Analysis of architectures for the scientific exploration of Enceladus

Abstract

In 2007 a JPL Rapid Mission Architecture (RMA) analysis team identified and evaluated a broad set of mission architecture options for a suite of scientific exploration objectives targeting the Saturnian moon Enceladus. Primary science objectives were largely focused on examination of the driving mechanisms and extent of interactions by the plumes of Enceladus recently discovered by Cassini mission science teams. Investigation of the architectural trade space spanned a wide range of options, from high-energy flybys of Enceladus as a re-instrumented expansion on the Cassini mission, to more complex, multielement combinations of Enceladus orbiters carrying multiple variants of in-situ deployable systems. Trajectory design emerged as a critical element of the mission concepts, enabling challenging missions on Atlas V and Delta IV-Heavy class launch vehicles. Various Enceladus Flagship-class mission concepts identified were analyzed and compared against several first-order figures of merit, including mass, cost, risk, mission timeline, and associated science value with respect to accomplishment of the full set of science objectives. Results are presented for these comparative analyses and the characterization of the explored trade space.

Heatshields for Aerogravity Assist Vehicles Whose Deceleration at Titan Saves Mass for Future Flagship Class Exploration of Enceladus

“…The trajectory has a launch C3 of 16.2 km 2 /s 2 and reaches the Saturnian system in 2043, 10 years after a 2033 launch via multiple gravity assists by Earth and Venus. The C3 provided by a Delta IV Heavy could enable all nine of the Enceladus Missions discussed in [1], while an Atlas V could support a long-lived soft lander (Mission "E") or a low energy plume fly-through Mission "F" [1]. Outbound events are listed in Fig.…”

“…Rendezvous with Enceladus occurs after a gravity-assist tour of Saturn's inner moons. The moon tour can take more than two years and requires up to 500m/s ∆V based on previous analyses [1]. The ∆V (DV) values for flight system insertion into the MT trajectories are specified on Fig.…”

“…These results scope the aerothermal conditions for incoming hyperbolic excess speeds ranging from 7.3 to 14.81 km/s. To be consistent with the notional blunt body and "Mission E" reported in [1], the entry mass for the TRAJ simulations was chosen to be 3,800 kg. For this heatshield feasibility study, the body was assumed to be a simplified 60° sphere-cone with a base diameter of 5 m, a nose radius of 2.315 m (ballistic coeff.…”

“…The AGA maneuver at Titan would be followed by a mass-saving, standard gravity assist, 2.5-year tour of Saturn's inner moons (referred to hereafter as a "moon tour"). That paper demonstrated that Enceladus exploration missions were achievable within the flagship mission cost cap (~$3 B), realistic mass (6,500 kg spacecraft and propulsion stage), and reasonable duration (14 years including the moon tour) [1]. These missions included landers and low energy plume fly-throughs.…”

“…This paper demonstrates that mature materials exist for the heatshield design of Aerogravity Assist (AGA) vehicles that would decelerate in Titan's atmosphere, thereby enabling mass savings required for the exploration of Enceladus. A 2009 paper by T. Spilker et al [1] described flagship class missions for the exploration of Enceladus. That paper identified technologies needed for the missions including autonomous navigation and radioisotope power, as well as challenges such as third body effects by Saturn on Enceladus orbiters.…”