Balloon to survive at ground level in Atmosphere of Venus

tahanson43206 · 2022-11-24 10:36:46

For SpaceNut re #50

Thank you for this helpful addition to the topic.

It appears from my Google search (pasted below) that the Bourdan Gauge is used for ** relative ** pressure measuremsnt.

In the case of the proposed instrument balloon package for the surface of Venus, the gauge would be used to insure that at all times, pressure inside the balloon matches the pressure of the atmosphere outside.. The pressure would be equalized by admission of oxygen to the inside of the balloon, through a valve controlled by the gauge.

Upon arrival at the surface of Venus, the internal pressure could be increased or decreased by releasing or admitting oxygen.

The method of addition of oxygen I am proposing is to admit CO2 to a processing subsystem, to separate Oxygen from Carbon Monoxide.

The Carbon Monoxide can then be used as a means of propulsion, by releasing the gas from ports to achieve lateral navigation.

Here is a search result for the type of gauge you have shown:

People also ask
Where is a Bourdon gauge used?
Does Bourdon gauge measures absolute pressure?
Image result for bourdon gauge
Bourdon tubes measures gauge pressure, relative to ambient atmospheric pressure, as opposed to absolute pressure; vacuum is sensed as a reverse motion. Some aneroid barometers use Bourdon tubes closed at both ends (but most use diaphragms or capsules, see below).
Pressure measurement - Wikipediahttps://en.wikipedia.org › wiki › Pressure_measurement
Search for: Does Bourdon gauge measures absolute pressure?
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Bourdon Gauge - an overview | ScienceDirect Topicshttps://www.sciencedirect.com › topics › engineering › bo...
bourdon gauge from www.sciencedirect.com
The Bourdon gauge consists of a tube bent into a coil or an arc. As the pressure in the tube increases, the coil unwinds. A pointer connected to the end of ...
Pressure gauges | Bourdon Instrumentshttps://www.bourdon-instruments.com › pressure-gauges
bourdon gauge from www.bourdon-instruments.com
Bourdon offers mechanical pressure gauges for accurate measuring of relative, absolute and differential pressure covering measuring ranges from 0…6 mbar to 0…
Bourdon tube pressure gauge - WIKAhttps://www.wika.com › Products › Pressure
bourdon gauge from www.wika.com
Bourdon tube pressure gauges are used for the measurement of gauge pressures from 0.6 ... 7,000 bar. They are classified as mechanical pressure measuring ...
Bourdon USA: Pressure Gauge Distributor & Process ...https://bourdonusa.com
bourdon gauge from bourdonusa.com
Bourdon is your first choice for precise mechanical pressure-measuring instruments and we offer a wide range of metals as well as customization.
Bourdon Pressure Gauge Explained - saVReehttps://savree.com › encyclopedia › bourdon-pressure-g...
bourdon gauge from savree.com
A Bourdon gauge is a mechanical device used to measure and display pressure. The gauge can be used for measuring pressure in both gas and liquid state ...

(th)

SpaceNut · 2022-11-24 10:59:17

The issue for a balloon valve is its only 1 way so there is no adding to the internal pressure since the known starting point is 1 earth or less when we are making it.

While it will stay that way until we are entering Venus Atmosphere where upon entry release the pressure outside is going to drop to near zero and we will need to equalize to that level at freezing temperatures.

The issue is over release is as bad as under releasing as once we do release there is no turning back as a too thin shell is going to crack unless it made thicker to take these swings of temperature and pressure.

http://www.surmet.com/pdfs/news-and-med … eramic.pdf

Average strength values of 700 MPa at 21°C and 631 MPa at 500°C have been measured for ALON specimens
prepared by precision surface finishing techniques.

93 bar of co2 is 1349 psi at the surface of Venus is the external mass accumulated pressure on the sphere.

https://www.engineeringtoolbox.com/carb … _2018.html

https://en.wikipedia.org/wiki/Venus

Surface temp. min mean max
Kelvin 737 K[5]
Celsius 464 °C
Fahrenheit 867 °F

https://resources.finalsite.net/images/ … ioxide.pdf

tahanson43206 · 2022-11-24 11:21:26

For SpaceNut re #52

It is helpful to see data for the operating conditions of the proposed balloon probe for the surface of Venus.

One adjustment might help ... the valve needs to be able to open entirely during launch and flight, to allow air inside to escape to vacuum.

The valve needs to be able to close for admission of oxygen into the cavity as pressure builds during descent.

However, after arrival at the job site, there needs to be a way to allow gas to move either way.

It seems to me that if the valve opens at the job site it would allow oxygen inside the cavity to escape if that is needed, or to allow more oxygen to enter from the oxygen supply subsystem if that is needed.

To the best of my knowledge, valves for gas lines are two-way by default.

If fact, I can't think of any way to make a valve one way.

Here is a trade offer:

General Purpose, Stainless Steel Pressure Transducers
0 to 100 psi, Gauge, 4 to 20 mA, Cable

This measuring device produces a voltage based upon the pressure reading.

While the device itself appears robust, the temperature range is far below what is needed.

What is needed is a pressure sensor able to operate at 462 degrees Centrigrade.

