In the last post in this series, we discussed methods for gas phase processing once the easily condenseable atmospheric constituents had been condensed-out. Before continuing on to a discussion about various processes for creating chemical precursors, I thought it would be useful to discuss various phases of Venusian ISRU development, with increasing levels of sophistication. This will help provide some context to further discussions.
Phase 0–Terrestrial Analog ISRU Prototyping: This is where we’re at now. As far as I know there has been almost no experimental development of the sort that some of our commenter have suggested which would use simulated Venusian atmosphere to attempt various approaches for extracting the different constituents for further processing. Obviously that which hasn’t even been tried in the lab is nowhere near ready to try in situ. This stage will likely be characterized by small, non-flight like, breadboard/brassboard-level prototype processes.
Phase 1–Venus In-Situ Demonstration: The first real Venus ISRU development phase will likely be in the form of small experiments mounted on robotic atmospheric balloons. We’re likely talking about experimental apparatus of less than 200kg, which are not so much focused on producing large masses of extracted materials, but just demonstrating and validating basic extraction processes. These steps will likely be focused on the concepts we’ve talked about so far of condensing out and separating condenseable species, and processing the atmospheric species to remove key hazardous materials, to demonstrate the ability to extract safe feedstocks for future larger-scale processes.
Phase 2–In-Situ Propellant Production and ECLSS Revitalization: This is the point at which the first steps beyond what we’ve already discussed will be taken. This phase may start with unmanned systems, demonstrating the ability to refuel rocket stages for transportation back into Venus orbit, and to provide fuel for Venus orbit propellant depots. But this phase will likely also include demonstration of the ability to revitalize the breathing air and drinking water for manned missions. This may also include trying to create enough lighter-than-CO2 gas to provide buoyancy for the robotic and manned systems. This stage isn’t necessarily about creating voluminous open habitat spaces and floating cities. Depending on the rocket approach taken for transportation between the cloud level and orbit, this could involve processing hundreds of tonnes of atmosphere into propellants, and tens of tons into lifting gasses and life support elements. At this point most chemical processing will be limited to that necessary to create propellants. Depending on what propulsion style makes the most sense, this could be LOX/LH2, LOX/Methane, or LH2 or Ammonia for nuclear thermal, solar/microwave thermal, or solar/laser thermal propulsion systems. These can mostly be created by simple one or two step processes from the basic atmospheric constituents previously discussed.
Phase 3–Small Settlements: At this phase, permanent settlements are first being attempted. So in addition to processing the atmosphere to create propellants for flights in and out of the Venusian atmosphere, and creating lifting gasses for supporting those smaller facilities, we’ll now be talking about creating large amounts of breathable air and water for filling these colonies. Also this phase will likely include the creation of simple construction materials to try and reduce the amount of material that needs to be shipped from earth. This will likely start requiring taking the initial chemical feedstocks and performing several processes to create materials such as carbon fiber, simple polymers, and sulfurcrete. These materials would be used for the structure of the settlements, and possibly even the atmospheric barrier film. This phase will be focused on the low-hanging fruit of materials that would require the most shipping mass from earth, but that are easiest to produce on Venus. Peter Kokh had some clever acronym for this for lunar ISRU, but I’m forgetting it at the moment. But basically, the more processing steps necessary to get to an object, the more likely it would be best to still import this from earth.
Phase 4–Advanced Settlements: At this phase large-scale permanent settlements will exist, and even some limited mining of the surface of Venus will likely have started. As this phase progresses, more and more materials of increasing complexity will be sourced locally, including some simpler metals, and more advanced plastics and composites. As this phase continues imported materials will focus on high-value hard-to-manufacture items like advanced electronics, complex machinery, etc. I think this Phase while interesting is probably beyond the scope of this series. If we get to this phase, we’ve “already won”.
Next Up: Basic Chemical Precursors for ISRU Development Phases 2 and 3
Jonathan Goff
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What this Venus colony scheme needs to work is a Venus co-orbital asteroid. Earth (or more likely Moon) won’t keep sending resources unless they expect something back, and it’s hard to imagine what those floating cities would have that anyone would want.
The asteroid would need to be big enough to supply tons and tons and tons of iron and phosphorus and many something-iums, but be unable to support to a colony of its own. (Maybe it’s too close to the Sun to keep any water.) Such asteroids probably exist, but we’ll need a survey telescope inside the orbit if Venus to find them.
As an aside, I think an interesting research project would be the study of corrosion of various popular terrestrial materials to see how they hold up under various possible conditions on Venus at different altitudes. Maybe a glass lined pressure chamber able to handle pressures and temperatures from near vacuum to the base of Venus’s atmosphere. One could also add intense UV light sources or ion bombardment to see if these inputs makes things more difficult.
Then see how long materials last, how they fail, and what the resulting damage looks like.
