Mission to Venus

elderflower · 2018-10-24 04:07:15

Douglas Adams has already done the Whale in space scenario. You are forestalled, Void!

Void · 2018-10-24 12:36:49

Quote:

Douglas Adams has already done the Whale in space scenario. You are forestalled, Void!

Actually very useful elderflower! Had to jog my memory by looking it up on the internet. Then I remembered reading it.

https://en.wikipedia.org/wiki/Speed_skydiving
Quote:

In stable, belly-to-earth position, terminal velocity is about 200 km/h (120 mph).

(For a human).

The whale would probably do worse I would think as it's mass to surface area ratio is less favorable.

So, if we consider the results dropping the whale from a height on Earth, and compare that to dropping a whale from a height on Venus, and ignore all the other unpleasant things that would happen to the whale because Venus is Venus. The whale might do better on Venus.

Venus has ~91% the gravity of Earth, and ~92 x the atmospheric pressure at the surface. This has to favor the results for the whale if only considering the splat factor.

Of course I am considering replacing the whale with a Mecha, where the mass to surface area ratio can presumably be made sensible to the survival of the device. Further I am considering putting aerodynamic features on the Mecha, so that it could glide, or autorotate to the surface. Autorotate would be like a helicopter blade. Further if needed, the helicopter blades could also be rotons. You might push liquid Nitrogen into hollow blades, and they would act like heat exchangers, and vent the propulsive exhaust from nozzles on the ends of the blades. Then this would be a powered landing. Alternately you might do something like the space shuttle, and do a controlled stall on landing. So methods to bring the Mecha to the surface undamaged are conceivable, even though in the down drop it would not be a lighter than air aircraft.

If the Mecha has arms and legs then they can be activated similarly to the rotons, you would push liquid Nitrogen into them and if the design were appropriate, these could activate the arms and legs pneumatically.

The core of the Mecha, however would be insulated to reduce the vaporization of dry ice and liquid Nitrogen, hopefully prolonging the time that the device could stay on the surface. While I have proposed using Liquid Nitrogen to activate the arms and legs, it is possible that liquid CO2 could be used. As the dry ice warmed up, at the ambient pressures of the surface, the CO2 would liquify before turning to vapor.

The method to retrieve the Mecha to higher altitudes, would perhaps be for it to become lighter than Venus air. To assist the lift, if you had rotons, and some cold fluids left, you could power the rotons to provide lift as well.

……

And then I have provided a Sulfuric Acid tolerant elevator chamber that the Mecha can be envelope into and so to lift it from the bottom of the Sulfuric Acid Mists and clouds, and up above them.

……

I am guessing the deployment method would be to have the Mecha in the elevator, and that assembly attached to a greater floatation device, above the clouds. You would load both the Mecha and the elevators with ballasts of dry ice and Liquid Nitrogen. You would unclamp the assembly to drop it. It would drop through the Sulfuric acid layers rapidly, but if balanced correctly it would stop at some height before striking the ground. Then the Elevator would drop the Mecha, and it would float up to just below the clouds to wait for the Mecha to come back up.

And then of course the desire is for it to pick up the Mecha and bring it up to above the clouds.

Very helpful elderflower!

Done

Last edited by Void (2018-10-24 12:57:07)

Belter · 2018-10-24 14:34:09

I wonder what would be terminal velocity at about 1250 PSI.

Belter · 2018-10-24 14:37:47

Apparently it's around 30mph more or less. One could probably make something designed to fall slowly enough to survive, collect samples, then float up with a balloon. No need for rockets. Replace balloon, resend.

Void · 2018-10-24 14:57:18

That is a way.

I myself envision that most likely the thing could float if it was not ballasted down by Dry Ice and Liquid Nitrogen. That is if it had a large volume you could fill with Nitrogen. I anticipate that it would be designed to level out at the 10 bar plus level just below the clouds and mists.

In order to bring up ore though it would have to be built with extra lifting capacity.

The dry ice at 92 bars could become liquid as it warmed up.
https://www.bing.com/search?q=Carbon+Di … c24075a21a
Melting point: -69.88°F (-56.60°C)
But I believe it has to be at a pressure of at least 5.1 bar to become a liquid.

After it became a liquid, as it vaporized, the vapors would have to be vented.
As the "Ballast" of dry ice diminished, it would be wise to bring ore on board to keep the ballasting as it needs to be to keep the device on the surface.

When you had as much ore as you might carry up to the 10 bar+ level, you could squirt the liquid CO2 out of the device to reduce ballast, and as it lightened up then it would eventually become airborne. You could continue to expel liquid CO2 to get to the 10 Bar+ level.

Then the elevator snatches it and the elevator spews out it's liquid CO2, to get lift to go through the Sulfuric Acid layers and above them.

Of course it has to be calculated properly. You could not afford to take too much ore with you. Perhaps in emergencies, the ore could be dumped in parts as needed.

Or you could use a roton blade powered by Nitrogen steam, to lift upwards. However I do not at this time favor that.

But yes, perhaps some kind of deployable balloon can be explored as well.

Done.

Last edited by Void (2018-10-24 14:58:38)

Belter · 2018-10-24 19:07:39

Why not used compressed liquid CO2 or something like that to power a rotor while spilling out? Not sure that would get you 50km straight up but it might get you part way. I would imagine CO2 hitting 800 degrees almost instantly would generate quite a bit of force. The problem I see is a material that can survive the temperature and sulfuric acid, though I imagine something must exist.

