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#176 Re: Science, Technology, and Astronomy » Heat Shield Design Manufacture Application Maintenance » 2025-04-29 09:00:27
tahanson43206,
AVCOAT is NOT a structural material. It's density is about 33lbs/ft^3 and thickness of material to protect Orion ranges between 1 inch (2.75lbs/ft^2) to 2 inches (5.5lbs/ft^2) areal density. 5.5lbs/ft^2 is already above the typical wing loading of an ultra-light, and so falls outside the range which keeps peak heating values low enough for practical reuse. To structurally support the AVCOAT heat shield, you must have a stiff and strong metallic or composite backing structure, as was/is the case for all AVCOAT heat shields from Gemini to Orion.
If the AVCOAT material itself is 2 inches thick, then it's 26.85kg/m^2, so already well above an ultra-light-like wing loading of 18.3kg/m^2. The point is that you're already beyond ultra-light-like wing loading BEFORE any structural backing material is added, never mind payload mass. Unfortunately, 2 inches of AVCOAT is only sufficient for 1 reentry from interplanetary velocities (moon, Mars, Venus). If you go any thicker or heavier to plausibly achieve multiple reuses without extensive refurbishment, then you're well above your mass per unit area limit necessary to knock-down those peak heating temperatures so that AVCOAT's ablation rate remains tolerable. In short, you must have a TPS with a much lower areal density, preferably structural in nature as is the case with HIAD and ADEPT, so you get some usable payload mass per unit area.
Optimum stiffener arrangement of hot structure HIAD rigid nose. The areal density of the ablative TPS design was 8.53 kg/m2 and the area density for the hot structure design was 10.07 kg/m2. This corresponds to a 15% increase in areal weight for the hot structure design as compared to the ablative TPS design.
HIAD and ADEPT are structural TPS materials / designs that are UNDER the areal density limit for achieving ultra-light-like wing loadings of 18.3kg/m^2. Anything heavier and non-structural in nature is going to weigh more than that per unit area, and thus increase peak heating rates to the point where ablation becomes significant. HIAD and ADEPT designs have been modeled that could withstand an interplanetary aerobraking maneuver, swiftly followed by EDL before the hot structure cools and becomes structurally unsound. My prior post in this thread included a paper on this, from NASA, from the group working on reusable / lightweight / deployable reentry heat shield technologies.
The reusable AVCOAT heat shield design doubled-up the thickness to achieve that outcome, and then they scraped away the charred material from the heat shield (after the protected vehicle was back on Earth) to retain its aerodynamic qualities for a subsequent reentry. That's one form of reusability that comes at the cost of additional mass per unit area.
#177 Re: Science, Technology, and Astronomy » Heat Shield Design Manufacture Application Maintenance » 2025-04-28 22:48:52
HIAD-based heat shields on the left, ADEPT-based heat shields on the right:
Instrumented ADEPT demonstrator test article before firing:
ADEPT "Spiderweave" Carbon Fiber Fabric Heat Shield with RCC Nose Cap Testing at NASA's ArcJet Facility (3,000F temperatures):
ADEPT after firing:
Hypersonic Inflatable Aerodynamic Decelerator Earth-based Applications
LOFTID Mission 2022
Diameter: 6m
Nose Radius: 1.71m
Sphere-Cone Angle: 70 degrees
Entry Mass: 1,100kg
Ballistic Coefficient: 24.7kg/m^2
Planet-Relative Entry Velocity: 8km/s
Peak Heating Flux: 39.8W/cm^2
...
Aerocapture is a lucrative applications for HIADs due to the lower peak heat flux and peak deceleration environments compared to a direct entry. But considerations of the thermal protection systems must be taken into account if the maneuver is followed up by a direct entry trajectory. One potential risk is the TPS material turning into glass after being heated initially if the vehicle operates exo-atmospherically too long post-aerocapture. Additionally, the TPS has to be certified to be capable of tolerating the dual heat pulse of aerocapture and then direct entry.
...
High Ballistic Coefficient/Booster Recovery
One of the areas of commercial interest for the HIAD is to use the deployable to recover launch vehicle stages, specifically second stage or the engines. These missions will be suborbital in nature, as the second stage of a launch vehicle would not have attained enough energy to get into a low Earth orbit. However, due to the mass of the engines as well as constraints such as low deceleration and heat flux required to allow the engines to be reused, the design of the HAID recovery system can be challenging. This scenario was briefly studied by the prior HIAD applications paper, but the HIAD design after the success of the LOFTID system allows for additional flexibility in the trade space.Several different second stage recovery scenarios are considered here, include low energy scenarios such as low Earth orbit (LEO) launch vehicles with low or mid-energy trajectories, geosynchronous Earth orbit (GEO) launch vehicles with high-energy trajectories, and geosynchronous transfer orbit (GTO) launch vehicles with mid or high-energy trajectories. The launch vehicle trajectories in the paper have been generalized as much as been possible to not be reliant on any proprietary material, but applications for individual launch vehicle may vary due to the capability of that system.
In the document HIADs for entry mass of 17kg/m^2 to 200kg/m^2 are planned, mostly for aerocapture, but also for Mars EDL. A Venus EDL HIAD for surface probes is also planned.
NEXTEL fabrics used in certain HIADs are multi-functional fabrics useful for MMOD protection as well:
Heat-Cleaned Nextel in MMOD Shielding
#178 Re: Science, Technology, and Astronomy » Heat Shield Design Manufacture Application Maintenance » 2025-04-28 00:20:55
tahanson43206,
NASA has done extensive development work and flight testing on ADEPT and HIAD. Both are single-use deployable refractory fabric based (typically NEXTEL fibers) heat shield materials. Said materials are known to work and capable of withstanding pretty extreme peak heating scenarios one and only one time. They were never intended to be reused. They are much lighter, for a given thermal protection rating, than any PICA or AVCOAT foam ablator equivalent. As GW pointed out during our last meeting, the act of heating them up to such extreme temperatures turns them to dust as they cool and ablate away.
While the materials used are not particularly complex or expensive, relative to tiles (HRSI, TUFROC / ROCCI) or RCC, they are somewhat delicate, must be deploy (potentially after multiple months in space), and use rather sophisticated (complex and expensive) tether-based "warping" of the material to control reentry attitude by manipulating lift and mass CG shifting (they're effectively fabric lifting bodies).
All that said, this is the only flight-tested / proven materials and tech combination capable of achieving something close to ultra-light-like wing loading figures.
Unlike HIAD testing, which was almost 100% successful, to date ADEPT testing has proven rather abysmal. HIAD uses inflated fabric donuts (typically made of Nomex and elastic bladders) behind the thermally protective NEXTEL layers, which provides structural support to the very large diameter heat shield. ADEPT opens up like an umbrella, uses CFRP support rods / beams behind the thermally protective NEXEL layers, and typically also features a large RCC cap at the center of the heat shield / lifting body, where stagnation heating is most extreme. I believe the HIAD demonstrator flights used a PICA or AVCOAT cap, rather than a much more expensive piece of RCC.
These testing results are somewhat strange, considering the fact that HIAD is a more technically complex solution than ADEPT, due to the use of CO2 cartridges used to inflate the fabric donuts, the possibility of punctures or sealing failures, the requirement for multi-stage inflation, etc. Various structural or deployment failures were blamed for the repeated ADEPT demonstrator test flight failures. After the technological teething issues are ironed out, ADEPT is at least theoretically much simpler than HIAD to deploy and ought to be more durable. To my knowledge, ADEPT was intended to be used in conjunction with heavier payloads such as tuna can habitat modules landed on Mars, since ADEPT can more easily scale to larger sizes than HIAD.
Interestingly, the inflatable donut portion of the HIAD tech was intended to permit very large parachute deployment so no retro-propulsion is required to land on Mars. This development work has not yet been completed. I believe NASA calls these devices ballutes (balloon parachutes).
