The technology of Unmanned Aerial Vehicles (UAVs) has tremendous potential to support various successful space mission solutions. In general, different techniques for observing space objects are available, such as telescopes, probes, and flying spacecraft, orbiters, landers, and rovers. However, a detailed analysis has been carried out due to the benefits of UAVs relative to other planetary exploration techniques. A prototype UAV has been successfully simulated to fly on Mars’ surface.
1. Introduction
Space exploration is the largest and most influential example of many kinds of convergence. It brings many technological areas together: propulsion, life sciences, materials, guidance, and in order to maintain the endeavour, space exploration is an example of several kinds of integration, power, communication, and a host of others
[1].
Progress in recent technologies has enabled UAVs to be considered valuable platforms for planetary exploration
[2]. UAVs have had extremely high progress to be applied for space missions
[3]. However, the applied methods for planetary exploration have limited mobility and low resolution and provide limited information about the planet. We have been motivated to use UAVs for space exploration to resolve these issues. In other words, we can say that UAVs can overcome the planetary measurement gap. Exploiting space through UAVs will have many benefits. UAVs can provide real-time services at the edge of the network
[4]. UAVs can map a large area of the planetary body and gather data from smart environments
[5]. Moreover, they have better resolution compared to the satellites and orbiters used till now. Since UAVs are remote-controlled spacecraft, they can have sufficient station time
[6].
2. Mars Exploration through Different Methods/Vehicles
The use of UAVs for planetary exploration may have many advantages, particularly that a UAV can map a wider area than a rover at a resolution far more significant than that provided by current satellites or orbiters
[7]. The overall details of the Venus, Mars, Titan, and Earths’ moon’s atmospheric conditions, characteristics, and configurations of the UAV flights are described below.
2.1. Mars UAVs
Mars, relative to Earth, has a low density; the concept of UAVs that can fly on this planet has gained a lot of interest due to the importance of Mars science [8].
Several studies by NASA, universities, and industry were carried out from the 1980s to the 1990s to identify new Mars atmosphere missions and design various types of Mars UAVs [9]. Article [9] patterned the construction of Mars aircraft, designated as the Argo VII. The Argo VII’s aerodynamic, stability, and control parameters were calculated using analytical and control parameters similar to that of ARES-2. Progress in technical areas, such as propulsion technology, composites, and energy storage systems, has led to more complex Mars UAVs. In article [10], as an affordable means of launching small planetary exploration payloads, the NASA Jet Propulsion Laboratory developed the Micro-Mission concept in 1999. The ASAP of the Ariane 5 launch vehicle was used to launch a spacecraft weighing 200 kg into a geosynchronous transfer orbit. Numerous universities have performed a study on Mars aerial vehicles since 2000, such as the University of Colorado at Boulder and Wichita State University. The MAP project was the subject of researchers from the University of Colorado at Boulder [11]. In article [11], as the design project priority, the MARV team chose to deploy the wings of the MAP. The project for MARV was split into four stages: initial design, deployment system, machining and fabrication of components, and step of integration and checking. The final aim of the project was to plan for the MAP with the wing packaging and wing launch. The outcome was a fully deployable wing with the associated actuator, microprocessor, and supporting applications. The secondary purpose of the deployable wing was to perform wind tunnel testing of the durability of its pitch. For the MAP, a full software architecture design was also built along with all the related electrical components required to incorporate the aerospace. In [12], the research explains the design and development of different autopilot device architectures for unmanned aerial mini/micro rotary-wing vehicles via the model-based design approach.
2.2. Designing Mars UAV
The Mars UAV is based on a vehicle system; however, it has been adapted to match the thrust requirements of Mars’ thin atmosphere. The Mars UAV system was created to create a model that could resist Mars conditions, such as dust storms and temperature shifts during night and day. When the UAV is expected to fly out of sight of the operator or to perform complex manoeuvres for which the control response from manual operation is insufficient, autonomy is required. The benefits of Mars UAV systems over helicopter vehicles motivated the development of the Mars UAV. When performing manoeuvres, the helicopter requires a complicated system to regulate the pitch of the rotors. On the other hand, UAVs can change their orientation simply by changing the rotor speeds. All three movements, roll, pitch, and yaw, may be accomplished simply by delivering appropriate signals to the motors to alter rotor speeds without any mechanisms or mechanical control. The negative of the Mars UAV system is that huge rotors require a significant amount of actuation effort to accelerate up or slow down, resulting in a delayed reaction time. The variable pitch is employed for very large rotors because motors cannot rapidly accelerate up or down.
