kbd512 Postings

tahanson43206 · 2024-12-18 07:24:43

For kbd512 re Venus mining and exploration planning...

Invoking a Tesla robot is an interesting idea, but (in my opinion) it evades the responsibility of solving the problems everyone else working on this is going to be dealing with.

Your competition is most certainly NOT going to be depending upon an piece of equipment that is not under their direct control. I am following your lead in thinking that solutions can be found for all the problems of dealing with 500 Celsius as the working environment.

It seems to me reasonable to design all the intelligence you need into the drones you are going to deploy, so they interact with each other on the work site to accomplish whatever goals you set for them.

Void just posted a very nice visual image of the atmosphere of Venus. It shows clearly the boundary layers where humans could live in modest comfort, if not in complete safety. Science fiction writers have been describing the conditions at that boundary layer for some time, and from my perspective most of them seem to have understood the reality of what the explorers would be dealing with.

I'm hoping you will be willing to solve the control problems for the onsite machinery, so that we might be able to publish something that would stand up to the intense scrutiny it is going to receive.

Invoking a Tesla robot is going to raise eyebrows at best, and generate a bit of skepticism at worst.

(th)

tahanson43206 · 2024-12-18 16:19:36

For kbd512 re Focused Solar Propulsion...

Your recent discovery (and reporting) of new materials for collecting light and guiding it to where it is needed inspires this question...

Given that the problem to be solved is turning light (photons) through a right angle (ie, traveling from the Sun and then to the engine) I'm wondering if any of the discoveries you've found are able to solve that particular problem at the microscopic level.

In other words.... imagine a flat plate set perpendicular to the Sun's rays. Photons arriving at the plate might be collected by a one-way optical cable.

To my knowledge nothing like this exists, but if it did, the light could be directed along the plane in whatever direction is desired.

Current technology involves use of a mirror to bounce the photons 90 degrees.

But that means there needs to be a mirror to catch every photon.

A one-way optical cable would do two things.... It would capture the photon, and it would reflect it 90 degrees to travel in a desired direction.

In electrical circuits, such one-way devices are called diodes. Is there such a thing in optical circuits?

(th)

kbd512 · 2024-12-19 04:03:48

tahanson43206,

My competition...? Do you mean all five or six of us "internet Venus mining dreamers" located here on Earth? We'd be collaborating, not competing.

Can you imagine how intense the scrutiny would be after proposing a mining truck that either never breaks down, or one that repairs itself, in addition to driving itself?

I'd be far more skeptical of someone proposing all of that, as compared to a foot-mobile environmentally-hardened automaton. You can find pictures on the internet of a humanoid robot intended to explore the ocean floor, which has already been to depths / pressures well in excess of what would be encountered on the surface of Venus.

The control issues can be "solved" using a human-like robot that can easily move around in ways that a mining truck never will.

Helios Electric Motors

ULTRA HIGH TEMPERATURE BRUSHLESS MOTORS
Permanent magnet brushless motors (surface mount or interior magnet) to 550 °C (1020 °F) ambient
Synchronous reluctance motors (no magnets) up to and in excess of 550 °C (1020 °F) ambient
Helios motors can be designed to operate on the Venusian surface (92 bar, 462 °C, sulphuric acid atmosphere)!

tahanson43206 · 2024-12-19 07:34:11

For kbd512 re Venus exploration initiative...

Thanks for finding the references to electric motors that can operate reliably at the temperatures they will have to deal with on Venus, at the surface.

I've created a topic for Venus Exploration in the Projects category.

I am interested in your idea/suggestion of using a Tesla robot to coordinate activities of purpose built machinery on Venus (or anywhere in the Solar System)

it seems to me the idea is so attractive it will eventually come to pass.

However, in the case of Venus, it seems to me that design of a suitable protective environment for the robot would be a reasonable precaution, and design of such a protective environment should be possible with existing human capability.

The specific problem to be solved is design of a cooling system able to maintain 25 degree Celsius temperatures inside the cabin, by delivering heat to the external 500 Celsius environment at 1200 Celsius (or whatever elevated temperature makes sense).

A related concern is how the Tesla robot is going to control it's purpose built "team" of machines. Humans have invented a variety of ways of controlling machinery using the electromagnetic spectrum. I don't know the answer to this, other than noting that the Soviets used radio to send data from their probes to satellites overhead, but is there anything about the atmosphere of Venus at the surface that would preclude use of the electromagnetic spectrum to provide for command flow to machines and data flow back?

This next section is for readers who are not members of the forum:

The Project Category is visible only to registered members. If you would like to join kbd512 in thinking through, and documenting, procedures to design equipment for operation on the surface of Venus, please see the Recruiting topic.

(th)

kbd512 · 2024-12-20 11:11:04

tahanson43206,

In all probability, no human is ever going to visit the surface of Venus, unless they're going there to die. The power required to maintain a 25C cabin temperature within a very small cabin volume is enormous. Even with a substantial amount of insulation, it's still enormous. They're in greater immediate mortal danger at all times than virtually any environment found on Earth, to include war zones. Some environments are not amenable to human life, irrespective of all monies expended and protections afforded. If the only issue at play was heat or pressure or acidic vapor in the atmosphere, then we could probably devise suitable methods to overcome that. The confluence of all three immediately lethal environmental factors make long term surface survival on Venus a rather bleak proposition.

Venus Rover Design Study

Take a look at the power requirement to cool a 0.38m^3 volume spherical enclosure, with minimal penetrations for communications / cooling / etc, to 50C or even 250C. It's wildly impractical, which is why I proposed using heavy duty machines and automatons built with materials or components that have already been engineered to readily withstand such harsh environments over significant periods of time. I'm perfectly content with using robots to mine the surface of Venus, even if we have a colony floating in the clouds somewhere.

The Tesla robot is merely a visually descriptive placeholder. People know what they look like. Something with a similar physical layout / appearance / capabilities will be controlling the mining operations. I don't mean that specific robot design will be used without suitable and perhaps very extensive modifications. I'm talking more about the software that particular robot has onboard than I am about the machine built around it.

As far as how it would control the mining equipment, I tried to explained that. It's going to use a fiber optic connection that plugs into the machine's network of sensors and actuators. All the "computer control" happens inside the robot's "brain". There's no real point to putting yet another computer aboard the vehicle unless we're going to add all the other equipment for it to "self-drive". I didn't mean to imply that the mining truck or power shovel will have zero electrical power or anything of that nature, merely that control over the machine will be exerted optically / photonically since borosilicate glass for the photonic chips and fiber optic cabling has no real issue operating at temperatures well in excess of those found on the surface of Venus.

There are certain materials that emit electricity when struck by light with a given wavelength, such as thermal photovoltaics (TPVs). Thus the optical sensors and control system will, for example, "steer the vehicle", by sending an optical signal into a TPV switch, which in turn actuates the steering gear with an electric motor / solenoid, in order to "turn left or right". Said electric motor won't be cranking on the rack-and-pinion, though, merely opening or closing a hydraulic valve that diverts some of the supercritical CO2 circulated through the vehicles primary systems (engine, transmission, brakes, steering gear, dump bed hydraulic cylinder) by its prime mover (a sCO2 gas turbine generating hydraulic power). That means the electric motor can be very compact and light, relative to what it's controlling / regulating. That means there's not a byzantine maze of hydraulic or electronic actuator control circuits running from the cab of the vehicle to whatever is being "controlled".

The described control scheme for all the functional "control bits" of the vehicle probably won't come to the same weight as a singular all-mechanical hydraulic control circuit or all-electrical control circuit. Since there are no moving parts between the machine operator and control valve solenoid, it's going to live a lot longer and require far less maintenance. The power requirement for this control scheme is reduced by orders of magnitude over a purely electrical or purely hydraulic scheme. Say that all of these systems did "break" in operation. How much easier will it be to replace a fiber optic cable vs all the mechanical or electrical devices required to accomplish the same task? How much easier would it be to troubleshoot?

