bubbles. If the composition becomes harder with time, the bubbles cannot move to the surface, stop and form foam. You can see it, if you buy liquid polyurethane in nearest tool shop and make polyurethane foam. Similar foam was observed in NASA space experiment during space flight and they said: “curing in vacuum is impossible”.

Therefore, the right composition should not contain low molecular fractions which can make bubbles and foam in vacuum.

If the composition does not break the curing reaction and does not give a foam in vacuum, it can be cured in space. That’s just right selection based on knowledge of the evaporation rates, composition components, curing kinetics and some experience. We have found and tested some compositions up to 10^-5 Pa pressure. They are not expensive and not rare. Some of them in cured form are certified for space constructions can be used now.

If pressure becomes lower than the vapour pressure of the components (10-100 Pa for liquid epoxy resins, for example) and the evaporation has been started, a following decrease of the pressure does not play a role. For example, if the pressure in Low Earth Orbit is 10^-5-10^-7 Pa (while the pressure near spaceship depends on sun irradiation, how long is the ship in the orbit, material of the ship walls and so on and it is usually higher than the pressure far from the ship), the evaporation will have similar effect on the curing material as in deep space, when the pressure can be 10^-11 or lower (if no one has been there and did not put his gases, I mean evaporation). Therefore, the compositions tested in Earth orbit can be used on Moon, on asteroids, in Jupiter’s orbit and in another galaxy.

So, a curing of liquid composition in vacuum is not a problem, while some official referee of my project in Europe said: “that’s impossible!” and rejected the project.

Project:”Large-size antenna dish, shield and frame of space station by the way of polymerization of composite material on Earth orbit in free space environment”

The main goal of the project is the development of the polymerization processes of polymer composite materials in free space environment and the creation the technology for large-size constructions on Earth orbit.

The size and mass of modern space constructions (antenna, space satellite, space station or space base) sent to the Earth orbit are limited by possibility of a launch vehicle. The large-size construction can be created by the use of the technology of the polymerization of fibers-filled composites and a reactionable matrix applied in free space or on the other space body when the space construction will be working during a long period of time. For example, the fabric impregnated with a long-life matrix (prepreg) is prepared in terrestrial conditions and, after folding, can be shipped in a container to orbit and kept folded on board the station. In due time the prepreg is carried out into free space and unfolded by inflating. Then a reaction of matrix polymerization initiates. After that, the artificial frame can be fitted out with the apparatus or used for any applications.

In this case, there is no limitation for size and form of the space construction, there is no necessity for some launch vehicles for the creation of high-size space construction.

However, conditions of free space have a destructive influence on polymer materials and especially for uncured polymer matrix of composite. In the free space the material is treated by high vacuum, sharp temperature changes, plasma of free space formed by space rays, sun irradiation and atomic oxygen (on low Earth orbit), micrometeorite fluency, electric charging and microgravitation. Our preliminary studies of polymerization process in high vacuum, space plasma and temperature variations showed that the polymerization process is available in free space under space factors and the composite cured in simulated free space environment has satisfied mechanical properties.

The present project includes:

- Investigation of the polymerization process and structure of selected composite material in simulated space environment;

- Test of polymerization of selected composite material during space flight;

- Development of large-size mirrors, antennas (some km diameter) and frame of space construction (for example, cylinder of 100 length and 10 m diameter) on Earth orbit by way of curing of polymer composite materials in free space.

Dr. Alexey Kondyurin

We have 55 years space flight history today, but we are still here, near Earth. Dreams on exploitation of other planets, asteroids, stars are as far as 55 years ago. Prospective programs of all space agencies do not include real plans for human mission far space. Only talks, talks, talks. Why? Why are we anchored on Earth? Why do we only dream about other planets and make movies?

The Moon is the nearest celestial body to our Earth. Man first visited the Moon in 1969. Why it was stopped? You say, it is too expensive?

No. The problem is that we can do nothing there: in space, on Moon, on Mars. Look our “modern” spaceships. Could you live in “fish-box” some years? Could you develop mining on asteroid if your “home” is 3x6x6 meters, where you can take out your hermetic spacesuit?

No. We need large construction in space. In order for long-term human missions to be possible, large pressurized construction is needed.

Let’s look what we have and what do we plan now. The 6.65 m3 pressurized crew compartment volume realized in Apollo program. MIR space station had 350 m3 pressurised volume. Completed ISS after  more than 10 years of building has 109 m length and total volume of 837 m3.

What do we need for real long-term space mission? Hundreds of cubic meters for one crewmember are required for living area, working area, greenhouse with sufficient plants and animals for food, air and water recovery and storage. We cannot go further without significant improvement of living space in space.

It is real barrier for space programs, space missions, space industry, space exploitation. No way further without breakage of this barrier.

