According to multiple lines of evidence, Venus was once a much different planet than it is today. But roughly 500 million years ago, a massive resurfacing event triggered a runaway greenhouse effect that led to the hot, poisonous, and hellish environment we see there today. Therefore, the study of Venus presents an opportunity to model the evolution of planetary environments, which can serve as a reference for what could happen in the future.
In the coming years, NASA plans to send lighter-than-air missions to Venus to explore the atmosphere above the cloud tops, where temperatures are stable and atmospheric pressure is comparable to that of Earth. With support from NASA, engineers at West Virginia University (WVU) are developing software that will enable balloon-based aerial robots (aerobots) to survey Venus’ atmosphere in small fleets.
Venus presents a special challenge to space explorers. Yes, there is a surface, but hellish temperatures and atmospheric pressure on the surface of Venus has a tendency to crush spacecraft fairly quickly. Short of building a submarine-rated surface explorer, maybe there’s a better way to look at the hothouse planet? A newly proposed NASA concept suggests using airships. Yes, airships with people in them.
But as you will see below, balloons and airships have been discussed extensively in the past decade by NASA and the Europeans as the best way of exploring Venus without needing to touch its hellish surface.
Venus may seem nothing but a distraction to an agency that is talking about exploring Mars in the 2030s (with Orion’s recent uncrewed test being the first advertised step of that, although critics say it won’t get us to the Red Planet). Leaving that aside, however, exploring Venus by balloon is not a new idea at all, even within NASA. The backers of the High Altitude Venus Operational Concept (HAVOC) even argue we should head to Venus before Mars, as one of the co-leads recently told Universe Today.
“A human mission to Venus is not on a lot of people’s radar, but we’ve really enjoyed working on the concepts for this mission,” said Langley’s Chris Jones, project co-lead, in an interview with Universe Today’s Nancy Atkinson. “This was an internal study: what does the future of humankind in space look like? Frankly, we see Venus as potentially no later than the second planetary destination that humans might go to, after Mars or even before Mars.”
Why? Jones explained that because it takes a shorter time to get to Venus, that makes it a “stepping stone or practice run” to get humans to Mars. “The best would be a long lived surface lander, but technology issues for surface robotic missions are pretty significant, and a human mission to surface is nearly insurmountable. What’s left is a good platform for a science mission at mid-level altitudes, and it paints a good picture for a human mission in the atmosphere at 50 kilometers.”
The clouds of Venus, Jones said, present an ideal spot for humans to roam from a spacecraft. The conditions at 50 kilometers (31 miles) above the surface are about the same pressure and atmosphere as Earth.
“Air itself is a lifting gas at those altitudes,” he added, “so you don’t have to bring some ridiculous supply of helium for this to work. And the rest of the environmental parameters at 50 kilometers are actually quite nice: the gravity is about the same as on Earth’s surface, the atmospheric pressure is about the same as Earth, and we can potentially manufacture a significant amount of that air by processing carbon dioxide. These are some of the facts we saw early on that inspired us to do this.”
There also would be more solar power and protection from radiation than Mars, and the temperature — although fairly hot — would be possible to account for fairly easily in spacecraft designs.
Jones provided some details on how the crew would spend about 30 days exploring the planet after a journey there and back (440 days total). Bear in mind that the mission is just in the early stages of even thinking about development. Cost, timeline, approvals and many other hurdles would need to be overcome before it could even become a reality.
“The big parameters of Venus’ atmosphere is the big longitudinal winds,” Jones said. “If you just rode them, it would take you about 110 hours to circle the planet. The other component of winds would push you towards the poles. In order to stay near the equator where there is less turbulence, the airship would ride the longitudinal winds while using a propulsion system to counter those winds pushing you towards the poles.”
The concept arose from science objectives for the planet out of NASA’s Venus Exploration Analysis Group, Jones said, whose aims include understanding the atmosphere and its interaction with the surface. NASA’s Langley Research Center also has human objectives they considered, such as showing how people can work in deep space and develop advanced technologies to accomplish that.
The HAVOC mission would start with a series of phased exploration sorties. The first phase would be examining the Venusian atmosphere with a robotic mission, and the second would be crewed ride to orbit that would include deploying an uncrewed robotic airship in the atmosphere.
The third phase is the 30-day mission described above, while the fourth phase could potentially be as long as a year. If it gets to a Phase 5, that would be a “permanent presence in Venus’ atmosphere”, Jones said.
Of note: balloons have been discussed before within NASA, particularly by Venus exploration advocate Geoffrey Landis of NASA Glenn, and Jones told Universe Today that this new team found much inspiration from Landis’ previous work.
Universe Today interviewed Landis in 2008 about missions he proposed about human-colony airships and uncrewed solar-powered airplanes. And in this 2010 study, he suggested three ideas for exploring the surface using uncrewed low-altitude balloons. One would skim the clouds around 25 kilometers (15.6 miles) and two other concepts (more rigid, naturally), would fly about 5 kilometers (3 miles) high. This was presented at an American Institute of Aeronautics and Astronautics meeting that year.
“A notable advantage of the carbon dioxide atmosphere of Venus is that this allows a much wider range of lifting gasses for a balloon; not merely the hydrogen or helium usually used for terrestrial balloons,” Landis wrote in the paper. “Oxygen and nitrogen, in fact, are lifting gasses in the Venus atmosphere (although not good ones). At the altitudes considered, two other lifting gasses are water (which is a gas at the temperatures considered) and ammonia.”
Landis was also not deterred by harsh surface conditions. While Venus’ surface is difficult — its 480 Celsius (900 Fahrenheit) thick atmosphere destroyed the Soviet Venera probes in minutes — he’s secured early-stage NASA funding for a robotic landsailing rover concept nicknamed “Zephyr”. “Sailing on Venus! How cool is that? The project will have an exceptional public engagement factor,” the description page for the Venus Landsailing Rover reads.
In a nutshell, Glenn has created electronics that can continue to function in temperatures similar to what are found on the surface. Simulations also show that solar cells would work, albeit at reduced efficiency. Hence the idea to use a heavily-reinforced landsail to take advantage of Venus’ 100-times-more-pressure-than-Earth atmosphere at the surface. Wind speeds are less than a meter of second, but have terrific force behind them. And at least some of Venus appears to be flat, with rocks only a centimeter thick in pictures from Venera.
Balloons have also been considered by the European Space Agency, particularly in the form of an uncrewed Venus Entry Probe discussed in detail in this presentation by Surrey Satellite Technology Ltd. It would include a Low Venus Orbiter that would map the planet to complement closer-to-ground measurements, a Venus Relay Satellite that would send information from the balloon, and the “aerobot” itself.
“The aerobot consists of a long-duration balloon and gondola … that will analyze the Venusian middle cloud layer at an altitude of ~55 km, where the environment is relatively benign. The balloon will deploy a swarm of active ‘ballast’ micro-sondes, which, once deployed, will determine vertical profiles of the lower atmosphere,” the presentation reads. More detailed information is available from this 2004 ESA workshop presentation by Surrey and this ESA webpage, which says the study was completed in 2005.
Students have even explored Venusian balloon ideas, such as in the 2014 Summer School Alpbach cosponsored by the European Space Agency. An uncrewed idea called EvolVe suggests a joint orbiter and balloon mission to see how tectonic activity and volcanoes affected the surface of Venus, among other scientific goals. The balloon would hover in the same general region, about 50 to 60 km (31 miles to 37 miles), and probe the surface using radar and other tools. It’s one of two concepts selected for further investigation that could lead to a science conference presentation and/or science journal publication.