45 research outputs found
DESIGN AND COST ANALYSIS OF HIGH-POWER SOLAR ELECTRIC PROPULSION PLATFORMS
No full textNowadays, space agencies are trying to select cost-effective solutions, to minimize space missions cost without affecting the performance. It means that cost analysis needs to cope with mission and feasibility analysis since the early design phases. The paper focuses on the preliminary design of high-power SEP platforms for space exploration and transportation, highlighting how the cost can represent one of the critical parameters to evaluate the feasibility and effectiveness of the solutions proposed. Particular attention is dedicated to the effects of specific design choices, mainly for the SEP subsystem, on the platforms design and cost. Main results are presented and discussed, and main conclusions are drawn
Missions, Architectures and Technologies for a Lunar Space Tug in Support of Cislunar Infrastructures
No full textCuriosity and discovery are vital elements for the future of human space exploration. Starting from past and present experiences in human and robotic exploration, the global community is working on preparing humans to push themselves beyond known boundaries, i.e. the Low Earth Orbit environment, to reach, explore and, eventually, colonize the Mars surface. This goal requires capability evolution and technology investments. The pathway to Mars includes multiple destinations. The Moon and its vicinity seem to represent the most promising intermediate step to fill the technology gap. The Lunar Space Tug represents one of the possible key elements to sustain the growth and the operability of the future Space Station orbiting in Cislunar space, thanks to its reusability and the adoption of electric propulsion. It can transfer unmanned modules from Low Earth Orbit up to the Cislunar Space Station and back, to provide the required replenishment. Among all Lunar Space Tug mission phases, autonomous rendezvous and mating maneuvers represent one of the most critical one from the point of view of the technology involved in the Lunar Space Tug design. The strong environmental impact must be considered to define the optimal rendezvous approach, especially when the maneuver must be performed in different environments as in this case, i.e. Near Earth Orbit and Cislunar. For the rendezvous maneuver, it is crucial to estimate environmental disturbances that can jeopardize the system as well as the maneuver success. To be compliant with the strict safety requirements that characterize this maneuver, a robust control can guarantee the constraints satisfaction, even when persistent disturbances are acting on the system. In this paper, a Linear-Quadratic Model Predictive Control has been adopted to control the Lunar Space Tug during the last phase of the rendezvous maneuver, showing the robustness behavior of this approach in the presence of reduced persistent disturbances and the compliance of the controller with the real-time application. Once the Lunar Space Tug design is defined through a multi-purpose systems engineering tool, the 6 degrees-of- freedom Lunar Space Tug simulator is used to analyze in deep the rendezvous maneuver. The optimal maneuver design is obtained according to the Attitude and Orbit Control Subsystem architecture and the Thrust Management Function adopted for the determination of the proper control actuators selection and command duration, to realize the control action required. Main results on the Lunar Space Tug design and related performance during proximity operations in both Near Earth Orbit and Cislunar environments are discussed and main conclusions are drawn
A Comprehensive Modeling Framework for Integrated Mission Analysis and Design of a Reusable Electric Space Tug
No full text"Earth is a small town with many neighborhoods in a very big universe." The quote of the American Astronaut Ronald John Garan Jr. perfectly summarizes the universal and enduring mankind's interest in exploring the unknown, discovering new worlds, pushing the boundaries of scientific and technical limits further and beyond. More than a half century ago, during a speech delivered at Rice University in Houston, President John F. Kennedy claimed the Moon as the new frontier for the human space exploration. The outstanding achievements of the Apollo mission pushed the research in space across the second part of the last century with new goals, as the permanent presence of the human in space. The evolutionary space program built up around that promise was, to say the least, challenging and involved the development of several revolutionary elements. Due to the significant economic effort required by the Apollo mission, only two elements were realized: the Space Shuttle on one side and the Skylab space station on the other. While the Shuttle remained operative until 2011, Skylab was short-lived and disposed after about six years. Only by joining forces with other international partners, NASA was able to realize a