Constant Rate Production: DOE Approach to Meeting NASA Needs for Radioisotope Power Systems for Nuclear-Enabled Launches
Robert Michael Wham,
George Behrens Ulrich,
Jacquelyn Candelaria Lopez-Barlow,
Stephen Guy Johnson
Issue:
Volume 5, Issue 2, December 2018
Pages:
63-70
Received:
10 September 2018
Accepted:
4 October 2018
Published:
23 October 2018
DOI:
10.11648/j.ajae.20180502.11
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Abstract: The use of radioisotope power systems (RPSs) for nuclear-enabled National Aeronautics and Space Administration (NASA) missions is made possible through a long-standing arrangement between the Department of Energy (DOE) and NASA. The requirements for the power system come from NASA, but DOE performs the procurement, fueling, testing, and delivery. A challenge has been interplay between the schedule for RPS availability from DOE versus the schedule for competitively selected missions. By mutual agreement, the actual operations to procure an RPS and prepare it for fueling have always been delayed until the final selection of a mission. The timeline for a New Frontiers–class mission leaves approximately 5 to 6 years from the time of final mission selection to the actual launch date. The number of RPSs used for a New Frontiers–class mission can be one to three units. If one or two units are needed, the timeline from the decision point to the launch date is a challenge, but it is achievable. The activities taking place include manufacturing the power system, producing the fuel, and performing the assembly/testing and delivery operations. If the mission selected requires three RPSs, the logistics of accomplishing all activities during the 5–6 years is problematic. The challenge involves obtaining the necessary resources for plutonium production, heat source production, and assembly/testing operations. Typically, the time between RPS-enabled missions requires staffing reduction down to 65%–75% of peak staffing levels to reduce costs. Coupling the ~2 year duration needed for hiring, training, and obtaining the appropriate security clearances for the required staff with the requirement for the RPS to arrive at Kennedy Space Center 6 months before the launch erodes much of the 5–6 years available to comfortably support the use of three RPSs. To provide better support for NASA RPS missions, a different approach for the production of heat sources was devised—constant rate production. This involves a higher level of base capability at DOE national laboratories to provide a stabilized workforce. This will enable 10–15 heat sources to be produced annually and placed into a stable intermediate form to enable storage for up to several years leading to quick production of general purpose heat source modules when a mission is selected. The upfront production of 238Pu is maintained so material is constantly in the pipeline. Production of key specialized components is also maintained using this model.
Abstract: The use of radioisotope power systems (RPSs) for nuclear-enabled National Aeronautics and Space Administration (NASA) missions is made possible through a long-standing arrangement between the Department of Energy (DOE) and NASA. The requirements for the power system come from NASA, but DOE performs the procurement, fueling, testing, and delivery. A...
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Hypersonic Glider Autopilot Using Adaptive Higher Order Sliding Mode Control with Impulsive Actions
Christian Tournes,
Yuri Shtessel,
Allen Spencer
Issue:
Volume 5, Issue 2, December 2018
Pages:
71-86
Received:
28 August 2018
Accepted:
14 September 2018
Published:
25 October 2018
DOI:
10.11648/j.ajae.20180502.12
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Abstract: Hypersonic glider designs often exhibit limited control authority and poor transversal stability. Furthermore, the methods used for aerodynamic performance estimation at high flight altitudes and hypersonic speeds are inevitably inaccurate and uncertain. Hypersonic Glider performance could be severely degraded by using traditional control and autopilot techniques that rely on an accurate knowledge of the aerodynamic coefficients. A new autopilot and control approach, presented in this paper, is based on recently developed special Higher Order Sliding Mode Control (HOSMC) algorithms that are mostly based on relative degrees but not on the glider’s mathematical model. Specifically, this autopilot and control approach includes robust continuous aerodynamic control augmented by impulsive reaction control thrusters. Control gain-adaptation allows addressing the vehicle bounded uncertainties and perturbations without overestimating the control gains. The impulsive augmentation of the continuous Higher Order Sliding Mode control provides almost instantaneous convergence thereby mitigating the risk of control loss caused by sideslip angle departures due to poor transversal stability and small lateral control authority. While Higher Order Sliding Mode control algorithms are inherently insensitive to the matched uncertainties and disturbances, the observers embedded in the Continuous Higher Order Sliding Mode Control algorithms reduce the time response of the control compensation. Simulation of a representative hypersonic glider executing normal and bank-to-turn maneuvers and controlled by the studied algorithms demonstrate excellent performance in the presence of significant model uncertainties and perturbations.