Karl,
Strongly agreed. I was thinking that last night as well. One of the key questions is the material forming the gas barrier between the habitat/blimp section and the outside atmosphere. I was originally thinking only Teflon would do, but am now seeing more and more data suggesting that properly treated Polyethylene might do (they use various types of PE for most Sulfuric Acid containers on earth). That would obviously be tons better because PE is much easier to make in quantity than PTFE due to the scarcity of Fluorine on Venus. So having some sort of atmospheric test chamber would be good not just for testing ISRU stuff like George was suggesting, but also for testing material durability.
~Jon
I’ve thought of a couple stumbling blocks, or challenges, with operating the airships.
It doesn’t make much sense to have a single airship performing all the individual processing tasks because then the airship would have to be loaded with just about every piece of imaginable equipment. I would think different airships would have common core functions like making lifting gas, breathable air, power, and water, and then specialize from there into making various chemicals, plastics, etc.
This means that the airships will frequently have to rendezvous and perform material transfers, and airships are rather fragile and unwieldy craft to navigate in close proximity in a potentially turbulent atmosphere. This might be especially true of robotic craft operated from Earth with a very long communications delay.
I think having one airship move above a second one while maintaining a safe altitude separation and then lowering a hose or material via a hoist might be simpler than trying to rendezvous horizontally, but I’m not sure. The tops of airships would probably be delicate and you wouldn’t want to risk ripping through with a dangling hose or a pallet of barrels. Their bottoms are tougher, but raising materials from the lower airship would require a very rigid structure.
Perhaps the could extend a fabric tube that’s stiffened by positive pressure, which then makes a hard seal with a docking ring on the other ship?
Basically, what’s the easiest way for a guy on one Goodyear blimp to pass a turkey sandwich to a guy on another Goodyear blimp? How could a person get from one blimp to another? There’s probably an elegant solution to the problem, but it certainly hasn’t occurred to me yet.
The Navy refuels at sea all the time in very turbulent conditions. The US does it with ships running parallel while the Brits do it with one ship trailing another. I would think there could be a mother ship with smaller, less critical if they collide, barges that do the actual transfer.
The trouble is that even in the simplified two-dimensional case of being on the ocean, collisions during replenishment are still frequent. The USS Yukon has suffered three serious collisions, the latest last year, and navy ships are built much tougher than airships. The current methods rely on a lot of crewmen and very experienced helmsmen who can deal with the cable tension pulling the ships together, along with the hydrodynamic forces generated between two ships in close proximity. For airships, those problem might be worse and an actual collision might due catastrophic damage.
I did find an interesting mathematical study of the problem from 1973 which might serve as a starting point, or we need to think out of the box and come up with something better.
George,
I’m not sure if your assumptions are right here. Do the airships need to be really fragile? I would imagine with a big open structure you could probably design things to take collisions safely. Also, you seem to assume that the airships will be just balloon at the top…why? I think it would be pretty straightforward to build a solid platform at the top to enable vertical docking. Plus, you also forget you’re commenting on the blog of Mr Sticky Boom. I’m sure these problems are solvable.
The problem is I don’t think you’ll be able to solve them without a lot more detail on how these systems are built. It’s definitely worth looking into, but I’m not too worried. Probably a good topic for a different blog post series.
~Jon
Okay, I was just chatting with a Navy veteran who has done a lot of underway replenishment, and he says it takes about 100 men, 50 on each ship, and went into some detail. So after some discussion, the better plan is this:
The receiving airship moves above the supplying airship and drops a line. The supplying airship (the one underneath) takes the line and attaches it to a pallet that’s sitting on a hard point (a hardened deck surface), probably at the stern of the ship. Then the receiving ship lags back and rapidly winches up the cable so that there’s no risk of the payload colliding with the supplying ship.
This way there’s never a heavy payload swinging freely toward an airship on the end of a long cable, which is risky. Instead the heavy payload is always moving away from the airship, and by the time the payload approaches the receiving ship the cable is obviously very short and the payload is entering a hard hanger, so no risk on either end. By having the operation done from the stern of the lower, supplying ship, the payload can swing aft of the lower ship so that if the payload breaks free, it will fall behind the lower ship.
As for grabbing the free end of the dangling cable, if it’s end has a small balloon or parachute attached and the lower, supplying airship’s transfer point uses a suction device (an exhaust or propulsive fan acting as a giant shop-vac), it will suck the end of the cable into the desired location, perhaps allowing the whole task to be fully automated so you don’t have to have a guy in a breathing mask running around on deck trying to grab a cable that’s whipping around in the wind.
And of course once the light weight cable is between the two ships, they could send a hose across using the cable as a guide, for liquid or gas transfer in either direction.
As an aside, if one wants to dock airships, I think Jon’s business has ideas along those lines that would work fairly well for airships.