SpaceNut · 2018-10-24 20:41:30

https://www.reddit.com/r/SpaceXLounge/c … usian_bfr/

I think I see what void is trying to create in freezing the gass used to make the blimp float as that should create a negative bouyancy to which would cause the blimp to sink into the atmosphere with a mass that when allowed to heat would cause the blimp to rise....

Buoyancy calculator

www.swansonphysics.com/fluids/buoyancy.pdf

here is the flying wing that another had proposed:
https://www.iflscience.com/technology/w … ever-lift/
http://www.blimpinfo.com/airships/incre … nus-skies/
http://orbitalvector.com/Venus/Venus%20 … SHIPS.html

This is related but for earth use:
https://gizmodo.com/the-aluminum-airshi … 1301320903

This company was trying to create a blimp that could reach orbit
http://www.blimpinfo.com/airships/can-g … aces-idea/

https://ntrs.nasa.gov/archive/nasa/casi … 010650.pdf
Airships 101: Rediscovering the Potential of Lighter-Than-Air (LTA)

More air ships
ctrf.ca/wp-content/uploads/2015/02/2014CTRF_S12_1_Regular.pdf

https://www.ocregister.com/2015/05/12/s … ts-patent/

Void · 2018-10-24 21:16:05

Yes Spacenut! The dry ice and liquid Nitrogen are ballast, coolant for sensitive equipment (Electronics, ect.), and once the dry ice has been converted to liquid CO2, yes Belter, motive force could be imposed by using the 92 bar hot air to provide propulsion. In fact I would think that if you pumped in 92 bar air at 864 degrees Fahrenheit (462 degrees Celsius), and mixed it with liquid CO2 in a confined space you would get significant expansion. Otherwise put the liquid CO2 through a heat exchanger to do the same.

As for the Liquid Nitrogen, it is there to motivate the legs, arms, and hands of the device to manipulate surface materials.

It is also there to purge out the body of the device. If you are using buoyancy, then the process would be to expel enough of the liquid CO2 to the exterior to make the device suitably light, and then purge the interior by heating liquid Nitrogen to a Nitrogen gas to fill the vehicle. The hope is to have sufficient buoyance to float upward. But if you still have some liquid CO2, you may use a propeller, or jet propulsion to go up even faster.

I intend to stop below the Sulfuric Acid clouds, so you perhaps would want to make sure you still had ballast to adjust to not going into the Sulfuric Acid. So to get to below the clouds, you would drop CO2 ballast, and if necessary some of the ore you gathered.

The pressure at this altitude would be about ~10 bars, so liquid CO2 could still exist.

Then the acid protected elevator joins with the Mecha, and envelopes it with a door closing. The Mecha expels any remaining liquid CO2 and Nitrogen it has before the door closes. Then the elevator expels its ballast of dry ice and/or liquid CO2 and the elevators buoyancy lifts the whole assembly to up above the cloud deck. Then the elevator connects to a large colony dome, locks on to it.

A time period follows where the device cools off. Then humans can service it either in a Nitrogen/Oxygen shirt sleeve environment, or in protective suits if the device is not purged of Venus air.

The Mecha and Elevator can be serviced, and reloaded with dry ice and liquid Nitrogen, and then the elevator is dropped. Due to ballast, I would expect it to fall quickly to the 10 bar level again. Then the Mecha is dropped from the elevator, and it will fall. In my version it might have the gliding aspects of the space shuttle, although at 92 bars it would not need to go very fast to "Plane" (I think).

Or you could have a helicopter blade like roton rocket assembly. Squirt liquid Nitrogen into the roton, and the roton would serve as a super heat exchanger, and as a helicopter, to land.

While I have done what I can to protect the Mecha from the Sulfuric Acid (Which does not more or less extend below 10 bars), I cannot promise that a hot mixture of CO2 and a little Nitrogen at 92 bars will not also be corrosive. But at least you only have to build the Mecha to tolerate that kind of a corrosive environment. You do not have to also make it tolerant of Sulfuric Acid. The elevator handles that.

But it is a half baked idea, and I like it that way at this point. Invent your own version. I would like that.
Done.

Last edited by Void (2018-10-24 21:22:28)

kbd512 · 2018-10-24 21:28:13

Belter wrote:

So what would be the use of people floating in cloud cities and how would that be different from floating in Earth orbit with 1G stations?

Development of technology to live in the clouds of Venus follows the same reasoning we're developing technology to live and work in space and on the surface of Mars. Principally, because we have the ability to do so, because technology development eventually benefits most of humanity (for those who decide living better lives is more important than killing each other or stealing from each other)- even if it doesn't benefit everyone equally at the same time, and because there will come a time when we have no choice but to seek out and live on new worlds. If we perfect the technology required now, then when we have no choice in the matter, we're significantly better prepared for future endeavors of the non-optional and non-trivial variety.

