Operationally Responsive Space Research Articles

A Hybrid TDMA/CSMA-Based Wireless Sensor and Data Transmission Network for ORS Intra-Microsatellite Applications.

To achieve launch-on-demand for Operationally Responsive Space (ORS) missions, in this article, an intra-satellite wireless network (ISWN) is presented. It provides a wireless and modularized scheme for intra-spacecraft sensing and data buses. By removing the wired data bus, the commercial off-the-shelf (COTS) based wireless modular architecture will reduce both the volume and weight of the satellite platform, thus achieving rapid design and cost savings in development and launching. Based on the on-orbit data demand analysis, a hybrid time division multiple access/carrier sense multiple access (TDMA/CSMA) protocol is proposed. It includes an improved clear channel assessment (CCA) mechanism and a traffic adaptive slot allocation method. To analyze the access process, a Markov model is constructed. Then a detailed calculation is given in which the unsaturated cases are considered. Through simulations, the proposed protocol is proved to commendably satisfy the demands and performs better than existing schemes. It helps to build a full-wireless satellite instead of the current wired ones, and will contribute to provide dynamic space capabilities for ORS missions.

Fast Recovery Routing Algorithm for Software Defined Network based Operationally Responsive Space Satellite Networks

An emerging satellite technology, Operationally Responsive Space (ORS) is expected to provide a fast and flexible solution for emergency response, such as target tracking, dense earth observation, communicate relaying and so on. To realize large distance transmission, we propose the use of available relay satellites as relay nodes. Accordingly, we apply software defined network (SDN) technology to ORS networks. We additionally propose a satellite network architecture refered to as the SDN-based ORS-Satellite (Sat) networking scheme (SDOS). To overcome the issures of node failures and dynamic topology changes of satellite networks, we combine centralized and distributed routing mechanisms and propose a fast recovery routing algorithm (FRA) for SDOS. In this routing method, we use centralized routing as the base mode.The distributed opportunistic routing starts when node failures or congestion occur. The performance of the proposed routing method was validated through extensive computer simulations.The results demonstrate that the method is effective in terms of resoving low end-to-end delay, jitter and packet drops.

Recent progress on development trend and key technologies of vertical take-off vertical landing reusable launch vehicle

As the Reusable Launch Vehicle can reduce the launching cost, and improve the ability of Operationally Responsive Space (ORS), many aerospace powers in the world consider the Reusable Launch Vehicle as a main development tendency of space transportation system. Recently, Space Exploration Technologies Corporation (SpaceX), as the spokesman of private aerospace corporations, has attracted all the world’s attention to the Reusable Launch Vehicle. SpaceX has been developing technologies for rockets’ fully and rapid reusability, and several recovery tests have been conducted on technology-demonstrators and post-mission controlled-descent tests on Falcon 9 rockets’ first stages, both touchdown on the ocean platform and the land. On 22 December 2015, a Falcon 9 FT rocket of SpaceX, carrying 11 Orbcomm communications satellites, lifted off from Cape Canaveral. After cutoff and stage-separation, the Falcon 9s first stage flight back into the atmosphere and pulled off a powered landing on on Landing Zone 1, which is about 10 km far away from the Launch Site of SLC-40, settling to a smooth tail-first touchdown, making it a significant space “first”. After already celebrated a successful booster landing, SpaceX had decided to attempt a landing at sea on this flight despite available margins for a return to land. This decision was prompted by the need to master the landing sequence for sea-based recoveries which will be needed for about half of Falcon 9’s flights when lifting heavy satellites to high-energy orbits. On 8 April 2016, SpaceX’s Falcon 9 FT rocket, carrying CRS-8 Dragon cargo, lifted off from Cape Canaveral. The Falcon 9’s first stage has accomplished the first ever successful returning rocket on the Autonomous Spaceport Drone Ship (ASDS). This is considered a landmark accomplishment on the road to economical interplanetary and asteroid-to- planet space travel because it enables expensive launch vehicles to be reused. In this paper, based on the experiments of Falcon 9, and analyzing the main projects of the Reusable Launch Vehicle abroad in the past 60 years, the critical technologies will be researched and the results will provide references for the research of new type of space transportation systems.

Operational Methodology for Large-Scale Deployment of Nanosatellites into Low Earth Orbit

The on-orbit deployment of large numbers of nanosatellites is cast in terms of the relative motion equations, augmented with differential drag. Using this framework, a methodology is developed for minimizing the likelihood of recontact or interference among the deployed nanosatellites. This approach is applied to a representative test case derived from the Operationally Responsive Space Office’s Launch Enabler Mission, which delivered 28 small payloads to orbit in 2013. By strategically varying the deployment order, timing, and launch vehicle attitude, the net separation among each of the nanosatellites is demonstrated for the first three weeks with minimal close approaches. These results are validated using high-fidelity simulations.