The device itself will only measure a few psi difference, because (as we have shown) the pressure inside the balloon will match the pressure outside.

The temperature inside the balloon will match the temperature outside.

The 1349 psi you've shown will be acting on the components of the instrument package, so they must be designed to withstand pressure (and temperature) at the job site.

(th)

SpaceNut · 2022-11-24 11:43:26

For sure with a temperature and pressure sensing on the outside we need to have acid resistant types but inside we can get away with other types, but all of these will be wired to the controller for the electronic valve. The valve as well must be of an acid resistant material as well.

I was thinking that Piezoelectric pressure sensors Piezoelectric-Pressure-Sensor-Function-EN-Image.jpg?MOD=AJPERES&CACHEID=ROOTWORKSPACE.Z18_NA5A1I41L0ICD0ABNDMDDG0000-cb089d1c-116e-4d81-a703-bbf413db57c3-mCrZzSl

Acid resisance would be the next issue at temperature.

tahanson43206 · 2022-11-27 11:55:01

For SpaceNut re #54

Thanks for investigating the sensor technology that might survive in the atmosphere of Venus.

I understand there is sulfuric acid in the clouds above the surface, but am wondering of the air near the surface contains much (or any) sulfuric acid.

The Soviets landed at least one probe on Venus (I've forgotten the exact number). Hopefully they were able to take measurements of the components of the gas mixture at the surface, before their equipment gave up due to heat and pressure.

***
I've printed the posts by kbd512, and will be working my way through them in coming hours.

in the mean time, here is a calculation of the surface of the proposed 1 cubic meter probe:

https://www.calculatorsoup.com/calculat … sphere.php
Choose a Calculation
r, C, A | Given V
volume V =
1
Let pi π = 3.1415926535898
Units m
Significant Figures 9
Answer:
radius r = 0.620350491 m
volume V = 1 m3
surface area A = 4.83597586 m2
circumference C = 3.89777709 m
Paste this link in email, text or social media.
https://www.calculatorsoup.com/calculat … tion=solve

Five square meters is the nearest higher whole number to use for estimating the mass of an ALON shell for the balloon.

I'm confident that a 1 mm thickness is more than sufficient.

For some reason, I have to keep repeating that there is NO pressure difference between the inside and the outside of the balloon.

There is NO temperature difference between the inside and the outside of the balloon.

The extreme pressure at the surface of Venus will indeed be present, but it will squeeze the atoms of the ALON shell equally from both sides.

The ONLY difference between the inside and the outside of the shell is:

1) Oxygen is inside the shell
2) Carbon Dioxide is outside the shell

At the surface of Venus, unless I have set up the online calculator incorrectly (which is certainly possible) the lift available is 17 kilograms.

I found this online calculator for pure Aluminum:

https://www.omnicalculator.com/construc … num-weight

https://www.omnicalculator.com/construc … kness:1!mm

13.5 kilograms is the mass computed by this online calculator for a sheet of Aluminum 1 meter wide, 5 meters long, and 1 mm thick.

Since the stress on the envelope of the balloon is 17 kilograms of lift, and since that stress is distributed over the entire envelope, I am guessing that the thickness of 1 mm may be more than is needed.

The calculator gives 6.75 kilograms for the weight if the thickness is reduced to .5 mm.

However, this set of results is for pure Aluminum.

The same computation for ALON will be different, because ALON is an alloy.

This citation from Wikipedia provides a bit of information about ALON(tm):

Aluminium oxynitride
From Wikipedia, the free encyclopedia
Jump to navigation
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"ALON" redirects here. For the aircraft corporation, see Alon (disambiguation).
Aluminium oxynitride AlON.png
Spinel structure of ALON
Names
Systematic IUPAC name
Aluminium oxynitride
Identifiers
CAS Number

12633-97-5 check
Abbreviations ALON
Properties
Chemical formula
(AlN)x·(Al2O3)1−x,
0.30 ≤ x ≤ 0.37
Appearance White or transparent solid
Density 3.691–3.696 g/cm3[1]
Melting point ~2150 °C[1]
Solubility in water
insoluble
Refractive index (nD)
1.79[2]
Structure
Crystal structure
cubic spinel
Lattice constant

a = 794.6 pm[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
check verify (what is check☒ ?)
Infobox references
Aluminium oxynitride (marketed under the name ALON by Surmet Corporation[3]) is a transparent ceramic composed of aluminium, oxygen and nitrogen. ALON is optically transparent (≥ 80%) in the near-ultraviolet, visible, and midwave-infrared regions of the electromagnetic spectrum. It is four times as hard as fused silica glass, 85% as hard as sapphire, and nearly 115% as hard as magnesium aluminate spinel. Since it has a cubic spinel structure, it can be fabricated to transparent windows, plates, domes, rods, tubes, and other forms using conventional ceramic powder processing techniques.[citation needed]
ALON is the hardest polycrystalline transparent ceramic available commercially.[2] Because of its relatively low weight, distinctive optical and mechanical properties, and resistance to oxidation or radiation, it shows promise for applications such as bulletproof, blast-resistant, and optoelectronic windows.[4] ALON-based armor has been shown to stop multiple armor-piercing projectiles of up to .50 BMG.[5]
ALON is commercially available in sizes as large as 18-by-35-inch (460 mm × 890 mm; 46 cm × 89 cm) monolithic windows.[6]

What is NOT at ALL clear is whether this material can be fabricated into a thin spherical shape, and that it would have any flexibility at all in that shape.

