The best level of living on a planet may not always be the obvious surface. While Moon and Mars settlements could be built inside lava tubes and other underground burrows, on Venus the best level for a human colony is above ground (way above). There is no need to step foot on a planet like Venus to inhabit it; any “first step” by humans on its surface would be a symbolic gesture only, with little practical benefit for actual colonization.

Living on the ground or in caves is something humans know very well. Living in structures that float high in the clouds however is unlike anything that we have ever done before, and presents many new challenges. To achieve it requires both imagination and careful consideration. The following are some of my notes on the subject.

Vehicle classification based on movement

Airborne vehicles on Venus could be roughly classified to three main types by their movement style: flyers, kites and drifters.

Flyers are actively powered aircraft that continuously move in the air. Their design is aerodynamic, similar to airplanes on Earth. By flying continuously eastward against the superrotation of the atmosphere, a flyer could stay in daylight perpetually, perhaps even be solar powered and not require large energy storage.

Kites are tethered airships that are attached to the surface of Venus with long cables. Unless their “anchors” are moving, they will naturally follow the surface day cycle of Venus, about 1400 hours of continuous daylight followed by an equal duration of moonless night. Their design needs to be aerodynamic, and like kites on Earth, they would be able to “sail” against the prevalent winds to maintain altitude with very little power. Cable systems that reach tens of kilometers above ground would need to have multiple “kytoons” along their lengths, to distribute the weight of the cable itself.

Drifters are freely floating lighter-than-air airships that mostly follow along the existing air currents, though they should be capable of small course corrections when needed. The movement of cloud patterns on Venus suggests that passive drifting would result in a cycle of about 40-50 hours of daylight and 40-50 hours of nighttime, varying depending on altitude and latitude. While drifting the effective airspeed is almost zero, so a drifter does not always have to maintain a streamlined aerodynamic shape. But it is good for drifters to be somewhat “dirigible” [i.e. “steerable”], even capable of powered flight when needed.

This classification may seem arbitrary, but knowing the intended purpose of a ship is helpful in making design decisions. The following notes are mostly intended for the passive drifter type ships, but some may apply to the other types of ships as well.

Yellow and Blue Air

When building and maintaining a ship based on containment and separation of different gases, it is important to be clear about what gases go where, especially since many of them look identical to human senses. This is why the following color-based nomenclature is suggested:

Yellow air stands for any Venus atmosphere based gas mixtures, not breathable for humans. It is used both for the raw atmosphere, and air that has been scrubbed of toxins, but still contains too much CO2.

Blue air is any gas mixture which is breathable for humans. As we know, normal Earth atmosphere is less dense than normal Venus atmosphere, so blue air can typically also be used as a lifting gas. In airship construction, “blue” areas mean all areas of the ship where humans can breath unaided.

This shorthand vocabulary makes it easier to discuss the engineering of an airship for Venus, but it could be adopted in the actual colonization itself; For example, any tanks, valves and pipes handling gases on board the ship could be appropriately color-coded, to help ensure correct operation under any condition. [The couplings could even be designed to be purposely non-compatible, to make accidental mixing less likely.]

[There are of course more colors available for naming gas mixtures; how about “red air” for mixtures of hydrogen and oxygen?]

Colony altitudes: 50-55 km

Choosing the altitude for human habitation is a matter of trade-offs. At about 50 km the atmospheric pressure is the same as at sea level on Earth, but daytime temperatures can be upto 20 degrees higher than the hottest climates on Earth. At 55 km, atmospheric pressure is about the same as on Earth at 5.5 km above sea level (for comparison, the base camp to Mt Everest is at 5.3 km elevation), and the temperature is a fairly pleasant 300 K.

Beside pressure and temperature, altitude also affects the speed of the air currents that push the drifter onward. The amount of radiation that the ship receives is also affected by altitude: this includes not only harmful cosmic radiation, but also the amount of sunlight that penetrates the clouds during daytime. A ship for humans should be designed to handle the range of temperatures, pressures, and haze conditions at these altitudes, with some tolerance to spare.

Indoor temperature in the blue areas can be kept constant by actively cooling it as needed, utilizing some power source to transfer excess heat outside the ship. The outside of the ship should also reflect most wavelengths of light; also window materials should be selective in what wavelengths they pass in. Too much insulation may increase the greenhouse effect; thermally conductive elements in the roof could help with passive cooling.

