Escape Trajectories of Solar Sails and General Relativity

General relativity can have a significant impact on the long-range escape trajectories of solar sails deployed near the sun. Spacetime curvature in the vicinity of the sun can cause a solar sail traveling from 0.01 AU to 2550 AU to be deflected by as much as one million kilometers, and should therefore be taken into account at the beginning of the mission. There are a number of smaller general relativistic effects, such as frame dragging due to the slow rotation of the sun which can cause a deflection of more than one thousand kilometers.Comment: 6 pages, 3 figures. Proceedings of the Sixth IAA Symposium on Realistic Near-Term Advanced Scientific Space Missions. Missions to the Outer Solar System and Beyond, pp. 67-72, Aosta, Italy, 6-9 July, 200

Interplanetary CubeSats system for space weather evaluations and technology demonstration

The paper deals with the mission analysis and conceptual design of an interplanetary 6U CubeSats system to be implemented in the L1 Earth-Sun Lagrangian Point mission for solar observation and in-situ space weather measurements. Interplanetary CubeSats could be an interesting alternative to big missions, to fulfill both scientific and technological tasks in deep space, as proved by the growing interest in this kind of application in the scientific community and most of all at NASA. Such systems allow less costly missions, due to their reduced sizes and volumes, and consequently less demanding launches requirements. The CubeSats mission presented in this paper is aimed at supporting measurements of space weather. The mission envisages the deployment of a 6U CubeSats system in the L1 Earth-Sun Lagrangian Point, where solar observations for in situ measurements of space weather to provide additional warning time to Earth can be carried out. The proposed mission is also intended as a technology validation mission, giving the chance to test advanced technologies, such as telecommunications and solar sails, envisaged as propulsion system. Furthermore, traveling outside the Van Allen belts, the 6U CubeSats system gives the opportunity to further investigate the space radiation environment: radiation dosimeters and advanced materials are envisaged to be imple- mented, in order to test their response to the harsh space environment, even in view of future implementation on other spacecrafts (e.g. manned spacecrafts). The main issue related to CubeSats is how to fit big science within a small package - namely power, mass, volume, and data limitations. One of the objectives of the work is therefore to identify and size the required subsystems and equipment, needed to accomplish specific mission objectives, and to investigate the most suitable configuration, in order to be compatible with the typical CubeSats (multi units) standards

Solar sail science mission applications and advancement : solar sailing: concepts, technology, missions

Solar sailing has long been envisaged as an enabling or disruptive technology. The promise of open-ended missions allows consideration of radically new trajectories and the delivery of spacecraft to previously unreachable or unsustainable observation outposts. A mission catalogue is presented of an extensive range of potential solar sail applications, allowing identification of the key features of missions which are enabled, or significantly enhance, through solar sail propulsion. Through these considerations a solar sail application-pull technology development roadmap is established, using each mission as a technology stepping-stone to the next. Having identified and developed a solar sail application-pull technology development roadmap, this is incorporated into a new vision for solar sailing. The development of new technologies, especially for space applications, is high-risk. The advancement difficulty of low technology readiness level research is typically underestimated due to a lack of recognition of the advancement degree of difficulty scale. Recognising the currently low technology readiness level of traditional solar sailing concepts, along with their high advancement degree of difficulty and a lack of near-term applications a new vision for solar sailing is presented which increases the technology readiness level and reduces the advancement degree of difficulty of solar sailing. Just as the basic principles of solar sailing are not new, they have also been long proven and utilised in spacecraft as a low-risk, high-return limited-capability propulsion system. It is therefore proposed that this significant heritage be used to enable rapid, near-term solar sail future advancement through coupling currently mature solar sail, and other, technologies with current solar sail technology developments. As such the near-term technology readiness level of traditional solar sailing is increased, while simultaneously reducing the advancement degree of difficulty along the solar sail application-pull technology development roadmap

