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- Eriksson, Johan, Professor, 1967-, et al.
(författare)
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Outsourcing the American Space Dream? : SpaceX and the Race to the Stars
- 2022
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Konferensbidrag (refereegranskat)abstract
- Whereas the rise of private space entrepreneurship is indisputable, this paper contends that contrary to the “NewSpace” narrative, the development of privately owned and operated human spacefaring does not dispel or fundamentally alter the American space dream but rather implies continuity of the narrative of America as the dominant global space power, specifically regarding a return to the Moon and with the explicit aim of colonizing Mars. The present paper analyzes the continuity of the American space dream and how it is expressed by public and private space actors as well as being supported by popular culture, entertainment, and an active space enthusiast community. The paper maintains that the continuity of the American space dream as a unifying national narrative is facilitated by how private spacefaring is heavily dependent on the US government’s emphasis on the pivotal role of private space industry for US-led space exploration. This dependent relationship provides incentives for private space entrepreneurs to share and tap into the established American space dream. The continuity of the American space dream is achieved through a prevailing yet reconfigured government-industrial complex.
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- Lindgren, Per, et al.
(författare)
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Robust real-time applications in Timber
- 2006
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Ingår i: 2006 IEEE International Conference on Electro/information Technology. - Piscataway, NJ : IEEE Communications Society. - 0780395921 ; , s. 191-196
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Konferensbidrag (refereegranskat)abstract
- Embedded systems are often operating under hard real-time constraints, for example in automotive applications. For such systems, robustness and reliability are crucial, which calls for rigorous system design and methodologies for validation. In this paper we advocate a design methodology for robust, realtime systems, based on Timber; a pure reactive system model that allows for formal reasoning about various system properties. We outline how system specifications in Timber can be "compiled" into efficient standalone executables for general light-weight microcontroller platforms. Methods for resource analysis and implications to system dimensioning and validation are further discussed.
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| 7. |
- Lindgren, Per, et al.
(författare)
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TinyTimber, reactive objects in C for real-time embedded systems
- 2008
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Ingår i: Proceedings, Design, Automation and Test in Europe. - New York : ACM Digital Library. - 9783981080131 ; , s. 1382-1385
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Konferensbidrag (refereegranskat)abstract
- Embedded systems are often operating under hard real-time constraints. Such systems are naturally described as time-bound reactions to external events, a point of view made manifest in the high-level programming and systems modeling language Timber. In this paper we demonstrate how the Timber semantics for parallel reactive objects translates to embedded real-time programming in C. This is accomplished through the use of a minimalistic Timber Run-Time system, TinyTimber (TT). The TT kernel ensures state integrity, and performs scheduling of events based on given time-bounds in compliance with the Timber semantics. In this way, we avoid the volatile task of explicitly coding parallelism in terms of processes/threads/semaphores/monitors, and side-step the delicate task to encode time-bounds into priorities. In this paper, the TT kernel design is presented and performance metrics are presented for a number of representative embedded platforms, ranging from small 8-bit to more potent 32-bit micro controllers. The resulting system runs on bare metal, completely free of references to external code (even C-lib) which provides a solid basis for further analysis. In comparison to a traditional thread based real-time operating system for embedded applications (FreeRTOS), TT has tighter timing performance and considerably lower code complexity. In conclusion, TinyTimber is a viable alternative for implementing embedded real-time applications in C today.
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- Nguyen, Hugo, et al.
(författare)
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Micropropulsion systems research and manufacture in Sweden
- 2003
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Ingår i: Proceedings of the 4th Round Table on Micro/Nano Technology for Space, ESTEC, Noordwijk, The Netherlands. - : ESTEC/ESA. ; , s. 476-485
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Konferensbidrag (refereegranskat)abstract
- Micropropulsion for spacecraft is an enabling technology for many future missions, and may increase the performance and drastically reduce the mass required for advanced propulsion systems. The Swedish activities in micropropulsion at The Angstrom Space Technology Centre (ASTC) are outlined. The research targets two major issues: the development of system parts, and the research into integration techniques and strategies. This paper collects a multitude of devices relevant to the micropropulsion system design, together with representative functional demonstrations. The items are mainly intended for chemical micropropulsion systems or fuel-feed systems for electric propulsion. In particular, gas handling devices, sensors, and actuators are presented. These include silicon nozzles, thin film heaters, suspended microcoil heaters, proportional piezoelectric valves, proportional and isolation valves using phase-change material, thermal throttle flow-regulators, high-pressure regulators, 3D-particle filters, and sensors for strain, pressure, flow, and thrust. Moreover, integration techniques and interface structures are presented, for example low-temperature plasma-assisted silicon wafer bonding, multiwafer bonding, thin film soldering, hermetic electric through-wafer via connections, and multiconnector through-wafer vias. Emphasis is on how these items are designed to allow for system integration in a multiwafer silicon stack, comprising a complete micropropulsion system. In this manner, all items form a parts collection available to the system design. This strategy is exemplified by three micropropulsion systems researched at the ASTC. First, the cold/hot gas micropropulsion system is suitable for small spacecraft or when the demands on stability and pointing precision are extreme. The system performance depends strongly on the use of gas flow control. The complete gas handling system of four independent thrusters is integrated in the assembly of four structured silicon wafers. Each independent thruster contains a proportional valve, sensors for pressure, temperature, and thrust feedback, a converging-diverging micronozzle, and a suspended microcoil heater. The mass of the system is below 60 g. In total, this will provide the spacecraft with a safe, clean, low-powered, redundant, and flexible system for three-axis stabilization and attitude control. Second, a Xenon feed system for ion propulsion is heavily miniaturized using microsystems technology. Basically, a micromachined high-pressure regulator receives the gas from the storage, and the flow is further modulated by a thermally controlled flow restrictor. The flow restrictor microsystem comprises narrow ducts, thin film heaters, suspended parts for heat management, and flow sensors. Hereby, the amount of xenon required by the electric propulsion systems can be promptly delivered. The complete system mass is estimated to 150g. Third, within the EU IST program, the ASTC participates in the development of a micro-pyrotechnic actuator system (Micropyros), suitable for short-duration space propulsion. The Micropyros integrate a full matrix of minute solid combustion rocket engines into panels situated on the spacecraft hull. The thrusters can be individually ignited, and each deliver thrust in the millinewton range. The ASTC focuses on the integration of the propulsion part by low-temperature bonding, and the characterization of the complete system.
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