long lasting permanent outpost orbiting around Earth, i.e. the International Space Station (ISS). But again, due to the considerable efforts dedicated to build up the ISS and to keep the Space Shuttle operative, the space race suffered a second setback. Until 2007, when the international community drew up a new visionary program. Moon exploration stepped again into the spotlight to extend and sustain human activities beyond Low Earth Orbit (LEO) towards Mars. The new era of space exploration has begun with the intent of expanding the frontiers of knowledge, capability, and opportunities in space. One of the first milestones is represented by the settlement of the so-called Lunar Orbital Platform-Gateway (LOP-G) by the mid 2020's. The Gateway will serve as a manned outpost in the lunar vicinity to support activities on and around the Moon while also servicing as technological and operational testbed to open the frontier for human exploration of Mars, thanks to the exploitation of key technologies, such as high-power electric propulsion. To sustain the LOP-G and its future visiting crews, the Orion spacecraft is currently under development. However, the usability of the Gateway could be extended if new transportation systems would be available to support the station transferring additional supplies and equipment. In compliance with the current plans to efficiently reduce the number of development and validation economic efforts by designing and exploiting same elements for multiple missions, a reusable, high-power electric space tug, i.e. the Lunar Space Tug (LST), is proposed in this Thesis to support the replenishment of the LOP-G. This innovative transportation system should be flexible enough to be adopted in different phases of the Gateway lifetime and for evolving needs. The LST should be in charge of recovering cargo modules released in Earth proximity and transfer them up to the Gateway performing a low-thrust transfer, before return to its operational orbit, ready for the next delivery mission, envisioning a closed-loop mission profile. A tailored multi-input/multi-output design tool has been developed to obtain the preliminary and detailed design, at component level, of the LST spacecraft for several propulsion subsystem architectures. The impact of adopting this technology on the platform design is investigated with respect to several thruster working points and case studies, each one characterized by different refurbishment needs. Then, the optimal LST configuration able to support the Gateway crew for different resupply needs is selected, performing a trade-off analysis among the design solutions that comply with all mission and system constraints previously defined in order to minimize the spacecraft mass, propellant consumption and overall mission cost. From an operational viewpoint, the LST should significantly rely on the Automated Rendezvous and Docking (ARVD) technology, which has been identified as crucial for the transition of space missions from geocentric architectures to self-sustainable, autonomy and independent. At this end, new Guidance Navigation and Control (GNC) algorithms shall be investigated to allow ARVD maneuvers to become reliable routine. In particular, the control problem encapsulates safety restrictions and performance specification that shall be properly addressed verifying the effectiveness and real-time implementability of innovative control strategies. Thus, a 6 Degrees-of-Freedom (DoF) orbital simulator has been developed to simulate the rotational and translational dynamics of the LST and its target vehicles in both Earth orbit and Lunar proximity. Moreover, to reproduce a realistic simulation environment, uncertainty and disturbance affecting the spacecraft dynamics during the maneuver have been modeled and included in the simulator. For attitude and orbital control, three different Model Predictive Control (MPC) algorithms have been implemented and their performance evaluated in the presence of disturbance and parametric uncertainty. In particular, a sampling-based stochastic MPC algorithm is proposed and the typical binding computational effort required by these type of stochastic algorithms, especially when running on low-performing hardware, has been overcome shifting the intensive computations to the offline phase, thus greatly reducing the online computational cost. To complete the algorithms verification process, all three MPC strategies have been experimentally validated exploiting spacecraft mock-up and running the algorithms on the on-board micro-controller, demonstrating their effectiveness and real-time computational applicability
How the Lunar Space Tug can support the cislunar station
No full textThe Lunar Space Tug is a sustainable transportation system able to rendezvous with a target body
in Low Earth Orbits environment, assess its current position, attitude and operational status, capture
the target and move it to the Cislunar space where the Lunar Orbital Platform-Gateway will be
