kbd512 Postings

kbd512 · 2025-01-07 17:51:27

tahanson43206,

The most pragmatic use of nuclear power is as stationary power plants creating electricity or fuels and oxidizers to use aboard vehicles that, for all practical purposes, cannot be equipped with a suitably powerful nuclear reactor at any reasonable mass. Ships and trains can accommodate onboard nuclear reactors in a practical way. A mining truck can potentially be powered by its own nuclear reactor, but it's near the lower limit of a vehicle with sufficient size and mass to carry the weight of the reactor shielding.

Rocket engines used for in-space propulsion, that burn for a handful of hours, can use nuclear power in a practical way. Kirk Sorensen, Thorium advocate extraordinaire, explains in his Selenium Boondocks blog why using a nuclear rocket engine for leaving Earth is "not just wrong, but super wrong". Thrust-to-weight matters quite a lot, and chemical engines provide more of that than any competing alternative. The power provided by a liquid rocket engine suitable for a booster / first stage is measured in terms of gigawatts, even for a small rocket engine like Merlin. An off-road 4-wheel drive pickup truck is never going to be powered by an onboard fission reactor in a practical way. An aircraft needs to have the same mass as a WWII era frigate, and a wing area larger than the flight deck area of our largest super carriers, to use a nuclear reactor in a practical way. Anything short of that is diving deep into fantasy expectations of nuclear reactors.

I'm 100% in favor of developing nuclear power and propulsion for space applications, but I want to see someone fly their reactor design in space before I believe that NASA or anyone else is serious about doing it, and has shown real commitment to using the tech for what it's good for- namely, supplying megawatts of power to support exploration and colonization objectives. Furthermore, they need to demonstrate a coherent program of record that justifies why we're doing it. The justification is fairly obvious to me, but it needs to be put into writing and then into action. That is the sole reason I've been looking at all the potentially viable tech alternatives to nuclear power. I don't think any of these alternatives are objectively "better" than nuclear power, but if nobody is serious about pursuing nuclear power, then it's rather pointless to sit around fantasizing about what we could conceivably accomplish using nuclear technology that is not flight-rated hardware.

Closer to home, I'm 100% in favor of using nuclear reactors to provide the cleanest electricity we're ever going to get, but nobody is doing that in a serious way, either. Nuclear power was a CO2-free electricity source that was viable for large scale deployment back in the 1970s, but the people claiming they "love the environment / climate" are the very same people who prevented us from deploying civil nuclear power as a cleaner alternative to coal / oil / natural gas. I do not feel inclined to listen to the complaints of people who did their utmost to prevent the deployment of dramatically cleaner energy technology back when it would've mattered far more than it does now. A staggering amount of coal, oil, and gas has been burned since the 1970s because they were too ignorant / arrogant to accept what was clearly a better option than any other option of that era. Since they subsequently spent boatloads of public money on their non-working electronic energy fantasies, which they still pretend are working, despite all objective evidence to the contrary, I'm even less inclined to listen to what they want.

World Economic Forum Global Energy Usage in 2018:

World Economic Forum Global Energy Usage in 1973:

World Economic Forum Global Energy Usage, from 1973 to 2018:

The way I see it, if you want electricity and an "electronic future", then you should support nuclear power. If you don't want nuclear power, then support synthesis of coal and oil from collected CO2 or waste products and solar thermal power. I don't care which option is selected, but pick one and stick with it. Either option is economically viable. Unless there is nuclear power, there is no "beyond coal and oil", there is only "pretending we're not burning more coal and oil to use the green energy machines, while actually burning a lot more coal and oil". So-called "green energy" is anything but clean, and the only thing "green" about it is the color of the money squandered on it. It's only producing a world of poor people using the dirtiest energy options available, because they can't afford the latest techno-nonsense made from "clean green coal" burned in Asia. A global CO2 problem doesn't magically go away because you burned the coal in someone else's country, either.

Anyway, we can see why coal and oil consumption hasn't changed much since. Coal and natural gas should've been replaced by Uranium and Thorium if the all our "big thinkers" (more like, "futurism fetishists") were politely told to sit over in the corner and keep quiet while the grown-ups discussed how to best assure our future energy supply. Instead, we allowed the anti-humanist elements of academia to apply their insanity to a wider swath of humanity than they otherwise had access to. We have now stored, rather than reprocessed into fresh fuel, enough Uranium to power the entire US (100% of everything that uses energy- the homes, the cars, the ships, the trains, and the planes) for the next 100 to 300 years. That stuff is sitting around in spent fuel ponds across the entire US, doing nobody any good, over an ideological belief held by people who can't count. We're "so worried" about proliferation that we've left who knows how much Plutonium in every reactor in America, rather than spending the money to stick it back into a reactor to make more power. I think that qualifies as an epic level of stupidity to placate the doomsday elements within the Democrat Party who pretend to care about the environment when they really just hate people.

We can wait another century for a miracle to happen with these so-called "green energy" technologies, or we can make more pragmatic choices, which are going to be made anyway, regardless of what the people who grew up watching "The Jetsons" think about it. Personally, I would prefer that we use more nuclear power because it's the least environmentally destructive and has empirically led to the fewest directly-caused human deaths of all competing options. Anyone dead-set on acquiring nuclear weapons will find a way to do it, so that's not a real reason for blocking the use of nuclear power in industrialized countries. North Korea has already proven that, and nothing effective was ever done to stop them, so worrying about what might happen versus what did happen is a pointless endeavor. If we can make fusion or anti-matter work in a practical way, then we should start using more of that instead of fission.

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

Carbon is being pulled out of the ground at record rates because people need energy and that very attractive "nuclear option" was flatly rejected by the very same people who now claim to care about "climate change", so we're burning more coal than we ever have, because "green energy" didn't deliver. The nuclear reactors were shut down or blocked from being built by those green energy ideologues, who then resumed burning coal. In the absence of nuclear energy, which was the only practical option for CO2-free electricity, and by far the cleanest, coal / oil / natural gas is what we were left with to provide energy. Our "green energy" tech failed to come anywhere near meeting the increase in demand, never mind the total demand. I don't actually care about what the selected solution is, so long as it doesn't violate basic math when it comes to supply chain availability of resources.

Energy will forever be a basic math problem. You either have the quantities of materials and machines to provide it, or you don't, so then you get less desirable options as alternatives to meet demand. We should've pursued nuclear "right now", then wind and solar after we figured out how to make it work at a grand scale. We have wind and solar farms that can be seen from space. They provide no energy more than 50% of the time. There's no energy storage, either, so a good chunk of what it could provide gets dumped into the ground.

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

When we stop wasting money on nonsense that doesn't work, or paying off Democrat Party campaign donors with money that's supposed to fund "Climate Change Action", then we can do that. I'm 100% onboard with sourcing all of our Carbon from CO2 recaptured from the atmosphere and oceans. That ensures we never run out of coal / oil / natural gas. Photovoltaics and wind turbines are the wrong kinds of machines to recycle CO2. CO2 recycling tech has already been proven way more feasible than powering cities with photovoltaics or wind turbines. It kinda makes you wonder why pursuing CO2 recycling wasn't selected as the best option for us to spend capital on.

