In this lesson, students discover the entire process that goes into designing a rocket for any customer. In prior lessons, students learned how rockets work, but now they learn what real-world decisions engineers have to make when designing and building a rocket. They learn about important factors such as supplies, ethics, deadlines and budgets. Also, students learn about the Engineering process, and recognize that the first design is almost never the final design. Re-Engineering is a critical step in creating a rocket.

When designing a rocket, engineers must not only consider how far and fast it needs to go, but also how much it will cost, how safe it will be, how heavy it will be, and what impact it will have on the environment. Very often, the strongest design will be too heavy or too expensive. That is why engineers must often find a compromise that satisfies all the requirements of a project. Engineers also often make several design iterations along the way. This means they design and test a rocket, discover what needs to be fixed, and then redesign and test until they come up with a successful final design. Newton motion rocket thrust weight control process design re-design tradeoffs After this lesson, students should be able to: Define and give an example of a "tradeoff" in engineering design. Explain that engineering design has several steps, that a project is not usually perfect after the first design, and it may take several redesigns before a project is considered done. Give an example of a factor to consider when building a rocket, such as: limited money, the needs of the customer, limited time, resources, ethical considerations, environmental considerations, safety considerations, as well as the rocket's performance. What are some questions that engineers have to take into consideration when designing a rocket? More specifically, what are Spacewoman Tess and Spaceman Rohan's needs for their rocket? This is perhaps the most important question because as their engineering team, they are your customers, and you are providing a service to them by designing a rocket that fits their needs. (Write their answers on the board. They might come up with things like: How high does it need to go? How much weight does it have to carry? How much can it cost? How safe does it need to be? Is it going to harm the environment? How long do we have to build it? For younger kids you may have to prompt them to get answers. How will the rocket be used? (Answer: It will be used to carry satellites and a spacecraft for Tess.) How will it be fueled (i.e., what type of propellant?)?) So, let's look at our list. There are a lot of things an engineer must think about when designing a rocket, or anything for that matter. Let's think about this question, "How much weight does the rocket have to carry? What does it need to carry?" Do you remember that our rocket needs to carry satellites for Maya, a spacecraft for Tess, and all the propellant to get the rocket up into space - a very heavy load! How might you go about designing a rocket to carry a lot of weight? (Possible answers: put in a huge rocket motor, make the rocket very light, or use a very powerful rocket such as a nuclear rocket.) All of these ideas would likely work, but some of them might not be good matches for the other questions on the board. For example, a bigger rocket can lift more, but it will cost more and might take longer to build. Or, a lighter rocket might be made out of very expensive materials or might not be strong enough to endure the stresses of launch. A nuclear rocket might not be safe and could potentially damage the environment if there was a disaster during/after liftoff. Engineering is a delicate balance between many types of different factors. Engineers call these necessary decisions that affect other actions tradeoffs. We might be able to make a super powerful rocket that is inexpensive, but it might be very harmful to the environment. This is the tradeoff. A rocket might have some good qualities and some bad qualities. If the bad qualities outweigh the good qualities, then we should look for a different rocket design. When designing a rocket, an engineer must keep in mind the rocket's uses, performance, cost, deadlines, safety, weight, controllability, environmental impact, and many other factors which must be carefully balanced in order to create a successful rocket. Do you think engineers always get a rocket design right the first time? The answer is no! It takes many re-designs to get something as complicated as a rocket right. An engineer calls this process re-engineering. It is simply learning from the mistakes of the past and applying those lessons learned to better a product. We do that with homework too, right? We learn from our mistakes and do a better job next time. Today you will learn about the actual engineering process and how it applies to designing a successful rocket for Tess, Rohan and Maya. Problem Identification: The first step in the Design Life Cycle is determining what the problem is ─ or what the customer needs. Engineers are problem solvers at heart. Their job is to design and build something better than before. Sometimes this involves modifying an old idea and sometimes it means starting from scratch with a whole new idea. At the beginning of a project, an engineer starts out with a list of requirements, or things that a product must do. For a rocket, requirements might include how fast it must be, how safe it has to be, how much it can cost, how much it can weigh, or when does it have to be completed. The requirements define what needs to be done to accomplish the project, or job. It is the engineer's job to come up with a solution to the problem that meets all the requirements. Forming Ideas: The next step in the engineering design process is an idea: "I wonder if…" The idea phase is where a group of engineers will brainstorm a bunch of ideas that might work as a solution to a problem. When these ideas are combined, a rough idea for a solution is complete. Feasibility: Engineers must then decide if the solution they came up with is feasible. Feasibility is not a question of "is it possible" (since little is impossible in today's high-tech, fast-changing world), but the questions are: can we afford it, is it safe, and is it the right thing to do? Projects are judged for feasibility by a panel of reviewers with strengths and expertise in science, engineering and project management. Conceptual Design: Once a project is deemed to be feasible, the next step is the conceptual design. The primary questions that are answered during the conceptual design are: What is the general configuration of the structure to be built? What major trade studies should be made (i.e., hardware, software, materials)? What is it going to cost (calculated estimation)? How long will it take (calculated estimation)? The design that comes out of the conceptual design phase is not the final design, but during this phase many of the important questions about what the final design will look like are answered. Preliminary Design: If the conceptual design