### Overview

In this challenge, students must program a rover to get from point A to point B on a map without driving across any of the craters located between the two points.

Students will:

• Understand ratio concepts and use rate reasoning to solve real-world problems.
• Create an engineered model, limited by criteria and constraints, designed to achieve the task of solving a complex problem.

Science and Engineering Practices

• Asking Questions and Defining Problems
• Engaging in Argument from Evidence

Disciplinary Core Ideas

• Defining and Delimiting Engineering Problems
• Developing Possible Solutions
• Optimizing the Design Solution

### Management

• Students are being asked to design, build, and program a robotic rover capable of carefully navigating Mars from a starting position around several treacherous obstacles. The programming relies on their understanding of ratios, their pre-requisite practice of moving the robot forward and backward in straight paths using only wheel rotations, and moving the arm and end effector.
• This lesson can be completed individually or within a group, although groups of two to three students of varied skill levels are recommended.
• The students need to have completed enough practice programs with their assigned robots to understand how to make their robots move straight for a distance using wheel rotations. The students will be applying their knowledge of ratios and rate reasoning to determine the appropriate number of rotations for the distance required in the challenge.
• Be sure to construct the map/course for the challenge in advance.
• Students without physical access to a robot can use a virtual coding environment, such as VEXcode VR or a virtual EV3 coding environment to develop block- or text-based code that can be executed on a virtual robot.

### Background

This grouping of two test rovers and a flight spare provides a comparison of three generations of Mars rovers (from left to right: Mars Exploration Rover, Sojourner, Mars Science Laboratory rover). Image credit: NASA/JPL-Caltech | + Expand

This map shows the route driven by NASA's Mars rover Curiosity through the 338 Martian day, or sol, of the rover's mission on Mars (July 19, 2013). Image credit: NASA/JPL-Caltech | + Expand

NASA has had robots on Mars for more than 20 years – each more technologically advanced than the last. From Sojourner in 1997, to Spirit and Opportunity in 2004, to Curiosity in 2012, technology is allowing rovers to get bigger and better, and perform more complex science. As we prepare for the launch of the Mars 2020 rover, scientists and engineers at NASA continue to improve the mechanics that allow for these robots to safely traverse the harsh and rocky terrain of the Martian surface. With more than 34 million miles between us and our Martian rovers, being able to safely drive around dangerous rocks, hills and craters is no easy task.

The surface of Mars is covered with impact craters which vary greatly in diameter. Because of the time and cost associated with sending a rover to Mars, we want to be sure we keep the vehicle safe once it arrives, and we do that by driving it (and landing it) on safe terrain.

Most of the craters we will try to avoid in this challenge are circular and therefore can be avoided by simply driving a curved path with a diameter slightly larger than the crater’s diameter.

### Procedures

1. Familiarize yourself with the engineering design process (shown in the graphic below) and use the following description to frame the challenge for students.
2. #### Identify the problem

The surface of Mars is covered with impact craters, which vary greatly in diameter. Most of the craters are circular and therefore can be avoided by simply driving a curved path with a diameter slightly larger than the crater’s diameter.

In this challenge, students must program a rover to get from point A to point B on a map without driving across any of the craters located between the two points.

#### Criteria for Success

For this challenge:

• Students may choose their own path.
• Students must program the rover to travel the path as quickly as possible by using a shorter route rather than higher speeds.
• Students must program the rover to move or turn and get their rover through the course.
• The starting point and ending point are marked as well as the location and size of the craters.
• Measurement devices like metric rulers, measuring tapes or meter sticks are permissible and their use is encouraged.
• During specified hardware practice times, students may perform test runs, calculate changes as needed for distance and determine when turns are needed to navigate the official challenge.

#### Engineering Constraints

• Once the challenge begins and the program has begun, students may not touch the rover without penalty.
• The rover must not cross over any of the crater edges.
• No sensors are to be used for navigation.
• The rover may not exceed 50% power on either motor.
• Students should program their rover to maintain a safe distance of 3 cm from the edge of any crater.
3. Show students the playing field designed.
4. Explain constraints, including rules and time limits, as detailed in the student guide.
5. Take questions from students regarding the challenge.
6. Monitor student teams for teamwork and to make sure all team members are actively engaged in the challenge. Note: Students will tend to gravitate toward their interest and comfort areas. Though a balance of strengths in a team is important, make sure all team members get some experience with all aspects of the challenge: brainstorming, designing, building, programming, troubleshooting and presenting.
7. When time is up or as each team is ready, have them run the course. Have other teams serve as judges and scorekeepers for each run.
8. Due to the variety of solutions and student skill levels, groups may finish at different times. Students who finish early can explore the extensions section below or add features to their robot such as messages on screen, flashing lights, etc.
9. After all students have completed the challenge, provide teams with time to create a reflection about their challenge and design-process experience. Reflections should include a component for academic language, and detail the obstacles faced and how students arrived at solutions. These reflections can take the form of a written sample or class presentation.

### Discussion

• What did you try that didn’t work out? How many times did you try it?
• What did you do when things didn’t work out like you expected?
• If given more time, what would your next step look like?

About students' thinking during the challenge:

• What obstacles did you or your group face in this challenge?
• How did you and/or your group confront these obstacles?
• What was your favorite part of the engineering design process?
• What do you think you have learned from this process you didn’t know before?
• Consider asking students about how wheel design is important for building a rover capable of traversing more demanding terrain. How did wheel design change throughout the years as bigger rovers have been sent to Mars? What differences do you observe in wheel design and what benefits could those changes impart?

### Assessment

Points for this challenge will be as follows:

 The rover navigates from A to B maintaining a 3cm safety margin for each crater. 60 points Complete the course in the shortest time span 10 points Motor exceeds 50% power -2 points for each second over 50% power Crossover or touch a crater -4 points (each instance) Violate 3 cm safety margin without touching edge of crater -2 points (each instance) Touch the rover outside of the start position -2 points (each instance)

Example scoring rubric:

 Expert Proficient Intermediate Novice Prototype Description Drawing clearly marks key features of the prototype critical to the function and meets the needs of the problem. Description fully discusses all components of the prototypes and how they address the needs of the problem. Drawing clearly marks key features of the prototype critical to the function and meets most of the needs of the problem. Description discusses components of the prototypes and how they address the needs of the problem. Drawing marks a couple key features of the prototype critical to the function and meets a couple of the needs of the problem. Description discusses components of the prototypes. Drawing marks a key feature or two. Description and design reflect only the personal interests of the group. Challenge Completion Scored 50 points Scored 36-49 points Scored 21-35 points Scored Below 0 - 20 Designing Reflection Reflection fully acknowledges the need to fail and make multiple iterations, yet is still forward thinking to the next steps of the design. Reflection fully acknowledges the need to fail and make iterations, yet is still forward thinking to the next steps of the design. Reflection fully acknowledges the need to fail and make iterations and there are next steps but these are undefined. Reflection discusses the success of the first or second prototype and points to this as the final product. Thinking Reflection Reflection fully acknowledges the obstacles during the process and provides concrete examples of learning as a result of these obstacles. Reflection acknowledges the obstacles in the process and provides a concrete example of learning as a result of these obstacles. Reflection acknowledges the obstacles in the process and makes an unspecified claim about learning as a result of these obstacles. Reflection discusses the success without mention of obstacles or learning opportunities.

### Extensions

This material is based upon work supported by the NASA STEM Educator Professional Development Collaborative at Texas State University under the NASA cooperative agreement award number NNX14AQ30A.