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.

There's nothing innovative about my thinking, merely more pragmatic than some others. Coal is Carbon and Hydrogen, but mostly Carbon, which is why it burns so hot (up to 3,000C when combusted with pure O2). I can all but guarantee that someone else thought of everything I've ever stated here, long before I ever thought of it.

tahanson43206 · 2025-01-07 18:46:07

For kbd512 re #201

Thanks for another comprehensive survey of chemistry of carbon and related subjects, along with historical examples and commentary.

I've created a topic that I hope you might be willing to develop a bit. I see this topic as similar to the Optical Plane topic, in that you've identified a potential opportunity that might be practical but also may NOT be practical.

The idea of burning pure carbon with pure oxygen looks to me like a very attractive option at Venus. No one has pursued it on Earth (as far as I can tell) simply because carbon is so conveniently packaged with hydrogen on Earth that there is no reason (other than curiosity) to try to use carbon by itself.

However, ** if ** there is a way to store carbon in a tank of some kind, and deliver it to a combustion chamber reliably, then it seems possible to me such a system might be competitive with carbon-hydrogen combinations.

We have at least one experienced chemist in the present active membership, so hopefully this new topic will attract other members.

***
I met a retired Senior Scientist chemist at lunch today. The last thing on this gent's mind right now is chemistry. However, while he was working he helped to design and implement a database for rapid/instantaneous lookup of hundreds of thousands of chemical reactions, and my guess is that number will have risen in the 10 years since he retired. I'll attempt to find out if this trove of data can be accessed by the public. I do know he's traveled all over the world to teach others how to use the system.

(th)

tahanson43206 · 2025-01-09 07:39:57

for kbd512...

HolyMoley(carbon) + HolyMoley(photons) >> HolyMoley(Squared)

I wonder if there might be an optimum ratio between CO2 and pure Carbon in the feed line that would reduce the unwanted behavior of pure carbon? Pure carbon by itself is (obviously) thirsty to bind with other atoms and it is not too choosy about who it favors.

Feed lines and storage tanks might be made of material that is resistant to carbon's grabby behavior.

On Earth Hydrogen tames Carbon via the hydrocarbon family tree, but on Venus Hydrogen is going to be hard to come by.

(th)

tahanson43206 · 2025-01-09 18:55:12

For kbd512 re sCO2...

If we decide to create a topic for sCO2, this link might be worth considering for a post:

https://www.energy.gov/sco2-power-cycles

(th)

tahanson43206 · 2025-01-11 17:32:35

For kbd512...

GW has provided a foundation block .... possibly a cornerstore .... for the counter rotating habitat ship topic.

http://newmars.com/forums/viewtopic.php … 28#p229028

I'm hoping to enlist your support for development of a set of detailed plans for an exploration vessel, including drawings supported by numbers.

I am not convinced by the 1 G argument, simply because we ** have ** to live at Mars G levels if we plan to settle Mars.

However, we can play with the RPM to achieve whatever G level seems to make sense to the personnel on the expedition.

GW has provided plenty of reasons to seriously consider the baton configuration for a small expedition.

We have so many topics in play right now, I'm not sure you have the bandwidth to spend much time on the counter rotating ship design. What I'm hoping you might be willing to consider is a leadership position (to be defined).

You provided a good example of that in your role as Webmaster. You set up the conditions for a project that took many months to complete, and you looked in from time to time, but for the most part you let the project team soldier on until the time came to put all that work into motion.

We might be able to do something similar with the Dual Counter Rotating Exploration ship concept.

This is decidedly different from your 500 passenger transport concept, but (as I think about it) the two vessels would have a lot in common.

The physical diameter of the vessel is fixed by physics, given a decision about RPM. The length of the vessel is entirely up to the project team. The ship can have as many bells and whistles as might be desired, or none at all, and the diameter will not change. The mass will certainly change as bells and whistles are added, but there is some minimal mass that is required to support the personnel in this vessel for a years long expedition.

GW has a commitment to finish projects he has already started, so if the rotating vessel topic is going to advance it will have to be without his participation.

(th)

tahanson43206 · 2025-01-21 21:45:36

For kbd512 re fiber habitats...
http://newmars.com/forums/viewtopic.php … 63#p229263

Thank you for this substantial contribution to the topic!

I'm coming away from my first reading thinking that creep may be a concern for duration of expeditions that employ inflatable habitats.

I'm wondering how to tell the condition of a habitat that might be placed in service. It seems possible that there might be a way to build sensors into the fabric itself, for example.

GW is talking (seriously as far as I can tell) about using these habitats for his deep space exploration vehicle for human transport.

My impression is that the Bigelow BEAM is the only working example that is in service. Is there any way to tell how well it is holding up?

You've recommended particular fabrics as best for particular purposes.

The systems in development by Sierra Space are having to pass NASA requirements testing. It would be interesting to see how their materials and fabrication choices compare to your recommendations.

Update a bit later: Anti-creep ???

I don't know the answer to this but hope you (kbd512 or other readers) will find the question at least interesting....

Concrete is routinely strengthened with metal elements. The advantage is that the strength of concrete in compression is combined with the strength of metal in tension. I bring this up in the context of fabric habitat structures.

In his recent post, kbd512 has identified creep of plastic fabric as a significant factor limiting service life. It occurred to me to wonder if a mixture of materials in the weave of an inflatable structure wall might help to overcome creep by (somehow?) shrinking while the plastic is relaxing.

(th)

kbd512 · 2025-01-22 02:23:45

tahanson43206,

"Fiber creep" refers to the phenomenon where a fiber, when placed under constant tension, gradually elongates over time due to a time-dependent deformation, essentially stretching slowly and irreversibly under sustained stress; this is a significant factor in materials like ropes, cables, and composite structures where fibers are under load for extended periods.

At the molecular level, creep occurs due to the movement of molecules within the fiber, allowing for gradual plastic deformation even at stresses below the material's yield strength.

It was also found that fibers fail under a constant load for a prolonged loading time and it is termed as creep failure. When a constant stress is applied to a fiber, deformation, so called creep strain, occurs with time. This creep strain eventually results in fracture.

https://www.samsonrope.com/docs/default … 12_web.pdf

My assumption is that this requires careful materials testing and design analysis to remain within design limits. The hoop stress in large pressurized structures can be quite high, even at fairly low pressures.

tahanson43206 · 2025-01-22 07:23:21

For kbd512 re #207

Thanks for more information on creep of carbon compounds that include hydrogen.

Please note that pure carbon (in the form of diamond) does not creep. It breaks clean, when it does break.

I'm looking for a way to (possibly) overcome creep in materials that are subject to it.

I don't know anything about "memory" metals other than that they exist. I wonder if something like that is possible in carbon based materials.