#179 Re: Martian Politics and Economy » Corporate Government » 2025-04-25 13:24:39
RobertDyck,
I agree that "real economy" should be based upon things of real tangible value so people don't do absurd things with money, but the US untethered the global economy from the global Gold and Silver supply because those two metals either had to have exorbitant prices if they were the only recognized stores of real wealth, or other stores of value had to be included in the representation of real wealth. For better or worse, we decided that all the goods and services in the "present and future economy" should represent real total value.
The mistake, at least from my perspective, of including "all the instruments of economy" (including future economic transactions before they took place) opened the door for speculators to manipulate the value of the materials, labor, and/or services by manipulating the represented value itself. Our government thought rational self-interest and existing regulatory controls (nobody actually practices laissez-faire economics) were sufficient. What rational government would deliberately devalue their own currency, keeping their people poor in the process? It turns out that the communist Chinese government did just that, in order to remain cost-competitive.
We could include various other metals, as you suggested, but at some point all the existing instruments of real economy must represent stores of real tangible value, else we're only recreating the problems associated with The Gold Standard. We ought not transact in terms of metal unless Martian society is dominated by the availability of metals. If such is the case, then yes, we should probably represent real tangible value in terms of various metals.
What valuation do you assign to new inventions that don't use metals as inputs, in terms of metals?
That was the fundamental reason for dropping The Gold Standard. After a certain point, using metals, even Iron, didn't make much sense.
Use your plastic greenhouse concept as an example. Presume it requires Martian-made plastics and sintered regolith to fabricate, but not much metal.
Real economy must somehow include food products made in greenhouses for the settlers, so how do we equate the value of said greenhouse, or the resultant food products, in terms of metals?
Whatever valuation we choose to assign to the greenhouse and the food, how will it be any more or less arbitrary than "all the instruments of economy"?
#180 Science, Technology, and Astronomy » Electrocaloric, Elastocaloric, and Magnetocaloric Materials » 2025-04-20 22:27:16
- kbd512
- Replies: 1
I'm creating this topic for discussion of said materials.
Traditional heating and cooling methods either involve circulation of phase change fluids like Ammonia or water or engineered hydrocarbons or chlorofluorocarbons between "hot" and "cold" plates, Joule-Thomson or pulse tube cryocoolers, heat pipes, etc. In modern times, we apparently have solid state heating and cooling systems that do not strictly require thermal transfer fluids, per se, that can leak into space if a collision with a piece of space debris creates a pinhole in the tubing carrying said fluid. This is not to assert that some or all of these new materials won't use a thermal transfer fluid in some stage of their thermal power dissipation loop, merely that one is not absolutely required.
Electrocaloric materials can transfer or move thermal energy using an applied electric field.
Elastocaloric materials move thermal energy by stretching and contracting shape-memory alloys such as Nickel-Titanium alloys or certain kinds of plastics or elastomers.
Magnetocaloric materials use magnetic or electro-magnetic fields to move thermal energy.
Although relatively new, there are in fact a limited number of commercialized examples of each of these technologies, primarily for HVAC or refrigeration. They offer energy savings advantages over traditional heat pump systems, so should be of great interest to those of us interested in space applications where input power / volume / weight are strictly limited, and ruthless efficiency is king. The temperature ranges some of these technologies are able to cover are still more limited than the various kinds of heat pumps we typically use, yet that may not matter much if an ideal application is found that will play to their strengths.
Generally speaking, we would use these technologies to collect and remove waste heat from our spacecraft or bases and then radiate the heat away into space.
#181 Re: Meta New Mars » kbd512 Postings » 2025-04-20 21:55:16
Blackbody Definition
A blackbody is a theoretical object that absorbs 100% of the radiation that hits it. Therefore it reflects no radiation and appears perfectly black. In practice no material has been found to absorb all incoming radiation, but carbon in its graphite form absorbs all but about 3%.
Stefan-Boltzmann Law
P = σAT4
P = Power (energy per unit of time)
σ = Stefan-Boltzmann constant (5.67 x 10^-8 W/m^2K^4)
A = surface area of the blackbody (in square meters)
T = temperature (in Kelvin)
A = 1m^2
T = 3,000K
P = (5.67 x 10^-8 W/m^2·K^4) * (1m^2) * (3,000K)^4
P = 0.0000000567 * 1 * 81,000,000,000,000
P = 4,592,700 Watts per square meter, or 459.27W/cm^2
40,000,000W = total collected input power available from the solar concentrating array for heating of the Hydrogen propellant
40,000,000W / 4,592,700W/m^2 = 8.709m^2 <- Maximum receiver surface area which can be heated to 3,000K by the solar concentrator array
For this Graphite heat pipe (more of a soda straw) to be 240m in length, it needs to be 11.54mm in diameter. On the bright side, it could be flexible enough to bend like a fishing rod for easy storage / transport to LEO. On the downside, coupling the power into something that small could present a bit of a challenge. However, I think I finally understand what you're trying to tell me about why it has to be built that way. It's related to getting the power out of the collector array and focused onto the receiver tube assembly, as I understand it. I'm not trying to argue, merely understand what you're telling me. If that's how it has to be built to keep the weight of the collector array in check, as well as the complexity and thus cost of the tech used, then so be it. I can envision some structural advantages to the 240m tube vs a much more compact receiver. After all, that gigantic solar concentrator array has to be connected to something.
The emissivity of Graphite is not equal to 1 (Graphite is not a perfect black body), so we would need to modify the equation used to arrive at the actual Watts of power input required to heat the receiver tube assembly to 3,000K. However, this places an upper limit on the surface area and volume.
What are we connecting the LH2 tanks to, so as to keep them well away from the receiver tube?
We seem to have a rather complex vehicle geometry to keep the imparted forces low and the structures light, but I'm trusting your judgement on this arrangement so as to ensure we remain within tolerable mass limits because you have more sophisticated tools at your disposal than I do, specifically the AI and OpenFOAM simulation tools.
#182 Re: Interplanetary transportation » Focused Solar Power Propulsion » 2025-04-20 19:16:37
Hollow-core fibers revolutionize green laser technology, by Qiang Fu, March 26th, 2024
Researchers made a significant breakthrough in laser and fiber technology, which showcases the potential for the long-distance fiber delivery of high-power green laser pulses via hollow-core fibers (HCFs), a revolutionary new type of optical fiber.
Efficient and flexible light delivery has been dominated by solid-core silica glass optical fibers, especially in telecommunications and industrial lasers. But high-power laser light delivery, vital for industrial applications, faces significant challenges with traditional fibers due to nonlinear processes like the Kerr effect and stimulated Raman scattering in the core, along with the damage threshold of silica glass. These factors greatly limit the deliverable power densities.
In hollow-core fibers (HCFs), >99.99% of the guided light is contained within the central air (or vacuum) filled core, bypassing the limitations of solid-silica core or traditional fibers. In 2022, the Southampton team successfully demonstrated the advantages of a new HCF design, transmitting 1 kW of continuous-wave near-infrared light (~1 μm) through a 1-km length, showcasing the technology's potential.
In the latest work, the team has expanded these capabilities into the green wavelength, crucial for numerous industrial applications, by transmitting kilowatt-peak power 520-nm laser pulses through 300 m of HCF.
Developing HCFs for visible wavelengths presents fabrication challenges due to the small structural features.
The team also conducted a comprehensive nonlinearity study on practical air-filled, long-length HCFs. Nonlinearity in HCFs in the visible relative to the infrared region is significantly higher, which is attributed not only to the reduced fiber core size but also to the shorter operation wavelength. This advancement is a crucial step towards using green laser light in high-precision, efficient material processing, which will benefit sectors like e-mobility manufacturing, notably in battery production.
Hollow-core fiber for green laser power delivery
The HCF used in this work guides light via anti-resonance, in which a series of thin-glass membranes surround the fiber’s core and confine the guided light within it. This is achieved via a single ring of seven cladding capillaries (seven represents an excellent balance between loss, bend-loss, and modality).
The fiber is fabricated by the stack-and-draw method using Heraeus F300 fused silica glass, and has a ~20.7-μm core diameter, a mode-field diameter of ~14.5 μm, and guides light from 515 nm to 618 nm with <30 dB/km loss (see Fig. 1). The reported fiber is 300 m long, but the team in Southampton regularly produces multi-kilometer lengths via this process. The fiber is also relatively bend-loss insensitive, with <0.1 dB/m loss for bends with diameters >13 cm at the operation wavelength of 520 nm.
