i-SAIRAS2020-Papers (2020) 5065.pdf CUBESAT SYSTEM DESIGN FOR MARS EXPLORATORY BALLOON (MEB) Virtual Conference 19–23 October 2020 Tristan Schuler1, Kairav Kukkala1, Virupakshan Vilvanathan1, Jekan Thangavelautham1 1SpaceTReX Laboratory, University of Arizona, USA, E-mail: [email protected] ABSTRACT Exploratory Rovers (MERs) that came before them. Fig. 1 shows the design concept of a MEB, fully de- Aerial vehicles, which have yet to fly on Mars, can ployed and exploring Mars. provide a new method for exploring rugged terrain ar- eas of Mars such as cliff and canyon walls that current From previous research, solar balloons for exploration surface vehicles are not capable of. Solar balloons use on Mars prove to be feasible by using a lightweight solar irradiation from the sun to heat up a lightweight envelope material with high absorptivity and low envelope, which results in heating of the internal am- emissivity to capture radiation from the sun. By in- bient air and generates lift. The Mars Exploratory Bal- cluding a vent, the balloon is also able to control alti- loon (MEB) platform is stowed in a 12U CubeSat and tude. For longitudinal control, the balloon adjusts al- piggybacks on a larger Martian Entry Descent and titude to ride the wind, which is predicted to flow in Landing (EDL) vehicle before initiating its own de- different directions depending on altitude, like Earth. ployment sequence after acquiring a safe separation An ideal area for a solar balloon mission is the north distance. Once deployed, the MEB uses a vent to con- pole during the summer; the balloon can maintain trol altitude and ride different wind patterns to collect buoyancy for weeks at a time due to the extended pe- high quality imagery and meteorological data from the riod of sunlight. Martian atmosphere. The present work gives an over- 2 RELATED WORKS view of the MEB platform, a concept of operations, and an analysis of several major subsystems. To date, exploration of Mars has been limited to sur- face landers, rovers, and reconnaissance orbiters. The 1 INTRODUCTION first interplanetary rotorcraft, the Mars helicopter, will An important unsolved mystery on Mars is the obser- be launching with the Mars 2020 rover to test feasibil- vation of recurring slope lineae (RSL) that have ity as well as perform as a multi-agent system to assist formed at the edge of crater walls, canyons, cliffs, and the rover with path planning [1]. Other aerial vehicles slopes. Another is the seasonal observation of me- that have been proposed for Mars include solar bal- thane near the bottom of canyons and cliff walls. A loons and lighter-than-air aerobots [2][3]. combination of high-res imagery, stratigraphy, and Balloons are not new to interplanetary missions. The core sample return of the Martian rock walls could first interplanetary balloon mission was the Soviet help solve these mysteries. Autonomous aerial vehi- VEGA mission, which had the objective of collecting cles can enable access to high-priority extreme terrain Venusian atmospheric data [4]. The mission was short, science targets on Mars that previous robotic surface but successful, and has inspired proposals for future landers and rovers have been unable to reach. aerobot missions on several planets and moons. One With an extremely thin foldable envelope and need of the most ambitious aerobot proposals is the Titan for a low-mass payload to maintain buoyancy the en- tire solar balloon and its gondolas will easily fit into a 12U CubeSat-deployment package. The 12U CubeSat can then piggyback on a larger Mars mission and de- ploy off a Mars EDL vehicle, eliminating the need for a dedicated heat shield. During descent, the solar bal- loon initiates its own deployment sequence before fully inflating and beginning to explore Mars. The en- velope inflates to around the size of a passenger hot air balloon and carries a primary and venting gondola that occupy a 4U volume that can support up to a 10kg payload. This platform, from a stowed 12U configu- ration, to full inflation has been named, Mars Explor- Figure 1 3D Model of a deployed MEB exploring atory Balloons (MEBs), to pay homage to the Mars Mars i-SAIRAS2020-Papers (2020) 5065.pdf airship explorer which would use a large helium bal- improve these weather and climate models. Wind loon with an integrated propulsion system to explore speed data will also be critical for limited control of Saturn's icy moon [5]. the MEBs. Through venting, the balloons can adjust their altitude to ride different wind currents and NASA proposed and has conducted experiments to use achieve limited horizontal control. Additionally, the solar Montgolfiers for soft landings on Mars. Rather balloons can temporarily land and wait for