Single layer carbon structures exist ... Google reminded me of the name: graphene

Just tossing this out as a question... is graphene subject to creep? It has no hydrogen atoms so may be better able to resist deformation as described in the article you showed us.

(th)

kbd512 · 2025-01-22 11:30:11

Marlinespike Seamanship

tahanson43206 · 2025-01-24 21:54:51

For kbd512 re #209

Thank you for that glimpse of the knowledge that the US Navy tries to pass along to it's personnel!

I read much of it slowly, and scanned all of it. A number of knots (bends) are familiar from other input pathways, and it was nice to see that knowledge cast in the frame of life at sea in the modern age.

***
This post is about the worry of creep of materials made of carbon and hydrogen. By now I've forgotten where this insight came from so if you were the source you'll need to forgive the merge with prior inputs. That insight is that hydrogen is the component of a molecule with carbon that provides the flexibility that is so valuable in a line or a hauser, but it is that very same hydrogen that accounts for the creep that you've brought to our attention.

In this post, I would like to offer a suggestion / inquiry about a possible way of defeating creep in habitats made for deep space missions...

What I'm thinking about is the possibility of wrapping inflatable modules with thin metal bands that are welded together so that the weld is stronger than the material. If the metal were heated before it is wrapped and welded, and allowed to cool after the weld is sound, then the metal should contract around the habitat and remain strong and contracting even if (as) the habitat itself loosens.

What I'm wondering is whether the fabric would in fact stretch/creep at all, if the metal wrapping is constantly squeezing the fabric?

I don't know the answer, but sure hope the question is interesting.

***
We have another Sunday meeting coming up. We have a new possible focus for discussion, with PhotonByte's return with Version 2 of his deep well habitat idea.

From my perspective, the more I think about the idea, the more attractive it looks.

(th)

tahanson43206 · 2025-01-27 19:02:50

For kbd512 re photon collection...;

SpaceNut remembered a paper from 2008.

Here is a link to the paper:
https://www.lpi.usra.edu/meetings/leagi … ra4011.pdf

I'm not sure how well this matches up with your inquiry into the merge process, but the paper demonstrates dramatically the power that you would have available if you can get the capture process to work.

It appears to me that the researchers were feeding photons into the ends of the cable in the usual way, but the volume of traffic shows what is possible.

(th)

tahanson43206 · 2025-02-06 18:19:57

For kbd512 re aircraft ...

The article at the link below doesn't fit into any regular NewMars topic, but I think it may be of interest to you... it is about the challenges of maintaining the radar absorbing coating on F22 jets. The F35 gets a brief mention.

https://getpocket.com/explore/item/thes … ascinating

(th)

kbd512 · 2025-02-07 10:06:50

tahanson43206,

The "crumbling" skin is not the actual "skin", which is made from Carbon Fiber or ordinary Aluminum alloys, but rather, it's a radar absorbent coating material with poor environmental resistance. The newer materials have much better resilience to harsh environments, but they still typically require periodic reapplication / touch-up. The composite materials do not "defeat" radar, but they make the airframe much lighter than it otherwise would be. The shaping of the airframe redirects radiation away from the threat radar and its multi-layer coatings do attenuate radiation. The airframe shaping is responsible for its aerodynamic inefficiencies, but the F-22's lifting body design, large wing surface area, and all-moving tail surfaces maintain most of the kinematic performance of a fighter jet not hamstrung by the requirement to be stealthy as well as fast and highly maneuverable. Everything in engineering is a series of compromises. Beyond that, the structural design of the F-22 airframe was, at least from Lockheed-Martin's perspective, all about minimizing cost to the government. This point is emphasized again and again in the public documentation they've released. A lot of Titanium was used where Carbon Fiber would be a significantly lighter / stiffer / stronger option, but cost a lot more money to fabricate parts with repeatable mechanical properties. Every 4th wing spar was Titanium instead of Carbon Fiber.

Since the speed and performance requirements were reduced for the F-35, that jet makes use of even more CFRP with some Aluminum, at an even lower price point than the F-22. Beyond that, some of the "stealth coatings" were literally "baked into the skin" of those jets, and the durability of the surface coatings was improved, so they cost less to maintain. While the F-22 was completely optimized for nose-on radar stealth, the F-35 is actually "more sealthy" from every other aspect besides the nose, in comparison to the F-22. I don't think our allies understand what kind of a bargain they're getting with the F-35 design. It's less stealthy than the F-22, nose-on, but more stealthy in every other respect, it has much better IR stealth than the F-22, in addition to radar stealth, it can climb for altitude almost as well, it's highly maneuverable at AoA limits that would see a F-16 either "fall out of the sky" or otherwise lose directional control, it has more internal weapons carrying capability, greater range, lower engine cost since you only have to service one engine, and if they quit demanding so much bleed air from the engine, then the engine core would last a lot longer than it does.

The F-35 was involved in a 15 year development program that saw multiple daily flights, sometimes 4 or 5 hops per day. There was not a single F-35 crash during its entire development program. That is a spectacular and nearly unheard of achievement.

Nearly all of the extreme cost of both the F-22 and F-35 programs was directly attributable to the avionics, sensors, and weapons integration development. Yes, the stealth features cost extra. Yes, the advanced structural materials cost extra. The real cost is in electronics, particularly software now that they're entirely software-driven combat jets, and maintaining the jets once they're operational, but almost nobody seems to appreciate that this is where the true cost of aircraft development is now found. It would be fair to say that we spent an extreme amount of money on electronics and software, and then we attached those advanced computing systems to a stealthy plane that moves and maneuvers about as well as any non-stealthy 4th gen fighter. F-14, F-15, F-16, F/A-18, Rafale, Typhoon, and Indian Flanker pilots have all stated that they could not find F-35s outside of visual range, that their jets were only as-maneuverable as the F-35 with equal fuel loads (fuel equals "life" in a jet), but their better airframe efficiency gave them "longer legs" (more range) by using external fuel tanks that the F-35 was not saddled with. As far as pure speed is concerned, the 4th gen jets are only "faster" if you don't care about how fast your run out of "life", which is measured in mere minutes.

We completely optimized the F-22 for stealth, rather than maintenance hours expended per hour of flight operation. The end result was a hideously expensive touch labor intensive maintenance schedule and very few hours of flight time per jet per year, or compromised stealth characteristics. The F-35 used better materials and better geometry to maintain its stealth characteristics, with the end result that it's still more expensive than prior generations of combat jets, but is more affordable to maintain. Geometry plays a major role in directing radar energy away from the source emitter. Special radar energy dissipating materials are used where geometry alone is inadequate.

The F-35's stealthy characteristics also paid more attention to "total package" stealth features, to include minimization of IR / UV (more special coatings and the use of fuel as a heat sink), and acoustic (engine inlet and exhaust nozzle design) signatures, whereas the F-22 was primarily intended to provide radar stealth. This is far more important than most realize, because most new fighters, stealthy or otherwise, now include long range / sensitive EO/IR turrets slaved to their onboard radars.