Think about why we replaced electrical and mechanical control linkages aboard the F-35 with fiber optics. It's probably all about weight and maintenance reduction. The reduced electrical power draw was merely a side bonus benefit. Electrical systems aboard aircraft are subjected to heat, vibration from the engine (gas turbines still vibrate, but at higher frequencies), and all the mechanical flexing that electronics and electrical connections love so much. On top of that, there is corrosion, especially in or near maritime environments. The F-35 still has a very powerful electrical system, but the reason for actuating control surfaces through fiber optic cabling leading to an opto-electro-hydraulic actuator was related to solving environmental problems. The cabling needs to be light and use the least amount of power. The electrical connection needs to lead back to the electric generator driven off the engine. The control response needs to be smooth and strong to overcome resistance from air flowing over the surface, which is why a small electric motor inside the actuator generates hydraulic vs electrical actuation force to produce both high power and high precision control of that power beyond what any kind of electric motor of equal size and weight can produce. Prior to fiber optics, they had these big / thick / heavy EMI shielded electrical cables leading all the way back to the flight control computer located near the cockpit. Said electrical cables were, I think, over a quarter inch in diameter and collectively all the EMI shielded signal cable runs weighed close to 1,000kg. They tried two solutions. The first was CNT shielded electrical cable. The second was optical cable. The first method greatly reduced the weight, but not the power draw. The optical method reduced both, and was much cheaper than CNT wiring was several years back, so guess which solution they went with? Now the surplus electrical power is available for other applications to take advantage of. Although not terribly meaningful at F-35 flight speeds, an optical system also responds faster to control input from the pilot.

All components used in my described control scheme are intrinsically capable of withstanding the heat and pressure without additional protections or power draw for active thermal cooling. We could use electrical signals through many miles of wiring, but then we need signal wiring and insulation capable of handling the heat and chemical attack, as well as electronics to send those signals, none of which are capable of natively operating on Venus, and we must resort to higher voltages and amperages to achieve that same control, due to greatly enhanced electrical resistance at 482C. The ampacity of electrical wiring beyond 180C isn't listed anywhere, because the plastic insulation we almost exclusively use would melt. In practice, nobody runs wiring that hot unless they have no choice. I think using tech that's not up to the task is a rather pointless design complexity when we have optical computers, optical-to-electrical signal converters (TPVs) to behave as on/off switches for small valve-actuating solenoid electric motors, and specialty electric motors which can be powered by a far more limited total number and length of electrical power cables, requiring far less precise voltage and amperage regulation.

Modern semiconductor-based computers operate at 1V to 2V, sometimes less. You don't have to experience much voltage variance to fry a chip, even when operating temperature control is not a problem. So we're either going to develop electrical power supplies with incredibly tight regulation at very high ambient temperatures, or we're going to "skip" using control electronics in favor of compute and signal delivery that has no real issue with "taking the heat". This system is still using electricity, but it's not trying to use it for everything when the weight and power draw wold be excessive.

What I'm not going to do is route mile after mile of high voltage / high temperature electrical cabling through these mining machines, with thousands of electrical connectors that need to be sealed somehow, merely to give our electrical engineers something to do. Just this year, someone came up with a commercial diamond-based transistorized integrated circuit device, capable of operating at 300C. That would be great to have, if not for the inconvenient fact that Venus surface temperatures are around 482C. Purely electronic or electrical control systems are not going to work on Venus in a practical way, which means we need a better computer control technology that is "natively" able to withstand much higher temperatures and pressures combined with chemical attacks. Borosilicate glass photonic chips, TPVs, and fiber optic cabling are the basis for "said technology".

How might we "power such an optical computer"?

Venus still receives an average of around 17.5W/m^2 of solar radiation at the surface, so I think we'd use that power to keep the photons flowing through the vehicle's onboard sensors. Purely photonic devices uses 1,000,000X to 10,000,000X less power than equivalent Silicon-based integrated circuit electronics to accomplish equivalent compute tasks. We simply don't need much optical power for that purpose, even when compared to modern electronics. An iPhone chip might draw a few Watts of power at most. 5W divide by 1,000,000 is a very tiny number. Since we won't be consuming a ridiculous amount of power in an effort to maintain electronics within survivable temperature ranges, we can then use the remaining thermal and electrical power for other purposes. Electrical power will be redirected into running lights allowing optical sensors aboard our controlling automaton / "Tesla robot" to "see" where the vehicle is headed, even when the surface is dimly illuminated. The vehicle's electrical system is by no means going away, rather control will be "mostly optical and some electrical" vs "mostly electrical and electronic". If someone invents an entire range of electronic devices capable of natively operating at 482C, then we might revisit this, but not until then.

tahanson43206 · 2024-12-21 10:05:58

For kbd512 re #180

Take a look at the power requirement to cool a 0.38m^3 volume spherical enclosure, with minimal penetrations for communications / cooling / etc, to 50C or even 250C. It's wildly impractical, which is why I proposed using heavy duty machines and automatons built with materials or components that have already been engineered to readily withstand such harsh environments over significant periods of time. I'm perfectly content with using robots to mine the surface of Venus, even if we have a colony floating in the clouds somewhere.

What do you mean by the expression "wildly impractical"?

You must mean something other than whether the machine works or not.

You must mean that it would take more work than you are willing to invest..

In my dictionary, if a procedure works and can put put into practice, then it is "practical".

A cooling system that can operate reliably for extended periods of time ** will ** inevitably come into being on the surface of Venus.

The reason should be obvious, but apparently it is not.

Human beings are going to want effective cooling when they explore hot places around the Solar System, so teams are going to be given the resources needed to achieve that objective.

What another person "wants" and what you consider "practical" are two decidedly different things.

We have seen that difference in other posts you have contributed to the forum archive.

Equipment that can explore the deepest part of the oceans was impossible until recent times.

And even when it became possible, folks might well have considered the equipment "impractical" because ** they ** could not afford to put it to practical use.

Now such deep ocean devices are being put to uses that most folks would consider "practical".

I would think it would be beneficial for the NewMars archive to contain a solid study of what it will take to build these surface equipment able to sustain a shirtsleeve environment for hours at a time.

It seems reasonable to me to presume the power needed to pump all that thermal energy can be supplied by a nuclear fission plant. It will generate plenty of heat on it's own, that has to be delivered the the external environment.

What I am hoping the forum will eventually contain is a solid study showing exactly how to do that.

There are humans on this planet already, with resources sufficient to fund a major initiative to put a long term exploration vehicle on the surface of Venus. We have already seen the Soviet Union put short lived vehicles on the surface of Venus. They weren't worried about notions of "practicality". They were interested in results, and after many failures they got results, which will stand in the record books of human achievement for as long as humans are able to keep records.

(th)

kbd512 · 2024-12-22 16:21:17

tahanson43206,

Whenever the probability of the environment itself killing someone significantly exceeds the possibility of us learning or gaining something of tangible value by sending them into that environment, I consider that a losing proposition, even if we can technically make it work. We probably have sufficient tech to send someone to go live in the clouds of Jupiter. They might even survive there for awhile. Unfortunately, the probability of them returning alive is low. That's what I meant by "not very practical".

Exploration and money making propositions involve two entirely different realms of engineering. I'm not saying nobody can, for a brief period of time, visit the surface using an incredibly well protected vehicle, just to see what's down there. I would never put someone's life in danger, merely to operate a mining truck down there. You're conflating these two very different projects and acting as if they're the same thing when they're clearly not. My posts about Venusian mining were related to money making. Putting people in trucks on the surface of Venus doesn't assist with that proposition, so I opted not to do it.

The cooling system required to keep someone from being baked alive likely has to be a small nuclear reactor to continuously generate the power and temperatures required to do so. That's the least concerning aspect of survival on the surface of Venus. All components of the life support system have to function in a near-flawless manner, but perhaps one of the most critical of the many involved components are simple seals to keep all that lethal stuff out. Sealing against a combination of Sulfuric acid and a supercritical solvent, at 482C, is a mighty tall order. You have Fluorine, Chlorine, Hydroxl, Sulfuric acid, and supercritical CO2 to deal with, combined with temperatures sufficient to melt Lead. It's like a hazmat bingo game. All that's really missing is lava and radiation from a reactor.. Oh, wait.

