farmerben
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Posts posted by farmerben
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I wonder if a balloon is a good way to descend through the Earth's atmosphere. Potentially it opens up whole new exploration missions on other planets including the giants.
How would we go about figuring out the rentry heating profile? I wonder if a titanium foil balloon of hydrogen would survive.
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I the engines are angled 8 degrees out they still provide 99% downward thrust. The hull would be protected against rocket exhaust and most of the debris.
There is also the problem of engine exhaust being reflected back up when close to the surface. Landing legs must reach much lower than engines due to this.
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Engine thrust can blow regolith all over the place, possibly damaging the engine. A solution to this could be a return to the so called "pendulum rocket fallacy". Putting the engines higher up reduces the regolith dust.
In KSP engines like the spider, twitch, and thud are ideally suited for this. But, does this work in real life? We also have to keep engine exhaust a safe distance from the hull.
A mushroom shaped lander may be ideal with the crew and payoad in the mushroom stem, the fuel in the mushroom cap. This not only eliminates the need for ladders and cranes, it offers a thick radiation shield for the crew compartment. The moon blocks 1/2 of all the radiation, the fuel and oxidizer can absorb nearly all of the rest.
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On 4/18/2022 at 12:00 PM, StrandedonEarth said:
Once the infrastructure is set up, magnetic launchers will be dirt cheap, and why brake into LEO? Direct entry will be cheaper.
Now for the controversial part: simply slam the slugs of metal into the deserts and pick up the pieces. The dust clouds raised will counter the greenhouse effect that causes global warming. But it also turns until a cheap, non-nuclear weapon of mass destruction, fired from some very high ground (although even higher ground is available outside Earth’s SOI…)
Shaping the metal into whiffle balls might a solution. With decent backspin, a whiffle ball can generate more lift than just about anything. On the other hand wind would take it away from precision landings.
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I finally ran this mission and created and album. Its been a long time since I posted images. Can someone please guide me how to do that. I don't want to register any more accounts than i have to.
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Uranus and Neptune have gravity similar to Earth and Venus. The only problem is supercritical fluids at thousands of atmospheres pressure. We don't know how big the rocky cores are.
Nuking the hydrogen and helium off into space sounds very wasteful. But perhaps with most of the atmospheres removed we would have two more livable worlds... almost as easy to colonize as Venus.
Gamma ray lasers might be fiction. Lasers depend on mirrors. You can generate a lot of gamma rays, but you need gamma ray mirrors to get the lasing effect for more than one pump. Stellar corona lasers are another good way of removing gas giant atmospheres.
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On 4/5/2022 at 10:01 AM, kerbiloid said:
Calculate their area and put on google maps.
Upd.
https://www.statista.com/statistics/196106/average-size-of-farms-in-the-us-since-2000/
Average US farm = 428 acre = 1.7 km2.
Average O'Neill cylinder: d = 8 km, L = 32 km.
Sside = pi * 8 * 32 = 804 km2.
Swindows = 804 / 2 = 402 km2.
236 average US farms, if the surface totally consists of plowland.
https://www.nass.usda.gov/Publications/Todays_Reports/reports/fnlo0220.pdf
2 million farms in US.
O'Neill cylinders per USA needed = 2 000 000 / 236 ~= 8 500
Number of US humans per O'Neill cylinder = 330 mln / 8 500 ~= 39 000.
I.e. O'Neill cylinder can provide with food ~40 kiloamericans.
Or, if count the exported food, ~ 100 kAm.
(Exactly like I had calculated before).
A cylinder of that size could support about 50,000 grass fed cows, maybe more if we breed the cows to be more spherical.
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It seems like the reflectors offer plenty of adjustability to control temperature throughout the habitable zone and maybe beyond. People who live there will want a variety of plants. For strictly industrial use (algae farms), etc simpler structures will work.
This approach is very efficient at creating habitable space with a minimum of mass. On planets, most of the material gives you nothing but gravity. On Earth land is already quite expensive.
