Final design of a space debris removal system

The objective is the removal of medium sized orbital debris in low Earth orbits. The design incorporates a transfer vehicle and a netting vehicle to capture the medium size debris. The system is based near an operational space station located at 28.5 degrees inclination and 400 km altitude. The system uses ground based tracking to determine the location of a satellite breakup or debris cloud. This data is unloaded to the transfer vehicle, and the transfer vehicle proceeds to rendezvous with the debris at a lower altitude parking orbit. Next, the netting vehicle is deployed, tracks the targeted debris, and captures it. After expending the available nets, the netting vehicle returns to the transfer vehicle for a new netting module and continues to capture more debris in the target area. Once all the netting modules are expended, the transfer vehicle returns to the space station's orbit, where it is resupplied with new netting modules from a space shuttle load. The new modules are launched by the shuttle from the ground, and the expended modules are taken back to Earth for removal of the captured debris, refueling, and repacking of the nets. Once the netting modules are refurbished, they are taken back into orbit for reuse. In a typical mission, the system has the ability to capture 50 pieces of orbital debris. One mission will take about six months. The system is designed to allow for a 30 degree inclination change on the outgoing and incoming trips of the transfer vehicle

Potential effects of optical solar sail degredation on trajectory design

The optical properties of the thin metalized polymer films that are projected for solar sails are assumed to be affected by the erosive effects of the space environment. Their degradation behavior in the real space environment, however, is to a considerable degree indefinite, because initial ground test results are controversial and relevant inspace tests have not been made so far. The standard optical solar sail models that are currently used for trajectory design do not take optical degradation into account, hence its potential effects on trajectory design have not been investigated so far. Nevertheless, optical degradation is important for high-fidelity solar sail mission design, because it decreases both the magnitude of the solar radiation pressure force acting on the sail and also the sail control authority. Therefore, we propose a simple parametric optical solar sail degradation model that describes the variation of the sail film's optical coefficients with time, depending on the sail film's environmental history, i.e., the radiation dose. The primary intention of our model is not to describe the exact behavior of specific film-coating combinations in the real space environment, but to provide a more general parametric framework for describing the general optical degradation behavior of solar sails. Using our model, the effects of different optical degradation behaviors on trajectory design are investigated for various exemplary missions

In-situ Magnesium Diboride Superconducting Thin Films grown by Pulsed Laser Deposition

Superconducting thin films of MgB2 were deposited by Pulsed Laser Deposition on magnesium oxide and sapphire substrates. Samples grown at 450C in an argon buffer pressure of about 10-2 mbar by using a magnesium enriched target resulted to be superconducting with a transition temperature of about 25 K. Film deposited from a MgB2 sintered pellet target in ultra high vacuum conditions showed poor metallic or weak semiconducting behavior and they became superconducting only after an ex-situ annealing in Mg vapor atmosphere. Up to now, no difference in the superconducting properties of the films obtained by these two procedures has been evidenced.Comment: 10 pages, 4 figure

Large SAR Membrane Antennas with Lightweight Deployable Booms

At the DLR Institute of Composite Structures and Adaptive Systems and the company Kayser-Threde extremely lightweight and stiff deployable carbon fibre-reinforced plastics (CFRP) booms and deployment mechanisms have been developed. The main target application is to develop an ultra-light weight solar sail for deep space satellite propulsion. Based on the successful development and ground-testing of a 20m x 20m deployable solar sail structure the in-orbit verification of the deployment principle and mechanisms is now being planned for launch in 2007. Kayser-Threde in collaboration with DLR has most recently completed a phase-B study of the solar sail project under ESA/ESTEC contract. In addition, mission and design studies have been performed at Kayser-Threde for ultra-light weight structures which can reach 100m x 100m in free space where a reflective, thin polyimide membrane is unfolded using DLR's advanced CFRP booms. Synthetic Aperture Radar (SAR) satellites require large and long antennas which in turn require a large satellite bus as well as a launcher with a large fairing. This is especially true for lower frequency SARs such as L-Band, where antenna sizes of typically 12m x 3m are required. The cost for such a SAR mission could be reduced significantly if the antenna and its deployment and support structure would be lightweight and could be folded during launch. The membrane antenna concept has been demonstrated in Canada by the CSA and EMS Technologies, and in the US by JPL. Receive only antennas are of interest for micro satellites which fly in a formation with a large active SAR satellite in order to perform SAR interferometry in a "Cartwheel" configuration. However, research has also been done for active phased array membrane antennas. The paper provides a first concept for a deployment and support structure for a L-Band SAR membrane antenna. Estimates for the mass and the achievable stiffness are provided

A Summary fo Solar Sail Technology Developments and Proposed Demonstration Missions

NASA's drive to reduce mission costs and accept the risk of incorporating innovative, high payoff technologies into it's missions while simultaneously undertaking ever more difficult missions has sparked a greatly renewed interest in solar sails. From virtually no technology or flight mission studies activity three years ago solar sails are now included in NOAA, NASA, DOD, DLR, ESA and ESTEC technology development programs and technology roadmaps. NASA programs include activities at Langley Research Center, Jet Propulsion Laboratory, Marshall Space Flight Center, Goddard Space Flight Center, and the NASA Institute for Advanced Concepts; NOAA has received funding for a proposed solar sail mission; DLR is designing and fabricating a 20-m laboratory model sail, there are four demonstration missions under study at industry, NASA, DOD and Europe, two new text books on solar sailing were recently published and one new test book is planned. This paper summarizes these on-going developments in solar sails

Mechanical Concepts on Large Membrane Array Antenna Architectures

Increasing interest from the scientific community to utilize space-borne L- or P-Band radar antennas for remote sensing techniques specifies very large antenna apertures in future. Typical applications are biomass monitoring, measurements of surface displacement due to seismic activity, volcanism, or glacier flow, or the sounding of the ice shields. A common European interest in large antenna developments can be derived from ESA’s Technology Harmonization Mapping activities. A growing trend of antenna sizes is expected for higher sensitivity instruments. Severe constraints on antenna size were identified and very large apertures at around 30m dimension were found to be required. To comply with future requirements of huge space antennas, typical items such as volume constraints of the launcher, system mass, system stiffness, development costs, shape accuracy during operation, and risks must be carefully assessed prior to concept selection. Foldable membrane array antennas are attractive candidates, but since thin gauge films do not provide any stiffness, deployable support structures are required to stretch the large membrane adequately. At DLR, in collaboration with space industries, very light deployment concepts for support structures in space are being developed. Originally intended to span huge membranes for propellant-less solar sails, the concepts are evaluated now to be applied to very large deployable array antennas. The main focus of the present trade-offs aim at strict mass reduction, but membrane flatness and alignment requirements are in consideration as well

A space-based system for NEO detection

A space-based detection system is proposed, to discover Inner Earth Objects and estimate their orbits and sizes. This system shall complement present future ground-based surveys and will enable the determination of the size of the population and its contribution to the impact hazard to the Earth

The Solar Sail Material (SSM) Project : Results of Activities

Solar Sail Materials (SSM