Pure speed was de-emphasized in the F-35 design because no fighter jet spends much time above Mach 1 due to fuel burn rate. The F-35's powerful single engine still provides a stellar climb rate, which is the primary reason for having a powerful engine, but drag limits top speed. The single engine F-35 (A-18,250lbs, B-13,500lbs, C-19,750lbs of gas) carries internal fuel very comparable to the twin engine F-22 (18,000lbs of gas). Fuel is the limiting factor in most missions, not pure speed, not climb rate, not weapons load. In short, fuel is "life". Therefore, having a jet that can fly for at least 2 hours without refueling was seen as very important. 4th gen jets cannot fly more than 1 to 1.5 hours on internal fuel alone. On top of that, the size of the weapons bays were increased to allow internal / stealthy carriage of missiles and bombs that are larger than what the F-22 can carry.

During the 10 year long Viet Nam War, despite the use of thousands of high performance combat jets like the F-4 / F-8 / F-102 / F-105, which were capable of Mach 2 flight speeds, the highest speed flight speed actually achieved was Mach 1.2. The cumulative flight time spent at Mach 1.2 amounted to less than 15 minutes over 10 years of flight operations. I think there were 4 whole hours of cumulative flight operation between Mach 1 and Mach 1.1. If you can fly and fight for 10 years against an enemy air force equipped with Mach 2 capable MiG-21 fighters and Mach 3.5 capable SA-2 air defense missile systems, yet never spend more than 15 minutes at a very modest Mach 1.2, then what does Mach 2+ speed actually do for your fighter jet design when it's clear that nobody is using it, but making Mach 2+ speed a hard requirement greatly affects its maneuverability and empty weight?

Improved climb rate actually does do something useful for a fighter jet. Apart from greater top speed, improved climb rate is the other effect of greater engine power, and the only "feature" which is actually used in modern air combat. Whether we're talking about American, European, Russian, or Chinese fighter jets, climb rate does matter, whereas Mach 2 speed optimization does not, because at speeds above high subsonic, even if you have a 9g capable fighter jet, your turn radius is measured in miles above high subsonic speeds, and the cumulative amount of time you can spend above Mach 1, before consuming too much of your precious fuel supply, is measure in single digit minutes.

The only kind of radar stealth that combat jets are designed for at the present time, is X-band radar stealth. This is due to the fact that most fighter jet radars and virtually all missile radars intended to track and home in on small / maneuverable / stealthy targets, such as other fighter jets or missiles, use the X-band for its vital precision at the speeds involved, it's ability to reject or "see through" water vapor / ground clutter / chaff / jamming, and its transmit power and range with small antennas. X-band is a compromise between less precise longer wavelength radars that have difficulty with the precision requirement at the speeds involved and unnecessarily more precise higher frequency bands that have performance issues against water vapor / jamming / ground clutter and reduced detection ranges for a given transmit power.

That is the reason why you see other nations continuing to develop stealth aircraft, despite all the false claims that stealth is useless or can easily be defeated. If that was the case, then someone would've devised missile radar tech that can track and lock-up an enemy aircraft from similar distances as non-stealthy aircraft. Since that is clearly not the case, we see the continued development and employment of stealthy aircraft and cruise missiles. The shoot-down of that F-117 in Kosovo was a non-repeatable special circumstance event that involved multiple factors which permitted it to happen. The F-117s were following the exact same ingress / egress routes from their air base, the shot took place a very close range, it used a lower band radar that works a little better against stealth, the pilot had his weapons bay and gear doors open, and IIRC, may not even have been aware that a shot had been taken, because I think they lacked operative RWR equipment at the time. That's not a knock on stealth, it's a tacit acknowledgement that stealth works so well that you can only achieve a kill against a stealthy aircraft when you deliberately remove all those advantages you've afforded to yourself.

Stealth was/is "easily defeated" by WWII radar tech, if you believe the ignorant nonsense spouted off by people who know very little about radio technology. The problem is that you cannot launch a missile against an aircraft located somewhere within a 1 to 10 cubic mile block of airspace (the general level of precision that lower frequency band radars are capable of against all aircraft not optimized for stealth against UHF / VHF band radars), which represents the limit of precision / resolution of those much longer wavelengths, and still expect to hit anything. You'll know that the stealth aircraft is there, but if your missile is using an X-band active radar because no UHF / VHF band antenna can fit inside its nosecone, then you can easily spot the problem you're going to have with achieving a kill. Merely knowing that an enemy aircraft, stealthy or otherwise, is operating "somewhere over the rainbow", doesn't amount to air defense capability. That is the "general level of stupid" that the people asserting "stealth doesn't work" are operating on.

The people who think multiple lower band radars, operating multiple miles apart, can triangulate the position of a stealthy aircraft by communicating that info back and forth to increase the precision of the return info to the degree required to accurately guide missiles, through whatever means, seem to be discounting the difficulty associated with doing that. It's not impossible, but far from simple and easy, else someone would already have done it. The Russians have claimed to be able to do it, but none of their S-300 / S-400 missile batteries have had any luck intercepting Israeli F-35s. Recall that we've been working on this problem as well, because at some point in the future we also expect to be facing stealthy aircraft and cruise missiles.

The Chinese have invented (purely their invention, and derived from first principles, not something stolen through espionage, which is greatly impressive, at least to me, knowing something about the difficulty of their achievement) some highly innovative techniques for accomplishing this task, but the radar stations used to do it are truly enormous and timely processing of the signals requires super computer power. Such radar arrays would not be fitted to ships, for example, in a practical way. To wit, they are not connected to air defense missile batteries, but are instead used as early warning radars. I would opine that even if they could somehow be connected to missile batteries, there's a high probability that offboard radar guidance or IR terminal guidance is still required, using two-way data links back to the radar. For all intents and purposes, this is an impractically large and expensive solution, but it does appear to work.

When we're ultimately forced to confront China, we're going to face many of the same problems that they face, as it relates to missile and radar technology. Most of the "solution" to X-band radar stealth appears to involve using EO/IR systems to "see" incoming aircraft or missiles using their heat signatures, because that giant plume of hot gas from a turbojet or turbofan engine cannot be easily masked from existing sensors. The issue, of course, is that long range EO/IR detection and tracking systems are like looking through a soda straw. You can only "see" a very small patch of the sky at any given time, and thus they are not generally useful for scanning large volumes of airspace for detecting incoming aircraft and missiles in the same way that search radars are used. The solution appears to be to combine sensor inputs for target search and track functions by using lower band radars in conjunction with EO/IR systems that systematically search through a block of airspace after the radar has detected that a stealthy aircraft is located somewhere within a particular block.

GW Johnson · 2025-02-07 13:54:58

Excellent posting Kbd512. Thanks.

The basics of stealth and detection have not changed since I worked in aircraft countermeasures 4 decades ago. What has changed are the technologies for achieving stealth. And I agree, the focus has been on radar stealth, almost but not quite to the exclusion of IR and visual stealth.