Circular revisit orbits design for responsive mission over a single target

The responsive orbits play a key role in addressing the mission of Operationally Responsive Space (ORS) because of their capabilities. These capabilities are usually focused on supporting specific targets as opposed to providing global coverage. One subtype of responsive orbits is repeat coverage orbit which is nearly circular in most remote sensing applications. This paper deals with a special kind of repeating ground track orbit, referred to as circular revisit orbit. Different from traditional repeat coverage orbits, a satellite on circular revisit orbit can visit a target site at both the ascending and descending stages in one revisit cycle. This typology of trajectory allows a halving of the traditional revisit time and does a favor to get useful information for responsive applications. However the previous reported numerical methods in some references often cost lots of computation or fail to obtain such orbits. To overcome this difficulty, an analytical method to determine the existence conditions of the solutions to revisit orbits is presented in this paper. To this end, the mathematical model of circular revisit orbit is established under the central gravity model and the J2 perturbation. A constraint function of the circular revisit orbit is introduced, and the monotonicity of that function has been studied. The existent conditions and the number of such orbits are naturally worked out. Taking the launch cost into consideration, optimal design model of circular revisit orbit is established to achieve a best orbit which visits a target twice a day in the morning and in the afternoon respectively for several days. The result shows that it is effective to apply circular revisit orbits in responsive application such as reconnoiter of natural disaster.

Structure Design and Analysis for the Spacecraft On-Orbit Replacement Unit (ORU)

By using on-orbit replacement and assembly technology, some fresh ideas and methods for the design, produce and application of spacecraft were put forward. Universal structure is one of the most basic requirements of On-Orbit replacement, assembly. Module structure must obey the rules of the Operationally Responsive Space (ORS). According to the degree of spacecraft module division, two module structures were proposed, and the complex structure was analyzed to verify the correctness of it.

Research on spacecraft design for ORS based on the systems theory

The unpredictability and uncertainty of Operationally Responsive Space (ORS) missions have brought new challenges to traditional spacecraft design methods, in which the satellite and the launch vehicle are designed independently. In this article, a novel integrated design method for ORS spacecraft design has been proposed by analyzing the characteristics of the ORS missions according to the system theory. Firstly, the feasibility of the integrated design method is analyzed. Then, qualitative analyses of integrated design method for the subsystems of the traditional satellite and the launch vehicle are carried out. Finally, the advantages of the integrated design method are demonstrated through quantitative research, especially for the uncertain space missions. Simulation results show that the integrated design method is an effective technology to realize unpredictable ORS missions.

Responsive Satellites Through Ground Track Manipulation Using Existing Technology

Traditional space operations are characterized by large, highly-technical, long-standing satellite systems that cost billions of dollars and take decades to develop. Many branches of the US government have recognized the problem of sustaining current space operations and have responded by heavily supporting research and development in a field known as Operationally Responsive Space (ORS). This ORS research focuses on hardware, interfaces, rapid launch and deployment with the overall goal of reducing per-mission-cost down to $20 million. However, there are few studies on the feasibility of maneuvering satellites in lowEarth orbit (LEO) from a ground-track perspective once an asset is launched. We can achieve operational responsiveness by changing the ground track of a given satellite and thereby a geographical target location by applying existing thruster technology. Therefore it is not so much a new technology but a change in the Concept of Operations (CONOPS) of today’s space systems application. The existing paradigm on maneuvering is that it is costprohibitive, especially in performing orbital plane changes, thus orbit-changing maneuvers are only done at the beginning-of-life to establish the service orbit, end-of-life for disposal, and when absolutely necessary for the safety of the system (collision avoidance). This paradigm along with traditional space programs have to change and a transition to responsive and maneuverable systems must take place to meet the needs of space users in a timely manner. The analysis we present here shows that a satellite equipped with a standard chemical propulsion thruster in a 60-degree inclined, 500-km altitude orbit can move the ground over-flight target anywhere on the globe (within 60 degrees north and south latitudes) in as little as ten hours from the time of the maneuver with a fuel expenditure, measured in change in velocity (ΔV), of 100 meters-per-second. Similarly, a more efficient electric propulsion thruster can provide the same maneuverability in 27 hours from the start of the maneuver while expending the same amount of ΔV. This research demonstrates that existing technology can maneuver a satellite significantly to change its ground track to overfly a desired target on Earth in a relatively short period of time and well-within standard fuel budgets.

