Aerial Platforms for Exploration Under Extreme Conditions in the Venus Atmosphere

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Introduction Venus exploration programs rely on remote sensing and in-situ approaches, with the latter offering more accurate and reliable scientific data. To facilitate remote and contact exploration, a Venus mission typically comprises two main modules: Orbiter: Operates around Venus to relay data back to Earth. Descent Vehicle: a capsule able to carry scientific payloads and aerial platforms into Venus’ atmosphere. More than 40 Spacecrafts have been sent to Venus, but its extreme conditions (high tempe-ratures, pressures, and clouds of sulfuric acid) limit the operational life of the probes to a few hours. The Soviet Union’s Vega balloons in 1985 demonstrated the scientific potential of aerial plat-forms (APs), providing critical date of over two days at altitudes of 51-54 km, where conditions were moderate. These balloons carried a modest payload of 7 kg, including 1-2 kg of scientific instruments [1-4]. Future aerial platforms with large payloads, longer operational life, and variable operating altitudes could significantly enhance Venus ex-ploration. Such advancements are pivotal for comparative planetology and habitability studies, especially given the discovery of Earth-like exoplanets with Venusian characteristics. Current General Circulation Models (GCMs) fail to fully capture Venus’ atmospheric dynamics, under-scoring the need for improved data acquisition [5]. Increasing the number and diversity of aerial platforms is essential to address these challenges, requiring enhanced payload capacities and inno-vative mission architectures, in particular, aerial platforms, to expand the fields of the fields of study of the planet atmosphere and surface, as well as to obtain updated scientific information about the phenomena studied. 1. Aerial Platforms for Venus Exploration The aerial platforms are designed to operate in the Venusian atmosphere where conditions are Earth-like, collecting data on atmospheric com-ponents and phenomena. This paper classifies these platforms based on altitude and positional control, evaluating them against three key criteria: scientific capability, complexity, and technological readiness. Three primary categories of aerial platforms are discussed: Fixed-Altitude Balloons: Passive platforms that drift with wind currents at a stable altitude. Variable-Altitude Balloons: Platforms capable of adjusting altitude to exploit atmospheric wind patterns for trajectory control. Three-Dimensional Maneuvering Vehicles: Active platforms offering lateral and vertical mobility, including aircraft. 1.1. Fixed-Altitude Balloons High-pressure balloons, such as those used in the Vega project, are ideal for stable operations in Venus’ atmosphere. Despite turbulence-induced fluctuations, these platforms have proven effective for long-duration data collection. The Vega balloons, with a diameter of 3.5 m and a payload capacity of 7 kg, covered 11,000 km over 46 hours (Figure 1) [1; 2; 6-8]. Figure 1. Balloons with variable altitude S o u r c e: by M.Ya Marov, U.T. Huntress [6] Figure 2. Balloon probe with payload of the Vega project S o u r c e: by Glaze et al. [20] Figure 3. Solar powered aircraft S o u r c e: by Glaze et al. [20] 1.2. Variable-Altitude Balloons Variable-altitude systems utilize mechanisms such as helium compression (mechanical or pump-based) to adjust buoyancy. These platforms can leverage vertical wind patterns, such as those identified by Venus Express, to navigate meridional wind currents, enabling controlled latitudinal move-ment (Figure 2) [5; 9; 10]. 1.3. Three-Dimensional Maneuvering Vehicles Fixed-wing aircraft powered by solar panels can fly high in the cloud layer using the intense solar flux on Venus. Instead of “floating” around the planet in the field of super-rotating atmospheric currents, a solar-powered aircraft must remain on the sunlit side of Venus, and this requires flying at speeds approaching 100 m/s, in an easterly direction opposite to the atmospheric flow. Compared to balloons, a solar-powered air-craft has the advantage of precise position control. However, dependence on electric propulsion also has limitations in the latitudes that can be observed. In addition, with existing and planned opportu-nities in the field of energy storage technologies, a solar-powered aircraft will not be able to cross the