Let's do a quick thermal power calc for cooling a 2.75m outer diameter and 23.75829m^2 surface area spherical cabin for our Venusian Caterpillar 797 facsimile.

Q = k * A * (T1 - T2) / d
Q = heat transfer rate in Watts
k = thermal conductivity in W/mK
A = surface area in m^2
T1 = hot surface temperature
T2 = cold surface temperature
d = thickness of the insulative material, in meters
482C = 755.15K
25C = 298.15K

Aerogel Insulation Thermal Conductivity at 500C: 0.06W/mK. Let's use 100mm thick insulation, so 0.1m thick.

Q = (0.06 * 23.75829 * (755.15 - 298.15)) / 0.1
Q = (0.06 * 3.75829 * 457) / 0.1
Q = 6,515W

Assume a 45% efficient thermal load transfer for cooling the cabin, which is actually quite good.
6,515W / 0.45 = 14,477W of power devoted solely to cooling the cabin.

For 200mm thick insulation: Q = 3,257W; thermal power = 7,238W (still quite a lot of power)

To avoid buckling with 1,367psi of external pressure applied to the sphere, I'm using a 3.5X safety factor, quite similar to the safety factor that ASME applies to boiler pressure vessels. The sphere must withstand 4,784.5psi (almost 33MPa) of applied external load for it to pass a basic BPVC safety check.

Buckling of a Tube Calculator

Using the above tool, this sphere must be about 60mm thick.

2.75m is the sphere's outer diameter, and it's 60mm thick, so:
10.889m^3 (vol. of 2.75mD sphere) - 9.525m^3 (vol. of 2.63mD sphere) = 1.364m^3 (volume of the steel)
1.364m^3 * 7,850kg/m^3 = 10,707.4kg of steel for the cabin (9,743.7kg on Venus)

I would cast this sphere as a single piece, use precision grinding to provide absolute uniformity, WPC treat it (micro shot-blasting), and then coat it with Silicon Carbide for hot Sulfuric acid resistance. The interior would use blocks of aerogel insulation wrapped in CarbonX fabric.

This proposed vehicle cabin is only modestly larger than the 2.1m diameter bathysphere that Jacques Piccard and Don Walsh used with Trieste to explore Challenger Deep, but significantly lighter (10,707kg vs 14,250kg for Trieste's bathysphere). However, the bathysphere carried by Trieste did not include 100mm to 200mm of interior insulation. Jaques Piccard had a forged and welded 89mm thick bathysphere produced for exploration efforts prior to the one for Trieste, which was 2.4m in diameter.

That seems pretty heavy. Perhaps we can use a Titanium alloy to roughly halve the weight, but the walls would need to be even thicker. Eglin ES-1 steel would be more or less guaranteed to work (negligible mechanical property loss at 482C), but would require some kind of Silicon-based surface coating (SiC) to withstand the chemical attack. I don't know enough about Titanium casting alloys to know if they would still be a good choice at 500C. My gut-feel on this is that steel is the correct material to use for this safety critical application, because the behavior of Titanium alloys is so hyper-dependent on purity, exact alloy composition, and the quality of the casting / forging / welding work. If I'm wrong about this, then we'll use Titanium and save several tons of weight. The application of Titanium to the frame is not about increasing strength, it's about decreasing weight for a given strength. Virtually any steel or Titanium alloy will require SiC coatings to survive the chemical attack.

Mechanical Properties of Titanium Alloys

If you want to add a window for the operator to be able to physically see out, then the pressure vessel is going to weigh more. I would count on adding 1 extra ton of weight for this feature. The cabin requires some kind of hatch, so it may as well be in the front of the vehicle where another vehicle can easily maneuver around the truck to transfer the equipment operators.

A toughened double-pane of borosilicate glass will be our transparent window material of choice, perhaps with a layer of highly pressurized Argon to limit the heat transfer rate. This will be a single piece design. A seal will be achieved using a multi-layer steel gasket. It's not possible to temper borosilicate glass, but it can be strengthened / toughened using a heat treatment process. Perhaps flake graphene could be mixed into the molten glass for additional toughness and resistance to cracking. The compressive yield strength of borosilicate glass is pretty spectacular. Were it not for its equally spectacular thermal conductivity, roughly 4X that of steel, I would seriously look into using a toughened glass for the entire cabin. Speaking of which, that functionalized aerogel which allowed sunlight to pass through but trapped or prevented heat from escaping, for the solar thermal power tower application, would be well worth looking into, since it would also prevent heat from entering. If it was possible to use the material that way, the cabin could be a "greenhouse" enabling visual observation in all directions, weighing perhaps a quarter of what an equally capable cast steel sphere weighs (in terms of compressive yield strength, not tensile strength). However, that's a significant tech and manufacturing process development investment to make.

tahanson43206 · 2024-12-27 20:18:52

For kbd512 ....

First, thank you for https://newmars.com/forums/viewtopic.ph … 81#p228781

Update Saturday 2024/12/28 ... the experiment failed. i'm not surprised, but the failure mode was ugly:

Info
Bad request. The link you followed is incorrect or outdated.
Go back

The link should not have worked, but the error message is incomplete. The link is correct and it is not outdated.
It is simply declined since the requester is not a logged in member.

That post is in RobertDyck's Project on greenhouses. This is an experiment to see if non-logged in members can see it.

Second, thank you for your additional thinking (and writing) about the Venus challenge.

I would appreciate a quick statement about Post #182 that answers the question of how a reactor could cool itself (and it's enclosure) far below ambient temperature at the surface of Venus. I looked throught the post, but did not see an answer.

I think the thermodynamics problem is solvable, but at this point, I have not seen (or perhaps have not recognized) a definitive answer.

I think that Calliban might be able to solve the problem, but for the moment at least, his attention is elsewhere.

The problem of how to run a reactor on Venus is simple enough:

Ambient temperature is on the order of 500 Celsius.

Radiator temperature needs to be greater than 500 Celsius, and i am offering 1200 Celsius as a round number that provides 700 degrees for a heat engine to operate.

The reactor itself will operate at some temperature greater than 500 Celsius, but my understanding is that the operating temperature of a reactor can vary over a wide range, depending upon the design.

What I cannot figure out is how a heat engine operating in an environment with a floor of 500 Celsius can pump coolant up to 1200 Celsius so the thermal energy can be delivered to the atmosphere of Venus, and the cooled fluid can be delivered to where it is needed inside the vessel.

Regarding weight ... It seems to me it is not necessary to be overly constrained by vehicle mass. The reason is buoyancy.

While buoyance is NOT much of a factor on Mars (as thoroughly discussed in this forum) it ** is ** a feasible possibility on Venus. The atmosphere at the surface is reported to be at about 92 atmosphere's pressure, and composed of CO2 (priimarily). It should be possible to compute the lift that can be achieved if a volume of gas lighter than CO2 is employed for that purpose.

Quick check: Carbon Dioxide is 44.009 grams per mole
Quick check: Atmosphere of Venus: 3.5 percent molecular nitrogen
Quick check: Nitrogen 28 grams per mole

Therefore if you make a lift compartment in your vehicle, you can obtain lift of 44-28 >> 16 grams per mole

If this possibility is of interest (and I hope it is) please investigate how you might design a vessel to take advantage of it.

The situation is not all that different from a deep sea exploration vessel on Earth, The mass of the vessel has to be great enough so that the vessel sinks to the bottom of the ocean, but the lift space needs to be great enough so that when water is replaced with oxygen the vessel rises.