Power delivery results
The power delivery experiments reported use an in-house-made 15.5-W, 520-nm, frequency-doubled ytterbium-doped fiber laser, producing 1.6 MHz repetition rate, ~520 ps pulses with ~18 kW peak power. The laser beam is focused to a 15-µm mode-field diameter to match the fibers, and results in a coupling efficiency of ~86%. HCF lengths of 2, 100, and 300 m were able to deliver average powers of 13.2, 6.7, and 3 W, corresponding to peak powers of 15.9, 8, and 3.6 kW, respectively (see Fig. 2).
The emergence of lower-loss and visible-guiding HCFs, now becoming available, is expected to enhance throughput efficiency and enable power delivery over kilometer-scale distances. Despite the energy density inside the fiber’s core reaching 5.5 J/cm2, no damage was observed in the fiber. The delivered beam quality, essential for precision micromachining and long-distance applications, was high across all the tested lengths (M2 <1.1).
Overcoming nonlinear limits of solid-core silica fiber
The nonlinear limit of solid-core silica fiber is a particular challenge in the visible due to the decreased core size (necessary for single-mode operation) and causes significant spectral broadening. When compared to a 15-m long, 10-µm-core photonic-crystal fiber (PCF), with similar loss to the HCF used (and measured using the same setup), significantly more spectral broadening was observed than for the 300-m length of HCF (see Fig. 3), clearly demonstrating the advantage these HCFs possess in terms of nonlinearity.
This work again shows that HCFs are ideally placed to solve issues encountered with the flexible optical fiber delivery of laser light and offer the possibility for large-scale delivery of laser light (especially in the green/UV-visible) for industrial processes. This flexibility is seen as vital for various future manufacturing concepts.
Expert commentary
Richard Carter, associate professor at the Institute of Photonics and Quantum Sciences, Heriot-Watt University, and academic lead at the Precision Laser Application Labs of the National Robotarium, as well as vice president of the Association of Industrial Laser Users (AILU), notes:
"Flexible delivery of ultrashort laser pulses (USP) would break a significant barrier in the adoption of USP manufacturing processes in industry. These forms of anti-resonant hollow-core fiber have been seen as one of the most promising options for several years, but issues in drawing reliable lengths of fiber have made this slow to practically realize.
The results highlighted from Southampton University represent a significant leap forward. Not only are the fibers able to guide in the more challenging green region but crucially with lengths and performances that are clearly ready for commercialization and industrial implementation."
FURTHER READING
Q. Fu et al., Laser Photon. Rev., 2201027 (Jan. 2024); doi:10.1002/lpor.202201027.
#183 Re: Meta New Mars » Housekeeping » 2025-04-20 17:59:08
tahanson43206,
I feel like I need to delete the cache and have the web server rebuild it, but I want to confirm that first.
#184 Re: Meta New Mars » Housekeeping » 2025-04-20 17:53:07
tahanson43206,
I have in fact changed the announcement message on the back-end to the text you asked for. I feel like there's some kind of reload step we may need to execute, though.
#185 Re: Not So Free Chat » Politics » 2025-04-17 01:25:09
RobertDyck,
I said I prefer the Canadian system, but don't see how to do that on Mars. Because Mars will have zero tax, I don't see how to pay for a healthcare system.
If you think I prefer our system, then you're equally wrong, but here's a thought. You are going to have taxes and you are going to have a purely public health care system (medical, dental, and vision), because there aren't enough medical staff or a large enough pot of money for any other options. Much like everything else in remote parts of the world, you're going to pay through the nose. Since every person on Mars needs to be productive, or there was never a good reason to send them there, you are going to provide full health care, period, or you won't have a functional colony.
A sanctioned ship is not allowed in any port that complies with America's sanctions.
China and India will happily do business with Russia. We can't do anything effective to prevent them from doing business amongst themselves.
Sanctions are starting to have effect; don't back down. The Russian economy will collapse late this year as long as sanctions are not lifted.
Iran has been under fairly draconian US sanctions since 1979. I'm sure their economy, which has far fewer natural resources and people than Russia, will collapse any day now. We've definitely made life miserable for the average Iranian, but most of them hate America about as much as they hate their own government. One thing's for sure, though, we're still at odds with each other over pretty much everything we care about.
The solution is to ensure Russia doesn't get to keep any Ukrainian land.
If most the fighting age Ukrainians are killed before you and Zelensky are forced to accept that Ukraine simply does not have the manpower to win a land war against Russia, I doubt very much that will be any consolation to the war's victims.
Providing Ukraine with weapons is cheap compared to American engaging directly in war with Russia.
The US and EU have spent $287B thus far to aid Ukraine, and borrowed even more money to do it. Spending another $287B is unlikely to achieve the desired effect, but our people will definitely be $574B poorer. Collectively, we've already sent as many ATGMs as Russia has tanks, including those it had in storage. The problem is that each one of those weapons cost about as much as a Russian tank, and Russia has been making new tanks about as fast as we can make missiles to destroy them.
Do you recall how historians stated that the defeat of Japan and Germany was inevitable because they couldn't keep pace with Allied war materiel production?
We're running into that same problem. To reverse that disturbing trend, we'd need to use our military to invade and start destroying their factories.
Just accept the offer, sell weapons.
So you can turn around and accuse America of war profiteering or war-mongering?
Hard pass.
You want separate countries, each with a military. But history shows us that results in war. Always.
Your own read of history indicated that we were fighting each other before nations existed. Heck, we fight each other within our own nations from time to time. Even when there's no functional government to speak of, you still have wars. Why are you unable to accept that violence is part of the human condition? Please tell me you don't actually believe you're the very first person who ever thought that if we did X vs Y, we'd have world peace.
Trump is doing many things wrong. His tariffs do not work they way he claims. But those tariffs are causing economic harm to my country.
Imagine how ordinary working class Americans feel about the results of NAFTA and the tariffs imposed on the products America attempts to export. We're eating a trillion dollar trade imbalance every year now.
The US has long claimed to be the leader of the free world, but the rest of us in the free world are watching as the US falls into dictatorship.
You do realize that was American propaganda, don't you?
What we're seeing with Trump is the transition from democracy to the dictator.
What you're seeing is the transition from a President who cares more about what other nations think about how America is run, to a nation where the President cares more about what Americans think about how America is run.
US DoJ Documentation on Kilmer Abrego Garcia
From the document:
On March 28, 2019, the Prince Georges county Police Gang Unit made contact with two suspected illegal aliens whom they had validated as an active MS13 gang members. ICE ERO officers [redacted] and [redacted] responded to 5600 Rhode Island Ave., Hyattsville, MD 20783.
Upon arrival, [redacted] met with Task Force Officer Detective [redacted] and he stated, that a subject later identified as Abrego-Garcia, Kilmer Armando (A# 201 577 119 (DOB : 07/26/1995) and Dominguez, Jose Guillermo (A (DOB [redacted] was detained in connection to a murder investigation. [redacted] and W. Allen then approached the subjects identified themselves as Immigration and Custom Enforcement Officer and questioned the subject as to their citizenships.
The subjects freely admitted being citizens and national of El Salvador by birth and that they were present in the United States illegally. The subjects were not in possession of any immigration documents that would allow them to be in or remain in the united States legally.
At approximately 1930, the subjects were arrested and transported to the Howard County Detention center for overnight placement . On March 29, 2019, the subject was transported to the Baltimore Field Office for processing without incident.
Abrego-Garcia is a citizen and national of EL Salvador. Abrego-Garcia claimed to have walked across the desert for many days entering illegally into the United States near McAllen, Texas on or about March 25, 2012.
The person that the Supreme Court ordered to not be deported from the US, and now demands be returned, was a legal citizen of the US.
SCOTUS demands return of an illegal alien who freely admitted to the arresting officers that he entered America illegally.
He entered the US as a refugee, got his Green Card, married an American woman, had a baby born in the US.
