Our Solar System\u2019s ice giants, Uranus and Neptune, have been largely left out of the planetary probe game. While all of the other planets\u2014including even the demoted Pluto\u2014have been the subjects of dedicated missions, the ice giants have not. In fact, the only spacecraft to ever even fly by Uranus and Neptune was Voyager 2 in the late 1980s. <\/p>\n
<\/p>\n But the lack of dedicated missions isn\u2019t because they\u2019re inconsequential worlds with nothing to teach us about nature. It\u2019s because it\u2019s difficult. Sure, distant Pluto received a dedicated visit, but it was just a flyby mission. Sending orbiters to distant planets is difficult because they need engines and fuel to enter orbit. They also need to be travelling slower, so the mission takes longer to arrive. And then there\u2019s the fact that solar energy is not a thing that far away from the Sun.<\/p>\n That doesn\u2019t mean we\u2019ll never send one. It just explains why they\u2019ve been left out of the planetary probe game so far. Uranus and Neptune are both fascinating worlds that deserve to be explored more thoroughly. Atmospheric probes will likely be the first step.<\/p>\n Just because they haven\u2019t had dedicated missions doesn\u2019t mean we haven\u2019t studied the ice giants. We know quite a bit about their internal structures and their atmospheric compositions. Enough that we can simulate them and what it might be like for probes sent into their atmospheres and how they can manage the heat. <\/p>\n That\u2019s what the ESA has done as part of an effort to simulate atmospheric probes that we\u2019ll no doubt send to these planets one day. <\/p>\n The ESA\u2019s simulations took place at two of their facilities: the hypersonic plasma T6 Stalker Tunnel at Oxford University in the UK and the University of Stuttgart\u2019s High Enthalpy Flow Diagnostics Group\u2019s plasma wind tunnels in Germany. Both of these facilities are designed to test and understand how probes travel through different planetary atmospheres. <\/p>\n One of the difficulties in simulating probe entry into the ice giants\u2019 atmospheres is velocity. The T6 Stalker Tunnel achieved speeds of 19km\/second, and it\u2019s the fastest wind tunnel in the UK. That\u2019s a start, but ice giant probes will travel even faster than that, which means there\u2019ll be more simulations in the future. <\/p>\n In the meantime, the simulations can still generate valuable data. \u201cThe tunnel is capable of measuring both convection and radiative heat flux and critically provides the required flow speeds for the replication of ice giant entry, with traces of CH4,\u201d said ESA Aerothermodynamics Engineer Louis Walpot. <\/p>\n Uranus and Neptune are similar to Jupiter and Saturn, but there are critical differences. The pair of ice giants contain heavier elements in supercritical liquid oceans well below the surface clouds. These oceans make up a sizable portion of the planets\u2019 masses. Both planets also have methane in their atmospheres, which makes them appear blue. This means that atmospheric probes would face a number of severe challenges.<\/p>\n \u201cThe challenge is that any probe would be subject to high pressures and temperatures and therefore would require a high-performance thermal protection system to endure its atmospheric entry for a useful amount of time,\u201d explained Walpot. These simulations will help engineers understand the challenges and how to design and build a probe that can withstand the entry.<\/p>\n \u201cTo begin designing such a system, we need first to adapt current European testing facilities in order to reproduce the atmospheric compositions and velocities involved,\u201d Walpot said.<\/p>\n Both NASA and the ESA are considering missions to the ice giants, though they\u2019re decades away. Testing at both these facilities is laying the groundwork for the ESA\u2019s potential mission. The ESA has given high priority to an atmospheric entry probe to either of the ice giants. <\/p>\n But there\u2019s lots of time for engineers to work on their simulations and develop probes that can handle the ice giants\u2019 heat. These missions are decades away. <\/p>\n![\"This](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2023\/11\/PWK1_Plasma_Wind_Tunnel_Facility_at_IRS-1024x776.jpg\")
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