(th)

kbd512 · 2024-12-28 14:58:51

tahanson43206,

Consider a 5m outer diameter sphere with 50mm (0.05m) thick Ti-6Al-4V alloy walls:

CO2 bulk density at 93bar pressure and 482C temperature: 64.91464kg/m^3

V1 = 65.44985m^3 for 2.5m radius / 5m diameter sphere
V2 = 61.60087m^3 for 2.45m radius / 4.9m diameter sphere
65.44985m^3 - 61.60087m^3 = 3.84898m^3 (volume of Titanium alloy metal for 50mm thick walls)
3.84898m^3 * 4,430kg/m^3 (Ti-6Al-4V bulk density) = 17,051kg
65.44985m^3 * 64.91464kg/m^3 (CO2 bulk density, 93bar, 482C) = 4,249kg
Apparent pressure vessel mass after buoyancy effects: 12,802kg
Venus Surface Gravitational Acceleration Compensation: 12,802kg * (8.87m/s^2 / 9.80665m/s^2) = 11,579kg

Buoyancy provides a 24.92% mass offset for the Titanium alloy spherical pressure vessel itself, which ignores the weight of the person(s) inside, atmosphere, and life support / sensor equipment inside the pressure vessel with the occupant(s). The lower surface gravity on Venus provides an additional "assist" with the mass of the pressure vessel. The apparent weight of the pressure vessel on Venus is still 11,579kg.

That is a very heavy singular vehicle component, quite similar in mass to an entire semi-truck without any trailer attached to it, but merely for a rather small pressure vessel shell. No other vehicle component masses have been taken into account, so we're talking about something that's likely at least as heavy as a fully loaded semi-truck, or a light main battle tank. The M46/M47/M48/M60 "Patton" series of main battle tanks from the Cold War era were around 44,000kg to 50,000kg for comparison purposes. If 1/4 of the mass is allocated to the passenger cabin, then the other 3/4 of the mass is allocated to the chassis, drive train, and energy storage or production. My take on this is that buoyancy, while it does provide a very significant mass offset, won't be comparably significant to the masses of all the systems keeping people alive and moving.

tahanson43206 · 2024-12-28 15:08:02

For kbd512 re #184

Thank you for picking up the idea of using buoyancy to sustain the vertical position of the probe!

Please examine deep sea vessels. I think you will find that the buoyancy chambers for most non-military equipment are ** outside ** the volume used for passengers or equipment. Your vision of a sphere seems to me to be on the right track, if you just add some external buoyancy equipment.

You'll be able to hover at precise altitudes while maintaining position against the modest winds using fans.

GW just confirmed the Carnot efficiency for the fission reactor as a positive value, on the order of 11% with ambient at 500 and reactor at 800.

We (this forum) may be moving toward something that would actually work.

(th)

kbd512 · 2024-12-28 21:50:59

tahanson43206,

Seawater's density is around 1,025kg/m^3, which is almost 16X denser than CO2 at 93bar. Systems that use supercritical CO2 as a working fluid use much higher pressures to achieve much higher densities. Here on Earth, submersibles frequently use exterior syntactic foam (120kg/m^3 to 600kg/m^3) coatings to achieve neutral buoyancy at great depths. Syntactic foam melts at around 121C, up to 232C for high temperature foams. That's not going to work on Venus due to the surface temperatures involved. There are other solid materials that can function at higher operating temperatures, but most of them are aerogels which may also require some sort of pressure-resistant envelope.

A Review of High-Temperature Aerogels: Composition, Mechanisms, and Properties

Polyimide-based: 1,000C
Zirconia-based: 1,300C
Silica-based: 1,500C
Carbon-based: 2,500C

If we could use some sort of toughened or tempered glass, that would fall within the range of 2,200kg/m^3 and 3,700kg/m^3, which makes the entire proposition of "using buoyancy on the surface of Venus" a much more technically feasible feat of engineering. I don't think metals are practical to use, unless we're talking about 3D printed Titanium alloy structures with void spaces. I would not use them as part of large habitable pressure vessels, but could see them being used as structural parts of a vehicle chassis. Basically, we have cast Iron or Titanium alloys or toughened glass materials which are suitable for large pressure vessels at 482C, but not much else.

Any kind of composite, such as a Sylramic fiber embedded in a metal matrix, will be very hard and resistant to deformation, but the heat and pressure will exploit any void space (defect) in the bulk structure, fracture it, and crush it. This is precisely what led to the implosion of the Titan deep sea submersible, albeit using a Carbon fiber reinforcement embedded in a polymer matrix. The polymer resin matrix was the weak link in that case, not the fiber, but it mattered little to the end result. Could a metallic matrix and high strength fiber combination succeed where plastic and fiber failed so catastrophically? Possibly. The level of manufacturing perfection required will be exceptionally difficult to master.

Assume a 60:40 fiber-to-metal ratio in the following ceramic fiber metal matrix composite material:

2.3093898m^3 is Sylramic fiber at 2,950kg/m^3, so 6,813kg, and 1.5395932m^3 is Ti-6Al-4V at 4,430kg/m^3, so 6,820kg, for a total of 13,633kg. The bulk density of this CMMC is about 3,542kg/m^3, slightly lighter than Alumina (Al2O3), but with the tensile strength of a low-spec maraging steel like C-250. It's a big step in the right direction, at 10,236kg with atmospheric buoyancy accounted for, 9,258kg final apparent weight with Venus surface gravity, but not neutrally buoyant.

That means a practical pressure vessel material, which remains neutrally buoyant without considerable "help", is effectively limited to toughened glasses as structural materials. In many respects glass is a near-ideal material for its exceptional compressive yield strength, temperature resistance, and chemical attack resistance. There are no temperature-resistant metal matrices, nor suitable Silicon-based ceramic fibers, with densities low enough to produce composites that can remain at least neutrally buoyant, with reasonable volumes, at the temperatures, pressures, and atmospheric densities involved. Even when using glass as a pressure vessel, most of this neutrally buoyant vessel's internal volume must be void space.

I rate this proposition as technically feasible by using advanced materials. It's certainly fun to think about, but I'm more interested in how we can exploit the mineral wealth of Venus for our collective benefit than a high tech "atmospheric submersible" exploration vehicle that likely cannot physically accomplish exploration tasks cheaper than metallic robotic surface rovers endangering nobody. It can move about without surface contact and that might be useful, but the idea here is to pick up and sample pieces of rock, or to drill down a ways to sample rocks. If I put a person inside that vehicle, then a lot or mass is immediately reserved for keeping them alive.

If I have a robotic rover that moves around at low speed on wheels, then it costs a lot less money because it can be made rather cheaply using steel or Titanium or high temperature composites, and it can last a decade or longer, as our pair of nuclear-powered Martian surface rovers have proven. The vehicle chassis and power train components were relatively cheap and fast to develop. We used a lot of Aluminum on the Curiosity and Perseverance rovers to save weight, and for cryogenic temperature compatibility. Only the solar and battery power systems, electronics, and navigation systems cost a lot of money to develop. If my computer control systems and scientific instruments will natively run at 482C, as photonics-based computer control systems will, then I don't require a power-hungry cooling system, so my total power requirements remain rather modest.

The vehicle you described is effectively an "airship". What do we know about airship operations? They tend to crash frequently when they venture too close to the ground. This "buoyant surface airship" would operate close to the ground by necessity. At high altitudes, airships can remain aloft for years, decades potentially. Operations close to the ground are intrinsically dangerous for all airships. Making contact at any significant speed is how they get damaged or destroyed. I guess the real question is, can you power an airship using less power than a ground vehicle while making it weigh significantly less? If so, then an airship might be cheaper to deliver and operate. I question how technically feasible that is, based upon extensive Earth-bound airship operational experience accumulated over the past century.

I would be willing to further entertain this idea if you explain what the "killer app" is for this near-surface Venusian airship- something it can do better than competing vehicle designs. Can it map the surface more efficiently? Can it traverse volcanic lava fields with little risk of hull loss? What kind of mission do you envision this vehicle performing?

kbd512 · 2024-12-29 19:44:54

Forum User File Uploads Test File

CV-60 USS Saratoga:

tahanson43206 · 2024-12-29 20:57:13

For kbd512 re #187

Thanks again for setting up the file and the link to the file, to show what is possible.

I am wondering if this is one of the vessels you served on?

***
This next is a follow up to our discussion in the Google Meeting.

Your suggestion of dropping a sea anchor below the habitat at 55 kilometers brought this thought to mind:

There is a band of the atmosphere below 55 kilometers where the sky is clear.