Indoor pressure of blue air does not need to be kept constant regardless of altitude, it can be adjusted according to outside pressure to avoid straining the structure of the ship. [For safety reasons, the blue areas should still be kept slightly overpressured compared to outside yellow air, to keep inevitable leaks pushing out instead of in.] The partial pressure of oxygen should always be kept at Earth sea level to avoid both mountain sickness and oxygen toxicity. In practice this would mean adjusting only the nitrogen component in blue air to account for pressure changes; this could be achieved using separation devices, for example pressure swing adsorbers, to separate and capture nitrogen out of mixed blue air.

Buoyancy and altitude control

Drifters are designed to be as passive aircraft as possible, but they still need to be able to maintain and control their altitude, perpetually and under all conditions, if permanent habitation is the goal. If the ship ascends too high, or descends too low, the integrity of the whole ship is endangered, due to ambient pressure either tearing it apart or crushing it. In practice, automatic altitude adjustments would be based primarily on readings from barometers and thermometers connected to outside air through static ports, so they would work even without accurate altitude measurements.

Any habitat that can support human life will have to be thousands of kilograms in total mass, most of it denser than yellow air. To stay at an altitude by buoyancy alone, the amount of lift from buoyant elements would need to counteract exactly the amount of gravitational pull. There is no force holding an airship in place, just different forces pulling it in different directions, that need to be equalized. An air “station” should be able to stay afloat even during power shortages, this means defaulting to either neutral or positive buoyancy.

A station should also be able to take on new cargo or send out drone ships. These scenarios imply that the ship’s total mass can change suddenly, and buoyancy must be adjusted simultaneously if altitude is to be kept. Existing lighter-than-air ships on Earth do not have the ability to quickly change the amount of lift provided by gas bags, so some new designs would need to be engineered and developed. Dropping ballast or venting lifting gas are not long-term solutions for adjusting lift on Venus.

Adjustable lift elements could be designed with multiple compartments, ballonets, or as one big compressible envelope with adjustable volume. In each case, reserve tanks of pressurized lifting gas are needed, with pumps to inflate and deflate the gas bags.

The actual transfer of mass onto or off the ships should of course be done carefully. For example, drone ships landing on board should turn off their engines gradually, so that the receiving ship has time to adjust its buoyancy to the added mass.

Launch altitudes: 70-75 km

Since Venus colonies will be airborne, any launches of space vehicles will also need to happen from airborne platforms. To conserve rocket fuel from fighting against air resistance, it makes sense to launch rockets from the highest altitude achievable with buoyancy. If colonization is successful, it should be possible to manufacture rocket fuel from material harvested from yellow air at the colony altitudes, then lift the rocket, along with its fuel and payload, up to thinner atmosphere using special high altitude balloons for launching.

At an altitude of 70-75 km, the air is thin and cold, much like 20-25 km above Earth [or surface levels on Mars] and is about as high as balloons can be made to carry heavy cargo. Compared to colony altitude, visibility is also better, and distance makes colony airships below safer from launch accidents. The pressure is below Armstrong limit, so humans must wear space suits or stay inside a pressurized vehicle.

Coordination of launch is delicate and requires guidance and observation from multiple ships in air and in orbit (ground observation will not be practical on Venus, for several reasons). At high altitude, a “rockoon” does not need to be straight vertical when fired, it can be aimed at an angle so it does not hit the balloon from which it hangs. But it is best to launch with a targeted heading, which requires some maneuvering capabilities in the launch platform. Once the rocket has successfully ignited its engines, it can be carefully released from the balloon platform and initiate burn.

Recovery of the high altitude balloon platform is perhaps desirable but not easy. Without the weight of the multi-ton rocket pulling it down, the balloon will quickly rise too high to maintain its integrity, and will burst if not vented. In theory it might be possible to compress hydrogen from the balloon quickly with electrochemical hydrogen compressors after the release, and start a more controlled descent. Such a system could potentially save hundreds of kilograms of hydrogen from being vented per launch, so it might be worth pursuing at some point. [Helium is nearly as good as hydrogen as a lifting gas, but as a noble gas it cannot be compressed either electrically or chemically.]