Quoting from kbd512 Post #203555:

ALON has a bulk density of 3.7 g/cm^3

A UK web site provided this figure for the density of Aluminum:

People also ask
What is density of aluminium?
2.7 g/cm³
Aluminium / Density

I understand (from the Aluminum calculator web site) that they are using a density figure of 2700 in their software.

That appears to match the 2.7 g/cm^3 figure from the UK web site.

From this I deduce that the figure computed earlier (above in this post) would need to be increased by a factor of:

1.37037037

to show the mass/weight of ALON in the application.

6.75 kilograms was given as the mass/weight of Aluminum for the balloon shell.

That number times the factor for ALON gives: 9.25

I deduce that if the shell is half a millimeter thick, then the payload is 7+ kilograms.

(th)

tahanson43206 · 2022-11-27 12:07:10

I ** think ** (but am not certain) that the ratio of surface area to volume DECREASES as the volume of a sphere increases.

I would greatly appreciate someone in the current membership double checking my understanding of this mathematical relationship.

I ** think ** it means that as the volume of a probe increases, the mass needed for the ALON shell becomes less and not more, with respect to the volume.

About 42,100,000 results (0.69 seconds)
Image result for how does surface area of a sphere change with increase of volume
Graphs of surface area, A against volume, V of the Platonic solids and a sphere, showing that the surface area decreases for rounder shapes, and the surface-area-to-volume ratio decreases with increasing volume.
Surface-area-to-volume ratio - Wikipedia https://en.wikipedia.org › wiki › Surface-area-to-volume_...

What would be helpful (for me for sure) is if someone could prepare a simple table showing:

Top row: Volume in 1 cubic meter increments: eg, 1 2 3 4 5

Along the side: ALON shell mass needed to enclose the volume, given a thickness of .5 mm

Row one would presumably show 9.25 kg for the mass of ALON

In the cells of the grid I'm hoping someone can show the lift available.

Remember, the lift is 12 grams per mol independent of pressure and temperature.

All you need to do is to compute the number of mols in your sphere, multiply by 12, and you have the grams of lift for that sphere.

***
The resident expert in spreadsheet technology is GW Johnson. I'll write to Dr. Johnson to ask if he is willing to (at least consider) setting up a spreadsheet for the Venus probe problem.

(th)

kbd512 · 2022-11-27 12:36:30

tahanson43206,

Correct. Surface area increases as the square of a sphere's radius, whereas volume increases as the cube of its radius. It's literally written into the mathematical formulas for area (powers of 2) and volume (powers of 3). That's why large nuclear reactors have trouble getting rid of waste heat and can melt down, whereas smaller reactors don't.

tahanson43206 · 2022-11-27 13:00:15

For kbd512 re #57

Thanks for the confirmation that the lift will increase as volume of the probe increases, if the ALON shell is held to the same thickness.

I've written to GW Johnson in hopes he might be willing to (at least consider) making a spreadsheet to show the lift for various sizes of probe.

The upper limit would appear (to me at least) to depend upon the launch vehicle and related subsystems for delivery to the surface of Venus.

The 1 cubic meter balloon would appear to be practical (if ALON can be made into a shell that thin) but a larger probe would permit more instruments and power capabilities.

(th)

kbd512 · 2022-11-27 15:24:44

tahanson43206,

The issue you're ignoring is the simple fact that material tensile strength is a constant value at a given temperature. What you proposed is something far thinner than scaled-up glass Christmas tree ornament. Most of us who have dropped an ornament onto a hard floor are aware of how fragile those are with zero pressure differential and at room temperature, and even though ALON is much tougher than quartz or Pyrex "glass", it's still an amorphous crystalline structure that doesn't respond well to radical temperature and pressure deltas.

In a confined space, a given starting mass of O2 gas heated to 462C won't produce the same pressure as CO2, so pressure regulation will become a very delicate balancing act whereby you're forced to pressure-match the outside atmosphere quickly and precisely to avoid rupturing the glass bubble. You need some sort of pressure regulation device to maintain buoyancy, and this is why semi-open hot air balloons have a kind of "valve" on top of the canopy to release hot air to control altitude. This requires a separate highly pressurized (and therefore heavy) metallic O2 sphere that injects O2 into the larger glass bubble as it descends through the atmosphere, towards the surface. Even if you start in the atmosphere of Venus where temperature and pressure approximate Earth sea level, you're going from 1 Bar to 92 Bar and 20C to 462C.

I'm not even sure a sphere that large and thin can be manufactured, because "clear" ALON starts as nearly opaque ALON, and a specialized grinding / polishing process produces the clear surface finish characteristic of "optical quality" ALON "glass".

I wish you could appreciate how difficult that will be to actually do, assuming it's even possible.