The four prototype B-1A bombers were not all that stealthy, it being mostly in the shapes of the metal skins. The B-1B bombers had less nose-on radar signature, but were just as large or larger at about 45 degrees off the nose as the B-1A's. For penetrating dense air defenses at low altitude, the most common aspect at missile launch is nearer 45 degrees than nose on. Achieving lower nose-on signature cost them air craft performance, because they had to compromise the inlets to achieve it. So, I don't know why it was done that way.

The other B-1B problem persists to this very day. On that design low-altitude penetration of dense air defenses, there are 3 avionics systems that must all operate, or else you end up a smoking hole in the ground. One is the navigation system. Another is the threat warning and countermeasures system. The third is the robotic piloting that enables flying a large craft very close to the ground at transonic speed. USAF did the systems integration on this one, not Rockwell. And if you turn on all 3 systems, they interfere with each other and crash. 2 OK, 3 no. Avionics were 2/3 the price of the program, and they could not afford to tear it all out and start over, so it was never fixed. Which is why the B-1 fleet has never been used in penetrating dense air defenses at low altitude. They have to stay away from that mission like the plague.

The stealth skin technology used in the B-2 and F-117 are older, comprising only the carbon composite skins, without the fancy coatings used on metal-skinned aircraft. The older F-117 was designed before the radar boys knew how to compute the reflection patterns from curved panels. That's why it was faceted so weirdly. They only understood how to calculate the return from flat panels. The facets and the extreme wing sweep caused very serious aerodynamic deficiencies in handling. By the time the B-2 was being designed, they knew how to handle curved panels, so that aircraft only has to overcome the aerodynamic control risks of flying wings. The biggie is not to deep stall it, because if you do, there is no recovery. This has been known since the fatal crash of an XB-35 in the late 1940's that killed USAF test pilot Glen Edwards. That's who the base is named for.

The bare epoxy carbon-fabric materials turned out to have a stealth-loss vulnerability associated with salt getting into the pores in the material. Once contaminated, it's no longer stealthy, and it was not possible to clean those pores of that salt. This is why the B-2 was never flown out of Diego Garcia, while the B-52's and B-1's were. It is also really a big part of why the Navy A-12 replacement for the A-6 Intruders was cancelled (salt spray very common on carrier flight decks!). The other two reasons were cost, and past negative experience trying to land tailless aircraft on carrier decks with the F-7U Cutlass (whose nickname was "widowmaker").

I suspect there's ways around the contamination issue now. But I haven't worked in that business since the mid 1980's, so I do not really know.

GW

Last edited by GW Johnson (2025-02-07 16:17:40)

kbd512 · 2025-02-09 00:09:24

Given the extreme cost of these modern stealthy heavy fighters, which are in fact weight-equivalent and cost-equivalent to WWII era strategic bombers, I would opt to field manned microfighters for tasks that heavy fighters are unsuitable for. AI-enabled "loyal wingman" drone tech is interesting, and has great potential with another 20 years of development, but thus far its reliability is questionable at best. AI works great until it doesn't, and then it's as dumb as a box of rocks. We can't risk the outcome of a major war on tech that's still as apt to attack our own assets or uninvolved third parties when its programming fails. Absent a reasoning capacity on-par with a human pilot, it's not ready for our next war. If the Chinese use it before we do, then they'll only encounter the same limitations.

There are tasks that microfighters won't be able to handle, but if we're limited to using heavy fighters for nearly every conceivable mission, then there will never be enough combat capable jets to deploy at any given time. The useful combat drones we've developed are every bit as heavy and expensive as manned heavy fighters. These large drones frequently require more maintenance since there's no human pilot aboard who can "work around" any unresolved issues with the jet between flight and maintenance events. The smaller drones have not proven very useful thus far, apart from short range battlefield recon and dropping grenades or mortar shells on infantry and tanks. Anybody who thinks they're going to attack a destroyer or aircraft carrier using a bunch of quad-copters is delusional. I noticed that the Navy quietly stopped purchasing and deploying the MQ-8 Firescout combat drones (semi-autonomous helicopter drones based on the OH-58 Kiowa airframe), which were touted as a revolution in over-the-horizon targeting and attack for small ships that can't launch fixed wing aircraft, against other ships and submarines. They did nothing of the sort. The MQ-25A, which has proven more generally useful as a tanker drone, is every bit as large as the F/A-18s and F-35s its intended to refuel, and per-unit purchase price is on-par with the Super Hornet.

The "gap tasks" most vital to fulfill during near future air warfare scenarios include CAS and CAP screen near friendly ships and air bases, and ISR in contested environments. The silly nonsense spouted off about hypersonic missiles, prompt global strike, and whatnot is just that- a bunch of hideously expensive idiocy making assertions about CONOPS which sound eerily similar to ye olde "long-range missile duels will make dogfights a thing of the past". Obviously, that type of combat never materialized during the Cold War, because the tech to do it was still too immature. The proliferation of stealth tech more or less assures that it won't. About 50 years after air-to-air guided missile tech development began, a fighter had a reasonable chance (better than 50/50) of launching a missile at a target beyond visual range, and either downing the target or forcing it to evade / distract / decoy the missile to avoid being shot down.

Cold War CAS involved gun runs and firing rockets at targets, but modern CAS uses small high precision munitions on targets designated by ground forces. Said munitions are now highly reliable, about 80 years after development began during WWII. If you can make a gun run on a target without getting shot up or shot down, then you're operating in a benign environment where a Predator drone can perform the same mission for a lot less money than any jet. Peer level adversaries like Russia and China have radar-guided AAA and MANPADS to use against anyone who thinks they can get away with that. A good number of Ukrainian and Russian pilots could attest to the effectiveness of 1990s MANPADS against helicopters and low-flying jets if they were still alive.

Cold War CAP screen of air bases and ships involved heavy fighters (F-4, F-14, F-15, Tornado, MiG-25, MiG-29, Su-27, MiG-31) engaging incoming bombers or missiles at ranges beyond their ability to launch missiles at the defended target. These days, there are so many weapons arrayed against carrier battlegroups and air bases that there needs to be a numerically superior airborne defensive force forming a close defense zone around the carrier or airbase, perhaps 50 to 100 miles at most, to pop any aircraft / missiles / drones that manage to penetrate the long range radar and missile defenses, mostly because cruise missiles don't get detected at longer ranges because the total number of assets looking for them is so limited. All we presently have is an offensive strike force, limited in number and time consuming to maintain, manifestly unsuitable for providing 24/7 air cover. This microfighter force does not require extreme speeds or heavy weapons loads since it operates near the defended assets. It does require high availability, significant numbers, and sufficient endurance to remain on station for at least 3 hours.

If we're fighting air battles against incoming enemy heavy fighters, then we can overwhelm them with sheer numbers, by physically being in more places at the same time than they can deploy heavy fighters or heavy missile batteries to contend with. China has apparently run into the same problem with pilot retention as we have. Their competent jet pilots frequently leave the military to work for the airline services. China's annual manufacturing rate for F-22 (Chengdu J-20) / F-35 (Shenyang J-35) equivalents is no better than what the US manages. Their pilot training problems are significantly worse. At present, China only produces about 1/4 as many fast jet pilots per year. This could mean they're held to exacting standards, and thus better trained than our pilots are, or it could mean the quality of their candidates is lower so more of them wash out as a result.

