AN OVERVIEW OF AERIAL APPROACHES TO EXPLORING SCIENTIFIC REGIONS AT TITAN M.Pauken1, J. L. Hall1, L. Matthies1, M. Malaska1, J. A. Cutts1, P. Tokumaru2, B. Goldman3 and M. De Jong4 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA; 2AeroVironment Inc., Monrovia, CA 3Global Aerospace, Monrovia CA, 4Thin Red Line Aerospace, Chilliwack, BC

Scientific Motivations Aerial Platforms for Scientific Exploration • Titan has a rich and abundant supply of organic molecules and a hydrology cycle based on cryogenic hydrocarbons. Titan • Aerial platforms are ideal for performing initial environments include organic, dunes, plains, and hydrocarbon lakes and seas. reconnaissance of such locations by remote sensing • Titan may have had near-surface liquid water from impact melt pools and possible cryovolcanic outflows that may have mixed with and following it up with in situ analysis. surface organics to create biologically interesting molecules such as amino acids. • The concept of exploring at Titan with aerial vehicles • These environments present unique and important locations for investigating prebiotic chemistry, and potentially, the first steps dates back to the 1970s [2]. towards life. • NASA initiated studies of Titan balloon missions in • When the Huygens Probe descended through Titan’s atmosphere it determined the atmosphere was clear enough to permit imaging the early 1980s [3]. of the surface from 40-km altitude and had a rich variety of geological features. Winds were light and diurnal changes were minimal • JPL conducted studies and technology development which are ideal for aerial platforms. in the 1990s and early 2000s [4]. • These observations affirmed that aerial vehicles could to play a key role in future exploration of Titan for 1) remote sensing, since many orbital signatures are obscured by the dense atmosphere, 2) mobility, since the lakes and dunes that covered many areas of • The Cassini-Huygens mission arrival at Saturn in 2004 Titan of would present hazards to surface vehicles and 3) surface sampling through controlled flight near the surface [1]. gave new impetus to aerial exploration of Titan.

Lighter Than Air (LTA) Concepts TSSM Montgolfiere Balloon • NASA and ESA jointly developed a concept for a Titan Saturn System Mission (TSSM) in 2008 with a 10.5-m diameter Montgolfiere balloon that would fly 8 to 10-km above the surface and carry a 144-kg gondola that included 25 kg for the science payload. The Montgolfiere balloon as part • Altitude control could be provided by heating of ambient gas with radioisotope power of the TSSM mission concept source (RPS) waste heat [5]. study • TSSM competed with a concept for a Europa (NASA) and Ganymede (ESA) mission that was selected on the basis of technical maturity in Feb 2009. • A joint CNES JPL technical effort on balloon development continued addressing issues of buoyancy stability and control and deployment. • A Montgolfiere balloon using RPS waste heat could float for many years at Titan because it is vented to the atmosphere making it insensitive to leaks from pin-hole defects.

Helium Balloons • The Titan Aerial Explorer [6] proposal concept featured a 4.6-m diameter helium balloon A multi-segmented helium balloon flying at 8-km altitude with a total floating mass of 170 kg including 19 kg for science concept for altitude control instruments. • Altitude control of helium balloons was shown to be feasible with modest amounts of energy by either pumped compression or mechanical compression [7]. • A mechanical compression altitude control balloon concept has segments that are compressed by shortening a tether that runs down the axis of the balloon. Release of the tether allows the balloon to rapidly ascend. • Life-limiting diffusion of helium through balloon envelopes at Titan temperatures was shown to be reduced by 4 orders of magnitude from that at Earth ambient [8]. Titan glider concept that requires Buoyant Winged Gliders little power to fly or maneuver • A buoyant gas filled wing concept uses no power to stay afloat. It could be capable of changing altitude and perform short duration station keeping for surface sample collection. • A small amount of power could propel it forward by shifting compressed atmospheric gas between forward and aft ballonets. • It could “swim” through the air by making sequential ascents and descents. It could turn while ascending or descending by filling ballonets located at the wing tips.

Heavier Than Air (HTA) Concepts Fixed Wing Vehicles • Concepts for fixed wing aircraft on Titan have been developed by Lemke [9]. Despite the The AVIATR Titan airplane poor specific power of radioisotope power sources, Titan’s low gravity could make it practical mission concept to achieve sustained flight. The AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance [10] involved a study to fully explore the capabilities of a fixed wing aircraft. • A disadvantage of the fixed wing aircraft is that electrical power must be subdivided between the needs of staying aloft and propulsion. AVIATR addresses this by a novel ‘gravity Copyright 2014 Mike Malaska battery’ climb-then-glide strategy to store energy for optimal use during telecommunications sessions. AVIATR cannot descend to the surface for sampling.

Rotorcraft • The dramatic expansion of drones capable of controlled descent has spurred interest in applying the same concept at the planets. A Mars Helicopter drone is under development at Titan rotorcraft concept flying JPL is being considered by NASA for flight on the Mars 2020 mission. over a lake before returning to • Rotorcraft are feasible at Titan and offer simpler mechanical and control system designs [11]. its base to recharge its battery • Like the Mars Helicopter, this would be powered by a rechargeable battery which permits only short flights of the order of an hour before recharging.

Aerial Platform and Planetary Science Vision 2050 References: • As NASA formulates a plan for Planetary Science Vision 2050, aerial platforms at Titan could [1] Cutts, J.A., Hall, J.L., and Kolawa, E., IPPW-5, 2007 play a key role. [2] Blamont, J., in Hunten and Morrison (eds), The Saturn System, NASA Conference Publication 2068, 1978 [3] Friedlander, A.L., JBIS, 37, pp.381-387, 1984 • Both LTA and HTA concepts are practical and could offer unique contributions to exploration [4] Jones, J. A., and Heun, M. K., “AIAA, Paper No. 97-1445, 1997 of this fascinating world. They bring the unique ability to perform synoptic coverage from [5] Reh,K., IPPW-010 altitude and in situ measurement when they descend to the surface. [6] Hall, J., IPPW-8. 2011 • Aerial platform would perform a large part of the role that both orbiters and rovers have [7] De Jong, M. and Cutts, J.A. , IPPW-12, 2015 [8] Pauken, M. and Hall, J.L., IPPW-11, 2014 served at Mars. When the time comes for sample return aerial platforms could perform the [9] Lemke, L.G., IPPW-7, 2008 critical role of lifting samples from the surface to a high enough altitude from which they can [10] Barnes, J., AVIATR plane report. Exp Astron (2012) 33:55–127 DOI 10.1007/s10686-011-9275-9 be injected into space. [11] Matthies, L.H, Tokumaru, P., and Sherritt, S., IPPW-11, 2014 • Planetary Science Vision 2050 must include a strategy for aerial platforms at Titan.

Pre-decisional information – for planning and discussion purposes only. Copyright 2017 California Institute of Technology. U.S. Government sponsorship acknowledged.