Ask Astro: Why will DAVINCI so quickly pass through Venus’ atmosphere?

Why will the DAVINCI spacecraft drop its parachute so soon after entering the atmosphere of Venus? Won’t that mean less time to collect data and images?

Steven Portalupi

Newmarket, New Hampshire

Venus and its massive atmosphere present an incredibly challenging environment for any in situ probe mission. The planet’s surface temperature is around 860 degrees Fahrenheit (460 degrees Celsius) thanks to dense CO₂ atmosphere, which also creates a surface pressure 90 times greater than that of Earth at sea level.

Sulfuric acid clouds exist about 25 to 43 miles (40 to 70 kilometers) above the surface in a thick layer. When the DAVINCI Descent Sphere (DS) spacecraft releases its main parachute about 32 minutes into the descent – ​​about 39 km above the surface – the temperature will already be 304 F (153 C).

This truly hellish environment presents challenges that other planetary probes do not have to face. Trying to build a parachute that could survive these conditions would be risky and expensive. Thus, DAVINCI uses fixed brake plates to slow its descent after the release of the parachute. The thick Venusian atmosphere also helps because the descent is more like settling into fluid than falling through air.

It is true that by cutting the parachute, the DS will spend less time in the lower atmosphere of Venus. But in many ways it’s an advantage because the machine spends less time there exposed to the harsh conditions. If the DS was left on the parachute longer, it would have to be designed to absorb more heat to keep the internal science instruments cool and have larger batteries to keep the craft running longer during the descent. This would increase the weight, which would make it even more difficult to build a parachute to support it!

To ensure that DAVINCI achieves its scientific goals, the DS uses state-of-the-art chemistry instruments and telecommunications systems that can sample the atmosphere every 500 feet (150 meters) of descent and take near-infrared images every the few seconds. The DS will transmit this data to its companion spacecraft in Venus orbit, the Carrier Relay Imaging Spacecraft (CRIS), before reaching the surface. Thus, in the short hour that DAVINCI will spend in the atmosphere of Venus, it will acquire groundbreaking measurements and images far beyond what any previous mission has achieved.

Colby Goodloe

DAVINCI Descent Sphere Lead Engineer, NASA Goddard Space Flight Center, Greenbelt, Maryland, on behalf of the DAVINCI Project