In the beginning, there will be only few airships on Venus. Entering from space a ship can end up far away from drifter airships at colony altitudes. Incoming vehicles must be equipped with “ballutes” or other means to turn themselves into airships after entry, and be capable of flying some distance to meet with a colony altitude ship for refueling. [More about navigation later.]

Trimming and stability

Since gravity on Venus is almost the same as on Earth, ships should be designed so that their decks stay level with little or no power. Marine ships floating on a surface can have a metacenter, but passively floating airships and submarines are stable only when their center of buoyancy stays directly above their center of gravity. Distance between the two centers provides torque for righting the ship, if the frame of the ship is rigid enough for leverage.

Just about all cargo needed on a self-supporting colony ship is going to be denser than air, which means that the buoyant elements of the ship will take up most of the ships total volume. Since the center of buoyancy must be above the center of gravity, all passively floating airship designs for normal pressures are going to be big and puffy on top, with smaller denser parts hanging down. [I call this the basic “lollipop” shape.]



To have wider and more spacious decks, self-trimming or stabilizing designs should be investigated. Any shifts in the center of gravity will tilt the ship, unless the center of buoyancy is also shifted at the same time. Increasing distance between the two force centers decreases the angle of tilt, but does not completely eliminate it. Some new designs are needed for zero-airspeed stabilization, for example using some of the payload as a movable counterweight. Large gyro flywheels would add angular inertia [at the cost of mass and power]: they will only slow the tilting caused by shifts in the center of gravity, not eliminate it completely.

Shifting the center of buoyancy is possible to some extent. There is an existing technique for this purpose: many airships have fore and aft ballonets that can be filled asymmetrically. [Submarines use an analogous system of “trim tanks” placed at extremes of the ship.]

If the ship is moving in air, either by its own thrust or pulled with cables, a third center is added to the equation, the aerodynamic center [more generally, “center of pressure“, applying also to hydrodynamics in submarines]. Things get more complicated with aerodynamics [for example, the choice of where to place thrusters or towing cable attachments in relation to the force centers], but with predictable airspeed it becomes possible to use relatively small control surfaces, like trim tabs or ailerons, to control attitude and achieve trimming.

Active stabillization at rest is of course possible, for example using compensating thrusters to force the ship level even when the center of gravity is not aligned, but like propulsion thrusters, power is consumed continuously while they are active. For a large “station” style drifter ship, with tons of cargo on board, stability should always be sustainable, even when not moving, or during power outage.

Structural analysis

The “lollipop” shape naturally divides the ship into two main parts, the balloon part at the top which is lighter than (yellow) air, and the dense “gondola” part where people and cargo are situated. The two parts are pulling the ship in opposite directions by forces equal to the total weight of the ship, so their connecting seam is structurally important; It is the foundation of the ship, its “tensile-load-bearing” wall.

The balloon does not need to carry the gondola just by the lower rim of the envelope. Many existing non-rigid and semi-rigid airships use internal suspension cabling, attached to the inside ceiling of the balloon with e.g. catenary curtains and leading down to the roof of the gondola. In addition to distributing the weight of the gondola more evenly to the balloon envelope, the internal cabling allows a non-rigid balloon to hold a more vertically flattened shape.

As a hanging structure that never lands, tensile strength is more important than compressive strength, even in the rigid parts of the ship. The rigidness of the gondola frame is also a trade-off: on the one hand, it helps keep the decks stable and level. On the other hand, if the frame is too rigid, mechanical vibrations get propagated throughout the ship, from machinery or just from the passengers walking about the decks. A combination of rigid and damping elements are probably needed, designed from lightweight and durable materials to keep the total weight down.

Since the structure is not intended to land or stand on its own, and is hanging down, many of the conventions of construction are turned upside down. For example, structural elements must be strongest at the top of the multi-level gondola tower, but less so at the bottom, where they carry less weight.

Bioreactors: not just for food

At its simplest, a photobioreactor is just a transparent plastic bag half filled with water, seeded with some live cyanobacteria, minerals, and trace elements. Yellow air is bubbled slowly from the bottom through the greenish water, where daylight turns it into blue air, collected at the top. The water turns greener and thicker through the day as the bacteria multiply. At the end of the day, the containers can be drained and the excess green mass concentrated for further processing. The plastic bags can then be refilled with water and minerals, in preparation for the next 50-hour day.