night side. It is also limited in how deep it can penetrate into the atmosphere, as dense clouds block the sunlight needed to power the device (Figure 3) [5; 10]. Figure 4. Venus Atmospheric Maneuverable Platform (VAMP) - Inflatable airplane S o u r c e: by G. Lee et al. [12] Venus Atmospheric Maneuverable Plat-form - An aircraft-type maneuverable aircraft with the weight of 450 kg, which is capable of independently entering the atmosphere of Venus from a low orbit at a speed, and is designed to survive under conditions of thermal pressure and hypersonic entry. During the flight phase, VAMP will move with minimal energy use at speeds of about 50-70 km/h in the upper and middle layers of the clouds of Venus and collect scientific data for transmission to Earth. VAMP is also quite stable and able to cope with the strong atmospheric winds of Venus, and can orbit the planet for up to a year (Figure 4) [5; 11; 12]. Next, we will examine in detail the related issues to the deployment and activation of aerial platforms (using aerostats as examples) as technical tools for research within the framework of inte-grated missions aimed at studying the atmosphere of Venus. 2. Deployment of Aerial Platforms Descent Vehicles (DVs) serve as carriers and deployment systems for aerial platforms. This paper reviews DV configurations and strategies for releasing balloons in Venus’ atmosphere. In practice, the following types of DVs have been utilized in various missions to explore the planets of the Solar System - Table 1 [1; 7; 16-17]. Designs for integrating aerial platforms within DVs are detailed, including configurations for spherical, conical, and segmental-conical vehicles. Deployment mechanisms for balloons are illustrated, emphasizing reliability during atmospheric entry - Table 2 [2; 7; 18]. Table 1 Types of Descent Modules and Their Characteristics Shape of the DM Description Dimensions Spherical Ensures stability and compact payload arrangements. Conical Accommodates elongated payloads, such as cameras, for high-altitude missions. Segmental-Conical Optimized for aerodynamic efficiency and high-speed atmospheric entry. Venus-D Type Features a sphere-cone shape for enhanced drag and stability. S o u r c e: by V.V. Efanov et al. [21] Table 2 Layout Configurations of DVs with Aerial Platforms Shape of the DM (Descent Modul) Components Spherical-Type DV: 1 - Aerostat Probe (AP 1) 2 - Aerostat Probe (AP 2) 3 - Gliding Probe (GP) 4 - Service and Scientific Equipment Compartment of GP 5 - Drifting Probe / UAV Container 6 - Radar 7 - Landing Probe Conical-Type DV: 1 - Drogue Parachute 2 - Braking Parachute 3 - Descent Module 4 - Truss 5 - Communication Antenna with Orbital Module 6 - Main Parachute 7 - Aerostat Envelope 8 - Aerostat Envelope Inflation System 9 - Aerostat Gondola 10 - Aerostat Guide Rope 11 - Aerodynamic Shield 12 - Second Aerostat Segmented-Conical-Type DV: 1 - Parachute Container 2 - Aerostat Power Cone, containing the aerostat probe envelope 3 - Instruments 4 - Fore Screen 5 - Delta-V in the entry from orbit Venera-D" Type DV 1 - Fore Screen 2 - Envelope 3 - Landing Module 4 - Parachute Container 5 - Aerostat Power Cone No. 1, containing the aerostat probe envelope 6 - Aerostat No. 2 7 - Aerostat No. 3 S o u r c e: by V.V. Efanov et al. [21] The deployment of aerostats in the atmosphere of Venus occurs following the descent module’s entry into the atmosphere during its descent phase. The configurations for the spherical and segmented-conical descent modules are illustrated in Figures 5, 6. Figure 5. Commissioning of balloons in the atmosphere of Venus from a spherical descent vehicle S o u r c e: by V.V. Efanov et al. [21] Figure 6. Commissioning of balloons in the atmosphere of Venus from a segmental-conical descent vehicle S o u r c e: by V.V. Efanov et al. [21] Table 3 Drag coefficient and application of different parachute parameters Type Drag coefficient General application (Mach number, M) Conical 0.75-0.90 Airdrop (M < 0.5M < 0.5M < 0.5) Biconical 0.75-0.92 Airdrop (M < 0.5M < 0.5M < 0.5) Disk-gap-band 0.52-0.58 Airdrop (M < 0.5M < 0.5M < 0.5) Ring-slot 0.56-0.65 Extraction deceleration (0.1 < M < 0.50.1 < M < 0.50.1< M <0.5) Ribbon 0.30-0.46 Supersonic deceleration (1 < M < 31 < M < 31 <M < 3) Conical ribbon 0.50-0.55 Airdrop, deceleration (1 < M < 31 < M < 31 < M < 3) S o u r c e: by S.C.G. Torres, V.A. Vorontsov [19] 3. Modeling the Motion of a Descent Vehicle in Venus’ Atmosphere The motion of a descent vehicle (DV), con-sisting of aerostats in Venus’ atmosphere is analyzed using the example of a spherical-type DV. The process can be divided into the following stages[7] [7]. 