The difference between a cloud city on Venus and Earth orbital stations is that Earth's orbital environment requires significant pressurization, high velocity orbital debris protection, radiation protection, and Earth-like gravity without imparting substantial force on a highly pressurized module. The environment in the clouds of Venus within a specific altitude band is far more benign than the surface environment on Mars. It's very close to Earth gravity, no pressure suit is required, and it has Earth sea level radiation protection. None of that holds true on the surface of Mars. The technology required to simply go there and come back to Earth is the same variety as that required to go to Mars, just a less extreme version of it.

A minimum energy Hohmann transfer to Venus requires roughly 90 days of travel time. If you're willing to burn more propellant, then 60 days is still feasible with a reasonable payload fraction. The Venusian atmosphere has no problem at all with providing sufficient braking force during reentry. There's also no reason why SEP couldn't provide significantly more payload fraction for less cost. Within limits, as you get closer to the Sun the efficiency of solar panels goes up. Any array sized for Earth operations provides at least as much power at Venus.

Airbus Defense has a contract with Ascent Solar to develop long endurance high altitude drone airships powered by thin film solar panels.

Lockheed-Martin is working on an Airship that can deliver 1,100t worth of cargo between continents substantially cheaper and faster than an ocean going freighter using a computer-controlled hybrid-electric thrust-vectoring propulsion system. Their new airship uses an air cushion system to both cushion landing over a wide area to limit load transfer and to anchor the airship to the ground without support infrastructure. They've also developed a robotic fabric repair system called Spider that crawls across the surface of the airship, like a bunch of little spiders, finding and patching pinholes in the fabric and transmitting the repair job photos back to a laptop for review. That's the sort of system that would be required to ensure that the inflatable remains airworthy without risk to humans to repair leaks.

Hydrogen lifting gas would not be flammable in a 96.5% CO2 and 3.5% N2 atmosphere, but H2 leaks and causes other problems. Pure CO2 provided from a heat pipe and gas filtration system (to capture undesirable compounds like sulfuric acid) extending into the lower atmosphere to transfer heat from the CO2 in the lower atmosphere into the gas bags would also work. I actually think the heat pipe system is the best solution since it could be designed to be self-regulating and not require external power or electronic devices to function. A combination of one-way pressure relief valves and simple buoyancy would regulate the operating altitude of the airship. Come to think of it, as the CO2 in the gas bags cools, the pressure relief valves could also incorporate miniature gas turbines that provide electrical power to provide the slight overpressure in the habitable portion, life support equipment, avionics, communications. Alternatively, as the CO2 cools it could be compressed, stored, and then released on demand to CO2 powered turbines for motive and electrical power. There's lots of ways to use CO2 and an extreme temperature delta to produce power.

SpaceNut · 2018-10-25 17:53:43

The density of dry ice is about 1.5 g/mL.
Mass of CO2 = Density * Volume
Density = 1.5 g/ ml
1 ml = 1 cm^3
Volume of cube = side^3

If all we had was a cube that was 7.5 mm = 0.75 cm

Volume of cube = 0.75^3 cm^3 = 0.75^3 ml

Mass of cube = 1.5 g/ml * 0.75^3 ml

Moles of CO2 = mass ÷ mass of 1 mole = (1.5 * 0.75^3) ÷ 44
At Standard temperature and pressure, one mole of a gas has a volume of 22.4 liters.

Need to solve how super heating changes the volume as that is the upward thrust that it would get to bring a payload from the surface back to orbit.

RobertDyck · 2018-10-25 20:27:27

Are you trying to find a lift gas for a blimp on Venus? You would want the blimp to hover at altitude where atmospheric pressure is 1 Earth atmosphere. Temperature is also tolerable at that altitude. CO2 at STP is 1.9763 kg/m³ or 0.12338 lb/ft³. CH4 at STP is 0.7173 kg/m³ or 0.044779 lb/ft³. And as kbd512 said about hydrogen above, methane is not flammable in a 96.5% CO2 and 3.5% N2 atmosphere. Use methane as lift gas, it's a lot less prone to leakage. Especially if contained in aluminized polymer film. For Venus you would want a polymer that can withstand high temperature, UV, and sulphuric acid.

elderflower · 2018-10-26 03:07:31

Significant lift would be had by using CO in your gas bags. Not so good as methane, but you don't need to extract hydrogen to make it on site.

Void · 2018-10-26 09:18:29

Methane and CO seem like things worth exploring.
A reference to a body of thinking on atmospheric habitation for Venus is here:
https://en.wikipedia.org/wiki/Colonizat … fficulties

By no means to I think a sure solution to the problems exists, but it is a task worth a bit of thought work I think.

This is an article about NASA's exploratory thinking on the subject:
https://www.space.com/29140-venus-airsh … ology.html
At least their first air ships would be filled with Helium. It seems implied in other reading that Helium could be extracted from the atmosphere.
Quote:

HAVOC's solar-powered airships would fly at an altitude of about 30 miles, where they'd receive 40 percent more solar energy than Earth receives at its surface.

A problem is sulfuric acid droplets on solar panels:
Quote:

The airships' solar panels would also have to function in a hostile environment; concentrated droplets of sulfuric acid are common in Venus' atmosphere. The HAVOC team has done some experimental work to identify materials that could serve as protective coatings for the panels, Jones said.

My initial thinking was to get the solar power plants above the clouds, so as to avoid the corrosive environment, but it may be that a low level of corrosive character is guaranteed even there. So, now I am thinking backwards on it.