I bring this up because (a) that would be good place for a sea anchor to ride and (b) that would be a great place for humans to spend some time if they want to get ouf of the clouds which (I understand) are a feature of life at 55 km.

To put a bow on this concept.... your idea of a glass observation dome might work at this altitude, so that humans flying down to that altitude for the view would be protected from whatever conditions exist outside at that point. The vehicle that would make this descent could be strung out on a line like a kite, and it should be able to maneuver with airfoils. There might be some reason to do this other than just for fun, but even if it is just for fun I would imagine humans on Venus would greatly value the opportunity to spend some time in this little vehicle.

Note: The vehicle definitely needs to be equipped with buoyancy backup equipment, in case the line to the habitat breaks.

(th)

tahanson43206 · 2025-01-03 18:03:40

For kbd512 re http://newmars.com/forums/viewtopic.php … 76#p228876

Thanks for showing the link to Gunter's web page.

What an amazing volunteer effort!

I sure hope folks chip in to help with the expenses!

I was amazed to see how may Centaur flights have taken place, and how many high value payloads were given their start from this stage.

(th)

tahanson43206 · 2025-01-04 07:30:42

For kbd512 re: http://newmars.com/forums/viewtopic.php … 79#p228879

Your customer for this concept would be the Taiwanese.

They have a tremendous advantage in their dispute with Chairman Xi.... they have ocean around them where they can deploy millions of these devices, in floating stacks with vertical storage containers similar to those on submarines.

If you want to have an impact (pun intended) you can send a copy of your post to the Taiwanese Embassy.

The NewMars forum is a good place to start, because you get (or may get) feedback to help you fine tune the proposal.

But to change the future, you need to place your idea where it would do some good.

(th)

GW Johnson · 2025-01-04 09:28:50

Good idea.

A nuance for some types of targets: the faster the penetrator speed at strike, the smaller the penetrator mass can be. Cruise to target vicinity at high subsonic, then fire a small solid motor to take your penetrator to nearer Mach 3 than Mach 1. You can use a smaller penetrator for the same effect, and get more range out of your weapon that way.

One of the things I worked on got the same armor-or-bunker penetrating capability as a 16 inch battleship projectile out of a tungsten or depleted-uranium penetrator about 3 inches in diameter. It flew at Mach 5. Tube launched, just like a bazooka. Really good tank and concrete pillbox destroyer, it could have been. (Didn't sell, because the prime wanted to put unnecessary beam-rider guidance on a projectile with only a one-second flight time, just to jack the price up.)

GW

Last edited by GW Johnson (2025-01-04 09:30:55)

tahanson43206 · 2025-01-04 15:06:31

For kbd512 ....

Noting GW's appreciation of your kinetic weapon idea.... Glad to see the support for your idea.

I'm reminded of the idea of tossing dead weight at the opponent, in earlier times. In those days the dead weight I'm thinking about were solid cannon balls, although those were preceded by elastic spring toss equipment using stones.

This post is about the interesting series you just added to the weapons topic, and specifically a reference to temperatures and pressures...

Turbine rotor power density is 200kW/kg at 715C and 250bar of pressure, using Haynes or Inconel superalloys, or 1,000kW/kg at 1,200C, using Sylramic fiber with a Silicon Carbide matrix (a CMC used in the convergent-divergent nozzles and other hot section components of afterburning turbofans). Most of that power density increase is due to the mass reduction of CMCs vs superalloys (2.95g/cm^3 for Sylramic or SiC vs 8.97g/cm^3 for Haynes 230, so 3X lighter), and the rest is higher operating temperatures and pressures, plus higher tensile strength at 1,200C than Haynes at 800C. Sylramic is a SiC fiber similar to Carbon fiber, but created for 1,400C applications. Ramp-up / ramp-down rates are at least as good as gas turbines. CMCs can crack, like any other ceramic, but SiC is highly resistant to thermal shocks.

The question I have is whether this equipment might work comfortably on Venus? In the Venus topic(s) we've established (to my satisfaction at any rate) that a nuclear fission reactor can indeed keep it's cold side cold enough to achieve Carnot efficiency for the electricity production equipment. I was thinking of fairly ordinary electricity production equipment, but your post(s) in the Weapons topic have me wondering if the power production might be done outside the hull in the open environment, with due protection from the atmosphere.

(th)

tahanson43206 · 2025-01-04 20:33:31

For kbd512 re kinetic weapon and delivery method.

I note your suggestion of making these weapons to be propeller driven. If your goal is to provide Taiwan with the ability to defeat an invading force of thousands of vehicles of various kinds, I like the idea of taking out the supply services on the mainland.

However, it seems to me unlikely that Taiwan would want to base these thousands of weapons on their land. My question for you is... if you go with this propeller system can you base it in floating tubes offshore, so that China cannot take them out before starting the invasion?

The Taiwanese are going to need thousands of these machines, and each one must be programmed to find the target without GPS if China takes out GPS ahead of the invasion. Is there an inertial guidance system that can backup GPS if GPS is down or compromised?

(th)

kbd512 · 2025-01-04 21:28:13

tahanson43206,

This is dual-use tech. It can be used to generate power here on Earth, on Mars or Venus, and its temperature tolerance and longevity are sufficient to qualify it as a power plant for ships and aircraft.

I don't know if you've detected a theme to my posts, but I've been looking at "generation beyond" technologies:

1. sCO2 and RamGen supersonic CO2 compressors qualify as the generation beyond conventional gas turbine engines. The power density of the components is wildly beyond anything we use now, with volumetric power density approaching that of our most powerful nuclear reactor designs. They're like rocket engines that can run at full output for decades. They can be used in combined cycle engines to propel the next generation of flying vehicles. Prior to sCO2, unless we're talking about rocket engines, there was no such thing as a 200MW engine that weighed 1,000kg or less. Most of what humanity uses is shaft power, rather than pure thrust, which is what a chemical rocket engine is so superlative at providing.

Even for rocket engines, however, sCO2 powered pumps could use heat from the main combustion chamber and nozzle to power the pumps, rather than from pre-burning the propellants, in order to produce gaseous propellant to feed into the main combustion chamber. This would mean more of the propellant gets burned in the combustion chamber, rather than requiring 10s of megawatts of thermal power to drive the turbopumps by combusting propellants in pre-burners and then feeding the combustion products through the main combustion chamber / injector pintles, which reduces exhaust temperature and thus velocity. The LH2 RS-25 turbopump, for example, requires 52MW of power to drive the fuel into the combustion chamber. IIRC, there are 4 pumps used to feed the RS-25. Thermal efficiency is probably not that great, because it's such a small device.

I would wager that somewhere between 100MW and 200MW of potential power is being siphoned off to drive those four (LPFTP, HPFTP, LPOTP, HPOTP) "engines". For an engine that already has a lower power-to-weight ratio when compared to something like the Merlin or Raptor, it would be nice if we could extract every last bit of "oomph" out of the propellants, while using much lighter materials than superalloys or Copper. The "heat exchanger" would weigh 500kg if 150MW is the thermal power requirement, with a 2.5X factory of safety. RS-25's main combustion chamber (~200kg) and nozzle (~430kg) already weigh more than that, so Sylramic and 3C-SiC would provide a considerable mass savings. RS-25's high pressure fuel turbopump achieves about 168kW/kg. A sCO2 turbine can readily achieve 1MW/kg, so 150kg for all pumps. The heat exchanger is a component that must exist, merely to have a rocket engine at all.

2. Photonic chips, data storage, and solar photon transport also qualify as generation beyond compute / natural power devices, capable of 10^6 to 10^7 greater energy efficiency, as compared to Silicon-based semiconductor integrated circuitry. True 3D hologram generators that project photons into three dimensional space above the projector, rather than optical illusions to "trick the mind", are just now becoming economically viable. That little parlor trick has been decades in the making, but is actually being sold right now, but for many thousands of dollars for a relatively small projector.