settled. Thanks to the adoption of an electric Propulsion Subsystem based of Hall Effect Thruster
clusters, the Lunar Space Tug can save fuel to the detriment of much longer transfer time to deliver
the unmanned cargo to the cislunar Gateway. Since the Lunar Space Tug has been conceived to be
reusable, one of the main issue is related to the on-orbit refueling to sustain the Lunar Space Tug
during its operational lifetime. Each mission scenario shall take into account the effects related to
refueling operations according to mission requirements and constraints. Considering the whole
mission scenario in which the Lunar Space Tug will operate, this paper focuses on mission analysis
and conceptual system design, including typical systems budgets, like transfer duration, ∆v , mass
and power. Moreover, according to the transfer duration and the needs of the Lunar Orbital
Platform-Gateway, a preliminary trade-off analysis has been accomplished to investigate the
possibility of using a fleet of Lunar Space Tug instead of a single tug, taking onto account safety,
reliability, costs and operations issues. The identified optimal configuration is then compared with
the current reference option, i.e. the NASA Space Launch System adopted as cislunar delivery
vehicle
The Lunar Space Tug in the Future Space Exploration Scenario
No full textThe Lunar Space Tug (LST) is a sustainable transportation system able to rendezvous with a target body in the Low Earth Orbits (LEO) environment, assess its current position, attitude and operational status, capture the target and move it to the Cislunar space where a new Deep Space Habitat will be settled. Thanks to the adoption of an Electric Propulsion Subsystem based of Hall Effect Thruster (HET) clusters, the LST can save fuel to the detriment of much longer transfer time to deliver the unmanned cargo to the DSH. The LST is designed to accomplish several applications, from cargo transfer, to on-orbit assembly and samples return. Being a reusable transportation system, one of the main issue is related to the on-orbit refueling to sustain the LST during its operational lifetime. Each mission scenario must consider the effects related to refueling operations according to mission requirements and constraints. From a system point of view, considering the whole mission scenario in which the LST will operate, this paper focuses on the interface requirements with respect to the other mission elements involved, e.g. Launch Vehicles, DSH, Re-entry Vehicle. On the other hand, the most critical Subsystems (S/Ss) have been analyzed into the details, focusing on those affected by the adoption of the Electric Propulsion, i.e. the Electrical Power S/S (EPS), the Thermal Control S/S (TCS), and the Attitude and Orbital Control S/S (AOCS). In this work, different mission scenarios and system configurations have been considered and analyzed and the main results have been compared through a multi-level trade-off analysis, in order to define the best mission strategy and system design with respect to the stakeholders’ expectations, requirements and constraints. Main results are presented and discussed, and main conclusions are drawn
Electric Propulsion, an Enabling Technology for the Deep Space Gateway
No full textThe new era of space exploration has begun with the intent of expanding the frontiers of
knowledge, capability, and opportunities in space, to bring humans back to the Moon before
sending them to Mars. One of the first milestones is represented by the settlement of the Deep
Space Gateway by the mid 2020’s in the lunar proximity, thanks to the exploitation of key
technologies such as high-power Solar Electric Propulsion, which will be the propulsive core
of the Gateway. In compliance with the current plans of efficiently reduce the number of development
and validation efforts, designing and exploiting same elements for multiple missions,
this paper proposes an innovative high-power electric space tug to support the replenishment
of the Station, which should be flexible enough to be adopted in different phases of the Gateway
lifetime. Exploiting a tailored MATLAB design tool, the main mission, mass and power
budgets are provided for several spacecraft configurations and electric propulsion subsystem
architectures. Moreover, the impact of adopting this cornerstone technology on the platform
design is investigated with respect to different thruster working points. Then, the optimal LST
configuration able to support the Gateway crew for different resupply needs is selected and its
design is presented in detail
HOW THE LUNAR SPACE TUG CAN SUPPORT THE CISLUNAR STATION
