Rakaydos
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Posts posted by Rakaydos
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5 hours ago, CastleKSide said:
Thanks for making this thread @sevenperforce
Im a big big fan of nuclear power, for multiple reasons. I honestly think it is the only viable way to get off of a petrochem energy economy, due to articles like https://spectrum.ieee.org/solar-energy-isnt-always-as-green-as-you-think as well as the major study that google conducted some years back.Selected excerps:
Quote> Most manufacturers recycle this waste to make more polysilicon. Capturing silicon from silicon tetrachloride requires less energy than obtaining it from raw silica, so recycling this waste can save manufacturers money. But the reprocessing equipment can cost tens of millions of dollars. So some operations have just thrown away the by-product.
> But accidents do happen and are more likely in places that have limited experience manufacturing semiconductors or that have lax environmental regulations.
> there is a newer approach: thin-film solar-cell technology. The thin-film varieties will likely grow in market share over the next decade, because they can be just as efficient as silicon-based solar cells and yet cheaper to manufacture, as they use less energy and material. (...) Moving to thin-film solar cells eliminates many of the environmental and safety hazards from manufacturing, because there's no need for certain problematic chemicals—no hydrofluoric acid, no hydrochloric acid.
> Making solar cells requires a lot of energy. Fortunately, because these cells generate electricity, they pay back the original investment of energy; most do so after just two years of operation, and some companies report payback times as short as six months.
> the amount of water used to produce, install, and operate photovoltaic panels is significantly lower than that needed to cool thermoelectric fossil- and fissile-power plants.
I'm not sure how you got "Solar is unviable" from this article.
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6 minutes ago, sevenperforce said:
Is it like thermonuclear, where efficiency continues to go up no matter how big you get, or is there a power level where you basically max out your benefits?
Modular-distributed makes a lot of sense for a lot of reasons, but I find myself wondering whether we could ever see the entire eastern seaboard running on one offshore megareactor.
A single reactor is a single point of failure- sabotage, incompetency, enemy actors, political winds, anything that takes it out, takes it ALL out. this also applied to the distribution network to get the power where it needs to go, which isnt 100% efficent either. I dont know the first thing about what the actual numbers are, but at some point, distribution losses and grid failures have to be a larger concern than the "bulk discount" of a larger reactor.
A bigger reactor also takes longer to design, build and bring online. That's another advantage to small modular reactors.
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15 minutes ago, sevenperforce said:
I would like to get a better idea of the scaleability characteristics of nuclear. Is bigger better/more efficient? Is there a lower limit?
Kilopower is a small reactor NASA designed for use on spacecraft... BEFORE Starship was on the horizon to make cheap lift a reality. It's less efficient that Megapower, (Which fits in a shipping container) which is less efficient than utility-scale nuclear, but modular nuclear has the benefits of eventually reaching economies of scale.
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There was a brief period when South Africa was looking like it was going to be a worldwide leader in advanced reactor design, back when Advanced meant pebble bed designs. But their teams ran into problems, I dont remember if they were technical or political, and they lost their lead.
Also relevant: Megapower. NASA's Kilopower's bigger, earth bound (for now) brother.
https://www.lanl.gov/discover/publications/1663/2019-february/_assets/docs/1663-33-Megapower.pdf
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Or, you know, lean into scifi even harder, and have some kind of unobtanium that is even more powerful, and cant be released in smaller amounts. Hyperspacial core tap to a higher energy dimension, which can only be opened for a few fractions of a second but releases enough energy to require a shock absorption plate.
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Orion was an "elegant in it's simplicity" workaround to the problems of making a nuclear engine. "Open cycle" engines, using your depleted power source as reaction mass, are vastly more effective than "closed cycle" ones, like NERV (a reactor heats propellant intead of burning it), the electric-pump rutherford (which only uses the batteries as a "preburner", and still has to dump batteries on the way up), and Ion engines (which use electricity to propell ions at frankly absurd velocities to get efficency, but not much actual thrust)
Chemical rockets are almost all open cycle, burning the propellant in a chamber and letting a jet of the combustion product escape to produce thrust. You cant detonate a nuclear bomb inside a combustion chamber, but Orion showed that you can afford to waste a lot of the potential nuclear blast, if you can run open cycle, even without the chamber to direct the blast into a single jet. (and there was some optimization, that basically turned the bomb into two jets, so they managed to get almost 50% efficency out of it)
But the better open-cycle nuclear engine design is the NSWR, which achieves criticallity in the propellant, AT the throat, so the blast happens in the nozzle where it can be directed.