3. CNT and BNNT fibers definitely qualify as the generation beyond Carbon Fiber as a structural material, with respect to their mechanical properties. We desperately need these materials in bulk to build the next generation of aircraft and rockets. Heck, wiring and concrete are already getting in on this action. It's the next big thing in materials tech.

4. I would say that UHTCs, aerogels, and multi-material tiles comprise our "generation beyond" reusable heat shielding materials.

5. On the battery and electronics front, we are make slow but dogged progress on Sodium-ion, solid state batteries, recyclable photovoltaics, and also, surprisingly, a new kind of semiconductor material that is actually the thin film photovoltaic material repurposed for computing. Since we've refined this tech so highly, true breakthroughs are few and far between, but we're literal lightyears ahead of where we were 50 years ago.

I'm trying to see what's out there that we have developed to the point that the tech is or rapidly will become reducible to repeatable engineering practices, to drive the next generation of power, propulsion, computing, and life support technologies.

tahanson43206 · 2025-01-05 15:09:17

For kbd512 re Post #194

Just FYI .... no reader of your post is going to have an idea to what "this" refers.

You are carrying on multiple conversations with multiple people on multiple subjects.

This is especially a problem when we are using your named topic because that literally has NO theme (by design)

***
Regarding your post in "Weapons" about where to base kinetic weapons....

Interesting analysis.

If you want to make a difference, you need to write something that gets read by decision makers.

Senator Cornyn is a possible candidate to receive your kinetic weapons idea. He is freed of the heavy burden of Senate leadership, so may have time to think about something else.

Regarding Taiwan .... Your answer was apparently written in haste.

We (the US) have a triad for defence for very good reasons.

Any defense installation on the island of Taiwan will be struck by a missile in the first wave of the assault.

If pods are floating off shore, then their exact location is not known at the moment of attack, so they represent a defense that is less likely to be taken out by the first wave.

It seems to me that your thinking is at a very high level, looking at entire theaters of potential conflict. The Taiwanese do not have that problem. Their situation is immediate and close at hand.

You're right that their defense is their problem.

My suggestion was to simply pass along an excellent idea to the people who are most in need of it.

(th)

kbd512 · 2025-01-05 18:31:59

tahanson43206,

Apologies. You asked about sCO2 gas turbines being usable on Venus. They are. sCO2 is a dual-use civil / military technology enabling the use of abundant fuels and synthetic natural gas or coal fuels, with greatly improved thermal efficiency. In actual practice, steam struggles to reach 35% thermal efficiency. I've seen claims as high as 50%, but I'm unaware of any actual steam turbine with that efficiency. In actual practice, after all losses are accounted for, sCO2 has demonstrated a real world 60% thermal efficiency. They are deliberately designed to operate at very high temperatures and pressures, making them ideal for applications where mass / volume is a factor, and high temperature resistance is a factor. SiC is nearly immune to Sulfuric acid at 1,200C. Very few other materials can make that claim.

sCO2 power plants are presently being deployed around the world in various oilfield pumping power and commercial electric power projects using advanced thermal cycles that both capture CO2 and repurpose as much waste heat as possible to drive the cycle. They're primarily powered by natural gas and coal, because that is what the world uses the most of for generating power. To my knowledge, the intent is to recapture the CO2 exhaust, store it as liquid CO2, and then turn it back into fuel using solar thermal power. I want to apply sCO2 tech to our military ships and aircraft because sCO2 is more thermally efficient than steam turbines and gas turbines, across a broader range of engine output levels than simple max output, which is where conventional gas turbines are most efficient. sCO2 equipment is lighter and more compact than both steam and gas turbine power plants, and potentially less costly since it requires so much less material. Beyond that, coal is the cheapest fuel, so if we can synthesize fresh coal from human waste products and collected CO2, then there's a great incentive to collect CO2 from the atmosphere and oceans or other sources. Right now we dump a large amount of raw sewage into the waterways and oceans. I would rather we collected the poo to make fresh coal.

CO2 recycling is vastly simpler and easier to achieve at human civilization scale than recycling of electronics materials. Everyone in the industry is finally having their "come to Jesus" moment regarding recycling of wind turbines, photovoltaics, and batteries. Electricity wasn't the miracle technology everyone had hoped for. The energy is renewable. The machines are not. Electricity is great to have as an option at a local scale where a major efficiency benefit for a specific task is on offer, but not remotely feasible to repower society with. It is not possible to consume less, or to burn less burnable materials, if the "new" energy generating and storage technologies are orders of magnitude less energy dense than what they fail to replace.

The Allam-Fetvedt cycle, in particular, uses 95% CO2 at very high pressure, a tiny percentage of O2 separated from the atmosphere, and coal or pure Carbon combusted with a small amount of pure Oxygen, as the heat source. The hot / high pressure CO2 in the combustor is used to trap heat, in order to regeneratively heat the sCO2 thermal power loop, so that less fuel has to be burned. We are building one of these pilot scale plants right now. It's a 270MWe power plant being built by 8 Rivers and Siemens Energy, and will use coal or CWS fuel in an Oxy-Fuel combustor. Nearly all of the heat is recycled and they've had no problems maintaining a flame in mostly CO2 atmosphere. It's based on a smaller 50MWth plant built in La Porte, TX, in 2018.

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

The Allam-Fetvedt Cycle is a recuperated, high-pressure, Brayton cycle employing a transcritical CO2 working fluid with an oxy-fuel combustion regime. This cycle begins by burning a gaseous fuel with oxygen and a hot, high-pressure, recycled supercritical CO2 working fluid in a combustor. The recycled CO2 stream serves the dual purpose of lowering the combustion flame temperature to a manageable level and diluting the combustion products such that the cycle working fluid is predominantly CO2. The pressure in the combustor can be as high as approximately 30 MPa. The combustion feedstock consists of approximately 95% recycled CO2 by mass.
...
In order for the system to achieve high thermal efficiency, a close temperature approach is needed on the high-temperature side of the primary heat exchanger. Due to the cooling process employed at the compression and pumping stage, a large energy imbalance would typically exist in the cycle between the cooling expander exhaust flow and the reheating CO2 recycle flow.
The Allam-Fetvedt Cycle corrects this imbalance through the incorporation of low-grade heat at the low-temperature end of the recuperative heat exchanger. Due to the low temperatures at the cool end of the cycle, this low-grade heat only needs to be in the range of 100 °C to 400 °C. A convenient source of this heat is the Air Separation Unit (ASU) required for the oxy-fuel combustion regime.
When burning natural gas as a fuel, this basic configuration has been modeled to achieve an efficiency up to 60% (LHV) as a power cycle net of all parasitic loads, including the energy-intensive ASU. Despite its novelty, the components required by this cycle are commercially available, with the exception of the combustion turbine package. The turbine relies on proven technologies and approaches used by existing gas and steam turbine design tools.

There is also a new process that uses superheated steam and Carbon from food waste or sewage, or collected CO2, in order to make fresh synthetic coal, in a matter of a few hours vs millions of years. The input energy source is solar thermal power. Coal-Water Slurry / CWS is a viable long term energy storage medium with the easy storabiity, energy density, and low flammability that other fuels lack. CWS auto-ignition temperature is some 600C higher than Hydrogen, Methane, Propane, gasoline, kerosene, and diesel. As liquid hydrocarbon fuels go, synthetic CWS is the most benign but energy-dense form of fuel we're likely to see, absent a breakthrough in fusion or anti-matter.

Everyone proposing the all-electronic society has already said that they don't want new nuclear reactors. Now that sCO2 and synthetic coal or natural gas can supply the power density of a reactor core when the Sun stops providing input power, as it does every single day, a long-term sustainable solution to our energy problems is at-hand. I would've been perfectly content with having abundant nuclear-generated electricity, because the waste stream generated is absolutely tiny, and its reliability / longevity in operation are unmatched. Unfortunately, our anti-humanist environmental crowd successfully lobbied Congress and the American people, against nuclear power, for longer than I've been alive. They deliberately soured public opinion on a very promising energy tech. To closely paraphrase Amory Lovins of the Sierra Club, "We weren't concerned with nuclear meltdowns, we actually liked that aspect of it, we were concerned with what humanity would do with all that cheap and abundant electrical power." Amory Lovins is a fake environmentalist and real anti-humanist. He "loves" the environment, but hates people. He's reiterated that statement over decades, so it's not an offhand comment he made when he was "young and dumb".