……

Supposing you had an envelope which had in it's interior a rectenna which also served in part as the internal structure. In this case of course I am thinking of solar power plants in the Orbitsphere of Venus, beaming power to a balloon target. The rectenna safely inside of the acid proof envelope.

In this case then the interior atmosphere can be an Oxygen/Nitrogen mix, and the assembly would float within the clouds. Geosynchronous is not absolutely required, but I would think that for Venus geosynchronous would be much lower than for Earth.

https://en.wikipedia.org/wiki/Space-based_solar_power
But it sounds like the rectenna's would have to be very large, so it would be a very large enclosure(s).
Supposedly humans would not be at that much risk, but I am thinking that I was exposed to concerned members here previously on the safety of such a system.

So you have so far these two options. Fly above the clouds, but still have to have special solar panels that can endure a corrosive environment. Or, embrace the sulfuric acid clouds and power the manufacturing facility with power from a space based solar power.

I think that the "Fly High" plan is already fairly well understood. So I am going to explore the space based solar power notion.

So, if you wanted to refine dry ice, Liquid Nitrogen, Helium, Argon, and perhaps Sulfuric Acid, and water from such a platform, a first step would be to suck in atmosphere from the cloud levels, and use a centrifuge to wring out the mist of Sulfuric Acid which at lower levels might also be diluted with water vapor mist.

A next stage would be to cool the gas mix, so that what sulfuric acid and water vapors in it were induced to condense. Another stage of centrifuging then perhaps.

I am guessing that perhaps the remaining gas mix would not be too corrosive to handle. So, then you would process the treated atmospheric gasses for the production of Dry Ice, Liquid Nitrogen, Helium, Argon, etc.

As for the Sulfuric Acid and water vapor liquids you produced, I suppose if they fill an industrial or life support need you would extract what you wanted from them.

Otherwise you could use those fluids for evaporative cooling. It would have to be a very corrosion tolerant cooling tower, but you could expel, the heat generated by the air separation processes.
https://en.wikipedia.org/wiki/Air_separation

These plants could perhaps be at lower levels in the clouds, maybe up to human tolerance of Nitrogen in their breathing process.
https://en.wikipedia.org/wiki/Nitrogen_narcosis
So at three bars of pressure or less.

Could the rectenna beams penetrate that deep? I am not sure.
However floating in say 2.5 bars of Venus atmosphere would allow the factory to have a very favorable lifting capability per floatation. This would allow more heavy industrial equipment on board.

So then, there appear to be at least two methods to achieve the products desired. 1) Reject the clouds, fly above them, but have trouble lifting your heavy factory up that high. This version is direct solar. You probably need special lifting gasses. Or; 2) Embrace the clouds, go deep, have very little trouble with keeping your factory afloat, use evaporative cooling, but have a need for either orbital based solar power or nuclear fission. (I don't favor nuclear fission for this).

I think this stuff in it's whole implementation will be a long time coming.

Done

Last edited by Void (2018-10-26 10:05:33)

kbd512 · 2018-10-26 14:16:19

My suggestion about using hot CO2 from the lower atmosphere was an attempt to avoid chemical refinement processes, but CO is obviously lighter than CO2. However, you still have to make CO. Obtaining N2, which has a nearly identical bulk density to CO, only requires compression and separation from CO2. That is not a major technological hurdle to clear since we already do that on Earth for industrial purposes. Robert's suggestion about using Methane requires extraction using sulfuric acid and CO2 to make CH4 is also a good idea, but also requires CH4 production. The chemical process I'm familiar with would yield O2, H2, and H2O, which could then be fed into a Sabatier reactor with CO2 to yield CH4. Since ISS, and presumably any Mars missions, would also benefit from such technology, further development and refinement has synergistic effects for Mars missions. On Venus, there is no abrasive dust problem to overcome and the source CO2 is sucked in and compressed at atmospheric pressure.

This problem boils down to gas bag mass, materials science, and total system complexity required to assure that the station stays aloft. The buoyancy / lifting force generated by the gas selected determines the volume and therefore mass of the gas bags that keep the station aloft. That said, any gas bag system requires constant input. There's no such thing as a leak-free system light enough to stay aloft, so design it to leak in a controlled manner and use readily available gases to keep the station aloft.

I would prefer to use some a system that combines passive pressure release valves with a gas compression / separation system that provides a locally sourced lifting gas product requiring minimal energy / technology input prior to use. The gas choices dictated by the planet's atmosphere are CO2 or N2. N2's bulk density at STP is virtually identical to CO, but N2 has the advantage of being an inert gas that doesn't require development and testing of special aeronautical materials, beyond those required to survive exposure to the sulfuric acid and hydrogen sulfide clouds of Venus. Sourcing enough H2 or CH4 to use as a lifting gas for a colony to use would require substantial technology investment / input, which is the same problem we're having with a Mars colony, as well as requiring periodic replacement of the gas bags.

However, the fluoropolymers already in current use as aeronautical materials for airships are already resistant to sulphuric acid. Therefore, the skin material of the gas bag should be PTFE bonded to UHMWPE / Spectra, also a current in-use aeronautical material for military and NASA parachutes, as numerous others have already suggested. This use case does not require substantial changes or testing.

