a question.
Have you or anyone you know ever had _seasonal_ influenza?
where do you think it originates?
would you care to revise the portion of your comment I highlighted?
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a question.
Have you or anyone you know ever had _seasonal_ influenza?
where do you think it originates?
would you care to revise the portion of your comment I highlighted?
I would invite you to stop with the condescending posts and to start providing information to back your... implied assertions. Where do you believe that seasonal influenza originates? What is the significance of that fact with respect to interspecies viral transmission? If you have something to say, then make affirmative statements instead of playing wise sensei humoring himself with addle-minded inferiors. Part of my annoyance with your approach is that you haven't established any degree of scientific competency here because your posts to date have been either emotional appeals or just questions that suggest you know better.
The people on this thread are intelligent and educated, and you should treat them as such. You should know better, given the wisdom of your age.
If I do some googling, I find an article on a virology blog that asserts that a lowball estimate of mammalian viruses is around 320,000. That's just mammalian. Across all known specifies of vertebrates, invertebrates, plants, lichens, mushrooms and brown algae, the author guesstimates over 100 million viruses.
Another google finds an article on Trends in Microbiology that states that there are about 270 viruses known to infect humans.
So that's 270 / 100 million, or 0.00027% of viruses.
If we just consider the 320,000 mammalian viruses, that's 0.084% of viruses.
I would assert that's rare. I brought viruses up in the context of Mars because we don't have any idea what might be lurking on the planet - including the possibility that the planet is dead as a doornail from core to surface. The whole notion may be nothing. Or it may be another plague.
Every time a human contracts the flu, that virus comes from another human. It does not come from a different species
I stand by my post. We are talking about the number of species that can host pathogens that can cross to humans and infect them. Out of well over 1 million species of insects, reptiles, birds, amphibians, and mammals, a tiny tiny fraction of those species can host a virus/bacteria/fungus that can cross to a human and infect them.
Such an occurrence is rare.
Let’s get back to talking about colonizing Mars.
To date, all our robotic explorers have failed to find convincing evidence of life on Mars, now or in the past. But our explorations have been quite limited. If there is life on Mars right now it is likely microbial but it would be very different from life on Earth and therefore extremely unlikely to be a threat to us.
There is some interesting and well-informed speculation that Martian microbes, if they ever existed, could have come to Earth via meteorites. Read this and decide for yourself.
https://www.scientificamerican.com/article/from-mars-to-earth-in-a-m/
So, could life on Earth have been transmitted to Mars via a meteorite? I don’t think so. We are at the wrong end of the gravity well.
Since this forum is
"Mars and off planet colonization".
here is a link to a convention of the Mars Society including colonization for those interested
"Mars and off planet colonization".
here is a link to a convention of the Mars Society including colonization for those interested
Set at ASU Again, 2023 Mars Society Convention Promises to be a State-of-the-Art Event - The Mars Society
The Mars Society is pleased to announce that the 26th Annual International Mars Society Convention will be held once again on the picturesque campus of Arizona State University (ASU) in Tempe on Thursday-Sunday, October 5-8, 2023. As in previous years, the international conference will bring...
www.marssociety.org
As long as you shield the container from the sun, liquid hydrogen will stay liquid out there, so that's actually NOT that big of a problem. And the nuclear reactor can be super small and light, since your passenger space is already shielded against radiation, so the reactor doesn't need additional shielding.
There is much that is "simplified" in space that would normally be problems down on earth. I think it's a good example of first principles thinking.
My question was why the use of hydrogen as a mass-reaction fuel instead of heavier molecules like xenon (commonly used in ion thrusters)?
Hydrogen is notoriously difficult to contain. It tends to leak out of containers. OTOH, if there is indeed available water on Mars, then hydrogen can be procured there. You don't need to carry your return supply on the way out.
But shielding is still an issue because how to shield the astronauts from cosmic rays is not a solved problem.
Maybe they're using hydrogen because it could (maybe) be replaced on Mars.
I still think that sending people to Mars is a bad idea. Huge costs for small rewards. Mainly just bragging rights.
Isn't leaking only a problem for gaseous H2? I thought liquid H2 doesn't permeate through the container?
As for the cosmic ray shielding, that problem has to be solved regardless of the propulsion method. I was simply pointing out how nuclear propulsion doesn't have as many problems as initially thought.
I too think a Mars colony is a bad idea, but I am in favor of a space colony and diversifying our habitable space. Relying on earth alone is short-sighted.
When passing through seals and various pipes and conduits, yes. But long term storage in an insulated and actively-cooled tank is perfectly fine. The largest liquid hydrogen storage tank in the world is at Complex 39B, and it has both of those features. I couldn't find the power requirements for the tank (other than "$0.15 in electricity saves $1 in hydrogen", whatever that means), but there's a lot of power available in space.
Per the above, it's difficult to keep that hydrogen cold once you start moving it around. It warms, vaporizes, and then you've got gaseous hydrogen to contain.
It took me a while, but here's the answer from Wikipedia:
"At any particular temperature, lightweight propellant molecules carry just as much kinetic energy as heavier propellant molecules and therefore have more kinetic energy per unit mass. This makes low-molecular-mass propellants more effective than high-molecular-mass propellants."
For nuclear electric propulsion, the physics work such that for a fixed amount of energy, the greatest amount of outgoing momentum comes from a larger mass atom. So you go with Xenon because it's heavy. It is chosen over other materials with lower ionization energy or greater mass for practical reasons. Storage requirements, toxicity, interaction with the engine's materials, and so on.
Astronauts survive in space stations for months at a time. The air is 100% recycled, while the water is 98% with solar panels providing the energy to do all this. The cargo ships supply mostly food. Granted that still leaves quite a bit to solve, but I'm hopeful by nature. After all, the earth is also a closed ecosystem with nothing more than energy from the sun to drive everything.