The projects discussing such large metal constructions delivered from Earth were proposed since the first flight on Moon. However, this method is not realistic: such large construction cannot be launched from Earth (too big mass and size). Large construction cannot be landed on the Moon (too big inertia). Such large constructions should be extremely durable to survive under huge accelerations at start and at landing (if landing on Moon or Mars). Building of large construction in space requires a long presence of workers (workers need pressurized cabins, life support system, water, food, that needs large construction to deliver and to keep it), delivering of separate blocks to one place with landing rockets (accuracy of landing in some meters is too complicate, or it needs Moon’s/Mar’s tracks to collect all landed blocks). Experience with building of ISS (International Space Station) showed, that the module building is extremely expensive, need much more launches and time and resources, than planned before, it takes years to finish. But the volume of whole ISS is enough only for 1 crewmember for far space mission!

You can say: robots will build the construction. Yes. Sure. I agree, in next 100 or more years. No one house has been built by robots on Earth by now. No one man lives in such house. It is too complicate. But space environment is much more complicate, than your smooth land with developed communications, roads, suppliers.

Therefore, a large construction in space should be built it-self.

There is only one way to get sufficient volume of the pressurized crew compartment: an inflatable construction. The soft shell of inflatable construction can be prepared on Earth, folded and transported in small container to space. Then the shell is inflated to a sufficiently bigger volume than the container. The shell materials should be soft to unfold easy and light to provide low mass.

Space agencies have an extensive experience in inflatable constructions. The history of inflatable space structures started from the "Echo", "Explorer", "Big Shot" and "Dash" balloon satellites in the 1960s. Based on success of the balloon satellite flights new projects utilizing inflatable structures for antennas, reflectors, Lunar and Mars houses and bases, airlocks, modules based on light polymer films were proposed from that time. Some of inflatable structures based on new materials were successfully (and sometimes unsuccessfully) tested in real space flight.

However, inflatable structures haven’t had a wide application in space exploration because of high risk of damage of the soft inflatable shell. Of course, the shell could be made of thick multilayers (Spacehab project), but the shell becomes heavy and the advantages of inflatable construction disappear.

The use of inflatable construction in space environment needs a rigidization of the construction wall after inflating. Since the first inflatable constructions flights, several methods of rigidization have been discussed: rigidization due to chemical reaction of a soft polymer matrix by thermal initiation of reaction, by UV-light initiation and by inflation of gas reaction; mechanical rigidization due to a stressed aluminum layer in the deployed shell; foam inflation; passive cooling below Tg of material; evaporation of liquid from gel. In some cases a combination of hard and rigidizable structures was developed. All of these methods were tested in Earth laboratory experiments. Only one real mechanism of rigidization was successfully tested in real space conditions - Aluminum stressed layers. However, this method is not suitable for large space construction.

The best way of rigidization is a chemical reaction in polymer matrix impregnated by fiber filler, which gives a durable composite material. These materials were tested under superior conditions including real space flight experiments. These materials are used for a wide number of space constructions now on Low Earth Orbits (LEO) and Geostationary Earth Orbits (GEO). These materials have long life-time (up to 20 years) under free space conditions and certified in all space agencies. Therefore, the chemical reaction rigidization process is the best method to be used!

For the creation of the construction frame, the fabric impregnated with a long-life matrix (prepreg) is prepared in terrestrial conditions, which, after folding, can be shipped in a space ship to the Earth orbit, Moon, Mars or other planet. The curing process should be slow to keep the prepreg soft. In space the prepreg is carried out and unfolded by, for example, inflating an internal bag. Next the chemical reaction of matrix curing should be initiated. The reaction can be initiated with high temperature or UV light irradiation. The required temperature for the chemical reaction can be achieved with Sun light irradiation or with internal heaters inserted in the prepreg. If the curing reaction requires UV light for the initiation, the sun light or UV lamps can be used to illuminate the prepreg. After complete curing the construction can be pressurised, fitted out with the apparatus and life support systems.

However, the curing technology of the composite material in space is not yet developed. The curing process in terrestrial environment is different than it will be in space. The prepreg cannot be placed in thermobox for precise temperature cycle, as it is used on Earth. The prepreg cannot be kept at Earth atmospheric pressure to prevent evaporation of active components. The composite material cannot be tested after curing to be sure in strength and exploitation characteristics of the material as it is usually done for construction materials on Earth. The curing technology in space will use different principles of composition, curing, testing as on Earth. It should be well developed and proved.

The main factors of space environment are high vacuum, space plasma (different kinds of irradiation, cosmic rays, Sun wind, atomic oxygen flux on Low Earth Orbit), sharp variation of temperature, microgravity (in orbit flight). All these factors influence on the curing process.

We have investigated the curing process in different compositions: under high vacuum, plasma and ion beams, in wide temperature variations. We found curable compositions for space environment. We found, that space plasma will help us to cure the construction wall. We tested mechanicals strength of the materials, that were cured under simulated free space conditions. It works! 

Conclusion: a curing in space is possible.

What is now? We need to test our composition in real space flight and then we can build large construction in space. A building of 10 m diameter and 80 m length after one launch is enough for your space factory?