Okay, moving on from the docking/transfer issues, I have an early phase 1 or phase 2 application that would involve a science mission to piggyback on the ISRU goals. The mission would be to analyze rock samples using sophisticated equipment that wouldn’t easily survive on the surface, and certainly not for long.
So simple samplers plunge to the surface, grab some samples, and then deploy a balloon to float back up to altitude. Then the ISRU/science airship starts a long chase to rendezvous with each balloon and retrieve whatever surface rocks have been recovered. The scientific instruments on the airship could be based largely on the analysis instruments on the Mars Curiosity rover or other vehicles, with the addition of radioactive dating so we can figure out exactly when Venus went through its resurfacing, instead of estimates based on impact crater patterns.
Since the balloon chases might be long, the airship is going to have to be solar powered for endurance. To maximize the scientific payoff, it would be best if the samplers were reusable, which would require recompressing the lifting gas for a new descent, along with recharging any on-board high-temperature batteries, and possibly creating a cryogenic gas for short term cooling of the sampler on the surface.
If the surface probe and balloon weighed 100 kg, they would need 178 kg of N2 or 10 kg of helium to get it back to altitude. If the probe requires cryogenic gas as a coolant, which would be expended during the surface stay, then that needs to be replenished. If making the lifting gas and cryogenics in the upper atmosphere reduces the total launch mass of the mission (given the number of surface probes being supported) then the ISRU component becomes a beneficial part of the mission with immediate payoff.
By reusing the surface samplers, the mission could collect data from far more of the Venusian surface than even the Mars rovers can, because by riding the high altitude winds the entire planet becomes equally accessible. If the airship proves to have a long service life, further enhanced sampling missions would only require launching new surface probes from Earth, whereas upgraded scientific instrument packages, sent on new airships, could service all the existing surface probes.
I had pictured the airships (later versions that do the actual air mining) to be quite large, dwarfing the Hindenburg. Each would have a docking port for the barges to transfer material between ships. They would ride around 170K feet (52km) keeping internal pressure @ 1 atm. Much like deep water drilling you could send down divers on smaller vessels to operate the UAV’s and other mining equipment, atmosphere and turkey processing equipment would be on the main ship.
What I didn’t realize was you can place the solar panels anywhere and receive sunlight due to the albedo of the clouds.
They would ride around 170K feet (52km) keeping internal pressure @ 1 atm.
I think it’s best to keep internal pressure close to external pressure which your airship pretty much does. Some modest overpressure would be useful to maintain structural integrity, but it does sacrifice lifting capacity.
Great to find these posts. Have just started to read them, lot’s of interesting ideas. You might like my section on Venus colonization in my blog here:
http://www.science20.com/robert_inventor/trouble_terraforming_mars-126407#comment-171072
Anyway do you all know about the Venus Society? See http://www.linkedin.com/groups/Venus-Society-4897138
I’ve linked to this discussion from my post as well and mentoned you on the Venus society. Found this blog through the discussion of my article here:
http://james-nicoll.livejournal.com/4752162.html
One thing that is of great interest I think is the possibility of life in the Venus clouds. First that it might be there already – because
*Venus prob. was habitable in past and residence time of dust in atmosphere is months rather than days
*Measurements that suggest there are particles there that are just the right size for life, and non spherical
* Evidence of OCS (Carbonyl Sulfide) which on Earth would be an unambiguous indicator of life.
http://www.examiner.com/article/could-life-exist-venus-atmosphere
So – if there is life, could tell us a lot especially if evolved independently of Earth – and – with such harsh conditions on surface of Venus- seems unlikely that it would be easy to seed Venus with Earth life via meteorite. So any life in the clouds has probably evolved independently for billions of years since Venus last had an ocean. And may be indigenous originated there.
If that’s so then we might need to be careful not to introduce Earth life until we have studied it properly to see what it is, find out how it works. Might well not be just one species but a complex ecosystem of micro-organisms.
That then is something for early non inhabited probes to explore.
Then – if there is no life there, then we can start thinking about colonizing, and might even think about introducing life to the clouds ourselves. Though we wouldn’t know what would happen, unlike Mars doesn’t seem that much that could go hugely wrong as a result of introducing new life to it ??
If there is life there though, I think need to pause and take stock of the situation and decide what to do next. Still can explore with humans in orbit and via telepresence to the orbital habs in the atmosphere as well as to the surface.
@Robert Walker.
Those links were very interesting! In reading some of the threads, I learned that silane (SiH4) might make a useful fuel, since it’s hypergolic with CO2. You probably couldn’t pull up a Venus rock sample that wasn’t chock full of silicon, which is useful for solar cells, glass, SiAlON, silicon carbide, and silicon nitride. If silane can be used as a fuel, you could also make air breathing engines for Venus. The fuel mass would be four times that of a hydrocarbon oxygen-breathing engine on Earth for the same energy output, but only half the mass of carrying both a hydrocarbon and oxygen. On the downside, silane is toxic and hypergolic with CO2, so I’m not sure you’d want much of it around.