No full textThe Lunar Space Tug is a sustainable transportation system able to rendezvous with a target body in the Low Earth Orbits (LEO) environment, assess its current position, attitude and operational status, capture the target and move it to the Cislunar space where a new Deep Space Habitat (DSH) will be settled. Thanks to the adoption of an Electric Propulsion Subsystem based of Hall Effect Thruster (HET) clusters, the LST can save fuel to the detriment of much longer transfer time to deliver the unmanned cargo to the DSH. The LST is designed to accomplish several applications, from cargo transfer, to on-orbit assembly and samples return. Being a reusable transportation system, one of the main issue is related to the on-orbit refueling to sustain the LST during its operational lifetime. Each mission scenario shall take into account the effects related to refueling operations according to mission requirements and constraints. Considering the whole mission scenario in which the LST will operate, this paper focuses on mission analysis and conceptual system design, including typical systems budgets, like delta-V, mass and power budgets. In addition, according to the transfer duration and the needs of the Cislunar station, a preliminary trade-off analysis has been accomplished to investigate the possibility of using a fleet of LST instead of one single LST, taking onto account safety, reliability, costs and operations issues. Main results are presented and discussed, and main conclusions are drawn
Electric propulsion for high-power deep space transportation system: investigation on mutual influences and preliminary sizing
No full textHow to Sustain the Deep Space Gateway with Reusable High-Power Electric Platforms
No full textThe future Lunar Orbital Platform-Gateway (LOP-G) will become a key on-orbit infrastructure
for the future human space exploration scenarios. This paper aims at designing and
sizing reusable transportation systems aimed at supporting the activities of the future station,
making benefit of the latest high-power electric propulsion technologies, currently under development.
Starting from an in-depth investigation of latest technological advancements of the
20kW-class Hall Effect thrusters, two mission scenarios supporting the LOP-G with resources
coming both from Earth and from the Moon are investigated. The results of the design and
sizing of the two reusable platforms and related electric propulsion subsystems is reported and
the results compared to envisage a common competitive architecture able to satisfy multiple
activities in support to the LOP-G
A sustainable bridge between Low Earth Orbits and Cislunar Infrastructures: the Lunar Space Tug
No full textThe International Space Station (ISS) is the first space human outpost and over the last 15 years, it has represented a peculiar environment where science, technology and human innovation converge together in a unique microgravity and space research laboratory. With the ISS entering the second part of its life and its operations running steadily at nominal pace, the global space community is starting planning how the human exploration could move further, beyond Low-Earth-Orbit (LEO). According to the Global Exploration Roadmap, the Moon represents the next feasible pathway for advances in human exploration towards the final goal, Mars. Based on the experience of the ISS, one of the most widespread ideas is to develop a Cislunar Station in preparation of long duration missions in a deep space environment. Cislunar space is defined as the area of deep space under the influence of Earth-Moon system, including a set of special orbits, e.g. Earth-Moon Libration points (EML) and Lunar Retrograde Orbit (LRO). This habitat represents a suitable environment for demonstrating and testing technologies and capabilities in deep space. In order to achieve this goal, there are several crucial systems and technologies, in particular related to transportation and launch systems. The Orion Multi-Purpose Crew Vehicle (MPCV) is a reusable transportation capsule designed to provide crew transportation in deep space missions, whereas NASA is developing the Space Launch System (SLS), the most powerful rocket ever built, which could provide the necessary heavy-lift launch capability to support the same kind of missions. These innovations would allow quite-fast transfers from Earth to the Cislunar Station and vice versa, both for manned and unmanned missions. However, taking into account the whole Concept of Operations for both the growth and sustainability of the Cislunar Space Station, the Lunar Space Tug (LST) can be considered as an additional, new and fundamental element for the mission architecture. The Lunar Space Tug represents an alternative to the SLS scenario, especially for what concerns all unmanned or logistic missions (e.g. cargo transfer, on orbit assembly, samples return), from LEO to Cislunar space. The paper focuses on the mission analysis and conceptual design of the Lunar Space Tug to support the growth and sustainment of the Cislunar Station. Particular attention is dedicated to interface requirements between the Space Tug and the modules of the Station, whose design can be deeply affected by the Space Tug. Main results are presented and discussed, and main conclusions are draw
