Abstract :
Aerostats in the atmospheres of Saturn and Uranus which mine helium-3 in a far future (>2150) economy based on clean D-3He fusion power and space propulsion have been considered since Project Daedalus [1, 2]. While even much easier D-T fusion power remains elusive, and engines capable of sustaining chemical launch vehicle thrust power densities for years instead of minutes present great engineering challenges, like the Drake Equation this vision presents a roadmap for each generation to make its contribution. We can ask these example questions of joint interest to contemporary basic science and the 3He vision, with realistic mission solutions in the next 20 years:
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3He and 4He concentrations tell us about formation and helium sequestration in cores, and are of obvious interest to 3He mining. Given the difficulties of retrieving He concentrations from remote sensing data, these concentrations remain uncertain even after Cassini and Voyager.
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Density, composition, and particle size distribution in the innermost rings tells us about the origin and lifetime of ring systems. This science then informs hazard assessment and mitigation for vehicles entering and leaving the atmosphere. The most exciting recent result is the success of the Cassini Grand Finale, which shows that an unarmored spacecraft can survive multiple near-cloudtop passages of Saturn’s ring plane.
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Vertical wind shear and storms [3] tell us about heat balance, internal structure, and planetary formation. This science then helps us assess violent weather hazards to long-lived aerial mining platforms.
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In the case of Uranus, verifying the CH4 concentration profile from in-situ measurements would validate the methane-free stratospheric gas (MFSG) balloon first conceived by Jones [4], which uses the molecular weight difference between the troposphere and stratosphere to provide balloon lift without requiring heat.
I will conclude by suggesting topics for near-term, small-group observing proposals for JWST and ground-based telescopes, and discuss the impact on these topics of the NASA Uranus Orbiter Probe instrument suite and the aerostats released into the Uranian atmosphere by the Chinese Tianwen-5 mission [5].
[1] Parkinson, R. C (1978) “Project Daedalus: Propellant Acquisition Techniques,” Project Daedalus Final Report, British Interplanetary Society
[2] Lamontagne, M. https://sites.google.com/view/worldships/home-base/fuel-acquisition
[3] de Pater, I. et al. (2014), “Record-breaking storm activity on Uranus in 2014,” Icarus 252, 121.
[4] Jones, J. (1998), “Ultralight Balloon Systems for Uranus and Neptune”, NASA Tech Brief NPO-20543
[5] Jones, A. (2023) https://www.planetary.org/articles/chinas-plans-for-outer-solar-system-exploration
