CubeSat Fall 435
CubeSat Advisors: Mechanical: Dr. Robert Ash ECE: Dr. Dimitrie Popescu 435 Team Members: Kevin Scott- Team Lead Robert Kelly- Orbital modeling and power Austin Rogers- Attitude control (Physical) Joseph Kingett-Attitude control (Logic) Matthew Degroff- Prototyping and Thermal
Mission Statement Exploit low-cost CubeSat orbital platform opportunities to design, build and orbit a scientific satellite, providing opportunities for innovation, scientific research, and student learning. Working with Hampton University, ODU will investigate the influence of solar activity on space weather, while demonstrating a new deployable drag brake design for accelerating orbital decay.
Primary Mission Objectives 1. Provide a hands-on, student-led flight project experience for undergraduate students by designing, developing, integrating, testing and flying an orbital constellation of three 1U CubeSats (with VT and UVa) 2. Obtain measurements of the orbital decay of a constellation of satellites to develop a database of atmospheric drag and the variability of atmospheric properties 3. Evaluate and demonstrate a system to determine and communicate relative and absolute spacecraft position across an orbiting constellation.
Secondary Mission Objectives 1. Advance and popularize CubeSats and associated technologies 2. Further our understanding of earth and space science, as well as develop new space technology that will enhance our space exploration capabilities 3. Successfully deploy drag brake to document orbital lifetime reduction via alteration of ballistic coefficient.
Background The drag forces acting on orbiting objects depend on the shape, speed and local density of the atmosphere. Spacecraft in Low Earth Orbits (LEO) traverse the Thermosphere, and that part of the atmosphere is controlled by solar activity. The science data obtained from single satellite missions invariably suffer from an issue known as spatial-temporal ambiguity. The problem arises because a satellite traveling through the LEO space environment is moving much faster than the thermal speeds of the gas particles in the medium. As a consequence, the measurements made aboard a spacecraft are similar to a series of photographic snapshots from different locations each snapshot captures a dataset that represents the geophysical conditions at a particular location and a particular time.
The Problem With the advent of small satellite systems such as CubeSats these goals are now within reach a constellation of many tens of CubeSats can be launched for less than the cost of a single Explorerclass mission. Despite their attractiveness, there are many practical obstacles to be overcome: 1. How do we develop software tools to ingest, analyze, and interpret large volumes of data from many satellites making simultaneous measurements? 2. How do the individual satellites adjust their relative locations and orbit parameters to make the best science measurements for a particular mission? 3. How do the satellites in a swarm keep track of the positions of other elements in the constellation, as they must to avoid collisions and to allow their data to be interpreted correctly?
Concept of Operations Three 1U CubeSats, housed within a 3U dispenser, will be placed in orbit aboard a launch vehicle. Subsequently, each 1U CubeSat will be deployed directionally, with respect to the primary orbit of the host vehicle, forming a constellation. One CubeSat will function as the primary communication satellite and will first establish a communication link with the ground. Then, the other two CubeSats will establish communication links with the primary CubeSat. After the three CubeSats have established their primary communication links, the CubeSat serving as the communications hub will signal the ground station, initiating mission operations and performing systems checks. Based on the initial orbits, and their line-of-flight orientations, data will be acquired to determine the drag force and local atmospheric density for the deployed CubeSats. After the constellation phase of the project has been demonstrated, a tethered drag brake will be inflated and deployed from the ODU CubeSat, producing a substantially different ballistic coefficient and orbital flight profile. Each CubeSat will incorporate accelerometers, gyroscopes and magnetometers, capable of measuring non-gravitational accelerations, spacecraft orientation with respect to the line-of-flight, and pitch, roll and yaw rates. Those data will be acquired and transmitted to the communication hub, for reception by the ground station radios directly or via the Globalstar network.
Concept of Operations
CubeSat Teams (Mechanical):
CubeSat Teams (Electrical):
Gantt
Prototyping and CubeSat Development The first part is focused on structural analysis of the CubeSat Justify the material being used (3D-printed Windform or aluminum) Aluminum: Density= 2.7 g/cc Tensile elastic modulus= 69 GPa Windform XT 2.0: Density= 1.1g/cc Tensile elastic modulus= 8.93 GPa Justify the structural design choices (seeking to find structural flaws)
Prototyping and CubeSat Development
Prototyping and CubeSat Development
Prototyping and CubeSat Development Thermal Control Internal CubeSat temperatures must remain within safe operating requirements for the electrical components. Expected conditions Heat conduction and thermal radiation are the only transport mechanisms. Heat generation from the electrical components and waste heat from the solar panels will be modeled.
ADCS logic Magnetorquers follow the equation: τ=μ B τ is the magnetic torque result μ is the magnetic moment of the solenoid B is the Earth s magnetic field If current is flowing through the wire, it produces a magnetic field It will react with the ambient magnetic field producing a torque that acts about an axis that is orthogonal to the plane containing μ and B Producing rotation about the torque axis B I
9DOF Test
Attitude Dynamics and Control System (ADCS)-physical - Magnetorquers use the interaction between their own magnetic field and the magnetic field of the Earth to control satellite attitude. - Fabricated a prototype magnetorquer - Conductive core - Two layers of ~400 turns each - Field magnitude of 4.59 Gauss using a 9V battery - Improved prototype magnetorquer - Still in development - Air core, flat wound - Similar to magnetorquers integrated in GOM Space solar panels
Power Simulations using a feature of Satellite Toolkit (STK), called the Solar Panel Tool, are underway to determine the solar power generation potential for different solar panel placement scenarios, satellite orientations, and different numbers of solar panels (including half-panels that cover half of one face of the CubeSat). Open source MATLAB code is also being used to supplement the simulations.
Orbital Simulations Using STK, the nominal orbit of the CubeSat constellation (assumed to be the ISS orbit) the seasonal variation of sunshine in an inclined 52 o orbit is being studied, since available solar power will depend on deployment date. The biggest task in orbital simulation at this point is to get a 3D model of the CubeSat into STK so that flight coordinates can be simulated as well, for the purpose of knowing the sun s position with respect to the CubeSat at any given time.
Orbital Simulation
Questions?