Do you have an expected timeframe for solving the pertinent problems before we have a closed ecosystem that is independent of Earth?
They should try another Biosphere project. The last one didn't go so well maybe the second time around it will work.
www.theguardian.com
Eight go mad in Arizona: how a lockdown experiment went horribly wrong
In the 1990s, a troupe of hippies spent two years sealed inside a dome called Biosphere 2. They ended up starving and gasping for breath. As a new documentary Spaceship Earth tells their story, we meet the ‘biospherians’
www.theguardian.com
I recommend the Wikipedia article instead of the hyperbole-laced media article.
Whatever the solution to a colony (whether machines or an actual ecology), I'd say that building one on Earth is the right starting point. Then in orbit somewhere. Or on the Moon. And only then on Mars. Mars is obviously a unique environment, but keeping any self-sustaining and closed environment going would be a major step forward.
My preference for the first off-planet colony would be a large spinning station. Spin it up to Mars' gravity and put it where it would get about the same radiation as the surface of Mars. It's relatively close to Earth in case of needed resupply, equipment changes or emergency, and it's accessible as a tourist destination, which would help defray the cost. Apparently a radius of 70 meters would provide a comfortable 0.3g (220m radius for 1.0g). It would keep Starships busy for a long time.
The more I think about a colony on Mars, the farther out my time horizon goes. We don't even know what we don't know about doing such a thing.
I remember a show called Space 1999. As a kid I thought we would be living on the Moon when I would be an old man. Well I'm closer to being an old man and no colonies on the Moon
www.bing.com
space 1999 - Bing
Intelligent search from Bing makes it easier to quickly find what you’re looking for and rewards you.
Interesting proposal. Mars gravity is 0.38 Earth so the station needs a slightly larger radius to match it.
Not sure how you would match the cosmic radiation levels though. I found this article with a graph showing “CREME 96 calculations of average daily GCR charged particle flux (#/m2-sec-sr) vs. LET for near-Earth interplanetary (NEI), LEO 365km/51.6°, and LEO 365km/28.5° flight environments”
Also on the NASA website is information about surface radiation levels on Mars which is stated to average 210 “micrograys per day”.
This JPL article has a color coded map of the Martian surface showing how REM/day levels vary depending on elevation, with lower elevations receiving less radiation due to the blocking effect of the Martian atmosphere.
So a lot of information is available but because those sources are using different measurement units it’s not easy for me to correlate them.
I threw that in there, but the really important bit is ensuring that the dosage in the station interior is at acceptable levels. A separate task is to then figure out how to keep exposure on Mars down to that level. Experiments to discover how that could be done could be pursued via robotic missions that place, for example, small containers that represent a colony structure and interior, and measuring internal radiation. Pile soil over some, leave other exposed, and so on.
Note that the ISS astronauts receive 0.5 millisieverts per day, or 0.05 rem per day. That's 18.25 rem per year, which is comparable to the numbers listed on that Mars map. So I'd say we're there. Not that a large spinning station should be placed into low earth orbit. I haven't looked up cosmic radiation levels at higher orbits, such as geostationary. They may require considerable shielding.
Various space agencies have recommended a lifetime exposure of 600 millisieverts. That would be a bit more than 3 years at these radiation levels. So it would be desirable to get below the ISS radiation levels for long-term habitation. That would probably have to include the shuttles that take people to and from Mars. I won't get into the problems of shielding mass on a spinning station or an interplanetary shuttle.
To continue on this thought, there's a great Wikipedia article on how cosmic rays affect human health.
There is all sorts of quantitative information on that page, including the fact that 180 days on the way to Mars delivers as much cosmic radiation as 500 days on the surface of Mars. That shuttle is going to have to take shielding seriously.
Then there's this quote, which gets a much better sense of the impact of a full mission.
It continues to observe that the latest US guidelines (National Council on Radiation Protection and Measurements) recommend lifetime limits of 500 to 2000 millisieverts. So it looks like a trip to Mars is around the limit for radiation exposure regardless of whose guidelines are followed, and it's important that cosmic ray exposure is kept to a minimum at every step of the way, with exposure in interplanetary space being most critical - perhaps the most costly aspect of shielding.
It may come down to creating a cycler if we cannot create a fast enough ship. Some kind of stasis or deep sleep for the duration of the trip would also seem to keep ship masses greatly reduced. So many problems to solve.
I have seen discussions online about using the onboard water tanks as shielding.
Buckminster
Well-Known Member
Elon aspires to many lofty goals. The first two cargo missions to Mars were supposed to happen in 2022, followed by four more missions in 2024.
But let's consider the environmental impact implied by such a production rate.
Methane rockets produce 2.75 tons of carbon dioxide for each ton of methane they burn. If SpaceX sends fleets to Mars every two years, then at 300 ships per year, that's 600 ships per fleet. Each fleet must be fueled for the trip, and let's call it 9 refueling launches per ship. That's 6000 launches per fleet. Each launch requires roughly 1100 tons of methane, for a grand total of 6.6 million tons of methane. That generates 18 million tons of CO2, or about 2 million cars' annual exhaust for two years. This ignores any environmental impact from producing the ships and propellants.
So it looks like Elon created Tesla as a carbon offset for SpaceX.
But I do wonder how the world will react to a company generating that much CO2. It won't matter that other sources of CO2 are larger because whatever they are, they're already entrenched in our society and our economy to provide some benefit to somebody. How will SpaceX justify injecting that much CO2 into Earth's atmosphere when the only benefit will be to people on Mars? I'm not sure that "Making humanity multiplanetary" is going to resonate with many people on Earth. This may end up being the largest-scale NIMBY event in human history.
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