He's not a refuge. He's a criminal gang member. If a Green Card was obtained under false pretenses, that means nothing. The American woman he married took out a restraining order against him for assault and battery, which included her being punched by the man, her shirt ripped off, and bruised.
The gang in question is in New York, but the individial in question has never been to New York state in his life. He is not a member of that gang. That's why courts exist: when false accusations are made, the courts can free the innocent. And that's why the Supreme Court ordered this man to not be deported.
MS-13 operates in just about every state now, so far as I'm aware, and that includes New York. There probably aren't many of them in Alaska or Hawaii, but that's about it.
He is a MS-13 gang member with the tattoos and regalia to prove it. He was identified by another MS-13 gang member and was arrested with other MS-13 gang members during the course of a murder investigation.
Why are you defending an illegal alien MS-13 gang member who beat the piss out of his American wife?
#186 Re: Martian Politics and Economy » Corporate Government » 2025-04-16 23:10:54
RobertDyck,
Let's start with something more fundamental. There are no native born Martians. The only nations I'm aware of with the potential ability to send people beyond LEO, some time during the next 20 years or so, are America and China. As near as I can tell, nobody else even thinks it's worth doing and has no serious funding devoted to sending humans to Mars. If the people from either nation refuse to relinquish their status as American or Chinese citizens, then they fall under the jurisdiction of whichever nation provided all the funding to send them there in the first place. It's not as if they're entirely independent actors with zero ties to Earth. That is the reality-based starting point.
So as to convince these people who decide to live on Mars that they should form their own government, separate and apart from whichever government sent them from Earth, what do you do to convince an overwhelming majority of them to renounce their citizenship and form a new government?
Presuming the effort to convince a majority of the people already living on Mars to form their own government was broadly successful and no violence results from that course of action, what particular net benefit is there to those two nations, which were previously sending their people and cargo from Earth, that convinces them to continue sending more people and cargo?
If the Mars colonization endeavor is consuming people and money which could be devoted to other productive uses, without the promise of an eventual return on investment, why would they continue funneling people and money into Mars colonization?
Even if they don't lift a finger to stop you, they don't need to lift a finger to help you, either.
What negotiating tactics or economic offers will be used to entice those host nations to continue their support?
This is where declarative reality fails, so tell the rest of us how you plan to convince them to do that, because it sounds like you're planning a "mostly peaceful insurrection".
For all of human history, the success or failure of colonization efforts has been determined by two forms of capital, monetary and human labor. You need both.
Annual Space Program Spending by Agency
NASA: $25B to $33.7B (2025)
CNSA: $14.2B
ROSCOSMOS: $11.4B
ESA: $8.7B
ISRO: $1.6B
JAXA: $1.5B
CSA: $0.9B
There seems to be quite a monetary disparity there. One nation is clearly doing the heavy lifting, and it's definitely not Canada, so I would think if Canada is the world power they claim to be, there'd be something approaching a real space program, but your national leadership, regardless of party, doesn't seem too interested. Thus far, there has only been one nation that's ever sent anyone beyond LEO, but the Apollo program ended 50 years ago. In terms of today's money, the Apollo Program cost about $280B. SpaceX has improved the cost per mission metric by leaps and bounds, but any serious colonization effort is going to require money coming out the wazoo and a stream of volunteers, because most of them will wash out of training or decide to pursue other options.
#187 Re: Exploration to Settlement Creation » Habitat Design on Mars » 2025-04-16 16:49:02
If the bricks are fired in a kiln, perhaps at a lower temperature if combined with Sulfur, will that increase their strength?
#188 Re: Martian Politics and Economy » Corporate Government » 2025-04-16 14:29:23
RobertDyck,
This is getting frustrating. kbd512 demands Mars be a copy of the US
Since kbd512 never said that the Mars government should or would be a copy of the US government, anywhere in this entire thread, imagine his frustration over having words imputed to him that he never wrote.
People do expect Mars to be a place to escape government, to escape the "Karens".
If I understand this correctly, a corporatist government, which would be the dictionary definition of fascism, is going to "save us from the Karens".
How?
Before our leftists overran academia and redefined what fascism meant to "far right dictatorship", fascism was traditionally and colloquially the collusion between government and corporations to wield absolute power. This was great for the absolutists, but fairly terrible for everyone, given what that inevitably leads to... W A R.
Now it's more of a footnote about how control was established over the economy by the fascist regime:
Corporatist economic system
The fascist regime created a corporatist economic system in 1925 with creation of the Palazzo Vidoni Pact, in which the Italian employers' association Confindustria and fascist trade unions agreed to recognize each other as the sole representatives of Italy's employers and employees, excluding non-fascist trade unions. The Fascist regime first created a Ministry of Corporations that organized the Italian economy into 22 sectoral corporations, banned workers' strikes and lock-outs and in 1927 created the Charter of Labour, which established workers' rights and duties and created labour tribunals to arbitrate employer-employee disputes. In practice, the sectoral corporations exercised little independence and were largely controlled by the regime, and the employee organizations were rarely led by employees themselves, but instead by appointed Fascist party members.
...
Fascist governments typically established close connections between big business and the state, and business was expected to serve the interests of the government.
If we deliberately combine corporatism with government, then we get dictionary definition fascism, assuming you have a dictionary that was written before leftists hijacked western academia so they could redefine the essential differences between their precious communism and fascism. In actual practice, you either had a deliberate merger between business and government (fascism) or a hostile takeover (communism). That was one of the very few ways in which national socialists materially differed from garden variety socialists / communists. In one case, the government wasn't opposed to corporations so long as the company spouted off the party line. In the other, the government violently replaced the heads of all corporations with their own party officials. I have no idea which was meaningfully worse, but both sure as hell killed a lot of people.
If you're like me, then you're wondering what overwhelming benefits we're going to get from an intentional merger of both systems of governance, given the propensity of both systems to treat their people rather poorly if they think they can get away with it.
He wants war because he served as an enlisted crewman on an American Nimitz class aircraft carrier, and is proud of it. I have more respect for members of the US military who served in ballistic missile silos in North Dakota. I've met a few. They're mild mannered, peaceful people who hate war. I'm sure they were chosen for that job because of their temperament. But war is bad. War is nothing but mass murder for the purpose of armed robbery.
You really like gaslighting people, but again, this kind of false premise personal attack only proves to me that you're unwilling to consider why it is that people have differences of opinion with you.
As long as anyone is arguing in favour of war, then I have no respect for that person. I could be more rude if necessary.
Nobody here is arguing in favor of war. We have a difference of opinion about how to best prevent wars. You seem to think we can come up with a system that ignores past human behavior. I'm telling you that as long as humans are involved, the results will be similar to whatever they were in the past, from a similar style of governance. The "evidence" for that is all of human history.
If you're outright telling me that you're being deliberately rude and disrespectful to another member of this forum, then I would ask you to stop. I still have respect for you as a person, and your opinions, even if I disagree with some of them, and would hope you would grant the same courtesy to others. If you cannot, then we're going to have to go our separate ways.
#189 Re: Meta New Mars » kbd512 Postings » 2025-04-16 04:32:05
tahanson43206,
Graphite heat exchanger tubing and shells are available in a very wide variety of sizes and shapes, because it's a sintered and then hot-pressed material formed using molds or 3D printing. I don't know think there are any Graphite tubes 240m long, but there are certainly 5m to 10m long tubes with flanges for connection to additional lengths of Graphite tubing. Heck, we even make Graphite and RCC bolts / nuts / studs / gaskets for connecting flanged piping.
If you require a 240m long heat pipe, that would imply 24 of the 10m long tubes, and possibly some sort of exterior support structure using stranded Carbon Fiber acting sort of like the suspension bridge cable-stays, which can natively survive high temperatures since they're made from pure Carbon as well.
complex pure Graphite components such as this jet mixer are also possible:
The components in some of these chemical processing plants are of considerable size because they run the Sulfuric acid through one set of pipes while they run water outside the pipe to absorb heat from the chemical reaction taking place inside the smaller diameter Graphite tubing. These chemical processes run at modest pressures but can and sometimes do achieve high temperatures.