Making a very small but very robust ALON "marble" with a nuclear-powered LIDAR laser mapping camera / communication laser sealed inside, which is heavier than the Venusian "air" (mostly CO2), but can drift for a very long way using its attached BNNT fabric streamer (because BNNT is highly resistant to acid, temperature, and pressure while being exceptionally light), will be much much easier to actually do. The "glass" portion of the probe will be quite capable of resisting the temperatures and pressures, so it doesn't require any complex pressure regulation device. It can either be pressurized and sealed at the manufacturing plant, or left completely unpressurized because it's strong enough to withstand the temperature and pressure near the surface without any internal gas pressure (camera / electronics sealed into the glass marble under a hard vacuum). At 24mm diameter, the ALON-protected device can still resist the temperatures and pressures due to inherent tensile strength of the material at that size, in accordance with ye olde square-cube law which we just talked about. Eventually, gravity will bring the camera down onto the surface of the planet, but not before it maps many miles of the surface from below the thick cloud layer in the upper atmosphere above it using its onboard laser, and then returns that data to the probe release / scattering balloon orbiting above it.

I suppose something similar could be done from orbit using MMW radar or from an atmospheric balloon, but the overriding reason to get closer to what you're mapping is greater precision. Short-wavelength radar can tell you what the topography is, but lasers do a better job of telling you what it's made from, thus which sites you might want to send surface rovers to explore in greater detail. The entire surface is visually obscured from orbit. It could be the case that only certain surface features are worth mapping from within the atmosphere using LIDAR and then fewer still worth exploring using rovers. For example, if it turns out that most of the surface is covered in Sulfur, but at a handful of locations it's covered in something else, then we want to know what's different or unique about those locations and why.

tahanson43206 · 2022-11-27 16:20:27

For kbd512 re #59

Thanks for continuing to add hefty (and healthy) content to this topic!

It's worth reminding any readers we might have, now or in future, that this undertaking started with one of Void's boundary stretching visions.

Void has gone on to bigger and better things, but the process he started lives on in this topic, for as long as the members see potential for success.

We started with glass, transitioned to ALON, and now may find ourselves having to make another transition, if ALON turns out to be a dead end.

The balloon shell needs to be flexible as a polyethylene hydrogen balloon, but able to survive at the temperatures of the surface of Venus.

A soap bubble is made by injecting air into a liquid that has been created by combining various materials so that the needed properties are present.

An ALON balloon would (presumably) be made in a way different from what is known at present.

As a thought experiment, has anyone tried injecting air into a molten mass of ALON?

I'd be surprised, but have NO idea one way or the other.

(th)

SpaceNut · 2022-11-27 19:46:49

You cannot send to Venus anything that is flexible if it's going to the depth of hell where conditions require a rigid solid shell. Remember that the shell will start out with a near zero atmosphere in it of oxygen and all of the stuff that we want to do observation with that are also not flexible.

These things just like the shell must be able to withstand a bump of two to the surface if its cannot be slowed enough to avoid it. Not to mention into a mountain or so when its floating near ground level. There is no means to refill the sphere as that would allow acids to come into the shell getting into the stuff within. We can only vent if needed to lower the sphere internal pressure as it rises from the external heating of conduction.

tahanson43206 · 2022-11-27 20:47:16

For spaceNut re #61

In your post, you've brought up several points ... we've dealt with some already, but repeating the answers is often helpful. This may be one of those times.

In addition, you've raised the question of acid again. Acid is found in the clouds, far above the surface. it is my understanding there is almost NO acid in the atmosphere near the surface. That would be something you might be able to help to clarify, if you can persuade Google or Bing to help.

Please see if the Soviets took chemical readings at the surface, and if those readings were shared with the rest of the world.

It would be helpful to know that there is (or is NOT) acid in the atmosphere on the surface.

There will be no bump at the surface. There is no need to do anything more than the Soviets did many decades ago. There is no need to invent a new landing system. The Soviet system worked fine. Let's use it for the next probe.

I am pretty sure the terrain on Venus has (by now) been thoroughly mapped, so all mountains, valleys and plains are known to meter accuracy. You can help by confirming that.

Your opening line seems overly assertive.

A dirigible does not have a solid shell. Why are you insisting on a solid shell of some kind? I am sure you must have a reason, but so far, you have not explained why you hold to that position.

I have tried (repeatedly) to explain that the purpose of the balloon envelope is to keep oxygen atoms in and Carbon Dioxide atoms out. There is no pressure difference. There is no temperature difference. The shell does NOT need to be rigid, and in fact (as kbd512 has pointed out) it would shatter if is is rigid.

You have offered another declarative sentence in the second paragraph:

Why would you suppose there is no means to refill the envelope?

I have covered that in mujltiple posts, and will try this one as well.

The reason to use Oxygen inside the envelope is that it is readily available from the atmosphere of Venus.

Helium is almost non-existent. Hydrogen is present but not at the surface. Hydrogen is available in the acids in the clouds.

Oxygen is available by admitting CO2 into the probe, extracting Oxygen and venting the CO for propulsion.

In your closing sentence, you've brought up temperature again. There ** is ** no difference of temperature between inside and outside.

We have an opportunity to develop Void's idea to the point it can be given to others for their review. The careful poking and prodding you (and kbd512) are doing is important to helping to build/develop a concept that will withstand scrutiny.