Abstract: Hypersonic glider designs often exhibit limited control authority and poor transversal stability. Furthermore, the methods used for aerodynamic performance estimation at high flight altitudes and hypersonic speeds are inevitably inaccurate and uncertain. Hypersonic Glider performance could be severely degraded by using traditional control and autop...
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Researches on a Martian Modular Base Shielded by an Artificial Magnetic Field
Issue:
Volume 5, Issue 2, December 2018
Pages:
87-95
Received:
11 September 2018
Accepted:
11 October 2018
Published:
7 November 2018
DOI:
10.11648/j.ajae.20180502.13
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Abstract: This proposal for the future colonization of Mars starts from the purpose of creating an expandable and modular community made of elements as transparent as possible with large windows that allow the view of Martian landscape as to mitigate psychologically effects derived from long stay away from planet Earth. To realize this aim, it will be necessary to protect the settlement from the dangerous cosmic rays that the Martian atmosphere could not sufficiently shield, at least in relation to the long period of stay expected for the future settlers. It will be demonstrated that it is possible to reach this goal by positioning the inhabited elements of the future base below a huge toroid made of electric cables driven by high voltage current that generates externally a magnetic field strong enough to shield the cosmic rays but, at the same time, almost null inside of it. To confirm this hypothesis, it has been realized a scale model of the Martian base, made by some electric cables arranged around a toroidal frame and run by low voltage current. The tests demonstrate that inside the toroid section the magnetic field is actually almost null, while outside it reaches values directly proportional to the current intensity that has been used to power the system.
Abstract: This proposal for the future colonization of Mars starts from the purpose of creating an expandable and modular community made of elements as transparent as possible with large windows that allow the view of Martian landscape as to mitigate psychologically effects derived from long stay away from planet Earth. To realize this aim, it will be necess...
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Adapting SE (3) Nonlinear Geometric Method to Control Single-Tri Rotors with Integrator
Dinh-Thinh Hoang,
Thi-Hong-Hieu Le,
Ngoc-Hien Nguyen
Issue:
Volume 5, Issue 2, December 2018
Pages:
96-105
Received:
4 October 2018
Accepted:
18 October 2018
Published:
21 November 2018
DOI:
10.11648/j.ajae.20180502.14
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Abstract: This paper presents a new method for controlling tri rotor-type unmanned aerial vehicles (UAV) adapted from the SE (3) nonlinear geometric method for quadrotor-type UAV. Like its predecessor, the control strategy for single tri rotors is realized in a hierarchical architecture, containing both attitude controller and position controller. As a basis, the mathematical dynamics of the tri rotor is given in form of rotation matrix that ensures the algorithm is independent from any specific representation, such as Euler angle or quaternion. Assumption about primary thrust component is made to decouple the equations of the controllers to find an appropriate reference target for the attitude controller. An integral action is proposed to alleviate the steady-state error that arises from incorrect modelling due to simplification. This is justified by a Lyapunov function that also yields additional conditions for parameter gains setup. Output of the controller includes desired torque components, as well as total thrust magnitude. It is from this point that divergence from the original method for quadrotors becomes prominent. A numerical solver is introduced to yield the desired motors’ angular speed and tail servo angle. Some numerical examples implemented on MATLAB/Simulink illustrate that the controller is able to correct steady-state error and gives quick response, just like its quadrotor-type counterpart.
Abstract: This paper presents a new method for controlling tri rotor-type unmanned aerial vehicles (UAV) adapted from the SE (3) nonlinear geometric method for quadrotor-type UAV. Like its predecessor, the control strategy for single tri rotors is realized in a hierarchical architecture, containing both attitude controller and position controller. As a basis...
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