#190 Re: Martian Politics and Economy » Corporate Government » 2025-04-16 04:12:04
RobertDyck,
Meanwhile George W. Bush invaded Iraq when there was no reason. Al Qaeda attacked on 9/11, and they were in Afghanistan. Iraq had nothing to do with it.
Meanwhile, you're railing against someone I never voted for. Tilt at that windmill a little harder, for all the good it will do.
Canada's medical system isn't perfect, but it's better than the US.
That's a matter of personal opinion. All the Canadians who come to the US to receive medical treatment for things your medical system fails to treat in a timely manner would clearly disagree, and they let their own private money do their talking, after your government has confiscated a significant portion of their paycheck, yet failed to provide those medical services. Canada's health care system is not "better" than the American system, merely different. Both systems fail in different ways. An honest person would admit that. A cheerleader would advocate for one system the other. I think both systems should be options that an individual can choose to take or leave.
As for Russia, you are not arguing against war, you're arguing for it.
Let's follow your line of thinking regarding what Russia will do in response to its logical conclusion. We somehow manage to wipe out Russia's conventional military forces. How do we do that? We invade Russia. What does the Russian government do if its military is facing annihilation at the hands of western military forces? It lobs its only remaining functional weapons, which would be its nuclear weapons, back at us. What happens then? Oh right, total destruction of Europe, America, Russia. What a brilliant plan. Why didn't I think of that? For starters, I'm not someone who thinks the Russians will decide to stop fighting when they're facing annihilation. What do I base that evaluation on? The Japanese military never stopped fighting after we'd already wiped two of their cities off the map with nuclear weapons. Both their military and their people had no plans to stop fighting us. Germany? Ditto. Stalingrad? Same.
There's yet another group of people who use this same line of reasoning- the Jews and the Palestinians. They're going to perpetually be at war with each other as a result, and nothing will change as long as they continue to use that line of reasoning.
You seem to want Mars to be some form of escapism from very human problems, and view the government as the problem, while fixating on some aspect of governance that you see as unfair or unwise. Nothing you've written so far makes me think you actually understand, or even attempt to understand, anyone else's viewpoint. Congratulations, you're exactly like the people you despise. You're no better, except in your own head, and no different.
First, the Supreme Court of the US has already ruled this is wrong.
According to you, our Supreme Court is wrong. You are very far from the first or last person to disagree with a Supreme Court ruling. Thankfully, your opinion is irrelevant. You're not an American and you don't live here. If you disagree so vehemently with American laws, then don't come here. You're looking to find fault over a personal or political disagreement. It's a lot easier to do that than it is to merely attempt to understand an issue or decision from anyone else's viewpoint, but that's also very intellectually lazy.
On the White House's theory, if they abduct you, get you on a helicopter, get to international waters, shoot you in the head, and drop your corpse into the ocean, that is legal, because it is the conduct of foreign affairs.
Timothy Snyder's theory is imputing his personal beliefs about what the White House actually said and did to what he wants it to mean to support his belief system. He has Trump Derangement Syndrome, same as you. President Trump is gone in less than four years. We had a dementia patient in the White House from 2020 to 2024. President Biden is gone now.
The person in this scenario is a foreign national drug cartel gang member. When you and Timmy demonstrate that you give a crap about the rights of all the people these illegals have raped, robbed, and murdered, then perhaps your words will carry more weight with people like me.
To be fair, in the interview on camera with Trump, he said he intends to deport them, not execute them.
That sounds like Timmy's strawman argument, which you "re-tweeted" here, is an outright falsehood, by your own admission. Now that we're both admitting that it was a gross misrepresentation of the actual nature of these deportations, we can proceed to talk about reality, rather than how our emotions make us feel about reality.
Ps. Regarding Trump sending individuals to a prison in El Salvador. It's a good time to remind everyone that Auschwitz was not located in Nazi German either.
Ps. Regarding Trump sending serial rapists and murderers back to their country of origin, since they are not Americans and entered America illegally. I'm guessing that after living with such brutish criminals for a week, assuming you're still alive, you'll be all in favor of tossing them out of helicopters, despite the fact that is clearly not what our government is actually doing with them.
Ps ps. Governor Josh Shapiro now thinks political violence needs to stop after one of his fellow leftists burned down the Governor's Mansion. I get whiplash from watching how fast leftists turn on a dime against criminals, the moment they become their victims. It's as if all the stupid leaves their body in an instant, they start behaving more like mature adults, and stop making endless excuses for the horrific things these violent criminals do to people.
#191 Re: Martian Politics and Economy » Corporate Government » 2025-04-15 02:35:31
RobertDyck,
We've been listening to the neolibs and neocons for the past 25 years. All it's brought to us thus far is endless war, economic decay, and further impoverishment of the middle class. If that was their entire plan, then we need a better plan, which they failed to deliver. President Trump at least has economic plans and deals that he's trying to pursue while "the system" tries to maintain the status quo bankrupting America. Whether or not I agree with 100% of everything he does is irrelevant to the fact that I'm finally getting something besides more of the same trash policies that are tantamount to economic suicide.
I don't have any issues with the Russian or Ukrainian people. None. I think they should both be allowed to live in peace, without the incessant meddling of the neolibs and neocons from the west. As near as I can tell, we kept poking at them until we fomented a war, so now they're at war. I would greatly prefer that we quit doing that.
I voted for the only guy who publicly stated that he was going to negotiate an end to the endless wars, but I'm advocating for war. Gotcha.
But your argument is called a "strawman". You create a problem that doesn't exist, then argue against your own problem.
Let's say that China follows through with their publicly stated plan and sends people to Mars, with the intent to mine resources and colonize Mars. Let's further stipulate that they decide they're not signing on to this "One Mars Government" that the rest of us set up on Mars.
If we attempt to impose your "no military weapons" policy on the Chinese, what do you imagine their response will be?
If you said "a war", then you'd be correct. Your government will make a demand they refuse to acquiesce to and then your options are to talk endlessly while accomplishing nothing, which is what the UN does, or to use military force, at which time they will respond in kind, and when last I checked we call that state of affairs a war.
Since that very specific problem clearly does exist right here on Earth, why do you suppose it won't follow humanity to Mars?
We cut off all military weapons to Iran. Whatever that was supposed to accomplish, the end result was that Iran made their own weapons. Russia and China have supplied some older SAM batteries and ancient fighter jets, yet the thousands of offensive combat drones and cruise or ballistic missiles that the Iranians have manufactured and supplied to their various terrorist networks are entirely home-grown weapons projects. All the economic sanctions and sporadic military operations haven't deterred them from arming themselves. Since Iran's manufacturing base is entirely domestic, there's nothing effective we can do to stop them, short of engaging in a war.
What is your government's course of action, which does not lead to a war, if the Chinese decide they absolutely are putting colonies on Mars, and absolutely refuse to submit to the authority of your One Mars Government?
#192 Re: Martian Politics and Economy » Corporate Government » 2025-04-14 21:07:47
RobertDyck,
Has Texas gone to war with California?
California fought for the Union and Texas fought for the Confederacy during the American Civil War. If that was the example you wished to use to show us how well your federal system would work to prevent war, then that's an automatic fail.
Anybody who has machine tools and chemicals can make weapons. To merely survive on Mars, all the same tech that will be required for civil purposes could just as easily be repurposed for war. Many technologies are what we term "dual use". A fertilizer plant is literally the exact same technology used to make explosives. Precise machining of metal tubes for heat exchangers or plumbing is very close to the tech used to make gun barrels.
Beyond that, the point you keep deliberately ignoring is that "the enemy gets a vote". You still act as if they're supposed to simply accept whatever it is you do, roll over, and play dead. That doesn't happen in real life. People do things you won't approve of. How over-the-top your reaction is, typically tells them how justified or unjustified they were in thinking that you were some sort of controlling despot.
I know of only one foolproof method to prevent war. Men of good moral character and conscience, as well as kindness towards others, are elected or appointed to positions of power. That means men who think logically, are not overly-emotional in their reactions to things they don't like, or prone to stigmatizing viewpoints that disagree with their own, to the point that they stop considering information that disagrees with whatever is going on inside their heads.