The Sabatier reactor and the collection of H2SO4 or H2S is still useful for many other purposes, namely generation of O2 for the life support system, H2O for human and aeroponic or hydroponic greenhouse consumption, and CH4 to power a fuel cell to provide backup electrical power, and production of polymers to support local repair and construction of the inflatable structures.

Primary electrical power should be provided by one or more of the following:

1. solar panels - works during daylight, but not at night, thus a solar-only approach would also require heavy batteries

2. wind turbines - works well, given wind speeds of up to 90m/s, basically the same technology that provides motive power, but heavy and requires importation of heavy metal conductors until some sort of commercial Graphene conductor becomes available

3. heat exchangers - capable of driving a turbine 24/7 using hot flowing CO2, but requires deployment of a several-kilometers-long fluoropolymer "snorkel tubes" deployed into the lower atmosphere to obtain hot, high-pressure CO2 to drive a turbine, but turbines are complex devices subject to mechanical (bearing) failure, although a fluid bearing using liquid CO2 could, theoretically, operate indefinitely

4. peltier device - another heat exchange concept that uses the aforementioned tube to create a temperature delta along both sides of the device to create power, with the added benefit of not using any moving parts except for the working fluid (the Japanese have an interesting take on the concept that uses tubular devices with hot or cold water pumped through them to generate the delta-T)

Anyway, the technology to do all of this is a lot more feasible in the near term than the technology required to live on Mars, mostly because there's nothing fundamentally new required. Similar inflatable habitats could be used as those destined for Mars, with the benefit of a less extreme pressure and temperature deltas and far less GCR radiation to contend with. The inflatable habitation technology for Venetian cloud colonies could become the basic prototype for use on Mars. The Mars variants would just be beefed up to withstand the temperature swings (more outer layers of PTFE), higher pressure containment requirement (more Spectra restraint layers), and reinforcement to support the weight of regolith bags for GCR protection (a final outer layer of Kevlar for abrasion resistance, combined with composite reinforcement ribs). That said, the same basic habitation tech that would work on Venus would also work on Mars.

Everyone needs to forget about trying to ship pre-assembled habitats to the moon or Mars aboard BFS. It's clearly not amenable to doing that. However, the cargo lift or hoist system presents no real problems to surface delivery of volumetrically small and comparatively lightweight objects (an empty inflatable habitat, a battery pack, or a roll of thin film solar panels) to the surface. The military uses ropes to send heavy objects down cliffs on a routine basis and the Navy is particularly fond of doing it. It works quite well.

We still haven't discussed the rigging system for this airship, either. Given the high wind speeds, dynamic pressures, and potential for unpredictable drafts, the gas bag should probably be a large multi-cell donut with a series of redundant stays tied to the inflatable gondola structures below it. The mass distribution within the gondola would function as a form of lead weight like that found in the keel of sailing ship. The rigging would be connected to a series of avionics-controlled electric servos used to adjust the donut's angle of attack, relative to the oncoming flow, so as to provide variable lift.

kbd512 · 2018-10-26 16:58:14

Void,

The thin film solar panels are bonded to PTFE laminates. The US DoD's variant of the product produced by Ascent Solar features this laminate for ruggedization (specifically, resistance to acidic chemicals used for cleaning and hydrocarbon fuels), for example. The high temperatures are more problematic, but not at the altitude where this airship would conceptually operate. It won't operate at "Earth sea level", but more like "Earth Mile High City" where the temperature drops to a value common in a temperate desert. Thus, no advanced cooling systems are required. Inside, it'll be like an office building. Outside, it'll be like Texas in the summer. In other words, not pleasant but not insanely hot.

You probably don't want to fly above the clouds because you need the sulphuric acid to obtain water. The types of equipment required to obtain the requisite consumables from the atmosphere don't really require lots of heavy equipment, so I think it's preferable to fly higher where it's cooler, so that less insulation, cooling capacity, and electrical power is required for propulsion. Beamed power isn't required. Even with losses, there's more than enough thermal energy available from the lower atmosphere to provide enough power.

SpaceNut · 2018-10-26 17:15:16

With the current technology the entire mission could be built and simulated in earth safer environment in order to test it all out. This could also include a simulated landing and return to orbit via the changing of gasses to a frozen form to allow the blimp to land and then allow for the temperature to cause the iced materials to become liquid once more without adding any energy to float once more...

The use of moxie would give all the oxygen for crew and plenty of co for the blimp to make use of.....

Void · 2018-10-26 19:27:58

Sounds good Spacenut. Of course I will eventually want to see a thriving economy for Venus. That could involve some interplanetary commerce, but then it would be great to be able to make a lot of this stuff insitu at Venus from local resources or maybe some Near Venus Asteroids.

kbd512 · 2018-10-27 12:51:02

I thought this would be relatively clean and simple, but the more I read about the material properties of available synthetic fibers like Spectra (UHMWPE) and Vectran (LCP) and Technora (p-aramid), the more obvious it became that proper materials selection and testing protocol won't be simple or cheap. We also need more data about expected H2SO4 concentrations and temperatures since hot sulfuric acid rapidly degrades synthetic fabrics. It may turn out that fabrics capable of exposure to higher temperatures, such as Vectran and Technora (a relative of Teijin's Twaron), supplant the substantially lighter Spectra as the go-to materials.

