SAM at REXUS Selection Workshop at ESA's ESTEC

Last week, Strathclyde's StrathSat-R traveled to ESA's ESTEC in Noordwijk, the Netherlands to present the sounding rocket experiment which should serve as a technology demonstrator for the Self-inflating Adaptive Membrane (SAM) concept. The workshop was organised by the German Aerospace Center (DLR), the Swedish National Space Board (SNSB) and the European Space Agency (ESA). Teams from across Europe presented their experiment proposals, there where 14 presentations in total, seven for the balloon and seven for the rocket. REXUS/BEXUS will probably select three to four experiments each. StrathSat-R's presentation went quite well and received good comments and suggestions from the expert selection board. REXUS/BEXUS will announce this Friday which experiments got selected for the upcoming campaign with a sounding rocket launch in March 2013.

Vacuum test of first prototypes

The first vacuum test of SAM’s hexagon elements was performed yesterday in the physics department of the University of Strathclyde. This vacuum test should prove if the residual air approach is working as expected. Furthermore, the test was used to validate the usability of various membrane materials and manufacturing techniques. The vacuum test showed that the residual air inflation works quite well and that the deformations observed are similar to the LS-DYNA simulation. The single hexagon seen in the picture is manufactured of two thin sheets of Mylar joined together by applied heat. Other prototypes were manufactured out of Kapton, polyethylene and solar film. Further research will focus on the improvement of the reliability of the seam lines.

Prototype manufacturing commences

Two weeks ago, manufacturing of inflatable samples started at the University of Strathclyde with the help of 4^th year student Adnan Mahmood. The research is focused on the behaviour of various membrane materials and manufacturing techniques in regards to SAM. The materials tested are polyethylene, Mylar, Kapton and solar film. The first prototype of one hexagon was completed yesterday (see picture). For this afternoon, a first vacuum test is scheduled to investigate the deployment behaviour of the hexagon with the residual air approach.

Deployment Simulations for SAM

Currently, deployment simulations of SAM are carried out in order to observe the performance of the membrane from the packed compressed state to the inflated flat shape. The program LS-DYNA is used for this kind of simulation due to its capabilities in inflation simulation (airbag simulation). The control volume method is used in this simulation due to its simplicity by subjecting the inside of the inflated membrane to a uniform pressure. The simulation was started with just one hexagonal element to validate if LS-DYNA can be used for the deployment simulation due to the fact of the rather computational expensive calculation necessary for the simulation. It could be concluded that the simulation performed quite well and it was decided to carry out deployment simulations on the possible sounding rocket set up of SAM with 18 hexagonal elements resulting in a diameter of roughly 80 cm in full deployed configuration (from a stored volume of 10x10x4cm³). Different folding patterns of the membrane are considered at the moment to fit it into the 10x10x4cm³ volume available in the StrathSat-R cube satellite.

Paper on SAM accepted for AIAA Structures Conference

The abstract on "Design and Development of a Deployable Self-inflating Adaptive Membrane" focusing on the concept and design of SAM, just got accepted for the 13th AIAA Gossamer Systems Forum (as part of the 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 20th AIAA/ASME/AHS Adaptive Structures Conference, 14th AIAA Non-Deterministic Approaches Conference, 13th AIAA Gossamer Systems Forum and 8th AIAA Multidisciplinary Design Optimization Specialist Conference) from the 23rd - 26th of April 2012 in Honolulu, Hawaii, USA.

The paper will be presented on the 24th of April in the session GSF-01, Inflatable Structures.

SAM got shortlisted for the upcoming REXUS campaign

SAM got recently shortlisted for REXUS (Rocket-borne Experiments for University Students), a DLR/SNSB/ESA funded programme that gives student teams the possibility to launch experiments on sounding rockets into micro gravity (100km altitude). SAM will be on one of two cube satellites as part of the StrathSat-R experiment deployed from the sounding rocket. The Selection Workshop will take place from the 5th to the 9th of December at ESA ESTEC in Noordwijk (NL).



Description of the experiment StrathSat-R:
For the success of future space missions involving large space structure, the development of new deployable structures and the improvement of current designs are of great importance. StrathSEDS, a sub-division of UKSEDS at the University of Strathclyde (Glasgow, UK), developed StrathSat-R therefore to validate different inflation deployment techniques in space conditions. The StrathSat-R experiment consists of two distinct sections that are based on a 1U cube satellite (10x10x10 cm3) outline. The primary objective of both satellites is to deploy a structure in micro-gravity by using inflation. After inflation, the two free-flying units have different specific objectives: The aim of the first cube satellite, FRODO (Foldable Reflective system for Omnialtitude De-Orbiting ), is to deploy and then rigidise a large reflective sail from a 1U cube satellite sized pod. After the deployment of the reflective sail, the de-orbiting manoeuvre takes place completely passively. This research could open up new high altitude orbital regimes for future pico- and nanosatellite missions. The scientific objective of the second cube satellite, SAM (Self-inflating Adaptive Membrane), is to serve as a technology demonstrator for the residual air deployment method with a novel hexagon element design approach. The big advantage of the hexagonal element approach is that a structure can be obtained which is simultaneously stiff and flexible due to the stiff pillow elements and the flexible seam lines. The second goal of this endeavour is to develop a structure that can adapt itself to various environmental conditions. For example, the structure could serve as a substructure for a solar concentrator and adjust its focal point autonomously by changing the curvature of the entire structure. Both cube satellites will be recovered after impact with the ground.

What is SAM?

SAM (Self-inflating Adaptive Membrane, developed by Thomas Sinn (advisor: Dr. Massimiliano Vasile) at the University of Strathclyde) is a new concept of a modular deployable multi-functional structure that can adapt itself to various mission conditions. SAM can operate as a reflector, as an antenna, as an extended solar array or as solar sail for example. The developed membrane is a modular passively inflatated structure made of basic triangular elements connected through shape memory alloy wires, enabling shape change with small applied current levels.
The composition of all the triangular elements forms an extended surface that can change the shape of the entire structure and fulfil multiple configurations. The big advantage of the triangle element approach is that a structure can be obtained which is simultaneously stiff and flexible due to the stiff pillow elements and the flexible actuation lines. The adaptive material will allow the extended surface to change its curvature and become a reflector, to change the focal point of the reflector, to maintain a flat surface or to change the orientation of part or the entire surface and induce an angular momentum. The current design of SAM envisions one side inherent a reflective surface while the opposite side is covered in thin film PV cells. By controlling the shape one could control the attitude and therefore face the PV side of the surface to the sun or alternatively point the reflective side.
The testing and validation of the deployment of this modular multifunctional structure is planned to happen through a suborbital flight within the upcoming REXUS (Rocket Experiments for University Students, a DLR/SNSB/ESA funded program) campaign. SAM will be deployed from a 1U cube sat and will demonstrate the deployment and surface control technology in microgravity. The next step is to install SAM on a 2/3U cube sat.