Do you know what I see "missing" from much of the leadership in the world today?
Many of those who are elected or appointed do not seem to give a tinker's damn about their own people. They literally thumb their noses at the plight of their people because they have gained wealth, power, and privilege, by whatever method, so they seem to hold the view that everyone else no longer matters.
If I was the Chairman of the Communist Party, someone who survived the various purges, plagues, and mass starvation by some minor miracle, the very last thing in the world I would want to subject my people to is any more of that. And yet... The people in positions of power like Chairman Xi and President Putin are either so ideologically blinded or so fixated on what they want, that they're going to perpetuate the system that took the people from them that they cared most about in this world, as well as their prosperity. I can't think of anything more self-defeating than that.
Any system of governance that requires you to denounce your own family members in public, merely for reading the wrong book, is rotten to its core. That would be why we still have wars over ideology. They're not going to go away unless we're no longer human.
#193 Re: Not So Free Chat » Politics » 2025-04-14 15:12:23
GW recently told me that the number of leftists who condone violence, or will act out in violent ways, is a small minority of radical leftists. I found his belief somewhat humorous, but clearly a majority of self-identified leftists disagree with him. Like so many people who have limited interaction with others, they're in denial about what those "other leftists" actually believe.
New survey reveals disturbing trend in support of political violence
WASHINGTON (TNND) — A new report from the Network Contagion Research Institute reveals a disturbing trend in support of political violence. Researchers found a significant number of Americans who identify as 'left of center' support deadly violence against President Trump and Elon Musk.
...
To assess support for political violence, all 1,264 U.S. residents surveyed by NCRI were asked to classify their political ideology. The survey defined 'left of center' as those who chose far left, liberal, and slightly liberal. The results among that group reveal that "assassination culture" appears to be emerging."A lot of folks on the left are probably feeling a sense of hopelessness or despair following the election loss," said Schwartz.
Some 38% of the total respondents said it would be "somewhat justified" to murder President Trump, while 31% said the same about Elon Musk. However, for those self-identifying in that group who were more left-leaning, those numbers grew to 48% and 55%, respectively.
...
The survey also looked at support for destroying Tesla dealerships, with 39% of all respondents saying it's partially acceptable and 57% of those left of center saying the same thing.
Survey Results
To assess support for political violence, we surveyed 1264 U.S. residents, balanced to reflect Census data on race/ethnicity, gender, age, and education.4 Respondents were asked demographic information, political identity, several political and psychological scales, and questions concerning their acceptance of specific forms of political violence. A score of 1 meant that the respondent considered political violence completely unjustified. Scores from 2 to 7 indicated that they believed there was at least some justification for political violence, and, in the case of those choosing 7, that it was completely justified.
The survey revealed several troubling trends. Over half of those who self-identified as left of center (55.2%) reported that if someone murdered Donald Trump, they would be at least somewhat justified (see Figure 1; similar proportions supported murdering Musk and destroying Tesla dealerships). This includes 13% who said this murder would be “Completely Justified.” Similarly, nearly half of those who self-identified as left of center said the murder of Elon Musk would be somewhat justified (or greater), with about 9% saying this is “Completely Justified” (see Figure 3). Over ⅓ of all respondents believe it is at least somewhat acceptable to destroy Tesla dealerships to protest Elon Musk’s involvement in the Presidential administration.
A majority of people who are merely "left-of-center" claim it's at least "partially acceptable" to either murder people or destroy their property over political disagreements.
I find that people who have attained the highest levels of education and intellect also suffer from the greatest degree of cognitive dissonance about how other people think and what they find acceptable, almost as if they live in their own little world that doesn't come close to approximating ugly reality. This is unfortunate for them, but even more unfortunate for the rest of us since high levels of education and status are also frequently associated with political, monetary, or other forms of power.
#194 Re: Human missions » Starship is Go... » 2025-04-14 14:45:55
GW,
My underlying point is that SpaceX requires RCC to make their fully exposed body fins and hinge lines survive reentry heating. We're not going to achieve ultra-light-like wing loading for a super heavy lift launch vehicle because it's not practical. We have our "go-to" materials for surviving reentry heating and they happen to work.
#195 Re: Martian Politics and Economy » Corporate Government » 2025-04-14 14:26:49
RobertDyck,
Wars between nations have existed since the invention of writing, and probably before. Long before.
By your own admission, war is not a nation-state or political problem, it's part of human nature, and existed long before writing was invented, and the entire nation-state or "country" concept.
Telling them to stop fighting because they should, or because people are dying, isn't going to do jack shit!
That would be why President Trump decided to stop funding their war. Ukraine is never going to recapture their territory unless we personally get involved, which we're not going to do, because the probability of escalation to a nuclear war is very high. We would rather both parties negotiate a cease fire that they both find acceptable, and have made every effort in good faith towards that goal. Maybe Putin or Zelensky or both are not sincere in wanting to stop their war, but we cannot know that with certainty if we do not try.
I don't want to debate culture. You're a Trump supporter, and Trump people are a cult.
Projection, gaslighting, name-calling, and cry-bullying only works on your fellow leftists. You should know that by now. It's no longer working on a growing number of them, either. People such as myself only find that behavior obnoxious and rude. You don't achieve peace or civility by being obnoxious and rude. You will live in a society where not everyone agrees on the best path forward. That is natural. There are very few situations or circumstances with desirable outcomes where we'd expect to see complete or near-complete agreement if everyone is going through their own rationalization process.
The people you're accusing of being cult members are the ones who are trying to put an end to the war in Ukraine. The people you identify with politically are trying to perpetuate the war.
Liberals such as yourself need not concern themselves with being logically consistent, which is why you can make such blatantly contradictory statements as "I don't want war" and "we need to keep fighting the Russians forever". You either don't mean what you say, or you cannot articulate what you actually mean because your emotions are getting the better of you.
The TV channels you choose to listen to told you it's our job to hate and fight the Russians. They did not tell you that Ukraine was lobbing artillery shells at ethnic Russians who happened to live in Ukraine since 2014, that we helped overthrow their duly elected President because he was an ethnic Russian and wanted more favorable trade arrangements with the Russians, and that we promised to not expand NATO eastward.
If you were merely a curious onlooker watching some fighting unfold in front of you, and your political beliefs were not threatened by who won or lost, then you might ask yourself who started what, why, and when. The issue is that you're not very curious. You've decided ahead of time what to believe, who or what you support, and will religiously ignore anything that disagrees with your beliefs, to the point of self-destruction.
We obviously can't allow that government to rule Mars.
Whatever would future Martians do without liberals starting or perpetuating pointless wars while falsely claiming to be anti-war?
The point is for Mars to be a place where different ideas can be tried. Experimentation to see what works, and what doesn't.
The Ukraine War is a liberal experiment implementing the tenets of your ideology.
How has that war helped Ukraine's birth rate?
But I don't want to get into details here.
If we got into details here, we'd find that I raised two sons and a daughter. You have no children, which you can blame on anyone or anything, but ultimately the only person at fault for that is staring back at you in the mirror. Anyone who is involved in governance should be asking themselves the kinds of questions that you clearly don't ask of yourself, because you don't want to confront the answers. For starters, war is a lot like poverty or "the poor". War will always be with us. We can choose to let it get the better of us, or we can go a different direction when its irrationality becomes too painful to ignore. Some of us have a higher pain tolerance than others, but everyone has a breaking point.
#196 Re: Human missions » Starship is Go... » 2025-04-14 12:19:20
I'd like to point out how ridiculously low 18.75kg/m^2 (3.84lbs/ft^2) truly is. That is the wing loading equivalent of the average ultra-light aircraft, none of which are made from materials that will withstand 800C. For a 150,000kg dry mass vehicle, the heat shield surface area is 8,000m^2. A regulation American football field is 57,600ft^2, or 5,351m^2, which means the heat shield would need to be 1.5X the size of a football field. For all practical purposes, we don't build any flying vehicles of that size.