Anyway, I’ve been wondering about the all important step of having an airship replicate itself.
I’m thinking that the parent airship automatically extrudes and glues together a thin balloon shaped like the final daughter airship in a process similar to automated sail or balloon construction. A module containing ISRU equipment is added, and then the balloon is inflated (or dropped free to inflate on the way down).
The daughter airship starts out as a very thin balloon, but spends all its time thickening its skin and reinforcing itself, shifting to lighter and lighter lifting gas mix to compensate for the added mass it’s pulling out of the atmosphere and turning into carbon fiber, plastics, and other materials, basically building its structure in a 3-D printing process.
Aside:
Interesting to see in miniature the sort of arguments I see in comparing Mars colonisation (a near-Earth planet, man’s second home) with asteroid mining (zero g! space dust! radiation! z0mg!). Surface sampling (descending into hell, then getting back) is “simple”, but docking two airships? Boy howdy, that’s a toughy.
The more we understand the details of problems, the harder something seems. The less we understand them, the easier it is to handwave them away.
Michael Welford pointed out a macroeconomic issue that looms large for many impoverished “colonies” on Earth: “It’s hard to imagine what those floating cities would have that anyone would want.” I submit this answer: Carbon, nitrogen, and the energy to ship it around the solar system. Venus air-colonies need more than high-tech goods from the rest of the solar system, they need hydrogen, because Venus is hydrogen-poor.
With hydrogen imports, air-colonies can render atmospheric CO2 directly into H2O with elemental carbon leftover. George Turned mentioned silane, which can be made from surface rock and imported hydrogen. Another chemical reaction with hydrogen converts atmospheric N2 into ammonia, which can itself be reacted with atmospheric sulfuric acid to produce ammonium sulfate, a fertilizer for floating farms. Elemental carbon can be used to make lightweight/highstrength carbon allotropes for the structure of air-colonies, their electronics, spaceplanes, etc. But it can also be shipped off-world as spools of space-elevator fiber or left in its elemental form for shipment to carbon-poor worlds.
The term “shipment” implies vast amounts of energy but Venus air-colonies have access to just that. Consider:
-Orbit has @twice the solar flux as Earth orbit for solar power and sail propulsion.
-Air-colonies above the clouds do not have cloudy days.
-Albedo; panels will generate 90% power from their reverse side.
-Superrotation (and density) of the atmosphere for wind power.
-The Oberth effect makes shipping around the solar system inherently cheaper.
Its a potent economic plan. With access to a sufficient quantity of hydrogen and self-reproducing airships, Venus can even be terraformed using this chemistry. With the bulk of the atmosphere (all the CO2) transformed into an ocean, the remaining 3 bars of N2 atmosphere will find itself divided in the following places:
-Dissolved into the new ocean.
-Turned to large amounts of fertilizer for mass-production of soil.
-Part of a the new nitrogen-cycle of the new biosphere.
-Allowed to remain as a buffer-gas in the atmosphere.
-Shipped to Mars and other nitrogen-poor worlds.
But that is rather beyond the scope of the present discussion.
In response to fireflower’s answer: “Carbon, nitrogen, and the energy to ship it around the solar system. ”
How can Venus supply these better than Earth? The gravity well is about the same, but anything leaving Earth can get a gravity assist from the Moon. Producing these on Earth is easier, as nothing needs to be moved.
Currently the reasons to settle Venus are scientific; an economic angle remains to be found.
Question which is bugging me about a Venusian colony:
At what latitude are you planning to place it?
If you go sufficiently north to have access to the Maxwell Montes, then you will be in the Polar collars – with temperatures about 30–40 K lower but clouds about 5KM higher than in more southerly latitudes. To my very limited knowledge, this seems a good choice, but means a slightly different situation to that normally described.
Further north (or the extreme south) seems out of the question thanks to the polar vortices: ultra hot cyclones are not going to be fun.
Further south in the Hadley cells lets you explore, from near the equator to about 60° North or South, depending on which one you are in: but explore what, and which do you chose? The surface is basically plains studded with volcanoes in both hemispheres; a few of the volcanoes might be high enough to make mining/exploration less stressful for machinery I guess.
I know nothing of the situation on the equator, so default to what I’ve read about sailing on our own equator – which boils down to the advice “Don’t”. Thor Heyerdahl in particular when talking about the possibility of crossing the Pacific at the equator regarded the idea as insane, and this is a guy who crossed one ocean on balsa wood and another on reeds. That’s a shame, as it’s also the location of Aphrodite Terra.