The resulting green biomass is an important source of a variety of hydrocarbons, and can be further processed by e.g. fermenting. Various methods of dehydrogenation can be used to produce unsaturated hydrocarbons for making polymers. Even on Earth, biomass grown in bioreactors could become a worthwile “green” replacement for crude oil.

The green biomass can also be eaten (it’s called Spirulina), if it is grown from acceptable ingredients (no too much sulfites or deuterium) and handled properly. It is not a complete food source, so it should be complemented with other forms of bacterial farming, such as yeast for vitamin B12. [Why bacterial farming? Human senses have evolved to see only the macroscale of biology: plants and animals. But a completely artificial ecosystem needs to be built “from the ground up”, starting at the microbiological level, where the real work of biology happens, before advancing on to some carefully chosen angiosperms and invertebrates.]

In an earlier post I implied that “trees are made from just sunlight and CO2, both more abundant on Venus than on Earth”, but that is incorrect. In actuality, for each CO2 molecule that photosynthesis breaks down, it must also break down an H2O molecule. Water and hydrogen are rare on Venus, and will be the main bottleneck for cultivating biomass.

Chemistry: the power of Hydrogen

Hydrogen is the most common element in the visible Universe, and out of all the atoms in the human body, hydrogen atoms are the most common. Hydrogen is so ever-present and chemically active that it is hard to imagine chemistry without it. It is even common practice to leave out hydrogen atoms when drawing chemical structures; there are so many to draw.

In the cloud layer, at colony altitudes for drifters, most of the hydrogen is bound in the clouds themselves, as aerosol droplets of concentrated acid. According to current understanding, the droplets making up the clouds over Venus are not formed by just phase transition, but also by a chemical process fueled by sunlight, called photolysis. In other words, part of the sunlight falling on Venus gets stored as chemical energy in the atmosphere. Could the acidity be just discharged to electrical power, like from a fully charged car battery? [Probably not, at least without grounding the electrical potential somehow.]

The problem with this chemical energy in the form of low pH is handling it safely. All materials of the ship that can face raw yellow air must be able to withstand the chemical energy of cloud stuff without degrading too fast. [Structural integrity is not the only concern, other important material properties could also deteriorate: optical, adhesive, lubricant etc.] Hydrogen and other elements collected and chemically separated from the cloud stuff must also be stored in a safe way, away from raw yellow air.

Cloud harvesting will probably occur in two steps: droplets are collected together into a liquid [drops may even spontaneously condense at the outer surface of the ship, like water condensation on Earth], which can then be electrolytically separated in an airless chamber to collect the hydrogen. This may be possible to do efficiently using nanomembranes similar to fuel cells, but the technology needs to be tailored to Venus. Since sulfuric acid reactions are mostly exothermic, excess heat might become an issue if the released energy cannot be stored or utilized. [Ionic separation may even make it possible to enrich some D from H at the same time.]

Having almost normal gravity can be utilized in industrial separation processes. For example, fractionating columns should work almost as well as on Earth, if they can be kept upright. It is even likely that some separation processes occur naturally in the atmosphere of Venus: For example the ratio of D to H seems to vary somewhat with altitude. It may even become possible to use knowledge of weather patterns to direct harvesting to places where enrichment of D is easier, or for keeping too much D from contaminating the biological ecosystem (including humans).

Both the chemical and biological ecosystems on board should aim at becoming fully closed and recycling, but some waste might still get produced in the long run. One situation where waste may be beneficial is using chaff to study the weather: thousands of ping-ping ball size objects could be released at the same time to the atmosphere, their movement in the winds followed via radar from a distance. Material for chaff can be e.g. something rejected by QA, which does not contain too much rare yellow air elements.

Local manufacture

As far as we know, yellow air is not made of very diverse elements. Only O, C and N can be considered abundant. H, S, Cl, F and some others have been detected in trace amounts, but any other chemical element needed must be imported to the airships, either dropped from orbit or lifted from below. The chemical factories on drifter airships should specialize in producing materials that are made up of only yellow air elements.