Venus Temperature and Pressure by Altitude
H(km) T(C) P(bar)
45 111.85 1.979
50 76.85 1.066
55 28.85 0.5314
60 -10.15 0.2357
65 -30.15 0.0977

As we can see from the graph, the "goldilocks" zone for airship operations is roughly 10km in height. Below 50km temperature and pressure rapidly increase to values that would cause structural failures. Above 60km the pressure and temperature are low enough that pressure suits are required for repair activities. The wind speeds on Venus at altitude have been clocked at 100m/s, similar to the fastest jet stream wind speeds here on Earth, so a loss of altitude of a kilometer could take mere seconds. Thus, the ability to hold altitude is an absolutely critical design feature.

The manufacturer states that Spectra fabric is not intended for extended duration use above 80C to 100C, which imposes a 50km lower operating limit. However, temperature can and does fluctuate on Venus and I need to find out how much. The temperatures at 45km in altitude would cause Spectra to loose substantial strength and by 40km in altitude, Spectra will melt. Vectran retains 50% of its strength at 150C, for comparison purposes.

Synthetic Fiber Data

Ultra High Molecular Weight Polyethylene Fiber from DSM Dyneema (DSM Dyneema and Honeywell Spectra are both UHMWPE fiber)

Kuraray Vectran (Liquid Crystal Polymer)

Samson Technora (high temperature capable para-aramid for load-bearing ropes and cordage)

Synthetic Fiber Info and Comparison from the US Naval Academy:
2 PAX Short Course Fibers

NASA Orbital Environment Materials Testing:
Comparison of High-Performance Fiber Materials Properties in Simulated and Actual Space Environments

Void · 2018-10-27 13:05:00

Perhaps Fiberglass? Might be heavy though.
https://beetleplastics.com/storing-sulf … struction/

I like your doughnut notion. Multichambered Toroid I am guessing. Could there be another doughnut above it, connected, filled with Helium & Nitorgen or a Hydrogen & Nitrogen mix?

I am thinking that the Nitrogen may plug some pores and reduce Hydrogen or Helium loss.

I am grasping on straws though.

......

This is why I favor a long term orbital presence, something like an Antarctic base, so that a lot of experimentation could be done prior to trying to occupy the atmosphere. Extraction of atmospheric gasses from the atmosphere by a skyhook might be it's payday activity.

The other purpose for such an orbital base would be in case a ship on it's way to Mars needed to abort to Venus.

Done.

Last edited by Void (2018-10-27 13:06:13)

kbd512 · 2018-10-27 16:11:09

Void,

Yes, I was thinking of a multi-chamber toroid deployed into the atmosphere behind a large HIAD. The most significant challenge is achieving sufficient deceleration high enough above Spectra's 50km lower altitude limit to permit sufficient time for gas bag deployment, else the Spectra will begin to melt at lower altitudes. I suppose a system of multiple gas bags in different containment structures is feasible, but that would substantially complicate the rigging mechanisms and increase mass. Are you thinking of a deployment inflatable?

NASA's Venus Temperature / Pressure / Atmospheric Density Data by Altitude

NASA/TM—2002-211467 - Atmospheric Flight on Venus

Understanding Composite Materials - An Engineer's Perspective

Carbon Fiber vs Kevlar vs Fiberglass - Which one is right for YOU?

Why you SHOULDN'T wrap Fiberglass in Carbon Fiber!

Points to Remember

The fiber composite structures are substantially heavier compared to all the fabrics I provided data sheets for. However, mass is also relative to the required strength and stiffness in any practical aeronautical application.

1. S-Glass and E-Glass GFRP composites are tops in pure strength on a per-unit mass basis if both tensile and compressive loads are considered, but not stiffness, which is where CFRP's really shine.
2. Kevlar and Spectra are even stronger than S-Glass in tension, but far weaker than any other types of fibers or composites using those fibers in compression and only slightly stronger than steel. That tends to limit the applications where those materials are optimal since many aeronautical structures see a combination of tensile and compressive loads applied in actual use.
3. Since Kevlar and Spectra have extreme tensile strength and superb abrasion resistance since their fibers are so slick, optimal uses include pressurized gas tanks, body armor, ropes, and chafing guards. Basically, applications where tensile strength is the most important consideration.
4. Most people think Carbon Fiber and CFRP's are the strongest, but that's because they compare the E-Glass composites made using the Burt Rutan / Scaled Composites mold-less construction techniques. On a per-unit mass basis CFRP's are considerably stiffer than E-Glass and somewhat stiffer than S-glass GFRP's, but weaker than both S-Glass and E-Glass on a per-unit mass basis if pure strength is the only consideration. That's frequently not the case in practical aeronautical applications where stiffness counts for a lot and components are designed to distribute loads appropriately.
5. Due to the stiffness of CFRP's, on a per-unit mass basis, CFRP's can be made approximately 10% to 15% lighter than S-Glass and 15% to 30% lighter than E-Glass, but mass savings of CFRP's over GFRP's depends on what direction(s) the load(s) are coming from and component design.
6. The carbon fibers in CFRP's have almost no elongation prior to failure. When CFRP's break it's a brittle failure mode, meaning it tends to snap like a glass rod. Conversely, the fibers in GFRP's tend to buckle first, especially under compressive load, and have substantially more elongation prior to failure. Composite landing gear on light aircraft are typically made with S-Glass since both tensile and compressive loads are applied and substantial deflections are routine. The stiffness and lack of elongation is why CFRP's are so popular for use in wings, fuselages, and propellers. Unlike landing gear, a rigid structure that doesn't deform under load is required for optimal performance of those components. The designer has to pay careful attention that loads applied don't exceed the elongation potential of the assembled CFRP components or the result is catastrophic failure.
7. UHMWPE (Dyneema / Spectra) fibers are typically not used in fiber reinforced composites because the fibers are so slick that the fibers tend to "pull" through the resin when a load is applied and the component deflects under load. In other words, the epoxy resin or glue can't hold or bind the fibers in place, so the fibers themselves begin to buckle before the resin holding the fibers in place does.
8. All that said, virtually any composite we care to name off, including the lightweight CFRP's, will be substantially heavier than the fabrics if the ability to repeatedly deflect under load and return to original size / shape is a consideration, and it is in an airship. Therefore, we would limit our use of hard composites and metals to applications where the specific mechanical properties of those composites or metals are required. Off the top of my head, this means the control mechanisms and attachment points for the rigging gear.