Both NSWR and Orion have the problem of spewing radioactive waste over your launchpad and the entire launch track, of course. That's the core problem with open cycle nuclear engines. Noone cares when a hydrogen/oxygen rocket spews H2O gas over the launch track, although some more exotic propellants also have concerns. But none of those concerns match that of nuclear waste.
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1 hour ago, JoeSchmuckatelli said:
I hadn't thought about contamination - and I knew escaped Helium wasn't a combustion /explosion risk; rather my concern was the slow loss of coolant in a proliferation of small reactors (increased likelihood of negligent maintenance) - where one placed in a populated area could overheat and... Well, you know.
Thanks for the informed responses!
Modern reactor design loves to play with thermal expansion as an emergency control- because nuclear material has to be densely packed to generate a self sustaining reaction, which heats up the material, which lowers the density of the material. So it's possible to design a reactor that's just barely critical, as long as the coolant loop is functional at removing heat from the reactor- while at the same time making super-criticality a physical impossibility, as the reactor stops working well before the temperatures get high enough to be a problem for containment.
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1 hour ago, kerbiloid said:
They thought, it's an earthquake.
Sounds like a problem with the soyuz, then.
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Lets face it, SpaceX's main selling point is "what have they done this week?" and they have very few dry spells.
But this was supposed to be New Shepards time to shine... and Bezos made it about him, instead of about the flight.
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2 minutes ago, kerbiloid said:
Combustion, fission, and fusion are predictable and don't depend on time and place.
And when (after 2040) all cars become electric, this will harden the things even more.
Neither does SBSP.
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1 minute ago, kerbiloid said:
This year was not that sunny and windy.
And yet, it's still cheap to put solar panels on roofs, over parking lots, and wherever they fit.
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3 minutes ago, kerbiloid said:
In exact limited places and avoiding the utilization problems.
Currently EU is enjoying the green power.
That's the lie that the oil producers (including russia) have sold us, yes...
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11 minutes ago, JoeSchmuckatelli said:
Well - once again, I bring up the difference between inconvenience (and economic cost) vs existential threat. From a species perspective, high heat and humidity are an inconvenience. Sure, the individual in an overcrowded city, reliant upon air-conditioning when the power goes out and the windows won't open is at risk... But as a species, we are adapted.
Plants love these conditions, btw.
Contrast this with reduced food production when it's too cold. Hard to put a sweater on your crops.
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We've talked about feedback loops - and there's an interesting one that you touch on: people's adapting to heat-island cities. We've done this by pumping in water and providing air-conditioning in modern buildings. But lots of people in the world live in buildings that date back to before central air was part of the design. Given the high cost and ugly appearance of retrofitting, many older buildings don't have such amenities. Those are the places where the heat-stroke is happening. In a hotter world, demand for such nice to haves will rise, with it the demand for more cheap power - and what's the cheapest source of power right now?
No-one wants grandma to cook (well, except at dinner time) - and she doesn't want to miss out on the happs in town; so because people demand to live in overcrowded conditions... the cost has to be paid in one form or another.
I'm sure you love thanksgiving dinner, too, but eat like that every day and you arnt going to last a year. According to studies, plant growth rate is limited by available sunlight- while there is some minor benifit to a higher CO2, they arnt going to consume more with the same sunlight.
"Sweater on your crops"- it's called a greenhouse, by the way.
Cheapest source of power: Solar and Wind (https://en.wikipedia.org/wiki/Cost_of_electricity_by_source)
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14 minutes ago, JoeSchmuckatelli said:
I will point out that Out-of-Africa humans do well in hot and humid environments.
Little Ice Age demonstrates that cold is more dangerous than hot.
There's hard limits there. Heat stroke is becoming an increasingly common problem in the warmer regions of the world.
It's not cold that's the problem, it's UNEXPECTED cold. If you know it's coming, you just wear a sweater.
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1 hour ago, kerbiloid said:
1. There is a lot of artificial underground caves. Say, where they mine oil and replace it with water and methanol solution.
2. The carbon dioxide is highly solvable in water.
3. The carbon dioxide can be turned into methanol and ethanol.
4. So, the carbon dioxide can be turned into a carbonated alcohol beverage stored underground in a cave already equipped with pipes for bottling.
5. A champagne is a carbonated alcohol beverage with fruit flavours.
Of course, it's a special secret recipe, exact side of the hill, the year, and so on, but if remove the water and the ethanol, it will be a set of organic molecules without magic.So, a solution.
