A manned mission to Venus is possible

Concept: With airships over Venus

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Mars is often the focus of missions for planetary research. It is the planet that has so far been explored most often with rovers and orbital probes. Mars is so interesting for researchers because it is assumed that billions of years ago were much more Earth-like and therefore more life-friendly conditions. But it's not the only interesting place in the inner solar system.

Venus, which is also called the "dark twin", which alludes to a destructive development of what was once supposedly a more Earth-like world, would also be an interesting target for closer exploration. A concept for manned missions to Venus is currently being developed by NASA scientists in collaboration with the Langley Research Center.

Manned flights to Mars have been discussed repeatedly for a long time. They would be a logical continuation of the intensive exploration of the red planet with numerous probes and rovers. A flight to Mars, along with a return to the moon, is the most likely and at the same time the largest project for manned space travel in the next few decades.

But practical implementation is still a long way off. Among other things, the problem of increased exposure to solar and cosmic radiation over a longer period of time during interplanetary flights represents a challenge for missions in deep space. But Mars is not the only conceivable target for manned missions in the inner solar system.

NASA scientists have developed a concept for the manned exploration of Venus, as the US magazine IEEE Spectrum reported.

Airships in the atmosphere of Venus
(Image: NASA)
A creative approach is required for this, because the surface of Venus is therefore absolutely hostile to life and technology. There are temperatures of around 500 degrees with an average pressure of 92 bar, which corresponds to a pressure in about 900 meters of water on earth. Entering the planet's surface is therefore ruled out for the foreseeable future. Instead, Dale Arney and Chris Jones of the NASA System Analysis and Concepts Directorate at Langley Research Center in Virginia, NASA researched the use of manned atmospheric airships.

They would fly at an altitude of around 50 kilometers above the surface, where the environmental conditions are more bearable at around 75 degrees with an external pressure of one bar. One advantage of Venus being closer to the sun is the more intense solar radiation, which benefits the solar-powered, helium-filled airship. It is about 40% higher than on Earth and 240% higher than on Mars. In addition, the astronauts at the targeted flight altitude within the Venusian atmosphere are exposed to a harmless level of cosmic radiation that roughly corresponds to the ambient radiation in Canada. Unprotected astronauts on Mars would be exposed to radiation levels of 0.67 millisieverts per day, which is roughly 40 times the dose of ambient radiation on Earth.

30 days with Havoc
Another advantage of a manned mission to Venus is the shorter distance to Earth. The distance of closest approach is 38.9 million kilometers, well below the closest distance to Mars, which is 55.4 million kilometers. The Venus astronauts would be on their way to Venus for 110 days. Once there, they would have 30 days on board the airship ahead of them. The researchers call their design High Altitude Venus Operational Concept, which will first be tested on a robotic airship. After the end of the 30-day atmosphere flight, the return flight begins, which, at around 300 days, takes significantly longer than the journey.

In total, the astronauts would be in deep space around 440 days. This is a long time, but significantly shorter than a possible manned mission to Mars, as the researchers point out. This could not be represented in less than 500 days, but realistically one would have to reckon with a mission duration of 650 to 900 days. In the event of a serious incident after arrival, the astronauts would have to hold out on Mars until the next return window opens to allow the planets to come closer enough.

In the case of a mission to Venus, on the other hand, there would be the one-time possibility of canceling the mission and flying home immediately after arriving on Venus. This could become acute in the event of problems with the airship, for example, a scenario that does not seem entirely improbable in view of the hypothetical mission profile.

Near the equator, where the atmosphere is relatively stable, wind currents circulate at around 100 m / s, which completely orbit the planet in around 110 hours. The self-rotation is negligibly small with a Venus day longer than a Venus year, with one of the puzzles in the exploration of our neighbor closer to the sun.