Interestingly, from my amateur attempts at researching how N2 and CO degrade or age Vectran, CO may actually be the better gas to use so long as extremely pure CO can be had. Mixing CO with other gases is a really bad idea. Apparently, N2 and air (O2/N2), has the effect of prematurely aging Vectran fibers by breaking the CO bonds within the molecular chains of the fibers.

Between the LFL and UFL, CO is highly flammable, so O2 and static electricity must never be present near the pressure release valves that control buoyancy or there could be fire (explosions are unlikely in the Venetian atmosphere). That said, PTFE and UHMWPE fabrics will also self-extinguish, even in our atmosphere. Any atomic oxygen present is also very bad news for Spectra / UHMWPE. As the previously posted materials testing document from NASA shows, Spectra failed completely in mere months from atomic Oxygen in the orbital environment. Similarly, H2SO4 is bad news for virtually all of these materials, even though many have substantial resistance to sulfuric acid, especially Vectran and PTFE. Thus, a PTFE layer or coating of fluoropolymer is required for ultimate durability in the Venetian atmosphere.

There's lots of design considerations at play here, but it's also a specific set of solvable problems. Lately, this has become far more interesting to me than Mars since there's a slew of human physiology and basic materials science problems with going to Mars and living there on a permanent or semi-permanent basis. We already have the soft of stuff required to live in the clouds of Venus.

SpaceNut · 2018-10-27 16:55:26

I wonder just how well the folding heat shield materials would work for the shell of the blimp balloon fabric.

Void · 2018-10-27 18:28:05

That is an interesting question Spacenut. I am not equipped for it at this time.

In fact I feel very insecure about managing to adapt to the sulfuric acid clouds as well.
However I will give a couple of things a shot.

I will use this table, and fumble around like a fool on this, but I tried.
http://gravity.wikia.com/wiki/Atmosphere_of_Venus

I would like to suggest that the clouds will offer 4 types of assault on your atmospheric barrier. Atmospheric barrier being the outer most dividing wall between Venus atmosphere, and the interior gasses, which is some cases are presumed to be a Nitrogen/Oxygen mix breathable by humans. Alternately there could be interior gasses that are otherwise. Just pure Nitrogen, Helium, Helium/Oxygen, or even Hydrogen.

1) First of all the clouds themselves if you can see them are to a large extent suspended mist of Sulfuric Acid, perhaps with a bit of water.
So this is the first assault.
2) The temperature of the dividing wall will determine if the wall will receive condensation to it from Sulfuric Acid vapors.
So, this is the second assault.
3) Then the vapors of Sulfuric Acid themselves.
So, the third assault.
4) U.V. light. If you are going to be high enough in the clouds to use solar energy, then you will have to cope with U.V. light.
So, the fourth assault.

So, I am thinking of a structure as previously considered, but wrapped in an acid proof sock of perhaps fiberglass cloth without resin. A wick.

I am thinking of a inverted cone. Perhaps with a rounded top. The top portion having solar panels which unfortunately have to be fortified against the worst corrosive effects that the clouds offer.

The top portion also being protected by fiberglass wick, but here it requires stand-offs that can endure contact with the wick.

For the down pointing cone part, the wick simply is an envelop attached to the perimeter of the top of the cone, and the envelope of the wick surrounding the cone.

With this, the hope would be to take care of problems #1 and #4 to some extent. The mist impinging on the wick, then it being a wick, that flowing downwards to drip off of the bottom, preventing the mist from impinging on the actual wall. Winds however might push it against the walls, so a weight is needed at the bottom of the wick to retain tension on the wick. Perhaps the weight would be a sulfuric acid containment where the sulfuric acid could in part be processed. Some of the sulfuric acid might simply be dumped overboard.

If possible the dividing wall will be warm enough to discourage condensation. Don't know if that is possible. You might have to be up high where the temperature of the atmosphere is colder. Again not sure if it can be done. But if so, that would handle #2.

As for #3, I don't know what the rate of corrosion would be from sulfuric acid vapors alone. If it is a problem, then perhaps purge air could be injected into the wick chamber. How that would be engineered I am not sure.

And that is all I have for it for now.