is acceptable, the team can move on to the preliminary design. Actions for the preliminary design are: Perform trade studies (decide on best components, materials, etc.). Create initial detailed designs. Create a detailed schedule and cost plan. Further develop concepts with the goal of reducing risk. Establish sufficient margins of safety. Detailed Design: The detailed design phase is where the detailed design is agreed upon and finalized. The customer must be happy and agree with the design, budget and schedule before anything can be built. Build and Test: This is the point where the manufacturing of hardware begins. (Presumably) all design details are complete and every part of the design is ready to proceed into reality. As part of this work, engineering models are often constructed for performance checks and tests. These tests are done with significant margins added to each of the tests - making them more extreme than anticipated during the mission. Any failures or weaknesses in the design must be corrected (back to conceptual or preliminary design) and retested to prove the product will fulfill its requirements. Delivery of Product: Finally, after much hard ─ yet very satisfying ─ work, the product is then delivered or sold to the customer along with documentation of all tests and operations to prove that the design works. Design, testing and re-design are integral parts of engineering that improves the final product. Nothing is ever just right the first time. Mistakes are inevitably made, but engineers learn from their mistakes, which are used to improve the product during redesigns. Even a design that works can be improved ─ maybe it can be produced even more inexpensively, maybe it can last longer, maybe it can be faster, etc. Attached are some examples of rockets and their builders. Note that some of the rockets have numbers after their name: a number that is increased each time they re-design and improve the rocket! A detailed plan for the resources and money available for a project. Making sure that the basic engineering design is not only possible physically, but also to make sure that it can be built and satisfy all the requirements (i.e., cost, timeline, safety, ethically, etc.). To learn from mistakes of the first design to improve the next design. Giving up one thing in return for another. Rockets on a Shoestring Budget How often do we come across limited resources? Are there enough swings on the playground for every student to have one? (Answer: no, of course not) What do you do if there is not enough of something? (Answer: share) If three kids are sharing a swing for 10 minutes, is it fair for one to stay on for 30 minutes? (Answer: no) If your parents gave you a dollar to buy candy, can you buy all the candy in the store? (Answer: No, you must pick from everything available.) How do you decide which candy you will buy? Why is one candy better than another? Would you choose a candy that tastes the best but only lasts 30 seconds or a candy that does not taste as good but you can enjoy it for 5 minutes? (Answer: Depends on what is valued more: taste or duration of enjoyment.) Sometimes we have to make "tradeoffs" to get the most out of an object or activity. You may have to tradeoff length of time on the swing to let everyone use it. You may have to tradeoff duration for a candy that tastes best. Engineering projects also have tradeoffs. Sometimes the tradeoff is weight, control or thrust for cost or money. Sometimes it is the materials available with which they can build. The engineering process takes many steps to ensure that all the requirements are met, and that is when tradeoffs happen. Also, an engineering project is never perfect the first time, and it often takes several redesigns to get it right. Even with the proper engineering tools and knowledge of rocket design, an engineering team still needs familiarity with the engineering process to be in tune with the customer's needs. Hopefully, now as Tess and Rohan's engineering team you have all the tools necessary to meet their need to get Maya's satellites to space and turn Tess' explorations into reality. Prediction: Have the students make a prediction on the following question: How many people think they can build a perfect rocket on the first try? (Tally student answers on the board. Tell the students that they will learn whether or not most engineers can design something right on the first try today.) Discussion Question: Solicit, integrate and summarize student responses. When a company wants to build a rocket, does someone just give them the materials for free? (Answer: No, cost is a very important consideration in an engineering project. Before a group of engineers receives money to build a rocket, they must have a detailed design that outlines how the rocket will perform, how much it will cost and how long it will take to build.) Reasonable Question or NOT? Spacewoman Tess, Spaceman Rohan and their daughter Maya are incredibly busy planning their trips. They have given you, as their engineering team, 5 minutes to ask them a few questions regarding their rocket design. Have the students as a class vote on whether or not the following questions are reasonable questions to ask regarding designing Spacewoman Tess' rocket: What is the purpose of the rocket? How much money do we have to build the rocket? Should the rocket be pretty or ugly? How much time do we have to design and build the rocket? When do you need the rocket? How long will you need to be in space? What are the satellites for? When will the satellites need to be in orbit? What color should the rocket be? Brainstorming: In small groups, have the students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Encourage wild ideas and discourage criticism of ideas. Ask the students: What are some steps you think engineers have to take to design a rocket? (Prompts: Do they have to think of ideas? Gather materials? Build a model? What else?) What are some trade-offs an engineer might have to consider when designing a rocket? (Possible answers include: safety, cost, materials, height of launch, weight, etc.) Design Flowchart: Have the students create a list and description of the steps in an official engineering project. Also, have them produce these steps in a flowchart (see Figure 2). Ask them what happens when there is some weakness or problems during the build and test phase? What would you do and back to which step does that take you? Problem Identification Forming Ideas Feasibility Study Conceptual Design Preliminary Design Final Design Build and Test Re-Engineering Delivery of Product Break students into teams. Have each team draw a picture to illustrate each step of the engineering design process. Hang these drawings around the room to remind students of the engineering design process. Have the students research a rocket and write a one-page paper about the engineering history of that rocket. They should answer questions such as how long did it take to design? How much did it cost? What were the requirements for the rocket? And were there any tradeoffs made during the design?