3.1. Stage One: Ballistic Motion of the DV in the Atmosphere During this stage, the vehicle’s velocity changes according to the laws of motion for a body falling through the air without a parachute (aero-dynamic deceleration), transitioning from the second cosmic velocity to a near-sonic speed. The equations of motion for the DV can be simplified and expressed as follows: (1) where V - vehicle flight velocity, m/s; θ - trajectory inclination angle relative to the local horizon (angle between velocity vector and local horizontal plane), rad/deg.; H - altitude above the planet’s surface, m; L - distance, m; Rv - average planetary radius (for Venus, Rv = 6051.8 km); ρ - undisturbed flow density, kg/m³; g - gravitational acceleration at the DV’s location, m/s²; Px - ballistic parameter, kg/m². 3.2. Stage Two: Deployment of a Deceleration Parachute and Descent Using the Deceleration Parachute Until the Main Parachute is Deployed The drag coefficient of the parachute depends on the canopy design, fabric type, permeability, flight speed, etc. Table 3 presents drag coefficient values for various parachute canopy types [19]. 3.3. Stage Three: Separation of the Deceleration Parachute, Detachment of the Upper Hemispherical Heat Shield Containing Two Aerostats Subsequently, the upper hemisphere descends on a parachute, followed by activation of the aero-stats. For this stage, the equations of motion can be expressed as: (2) where: m - mass of the DV (or its components), kg; Cx - DV drag coefficient (or its components); Sm - characteristic area of the DV; CP - parachute drag coefficient; FP - parachute area; Ca - aerostat drag coefficient; Fa - aerostat area; k - added mass coefficient; U - aerostat shell volume, m³. 3.4. Stage Four: Deployment of the Main Parachute, Descent, and Deceleration in Venus’ Atmosphere The simulation yielded trajectory parameter variation graphs over time (Figures 7-11). Figure 7. Trajectory parameters of a spherical DV during motion in Venus’ atmosphere (Stages 1-4) S o u r c e: by M.V. Quispe Mendoza а b c d Figure 8. Parameters during parachute deployment with variable masses: a - altitude, km; b - trajectory angle, deg; c - overload, units; d - velocity, km/s S o u r c e: by M.V. Quispe Mendoza а b c d Figure 9. Parameters during upper hemisphere detachment: a - altitude, km; b - trajectory angle, deg; c - overload, units; d - velocity, km/s S o u r c e: by M.V. Quispe Mendoza а b c d Figure 10. Parameters during aerostat probe deployment: a - altitude, km; b - trajectory angle, deg; c - overload, units; d - velocity, km/s S o u r c e: by M.V. Quispe Mendoza а b c d Figure 11. Parameters during aerostat parachute deployment: a - altitude, km; b - trajectory angle, deg; c - overload, units; d - velocity, km/s S o u r c e: by M.V. Quispe Mendoza Conclusion This study examines various aerial platforms carrying payloads for the contact and remote investigation of Venus’ atmosphere and surface. The analysis of these platforms demonstrates en-hanced potential for achieving scientific objectives in future missions. Due to the extreme atmospheric conditions of Venus, prolonged contact-based studies are in-feasible, emphasizing the importance of increasing the number of aerial platforms deployed to the planet, which necessitates a higher payload capacity for descent vehicles. Simulation results confirm that trajectory parameters of a spherical descent vehicle with payloads up to 100 kg remain within acceptable limits across all motion stages, enabling the in-tegration of advanced technical systems, such as aerial platforms, into the baseline design.

About the authors

Victor A. Vorontsov

Moscow Aviation Institute (National Research University)

Email: victor-vorontsov@yandex.ru
SPIN-code: 1063-3737
Doctor of Sciences (Techn.), Professor of the Department 601 and 604 4 Volokolamskoe highway, Moscow, 125993, Russian Federation

Michael V. Quispe Mendoza

Moscow Aviation Institute (National Research University)

Author for correspondence.
Email: dixwmichael@gmail.com
ORCID iD: 0009-0000-1833-2562
SPIN-code: 9178-6215

Ph.D Student of the Department 604

4 Volokolamskoe highway, Moscow, 125993, Russian Federation

References

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