The design characteristics for this microfighter would be as follows:
Airframe: T1100G tape-wound composite primary structure and skins to minimize weight
Anticipated Empty Weight: 6,000lbs
Max takeoff weight: 10,000lbs
Max level flight speed: 715mph (MiG-17 equivalent)
Cruise speed: 550mph (F-16 equivalent)
Climb rate: 41,000fpm (F-4 equivalent)
Roll rate: on-par with 720°/s (A-4 equivalent)
Turn radius: 1,100ft (F-86 equivalent)
Engine: Honeywell HTF-7700 (7,665lbf; 950lb/hr burn rate in cruise; powers Cessna Longitude biz jets)
Internal Fuel: 2,856lbs (420 gallons)
Armaments: up to 1,000lbs of stores
2X Stinger (self-defense)
and
4X Peregrine (CAP mission)
or
4X GBU-53/B Stormbreaker (SEAD mission)
or
8X AGM-176A Griffin (CAS mission; unpowered glide bomb version of Griffin)

Those are cost-reduced but highly effective armaments, all proven to work well through multiple wars, except for Peregrine, which is an AMRAAM derivative product. Peregrine uses miniaturized AMRAAM tech. StormBreaker and Griffin repurpose existing missile components taken from other weapons like Hellfire, Sidewinder, and JDAM. No development is required for the engine, sensors, or weapons used by this fighter concept, which is a good thing, because there's no time for that.

Mission Equipment:
Raytheon PhantomStrike AESA radar
Pave Penny laser targeting pod or similarly-sized EO/IR pod

Projected Cost Breakdown:
Airframe: ~$3M (complete airframe and avionics, not including engine or crew systems)
HTF-7700 Engine Cost: ~$3M (based on 2021 engine replacement cost of $2.8M)
PhantomStrike Cost: ~$500K (2024)
Ejection Seat and Aircrew Environmental Systems: ~$500K (seats are about $200K)

Cost is broadly based upon known XQ-58A procurement costs. If the 6,000lb MTOW XQ-58A costs ~$4M, then ~$7M (a different but more efficient commercial engine, same PhantomStrike radar, 67% MTOW increase), so a bit more than double the cost seems reasonable to me. PhantomStrike provides full APG-79 capabilities (Super Hornet uses APG-79) in a smaller package using miniaturized modern electronics. We're building a lower cost Viper / Super Hornet facsimile that carries 4 offensive air-to-air missiles based upon AMRAAM (same range, lower per-unit cost, modern modern electronics, half the length and weight of AMRAAM). In practical terms, the Super Hornet carries 4 AMRAAM, 2 Sidewinders for self-defense, and 3 external fuel tanks to feeds its big thirsty F414 engines. The 20mm cannon won't be used for intercepts because our pilots tried blasting the drones inbound to Israel after they ran out of missiles, but almost shot themselves down due to the blast and debris from the exploding kamikaze drones or cruise missiles that Iran and the Houthis fired at Israel.

I chose the Honeywell HTF-7700 engine for 3 reasons:

1. HTF-7700 provides sufficient dry / non-afterburning thrust, and doesn't have an afterburner. A 0.75:1 TWR at MTOW is sufficient for nearly all operational purposes, and provides the ability to remain aloft without refueling for about 3 hours vs 1 to 1.5 hours in a Super Hornet or F-35 not carrying external fuel tanks. The Honeywell F-125, a purpose built fighter engine, can provide 1:1 TWR at MTOW using burner, but it's not as fuel-efficient and dry thrust is much less than the HTF-7700. The HTF-7000 series engines can be developed to provide up to 10,000lbf of static thrust, without afterburner, if so desired. My opinion is that more thrust is far less helpful than efficient thrust and reliability. If equipped for a CAP mission, then my proposed microfighter has a 0.81 TWR vs 0.93 TWR for the Super Hornet using burner. It's TWR is still much higher than the Super Hornet, at 0.75:1 for the microfighter vs 0.55:1 for the Super Hornet, if both jets are limited to dry thrust to conserve fuel. No burner also equals no burner maintenance.

2. This engine has proven highly reliable in civil operation across multiple thousands of in-service engines, over 99.9% availability demonstrated thus far, with limited maintenance and low total cost of ownership. There is a still-growing pool of these engines in civil service, because when you follow the maintenance schedule having a problem with the engine is almost unheard of. That's what I want- an engine that's been completely sorted-out through many years of development and operational use.

3. We source nearly all of our aircraft engines from Pratt & Whitney or General Electric. Both of those companies do good work, but we need to spread the contracts around to retain at least 3 different suppliers. Honeywell products are known for their pricier options, but their products are generally high quality and every bit as reliable as Pratt or GE.

How can I be "reasonably sure" that I will achieve those empty weight and performance targets?

There are few absolutes in life, but this microfighter design proposal, at MTOW, has a better TWR than the English Electric Lightning at its MTOW. It's wing loading will be lower than that of modern fighters, on par with highly maneuverable jet trainers, and its airframe planform will be similar to the F-16, while using lighter composite materials almost exclusively. Since it doesn't need to be supersonic, we can use airfoils producing higher Cl values. The only design innovations I wish to incorporate are simplifications for mass manufacture and aeroelastic control surfaces that provide smoother airflow over deflected control surfaces such as flaps and slats. I'd wager we can obtain Rafale / EuroFighter maneuverability, very tight turn radii, and F-4 climb rates without anything too spectacular on the design front. We're giving up pure speed and load carrying capability to arrive at a more pragmatic short to medium range fighter design that can loiter at altitude for extended periods of time. That makes a microfighter more useful for close-in CAP for point target defense and CAS.

During the Cold War, the West developed the F-5 Tiger / A-4 Skyhawk / BAE Hawk / F-20 Tigershark, which were highly maneuverable short range multi-role aircraft that proved to be challenging BFM opponents for much faster and more powerful combat jets to successfully engage. If you were not a top notch pilot, you would still lose an engagement fighting what were superficially far less capable combat jets. The electronics capabilities of their era greatly limited their general utility. However, electronics rapidly evolved while we basically dropped the entire idea of fielding large numbers of these relatively low cost / high reliability combat jets.

We wound up with very limited numbers of high-end heavy fighters that were not available when and where needed, because they were too expensive and maintenance intensive. We're nearing the point where the sticker prices for a squadron of fighters or bombers represents a significant portion of a military force's total annual fuel or spare parts budget, which means more money is being spent purchasing the machines than operating them. You should figure that 25% of any budget is devoted to personnel. Another 50% should be operational costs, such as fuel and maintenance.