Efficient Covariance Intersection of Attitude Estimates Using a Local-Error Representation

As the complexity of spacecraft and space systems increases, there is an ever increasing need for more accurate and robust estimators to track the system. While the demand placed on an individual spacecraft is increasing, the spacecraft itself is being pushed towards smaller, independent pieces of hardware which may have limited power and/or computational abilities. One such initiative is often refereed to as Operational Responsive Space (ORS). The primary goal of ORS systems is acceleration of the mission conception-to-launch timeline of spacecraft by means of utilizing off-the-shelf type modular components for construction of the spacecraft. With such modular systems, customized interfacing and software necessary to direct all data to a central processor may not be possible given the accelerated timeline, the unfortunate result of which would be degradation of the estimates due to missing data. Graduate Student, Department of Mechanical & Aerospace Engineering. E-mail: ckn@buffalo.edu. Student Member AIAA. Professor, Department of Mechanical & Aerospace Engineering. E-mail: johnc@buffalo.edu. Associate Fellow AIAA. Senior Professional Staff I, SEG, Space Department. Email: adam.fosbury@jhuapl.edu. Member AIAA. Assistant Professor, Department of Aerospace Engineering. Email: cheng@ae.msstate.edu, Senior Member AIAA.

Pseudospectral method based trajectory optimization and fairing rejection time analysis of solid launch vehicle

The problem of real-time trajectory optimization for small solid launch vehicle of operational responsive space (ORS) was studied by using pseudospectral method. According to the characteristic of the trajectory design, the dynamics model was set up in the inertia right-angled reference frame, and the equation and parameter at the orbit injection point were simplified and converted. The infinite dimension dynamic optimal control problem was converted to a finite dimension static state optimization problem and the algorithm reduced the complexity so as to become a general algorithm in trajectories optimization. With the trajectories optimization of a three-stage solid vehicle with a liquor upper stage as example, the model of the trajectory optimization was set up and simulations were carried out. The results demonstrated the advantage and validity of the pseudospectral method. The rejection time of fairing was also analyzed by the simulation results, and the optimal flight procedure and trajectory were obtained.

Operationally Responsive Space: A New Defense Business Model

Space capabilities are a prominent element within the collection of global advantages the United States enjoys today. Space is one of the commons, along with the sea and cyberspace, that constitute the triad of capabilities on which America's global power rests. But several ominous trends now compel a reassessment of the current business model for meeting the nation's needs for military space capabilities. While the existing model has served the nation well, a new business model is at hand and can now be readily grasped to propel us into the future. Trends compelling this reassessment include: falling barriers to competitive entry into the commons of space, an increasing dependency on space capabilities, and emerging vulnerabilities in current space systems. In addition, there are systemic issues emerging across the spectrum that require a reexamination of how the nation acquires these precious assets. Such issues include: the fact that important space programs are in trouble for reasons either financial or technical; the growing need to recapitalize space capabilities; decreasing industrial base viability; reduced science and technology funding; and the need to develop space professionals. The current business model for space is unable to support, by itself, the combined weight of these accumulating pressures. The context of space technology is also undergoing rapid change. While the cost to place a kilogram of capability on orbit remains expensive, the capability resident in every kilogram is soaring, given the unrelenting increase in information technology. This makes a new, complementary business model for space feasible. The door for much smaller satellites, weighing less than 1,000 kilograms, and even micro and nano-satellites is opening, allowing the Department of Defense to redefine cost and mission criticality curves, increase transaction and learning rates, and to favorably change the risk calculus. The old business model will not work in the development of these smaller satellites and cannot be modified to acquire the new capabilities. The new business model is derived from new technology, lower costs, and a new set of output-oriented metrics. As we move toward the age of the small, the fast, and the many, it's time to start applying these precepts to space. There also is an operational imperative underlying the rapid adoption of this complementary and broader business model. Done correctly, this new model, with its flexibility and responsiveness, will ensure America's space superiority well into the future. Second, the model can serve as a test bed for the larger national military space program by allowing the Defense Department to leverage targeted science and technology investments while enhancing the professional development of military and industry space talent. So, national security space capabilities can grow out of this new model, but without the current problems and risks. Finally, by adopting this co-evolutionary process of pairing concepts and technologies, change can be influenced immediately. This model has at its core a generational development and acquisition strategy. In short, it is within our grasp to create new options in space, a process which itself can be a very powerful competitive advantage. Operationally Responsive Space (ORS) is the term used to describe this new, complementary business model. Rather than teasing operational capabilities from systems designed and paced for larger national security capabilities, the full spectrum of critical capabilities are created from the bottom up. So, the new model is about defining a joint military demand function and providing joint military capabilities for operational- and tactical-level commanders. Finally, the model emphasizes short cycle times and accelerated learning, providing high-speed iterative advancement in operational capabilities. This new model is closely aligned with Harvard Business School Professor Clayton Christensen's Disruptive Innovation Model. …