Since all that history with, and current public perception of, nuclear power cannot easily be "undone", now they're getting synthetic coal and natural gas from solar thermal and geothermal. If they don't like coal and natural gas, then they can use their own money, rather than public money, to prove that their all-electronic society is long-term sustainable. As the general public increasingly turns against and strips these charlatans of their unearned power and privilege, we will forge a new path without them. They were given a very generous 50 years of intellectual effort and endless funding, but produced nothing of lasting value.

Ultimately, children of the Baby Boomer generation viewed electricity as "magic". It's not magic and never has been. It's the most expensive way to generate and use power. It's a wildly inappropriate way to power everything in modern society. Those who should've known, who had every educational advantage afforded to them, somehow knew too little about the actual problem, which was how their vision of a future society clashed with material reality, and refused to perform basic sanity checks on their own work. Doing so would've ensured that what they thought was possible, had to be evaluated for workability. All of that was an afterthought for them, if they thought about it at all. Scant evidence exists that they did. There was lots of cheap talk from our policy makers about transforming society, but nobody asked what it was being transformed into. More than a few absurdly expensive bridges to nowhere were built. To what end? To make everyone poor again? We've been there already. Nothing worth having ever came from doing that.

Through it all, there was no real effort at ultimate sustainability, which should've been the policy and implementation aim all along, so nothing remotely practical was ever created as a substitute for coal / oil / natural gas. On top of that, no consent / buy-in was sought from the people paying for all of this. There was only accusation of "loving big oil" or "hating the environment" or "you're a climate denier" and similarly unhelpful discourse. Even if that was true, the people making those statements are universally "basic math deniers" when it comes to the feasibility of their proposed solutions. There was also plenty of outright dismissal of growing concerns that none of what we're doing is "green" or somehow "in keeping with nature". That movie Micahel Moore made, "Planet of the Humans", was a bright shining example of what was really going on, and is still going on to this day. The energy and materials requirements to make everything electric or electronic looked a lot like the "unsustainable growth curve" that our peak oil people warned everyone else about, albeit with a drastically more limited supply. For the "true believers" amongst this crowd of math illiterates, any solution to a problem that did not apply to their favored energy solutions was to be ignored. Unfortunately for everyone, simple but profound problems such as not having enough Copper on Earth to do what they wanted to do, could not be "ignored hard enough" to make any difference to energy and materials reality. That is the true reason for the apparent lack of progress. It has nothing to do with oil companies, people's perceptions of the environment or climate, or any other reason.

Addressing root causes is what sCO2 goes a long ways towards, ditto for all the other "generation beyond" technologies I mentioned. Power equipment of any significant output was enormous and cumbersome to both manufacture and deploy. Computers capable of human-like reasoning cannot be implemented through Silicon-based semiconductors in a practical way. Aircraft which are dramatically lighter, and therefore require far less energy, cannot be built at scale without CNT or BNNT or natural fiber composites and sCO2 gas turbines.

We've taken metals-based components about as far as we can take them. Only 3D printing / laser sintering of parts represents "generation beyond" technology.

Current battery gravimetric and volumetric energy density is no better than highly compressed air. Power density is much better, but not recharging times. Ultimate sustainability remains a giant question mark that ought to receive an answer, though I doubt it will. Every day I hear about some "revolutionary" new battery or photovoltaic tech. Few to none of these tech improvements will ever be deployed at-scale, because all of them have fatal flaws. I'm hopeful that we will see something better for solid state batteries, but once again, that tech is clearly most appropriate for powering mobile computing devices, not cars / trucks / trains / aircraft.

I guess I'm left hoping that those involved in industry have already "picked up" on what is working at-scale, and what is not.

tahanson43206 · 2025-01-05 21:09:55

For kbd512 re Post #196

First, thanks for #196 with additional detail about SCO2 and specific clarification about the Venus application.

And second, thanks for allocating some time to the discussion of this technology in the Google meeting this evening.

The key takeaway for me was your impression/belief that a fission reactor small enough to provide power in a Venus probe seems unlikely, if the fuel is not highly enriched Uranium. However, NASA qualifies as a federal agency trusted with such fuel.

Our proposal for a Venus probe is most likely to be sponsored/implemented by NASA, so the size of the reactor can be as small as is practical for an exploration vehicle intended to operate on Venus for decades.

I am interested in your SCO2 idea, and would be interested to know if you can make it work in the somewhat unique conditions at the surface on Venus.

I am NOT interested in the mining application you have in mind, because the funds for mining equipment will FOLLOW discovery, and the NASA probe we are working on can provide detailed studies of the surface of Venus over a 25 year system lifetime.

I AM interested in the buoyant vehicle (ala deep sea exploration on Earth) because it has the potential to "fly" anywhere on the planet, and hover over a specific location as long as necessary.

I'd like to see a design for a fully Venus qualified vehicle flow from the discussions on NewMars.

***
Thanks for your offer to help GW with his web site! I'm not sure what the full potential might be, but installation of a complete forum package is one way of accelerating the process. The feature we have in work for NewMars to serve files would be mighty handy for such a site on GW's domain.

We could store all his files in the directory structure, and serve them with links from the forum software.

The forum software offers search capability, so visitors to his site could quickly find things, and we could serve files from posts for the purpose.

(th)

kbd512 · 2025-01-06 04:00:55

tahanson43206,

I'll believe that NASA is serious about using fission reactors again the very first time they actually send one into space, irrespective of output level or suitability for some specific robotic exploration mission. Until then, they're spending a lot of money while producing nothing of tangible value to anyone, including NASA. I'm not an expert on any of this, but I've never seen or heard of a power source being used on a probe that's never once flown in space. KiloPower will either be flown and tested at least once, prior to use on an actual mission, or NASA isn't serious about using fission powered space probes.

KiloPower and the NTR being developed by BWXT were both redesigned to use HALEU as the fissile fuel after President Trump stated that weapons grade materials would not be used to power space missions. Using HALEU in KiloPower makes the reactor about 20% heavier than HEU. It's not catastrophic to the reactor mass, but clearly doesn't help. Using HALEU in the NTR, because the power level is so high and total operating time so brief, IIRC, represents only a 10% total mass increase. There may be some fast vs thermal spectrum mass reduction possible, but neutron leakage will be very high and the neutron and secondary gamma radiation shielding mass rapidly increase as a result. President Biden did nothing to reverse that policy, so far as I'm aware, and President Trump will take office again in a week or so. To wit, both the Russians and Chinese have also backed off on using weapons grade materials for space power and propulsion.

Argonne National Labs HALEU vs HEU Comparison for BWXT's "Draco" Nuclear Thermal Rocket Engine:
https://publications.anl.gov/anlpubs/2021/03/166537.pdf

Almost all of the mass increase, if you flip to Page 66, is driven by the fuel load and moderator. You need a mere 20.4kg more HALEU than HEU, but your moderator mass increases by 245kg. Due to a "quirk" of this application, the HALEU design actually makes slightly more thermal power than the HEU core, but only at the cost of increased mass, some 379.1kg in total. Reactor power is 540MWth for both designs, and Hydrogen flow rate is 13.6kg/s. If you're wondering why the mass delta is so small and reactor volume is virtually unchanged, when going from HEU to HALEU for a rocket engine application of nuclear power, it's because a NTR is a power-dense rather than energy-dense reactor design. For either fuel, the core is "cooked" (done done) after a matter of days of operation.

KiloPower, on the other hand, must be an energy-dense reactor design that lasts as long as possible. That is where the difference between HEU and less highly enriched fuels really starts to affect total core mass and volume.