The idea of flying UAVs on Mars is to show that with significant rotor blade design optimisation, enough lift can be created to fly a lightweight UAV in the thin atmosphere. The design also emphasises making the flight and operation autonomous and mapping the surrounding terrain and path planning to help the ground-based rover go beyond its existing capabilities. The Mars UAV will be used in high tip Mach numbers and low Reynolds numbers. To minimise the development of unwanted shock waves, it is critical to maintain subsonic speed at the rotor’s tip in a generic rotor design.
If not anticipated beforehand, the produced shock waves significantly impact the rover’s lift-generating capabilities. Because the air density on Mars is so low, rotating the rotor is greater while keeping the tip speeds subsonic is advantageous. The vehicle’s hovering will be controlled in the same way any UAV flying under Earth settings. The suggested controller, specifically developed to manage the co-axial rotors, will handle the roll, pitch, and yaw movement instructions. The lower gravity value will assist the vehicle in remaining stable while flying and prevent tiny instabilities produced by unstable phugoids
[13]. The suggested rotor blade size is 1.12 m, and when placed co-axially, two rotors spin in opposing directions.
The entire mass of the UAV is estimated to be roughly 6 kg
[14]. In the CAD modelling section of this project, parts of the onboard payload and system requirements will be explored. A radioisotope thermoelectric generator is now used to power Mars rovers. However, radioisotope thermoelectric generators have poor efficiency, and it is not suited for UAVs due to the hefty subsystem necessary to regulate the heat created. The Mars UAV is meant to run entirely on solar power. The Mars UAV’s longer arms help mount roll-out solar arrays. These solar panels may be extended for charging and retracted for flight. Flight data from the Ingenuity helicopter project will assist in determining whether or not a powered fight is conceivable in Mars’ atmosphere and how to pursue this notion in terms of boosting payload mass while lowering system mass
[15]. For more details, the design of UAV for Mars exploration is discussed in detail in
[14][16][17].
2.3. Previous Major Devastating Failed Missions in Space Exploration
Various approaches used earlier for planetary exploration have many limitations. Landers are limited to the landing site’s surrounding area and can only explore appropriate terrain. For example, the range reported by the JPL for the MER is a total distance of 1 Km, whereas a Mars UAV can potentially explore 500 Km
[18]. Since landers may have minimal (or no) freedom to walk around freely, they have only had a single, one-time body experience. In sterile conditions, certain landers, such as Huygens on Titan or Mars landers, must be designed to prevent Earth contamination
[19]. Rovers have some benefits over stationary landers, as they examine more territory and lead to exciting features. However, the greater likelihood of loss, owing to landing and other threats, is the downside of rovers relative to orbiters and that they are limited to a restricted area around a landing site that is only roughly expected. Moreover, owing to the contact time delay between Earth and other planetary bodies, travelling safely from rock to rock or position to location is a big challenge. The rover drivers on the spatial body cannot immediately see what is happening to a rover at any given moment, unlike a remote-controlled vehicle, and they could not send fast instructions to prevent the rover from crashing into a rock or falling down a cliff
[20]. From the Yutu (from 2013–2016) and the Opportunity (2004–2018), the rovers have just been able to drive up-to-the-distance of 0.1 and 45.16 km, respectively
[21].
Table 1 discusses some of the major previously failed missions for planetary exploration.
Table 1. Discussion table on previously failed missions.
Reference |
Mission |
Lander |
Orbiter |
Rover |
Human Crew |
Cause of Failure |
[21] |
MCO |
✕ |
✓ |
✕ |
✕ |
Cost constraint. |
[22] |
Chandrayaan-2 |
✓ |
✓ |
✓ |
✕ |
500 m short of the lunar surface, Vikram Lander lost control and crashed with the Pragyan rover. |
[23][24] |
Columbia Space Shuttle |
✕ |
✓ |
✕ |
✓ |
Damage in the left-wing. |
[25] |
Viking project |
✓ |
✓ |
✕ |
✕ |
Software updates error. |
[26][27] |
DART project |
✕ |
✓ |
✕ |
✕ |
Wrong estimation of distance through the computer. |
[28]. |
MPL |
✓ |
✕ |
✕ |
✕ |
Faulty transmitter. |
[28] |
NOAH 19 |
✕ |
✓ |
✕ |
✕ |
Mechanical malfunctioning. |
This entry is adapted from the peer-reviewed paper 10.3390/drones6010004