Browsing by Author "Palla, Chiara"

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    Development of commercial drag-augmentation systems for small satellites
    (ESA Space Debris Office, 2017-06-30) Palla, Chiara; Kingston, Jenny; Hobbs, Stephen
    In the framework of the ESA CleanSat programme Cranfield University is developing a family of drag augmentation system (DAS) modules to enable small satellites in Low Earth Orbit (LEO) to comply with space debris mitigation requirements. There are currently two mature Cranfield DAS designs based on deployable Kapton sails using stored energy for deployment. One concept is Icarus and it is currently on-board the UK’s TechDemoSat-1 (launched 8 July 2014) and Carbonite-1 spacecraft (launched 10 July 2015). The second concept is the de-orbit mechanism (DOM) module, which is due to fly as technological demonstrator on the upcoming ESA ESEO mission. The key drivers used during the design process were: low cost, low mass, easy testability, safety, reliability, and avoidance of additional debris production. These drivers matched with top-level requirements, from a potential customers perspective (e.g.: satellite integrators), which were defined during the CleanSat study. Other relevant requirements for the DAS included demisability, performance (in terms of orbital decay), area-to-mass ratio, functionality, lifetime, and environment compatibility. This paper discusses the compliance of the Cranfield DAS designs with the identified requirements, and illustrates the scalability via application to several case study missions (500 kg and 200 kg LEO satellites). The two most challenging aspects to assess were compliance with the lifetime required for storage on ground and pre-deployment on orbit, and the effect of the orbital environment (radiation, ATOX, debris) on the sail. The study has provided useful input to explore new concepts based on the heritage designs; these concepts are evolutions of the DOM unit and hybrid designs. The hybrid design combines aspects of the Icarus and the DOM concepts to reduce the limitations of the respective individual devices and improve scalability, adaptability and manufacturability. In addition, this work is helping to achieve commercial readiness for the technology. This will enable development of a commercial DAS offering that will be an attractive solution for small satellite integrators, allowing them to meet debris mitigation requirements.
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    Development of drag augmentation systems for de-orbiting small satellites
    (2017-06) Palla, Chiara; Kingston, Jenny
    The adoption of the ISO 24113 by ESA in 2014 has set an important milestone for the path towards an evolution and worldwide compliance of the Space Debris Mitigation (SDM) requirements. Small spacecraft classes have limited propulsion capabilities or even they are not provided with propulsion subsystem to achieve a controlled re-entry. This issue brings the need to develop affordable de-orbiting technologies with a limited reliance on the system level performance, ideally largely passive methods. The main aim of this research is to develop passive drag augmentation systems (DAS) for de-orbiting small spacecraft at the end of life, enabling them to comply with SDM requirements. After a feasibility study for the potential commercial use of DAS, the satellites’ need for passive de-orbiting technologies is investigated through market forecast and future scenarios of spacecraft compliance to the 25 years re-entry requirement. Spacecraft subsystems failures are analysed statistically to assess how they might impact the end of mission phase and to guide in the de-orbiting strategy selection. The applicability of current Cranfield DAS design is assessed by developing a simple model for preliminary drag area calculation, validating it with STELA and DRAMA, and calculating the additional area needed vs the area provided by DAS for a spacecraft sample. The requirements for DAS are analysed considering the customer’s needs with respect to the internal design drivers. A design parameters analysis is performed to evaluate the scalability of the DAS and their compatibility with satellite platforms. The parametric study together with the requirements analysis provide useful input to explore new concepts based on the heritage designs. In parallel, the De-Orbit Mechanism (DOM) technological demonstrator is developed from prototype model up to flight model, after undergoing qualification test campaign. The DOM will fly on board the upcoming ESA ESEO mission. This research will enable a commercial DAS products offering that will be an attractive solution for small satellite integrators, allowing them to meet debris mitigation requirements.
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    Failure analysis of satellite subsystems to define suitable de-orbit devices
    (Elsevier, 2016-07-14) Palla, Chiara; Peroni, Moreno; Kingston, Jennifer
    Space missions in Low Earth Orbit (LEO) are severely affected by the build-up of orbital debris. A key practice, to be compliant with IADC (Inter-Agency Space Debris Coordination Committee) mitigation guidelines, is the removal of space systems that interfere with the LEO region not later than 25 years after the End of Mission. It is important to note that the current guidelines are not generally legally binding, even if different Space Agencies are now looking at the compliance for their missions. If the guidelines will change in law, it will be mandatory to have a postmission disposal strategy for all satellites, including micro and smaller classes. A potential increased number of these satellites is confirmed by different projections, in particular in the commercial sector. Micro and smaller spacecraft are, in general, not provided with propulsion capabilities to achieve a controlled re-entry, so they need different de-orbit disposal methods. When considering the utility of different debris mitigation methods, it is useful to understand which spacecraft subsystems are most likely to fail and how this may affect the operation of a de-orbit system. This also helps the consideration of which components are the most relevant or should be redundant depending on the satellite mass class. This work is based on a sample of LEO and MEO satellites launched between January 2000 and December 2014 with mass lower than 1000 kg. Failure analysis of satellite subsystems is performed by means of the Kaplan–Meier survival analysis; the parametric fits are conducted with Weibull distributions. The study is carried out by using the satellite database SpaceTrak™ which provides anomalies, failures, and trends information for spacecraft subsystems and launch vehicles. The database identifies five states for each satellite subsystem: three degraded states, one fully operational state, and one failed state (complete failure). The results obtained can guide the identification of the activation procedure for a de-orbit strategy and the level of integration it should have with the host satellite in order to be activated before a total failure. At Cranfield Space Research Centre two different solutions have already been developed as de-orbit sail payloads for microsatellites (Icarus-1 on TechDemoSat-1 and Icarus-3 on Carbonite-1 currently on-orbit, DOM for future ESA ESEO mission). This study will provide a useful input to improve and refine the current de-orbit concepts for future satellite missions.
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    Forecast analysis on satellites that need de-orbit technologies: future scenarios for passive de-orbit devices
    (Springer Verlag, 2016-05-10) Palla, Chiara; Kingston, Jennifer
    Propulsion-based de-orbit is a space-proven technology; however, this strategy can strongly limit operational lifetime, as fuel mass is dedicated to the de-orbiting. In addition previous reliability studies have identified the propulsion subsystem as one of the major contributors driving satellite failures. This issue brings the need to develop affordable de-orbit technologies with a limited reliance on the system level performance of the host satellite, ideally largely passive methods. Passive disposal strategies which take advantage of aerodynamic drag as the de-orbit force are particularly attractive because they are independent of spacecraft propulsion capabilities. This paper investigates the future market for passive de-orbit devices in LEO to aid in defining top-level requirements for the design of such devices. This is performed by considering the compliances of projected future satellites with the Inter Agency Space Debris Coordination Committee de-orbit time, to quantify the number of spacecraft that are compliant or non-compliant with the guidelines and, in this way, determine their need for the previously discussed devices. The study is performed by using the SpaceTrak™ database which provides future launch schedules, and spacecraft information; the de-orbit analysis is carried out by means of simulations with STELA. A case study of a passive strategy is given by the de-orbit mechanism technological demonstrator, which is currently under development at Cranfield University and designed to deploy a drag sail at the end of the ESEO satellite mission.