wind direc- than carrying a lighter-than-air gas, the balloons use tion to change. heated atmospheric air generated from solar irradia- tion to achieve buoyancy [6]. There have also been 4 CONCEPT OF OPERATIONS (CONOPS) several studies and models for vertical controllability Fig. 2 shows a proposed concept of operations for the of solar balloons and high altitude lighter-than-air bal- MEB deployment sequence. The MEB will piggyback loons on both Earth and Mars [7-9]. Lighter-than-Air on a larger Mars EDL vehicle before carrying out its vehicles can also utilize different wind patterns at var- own deployment sequence. The stowed MEB jettisons ious altitudes to adjust their horizontal movement [10- sections of the 12U CubeSat throughout the descent to 12]. reduce weight, eventually resulting in two lightweight 3 MISSION OBJETIVE gondolas connected to the inflated MEB. The MEB's low mass envelope acts as both a parachute and bal- The MEBs have two major mission objectives. The loon throughout the descent and because of its material first objective is to collect high-quality imagery of properties, can achieve buoyancy before making con- hard to reach areas of Mars such as canyon and cliff tact with the Martian surface. walls, as well as rugged terrain areas that rovers cannot explore. A major goal of the MEB platform is to cap- 4.1 Piggyback Mission ture high resolution imagery of Recurring Slope The stowed MEB CubeSat will enter the Martian at- Lineae (RSL), one of the Red Planet’s greatest mys- mosphere on a larger EDL vehicle to avoid the cost of teries. As a low altitude aerial platform, the MEBs can an entire mission as well as eliminate the need for a collect finer detailed imagery than any of the current dedicated EDL vehicle. CubeSat landings for asteroids orbiters. The MEBs can also provide a unique perspec- and the Moon have been proposed, but none have tive that the current surface vehicles on Mars cannot launched at this time [13][14]. Mars introduces the ad- obtain. The MEB will use the onboard cameras for vis- ditional need for a heat shield during reentry to with- ual terrain mapping, visual odometry, and selecting stand the heat from high speed entry into the upper optimal landing sites. Martian atmosphere. Even with the thin atmosphere, a The second major mission objective is to collect at- spacecraft entering Mars will heat up to over 1000 K. mospheric data on Mars to develop better Martian me- The MEB can fit inside of a 12U CubeSat in a stowed teorological models. Currently, atmospheric data col- configuration, so rather than creating an EDL vehicle lection on Mars has been limited to the surface vehi- specifically for the MEB, to minimize size, we suggest cles and the MAVEN spacecraft which collects data piggybacking on the EDL vehicle of a larger Mars on winds in the Martian upper atmosphere. The MEB lander mission. A similar design has been proposed for can collect atmospheric data in a larger 3D area to help an inflatable sailplane that deploys at a high altitude Figure 2 Concept of operations for deployment of a MEB on Mars i-SAIRAS2020-Papers (2020) 5065.pdf on Mars after piggybacking on another mission’s EDL Next, a timed chute deploy will fully release the enve- vehicle. [15]. lope to begin natural ram-injection inflation while fall- ing through the upper atmosphere. Ram-intake bal- After the heat shield of the EDL vehicle is jettisoned, loons dropped from high altitudes have been success- the 12U CubeSat will launch off of the EDL vehicle fully deployed by NASA in a terrestrial setting, includ- using solid rock propellant as shown in Fig. 2. Heat ing with solar balloons [3][17]. shields for previous Mars surface missions have been jettisoned at heights of up to 12 km which would be In the drop tests, the solar balloons failed to inflate the ideal separation height for the stowed CubeSat without a rigid hoop at the mouth opening. Therefore, [16]. From simulations using models of the Martian solar balloons on Mars need a hoop that can be com- atmosphere, Fig. 3 shows that the MEB could achieve pressed to a small volume. The hoop will use either a buoyancy before contacting the ground with a large lightweight shape memory alloy such as NiTiNOL, or enough balloon volume-to-mass ratio as well as pre- a pressurized inflatable hoop. heating of the envelope before being exposed to the 4.3 Multi-Day Flight atmosphere. Heating of the internal air could easily be achieved by using a rapid chemical combustion reac- A solar balloon flying on Mars would be an achieve- tion. If, however the envelope is not preheated, or the ment, but the ideal goal is to have these balloons fly volume-to-mass ratio is too small the MEB would in- for weeks or months at a time.