From the UK's £57B FY2024 defense budget, £42.75B should be personnel and operations. All the rest of the money, which is split between their Air Force, Army, Navy, and Marine Corps, amounts to £14.25B. All the ships, submarines, tanks, artillery pieces, combat jets, logistics support assets, etc, as well as any military tech research efforts, will consume the rest of that £14.25B figure. When individual combat jets cost £120M, or substantially more for the 6th Generation fighters and bombers in development, how many of those do you think the Air Force and Navy can afford to field before their excessive cost starts to become a problem on the operational side? All military services across the planet are already experiencing dramatic sortie generation rate reductions with stealthy 5th gen combat jets. As a pilot, you might get 150 to 200 flight hours per year, at most, flying something like the F-35. Prior generations were routinely achieving 250 to 400 flight hours per year, which is enough to maintain basic proficiency flying the jet as well as prosecuting a specific mission or target set (practicing the use of the aircraft as a useful military weapon). Simulators can help maintain basic airmanship skills, but they've not proven to be a like-kind substitute for actual flying experience.

The UK has 34 F-35Bs and 137 Typhoons in total, so fewer than 15 squadrons of multi-role heavy fighters in total, shared amongst all their services. During the Battle of Britain, 71 operational fighter squadrons that took part. Does that provide some indication of just how few and far between modern air power assets truly are? Seeing any kind of fast jet operating overhead is a rarity, because there are so few of them. There are fewer than 300 total rotary wing aircraft operated by the UK MoD. The UK ended WWII with approximately 12,000 aircraft of all types, or about 1,000 squadrons worth. We can argue that modern aircraft are more capable than WWII era aircraft, which is true, but we cannot argue that fewer than 1,000 aircraft in total can be in 12,000 different places at the same time, because they cannot.

Losses don't have to be too high for a substantial portion of your total air combat capability to be wiped out by enemy action. A successful kamikaze drone or missile attack against and airbase can be a catastrophic event. If you lost 1 squadron of Typhoons or Super Hornets in an attack, it would represent a non-recoverable loss over any meaningful timeframe during a war, as compared to losing 1 squadron of Spitfires or Mustangs, which could and did happen during WWII on specific days of the war, on singular missions.

We need a more pragmatic approach to combat jet design to help reverse this trend towards fewer and fewer combat machines capable of fewer and fewer flight hours per year. I think this microfighter design concept is a viable way to do that, enabled by electronics miniaturization required to provide similar capabilities to our modern heavy fighters, with limitations to combat loads and ranges being accepted as the compromise we're making to achieve affordability. This microfighter concept has a combat weight similar to a WWII fighter, despite incorporating vastly more advanced sensor and weapons tech, which means we can field enough of them to make a significant difference to the outcome of the next war.

I don't know if we're going to end up fighting Russia or China or both at the same time, but they seem dead-set on establishing global empires. Whatever the case, we all know what happened the last time two powerful nations were hellbent on doing that and thought their opponents incapable of effectively fighting back. WWII dragged on much longer than it should have, and more lives were squandered during and after that process, because we were unprepared for war. I would opine that the aftermath was nearly as bad as the war itself, even though it was famine / plague / politically-motivated purges in the East that caused much of the "after-kill" beyond WWII. If we make the same mistake twice, that's on us, not them.

tahanson43206 · 2025-02-10 12:27:27

For kbd512 re Steam vs Ion competition....

We have at least one electrical engineer in the membership, but that person is not currently active.

While I understand you are NOT an electrical engineer, your experience and education and deep reading may give you what it takes to head up the Ion Team until an Electrical Engineer shows up.

I have invited Calliban to take the lead of the Steam Team. Calliban's mission (should he accept it) is to see what amount of energy he would need to provide the maximum possible acceleration of a ton mass space vessel using a kilogram of water as the propellant.

Once we know what that amount of energy is, the Ion Team can use that energy amount to look for the best possible solution using Ion acceleration.

The competition is intended to be limited so that NewMars members can focus on a small part of the Universe of problems to be solved.

The ions to be accelerated are Hydrogen and Oxygen.
The mass of the space vessel is given as 1 metric ton.
The mass of the water propellant is given as 1 kilogram.

Energy for the Ion system will become available when (if) the Steam team completes it's work).

(th)

tahanson43206 · 2025-02-15 17:37:47

For kbd512 re work in topological optics topic...

25+ mm is a surprising diameter for a fiber cable.

I'm used to seeing or reading about hair's breadth diameters, so the difference is noticeable.

Ahead of Sunday's meeting, if you have time, and if the question is of interest...

If we assume a 100 meter strip of collection panel that is one centimeter wide, the maximum power it could collect would be some value near the Sun, and beyond the scope of the immediate inquiry.

Can you figure out what the maximum power that might be collected in Full Sun at LEO?

From that, can you figure out the diameter of a fiber cable to carry whatever the load is?

I'm wondering if the feed from the sides of the collection panel might be low enough so that optical fiber in use today might serve?

Is it possible you are working on the collection pipe, that would collect feeds from small fibers along the kilometer or more of the structure?

If that is a correct understanding, then two 90 degree bends would be required. The first would be from the optical collector in the 100 meter run to the optical fiber in that feed. The second would be from that feeder into the main trunk.

***
I'd like to see if we can work Calliban's steam balloon into the mix, if we have time.

(th)

kbd512 · 2025-02-16 01:27:11

tahanson43206,

If we assume a 100 meter strip of collection panel that is one centimeter wide, the maximum power it could collect would be some value near the Sun, and beyond the scope of the immediate inquiry.

The power radiated from the Sun is a function of distance from the source emitter.

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

Total solar irradiance (TSI) is a measure of the solar power over all wavelengths per unit area incident on the Earth's upper atmosphere. It is measured facing (pointing at / parallel to) the incoming sunlight (i.e. the flux through a surface perpendicular to the incoming sunlight; other angles would not be TSI and be reduced by the dot product). The solar constant is a conventional measure of mean TSI at a distance of one astronomical unit (AU).

TSI (Total Solar Irradiance) at ToA (Top-of-Atmosphere; where "space" ends and Earth's atmosphere begins), at 1AU (about 93 million miles, on average) distance, is about 1,361W/m^2.

100m * 0.01m = 1m^2

TSI over 1m^2 = 1,361W

Is it possible you are working on the collection pipe, that would collect feeds from small fibers along the kilometer or more of the structure?

Yes.

From that, can you figure out the diameter of a fiber cable to carry whatever the load is?

Yes, and I gave an example for transmitting 1kW of photonic power with long-term durability (years of operation) taken into account. When you see fantastically high power densities for fiber channel lasers, those are typically for very brief bursts of power and they also typically use active cooling systems to remove waste heat from the "light pipe" delivering the coherent photonic power to the emitter aperture. In contrast, a fiber optic cable delivering light over 1 to 100s of kilometers for communications systems is a strand or strands of uncooled Silica fiber wrapped in a chemical dopant used to reflect light back into the "core" of the fiber strand, plus a plastic sheath to protect the fiber from the elements while its buried in the ground, exposed to the atmosphere, subjected to some harsh chemical environment, etc. In this application, said fiber is more akin to telecommunications fiber optic cabling than it is to an actively cooled fiber channel laser fiber optic element.