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Living inside an O'Niell cylinder might be more pleasant than living on the surface of Mars. Most O'Niell cylinders would attempt to create a stable, desirable ecosystem. In our solar system they could resupply or reset the ecology in special cases. Producing most of their own food is probably not their biggest problem.
On an interstellar mothership mission we would want to bring the largest possible seed bank. And hope to find worlds where any type of ecosystem can take hold. In the timescales it takes to travel between the stars with lots of mass, evolution will take each fertile world in its own unforeseeable directions.
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41 minutes ago, Nuke said:
i think a better way would be to construct an artificial asteroid entirely out of the materials you need for the colony to be used at a later date. you would have a core hab module (hab centrifuge, industrial area, the works). this would be surrounded by spherical insulated double hull pressure vessel. outside that you would have water ice storage, other ices (like ammonia or hydrocarbons) separated by bulkheads. within the ice can be storage containers for various useful metals and other materials, cold storage for biologicals like seeds and embryos. also this would be your warhead magazine and nuclear reactors. another pressure hull would surround this, followed by insulative material and then an armored outer hull layer. out side that would be remass material to be ablated by warheads. such a craft could be relatively large, support a healthy human population, and be self sufficient for some time in the target system in the event that any suspected biosphere be unviable. this maximizes colonization options, you could set up terrestrial colonies and/or use the ship as a permanent station in an astreroid belt or moon system. at the destination the bulk of the ship can be cannibalized to kickstart colonization.
We haven't had much success yet with self sustainable colonies even on Earth. It would take a small world worth of supplies to colonize another star system.
Vesta is 500 km in diameter of iron ore. You could use quite large fusion explosions and still have impulsive forces less than the gravity of the body itself. Ice and so on would stick to the outside by gravity. And the pusher plate could be rigidly attached to the entire vessel. For crew comfort ( not necessity) use sprung chairs or bunks for the crew.
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It is a massive advantage to be massive with an Orion style drive. I see it as something you can build out of asteroids and then use for interstellar colony missions.
The crazy part of the idea are the giant springs. The more massive we make the entire thing the less need for springs.
I mean we just need to save up enough deuterium... then we can hollow out Vesta and go for a spin around the galaxy.
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19 hours ago, JoeSchmuckatelli said:
In the "Earth is resilient" column, add: Cleared tropical forests can regain ground surprisingly fast | Science News
Most tropical soils are naturally very poor. Evidence indicates that natural soils which have 0.5% carbon can be raised to 9% through human intervention. https://en.wikipedia.org/wiki/Terra_preta
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I can't find the old features I used to use all the time. Right clicking parts used to permit autostrut, fuel flow priority, destaging fairings entirely, and more. How do I turn these on?
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A Maxwell's Demon to interfere with the Hawking radiation could do awesome things. Larry Niven had a bit in the book "Shipstar" about rotating black holes with opposite electric charge, to send messages on gravitational waves. The Demon could not only decide which charges to cast back into the black hole, it could also create powerful magnetic fields by selecting charges to orbit permanently in the accretion disk, or setup powerful antimatter explosions by putting charges on eccentric orbits to collide at some future time. I'm not sure if any of that would speed up the death of the black hole. Not that anybody more serious than me or Niven has developed a theory for black holes with net electric charge.
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Error!
I see a thread with an interesting scientific question, then first post immediately shifts to a fictional FTL thing.
Spacescifi, I like you and I like your contributions. But this style of thread creation is slightly offensive.
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19 hours ago, K^2 said:
. I can build a proton accelerator with sufficient energy in my living room, unless my wife stops me, but I won't be able to generate a current
True that. A 2-3 diameter cyclotron has sufficient energy. Maybe if you had dozens of them surrounding a reactor then you would have something. Nobody to my knowledge has tried to mass produce proton accelerators for the price of TVs.
Anyhow alpha-beryllium neutron sources are an easier way to get neutrons. And still to this day the most inexpensive fission reactor is the RBMK 1000.
If we position a reactor in the right spot, we could harvest high energy protons.