Microscopic Approach to Analyze Solar-Sail Space-Environment Effects

Near-sun space-environment effects on metallic thin films solar sails as well as hollow-body sails with inflation fill gas are considered. Analysis of interaction of the solar radiation with the solar sail materials is presented. This analysis evaluates worst-case solar radiation effects during solar-radiation-pressure acceleration. The dependence of the thickness of solar sail on temperature and on wavelength of the electromagnetic spectrum of solar radiation is investigated. Physical processes of the interaction of photons, electrons, protons and helium nuclei with sail material atoms and nuclei, and inflation fill gas molecules are analyzed. Calculations utilized conservative assumptions with the highest values for the available cross sections for interactions of solar photons, electrons and protons with atoms, nuclei and hydrogen molecules. It is shown that for high-energy photons, electrons and protons the beryllium sail is mostly transparent. Sail material will be partially ionized by solar UV and low-energy solar electrons. For a hollow-body photon sail effects including hydrogen diffusion through the solar sail walls, and electrostatic pressure is considered. Electrostatic pressure caused by the electrically charged sail's electric field may require mitigation since sail material tensile strength decreases with elevated temperature.Comment: 10 pages, 6 figures. Talk given on the 59 International Astronautical Congress, Glasgow, Scotland, 29 September - 2 October, 200

The Accumulation of Tissue Cholesterol and Its Relationship to Bile Acid and Sterol Turnover

Normal and hypophysectomized rats were divided into equal homogeneous groups to determine the effect of cholestyramine, corn oil and cholesterol on the excretion of fecal bile acids and sterols. Bile acid turnover rates, pool sizes, and spectrums were studied and compared

Scouting the spectrum for interstellar travellers

Advanced civilizations capable of interstellar travel, if they exist, are likely to have advanced propulsion methods. Spaceships moving at high speeds would leave a particular signature which could be detected from Earth. We propose a search based on the properties of light reflecting from objects travelling at relativistic speeds. Based on the same principles, we also propose a simple interstellar beacon with a solar sail

Technology requirements of exploration beyond Neptune by solar sail propulsion

This paper provides a set of requirements for the technology development of a solar sail propelled Interstellar Heliopause Probe mission. The mission is placed in the context of other outer solar systems missions, ranging from a Kuiper Belt mission through to an Oort cloud mission. Mission requirements are defined and a detailed parametric trajectory analysis and launch date scan performed. Through analysis of the complete mission trade space a set of critical technology development requirements are identified which include an advanced lightweight composite High-Gain Antenna, a high-efficiency Ka-band travelling-wave tube amplifier and a radioisotope thermoelectric generator with power density of approximately 12 W/kg. It is also shown that the Interstellar Heliopause Probe mission necessitates the use of a spinning sail, limiting the direct application of current hardware development activities. A Kuiper Belt mission is then considered as a pre-curser to the Interstellar Heliopause Probe, while it is also shown through study of an Oort cloud mission that the Interstellar Heliopause Probe mission is the likely end-goal of any future solar sail technology development program. As such, the technology requirements identified to enable the Interstellar Heliopause Probe must be enabled through all prior missions, with each mission acting as an enabling facilitator towards the next

Extension of Earth-Moon libration point orbits with solar sail propulsion

This paper presents families of libration point orbits in the Earth-Moon system that originate from complementing the classical circular restricted three-body problem with a solar sail. Through the use of a differential correction scheme in combination with a continuation on the solar sail induced acceleration, families of Lyapunov, halo, vertical Lyapunov, Earth-centred, and distant retrograde orbits are created. As the solar sail circular restricted three-body problem is non-autonomous, a constraint defined within the differential correction scheme ensures that all orbits are periodic with the Sun’s motion around the Earth-Moon system. The continuation method then starts from a classical libration point orbit with a suitable period and increases the solar sail acceleration magnitude to obtain families of orbits that are parametrised by this acceleration. Furthermore, different solar sail steering laws are considered (both in-plane and out-of-plane, and either fixed in the synodic frame or fixed with respect to the direction of sunlight), adding to the wealth of families of solar sail enabled libration point orbits presented. Finally, the linear stability properties of the generated orbits are investigated to assess the need for active orbital control. It is shown that the solar sail induced acceleration can have a positive effect on the stability of some orbit families, especially those at the L2 point, but that it most often (further) destabilises the orbit. Active control will therefore be needed to ensure long-term survivability of these orbits