ExoMars alternative escape trajectories with Soyuz/Fregat.

Area of Science:

• Planetary Science
• Astrodynamics
• Space Mission Design

Background:

• The ExoMars mission aims to orbit Mars and land a rover to search for signs of life.
• Initial feasibility studies revealed a very small mass margin for the orbiter in a direct transfer scenario using Soyuz/Fregat.
• This constraint necessitates exploring alternative trajectory designs to accommodate higher orbiter masses.

Purpose of the Study:

• To investigate alternative interplanetary trajectories for the ExoMars mission.
• To enhance the mass margin for the orbiter by utilizing lunar swing-bys and the Sun's gravity gradient.
• To identify feasible trajectory designs that meet mission requirements for Mars arrival.

Main Methods:

• Utilized WESBOT, a GMV tool, for designing Weak Stability Boundary (WSB) transfers to the Moon and Earth escape trajectories.
• Analyzed trajectories involving multiple lunar and Earth swing-bys, leveraging the Sun's gravity gradient for DeltaV savings.
• Employed a systematic search for initial guess trajectories, combining patched conics and multiple shooting methods.
• Optimized departure conditions (date and orbit) while maintaining the required Mars arrival date.

Main Results:

• Identified and presented optimal trajectories with varying morphologies for different swing-by strategies.
• Demonstrated the potential for significant mass gains through the strategic use of gravity assists.
• The analysis confirmed the applicability of these novel trajectory designs to the ExoMars mission.

Conclusions:

• Combined lunar swing-bys and Sun gravity gradient maneuvers offer a viable solution for increasing orbiter mass on Mars transfer trajectories.
• These advanced trajectory design techniques are crucial for overcoming mass limitations in interplanetary missions like ExoMars.
• The study provides a foundation for future mission planning requiring enhanced payload capacity.