Fortunately this includes many forms of polymers and elastomers, carbon fiber precursors, synthetic resins and hardeners. Even photoactive, light emitting, and piezoelectric compounds are possible. Most polymers are insulators, but some polymers can be made conductive, both thermally and electrically. Their conductivity is not quite as good as Cu or Al, and they are certainly more difficult to form into electrical wiring.

Many interesting 2-D lattice molecules are also possible in theory to form out of yellow air elements, but the processes to manufacture and apply graphene-like materials are not mature yet. Carbon nanotube wires are in theory better conductors than Cu, which would make it possible to create very lightweight inductors and windings for electromagnets, if they could be manufactured at scale. [Special ferromagnetic metals for magnetic cores would still be needed to build efficient electromagnetic motors or turbines.] Using ordinary carbon fiber for electrical wiring and electromagnetic windings is not an optimal solution; it may work, but inefficient conductivity wastes part of the electricity as heat; and there is already too much of heat in colony altitudes of Venus. [Perhaps more suitable for Mars colonies?]

In a self-sufficient colony there should exist the capability to create replacement parts for any of the structural parts of the ship itself, if not on every ship, at least distributed among a fleet of ships. Biomass produced by the bioreactors can be used as a raw ingredient to many kinds of materials. Especially useful would be strong fiber filaments that could be robotically woven into flexible fabrics for sails, parachutes and balloon envelopes, or combined with resins and hardeners to form rigid composite structures, pressure tanks, fractionating columns, or any rigid parts for the frame.

It is unlikely that sophisticated nanoscale items such as high-end computer chips or nanomembranes can be produced locally, so spare ones need to be imported and kept in store for emergencies. Essential sensory equipment, such as pressure gauges, barometers and radar antennae, may be possible to build locally, but the reliability of such “home-made” instruments must be well tested before relying solely on them.

For many reasons it is good to separate the manufacturing areas from the main blue areas, and let the solvents and hardeners evaporate fully before taking locally created polymers into use. [There is not much benefit in having a free shield from cosmic rays, if you end up getting cancer anyway due to chemical exposure.]

Power sources and storage

Solar cells should be possible to use even in the middle cloud layer; although less light is available than at launch altitude or orbit, daylight is so diffuse that solar panels would work oriented in any direction, even downwards. The drifter day cycle means that collected solar power must be either stored for use during the 50 hour night, or an alternative power source must be found that works without daylight.

Electrical batteries will definitely be used, they are convenient and well known technology that works well with electronics, radio and lights. But there are other means of storing power than batteries. One storage alternative could be compressed air (of suitable color), something that may anyway be necessary to store reserve lifting gases. Pressure tanks may also be easier to manufacture locally than efficient electrical batteries, and can be made without rare metals.

Stored compressed air does not always need to be turned into electricity: compressed air can for example be vented via a Coandă thruster to propel or turn the ship. Pneumatic motors are possible to make without metals or magnets or electric hazards, and their operation is based on air-tight seals and gas pressure; familiar concepts when living inside an airship. But some way to create compressed air is needed to run pneumatic motors. Outside of manually powered pumps [which should be considered as a backup system in case electrical power fails] or phase-change engines, this means electrical pumps running on solar power.

An added bonus of compressed air as a power source is that venting compressed air actually removes heat. Surrounding a pressure tank with a heat exchanger and a heat pump could be utilised in directly cooling blue areas, even if the tanks themselves are kept outside in the yellow areas for safety.

Other than solar panels and cloud harvesting, energy collection from the environment may require long-winded equipment, to utilize the natural differentials of different altitudes. A kite sail could be floated a few kilometers above the ship, or a turbine dragged a few kilometers below the ship, to collect power from the difference in wind speed. A more complex “cable” might be able to use “aerothermal energy”, in the same way that geothermal energy is pumped from below ground on Earth. Any system with long cables or pipes is also vulnerable to the buildup of static electrical charges. [If they can be safely utilized, why not just harvest lightning directly?]

It is unlikely that the pressure differential between altitudes can be siphoned, even with a long capillary tube. But if pressure tanks are easy to manufacture, it might be possible to let nature fill them one by one: drop them down with a mechanism that closes their valve when a predetermined ambient temperature is reached, and inflates an accordion bellows balloon that slowly lifts the tank back up. There are disadvantages to this scheme that may hurt overall efficiency, but the method can also be justified with collecting air samples from different altitudes for scientific purposes.