(th)

SpaceNut · 2022-11-27 21:51:17

If flexible balloon will tear on the first puncture point since it's going to distort shape as it goes through its temperature cycles from launch all the way down to the surface.

https://en.wikipedia.org/wiki/Venera

https://www.rbth.com/science-and-tech/3 … over-venus

I only found this 1 image and it looks dry but at what level above the surface we cannot tell where it begins.

Adding atmosphere to a balloon requires a pump since we need more than the pressure that is inside and that would be co2 from venus atmosphere.

https://www.nasa.gov/directorates/space … robiology/

https://www.nasa.gov/directorates/space … ropulsion/

https://solarsystem.nasa.gov/planets/venus/overview/

https://en.wikipedia.org/wiki/Atmosphere_of_Venus

Venus's sulfuric acid rain never reaches the ground, but is evaporated by the heat before reaching the surface in a phenomenon known as virga.

https://en.wikipedia.org/wiki/Sulfuric_acid

https://en.wikipedia.org/wiki/Atmosphere_of_Venus

Not sure at what altitude but its where the temperature will cause it to boil.

Atmospheric profile

So once released its going to see temperatures all the way to the surface change externally and internally until stable and during that total time of slowing the pressure inside will be venting to keep it below the burst point rigid or not.

kbd512 · 2022-11-28 01:37:49

tahanson43206,

30 Years Ago: Magellan Off to Map Venus By John Uri NASA Johnson Space Center

From NASA's article:

Venus has often been called Earth’s sister planet, mainly because the two are roughly the same size. And there the similarity ends. One significant difference is that Venus is covered by an opaque cloud layer that does not allow direct visualization of its surface. For this reason, early probes making flybys of Venus didn’t even carry cameras. In 1961, using Earth-based radar scientists were for the first time able to peer through the clouds and obtain very low resolution “images” of the surface of Venus. By the mid-1970s technology had improved so that Earth-based radars could provide surface resolution down to about 10 kilometers, but only of limited areas of the planet. The next step was to place a small radar instrument into orbit around Venus – what it lacked in size it more than made up for in proximity to the surface.
The first spacecraft to study Venus using radar was Pioneer Venus Orbiter, managed by the NASA Ames Research Center in California’s Silicon Valley, which entered a polar orbit around the planet in December 1978. Over the next 14 years, among other observations it mapped approximately 90% of Venus at a resolution of about 10 kilometers. Pioneer Venus found the planet to be almost perfectly spherical, unlike Earth which has a measurable bulge at the equator. Also, more than half of Venus’ surface is within 500 meters of the mean surface height. The radar imagery found two large continents, Ishtar Terra roughly the size of the United States and Aphrodite Terra about the size of Africa, as well as large-scale tectonic features such as rift valleys and volcanic calderas.
As good as the results returned by Pioneer Venus Orbiter were, scientists yearned for higher resolution radar imagery. The Soviet Union obliged by launching two spacecraft carrying Synthetic Aperture Radar (SAR) instruments with large antennas. Venera 15 and 16 entered polar orbits around Venus in October 1983 and during their eight-month missions mapped about a quarter of the planet’s surface to a resolution of 1 to 2 kilometers. During this time, NASA was planning its own mission called the Venus Radar Mapper, later renamed Magellan, with the capability to map the planet down to a resolution of 120 meters using SAR. Magellan’s prelaunch goal was to map up to 70% of the planet during one 243-day imaging period, equivalent to one Venusian “day.” The Jet Propulsion Laboratory in Pasadena, California, managed the mission.
Magellan became the first planetary probe to be launched by the Space Shuttle when it blasted off from the Kennedy Space Center inside Atlantis’ cargo bay on May 4, 1989, during the STS-30 mission. The crew of David M. Walker, Ronald J. Grabe, Mark C. Lee, Norman E. Thagard, and Mary L. Cleave deployed the 7,604-pound Magellan and its Inertial Upper Stage (IUS) the next day. One hour later, the IUS ignited to send Magellan on its 15-month journey to Venus. After several mid-course corrections, Magellan settled into a near-polar orbit around Venus on Aug. 10, 1990.
On Sep. 15, Magellan began returning high-resolution radar images of Venus’ surface, showing evidence of volcanism, tectonic movement, lava channels and pancake-shaped domes. During the 243-day mapping cycle that ended May 15, 1991, Magellan mapped 83.7% of the planet’s surface with unprecedented resolution, exceeding its pre-mission objective. The spacecraft remained healthy and NASA extended its mission to conduct an additional five 243-day imaging cycles, which in aggregate increased the area of the planet mapped to 98%. In addition to radar imaging, Magellan also made precise measurements of Venus’ gravity field and used the planet’s atmosphere to circularize its orbit in the first test of the aerobraking technique. During its final cycle, Magellan studied Venus’ upper atmosphere. On Oct. 13, 1994, after a series of controlled engine firings lowered its orbit, Magellan entered Venus’ atmosphere and burned up, having completed its highly successful mission during more than 15,000 orbits of the cloud-shrouded planet.
Magellan’s high-resolution radar global map of Venus, comparable in resolution to visible light imagery-based maps of other bodies in the solar system, provided scientists with a deeper understanding of Venusian geology and the role of meteorite impacts, volcanic activity, and tectonics in the formation of surface features. Volcanic features are very common on Venus, making up the majority of surface formations including vast lava plains, lava domes, and large shield volcanoes. Evidence of meteorite impacts is limited, indicating that the surface of Venus is relatively young, on the order of 800 million years old. Typical signs of plate tectonics are not present on Venus, indicating little or no continental drift activity. The images revealed little evidence of erosion or wind effects despite the dense atmosphere, and this is likely due to the extreme dryness of the Venusian atmosphere.

