As part of Purdue University's Introduction to Aerospace Design course, (course code "AAE 25100") me and a group of three other students were tasked with designing a Mars sample retrieval mission involving selecting a viable launch vehicle and launch date while also calculating important astrodynamic mission parameters such as ΔV, mission duration, and stage masses. Our hypothetical spacecraft was intended to transport a lander that could retrieve samples from the Perseverance rover on the surface of Mars.
During this project, I was largely in charge of handling calculations in MATLAB and then communicating their mathematical basis in our 72-page design report. By utilizing the patched conics
method, we found that it would take a ΔV of 3.55 km/s to leave Earth's orbit entirely after using 8.80 km/s of ΔV to get to low Earth orbit assuming we launch from Kourou for maximum gravity assist.
After that point, we estimated that entering a Mars capture orbit would take 0.85 km/s of ΔV. Once the samples are retrieved from the Perseverance rover by our lander module, the lander would need to burn 3.54 km/s of ΔV to return to
low Mars orbit and rendezvous with the orbiter module. To depart from Mars and back towards Earth, the spacecraft would need 2.11 km/s of ΔV. At the end of the mission, we approximated the re-entry velocity of the spacecraft into Earth's orbit
to be around 11.07 km/s, although the Earth re-entry was beyond the scope of this project.
By using the period of the Earth-Sun and Mars-Sun orbits, the semimajor axes of the orbits, and the gravitational parameter of the Sun, we can calculate the transfer period, synodic period, and two backup dates for the mission's start.
The estimated timeline of this designed mission would be to have the mission begin on January 16, 2025. 683 days later, on November 29, 2026, the spacecraft would depart Earth towards Mars, and would not arrive for
another 258 days on August 15, 2027. After the sample retrieval is successful, the spacecraft can depart Mars on November 12, 2028, or 454 days after arrival. The spacecraft would finally arrive back at Earth on April 14, 2030
after 517 days of travel from Mars. Overall, the mission would take 1914 days, or 5 years, 2 months, 4 weeks, and 1 day.
The spacecraft, excluding the launch vehicle used to transport it to low Earth orbit, was estimated to have a gross lift-off weight of 10738.05 kg. Meanwhile, the orbiter's mass upon arrival into the Mars capture orbit
had a mass of 4066.65 kg. Then, upon departure from Mars, the orbiter would only have a mass of 2350.13 kg. The lander module used to retrieve samples from the Perserverance rover would need to have a mass not exceeding
135.68 kg.
Me and my teammates' efforts won us the
Northrop Grumman S.P.A.C.E. Award in 2024
for having the most clearly communicated rocket design among all students in the Introduction to Aerospace Design course.
One key mission design choice that was unique to our solution, as highlighted by Northrop fellow Dave McGrath,
was our decision to entirely shed our Mars lander's entry, descent, and landing (EDL) gear upon ascending from the surface of Mars. This decision originated from the struggle to find
a viable rocket engine to fit within our Mars ascent vehicle that would provide enough ΔV to ascend back to the orbiting vehicle. By shedding the EDL gear, we effectively
reduced the weight of the Mars ascent vehicle which relaxed our criteria for possible engines to use in it.