All produced carbon dioxide should be collected, turned into ethanol and carbonated with the rest of the carbon dioxide.
Then it should be being pumped underground on the oil rigs, and replace the oil, like they do it now with methanol.
When the oil deposit is exhausted, and the cave is full of the carbonated alcohol beverage, they should pour the syntheti champagne extract...
... And voila! Where they were mining oil, there is an undergroud lake of champagne with pipes and cranes to fill the glassware when needed.In case anyone remotely considers the above a serious suggestion- no. The long-chain hydrocarbons you're displacing contains far more carbon than the CO2 you are filling the same volume with, meaning that it's better to leave all the oil (and coal) in the ground than dig it up only to rebury it. We've already done enough damage, reversing millions of years of natural sequestration in only 200 years.
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22 hours ago, tater said:
Yeah, this really is the problem with human spaceflight. I love human spaceflight, it's cool, and it's the future I want to see. I just can't wrap my head around a decent use case that results in any economic benefit except tourism—and tourism as a mass market is a long, long pole, IMHO. Needs to be airline level safety, maybe not 2021 airline safety, but certainly airline safety from within the last few decades, so many orders of magnitude safer than space travel is right now.
In order for there to be transportation, there has to be a destination worth transporting to. Without the ISS, Commercial crew would never have happened.
A SpaceX mars base/colony "beachhead" is a precondition for interplanetary science expeditions. There's no reason for Stanford to do LEO science and Lunar science is the domain of "the Goverment". But in the not so distant future, a non-govermental base on mars that offers base-camp amenities for expeditions into the martian wilderness is something that might attract institution-funded geological lewis-and-clark missions, funding the expansion of the base.
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5 minutes ago, JoeSchmuckatelli said:
Dear Space X,
Your Boat Naming Scheme is more interesting than your Dragon Capsule Names.
Please quit letting committees put bland, previously used names on these.
Consider "Falling with Style" for Dragon 5?
Joe
The "committee" in question is the first crew. You want a better name, buy a new-build Dragon capsule flight and name it yourself.
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On 10/5/2021 at 2:18 PM, mikegarrison said:
One of many feedback loops.
Like a microphone in front of it's speaker, this is not a good feedback loop.
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3 hours ago, JoeSchmuckatelli said:
I'm guessing that the flaps are largely useless in the Martian atmosphere for that right up to when things get exciting...
Which probably means 'too late'.
The flaps are actually about balancing during hypersonic entry, with different payloads.
An empty tanker might enter with the nose flaps all the way retracted, while a crewed ship entering with heavy nose windows might have the flaps fully extended, to get the same entry profile.
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19 minutes ago, SpaceFace545 said:
Someone is saying this finally. If SS blows it's gonna leave an N1 size explosions, blah blah cryogenics are safer or something but it's still much larger than the N1. SS needs to be launched extremely far from everything.
I seriously doubt that crew will ever fly on starship but if they do it definitely will need an abort to pull something away from ~350 feet of tanks holding volatile gases.
Note that your typical ICE car's gas tank contains the chemical energy of about 40 kilograms of TNT, and people are allowed to just fill them up at the pump, whenever. Even fill spare gascans.
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12 minutes ago, JoeSchmuckatelli said:
Their slow pace is probably more of a factor in obsoleting them than that.
They should have launched the 'off the shelf' 'existing infrastructure' project in 2017 (leaving SX to play catch up).
From further up the tweet chain:
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On 9/15/2021 at 2:03 PM, tater said:
Assuming LSS works for the first missions, all the other entries look comical unless they are also cheaper per unit capability.
LM has in the past floated the proposal for a lander that was "comically large"... though less so that Starship. Launch it to orbit, utilize a dreaded D-word to get it to the moon, and reuse it for lighter lunar missions than Starship supports.
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2 minutes ago, tater said:
They always expected free flights and this contingency—the vehicle has a larger volume than the Apollo CM, and the toilet is at least a toilet, and not just bags with stick-um around the rim.
While true, the military (and astronauts were very military, in the apollo days) is very good at glossing over the "suck" inherent in military duties. Apollo sanitation would just be an extension of that.
The fact that Dragon is an improvement over apollo in that regard doesnt mean it isnt a step down from an Airstream camper.
SpaceX Discussion Thread
in Science & Spaceflight
Posted · Edited by Rakaydos
"Enviromental racisim" = minorities are forced to live (via economic pressure, redlining, gentrification, whatever) in places most affected by climate change.