To be frank, 120m resolution is not all that accurate.

EOS Data Analytics - What Is Spatial Resolution Of Satellite Imagery Data?

Spatial resolution refers to the size of one pixel on the ground. A pixel is that smallest ‘dot’ that makes up an optical satellite image and basically determines how detailed a picture is. Landsat data, for example, has a 30m resolution, meaning each pixel stands for a 30m x 30m area on the ground. It’s considered a medium-resolution image, which can cover an entire city area alone, but the level of detail isn’t fine enough to distinguish individual objects like houses or cars.
This subdivision into low, medium and high is provisional, as imaging technology advances all the time. What was considered high resolution back in the 80s ‒ for example, NASA satellite data from Landsat with its 60m per pixel ‒ has become low in today’s standards. The finest resolution as of now is 30cm provided by very high-resolution commercial satellites.
Low resolution: over 60m/pixel
Medium resolution: 10 ‒ 30m/pixel
High to very high resolution: 30cm ‒ 5m/pixel

If 30m is "medium resolution", then 120m resolution is 4X more coarse, and now considered to be "low resolution" by NASA.

From USGS:

Light Detection and Ranging (LIDAR) is a technology used to create high-resolution models of ground elevation with a vertical accuracy of 10 centimeters (4 inches).

Handout 8: Sulfuric Acid in the Venusian Atmosphere - Source nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html

The clouds of Venus are made up of droplets of concentrated sulfuric acid (H2SO4). The cloud layer begins about 30km above the surface of Venus, and ends at about 60km above the surface. Below the cloud layer (0-30km above the surface of Venus) the atmosphere includes a “haze” of sulfuric acid droplets.

Any quantity of Sulfuric Acid at 462C is pretty corrosive stuff.

kbd512 · 2022-11-28 02:20:00

tahanson43206,

Making assertions has little to do with reality. Whether or not you claim there is no internal pressure and temperature difference, is irrelevant, because in the real world there will be a difference that must be managed. Can we at least talk about reality?

ALON is a solid material. It's high temperature and acid resistant, but not at all flexible. A traditional "blimp" is not going to get anywhere near the surface. However, we cannot make a "blimp" or "bubble" of any significant size using ALON material. We can make marbles out of it, though.

Flexible plastic-type materials that hold gas pressure and can also withstand Sulfuric Acid attack at 462C don't exist, so far as I'm aware. Stainless steel can be rolled very thin, and is resistant to hot Sulfuric Acid at low or high concentrations, but not intermediate concentrations. A 0.254mm thick 1m^2 steel sheet would weigh about 4.5lbs or so, so a 1m diameter sphere will weigh about 14.13lbs. I'm not entirely sure how that helps us if the goal is to "see" out of the sphere, but it's at least doable.

tahanson43206 · 2022-11-28 07:13:20

This post is about the manufacture of ALON

Surmet
Surmet is the only company globally, that manufactures ALON®. Taking over the development of ALON® from a laboratory demonstration stage in 2002, Surmet is proud to announce the commercial availability of ALON® in large volumes and in really large sizes.
Composition: Al23-1/3XO27+XN5-X
Density: 3.696-3.691 g/cc
Grain Size (typical): 150-250 microns
Structure: Cubic, Spinel
ALON® Optical Ceramic - An advanced transparent ... - Surmet
www.surmet.com/technology/alon-optical-ceramics/index.php
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In a side bar, Bing offers this collection, which may ? be from Wikipedia

Aluminium oxynitride
Aluminium oxynitride is a transparent ceramic composed of aluminium, oxygen and nitrogen. ALON is optically transparent in the near-ultraviolet, visible, and midwave-infrared regions of the electromag…
Chemical formula(AlN)ₓ·(Al₂O₃)1−x · 0.30 ≤ x ≤ 0.37
AppearanceWhite or transparent solid
Density3.691–3.696 g/cm³
Melting point~2150 °C
See more
Despite aluminum oxynitride’s ability to produce a superior transparent aluminum armor, this material has not been put into widespread use. The largest factor in this is cost.
However, for the time being, creating aluminum oxynitride is still far too expensive to make it viable for anything other than the most niche applications.
These characteristics make aluminum oxynitride have a very broad application prospect in the fields of national defense and aerospace.
Data: Wikipedia · tssbulletproof.com · riotglass.com · rboschco.com
Wikipedia text

The material has only been known for a few decades ...