TSI only tells you how much total photonic power is available to collect. Much like electrical power, a Wattage figure does not express how much power you can shove through a given volume of "conductor" without damaging said conductor.

A Silica-based "light pipe" (something to shove photons through), has a practical upper limit of about 2 Watts per square millimeter of "pipe surface area". That is, if the "pipe" available to shove photons through is 1 square millimeter in cross-sectional area, then you can shove about 2 Watts of photonic power through said pipe without damaging the pipe or degrading its ability to transmit photonic power. The same concept applies to electrical conductor wiring, and we have Ampacity ratings for electrical conductor wire gauges that are a function of their cross-sectional area, as well as surface area when it comes to AC power, related to what amount of current they can carry. We can manipulate Volts as well as Amps when it comes to electricity to manipulate the gauge of wiring used to carry a given amount of power, but eventually we run up against dielectric breakdown voltages where we have arcing and sparking across any medium, to include a hard vacuum.

Since this "light pipe" is in fact a solid material, made from a specific material (Silica, typically, although polymers are also used) with a specific density (2.2g/cm^3 or 2,200kg/m^3), when it comes time to transmit the collected or generated power to some other endpoint use, then we need to consider volume in addition to cross-sectional surface area in order to compute the mass of the material we're using to transmit the power back to our point of use. As you can imagine, the mass of this materials grows rather large rather quickly, for both Silica and Copper.

There are certain kinds of photonic power transmission "pipes" that have hollow cores, but those still rely upon total internal reflection to deliver the power, and also have their limits. Thus, we must remain mindful of power transmission mass, in addition to collector mass and surface area.

We can feasibly use different materials to collect and deliver the power with significantly lower masses. For example, PMMA plastics, but that material also has a much lower power density per square millimeter. Everything in engineering is a series of trade-offs.

tahanson43206 · 2025-02-27 21:32:27

For kbd512...

Thanks for the antimatter addition to the Any Propulsion topic!

Here is a link to a YouTube by the gent you cited:
https://www.youtube.com/watch?v=n2pWv-D84W0

I thought it might be better for you to add it to the post (if you want to) rather than me adding a post and covering your post.

(th)

tahanson43206 · 2025-03-01 07:37:25

For kbd512 re new topic in Projects category...\

Please take a look at the new Optical Plane topic.

Let's discuss the concept in the up coming Google Meeting.

The amount of power to be collected appears to be greater than I had thought by an order of magnitude.

I'm hoping you will be able to figure out how to use 2 MW of constant power to drive this vessel on a deep space mission.

Details of how to transmit thrust to a client vessel need to be worked out.

Extrapolations of how having power of this magnitude might influence space mission planning would be welcome additions to the forum archive.

Update: It would be interesting to know if any of the vendors of the optical collectors you found can make them small enough to fit into the ribs of the wings of the Optical Plane system. The limited factor for the system appears to be the amount of power that can flow along a single fiber.

I've been assuming one watt can flow along a "normal" optical fiber (whatever that is) but I don't know that, so will hope you have time to clarify it.

The longest run of a single fiber would be 1.1 km, for the furthest right and left most tips of the forward most rib.

I got an estimate of 100,990 kilometers for the total length of fiber needed for this application. However that first estimate may be low.

On a second try I got 19,999,000 km of line.

I'll put the calculation steps in the new project topic for Optical Plane.

(th)

tahanson43206 · 2025-03-02 21:54:50

For kbd512 re power available at stern of 1 km long platform:

I'm getting 2000 Megawatts.

What can you do with that?

It appears the problem of the 90 degree bend is solved, so let's move on to how you are planning to use the power to generate thrust?

(th)

kbd512 · 2025-03-03 10:54:05

tahanson43206,

You need about 40MWth of input power per kiloNewton of thrust generated at the same temperature and therefore Isp as a solid core nuclear thermal reactor, so 2GWth translates into about 50kN of thrust. This assumes the use of Hydrogen as the propellant. You can use higher mass propellants to generate more thrust, such as Methane or Ammonia or CO2, but pure Hydrogen will always provide the highest Isp, which is what we're after in this instance.

tahanson43206 · 2025-03-03 13:45:05

For kbd512 re thrust that might be achieved using 2000 Megawatts of solar power.

According to Google (using www.convertunits.com) a kilonewton is equivalent to .1 (1/10th) ton-force (rounding to nearest tenth)

The implication seems to be 5 tons of force generated while the Sun is shining and hydrogen is flowing.

Can you spec out how this system would stand up to service as a space tug?

A major potential service is to push ships toward the Moon.

A minor potential service is to push ships toward Mars, or decelerate them so they fall toward Venus.

5 tons may not amount to much, if the mass of the solar power collection system, and the hydrogen propellant are significant compared to the mass of the customer vessel. On the other hand, perhaps the rocket equation might show a scenario where this idea would work.

To start with, what flow rate of hydrogen is needed to generate that 5 tons?

My guess is that this is going to be an iterative process.

I wonder if GW's spreadsheets can be adapted for this scenario?

(th)

kbd512 · 2025-03-03 17:55:41

tahanson43206,

ṁ = F / (g * Isp)
ṁ (mdot) = mass flow rate, in kg/s
F = thrust (force), in Newtons
g = standard gravitational acceleration; 1g = 9.80665m/s^2
Isp = specific impulse, in seconds

The 40MWth figure corresponds to an Isp of about 1,000s, and I "baked-in" some anticipated losses into that figure.

ṁ = 50,000 / (9.80665 * 1,000)
ṁ = 50,000 / 9,806.65
ṁ = 5.0986kg/s

I hope that helps.

tahanson43206 · 2025-03-03 19:05:39

For kbd512 re #224

Thanks for clarifying the flow rate of hydrogen that would support thrust of 5 tons-force given 2000 MW of solar energy.

I'm sure it's just coincidence that the derived figure is 5 kg/s, but it makes it easier to remember.

Some weeks ago you were ready to start work on the engine design, but I was reluctant because at that time we had not ironed out the delivery mechanism. I am now satisfied the photon collection and delivery system is not only practical but could be built with existing photon collection traps and existing fiber.

If you are still interested in working on the engine design, please describe how all those photons will be directed to the task of heating that 5 kb/s of hydrogen to the energetic state needed. I assume the engine will need to be cooled just as combustion engines are now, because (it seems likely) the temperatures needed to produce the thrust would melt most metals (if not all).

Caveat: This may not be possible with today's technology.

This topic is available to show what is possible today and what is not practical with today's materials.

(th)

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#221 2025-03-02 21:54:50

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#222 2025-03-03 10:54:05

Re: kbd512 Postings

#223 2025-03-03 13:45:05

Re: kbd512 Postings

#224 2025-03-03 17:55:41

Re: kbd512 Postings

#225 2025-03-03 19:05:39

Re: kbd512 Postings

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