……

As for weight, I am sure weight would be a problem. However the larger the enclosure, the more volume of lifting gas you have against the weight of the total envelope of the device.

……

This is why although I am comfortable with a machine to dive to the surface of Venus and collect minerals, and I am comfortable with orbital habitats for Venus, I think there would need to be a long period of research to discover if it can ever be possible to install and maintain floating habitats for humans.

……

My own feeling is that first you start with a research station in orbit, and begin testing the environment of Venus to discover what is real and what is simply not attainable.

In my view, if you could scoop gasses from the top of the atmosphere of Venus into orbit as I have mentioned before perhaps with a skyhook, and if you had materials for orbital structures from the Moon and/or asteroids, then you might discover a value for Venus before you even inhabited the clouds. Of course this then requires solving radiation problems.

That's how I see it.

The Moon first, because from what I see the Moon will be first, and there will be a continuing interest in the Moon.
Then Mars.
Then much later an expanded presence for Venus. But Venus could have a research station before that that would double as a rescue crew, if a ship like a BFS on it's way to Mars via Venus had to abort to Venus.

I don't see how to rush Venus. It's going to be a real nightmare to make work.

Done.

Last edited by Void (2018-10-27 19:04:48)

kbd512 · 2018-10-27 18:58:09

SpaceNut,

A backshell is definitely required during reentry, if that's what you're getting at. The HIAD is inflated in orbit around Venus, just prior to reentry. This is what I was thinking, regarding the Venus Atmospheric Station setup and crew transfer to the station.

F9H - SpaceX Falcon 9 Heavy; SpaceX's partially reusable heavy lift booster
LLO - Low Lunar Orbit
LVO - Low Venus Orbit
TLI - Trans-Lunar Injection
TVI - Trans-Venus Injection
ITV - Interplanetary Transport Vehicle; NASA / Lockheed-Martin's SEP-powered ITV variant in LLO
SEP - Solar Electric Propulsion unit / stage; Lockheed-Martin's ExoLiner space tug using Aerojet-Rocketdyne / NASA X3 ion engines or Orbital ATK's take on the same concept, which uses their GEOStar bus
VAS - Venetian Atmospheric Station
HIAD - NASA / JPL's Hypersonic Inflatable Aerodynamic Decelerator; an advanced lightweight deployable reentry technology for Venus and Mars

1. F9H #1 injects the SEP into a GTO orbit
2. F9H #2 injects the VAS into the same orbit
3. SEP mates with VAS in preparation for TVI
4. SEP TVI's the VAS payload to Venus
5. SEP places VAS into a stable LVO in preparation for reentry
6. HIAD inflates and VAS separates from SEP for reentry
7. VAS reenters, using HIAD to rapidly decelerate high in the Venetian atmosphere, whereupon HIAD falls away
8. The gas bags for VAS are rapidly inflated to keep the station at or above 50km in altitude
9. The inflatable habitation modules are slowly inflated until a slight overpressure at the expected cruising altitude is achieved
10. A series of automated station checks are performed to confirm integrity of the gas bags, rigging system, and habitation modules
11. The atmospheric snorkel tube is deployed into the lower atmosphere to use pressure to force hot CO2 through the heat exchanger for electrical power, to obtain additional lifting gas, O2 for pressurization, and to obtain H2SO4 for water
11. atmospheric flight tests begin to assure positive control of the station
12. F9H #3 TLI's a VAS crew to the ITV
13. VAS crew docks with and transfers to the ITV
14. ITV departs LLO for Venus
15. ITV spirals into LVO for reentry, in preparation for crew transfer from the capsule to VAS
16. VAS crew reenters, inflates their own balloon / gas bag after reentry, and chases down VAS
17. VAS uses a flexible remote manipulator arm (a super-sized variant of Festo's Octopus Gripper technology) to capture the Dragon capsule and the crew transfers to VAS from their capsule

kbd512 · 2018-10-27 19:06:59

Void,

PTFE has superb resistance to 100% concentrations of sulfuric acid, both hot and cold. It's also superb against most other acids with Carbon and Nitrogen in them. A PTFE shell or coating on exposed surfaces is absolutely mandatory in the Venetian atmospheric environment.

Have a look:

PTFE and Teflon Chemical Compatibility Chart

Edit:

In case it's not clear, the major problem I see is H2SO4 getting inside the structure from impurities in the inflation gases or through the various valves that regulate the pressurization of the structure. That would be a disaster. That's why the Spectra needs a PTFE coating or the lifting gas collection system requires ultra-pure CO or N2.

Edit #2:

Also, have a look at the material properties for Carbon Monoxide / CO:

Air Products - Carbon Monoxide

Last edited by kbd512 (2018-10-27 19:28:52)

SpaceNut · 2018-10-27 20:49:33

Was not really thinking of the hiad which is the doughnut cone inflatable but more along just the frabic used in the adept foldable .

https://ntrs.nasa.gov/archive/nasa/casi … 012768.pdf

trial version for mars

https://flightopportunities.nasa.gov/technologies/139/

What I was thinking of was to use a bigelow inflatable which would be inside the doughnut bouyancy inflateables with a cover skin with the material of adept...

Astronauts could ride in the inner portion of the inflatable that is not collapsed as they would not require much space to be within leaving the capsule on orbit.

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