Qualitative Assessment of Aerocapture and Applications to Future Missions

Abstract

We examine the current state of readiness of aerocapture at several destinations of interest, to identify what technologies are needed and to determine if a technology demonstration mission is required, before the first use of aerocapture for a science mission. The study team concluded that the current state of readiness is destination dependent, with aerocaptured missions feasible at Venus, Mars, and Titan with current technologies. The use of aerocapture for orbit insertion at the ice giant planets Uranus and Neptune requires at least additional study to assess the expected performance of new guidance, navigation, and control algorithms and possible development of new hardware, such as a mid-lift-to-drag entry vehicle shape or new thermal protection system materials. A variety of near-term activities could contribute to risk reduction for missions proposing the use of aerocapture, but an end-toend, system-level technology demonstration mission is not deemed necessary before the use of aerocapture for a NASA science mission.Nomenclature L∕D = lift-to-drag ratio of vehicle V ∞ = hyperbolic excess velocity, km∕s ΔV = velocity change, km∕s

A Unified Framework for Aerocapture Systems Analysis

“…Studies over several decades have shown that the technical risks associated with aerocapture can be mitigated, 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 programmatic 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.…”

“…13 A 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. 12 Quantitative 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 Performance Analysis for a Neptune Mission Using a Heritage Blunt-Body Aeroshell

“…since the last such study was performed could allow the navigation uncertainty component to be reduced and hence lower the vehicle L/D requirement. Atmospheric uncertainties at Neptune have been modeled in Neptune-Global Reference Atmospheric Model (GRAM), but no improvements are available over the data used by Lockwood et al 1 Spilker et al 4 recommends performing opportunistic stellar occultations of Uranus and Neptune to improve the atmospheric models, but also notes that the technique may only provide information at high altitudes and extrapolating to altitudes relevant to aerocapture carries greater uncertainties. A dedicated research program for combined ground-based observations and modeling efforts is required to reduce the atmospheric uncertainties at altitudes relevant to aerocapture.…”

“…The large navigation and atmospheric uncertainties drive the need for a vehicle with sufficient control authority to perform aerocapture without the spacecraft risking escape or getting trapped in the atmosphere. 4 Several mission concepts and technology demonstration flights have proposed the use of aerocapture, but have never been flown. [5][6][7][8][9] Hall et al 10 showed that aerocapture could enhance missions to Venus, Mars, Titan, and Uranus and enable some missions to Jupiter, Saturn, and Neptune.…”

“…Heritage low lift-to-drag ratio (L/D ≤ 0.4 ) blunt-body aeroshells and existing thermal protection system (TPS) materials are sufficient for aerocapture at Venus, Mars, and Titan. 4,[11][12][13][14] Aerocapture studies have historically used a mid lift-to-drag (L/D) vehicle with L/D of 0.6-0.8 to accommodate the large navigation and other uncertainties at Neptune. 15,16 Planetary entry vehicles flown to date are low-L/D vehicles with L/D less than 0.4.…”