Overview

This was a 300-level project for AERE 351 at Iowa State University, where our team—Carter, Seth, and I—designed a Mars transfer mission to replace a malfunctioning spacecraft. The goal was to create an efficient interplanetary trajectory that launched on June 5, 2004, and arrived at Mars on May 14, 2005, while minimizing total ∆V (change in velocity) to save fuel. 

We explored multiple maneuver strategies, including two-impulse, three-impulse, and a Venus gravity-assist flyby. Tools like MATLAB, Python, ANSYS, and STK were used to model trajectories, run calculations, and visualize orbital transfers. 

This project gave us hands-on experience with mission planning, impulse maneuver design, and comparing different orbital paths based on performance. It also improved our coding skills and helped us become more confident working with industry-relevant software tools.

Maneuver Approaches

For this mission, we explored and compared three different transfer strategies to get from Earth to Mars. Each approach had its own trade-offs in terms of fuel use, timing, and complexity. You can see a visual of each trajectory below, along with a few rough numbers or advantages listed under each one. 

These were the three maneuvers we analyzed:

• Two-Impulse Transfer
  A straightforward approach with just a departure and arrival burn.
  
  

• Three-Impulse Transfer
  Adds a mid-course correction for more control over timing and arrival conditions.
  
  

• Two-Impulse with Venus Flyby
  Uses Venus to slingshot the spacecraft toward Mars, helping save fuel without an extra burn.
  
  

These different paths were modeled using MATLAB and visualized in STK to better understand their performance and feasibility. (see images below)

Challenges and Solutions

We ran into a handful of technical and learning challenges throughout the project, each pushing us to dig deeper and improve how we worked:

• Switching from Python to MATLAB
  We started out using Python and Skyfield for initial modeling, but eventually made the switch to MATLAB. It gave us more flexibility and better documentation for orbital mechanics problems. It also made it easier to fine-tune Lambert transfers and work with matrices as our calculations got more involved.
  
  

• STK Orbit Issues
  When we moved our solutions into STK, we noticed some of the orbits were flipped or didn’t match our expectations. This ended up being an issue with how we were handling Lambert arc parameters and reference frames. After some trial and error, we figured out how to manually adjust the inputs to match what STK expected.
  
  

• Flyby Errors
  Our first attempt at modeling a Venus flyby actually resulted in a crash into the planet. We misunderstood the way gravity assists should be targeted. After checking back with course notes and asking the TAs for help, we reworked the trajectory to take advantage of the flyby without hitting Venus.
  
  

• Learning STK
  STK was a powerful tool, but it took time to get used to. Figuring out how to model multiple maneuvers, use the right time windows, and visualize things properly took a lot of experimenting. By the end, we were able to create a full simulation showing all three trajectories clearly.
  
  

Each problem we ran into helped us better understand both the tools and the physics. The process of solving these issues gave us a stronger grasp of interplanetary mission planning and what it takes to make a design actually work.

Results and Summary

Our analysis compared three different interplanetary transfer strategies: a two-impulse direct transfer, a three-impulse maneuver, and a two-impulse maneuver with a gravity assist flyby around Venus. The primary goal was to minimize total mission ∆V (change in velocity), which directly correlates to required fuel.

• Two-Impulse Transfer
  
  

  • Departure ∆V: ~3.67 km/s
    
    

  • Arrival ∆V: ~5.20 km/s
    
    

  • Total ∆V: ~8.87 km/s
    
    

  • Straightforward trajectory but relatively inefficient in fuel usage.
    
    

• Three-Impulse Transfer
  
  

  • Departure ∆V: ~4.60 km/s
    
    

  • Mid-course Correction at Venus: ~3.86 km/s
    
    

  • Arrival ∆V: ~6.13 km/s
    
    

  • Total ∆V: ~14.59 km/s
    
    

  • While flexible, this approach was less fuel-efficient overall due to the high mid-course correction.
    
    

• Two-Impulse Transfer with Venus Flyby
  
  

  • Earth Departure ∆V: ~3.67 km/s
    
    

  • Mars Arrival ∆V: ~5.20 km/s
    
    

  • Venus flyby provided an effective ∆V boost of ~3.86 km/s without expending fuel
    
    

  • Total ∆V (actual burn): ~8.87 km/s, but with significant trajectory shaping due to the flyby
    
    

  • Best overall solution in terms of fuel efficiency and mission feasibility
    
    

All three trajectories were modeled and animated in Systems Tool Kit (STK) for visualization, allowing us to evaluate orbital paths, encounter windows, and trajectory timing. The results from our custom MATLAB Lambert solver were cross-checked against STK outputs to ensure consistency between numerical and simulated solutions.

Want More Data? 

If you're curious about the full trajectory analysis, code methods, or STK visualizations, you can download and read our complete final report below. It covers all the maneuver strategies we explored, our numerical results, and how we arrived at the final mission design.