Tag Archives: featured

Spring 2019/Midterm/ 25 Feb 2019

Midterm exam can be found by clicking the link: AEM_591_Exam_Orbit_Determination

This marks the end of the necessary background for orbit determination.

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Learning Creo Parametric (New CAD tools!)

I recently installed and started teaching myself the Creo suite of tools. I needed a replacement for AutoDesk Inventor. I’ve posted the finished product of the tutorials for building a piston/ piston shaft. I would like to reach the same capability I previously held with Inventor. For those of you not familiar with Creo, Wikipedia offers this:

Creo Elements/Pro and Creo Parametric compete directly with CATIA, Siemens NX/Solidedge, and SolidWorks. The Creo suite of apps replace and supersede PTC’s products formerly known as Pro/ENGINEER, CoCreate, and ProductView.

I previously used AutoDesk Inventor to make the Gulfstream GV/ G550 model (Gulfstream G-V CAD). Dr. Charles O’Neill has reproduced a version of this model in CATIA. The article describing the model is here: https://charles-oneill.com/blog/gulfstream-gv-g550-cad-model/ His model is available on GrabCad: https://grabcad.com/library/gulfstream-gv-g550-low-fidelity-2

GV-pods

Gulfstream GV / G550 CAD Model

Engineers/pilots will notice, on my model, the abscence of wingtips and the exact airfoil is reproduced as best as possible for being lofted from drawings. This drawing was intended as low fidelity to facilitate a proposal. It meets those requirements.

Completing the Creo tutorial required some breakdown between both the text and the videos provided. Completed exercises are shown below.

creoparametric_ex1

A piston created in Creo (Creo Beginner Exercise 1)

creoparametric_ex2

A crankshaft to emphasis patterns and simplifying (Creo Beginner Exercise 2)

[youtube https://www.youtube.com/watch?v=i_oc1Cko-KI&w=560&h=315]

Spring 2019/Lecture 12/Real Measurements 2 – 22 Feb 2019

Two way ranging and Doppler systems are summarized. Differenced measurements or “differencing,” is explained. For additional explanation on differencing see Penn State’s course for Geospatial and GNSS professionals (https://www.e-education.psu.edu/geog862/node/1727).

There was some difficulty with projecting the slides to the screen so they have been added after the lecture was recorded.

Sign up for updates here: OD Course Landing Page (Syllabus/Schedule)

Slides: L12 Slides – Real Measurements 2

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Spring 2019/Lecture 11/Conceptual Example – 20 Feb 2019

The environment and relativity effects on radio and optical communications are introduced.  One-way range measurement systems are introduced. GPS is provided as an example but it still applies to GLONASS and Galileo. Two-way range, Doppler, and differenced measurements are considered next.

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Slides: L11 Slides – Real Measurements

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Spring 2019/Homework 2 Solution

Demonstrate understanding of orbital mechanics necessary to complete orbit determination course. In problem 1, position and velocity are converted between osculating elements and sub-satellite points. In problem 2, the receiver measurements confirm the node location varies over time. In problem 3 the equations of motion are numerically integrated for a GLONASS satellite for one day.

Sign up for updates here: OD Course Landing Page (Syllabus/Schedule)

GitHub: Repository for Code Used

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Spring 2019/Lecture 5/Perturbed Motion – 6 Feb 2019

Sorry for the missed lectures on Friday and Monday. I was out sick. Assignments are due on Friday. We covered perturbations to orbital motion. We examined contributions from gravitational and nongravitational sources to the two-body motion.

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Slides: L5 Slides – Perturbed Motion

[youtube https://www.youtube.com/watch?v=HZjksLbF4go&w=560&h=315]

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Spring 2019/Lecture 4/Two Body Problem – 30 Jan 2019

We resumed today with orbital mechanics. We covered the two-body problem, introduced Kepler’s problem (time doesn’t relate well to true anomaly), and sprinted to the state transition matrix. We will resume with perturbations and additional bodies considered on Friday.

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Slides: L4 Slides – Two Body Problem

[youtube https://www.youtube.com/watch?v=Mx6PEYk_RQE&w=560&h=315]

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Updates: Ph.D. Candidate

I’ve officially passed my qualifying exams. I took my qualifiers in both Intermediate Dynamics and Space Systems. Having passed both I am officially a Ph.D. Candidate. Time to begin preparing for my thesis proposal.

Next semester will see the completion of a satellite ground station at Alabama (more on that later), the publishing of an Orbit Determination course, and my proposal.

I can’t wait to return to my research! It’s been languishing as I focused on qualifiers.

Lecture 3 – Orbital Mechanics Review B

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Lecture

I pick up again by reviewing the solution to the problem assigned during Lecture 1. (The link will take you to a solution using C++ on GitHub). A few common coordinate systems and reference frames are introduced, orbital perturbations are introduced, and an example problem to be solved in Lecture 4 is given to the class to start on.

[youtube https://www.youtube.com/watch?v=FlcF9AoNBUo]

Previous Lectures

Lecture 2

Lecture 1

Resources

Lecture 3 – Review Of Orbital Mechanics B

Lecture 2 – Orbital Mechanics Review A

Lecture 1 – Orbit Determination Concepts (slides)

AppendixA-ProbabilityAndStatistics

OD – HW 1 Solution

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Solution to Homework 1

Problem 1 provides the solution for us. We are learning how to use iterative methods to estimate the state vector. In this case we will use the Newton-Raphson root-finding method to solve for the problem. An Excel sheet is provided that walks through the first three iterations as an illustration. C++ code is provided on GitHub that will solve for the final solution and show the number of iterations.

Homework Solution 1

Excel – Visual Iterative Solution

C++ Solution