submitted to this conference. Note that nominal trajectories with ﬂight times less than 13 years are difﬁcult to achieve with propulsive insertion,3and hence aerocapture allows a 5 year reduction in ﬂight time to Neptune. Preliminary results indicate the high arrival V1of 20 km/s enables the use of a heritage blunt body aeroshell with L=D = 0.4, and is within the capability of existing TPS materials. Further study is on-going to investigate if the L=D requirement can be reduced to 0.24 to enable use of an MSL- derived aeroshell for Neptune aerocapture. The statistical performance metrics from Monte Carlo simulations (such as percentage of cases captured successfully, apoapsis dispersion etc.) shown in Fig. 5 must be assessed and compared to the preliminary estimates used earlier. If the vehicle performance is satisfactory (in a statistical sense i.e. the probability of mission critical failure such as accidental escape is sufﬁciently low) the mission concept can proceed to the next step of more detailed system analysis. If not, it is necessary to identify the cause of the failures and adjust the interplanetary trajectory, vehicle design, and guidance scheme to ensure acceptable performance. Athul Pradeepkumar Girija et al. “Aerocapture Performance Analysis for a Neptune Mission Using a Heritage Blunt- Body Aeroshell”, AAS 19-815, 2019 AAS/AIAA Astrodynamics Specialist Conference, Portland, ME. 9 200 250 300 350 400 450 Apoapsis altitude x 103, km0100200300400500600Number of cases98.8% 350 300 250 200 150 100 Periapsis altitude, km200250300350400450Apoapsis altitude x 103, km #3585Figure 5. Representative aerocapture vehicle performance analysis results from Monte Carlo simulations for a vehicle with L=D = 0.4 entering Neptune atmosphere at 30.5 km/s. Target apoapsis alt. = 400,000 km. (Left) Histogram of apoapsis alti- tude achieved. 100% of the cases captured successfully in this simulation i.e. no cases resulted in atmospheric burnup or escape. (Right) Apoapsis vs. periapsis altitude at atmospheric exit. Refer to the companion paper* for more details. Subsystem Design, Cost and Risk Assessment The ﬁnal step in the proposed framework is the incorporation of power systems, instruments, command and data handling, propulsion, aeroshell conﬁguration and structure, thermal protection system (TPS), spacecraft design and packaging inside the aeroshell, telecom and thermal manage- ment. This step is suitable for a NASA concurrent engineering design lab such as Team X8for a high ﬁdelity mission concept study. Subsystem level analysis may be required for aerothermal predictions and TPS sizing for which the expertise specialized research groups and facilities and NASA Ames Research Center can be leveraged. A major limitation of the previous high ﬁdelity aerocapture systems analysis studies4–6is that a cost and risk assessment is lacking. The lack of cost and risk assessment could be attributed to the fact that these were among the ﬁrst ever detailed aerocapture systems studies and the schedule and time constraints limited the investigations that could be performed. In the proposed framework, once the system deﬁnition reaches an acceptable level, a cost estimate (based on parametric mod- els, historical data etc.) is performed. Such an estimate is difﬁcult to perform at the level of the present paper, and hence is not performed for a Neptune aerocapture mission. However, the study emphasizes the importance of being able to provide a reliable cost estimate for any future aerocap- ture mission concept study. The science return should be commensurate with the mission cost, and should allow ample margins for cost growth and options for descopes if required. Despite acknowledging the signiﬁcant performance beneﬁt offered by aerocapture for outer planet missions, the concern of the risks associated with aerocapture is clearly visible in the literature. The Decadal survey remarks,“Further risk reduction will be required before high value and highly visible 10 missions will be allowed to utilize aerocapture techniques.” There are very few studies which has investigated quantitatively the nature and magnitude of risks associated with aerocapture. Studies over several decades have shown that the technical risks associated with aerocapture can be miti- gated, for example many of the technologies a future aerocapture vehicle would use such as guided hypersonic ﬂight has been demonstrated by Apollo and Mars Science Laboratory (MSL).12 The cost and schedule risks for aerocapture are substantially less understood, along with pro- grammatic and political risks. The present study recommends that future aerocapture studies apply quantitative risk assessment techniques which NASA has matured though numerous manned and robotic missions.13A recent study initiated by the NASA Planetary Science Division concluded that a technology demonstration mission is not required before use of aerocapture on a mission, but remarks that ice giants require additional study.12Quantitative cost and risk estimate for an ice giant aerocapture mission concept is highly desired and will inform the upcoming Decadal survey studies regarding the readiness of its use for a large strategic mission. AEROCAPTURE MISSION ANALYSIS TOOL The identiﬁcation of techniques that enable missions or signiﬁcantly lower their cost is of interest to the planetary science community.2The proposed integrated framework presented can be imple- mented in an aerocapture mission analysis software suite for rapid mission architecture studies. One of major issues faced by the Ice Giants Pre-Decadal Mission study was the lack of software tools for analysis of aerocapture mission concepts. The tool can be used in concurrent engineering facilities to enable mission designers to perform trade studies and assess what-if scenarios for aerocapture mission concepts. The software suite can enable cost-effective, rapid aerocapture mission concept studies without having to resort to selecting a single-point design in the early study phase when the requirements and capabilities may not be well deﬁned. CONCLUSIONS The present study proposes a uniﬁed framework for aerocapture mission concept studies. The importance of interconnectedness between the interplanetary trajectory and vehicle design in early mission design is presented using aerocapture feasibility charts. The methodology is applied to a Neptune aerocapture mission, and shows that fast arrival trajectories can allow the use of low- L=D (L=D0:4) aeroshells and also allow signiﬁcantly shorter ﬂight times ( <8 years) compared to propulsive insertion architectures which take 13 years or longer. The analysis can be extended to other atmosphere-bearing outer planer destinations such as Uranus and Titan. The proposed integrated framework presented can be implemented in an aerocapture mission analysis software suite for rapid mission architecture studies. ACKNOWLEDGMENT The authors acknowledge Dr. Anastassios Petropoulos at the NASA Jet Propulsion Laboratory and and Dr. Nitin Arora, formerly at the NASA Jet Propulsion Lab for providing the interplanetary trajectory data used in this study. A.P.G was a participant of the 30th Plannetary Science Summer Seminar (PSSS) which contributed to the end-to-end mission life-cycle analysis methodology used in the study. A.P.G. thanks Dr. Charles Budney, Dr. Karl Mitchell and Ms. Leslie Lowes, all at the NASA Jet Propulsion Laboratory for valuable lessons during PSSS. 11