Could a nuclear-powered flywheel circling Jupiter be the key to interstellar exploration? A team of Bulgarian scientists claims that Jupiter is a particularly suitable planet for this kind of exploration in a paper posted on the preprint server arXiv, meaning the research has yet to be peer-reviewed. This is because the planet has some characteristics that make it especially resistant to human interference.
The scientists say their proposed aircraft, a “subatmospheric” craft designed to work better in the Jovian atmosphere, could open new paths for custom-built spacecraft. How close are we to circling Jupiter? Let’s examine the gas giant that is almost more a star than a planet.
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The case of Jupiter is straightforward, the scientists at Sofia University write in their paper:
“Among the planets of the Solar System and their satellites, Jupiter is a viable target for exploration, as it has a thick atmosphere suitable for aerodynamic flight, there is no solid surface that could be contaminated after the end of the mission, and Atmospheric data to design an aircraft is readily available.”
Our main and imminent targets on the Moon and Mars have almost no atmosphere. That’s fine, but it’s a huge technological challenge when it comes to thinking about making both places liveable for people, where their technology can continue to work despite the very different gravity, wind, and so on.
Jupiter’s atmosphere, on the other hand, is so thick that we can basically fly normal planes that are carefully attuned to the physics and logistics of exploring the planet’s atmosphere.
Jupiter is so far from the Sun that we can’t rely on solar energy to propel an airplane into the atmosphere. Nor can we depend on combustion, which requires oxygen; Jupiter’s atmosphere is 90% hydrogen. The researchers, therefore, suggest a type of “nuclear battery” propulsion whose fuel could be sustained for decades, and which does not require oxygen or sunlight:
Nuclear fuel has an extremely high energy density that allows for months, if not years, of sustainable flight before the fuel runs out. Unlike chemical combustion, the nuclear reaction does not rely on oxygen to produce heat. This allows flying in anaerobic atmospheres and without the need to carry an oxidizer.
The engine can be designed as a ramjet, which relies on supersonic gas compression rather than turbocharging to produce thrust, which has a number of advantages: it has few moving parts, minimizing the risk of mechanical failure, and it is lightweight . The latter is of paramount importance, given the capabilities of launch vehicles and the cost of putting every pound into orbit of other planets.
(Note: No renderings of the aircraft proposed by the scientists exist. The main image shows NASA’s nuclear space propulsion concept.)
According to scientists, Jupiter is also one of the only places that make sense for humans to explore at this juncture. Why? Because using a nuclear ship in a context where it will crash into a rocky surface means that we will automatically have contaminated another planet with radioactive material.
This excludes Titan, our favorite moon, whose thick atmosphere covers a solid surface:
For rocky bodies with dense atmospheres, like Venus and Titan, there is a moral obstacle to using nuclear power for aerodynamic flight, as the plane will end up crashing to the surface and contaminating [the] local ecosystem with radioactive material. These considerations make gas giants a viable option for such a mission. They present thick atmospheres without a hard surface and are particularly interesting for exploration, due to the presence of climate and different atmospheric phenomena.
By conducting a few simple initial explorations of Jupiter, scientists could learn a great deal both about the planet itself and about the technology of the first Jovian aircraft. In fact, these researchers explain, missions like this could be the key to unlocking the use of resources “in situ”, that is, for their extraction and use to make fuel for the return trip, for example, or for the settlers who plan to stay on other planets long term.
All that is needed is an almost normal aircraft with a nuclear-powered ramjet.