Navigation and communication

The visibility in the cloud layers is probably not good enough to navigate accurately by sight. Even if a mythical Viking sunstone would show the Sun behind the clouds, placing the horizon would still be guesswork. Flying in colony altitudes will depend on instruments even during the day.

This is not that dangerous for a fleet of drifters within a few kilometers of each other, all passively sailing along the same winds. Visibility should extend that far, and light beacons should be required on all ships, even during the day [of course radio beacons will also be required on all ships, with ship identifications]. Flyer type ships however are much faster, and at superrotation speeds travel to the edge of visibility in seconds. A supersonic rocket is effectively blind in the cloud layers, and must rely on other wavelengths.

Knowing exactly where you are and what direction you are facing is also important if you need to send data to an object in orbit, or any kind of tight beam communication inside the cloud layer. On Earth, geopositioning systems work by broadcasting a simple time signal from multiple satellites. This setup is possible on Venus as well, but needs to be set up in advance. The intelligence is at the receiving end, where the periodic time signals from the satellites are analyzed to arrive at an estimated coordinate. Translation from satellite time signals to Venus surface coordinates will require calibration with another positioning method, preferably triangulated from multiple ships.

A viable positioning method that works without satellites, surface beacons or other ships is radar surface feature recognition. A computer machine learning system trained on mappings from previous missions should be able to correlate radar data to surface coordinates with good accuracy. With a high-resolution radar, it may become the standard against which other positioning systems will be calibrated.

A fleet of ships drifting within line of sight distance to each other is a fairly safe place to live in terms of navigation. [Not all of them need to be manned ships.] Constantly broadcasting your ship identity and positioning coordinates to surrounding ships makes it easier to model not just the position of all ships, but also the pitch, roll, and yaw of your own ship in relation to multiple lines of sight.

Flying in air makes sound-based communication between ships possible. This is mainly a curiosity, but does bring a nice human element to life on Venus. A passive drifter is itself fairly silent, compared to flyers and multicopter drones. Silent ships changing altitude is a potential hazard to nearby ships, and could be accompanied with alarm beeps, like a truck reversing on Earth. And of course there is the possibility of noisy neighbor airships, with their uninsulated envelopes vibrating to the music playing inside. [There may even exist natural noises on Venus. Even though lightning has so not been positively confirmed on Venus, there have been indications of thunder-like noises propagating in the atmosphere. Maybe someone alive today will become the first human to hear thunder on another planet?]

Venus will have its own data communication network, of course. Venus ships will produce a lot of data themselves, which is beneficial to store in a replicated, distributed way among the fleet of ships. The distributed cloud [yes, this will be the first cloud system with a literal cloud layer] could also host any data caching or mirroring from other planets, with priority-coordinated access to the high-latency interplanetary data links. To enable efficient data distribution, the antenna systems on board each ship must be capable of detecting and tracking the beacon signals of nearby ships, and directing their higher frequencies at each other for maximum bandwidth [somewhat like 3DBF in 5G]. Most of the equipment for the computer network must come from Earth for the foreseeable future; offline bulk data storage media [optical or chemical rather than magnetic due to rareness of magnetic raw materials] is a possible first candidate for local manufacture.

Some assembly required

Dropping into the atmosphere from space limits the possible size and shape of individual airships sent to Venus. Much larger structures become possible if assembly can take place at colony altitude. And even if a colony consists of multiple smaller ships floating close to each other, they will need to transfer materials and people between ships from time to time. A modular design, standardized across the fleet [like ISO containers] is highly desirable.

Doing construction or assembly that hangs downwards is completely opposite of most construction done on Earth. Only nests built by birds and flying insects are examples of hanging-in-air construction. Is it even possible to combine modularity, lightweight construction, and airtight seals between different colored airs, while hanging down from balloons?

This sketch concept uses a rectangular rigid module constructed of straight lengths of rods or pipes, arranged in an interlaced pattern, like wicker or a bird’s nest, that distributes mechanical forces in all directions. The design is rotationally symmetric, which means that two modules can interlock facing any of its six faces towards each other, to ease assembly and design.

In the interior of each cubic module is an open space, roughly spherical [unofficially called “egg space”, continuing the bird’s nest analogy], where different payloads can be attached and carried. The exposed rods of the frame provide both support for the inner payload and anchoring for hauling the module from the outside, or for attaching various equipment. The open frame can also be reinforced where needed, even replace the payload completely with structural elements for some modules in the assembly.

