farmerben
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Posts posted by farmerben
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I'm skeptical because the cycle they claim to have found is 2.4 million years. If it was every 26 months, case closed. But what changes between Earth and Mars on a 2.4 million year cycle?
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What altitude, angle, and speed does the drop occur?
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Still a very heavy engine, to say nothing of expensive and dangerous. You don't need it to go to Mars. Most of the delta-V required is for landing and launch. The interplanetary transfer is relatively easy.
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Assume storage is a solved problem. How do you generate thrust?
The matter anti-matter collision gives you mostly high energy gamma rays in random directions. You can't mirror those. You could absorb some of it with thick layers of heavy metal or other material, but that means lots of mass. Suppose you absorb 33%, waste 33% and exhaust 33% as a photon drive in the proper direction. We are talking about a very low thrust to weight ratio engine, even if the fuel is light.
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Question: What are the oldest functioning batteries?
Batteries have been a commercial product for close to 150 years now and all sorts of chemistries work, some very heavy by today's standards. I wonder which ones are the longest lasting with functionality, this is an important question for spaceflight too. Could you make batteries that last a century? Is there a tradeoff between longevity and weight?
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7 hours ago, Nuke said:
you mean technology which has already been demonstrated on mars. you just need to upscale it.
there are of course more than one way to do this. you could launch from earth and refuel in orbit, then you dont need a moon base at all. the ship on mars would require landing a return vehicle, empty of course, and refuel it over the course of years in time for human landing. only thing im not sure about is the return aerocapture. we have done that manuver before but never on a man rated craft. and the risk of either burnup or getting flung out into the greater solar system with no hope for either rescue or survival is kind of a big risk.
im only making the point that we dont need anything fancy in the way of propulsion technology to go to mars. so many videos with something like "this new technology will get us to mars in x days" are just clickbait and the tech is either so far down the technological readiness ladder that it would take 10 years to develop, are so theoretical where we cant even be sure it would work at all. its a terrible metric. cost and risk mittigation are the real killers to a manned mars mission.
I agree completely. I would create a designated orbit to orbit vehicle for the Earth-Mars transfer, and a separate vehicle for orbit-surface transfer at each end, so 3 vehicles total.
It's a two year mission because of the orbital resonance. So roughly 3 months on Mars and roughly 20 months in transit.
A dedicated orbit-orbit vehicle can save weight on unnecessary systems, while being more spacious than the surface transfer vehicles.
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Possibly a large moon and tidal oceans are critical for the development of early life on Earth. Assuming the aquatic origins of life, the exact gravity and atmospheric pressure could probably vary.
If the gravity were a little different on Earth space travel would be way easier or way harder, ie single stage to orbit rockets would work or no rockets would work at all.
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Fun fact of the day: For sailing vessels on the sea, trimarans are faster than catamarans and monohulls. And catamarans are generally faster than monohulls. Multihulls do not rely on ballast for their righting moment so they do not need to displace as much water.
If you load multihulled vessels with lots of mass their relative advantage compared to monohulls is diminished. The idea of sailing cargo again is interesting but suffers very serious challenges. If you want to sail fast, sail light.
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If normal economics were inverted propulsion would make you money rather than costing. Maybe it's an oversized Orion ship driven by H bombs. And for a good sci-fi reason running the drive is profitable, more profitable than any known stationary engine, for a very good reason. Then you could justify oversized payloads and get paid twice. Once by the shipper of oranges and once from the profit you make running this drive.
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I thought it was "parts hydrogen"
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Wherever the aliens lie on the spectrum from peaceful to aggressive, it will be to our advantage in almost every case to know more about them than they know about us. If they are technologically our near peer and aggressive, it will be extremely important.
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It is more respectful to learn their language for introductions, just like when travelling to foreign countries.