Imagine a reactor target with 1000 cathode ray tubes surrounding it. The cathode ray tubes would deposit electrons on our target while becoming positively charged themselves.
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8 hours ago, Cavscout74 said:
I just saw a news headline saying 40% of Americans surveyed by the CDC tried to use bleach to disinfect their food to prevent Coronavirus transmission. I've always been proud to be an American, regardless of our faults, but seeing that article, I may have to move.
The only saving grace is that only 502 people took the survey. I just need to figure out how 196 people (39%) that are obviously too stupid to live managed to turn on a computer, connect to the internet & fill out a survey. Oh, wait, facebook, that's how.
Using bleach to disinfect drinking water is actually a thing. Here are instruction from the US EPA
https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water
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I think muons are more likely to initiate fusion if you get one to replace an electron in the ground state of H22 There are fast muons raining down on us all the time, we just need more slow ones. Maybe a giant airship full of deuterium gas could get some.
The Van Allen belts have plenty of high energy protons. We just need to concentrate the current. A giant magnetic field like a torus could pinch the protons into higher concentration. Or we could beam electrons at a target giving it a negative charge and allow it to pull in protons that way.
If we are talking about compressing Uranium or Thorium into supercritical densities, I don't know if that is possible. Plutonium has several different density states, and the transition from one to the other can go from subcritical to supercritical. I believe that transition could be achieved by hitting plutonium with a hammer. Other metals like iron can change structure by hitting them with hammers, but they barely change density at all. Is that what we are talking about? Using lasers or magnets to hammer solid metals into super densities? I'd like to see more evidence that this phenomenon is a thing.
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Carlo Rubbia at CERN has done decades of research using proton beam spallation to drive subcritical reactors. This technology is spectacular all it needs is inexpensive high energy proton beams. Or a seat in the Van Allen belts.
There is an economical device to accelerate electrons using a so called laser wakefield. If proton acceleration could be achieved on a similar scale, then beam driven subcritical reactors would be a reality.
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32 minutes ago, JoeSchmuckatelli said:
… I know that based on this information I should be able to pinpoint what star the signal is coming from. Sadly, I don't have the maths for this. But can you guys help me to know whether my scratch-paper figuring is correct?
This little thought experiment came about through a conversation with a couple of friends and my son several nights ago. The debate meandered about which direction is 'straight up' at night after sunset, and eventually what the angle was between straight up and the sun. After drawing circles and rays on a napkin I was able to convince them that 'straight up' immediately after sunset is a pretty sharply acute angle with the sun, despite all appearances to the contrary.
So I've tried to figure this out on my own, but what I'd like to do, now, is get someone here to help me understand it mathematically (Mind you, both of my degrees are non-science degrees, so please bear with me!)
I know from reading Patrick O'Brian's Aubrey / Maturin novels (e.g. Master and Commander, et. al.) that for an observer about 100 feet above sea level that his or her horizon is actually about 11 nautical miles. With the earth being 21.000 NM in circumference, if we divide that by 360, we get 60 NM for each degree, and 11 NM is roughly about 1/5th of that... so if I'm correct (and ignoring atmospheric effects) -- "Straight Up just after sunset should be about 1/5th of a degree from the edge of the sun.
Am I correct so far?
So having figured that out, if I determine my distance from the equator - let's say my hill is in Santa Barbara, California (about 2069 NM) - which is about 34 degrees - shouldn't I be able to combine the two angles and the date to figure out what star just happens to be blinking?
I'm assuming at this point I'd have to find some resource that shows where the visible stars are in relation to earth's orbit on a given date.. but would my two angles theory described above be enough to narrow it down?
Huh? I'm sure someone in your group argued that directly overhead was about 90 degrees from the sun. And your argument for a very acute angle is???
Many years ago, on a vacation with my family, I derived the general case for how far you can see over the ocean, based on lines tangent to a circle. I won't derive it again right now, but I can tell you several variables are squared or square-rooted so the approximation you made is not accurate. IIRC standing 6' above sea level lets you see about 4 miles. Hotel balconies let you see 10-20 miles. At long ranges you really see mostly things above the horizon like the crest of a wave and the crest of the next wave beyond it, without seeing any surface in between.