Blue quarters for habitation can be built inside module frames, and be connected with flexible or inflatable corridors. Rooms can also be erected using only inflatable elements attached to the module frame. Slightly overpressured wall elements could be useful in keeping blue and yellow air separate, or detecting leaks. For more permanent construction, instead of gas the wall elements could be injected with an aerosolized resin that hardens into a foam. This results in less “bouncy castle” feel, adds insulation from outside heat, and avoids having to adjust inside-wall pressure when the altitude changes.

What next?

So far colonization of Venus has been a thought experiment, what current technology might allow given what we know about the conditions on Venus. But there is a lot that needs to happen before we can send the first humans to live on Venus.

Local weather is crucial to flyers and drifters in the cloud layer. We have studied what we can from looking at the cloud patterns, but it would be prudent to send more unmanned missions to study aspects of weather (including electrical aspects, thunder and/or lightning, and radio weather) first-hand. Detailed chemical composition of the more hidden cloud layers could be studied at the same time, not just for their interaction with manmade ships, but also to ensure that there are no naturally occurring complex macromolecules or processes that human colonization might contaminate.

Even if volunteers might be available, it would not be ethical to send humans to Venus if there is no feasible way for them to return. There have been designs for air-based launches from Earth, but so far all missions with humans on board have been launched from the ground. Launching from a high-altitude balloon would save rocket fuel on Earth too, so it makes sense to mature the technology here first. [There are some entrepreneurs working in this area, for example zero2infinity with bloostar.]

Despite the obvious differences, many of the challenges of Venus airborne colonization are the same as those of Moon or Mars ground-based colonization. All are behind gravity wells, so equipment shipped over must be both lightweight and built to last. All will need reliable systems for blue air management, as well as medical diagnosis and treatment. Photovoltaics and battery technology is needed for all destinations, as are advanced automation and robotics. Developing these space technologies will also help Venus colonization.

Different airship models can be tested and developed in Earth’s atmosphere first, before modifying them for Venus. Unfortunately there doesn’t seem to be much interest in long-duration unaided flight on Earth to drive the needed technical development on its own. Currently the record duration for untethered airship flight is 20 days, from 1999. For successful Venus colonization, flight durations should be counted in months and years, not days. [The 1999 record was not even the primary goal of the mission; it was to circumnavigate the globe without landing.]

And even if it suddenly became fashionable to make floating cities on Earth, they would be much easier to assemble on the ground than in air. Even if it is technically possible to build floating cities on Earth, there is no real economic incentive to play “floor is lava” during their construction. But such games need to played here at least part of the time, to gain the practical knowledge and skills needed for sustainable Venus airborne colonization.

Terminology

airborne: English word meaning “carried by air”

ballonet: adjustable non-lifting gas bag inside the outer envelope of some airships

ballute: fusion of “balloon” and “parachute”

catenary curtain: a load-distributing internal cable attachment in some airships

envelope: airship jargon for “gas bag”

kytoon: fusion of “kite” and “balloon”

LTA: contraction of “lighter-than-air”

metastable: loading a surface ship with its center of buoyancy below the center of gravity

pH: “power of Hydrogen”, a logarithmic measure of ion concentration in a solution

rockoon: fusion of “rocket” and “balloon”

self-trimming: a mechanism that helps keep cargo evenly loaded on a ship

static port: external air sensor fitting on an aircraft

superrotation: the rotation of Venus’s atmosphere, faster than surface rotation

trimming: in this context, keeping a ship level

History

The earliest mention of using buoyant airships on Venus I have found is in The Exploration of The Solar System by Felix Godwin (New York, Plenum Press, 1960). [This charmingly detailed but outdated book is otherwise an excellent example of smart and imaginative extrapolation from insufficient data.]

“(21) The non-rigid airship is for some purposes the ideal form of transportation on Venus. Owing to the dense air, it can carry considerable loads. Furthermore, it is completely unrestricted by the terrain and can hover anywhere, either for observation or for discharging cargo.” [pg 86.]