The Nextel fabric that ADEPT was made from costs around $20/ft^2. It would survive 850C without issue. However, the fabric for this heat shield would cost more than all 6 Raptor engines (now less than $200K per copy), and I'm guessing that this deployable fabric heat shield would need to be jettisoned to allow Starship to land. How do we do that?
This seems like a highly impractical solution without some kind of radical redesign of Starship. Starship might be able to deploy such an enormous heat shield, and it should protect Starship from reentry heating without any real issue, but how does one then land a vehicle ensconced in this giant fabric "lifting body surf board"?
Starship on a football field:
Where the heck are we stowing a heat shield that large and how are we either getting rid of it to land vertically, or somehow using the heat shield to soft land on the ocean?
#197 Re: Martian Politics and Economy » Corporate Government » 2025-04-14 11:46:18
RobertDyck,
After all, there would be a strong temptation to duplicate all the problems that currently exist in western society.
What are the problems that currently exist in western society, as you see it (as of right now, not 10 or 20 years ago)?
Who or what, or what events and activities, caused those problems?
How does a federal government that doesn't enforce minimum standards for the age of marriage, for example, remedy those problems?
If you moved from one area of Mars where the age of consent / marriage is 16, to another where the age of consent / marriage is set at 18, how does that serve to reduce the litigiousness of modern western society?
That seems like a system in which marriage can be redefined by local governments to mean whatever they want it to mean. If marriage is not defined at the federal level, then you have no guaranteed equal protection under the law the moment you move between local jurisdictions.
Should the government, local or federal, involve itself in marriage at all?
That's a different question than age of consent in a sexual relationship. I'd like to point out that distinction. If the federal government says the legal age of consent is 18, then it's not telling anyone who can get married, only whether or not someone is considered a minor child who should not be in a sexual relationship, because they cannot be held legally responsible for their actions, rather than an adult who can legally be involved in a sexual relationship.
At what age should someone be held legally responsible for their own actions, and to what extent?
That seems to be the crux of the matter.
Both western and eastern societies seem to set different ages for different activities.
Age of consent seems to vary from is as low as 12 in Cuba, to as high as 21 in Bahrain. Beyond that, many countries distinguish between two minors engaging in a sexual relationship vs a minor and an adult by legal definition. Some countries tie the age of consent to marriage, while others do not. A few countries have different rules for homosexual relationships vs heterosexual relationships. All in all, it's a very "mixed bag" regarding what people consider acceptable or normative.
#198 Re: Single Stage To Orbit » SSTO Minimum Isp to Achieve Orbit » 2025-04-13 13:33:56
Dr Clark has made it pretty clear that what he actually wants is a SSTO version of Starship. Unfortunately, Starship uses the wrong technology set for a fully reusable SSTO. Any structural material weaker than T1200 fiber is unsuitable. All metals are far too weak and heavy. We need to figure out how to create an integrated RCC primary structure / thermal protection system with sacrificial thermal barrier ceramic coatings to limit surface erosion during reentry. All propellants less dense than RP1 fail to deliver sufficient Total Impulse for a reasonable propellant tank volume. Raptor generates sufficient thrust per unit of engine weight, but does nothing to address the propellant volume disparity with RP1. Total Impulse delivered per unit of propellant volume dictates acceptable chemical propellant combinations for SSTOs, because it affects structural mass and mass fraction, since hoop stress from internal pressurization loads tend to dictate minimum structural mass requirements with LCH4 and LH2.
Using 90% of vacuum Isp, you get 304.2s for RP-1 (RD-180), 324.9s for LCH4 (Raptor 3; sea level model), and 382.5s for LH2 (RS-25). LH2 is clearly better than RP1 on Isp, but that figure of merit is highly misleading without understanding just how much Density Impulse affects Total Impulse for a given vehicle dry mass, by way of its propellant tank structure- the largest structural part of the entire vehicle.
Oxidizer: 2,339.2kg (1.746m^3 of LOX at 1,340kg/m^3)
Fuel: 860kg (1m^3 of RP1)
Total Propellant Volume: 2.746m^3
Engine: RD-180
Mixture Ratio: 2.72:1
Mass Flow Rate: 1,250kg/s
Thrust: 3,723,161N / 379,657kg-f (90% of vacuum thrust)
Firing Time: 2.55936s
Total Impulse from 1m^3 of fuel: 9,528,909N-s
Propellant Mass for 510s of Firing Time: 637,500kg; 1,899MN-s Total Impulse
LOX/RP1 Propellant Mixture Ratio and Total Propellant Mass and Volume for 510s of Firing Time:
1,250kg/s * (2.72/3.72) = 913.978494623655914kg/s LOX; 1,250kg/s * (1/3.72) = 336.021505376344086 RP1
466,129kg / 347.857m^3 LOX; 171,371kg / 199.269m^3 RP1; 547.126m^3 ttl propellant vol
Oxidizer: 1,606.64kg (1.2m^3 of LOX at 1,340kg/m^3)
Fuel: 422.8kg (1m^3 of LCH4)
Total Propellant Volume: 2.2m^3
Engine: Raptor 3
Mixture Ratio: 3.8:1
Mass Flow Rate: 1,160kg/s
Thrust: 2,471,276N / kg-f of thrust (90% of vacuum thrust for sea level nozzle)
Firing Time: 1.74952s
Total Impulse from 1m^3 of fuel: 4,323,540N-s
Tank Volume for RP1 Equivalent Total Impulse: 4.849m^3 (77% increase over RP1)
Propellant Mass for 510s of Firing Time: 591,600kg (92.8% of RP1); 1,260MN-s Total Impulse (66.4% of RP1)
LOX/LCH4 Propellant Mixture Ratio and Total Propellant Mass and Volume for 510s of Firing Time:
1,160kg/s * (3.8/4.8) = 918.333333333333333kg/s LOX; 1,160kg/s * (1/4.8) = 241.666666666666667kg/s LCH4
468,350kg / 349.515m^3 LOX; 123,250kg / 291.509m^3 LCH4; 641.024m^3 ttl propellant vol; 17.2% vol increase over RP1)
Oxidizer: 425.4kg (0.317m^3 LOX at 1,340kg/m^3)
Fuel: 70.9kg (1m^3 of LH2)
Total Propellant Volume: 1.317m^3
Engine: RS-25
Mixture Ratio: 6:1
Mass Flow Rate: 514.49kg/s
Thrust: 2,050,942N / 209,138kg-f of thrust (90% of vacuum thrust)
Firing Time: 0.96464s of firing time
Total Impulse from 1m^3 of fuel: 1,978,421N-s
Tank Volume for RP1 Equivalent Total Impulse: 4.816m^3 (75% increase)
Propellant Mass for 510 Seconds Firing Time: 262,390kg (41.2% of RP1); 1,046MN-s Total Impulse (55.1% of RP1)
LOX/LH2 Propellant Mixture Ratio and Total Propellant Mass and Volume for 510s of Firing Time:
514.49kg/s * (6/7) = 440.991428571428571kg/s LOX; 514.49kg/s * (1/7) = 73.498571428571429kg/s LH2
224,906kg / 167.840m^3 LOX; 37,484kg / 528.692m^3 LH2; 696.532m^3 ttl propellant vol; 27.3% vol increase over RP1)
Implications:
To deliver the same 1,898,812,110N-s (1,899MN-s) Total Impulse that LOX/RP1 delivers by firing for 510s:
Raptor 3 has to fire for 768s, which implies 705,280kg (526.328m^3) of LOX, 185,600kg (438.978m^3) of LCH4, 891,289kg (965.306m^3) in total
RS-25 has to fire for 926s, which implies 338,681kg (242.747m^3) of LOX, 56,447kg (796.148m^3) of LH2, 476,327kg (1,038.895m^3) in total
You may or may not need to deliver 1,899MN-s to push any particular payload into orbit using lighter / higher-Isp propellants, but if that's how much force you require to deliver a heavy payload to orbit, then your propellant volume increases for equivalent total force generated, by 76.4% for LCH4 or 89.9% for LH2.