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15 hours ago, Vanamonde said:
Neutron stars are commonly described as being entirely converted into neutrons, but for metals to be present at least some of the surface matter would have to remain in atomic form with protons present and associated with neutrons in nuclei. Is that common for neutron stars? It's not hard to believe but I've never heard it mentioned before. How deep is the normal matter "crust"?
I think a good fraction of the matter is protons. The neutrons regularly beta decay and the protons regularly reverse beta decay. The electrons may be modeled as a fermion gas distributed throughout the star and not bound to any nucleons.
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It might be fairly well preserved. Certain components will have melted but probably not all of it.
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Static structure relative to the engine and hull should not be difficult. A floor that is 300 tons at 3g will need to support 900 tons. That means steelwork on the scale of a large railroad bridge. It's not far outside the specs of normal seagoing ships, they are designed to take a beating. If the 3g acceleration is relatively smooth, unidirectional, and vibration free, you should be fine. Vibrate everything at 3g's and its a different story.
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Wikipedia says the surface pressure is 1.45 atm. That's about the pressure under 2 meters of water on earth. Not even enough to painfully pressure your ears.
I'm curious if you could withstand crushing inside the gas giants.
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44 minutes ago, KSK said:
So yeah - how do you run a galactic civilization when communications and travel times are limited to c?
You don't run it in the sense of having unified governance and trade relationships.
You can't even have real time communication. A generous mother world could send bulk data updating something like Wikipedia, with 3-D printable files and so on. So that colonies would get tech updates within their own light cone.
If we stop overpopulating, and come to an economy of overabundance, we may decide to stop expanding. I want to explore other stars, just because. But settlers going to frontiers are hoping for a better life. If it's absurd to expect a better life on a new colony than in a mature system, colonies may not grow.
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The premise of the question is what would you take to the moon, not what you could bring back. Maybe because Elon decides to launch a ton of anything not concrete. Or maybe you have a few kilos of extra capacity on each subsequent mission.
You can have sample return missions, but would you fill the sample container with something valuable for the first half of the trip?
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Human produce a lot of carbon waste. Maybe the most valuable thing to have piled on the moon (but super cheap on earth) is snacks.
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Space X famously launched a car on the test flight of falcon heavy, saying it was cooler than launching a block of concrete. Yeah concrete is not that valuable in space, but what about rice or something. Something future people might use.
It may happen again sometime soon. Assume that in the near future we test new landers on the moon, for which there are not enough super high value payloads ready. Or that the weight of high value equipment is such that we always have a few extra kilos of capacity we can take to the moon.
What would you take?
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Hydrogen can be used instead of Carbon as a reduction agent in steel making. It looks possible for Earth to switch over entirely to this technique in <100 years, if green policies are a priority.
https://www.weforum.org/agenda/2022/07/green-steel-emissions-net-zero/
I predict that magenetite Fe3O4 is abundant on the surface of the moon and mars. You need a big harrow or rake with powerful magnets on it, tow it behind the rover, collect kilos of magnetic black sand.
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18 hours ago, StrandedonEarth said:
If there was an omnidirectional radio transmitter at Proxima Centauri, how powerful would it have to be for us to detect it with current technology? Would it even be detectable over the radio noise from Proxima?
A 500kW transmitter 4 light years away would be received at about 10-28 watts/sq. meter.
They are trying now to detect aurora signals from exo-planets. AFAIK it hasn't happened yet. That's not how any exoplanets were discovered.
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Actually we probably need an antenna on the dark side of the moon just to scan the radio bands that are full of human signals. Our own signals bounced off the moon may be much louder than the signals we are looking for.
Beyond a hundred light years or it would be difficult to detect a civilization exactly like ourselves. And we stopped building >500kW radio transmitters for civilian use several decades ago.
The Analysis of Sea Levels.
in Science & Spaceflight
Posted · Edited by farmerben
The article doesn't give any details of what they found and why they think it is a 2.4 million year cycle, let alone how Mars accounts for it.
And Venus exerts much more gravitational influence on Earth than Mars does, plus has greater inclination.