Once data about the harsh surface conditions started to come in from the early missions, the idea of sending buoyant vehicles into the atmosphere of Venus gained more traction. Many countries had plans for putting scientific aerostats on Venus in the 1960s. For example in 1967 Martin Marietta Corporation made a feasibility study for NASA of a Buoyant Venus Station (BVS), considering payload masses of 90 kg, 907 kg, and 2268 kg.

Two aerostats (21 kg each) were eventually launched into the middle cloud layer in 1985, as part of VEGA. The multinational mission was a success, and radio telemetry from the helium-filled balloons was tracked for 46 hours from 20 radio telescopes around the Earth. French scientist J. E. Blamont is credited with the original proposal.

Manned missions on dirigible airships were also discussed. In issue 9/1969 of Tekhnika Molodezhi (“Technique – Youth”), pg 14-16, V. Ivanov writes

“In fact, above the inhospitable surface of Venus, it is very convenient to drift in a dense atmosphere. In addition to devices such as bathyscaphe, it is advisable to launch balloon-probes or even airships to our heavenly neighbor. For example, a small balloon probe, drifting at a height of fifty kilometers, is capable of transmitting data on its way, about the downstream terrain for many days in a row. Perhaps relatively quickly people will create in the upper layers of the atmosphere of Venus a drifting laboratory that will prove to be more effective than a manned artificial satellite of the planet.” [translated from Russian by Google Translate]

The idea of dredging the surface of Venus from a buoyant ship with a long cable was also floated. In Aviatsiya i Kosmonavtika (“Aviation and Astronautics”) 10/1973, pg 34-35, G. Moskalenko writes

“The aerostatic type device can be equipped with a cable hanging downwards with research equipment suspended for it for vertical sounding of the atmosphere, as well as mechanisms for taking ground from the surface. The length of the rope is not difficult to increase due to the attachment of intermediate lifting balls, which compensate for the load on the rope. It is interesting to note that by picking up the appropriate lifting balls, the cable can easily be lifted above the bearing balloon.” [translated from Russian by Google Translate]

The futuristic idea of living permanently on Venus in large floating habitats also emerged early on. In issue 9/1971 of Tekhnika Molodezhi, pg 55, S. Zhitomirsky writes:

“[…]the composition of the Venusian atmosphere suggests a more tempting solution – the station can be inside the balloon. Indeed, carbon dioxide is one and a half times heavier than air, and a light shell containing air will float in a carbon dioxide atmosphere. If the inhabitants of Venus prefer not a nitrogen-oxygen but a helium-oxygen mixture for breathing, the lifting force of their “air” will sharply increase. […] To the edges of the platform is attached a huge spherical shell, which limits the airspace of the island. It is transparent, and through it you can see the whitish sky of Venus, eternally covered with multilayered luminous clouds. The shell is made of several layers of synthetic film. Between them, gas formulations containing indicator substances are circulating.” [translated from Russian by Google Translate]

[As the zonal wind speeds were apparently unknown at the time, Zhitomirsky assumed that the flying islands can move at about 13 km/h to stay constantly in daylight. The actual airspeed required to do that outside of polar regions is actually 20-30 times higher, infeasible for a ship that big.]

Links

Venus colonization has its fans [“Friends of Fria”, as Peter Kokh called them], but finding relevant discussion about the topic can be frustrating. [For example, the domain name venussociety.org is reserved, but has no content at this time.] I can recommend two links which both have pointers to deeper sources:

This 2011 article By Robert Walker presents a friendly introduction to the topic, and also a source of links to further discussions on various internet forums: “Will We Build Colonies That Float Over Venus Like Buckminster Fuller’s Cloud Nine?”

Venus Labs has published a highly detailed “Handbook For the Development Of Venus”, Rethinking Our Sister Planet, written by Karen R. Pease. The book is a seriously detailed imagining of how a manned mission might be accomplished with existing technology. It has lots of links and sources of information. [There are a lot of original ideas in the book as well, but I can’t say that I completely agree with all the proposals. One thing that strikes me particularly is the insistence of housing people high inside the balloon envelope, even doing bungee jumps while hanging from the ceiling. To me it sounds a bit like the wild stunts of wing walkers playing tennis on the wings of biplane in the 1920s: it is perhaps possible but very risky and uncomfortable, and ultimately has nothing to do with the primary engineering purpose of wings or balloons.]