Space Shuttle Main Engines typically fired for about 520s. I used 510s, which is close enough to what I could recall from memory. Using 90% of vacuum Isp, Total Impulse equates to 1,066,489,840N-s over 520 seconds, so 3 RS-25 engines would deliver 3,199,469,520N-s. The pair of Solid Rocket Boosters delivered about 3,309,476,870N-s. All together, 6,508,946,390N-s of thrust was required to deliver a 116,120kg Space Shuttle Orbiter to LEO. Space Shuttle consumed approximately 997,904kg of APCP plus 735,601kg of LOX/LH2 to achieve orbit, 1,733,505kg in total, which is pretty darn close to LOX/RP1.
How much of each liquid bi-propellant combination do I need to generate 6,508,946,390N-s of thrust?
LOX/RP1: 1,597,846kg (1,192.422m^3) of LOX; 587,443kg (683.074m^3) of RP1; 2,185,289kg (1,875.496m^3)
LOX/LCH4: 2,418,744kg (1,805.032m^3) of LOX; 636,511kg (1,505.467m^3) of LCH4; 3,055,255kg (3,310.499m^3; 177% of LOX/RP1)
LOX/LH2: 1,399,547kg (1,044.438m^3) of LOX; 233,258kg (3,289.956m^3) of LH2; 1,632,805kg (4,334.394m^3; 231% of LOX/RP1)
The propellant mass differential between LOX/RP1 and LOX/LH2 is only 198,299kg in favor of LOX/LH2 for equivalent Total Impulse.
Will that 198t of additional propellant mass for LOX/RP1 over LOX/LH2 make an actual difference to payload mass for a SSTO?
No. The driving forces behind vehicle dry mass fraction are propellant tank volume and hoop stress from internal pressurization, not aero loads or acceleration loads. LOX/LH2 engines typically have 75:1 thrust-to-weight ratios, whereas LOX/LCH4 and LOX/RP1 are 185:1 to 200:1. LH2 propellant tanks require the highest internal pressurization levels and are physically the largest in size across all common fuels.
The Space Shuttle Orbiter's internal volume, excluding engines and control surfaces, was about 965m^3 and total surface area was about 1,105m^2. Therefore, a SSTO Space Shuttle's internal volume for propellant is about 1.95X that of the historical Space Shuttle Orbiter, if powered by LOX/RP1, 3.43X larger in terms of internal volume if powered by LOX/LCH4, or 4.49X larger if powered by LOX/LH2.
Rockwell's VTHL SSTO concept was to be powered by LOX/LH2 only, have roughly the same payload as the utlimate Space Shuttle design, so it was substantially larger than the historical Space Shuttle Orbiter as a result. That said, total payload to orbit for either LOX/LH2 plus APCP or LOX/LCH4 or LOX/RP1 is the same 116,120kg. The only major difference is how large the vehicle volume becomes and its GLOW. My assertion is that it has to remain small because materials don't get any stronger as you scale-up the total volume and surface area.
200:1 TWR RP1 fueled engines, for a 2,301,409kg GLOW and 1.5:1 liftoff TWR, would weigh 17,261kg
185:1 TWR LCH4 fueled engines, for a 3,171,375kg GLOW and 1.5:1 liftoff TWR, would weigh 25,714kg
75:1 TWR LH2 fueled engines, for a 1,748,925 GLOW and 1.5:1 liftoff TWR, would weigh 34,979kg
Lockheed-Martin's externally box-stiffened 10m diameter composite cryogenic tank demonstrator had an internal volume of 634.297m^3 and a weight of 2,981kg, so 3 of them, sufficient to hold 1,875.496m^3 of LOX/RP1 propellant, would weigh 8,943kg. It was made with IM7 fiber (820ksi tensile strength) vs Toray T1200 fiber (1,160ksi tensile strength), a 41.5% strength improvement.
116,120kg - 8943kg (propellant tanks)- 17,261kg (engines) - 17,149kg (heat shield) = 72,767kg remaining (landing gear, pressurized cabin, payload)
The 17,149kg heat shield mass figure represents the historical Space Shuttle Orbiter's heat shield weight multiplied by 2. We have lighter more protective materials available today that did not exist in the 1970s.
For composite cryogenic propellant tanks filled with either LOX or LH2, NASA testing of Boeing, Lockheed-Martin, and Northrop-Grumman submitted cryogenic propellant tank demonstrator designs determined that if maximum vehicle acceleration was between 3g and 4g, then hoop stress from propellant pressurization dictates the minimum structural mass required. LH2 requires the highest internal pressurization between LOX / RP1 / LCH4 / LH2 propellants. All tanks tested were made from IM7 (820ksi tensile strength) fiber, which is much weaker than T1200 (1,160ksi tensile strength), yet all of them were dramatically lighter than a new mass-optimized Al-2195-T6 alloy, on par with paper-thin stainless steel balloon tanks that collapse under their own weight unless they're kept internally pressurized. All composite tanks burst at much higher pressures than the 2195 analog used for comparison.
If you double the required internal vehicle volume to produce the same total force to accelerate the vehicle to orbital velocity, the design problem becomes much more difficult to reconcile with materials that don't get any stronger as you scale-up in size. Volume doesn't scale with surface area, so the problem is not quite as severe as it appears on the basis of volume numbers alone, but you cannot more than double the internal volume required for LH2 propellant without a lot more structural material and engine mass. The payload mass fraction is rapidly displaced by vehicle structural mass fraction, and you end up with structures at the edge of their strength limits.
#199 Re: Human missions » Starship is Go... » 2025-04-12 19:50:02
If you create a deployable fabric heat shield considerably larger than the vehicle being protected, how do you either jettison the heat shield or stow it in order to land?
We have a wealth of experience with improved lightweight heat shielding materials. The fastening methods, rather than the tiles themselves, seem to be failing. The tile losses appears to occur near discontinuous surfaces (the "step" or "lip" between protected areas that have tiles and nearby areas that don't any) to the oncoming flow around those complex hinged joints. I see what looks like gas cutting from the wake coming off the leading edges. As the AoA is varied to steer the vehicle during reentry, some of the flow appears to wash over parts of the vehicle that may not have that crazy-hot flow impinging upon it at reduced AoA. Maybe I'm wrong about that, but from the videos that's what it looks like to me.
The Space Shuttle Program developed Advanced Carbon-Carbon (ACC- an advanced RCC derivative) aileron, body flap, and rudder structures that both resisted mechanical / aero loads and acted as "hot structures" which had no thermal insulation. This is to say, the materials were not a more complex sandwich of HRSI, backing insulating felt, and Aluminum alloy primary structure. This was projected to save 700lbs of weight for the large body flap, and up to 7,000lbs of weight if the ailerons, rudder, and body flap were all made purely from ACC vs a mix of different TPS and structural materials.
Here's the NTRS Report:
RECENT ADVANCES IN CARBON-CARBON MATERIALS SYSTEMS
They were also contemplating replacing FRSI tiles on the orbiter's belly with ACC and switching to a hot structure that required little to no insulation. Starship's 304L primary structure could have a very thin layer of ACC with a very light aerogel insulation layer underneath. The body flaps could be replaced with monolithic ACC structures. This seems like a better way to solve the peak heating problem than fragile tiles near hinge lines. Monolithic ACC "fins", like the ACC orbiter body flap from that NTRS Report, doesn't have any tiles to lose. It's intrinsically capable of withstanding the temperatures FRSI tiles are subjected to, plus a little more, in addition to resisting the aero loads so no structure steel reinforcement is required. NASA also developed metal fasteners that wouldn't crack the ACC as they expanded at different rates.
This is less involved change proposal than completely redesigning the upper stage into a lifting body that lands on a runway.
#200 Re: Human missions » New NASA Director nominated » 2025-04-12 00:01:37
GW,
Can you identify any specific behavior of Elon Musk that you find atrocious?
Can you opine as to why radical leftists decided that the most appropriate response to Elon Musk's behavior, even if it was atrocious by your definition, was to then go out and destroy the property of their fellow leftists and to assault them for doing business with one of their fellow leftists?