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https://soygrowers.com/dredging-the-mighty-mississippi-why-only-5-feet-measure-up/
The US government is already dredging the lower Mississippi in sufficient quantity to fill 2000 acres of polders every year. From what I can see the mud being reclaimed gives us much less value than it could.
My idea is bring firewood grade timber to the dredging polders. Assemble crude wooden formworks above the water level and set them on fire enough to lightly char, but not fully burn them. Then discharge the river material into the wooden formworks. We allow mud to overflow the formworks permanently burying them. Vehicles driving on top will compress the soil and fill in cavities.
This will build mounds spaced out in the Mississippi delta. The charred wood will absorb nitrates and phosphates, and lock them for a very long time. The carbon will be immobilized for millennia. The higher altitude mounds absorb the impact of hurricanes better. There will still be plenty of wetland, but higher ground interspersed enriches biodiversity and human use.
How does the engineering math work out? That mostly depends on how much labor is required to collect the wood and get it to small ports anywhere on the river. And how much labor goes into the form work for the mounds.
It costs very little to carry 1000 tons of wood on a single barge down the river. Say out standard mound site is 10 acres, and we work on about 100 mound sites at a time. Then one barge worth of wood is enough to build up more than a foot around the perimeter on a site, with plenty extra to burn or bury randomly in the middle. How much forest is that? We can probably get 5 tons of scrap wood per acre consistent with sustainable thinning practices. So 200 acres of forest thinned to load one barge one time. Essentially we are feeding 20 acres worth of excess vegetative scrap per 1 acre of elevated reclaimed land. Where the living matter continuously renews while the buried stuff is immobilized.
There are a lot of questions still to consider of economic, social, and political importance. I'm looking at it first and foremost in terms of the waste streams and externalities we currently generate, and looking for better places to put them.
Like it or not, we live in an era when too many of the young people are under-employed and dependent on others. You know what they do? By day they ride around on ATV's looking for mud puddles and steep embankments tearing up as much forest as possible. At night they set fires, take drugs, and yell at each other. That's fine, it's a free country. But could they please do something useful and not be so annoying.
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Meanwhile the Army and Navy may get ramjets of their own.
As a US taxpayer, I have no problem shooting million dollar bullets like popcorn. As long as our NATO allies give billions of dollars of research grants to companies as old as my long dead grandparents.
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Scintillators are more complex than I had realized as well. I was under the impression that they worked off X-rays and gamma rays, but that is probably because the detectors I am familiar with are shielded to reduce noise. They seem to be directly stimulated by high energy electrons and protons as well. In the case of neutrons and heavy ions I'm not so sure how they work. Some of them are using liquid or gas scintillators to slow down neutrons until they decay, others use neutron absorbers like lithium and boron to bring other elements in the crystal into an excited state.
I did find an interesting article about how the LHC must calibrate and maintain their scintillators because the high energy hadrons cause spallation and fission events in their detection crystals degrading them over time. They are using rare earth elements in their crystals though. There are plenty of lighter salts not as prone to this sort of damage.
Noble gasses and ionic salts can stand up to radiation pummeling in Jovian belts. I doubt if organic materials could survive very long. A metallic sail could tank some of the damage, I had envisioned it's main role as a collector.
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What limits will there be to the scale of such a device? I'm not aware of any important limits on the size of the tube, volume of lasing medium, etc.
One of the limits is damage to the transparent aperture, which could be greater in this environment due to all the extra radiation. But it seems to me the scintillator pumping mechanism could scale to high energies better than a pump based on electrical currents. Both require active cooling at high energies. In the scintillator example all that power is evenly distributed over a large surface.
A stellaser using the solar corona for a gain medium could potentially use an empty hole for an aperture and thus scale to higher energies than any type of laser that tries to contain gas with a transparent window.
deorbiting a hydrogen balloon
in Science & Spaceflight
Posted
Even if exploding due to heat is likely possibility, I think it worthy of an experiment.