Take thin film photovoltaics, for example. There was endless talk at NASA about using them in space, and many tens of millions were spent testing them on the ground. IIRC, JAXA is the only space agency to first test them in space for qualification, and then fly them aboard a space probe bound for Jupiter. The thin film was selected for that mission because they could be huge for very little weight, so they provided enough electrical power, even out at Jupiter, to power the probe in question. However, NASA spent crazy money developing thin film tech, and to this day we're using triple-junction polysilicon photovoltaics for almost every science mission, with a smattering of MMRTGs being the only notable use of nuclear power. Even the ASRGs which would've provided a lot more power from Plutonium-238, have ultimately been used for nothing and the many tens of millions spent on the ASRG development program produced nothing. NASA has a long and storied history of producing nothing when it comes to the use of nuclear power.

We now have a new nuclear tech development program that uses Cobalt-60 as the power source and it creates electricity directly from gamma rays, with output levels starting around 100kW. It greatly resembles a prototypical Lithium-ion "jelly roll". It does require gamma shielding, which is heavy, but at 100kW output, it's a fraction of the size of KiloPower. I can't recall everything I read, but I think the max practical-sized devices they're looking at are around 2MWe, which is still quite a lot of power. It's nowhere as energy-dense as a fission reactor, but it can still make 100kW for about 10 years at a drastically lower mass and volume than KiloPower. Since this is largely a commercial development, with only some NASA funding allocated, I would put more money on Cobalt-60 direct electrical power sources than small fission reactors. If BWXT actually flies Draco in space in 2027, or even a couple of years behind schedule, I would love to be proven wrong.

BWXT is or was working on a small modular reactor design as well (no idea if this has already been killed), named "Pele":
https://admin.sc.gov/sites/admin/files/ … udyR00.pdf

The only thing that makes BWXT more credible than most other companies is that they've delivered around 400 reactors to the US Navy. That's a gosh darn strong track record of actually delivering working nuclear reactor hardware. GE, Bechtel, General Atomics, Siemens, or someone else might be the prime contractor that stitches all the pieces together, but BWXT (Babcock and Wilcox) is the subcontractor that actually builds the reactor hardware. In my book, experience and track record count for something more than grand ambition. Even when Russia and China are added for comparison, there are vanishingly few government agencies or defense contractors who have built 400 working nuclear reactors for anyone, for any purpose. At any given time, there were only 450 commercial power reactors in operation across the entire world. For a singular company to have built 400 nuclear reactors is quite an accomplishment. I think it means they probably know what they're doing.

Anyway...

If I had components natively operable at 482C (photonic computers, Titanium / superalloys / SiC, and 100kWe Cobalt-60 power sources, I probably wouldn't concern myself with sCO2 gas turbines until my power requirements ranged between 10s and 100s of MW.

If I needed a non-nuclear / portable power source on the surface of Venus, it would be a partial Allam-Fetvedt cycle liquid metal turbine burning pure Carbon dust with pure O2, both of which would be extracted from the Venusian atmosphere and stored. No attempt would be made to recycle the CO2, but we would recycle the heat in the sCO2 generated during combustion. Carbon requires nothing more sophisticated than a metal tank to store it in, with CO2 providing pressurization equal to 93bar, so the tank doesn't need to be very heavy to withstand the pressures involved. However, something akin to a scuba cylinder would be required to natively withstand the pressure if the tank was emptied and not pressurized. Pure Carbon won't ignite at 482C. The auto-ignition temperature for pure Carbon and pure O2 is around 660C, and then it burns at temperatures up to 3,000C, making it a superlative heat source. Our heat exchangers would become tiny, especially with a 93bar CO2 atmosphere acting as our cold side heat sink. Only low velocity CO2 flow across the radiator is required for highly effective cooling. Supercritical CO2 inside the power transfer loop could be exchanged for molten Tin, which melts at 232C and boils at 2,602C, so Tin always remains in liquid phase at Venusian surface temperatures. To achieve the desired power density, the pressures required by supercritical CO2, Argon, or Xenon may become too great for practical operation. However, so long as we can keep reactive gases out of that power transfer loop, molten tin will enable absurdly high power density. Tin is about 7.25X denser than water- more than double the density of liquid Xenon. Not much velocity is required to produce gobs of torque at lower rpm. That should help with power turbine longevity. Silicon Carbide is known to be stable when exposed to Tin at extreme temperatures. Molten Tin is rather aggressive in attacking common metals alloys, but SiC and certain other refractory ceramics are virtually unaffected. We can go to at least 1,200C with SiC, but we may consider the use of UHTCs for even better power density.

Containment materials for liquid tin at 1350 °C as a heat transfer fluid for high temperature concentrated solar power

Pumping liquid tin at 1400°C

When it comes to SiC, the specific crystalline structure used matters to whether or not SiC is attacked by the Tin. Graphite, on the other hand, requires very little modification. Unfortunately, I think Graphite would be reactive with Sulfuric acid at the temperatures and pressures at the Venusian surface. That means the correct kind of SiC is required, or perhaps Graphite-coated coolant passages in a SiC heat exchanger?

Replacing a supercritical fluid with Tin would simplify the working fluid storage problem since a much larger volume of high pressure CO2 to "charge" the system is replaced with a liquid metal possessing a density comparable to Iron. That makes the power turbine and heat exchangers a very small part of the total power / propulsion system mass. A liquid metal cannot be compressed in a meaningful way, so no extreme pressure deltas are present inside the power transfer loop to complicate system design. No recompression turbine is required.

At 750bar and 427C, we can store ~326kg/m^3 of pure O2 in a ceramic matrix O2 tank, and then discharge that down to 93bar before refilling the O2 tank. I don't know what materials we should use to contain O2 at that temperature and pressure.

That's what I would use to provide conventional power to a large / heavy surface vehicle, or act as a conventional power storage system for a surface base.

Cleaving O2 from CO2 is a very energy intensive process, but this should be of interest to our readers:

Carbon dioxide splitting using an electro-thermochemical hybrid looping strategy

Wonder of wonders, this process was created for near-100% CO2 recycling back into O2 for long duration crewed space flight. I assume it could be used to manufacture pure Carbon and Oxygen to power vehicles, even though it was originally intended for closed-loop life support.

tahanson43206 · 2025-01-06 07:24:31

For kbd512 re #196

Thanks for this deep study! The choice of tin as the fluid, and carbon as the chemical fuel is surprising but it sure sounds plausible at first reading! The solution you've proposed appears (again at first reading) to enable any number of mobile devices to operate on Venus given a supply infrastructure. The infrastructure to supply that pure carbon and O2 is not part of #196.

Your discussion of nuclear fission alternatives seems to point to a large "mother ship" that makes fuel and oxidizer for all those mobile units.

(th)

tahanson43206 · 2025-01-06 11:23:00

For kbd512 re carbon particles as chemical fuel....

Your recent post about using pure carbon as a fuel on Venus might work on Earth...

Coal needs to stay in the ground, where it's been for millions of years.

Carbon, on the other hand, needs to come out of the atmosphere.

Until your innovative thinking occurred, every other human thinking about this has imagined a combination of carbon with hydrogen in one of their many configurations.

I'd like to (at least try to) encourage you to think about how your idea might be put into practice on Earth.

I'm assuming you are thinking of embedding the carbon molecules in a carrier of some kind. Water is a natural on Earth, and perhaps the native atmosphere on Venus would serve the same function there.

Is there an optimum ratio of water to carbon that would maximize performance of combustion engines working with this fuel?

Does it make sense to consider dispensing a carbon-water slurry from pumps?

Are there any downsides to this concept, such as clumping of carbon in a tank if water evaporates?

Update later: Methanol is comparatively simple molecule ( I understand ) that can be made from CO2 and water. Can the energy carrier capability of methanol be enhanced by suspending carbon molecules in the liquid? Has anyone experimented with this idea?

Update later: Apparently coal slurry transport in the Western US was seriously considered in a number of locations. The railroads appear to have won the legal fight. The idea was opposed by most environmental groups, but the use of precious water was a major block to the idea.

Note: Apparently in the example cited above, the coal slurry was to be dried out before it was burned.

(th)

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