It would be neat if it were a steampunk-style civilization traveling around their atmosphere in helium airships. But probably just helium escaping from rocks...
Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
31–40 of 59 posts
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#32Is it wrong that I was hoping for something along the lines of: https://www.scientificamerican.com/article/how-would-we-know... except where they are noting how helium is being allowed to escape and not being captured as was previously done by the now shut down U.S. National Helium Reserve.
Am I missing something or does that article only contain the back story and nothing actually noteworthy?
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#33Earlier quoted context omitted.
the catalog says 6.38x mass in one place and 5.6x mass in another they must be able to calculate mass from orbital physics? so you'd need a rocket 6x the size of SaturnV or whatever they are using for Artemis to escape it and most of that rocket is to lift the weight of the fuel for said rocket so it might be physically impossible to build such a creature at current level of tech (might be yet another angle to "why n…
√(G × mass÷radius) [escape velocity] = v_e × ln(m_0 ÷ m_f) [Tsiolkovsky] Impossible to tell how much extra mass you need but it's exponential . Adding a unit of v_e [effective exhaust velocity] to escape velocity means you need 2.717 times as much fuel in an ideal rocket. Earth escape velocity is 11000m/s ignoring atmosphere (which is not ignorable). If the new planet is 6x mass and 2x radius then √3 times escape vel…
Perhaps that's why they're attempting to build a starship out of helium.
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#34Earlier quoted context omitted.
√(G × mass÷radius) [escape velocity] = v_e × ln(m_0 ÷ m_f) [Tsiolkovsky] Impossible to tell how much extra mass you need but it's exponential . Adding a unit of v_e [effective exhaust velocity] to escape velocity means you need 2.717 times as much fuel in an ideal rocket. Earth escape velocity is 11000m/s ignoring atmosphere (which is not ignorable). If the new planet is 6x mass and 2x radius then √3 times escape vel…
From the archives ... How much bigger could Earth be before rockets wouldn't work? https://space.stackexchange.com/q/14383 Feb 3, 2024 https://news.ycombinator.com/item?id=39243303 And related... https://worldbuilding.stackexchange.com/questions/178131/wha... https://physics.stackexchange.com/questions/117347/when-a-pl...
Man I love this.
> Up above 10g, something really interesting happens that is kind of a theoretical limit. The mass of the rocket reaches a measurable fraction of the mass of the entire planet it's launching from.
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#35Earlier quoted context omitted.
It is the four layers of resources, each one is smaller than the next. 1. What is the total theoretical resource? 2. How much of it do we actually now the location of 3. How much is technically recoverable? 4. And most importantly, how much is economically viable? The last one is really the crux of the problem nowadays, there is a lot of helium but most of it just isn't in a high enough quantity to make the investmen…
> 4. And most importantly, how much is economically viable? But literally the least important factor beyond “should we have started yesterday”. The amount of waste humanity has perpetuated in just the last 100 years because something wasn’t “economically viable” this fiscal quarter makes my head hurt.
Doing economically inviable things is waste. It's pumping resources into something worth less than the sum of its inputs.
Apropos of nothing, see one trillion dollars into datacenters.
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#36Earlier quoted context omitted.
There will come a point when the price hits high enough to justify the cost but that also means higher costs to the end user. This makes me wonder if it'd be worthwhile starting a company to capture it now, and just stockpile it until it's rare enough to be able to use my stockpile to control the price. The DeBeers diamonds playbook applied to helium, or maybe the Peter Thiel build-a-monopoly-to-win approach.
That's where the government reguli could step in. It wasn't economically viable to capture natural gas so it's just flared off, but if the government fines oil companies for flaring off the natural gas, suddenly it's economically viable to capture it instead of wasting it.
> if the government fines oil companies for flaring off the natural gas, suddenly it's economically viable to capture it instead of wasting it.
If the government fines individuals for not digging holes in their back garden every day then suddenly it's economically viable to dig holes in your back garden every day, but it doesn't mean it's overall productive.
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#37Earlier quoted context omitted.
NASA and Starlink have already been using ion drives with 10x ISP of chemical rocket engines. Using such drives a 3 stage with existing nuclear reactors as energy source can get to 150-200 km/s. While it haven't been built yet, nothing seems to prevent ion drive even with 100x ISP of chemical rocket. That means we can get 1000-2000 km/s (acceleration with existing reactors would take about 100 years) and get to the c…
The problem is radiation. Empty space is not really empty, there are stray atoms floating around. Very scattered, but at a high impact momentum penetrate the ship ionizing anything in their way, and making the ship itself radioactive. Not even talking about stray high-energy particles from distant supernovas and magnetars -- those irradiate ship regardless of its speed.
If "closest star" is Proxima Centauri, we're talking 4.5 light-years. Getting there in 1000 years means an average speed of 0.45% of the speed of light. At that speed less than 0.01 cm of titanium is enough shielding to keep the radiation out according to figure 1c) in my source below. Which makes sense because because this is ~10% of the speed of "normal" alpha radiation which is stopped by just your skin.
"Radiation Hazard of Relativistic Interstellar Flight" by Oleg Semyonov: https://arxiv.org/abs/physics/0610030 via Project Rho: https://projectrho.com/public_html/rocket/slowerlight3.php
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#38Is it wrong that I was hoping for something along the lines of: https://www.scientificamerican.com/article/how-would-we-know... except where they are noting how helium is being allowed to escape and not being captured as was previously done by the now shut down U.S. National Helium Reserve.
Am I missing something or does that article only contain the back story and nothing actually noteworthy?
It contains the story of how Carl Sagan convinced the Voyager crew to turn its sensors towards earth so as to see if life could be detected using its quite minimal sensor suite --- I thought it had a link to the original published paper.
The fate of the Strategic Helium Reserve is a different issue and there are many articles and op. ed. pieces on it --- the Wikipedia article should cover this:
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#39Earlier quoted context omitted.
> 4. And most importantly, how much is economically viable? But literally the least important factor beyond “should we have started yesterday”. The amount of waste humanity has perpetuated in just the last 100 years because something wasn’t “economically viable” this fiscal quarter makes my head hurt.
Doing economically inviable things is waste. It's pumping resources into something worth less than the sum of its inputs. Apropos of nothing, see one trillion dollars into datacenters.
That is exactly it - how do we define economically inviable? There are many answers, very different.
Re: Helium escaping from atmosphere of nearby rocky exoplanet in a habitable zone
#40Earlier quoted context omitted.
When you're done with it can I borrow your particle collider capable of mass synthesis of helium
Alpha particles are essentially Helium, so by breeding large amounts of highly active alpha emitters you can produce Helium much more effectively than by fusion.
Probably that's what they did at the rocky exoplanet. How much radiation do they need down there for it to be measurable as helium in the atmosphere?