AlON: A Brief History of its Emergence and Evolution
https://www.researchgate.net/publication/223721385...
Jan 31, 2009 · In the early 1970s in Japan, the United States and France it was found that additions of nitrogen into aluminum oxide resulted in new spinel-like phases. At about the …
Estimated Reading Time: 9 mins

(th)

tahanson43206 · 2022-11-28 07:48:40

As a follow up to the Bing discovery of the sole manufacturer of ALON(r), I filled out the contact form on the company web site.

It is normal for an inquiry of this nature to be filed without a response. There are many reasons why this could occur, and it is to be expected.

I closed the inquiry with this:

This inquiry is the result of a discussion about the challenges of designing a probe to survive the challenging conditions on Venus. The original inquiry arose from a request published by NASA, for suggestions for a rover that would operate for an extended period on Venus. The normal fate of an inquiry like this one is to be filed without a response, for a variety of reasons. However, it is possible the idea will stimulate thought within the staff of Surmet, and some good may come of it. (th) (Junior) Moderator, NewMars forum.

(th)

tahanson43206 · 2022-11-28 07:53:34

We should NOT expect a response from the manufacturer of ALON(r).

However, we are free to continue working on possible application of this remarkable material, without knowing what is possible.

It appears from the company web site, that the material can be fabricated in the shape of a dome, which implies (to me at least) that the material could be fabricated in the shape of a dome, and two domes can be joined to make a sphere.

In addition, there is NO requirement that the walls of a balloon for Venus ** have ** to be spherical. The sphere is the natural shape that flexible material assumes when it is used to hold a gas. However, a thin sheet of material can serve as the wall of a container to hold gas. A cubical shape for a probe "balloon" envelope is a possibility.

(th)

GW Johnson · 2022-11-28 14:09:41

At tahanson43209's request I looked through this conversation. I'm not sure what to make of all this, not yet. Y'all seem to want a lighter-than-air craft for Venus surface conditions. That's awfully challenging. Y'all seem to want to use oxygen as your lifting gas, somehow deriving it from the sulfuric acid. If you have a way to derive oxygen from H2SO4, you can also derive hydrogen, I would think. There's less of it, but it would have more lifting power, and in a CO2 atmosphere, it is effectively inert.

MW CO2 = ~ 44
MW O2 = ~ 32
MW H2 = ~ 2

density = P/RT = P MW/Ru T is proportional to MW. So at the same P and T, the relative densities of H2, O2, and CO2 are 1, 16, and 22, respectively. 22 - 1 = 21 basis units is a huge amount of potential lifting power for hydrogen in CO2. 22 - 16 = 6 basis units for oxygen in CO2 is positive for lifting power, but not by nearly so much as hydrogen. It is the difference in densities (not MW's) that creates the lift in any LTA design. The basis unit is the density of hydrogen at the flight condition on Venus, anywhere from surface to high altitude.

Myself, I'd go with the hydrogen as way-to-hell-and-gone more lift power available.

You will need to vent the lift cell envelope, whatever it is made of. That gets rid of the pressure-difference problem entirely, and incurs making make-up gas as you fly. Put the vent on the bottom, much like the vent in a hot air balloon. Now you are down to the loads on the envelope imposed to carry the payload, and any wind gust pressures or terrain impact forces.

A question: can ALON be made as a thin fiber with inherent flexibility the way silica glass can? I'm guessing this depends upon whether ALON is a real crystalline material or an amorphous super-cooled liquid (the way silica glass is).

Another question: and can such fiber (if it exists at all) be woven into a fabric? If so, that would make a far more survivable lift cell envelope for an LTA design.

Assuming a very tight weave, we would still need "something" to seal up the pores in the fabric. I have no clue what that might be. Maybe the NASA bunch that flew the inflatable heat shield have something which serves that purpose.

GW

Last edited by GW Johnson (2022-11-28 14:22:40)

Calliban · 2022-11-28 15:18:38

Tensile ceramic fibres, such as those used for ropes, nets or gas envelopes, are coated with a thin layer of polymer. This prevents stress fractures from forming as the fibres slide across one another. It would be difficult to find a polymer that will not boil or pyrolyse at 450°C. Maybe graphite grease can perform this function?

The choice of lifting gas is complicated by the extreme temperature. Hydrogen molecules are small. Finding a gas proof material that is both flexible, resistant to fatigue and impervious to hydrogen at 450°C, will be extremely challenging. The porosity of metals to hydrogen is a function of the lattice structure (BCC, FCC), the size individual crystals and the length of intermetallic bonds and thickness of the material. Grain boundaries are low density areas that will leak hydrogen more efficiently than could occur at right angles to crystal plains. But at 450°C, intermetallic bonds will be considerably longer than at room temperature, and the rate of diffusion even through crstal plains will be substantially greater. Thin metal foils will leak hydrogen rapidly, so a way must be found to produce make up hydrogen to balance losses. Otherwise, you may need to compromise with a heavier lifting gas with a lower rate of diffusion across the membrane.

