# University of São Paulo: Jupiter Project: USP students develop rocket trajectory simulator

ANDa team of four students from the Jupiter Project, a USP extension group dedicated to research and development of experimental rockets, created a rocket trajectory simulator, called RocketPy, which predicts the dynamic behavior of sounding rockets during flight, ensuring safety launches and proper planning for missions of this nature. The code has the ability to predict the behavior of rockets by estimating various physical and mathematical parameters. In addition to these estimates, atmospheric conditions at the launch site are taken into account based on historical data from meteorological agencies around the world.

The article that describes the study, entitled RocketPy: Six Degree-of-Freedom Rocket Trajectory Simulator , was published on the Asce library platform , authored by students Giovani Ceotto and Guilherme Fernandes and professor Bruno Souza Carmo, from Escola Politécnica (Poli) of USP, and students Rodrigo Schmitt, from the Institute of Physics (IF), and Lucas Azevedo Pezente, from the Institute of Mathematics and Statistics (IME), both at USP.

Is it a bird, a rocket or a missile?
The rockets typically launched by universities, including those from Project Jupiter, are medium-sized, known as sounding rockets; very different from what we see in movies and news.

Guilherme Fernandes explains to Jornal da USP that they can generally fall into two categories: those that reach a maximum height (called apogee) of 1 kilometer (km) of altitude and those that reach triple that. These more powerful ones weigh around 30 kilos (kg), are, on average, 3 meters long and can exceed 1000 km/h. At this speed they get very close to the sound barrier, that is, they are almost faster than sound, which travels at about 1200 km/h — when that happens, you hear a bang and the supersonic regime.

The most used in releases by the team are the most modest, with lesser apogee. Generally, they have 8 kg of total mass, about 2 meters in length and can reach maximum speeds of the order of 600 km/h, which means that the rocket reaches its maximum point in approximately 14 seconds, a parameter also estimated with precision by code.

Due to the dimensions of the vehicles, they are very similar to missiles and, therefore, launching them is a risk. For safety, it is necessary to know with good precision where the fall will be. Therefore, the objective of the research was to develop software that could predict the behavior of rockets, from engine ignition, launch, until reaching its peak and landing. “With the developed code, we got a good accuracy of the rocket’s fall position; we have a good degree to determine the area in which the rocket lands and, thus, guarantee that there is no danger”, says Giovani Ceotto. According to him, in addition to a parachute, which smoothes the landing and prevents them from falling ballistically, what differentiates these rockets from missiles is the scientific purpose given to the flight.

science to heaven
While large rockets take humans into space, smaller ones fulfill the mission of helping researchers to study flight characteristics and more about physics and biology at high altitudes.

According to Ceotto, other groups around the world have already launched experiments to assess how the growth of different bacterial cultures can be affected by the high accelerations of a launch, or by microgravity, a condition of almost zero gravity, which the rocket feels near its apogee .

In other studies, the Jupiter Project carried out experiments related to the control of an inverted pendulum in the area of ​​Dynamics and Control, a chemical experiment based on reverse osmosis and also a weather conditions sounding system, this one developed in partnership with the Federal University of Rio de Janeiro (UFRJ) — account Ceotto.

However, to ensure that the rocket meets the requirements of an experiment — gets the correct acceleration, altitude, and parameters —it is necessary to simulate its trajectory. With that in mind, in addition to the security aspects, the software developed by the team guarantees the mission’s performance.

Forecasting the weather and the behavior of rockets
In addition to variables such as rocket characteristics, aerodynamics and engine behavior, weather conditions also impact the accuracy of the vehicle’s trajectory.

Ceotto explains that one of the meteorological conditions is the wind, its intensity, direction and variation as the rocket rises; others are the temperature, pressure and humidity of the atmosphere. In practice, the most used method to know these variables is, right before the rocket launch, to release a weather balloon: a helium balloon that ascends and collects atmospheric data, and then the data is computed in simulators.

“The limitation is that you can only do this before the flight and we needed, months before, to have a weather forecast of how conditions would be on the day of the launch”, he says. The team’s solution was to add to the software the ability to collect data from international meteorological agencies and process it to generate the information necessary for the safety and quality of the launch.

Project Jupiter and the space race
In the midst of the space race, large well-established companies, such as SpaceX, launch larger rockets, but there are startups that seek to assert themselves in the market. One of the hurdles faced by small businesses that have come late to the fray is mastery of launch technologies. As Ceotto informs, rocket trajectory simulators, in general, are considered secret technologies of governments and large companies.

On the other hand, the software made by the team is open, that is, it is freely available to the public, and any user can make their own contributions. “Currently we have a team of 14 students working intensively on the development of new tools. Users can look for these people, who will provide all the necessary support”, says Fernandes. To access the code, you don’t need extensive knowledge in the area, just go to rocketpy.org and follow the steps described on the page to learn how to use and contribute to the research.

The code was developed in a programming language known by the students over the course of three years and focused on the project’s needs. Part of the data that composes it comes from North American and European projects, in order to compare the simulation with the real launch data. “It is noteworthy the result of an extension group being published in a prestigious magazine. This influences our students to realize that we produce relevant knowledge that is worth sharing with the academic community”, says Giovani Ceotto.

At USP, there is the tripod: teaching, research and extension. Upon entering the University, students are included in the teaching pillar. According to Fernandes, upon joining the Jupiter Project – or any similar group at USP – students begin to practice the extension pillar, and put into practice what they learned through teaching. The research pillar was covered by the group’s students with the published article. “The publication in question sets a new milestone for the Escola Politécnica”, he completes.