Analysis of Galileo's Jupiter entry probe reveals gaps in heat shield modeling

October 15, 2019

WASHINGTON, D.C., October 15, 2019 -- The entry probe of the Galileo mission to Jupiter entered the planet's atmosphere in 1995 in fiery fashion. As the probe descended from Mach 50 to Mach 1 and generated enough heat to cause plasma reactions on its surface, it relayed data about the burning of its heat shield that differed from the effects predicted in fluid dynamics models. New work examines what might have caused such a discrepancy.

Researchers at the Universidade de Lisboa and the University of Illinois at Urbana-Champaign report their findings from new fluid radiative dynamics models using data transmitted from the of Galileo's 30-second entry. The paper, published in Physics of Fluids, from AIP Publishing, employs new computational techniques developed in the nearly 25 years since the mission.

"Early simulations for the probe design were conducted in the 1980s," said Mario Lino da Silva, an author on the paper. "There are some things we can do in 2019, because we have the computational power, new devices, new theories and new data."

Galileo's probe entered Jupiter's gravity traveling 47.4 kilometers per second, making it one of the fastest man-made objects ever. The fireball caused by the descent warmed the carbon phenolic heat shield to temperatures hotter than the sun's surface.

Data from the probe revealed the rim of the heat shield burned significantly more than even today's models would predict, measured by what is called the recession rate.

"The fireball is a kind of soup where a lot of things happen at the same time," he said. "One problem with modeling is that there are many sources of uncertainty and only one observed parameter, the heat shield recession rate."

The group recalculated features of the hydrogen-helium mixture the probe passed through, such as viscosity, thermal conductivity and mass diffusion, and found the oft-cited Wilke/Blottner/Eucken transport model failed to accurately model interactions between hydrogen and helium molecules.

They found the radiative heating properties of hydrogen molecules played a significant role in the additional heating the probe's heat shield experienced.

"The built-in heat shield engineering margins actually saved the spacecraft," Lino da Silva said.

Lino da Silva hopes the work helps improve future spacecraft design, including upcoming projects to explore Neptune that will likely not reach their destinations until after he has retired.

"In a way, it's like building cathedrals or the pyramids," he said. "You don't get to see the work when it's finished."

Lino da Silva next looks to validate some of the simulated findings by reproducing similar conditions in a shock-tube facility tailored for reproducing high-speed flows.
-end-
The article, "Computational fluid radiative dynamics of the Galileo Jupiter entry," is authored by Luis dos Santos Fernandes, Bruno Lopez and Mario Lino da Silva. The article will appear in Physics of Fluids on Oct. 15, 2019 (DOI: 10.1063/1.5115264). After that date, it can be accessed at https://aip.scitation.org/doi/10.1063/1.5115264.

ABOUT THE JOURNAL

Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids. See https://aip.scitation.org/journal/phf.

American Institute of Physics

Related Atmosphere Articles from Brightsurf:

ALMA shows volcanic impact on Io's atmosphere
New radio images from ALMA show for the first time the direct effect of volcanic activity on the atmosphere of Jupiter's moon Io.

New study detects ringing of the global atmosphere
A ringing bell vibrates simultaneously at a low-pitched fundamental tone and at many higher-pitched overtones, producing a pleasant musical sound. A recent study, just published in the Journal of the Atmospheric Sciences by scientists at Kyoto University and the University of Hawai'i at Mānoa, shows that the Earth's entire atmosphere vibrates in an analogous manner, in a striking confirmation of theories developed by physicists over the last two centuries.

Estuaries are warming at twice the rate of oceans and atmosphere
A 12-year study of 166 estuaries in south-east Australia shows that the waters of lakes, creeks, rivers and lagoons increased 2.16 degrees in temperature and increased acidity.

What makes Saturn's atmosphere so hot
New analysis of data from NASA's Cassini spacecraft found that electric currents, triggered by interactions between solar winds and charged particles from Saturn's moons, spark the auroras and heat the planet's upper atmosphere.

Galactic cosmic rays affect Titan's atmosphere
Planetary scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed the secrets of the atmosphere of Titan, the largest moon of Saturn.

Physics: An ultrafast glimpse of the photochemistry of the atmosphere
Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

Using lasers to visualize molecular mysteries in our atmosphere
Molecular interactions between gases and liquids underpin much of our lives, but difficulties in measuring gas-liquid collisions have so far prevented the fundamental exploration of these processes.

The atmosphere of a new ultra hot Jupiter is analyzed
The combination of observations made with the CARMENES spectrograph on the 3.5m telescope at Calar Alto Observatory (Almería), and the HARPS-N spectrograph on the National Galileo Telescope (TNG) at the Roque de los Muchachos Observatory (Garafía, La Palma) has enabled a team from the Instituto de Astrofísica de Canarias (IAC) and from the University of La Laguna (ULL) to reveal new details about this extrasolar planet, which has a surface temperature of around 2000 K.

An exoplanet loses its atmosphere in the form of a tail
A new study, led by scientists from the Instituto de Astrofísica de Canarias (IAC), reveals that the giant exoplanet WASP-69b carries a comet-like tail made up of helium particles escaping from its gravitational field propelled by the ultraviolet radiation of its star.

Iron and titanium in the atmosphere of an exoplanet
Exoplanets can orbit close to their host star. When the host star is much hotter than our sun, then the exoplanet becomes as hot as a star.

Read More: Atmosphere News and Atmosphere Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.