You cannot really make intelligent decisions until you can quantify these problems. My hunch would be that metal foils, probably austenitic stainless, would be the best gas cell material. Careful pressure control is needed to minimise flexing of the material, which could result in fatigue damage. At 450°C, all steels are considerably more ductile than at room temperature, which is a good thing. Maintaining the gas cells at a slight but constant positive pressure prevents the flexing that could lead to damage. A single spherical stainless foil gas gas cell, could be allowed to expand to fill the tensile ALON fibre envelope. Essentially this would be a graphite greased, ALON fibre envelope with a stainless foil inner lining. Alternative lifting gases are water (MM =18) or neon (MM = 20.2).

Additional: Diffusion of hydrogen out of gas cells is a surface area effect. One way of minimising diffusion rate is to scale up the balloon. This does two things. Firstly, the total diffusion rate scales with surface area, but lift scales with volume. So a spherical balloon with twice the diameter will lose lift at only half the rate. Secondly, a larger balloon can be equipped with more or thicker layers of gas proof lining. The diffusion rate per unit area of gas cell will be inversely proportional to the thickness of the liner. Double the thickness and you halve the rate of leakage per unit area.

Last edited by Calliban (2022-11-28 15:41:12)

kbd512 · 2022-11-28 16:02:09

GW,

BNNT fiber can withstand the heat (700C to 1,000C in "air"), as well as Sulfuric Acid attack, but as you pointed out, a fabric weave tight enough to contain a gas like Hydrogen or Helium is functionally impossible to achieve. A thin stainless steel foil could also survive at either low or high acid concentrations, but would be attacked by moderate concentrations. You'd need the BNNT fiber to reinforce the foil, so the stainless would have to be "melted" into the BNNT fiber under vacuum. This is an example of a flexible nanocomposite material. These are primarily lab-based materials, but have been produced in modest quantities.

I still fail to see what the point is, of not simply using a loop-type streamer to drastically slow the rate of descent, so that the probe eventually lands but remains useful for some period of hours after initial release. The wind speed at 30km is about 35m/s. That's more than enough to cause a marble on a string to drift for many miles downrange. The winds on Venus, from observation, only flow in one direction around the circumference of the planet, so you pick the latitude you wish to release the probes over and the combination of wind and atmospheric density does the rest.

Calliban · 2022-11-28 16:52:13

If my sums are right, the density of the atmosphere at ground level is ~60kg/m3. That is 50x the density of air at Earth sea level at 15°C. Maybe a rigid aerodynamic vehicle would be a better choice?

Last edited by Calliban (2022-11-28 16:53:17)

kbd512 · 2022-11-28 17:31:12

At 30km in altitude, you're already at 220C+ and 9.85 atmospheres of pressure, but you're also below most of the clouds and haze obscuring the surface, so a high precision mapping laser should be able to cover huge swaths of the surface in a single pass. A drone could fly very slowly using stubby little wings to generate lift, given that kind of atmospheric density.

kbd512 · 2022-11-28 18:01:46

It looks like Toray has some polyamide resins that have a glass transition temperature of 454C or so, meaning a composite airframe operating at half that temperature, at 30km in altitude, should still have usable strength.

Properties and Applications of Toray High Temperature Composites

However, polyamides also dissolve in Sulfuric Acid, so some sort of near-perfect PTFE sealant must be applied to the surface of the craft, or it will literally "come undone" mid-flight.

Glass or Carbon Fiber for strength, high-temperature polyamide resin to hold the airframe together, and then a thick layer or several layers of PTFE, which can also withstand the temperature and has superb Sulfuric Acid resistance. The electronics can be near-conventional (Silicon-Carbide-based) at that operating temperature, with some material substitutions (such as Silver conductors to make up for the loss of electrical conductivity at elevated temperatures; about 65% of IACS at 220C).

tahanson43206 · 2022-11-29 08:16:22

In hopes of keeping discussion in ** this ** topic focused tightly on the unique set of problems to be solved at ground level, we now have a topic available for balloon proposals that will operate at higher elevations.

The suggestion of GW Johnson to provide an open vent at the bottom of the ground level exploration balloon is attractive in a number of ways.

The question I have is how to prevent CO2 from entering the cavity of the balloon, if it is open at the bottom.

I formed a mental picture of a hot air balloon on Earth, with the atmosphere inside and outside the envelope the same.

That would not be the case for the proposed surface exploration balloon, so I'm assuming a net outflow of Oxygen would be needed.

Can anyone provide guidance on how buoyancy would be altered in this situation? It is definitely desirable to be able to manage elevation as winds carry the instrument package around Venus. SpaceNut has reminded us there are terrain features (eg, mountains) that the balloon needs to rise above as winds carry the package along.

We have shown that Oxygen can provide 17+ kilograms of lift at the surface of Venus, per cubic meter of volume inside the balloon envelope.

Since Oxygen is readily available, more Oxygen can be added to the interior and pressure increased if the vent to the outside is closed.

Would the presence of more Oxygen inside the envelope cause lift to increase, if volume is held steady?

An alternative might be to simply add helicopter propeller(s) to the design, to provide for vertical impulse where a ground obstacle might loom in the path.

A successful design might include provision for more than one gas to be employed for elevation adjustment.

Since Helium is going to be difficult to obtain in Venus, a supply might be shipped with the vehicle and used in emergency situations, when other measures are inadequate to lift the package over a looming obstacle. However, once exhausted, that remedy would no longer be available.

(th)

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