Alessandro Atzei

Solar polar orbiter: a solar sail technology reference study

An assessment is presented of a Solar Polar Orbiter mission as a Technology Reference Study. The goal is to focus the development of strategically important technologies of potential relevance to future science missions. The technology is solar sailing, and so the use of solar sail propulsion is, thus, defined a priori. The primary mission architecture utilizes maximum Soyuz Fregat 2-1b launch energy, deploying the sail shortly after Fregat separation. The 153 × 153 m square sail then spirals into a circular 0.48-astronomical-unit orbit, where the orbit inclination is raised to 90 deg with respect to the solar equator in just over 5 years. Both the solar sail and spacecraft technology requirements have been addressed. The sail requires advanced boom and new thin-film technology. The spacecraft requirements were found to be minimal because the spacecraft environment is relatively benign in comparison with other currently envisaged missions, such as the Solar Orbiter mission and BepiColombo.

GeoSail: An Elegant Solar Sail Demonstration Mission

In this paper a solar sail magnetotail mission concept was examined. The 43-m square solar sail is used to providethe required propulsion for continuous sun-synchronous apse-line precession. The main driver in this mission was found to be the reduction of launch mass and mission cost while enabling a nominal duration of 2 years within the framework of a demonstration mission. It was found that the mission concept provided an excellent solar sail technology demonstration option. The baseline science objectives and engineering goals were addressed, and mission analysis for solar sail, electric, and chemical propulsion performed. Detailed subsystems were defined for each propulsion system and it was found that the optimum propulsion system is solar sailing. A detailed tradeoff as to the effect of spacecraft and sail technology levels, and requirements, on sail size is presented for the first time. The effect of, for example, data acquisition rate and RF output power on sail size is presented, in which it is found that neither have a significant effect. The key sail technology requirements have been identified through a parametric analysis.

Sample return from mercury and other terrestrial planets using solar sail propulsion

A conventional Mercury sample return mission requires significant launch mass due to the large AV required for the outbound and return trips and the large mass of a planetary lander and ascent vehicle. It is shown that solar sail spacecraft can be used to reduce lander mass allocation by delivering the lander to a low, thermally safe orbit close to the planetary terminator. In addition, the ascending node of the solar sail spacecraft parking orbit plane can be artificially forced to avoid out-of-plane maneuvers during ascent from the planetary surface. Propellant mass is not an issue for spacecraft with solar sails, and so a sample can be returned relatively easily without resorting to lengthy, multiple gravity assists. A 275-m2 solar sail with a sail assembly loading of 5.9 g/m2 is used to deliver a lander, cruise stage, and science payload to a forced sun-synchronous orbit at Mercury in 2.85 years. The lander acquires samples and conducts limited surface exploration. An ascent vehicle delivers a small cold-gas rendezvous vehicle containing the samples for transfer to the solar sail spacecraft. The solar sail spacecraft then spirals back to Earth in 1 year. The total mission launch mass is 2353 kg, launched using a Japanese H2 class launch vehicle, C3 = 0. Extensive launch date scans have revealed an optimal launch date in April 2014 with sample return to Earth 4.4 years later. Solar sailing reduces launch mass by 60% and trip time by 40%, relative to conventional mission concepts. In comparison, mission analysis has demonstrated that solar-sail-powered Mars and Venus sample returns appear to have only modest benefits in terms of reduced launch mass, at the expense of longer mission durations, than do conventional propulsion systems.

Innovations for competitiveness: European views on “better-faster-cheaper”

Abstract The paper elaborates on “ lessons learned” from two recent ESA workshops, one focussing on the role of Innovation in the competitiveness of the space sector and the second on technology and engineering aspects conducive to better, faster and cheaper space programmes. The paper focuses primarily on four major aspects, namely: 1. a) the adaptations of industrial and public organisations to the global market needs; 2. b) the understanding of the bottleneck factors limiting competitiveness; 3. c) the trends toward new system architectures and new engineering and production methods; 4. d) the understanding of the role of new technology in the future applications. Under the pressure of market forces and the influence of many global and regional players, applications of space systems and technology are becoming more and more competitive. It is well recognised that without major effort for innovation in industrial practices, organisations, R&D, marketing and financial approaches the European space sector will stagnate and loose its competence as well as its competitiveness. It is also recognised that a programme run according to the “better, faster, cheaper” philosophy relies on much closer integration of system design, development and verification, and draws heavily on a robust and comprehensive programme of technology development, which must run in parallel and off-line with respect to flight programmes. A companys innovation capabilities will determine its future competitive advantage (in time, cost, performance or value) and overall growth potential. Innovation must be a process that can be counted on to provide repetitive, sustainable, long-term performance improvements. As such, it needs not depend on great breakthroughs in technology and concepts (which are accidental and rare). Rather, it could be based on bold evolution through the establishment of know-how, application of best practices, process effectiveness and high standards, performance measurement, and attention to customers and professional marketing. Having a technological lead allows industry to gain a competitive advantage in performance, cost and opportunities. Instrumental to better competitiveness is an R&D effort based on the adaptation of high technology products, capable of capturing new users, increasing production, decreasing the cost and delivery time and integrating high level of intelligence, information and autonomy. New systems will have to take in to account from the start what types of technologies are being developed or are already available in other areas outside space, and design their system accordingly. The future challenge for “faster, better, cheaper” appears to concern primarily “cost-effective”, performant autonomous spacecraft, “cost-effective”, reliable launching means and intelligent data fusion technologies and robust software serving mass- market real time services, distributed via EHF bands and Internet. In conclusion, it can be noticed that in the past few years new approaches have considerably enlarged the ways in which space missions can be implemented. They are supported by true innovations in mission concepts, system architecture, development and technologies, in particular for the development of initiatives based on multi-mission mini-satellites platforms for communication and Earth observation missions. There are also definite limits to cost cutting (such as lowering heads counts and increasing efficiency), and therefore the strategic perspective must be shifted from the present emphasis on cost-driven enhancement to revenue-driven improvements for growth. And since the product life-cycle is continuously shortening, competitiveness is linked very strongly with the capability to generate new technology products which enhance cost/benefit performance.

Electric propulsion in Europe

Abstract This paper presents the major activities carried out in Europe in the field of Electric Propulsion. Four lines of development are presently pursued. Two different models from the RIT family of radio-frequency ion thrusters are being developed in Germany. The RIT-10 thruster, operating in the thrust range of 10 mN, is due to be flight tested on board of the European Retrievable Carrier EURECA in 1988. A scaled-up version of this thruster, the RIT-35, is under development and it is mainly intended as the basic element of an Electric Propulsion Module for future interplanetary missions. Field Emission Electric Propulsion (FEEP) and Magneto-Plasma Dynamic (MPD) thrusters are also undergoing extensive research and testing. The paper describes the research, development and qualification programmes associated with the electric propulsion systems mentioned above and the work done by European industries and Universities. Finally an account is given of future interplanetary missions for which the use of primary electric propulsion is envisaged.