The Theory of Integrated Sticks

2015 IEEE International Conference on Robotics and Automation (ICRA), 2015

As the number of rocket bodies and other debris in Earth's orbit increases, the need to capture and remove this space junk becomes essential to protect new satellites. A low cost solution may include gecko-inspired directional adhesives, which require almost no compressive preload to generate adhesion and are therefore suitable for surface grasping in space where objects are free floating. Current individual adhesive units with a pair of opposed pads achieve a limit of 13N normal to the surface. Instead of using a single large unit to generate high levels of adhesion, using multiple small gripper units is desirable to prevent single-point failures and to conform to higher curvatures. For this strategy to succeed, it is essential to distribute the overall force evenly, to minimize the overall preload normal to the surface, and to prevent local failures from propagating over the array. We present two load sharing mechanisms. The first uses nearly-constant force springs in parallel. The second uses a tendon and pulleys in series. Both allow a 4-unit gripper to maintain the same adhesive stress as a single unit. A normal adhesive load to compressive preload ratio of 100:1 is demonstrated. Zero gravity experiments and air bearing floor experiments demonstrate the gripper's functionality in a simulated space environment. Design considerations are discussed for further scaling, with the trade-offs among load sharing, suitability for different surfaces, and failure sensitivity.

1994

The design of a solar sail space vehicle with a novel sail deployment mechanism is described. The sail is triangular in shape and is deployed and stabilized by three miniature spacecraft, one at each corner of the triangle. A concept demonstrator for a spherical microrover for the exploration of a planetary surface is described. Lastly, laboratory experiments have been conducted to study the migration of thin oil films on metal surfaces in the presence of a thermal gradient.

Physics of Fluids, 2013

2011

The space elevator should offer access to space at a cost orders of magnitude lower than possible today, changing the appearance and scope of space travel itself. The elevator has two major conceptual advantages over rockets that should lower operational cost. Firstly, the energy required to climb the tether does not have to be stored on board of the delivery vehicle, but can be e.g. transmitted from the ground by laser or by electrical power through the cable. Secondly, the energy spent can be partially recovered as the delivery vehicle and its return cargo descends. As a result of the steep drop in cost, rapid developments could be expected, as have happened in recent years for personal computers and mobile communication. For large multi stage rockets it would mean they would become all but obsolete. The use of satellites for any purpose would however become commonplace, and so would commercialization of space as well as human exploration of the solar system. For orbital transfer less ambitious than the bolo systems one can avoid the requirement of spin up that is inherent to a rotating tether system. A pendulum motion can be sufficient in some cases and it is readily achieved as a side effect of deployment. A well timed payload release from a swinging rather than rotating tether can be an effective way of changing orbit for both endmasses through the principle of momentum transfer. An example is the delivery Chapter 1 Year Experiment Length [km] Technology Objective Success Remark Ref. Gemini 11 Gemini 12 0.036 0.04 Mechanical link between Gemini and Athena upper stage Artificial gravity Gravity gradient stabilization YES MOSTLY Spin stable 0.15 rpm Manned with manual control NASA 1967 TPE 1 TPE 2 Charge 1 Charge 2 Charge 2B 0.04 of 0.4 0.07 of 0.4 0.418 0.426 Part II, the development, therefore narrows down on the SpaceMail application. It focuses on the design, development and qualification of a tether system for a demonstration mission. Chapters 4 is concerned with the development and assessment of a suitable material and tether design. As tether induced collision risk has been identified as a primary show stopper for past mission proposals, particular attention is paid to the design s implications for safety. Possibilities are explored to decrease risk both during and after studies have been performed by Erik and myself jointly. I developed the risk analysis approach and performed and analyzed many of the simulations. The bare tether as fail safe concept is my idea. The plasma chamber tests at IFSI CNR were performed and analyzed for us by F. de Venuto & G. Vannaroni. M. Dobrowolny provided a sneak preview into his dynamic models for comparison with our simulations. The multi point sensing options are generated by Joe Carroll, Erik and myself. The deboost study was supported by ESA ARCOP contract 14621/00/NL/MV. Bas Lansdorp at Delta Utec came up with the rimspeed as critical parameter for the artificial gravity comfort zone ("no tether no comfort"). He also made many of the MARS g trade offs and designed the HELD deployer. The self accelerating rotating tether for stable deorbit (LeBRETON) is my idea, Alexander van Dijk at Delta Utec worked out a lot the details for the Jupiter case. Overall it has been a joint effort including also Erik and Prof. Juan Sanmartin, funded by ESA/ESTEC contract 17239/03/NL/HB. Chapter 4. Thanks to Martien Jacobs, Daan Tummers, Joyce Kersjens, Hans Plug at DSM High Performance Fibers and for their advise on Dyneema® and helpful discussions. All at ESTEC/QMC (Marc, Jacco, Andreas, Gerard, ...) & Antonio Araujo for providing and operating the test facilities and a lot of support. Prof. Guillet for the E/CO and MVK samples. Pieter Gijsman at DSM research provided chemistry advice and performed the GPC and FTIR tests. The degradable tether study was supported by ESA contract 13746/99/NL/MV. Andrew (break strength), Igor Sheynikov at Delta Utec (damping, ripstitch) and Center of Expertise in Reggio Emilia (stiffness) were a great help with the material tests. Igor also helped me with the barberpole test in vacuum, performed at the SSAU. The YES2 Center of Expertise in Samara was led by Igor Belokonov. Chris Blanksby did the Foton tether interaction simulations. Joep Breuer came up with the Prusik knot idea, it proved to be Columbus egg. Chapter 5. The Rapunzel deployer is a brainchild of Manfred Krischke and Dieter Sabath, built by Werner Kast and Mario Kowalchyk with whom Erik and I tested it in zero g. The YES2 breadboard barberpole is designed by Carlo Menon at Delta Utec, he also devised the conceptual trade offs. The YES2 flight hardware by the YES2 Center of Expertise in Patras and our students in Delta Utec. Bradford Engineering manufactured it. Marcel van Slogteren and colleagues at the ESTEC workshop helped out a lot. Thanks to Kayser Threde and Christian Knueppel of the TSE team for the opportunity to do the deployment tests and for the TSE breadboard long term loan afterwards. I often think back of the 21 day stay with Erik in a tent in Rostock. TSE was an ESA GSTP project. Prof. Ferdi Hermanns at the YES2 Center of Expertise in Remagen/Krefeld is the source of the great textile industry ideas in winding and unwinding rig. These rigs are truly an extensive effort, involving many of Hermanns students. I am most indebted to the builders of the first version: Stefan Zwick, Joerg Malchus, Thomas Betz, David Schaefer, the builders of the second version: Mario Timmermanns and Christian Camps. Andrew again helped a lot and performed many of the YES2 unwinding tests. We even lived together in Krefeld for I do not know how many months to get these things running properly. I was particularly supported with the last but not least improvements for the third and final version and long nights of tether winding by Florian Helling and Marco Stelzer (an ace on the "Winding machine DeLuxe"), at Delta Utec and ESTEC. Thanks to Marco again and Paul Williams for the help with the control algorithms. Mathieu Mirmont programmed the flight model of the OBC (I was allowed to do only the breadboard). Ilias Spiliotopoulos and Rafal Graczyk programmed and built the flight stepper driver. The Chapter 5 early work and YES2 design phase were mostly funded by Delta Utec. The brainstorm phase, the Centers of Expertise and the flight hardware development were funded by the ESA Education Office. Chapter 6. I thank Erik, Prof. Ockels, the Delta Utec students, the ESA staff, the ESA Young Graduates, Tether Applications, Arthur C. Clarke, TNO and Bradford Engineering for their help. ESA, NIVR & Delta Utec funded YES. Chapter 7. The FLOYD, MASS and Fotino have been designed, built and tested under my lead with the help of 100 Delta Utec interns, and about 80 other students at the 4 YES2 Centers of Expertise, in Warsaw and scattered elsewhere around Europe. Thanks to Fabio De Pascale (the integration manager) and all ESA staff that supported us. Emxys in Elche, Spain supported the electronics development, as well as Bernard Ouwehand and Bradford Engineering. Chapter 8. Thanks to the ESA Human Spaceflight microgravity department, the ESA Education Office and TsSKB to make the YES2 mission possible, in particular Antonio Verga and Ruedeger Reinhard for their genuine interest. Tom and Christophe at RedShift for providing the excellent DIMAC data. Receiving data from your own space experiment is exhilarating, but that joyful moment may not by itself balance the efforts that needs to be invested to get it done. Having worked with so many dedicated young people so closely, and with a shared goal, certainly does.

