**1. Introduction**

Mars attracted human attention since 1960. To understand the importance of Mars exploration, several reasons should be considered. First, the Red Planet has similar dimensions compared to Earth's continental surfaces. Secondly, it has the capability to host Earth-like ecosystems promoting bacterial life. Furthermore, it represents a prototype sample to study the effects of a probable dramatic climate change [1].

Although the current Martian atmosphere is quite unfeasible for human life, the fundamental component for life i.e., water does exist on Mars around the poles and is probably distributed under the Martian surface. Therefore, a permanent human presence for research purposes on Mars requires reliable and affordable entry vehicles.

Several missions were performed in the past but unfortunately, most of them were unsuccessful [2, 3]. The first attempt to reach Mars was performed by URRS in 1960 with *Marsnik 1*. After several failures just on July 15th, 1965, the NASA *Mariner 4* successfully performed the first Mars flyby. Only in 1976 with *Viking 1* and *2* missions, for the first time, a human device successfully landed on Mars. On 4th July 1997, the first rover, *Pathfinder*, landed on Mars. The purpose of *Pathfinder* was to reduce the costs of space missions. It cost only 5% of *Viking* missions and was developed to test new technologies and approaches for future Mars missions.

During the last decades, significant technological advances have been done. NASA *Pathfinder* successors, *Spirit* and *Opportunity*, provided more than 100,000 images. Currently, three NASA rovers are active on the Martian surface: *InSight, Curiosity*, and *Perseverance*. *InSight* is currently devoted to study the planet's interior; while *Curiosity*, launched in 2012, is still operating on the Gale crater. Finally, Perseverance is the rover of the Mars 2020 mission, and its work objective is to look for signs of ancient life and collect rock and soil samples for a possible return to Earth (i.e., Mars sample return missions) [2]. This mission has the additional record of having allowed a small helicopter, namely Ingenuity, to fly to Mars for the first time in history.

All current Martian devices are unmanned [2]. However, for the upcoming Martian manned missions, recent studies have shown the limited possibility to adopt aeroshells for Mars landing. Braun and Manning [3] highlighted that without a lifting entry, Mars exploration with manned missions can result unfeasible because of the high g-loads associated with hypersonic deceleration and the touchdown.

In this work, a preliminary feasibility analysis of a Martian entry, performed with a lifting body having a blended double delta-wing, is performed. As no previous experience is gained on the use of lifting bodies for Mars entry, a conceptual configuration for an Earth re-entry mission from LEO is preliminarily assumed. A three degree of freedom (dof) trajectory model with a standard Mars atmosphere is adopted to address the entry and descent flight. A simplified heat transfer analysis based on the radiative equilibrium hypothesis for the wall of the descent spacecraft is also performed to compute heat loads during entry. The feedback on a trajectory, obtained by varying AoA and bank angle considering aerodynamic efficiency, and the capability to reach a predefined landing spot is discussed. The possibility to perform a lower deceleration within a shallower entry angle, taking full advantage of the Mars atmosphere is considered.

## **2. Lifting entry in Martian atmosphere**

In 2007 NASA developed a standard design for a reference vehicle architecture for human Mars entry descent and landing (EDL) [4]. It consisted of a hypersonic aero assist entry system with a mid (0.6–0.8) Lift-to-Drag ratio (L/D) aeroshell, able to perform the aerobraking maneuver, that is ejected at a low supersonic Mach number. The use of hypersonic inflatable aerodynamic decelerators (HIADs) is also deeply studied to deliver human-class payloads to the surface of Mars [5]. However, inflatable decelerators do not provide sufficiently low terminal speed adequate for a safe manned landing [6, 7].

Recent studies highlighted the necessity to adopt a different vehicle design for manned missions [2]. A decisive design criterion is represented by the altitude at which the vehicle reaches a subsonic speed. Therefore, lifting body architectures having higher aerodynamic efficiency compared to aeroshells, are currently investigated for a high lift EDL mission [8, 9].

Specifically, lifting bodies (like Dream Chaser) allows a more favorable aerothermal environment and can customize the landing spot using bank angle modulation [10]. Control authority is also important for Mars explorations because it opens the possibility of using a lightweight Thermal Protection System (TPS). Besides, heat load can be controlled with drag (i.e., AoA) modulation which varies the ballistic coefficient during the entry phase according to a prescribed guidance law. Therefore, unlike capsules, a lifting body can take advantage of the