The length of the day of Venus is less important for the airship crew. The course of the equatorial wind currents is more relevant. The circular 100 m / s current runs from south to north. So the airship will steer south as long as there is plenty of solar energy available and will swivel north when the irradiation is decreasing and the crew has to save energy.

Naturally, there will be no outdoor activities during your stay in the airship. The crew will stay in a habitat with a volume of 21 cubic meters, which is based on the Space Exploration Vehicle.

The airship has an astonishing payload capacity of 70 tons, of which 60 tons are used on the ascent stage, a return vehicle equipped with a two-stage rocket engine that is moored under the airship. It is based on the existing but much smaller Pegasus rocket, which transports satellites into orbit using a carrier aircraft.

Lots of changes
The course of a mission, as outlined by the NASA researchers, was anything but trivial and includes numerous transfers in space close to the planet. First, the astronauts start with an Orion capsule. This takes them into orbit, where the previously unmanned interplanetary spaceship is waiting to take them to Venus.

A second spaceship is already waiting in Venus orbit that the airship has transported. The astronauts switch to the other ship and begin the descent while the interplanetary ship remains in orbit.

The entry sequence is demanding. “With no landing possible on the surface, this part of the mission will be extreme. As a rule, when we talk about missions to Mars, for example, we are talking about EDL (Entry, Descent and Landing, "the researchers clarify." In our case, a landing is clearly synonymous with a dramatic failure. So we are talking about EDI (Entry, Descent and inflation). "

During the descent, the airship is surrounded by an aeroshell with the float not deployed and the entry sequence begins at a speed of 7200 meters / second. During the next seven minutes, a planned deceleration to around 450 m / s is to take place, and a parachute is to be deployed for further deceleration. A little later the aeroshell is thrown off and the airship then continues its descent at around 100 m / s, while it unfolds and the lifting gas inflates the float.

Finally, the volume and the resulting load capacity increase significantly, so that the redundant parachute is no longer needed and is thrown off. The descent is ended at an altitude of 50 kilometers above ground.

After the 30-day exploration of Venus, the astronauts climb a small return capsule at the top of the ascent stage, the airship is separated and the astronauts return to the interplanetary spaceship. With this they will start the flight home, which takes around 300 days. Arrived in earth orbit, one last change takes place in a waiting Orion capsule, with which the Venus drivers finally land on earth.

Ambitious project
The HAVOC team considers its concept to be a realistic possibility of exploring our hot neighbors with a manned mission, but in fact the implementation sometimes requires technologies that are not available at short notice. For example, it depends on Block IIB, the large configuration of NASA's new SLS heavy-duty rocket, to start the various mission components. However, this will probably not fly before the end of the 2020s.

In addition, the mission profile with its numerous transfers from spaceship to spaceship has plenty of room for complications. The core of the mission in particular, the use of the airship, is a daring maneuver without precedent, beginning with the critical part of the entry into the atmosphere and ending with the final ascent. In general, the concept of a lander and a mother ship that remains behind has not been used since the Apollo missions.

Mission with potential
Despite the numerous challenges, NASA researchers are sticking to the scientific and aerospace benefits of the mission. Venus has been largely ignored for decades, with the exception of ESA's Venus Express mission, which recently came to an end after eight fruitful years, Raumfahrer.net reported. It is as interesting as Mars in many ways. Also on Venus around a billion years ago, significantly different environmental conditions are likely to have prevailed. Similar to Mars, Venus may have had water and a much different, more complex atmosphere.

The reasons for the dramatic climate changes and the extreme greenhouse effect that has occurred, from which the hot surface temperatures result, are not yet adequately understood. Research could certainly provide valuable insights into climate developments on earth.

Finally, the researchers conclude their conception with a truly visionary idea of ​​interplanetary expansion. The atmosphere of Venus is a quite acceptable place to stay in several respects, possibly even more suitable for longer stays than the surface of Mars. The researchers dream of long-term atmospheric habitats. These “cloud cities” would be a further step for mankind on the way into space.