Space tethers are cables that connect satellites or other endmasses in orbit. The emptiness of space and the near-weightlessness there make it possible to deploy very long and thin tethers. By exploiting basic principles of physics, tethers can provide propellantless propulsion and enable unique applications such as the provision of comfortable artificial gravity or the removal of space debris. Nevertheless there are still no tether applications in use today - there appears to be a "gap of scepticism". A safe tether and deployer system has therefore been designed and verified with the help of simulation and innovative ground testing equipment. Through a hands-on educational approach, the YES and YES2 low-cost space tether experiments have been launched into orbit. In September 2007, all 32 km of the YES2 tether are deployed in orbit. With the help of this tether, a student-built re-entry capsule is deorbited over Kazakhstan. This work reports this design and analysis effort, with the aim to raise confidence in the use of space tethers.

2004 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) (IEEE Cat. No.04CH37566), 2004

This paper presents an experimental system for assembly in space. A weightless and frictionless environment is approximated using an air-hockey table where robots and structural components can float on the surface. The robots use fan propulsion to dock with components and assemble them together to make 2D structures. This system is designed to implement three key technologies for space selfassembly: 1) intelligent components with universal connectors, 2) a set of self-reconfigurable robots that fetch and assemble components, and 3) a distributed method for controlling the robotic-assembly process. An overview of the system's design and experimental results is presented.

Tethers have been proposed for several space applications, like satellite de-orbiting or re-boost, electric energy generation, scientific research and so on. However, they may be vulnerable to orbital debris and meteoroid impacts. The problem was assessed, to assist tether systems design, by detailed numerical computations of the average impact rate of artificial debris, taking into account the specific geometric properties of tethers as debris targets, when compared to typical satellites. The results obtained confirm that, for single-strand tethers in low earth orbit, the probability to be severed by orbital debris and meteoroid impacts is quite significant, making necessary the adoption of innovative designs for long duration missions.

Journal of Spacecraft and Rockets, 2007

A mechanism for control of space tether deployment is presented and discussed in this paper. This friction device called the "barberpole" was derived from the textile industry. The mechanism was analyzed, developed and tested for the second Young Engineers' Satellite mission (YES2), which is intended to feature the first European tether deployment. YES2 further aims to use the tether to accurately deorbit a small innovative re-entry capsule. The barberpole is used for precisely guiding the dynamics of a capsule by controlling the deployment velocity of a tether which connects the capsule to an orbiting platform, in this case the Foton satellite. Design steps, derivation of a mathematical model, thermal analysis and experimental results of the device are presented in this paper. The exponential dependency of applied friction force versus number of tether wraps around the pole is theoretically and experimentally proved. Friction performance and predictability are discussed based on experiments performed both on ground using a custom-built test-rig and during parabolic flight campaigns. The work highlights the suitability of the barberpole design for space tether applications.