Spaceflight
MechanicsCornell Certificate Program

Spaceflight mechanics may seem like a new and exciting field, one tied to cutting-edge innovations in technology, but the fundamentals of spaceflight are also the fundamentals of classical mechanics, both of which use the common language of vectorial analysis. To solve the more complex dynamics problems that you will encounter throughout this program, you first need to ensure that you increase your fluency in this common language of vectorial analysis; i.e., vectorial calculus and vectorial algebra.

In this unit, you will start by reviewing the mathematical conventions that form the basis of vectorial analysis. This will provide you with the foundation you’ll need to solve dynamics problems for objects in space and practice different ways of measuring space and time when analyzing space systems and planning for orbital maneuvers. You’ll complete the unit with a solid grasp of which standard definitions are at your disposal when approaching a new problem in astrodynamics.

To conclude the unit, you will complete a series of written assignments and MATLAB assignments to help you increase your comfort level with the calculations involved in most dynamics problems. The concepts should already be familiar to you, and the conventions you review will be consistently applied throughout your study of spaceflight mechanics.

The two-body problem (two point masses interacting via gravity, with no other forces present) is the fundamental building block of celestial mechanics. In fact, the two-body problem is the only orbital mechanics problem with an exact solution, allowing you to express the positions of both bodies in the past, present, and future, with a single mathematical expression.

Although, in practice, you are unlikely to deal with two bodies in the strict sense, many complex systems behave like collections of two-body orbits that gradually change over time. Building a solid understanding of the two-body problem is therefore critical as you continue your studies in spaceflight mechanics.

In this unit, you will start to build an analytical and geometric intuition for how two-body systems work. You’ll accomplish this by analyzing the two-body system in three different ways: using Newton’s law of gravity and Newton’s second law to derive the conic section solution, using Kepler’s laws to provide a geometric interpretation to this solution, and using conservation of energy to gain further understanding of the relationship between orbit positions and velocities.

You’ll practice applying these methods in both written and MATLAB assignments, which will ultimately equip you with critical insights into the physics of orbits.

A two-body orbit can be thought of as a static structure in space, but in practice, real orbits evolve in time due to gravitational and non-gravitational effects not captured in the two-body model. In many cases, we can think of these additional effects as orbital perturbations — forces that are small compared with the primary gravitational pull between the two bodies and leading to very gradual changes in the Keplerian orbital elements. The study of orbital perturbations builds directly upon our understanding of two-body orbits and their geometric and physical interpretation, then expands these to model orbits whose properties change in time.

In this unit, you will delve into the concept of osculating orbital elements and mathematical tools to analyze the effects of perturbing forces. You’ll also explore the most common sources of these perturbations. You’ll then examine examples of orbits that take advantage of perturbations to accomplish things that are impossible with regular two-body orbits as well as orbits explicitly designed to account for perturbations that would otherwise destroy a desired orbital geometry.

Thus far, you’ve studied the natural evolution of orbits, predicting what will happen to objects in space when they interact with forces in the natural environment. But what happens when you apply control to a spacecraft? Though you will spend very little time controlling spacecraft in reality — usually it just coasts along a particular orbit — it is critical that you know how to take control of your spacecraft’s orbit and have it go where you want it to go.

In this unit, you will practice applying a variety of mathematical models to understand how to use the propulsive capabilities of your spacecraft in order to modify its orbit. You’ll apply your understanding of orbital maneuvers by working through problem sets focused on field applications.

Although space propulsion involves many subtopics and could easily fill several units, this unit covers a state-of-the-field introduction to propulsion concepts. You will discover the basics of propulsion for space missions: the ideal rocket equation, in-space propulsion, fuel use, and launch operations. You’ll study chemical and electrical propulsion methods as well as future propulsion options, including solar sails and electromagnetic systems. You’ll then apply your understanding of propulsion systems by working through problem sets focused on field applications.

Understanding and controlling the orientation of a spacecraft is just as important as controlling its orbit and position. To understand spacecraft orientation — also known as attitude dynamics — you will study the mathematical language and toolset for dealing with attitude and the kinematics of rigid body orientation.

You will then consider the kinetics, or dynamics, of these rigid bodies. You’ll apply an extension of Newton’s second law, called the internal moment assumption, to consider angular momentum. Finally, you’ll revisit key concepts of energy to describe rigid body behavior in an actual spacecraft.

To control a spacecraft, you need to know how to determine its orientation and position in inertial space. Stabilizing and controlling a spacecraft’s attitude is crucial for various applications, and you can manipulate your attitude control system (ACS) to achieve preferred orientations. The choice of approach and hardware depends on the pointing accuracy you hope to obtain.

In this unit, you will focus your attention on attitude kinematics and the orientation dynamics of spacecraft. You’ll first enhance your understanding of three-dimensional rigid body dynamics then review classes of attitude control hardware such as reaction wheels, control moment gyros, magnetorquers, and reaction control systems. You’ll also examine attitude control and determination: dynamics, equations of motion, control laws, and attitude sensors. Finally, you will explore the methods for attitude control and attitude estimation.