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General Science / Re: The journey to the red planet: does humanity need Mars colonisation?

« on: 09/07/2021 10:06:13 »

It would be much better to invest in technology and projects that can preserve Earth. I have already mentioned on this forum but in another thread  satellite technology that can track rare species of animals to prevent them from being killed by poachers. Also, there are special satellites that can observe coral reefs in order to help scientists to save it.

Of course preserving earth is mandatory, since it's the only place in the universe which we know for sure contains and supports existing conscious entities, at least for now. But we shouldn't restrict ourselves to become too dependent on it. We know that the universe is much larger than earth, and it's mostly unexplored. Terraforming other planets is just a stepping stone to expand consciousness further, even beyond our solar system. It's extremely unlikely to achieve the universal terminal goal if we restrict ourselves to a tiny spot so insignificant in size, compared to observable universe.

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General Science / Re: The journey to the red planet: does humanity need Mars colonisation?

« on: 07/07/2021 02:03:22 »

Someone has thought about it.

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Physics, Astronomy & Cosmology / Re: Can we turn waste plastic into rocket fuel?

« on: 02/06/2021 02:35:17 »

Also, there are many types of plastic such as PP, nylon, ABS, PVC etc. so it will largely depend on the type of plastic you use for the fuel.

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Physics, Astronomy & Cosmology / Re: Can we turn waste plastic into rocket fuel?

« on: 01/04/2021 22:14:24 »

Have you heard about the new special type of rocket fuel that is made from plastic waste? One company uses particular kinds of plastic to remake them in rocket fuel

Plastic is derived from oil, which contains a lot of potential chemical energy. This energy is used directly to fuel vehicles such as automobiles, ships and aircraft.

And plastic is derived from oil.  So it could be used as fuel - especially  in rockets, which are much simpler than cars.

Cars need complicated internal-combustion engines. With pistons, cylinders, crankshafts, gears and other mechanical moving parts.

Whereas rockets only need fuel to burn.  So couldn't a fuel made of oil-derived plastic, supply that need?

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Physics, Astronomy & Cosmology / Re: Do you believe in possibility of life in other galaxies?

« on: 23/03/2021 17:36:28 »

But still, there is a possibility that in some galaxy and in some exoplanet there are some forms of life or this planet can be similar to Earth in conditions for living for humans.

By the logic spelled out above, it is essentially a certainty, yes.
The beings living there will probably not be particularly human-like, but perhaps the chemistry will be somewhat similar such that we might be able to eat the local vegetables.

OK, so such a place likely exists. So what? We can't sense it.

If we only consider planets within our visible universe, less than 2.5% of them are within the Hubble radius, and far less than 1% of those are within 2 billion light years distance. So suppose somebody a mere couple billion light years away has fantastic sensing technology and notices Earth has the right atmosphere and environment for them.  They also have ships that can move at nearly light speed.  By the time they get here (4 G-year minimum), the Earth will be a charred smoking husk, certainly not the friendly environment they sensed from afar. Such environments are temporary. Maybe some life here has evolved to a hot dry planet, but it won't be what the visitors came here for.
So the existence of some planet habitable to us without modification is of little interest to humans even if we could somehow know where it is. It has to be reasonably close by.

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Physics, Astronomy & Cosmology / Re: Do you believe in possibility of life in other galaxies?

« on: 23/03/2021 13:52:41 »

With over a hundred billion galaxies in the universe.

There are considerably more than that, given the fact that there's no known limit to the size of the universe. If there is a finite chance of life in a given galaxy, then there being life elsewhere is a certainty.

some scientists claim that they have already found some exoplanets that can be like Earth.

Their idea of 'like Earth' is that it has gravity within 50% of ours and perhaps a likely temperature that is within 100°C of ours, each being one of the few things that can be measured of an exoplanet from our distance.

If they mean one that has free oxygen, that doesn't happen naturally. It only happens if there is life already there, and improbably similar to our kind of life. I notice most people that ponder this question (including many scientists) only consider Earth-like carbon/water based life. There are far more possibilities, but most so alien they are hard to conceive without finding (or even recognizing) it first.

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Physics, Astronomy & Cosmology / Re: Types of propulsion system

« on: 19/03/2021 07:25:40 »

Surely, nuclear fusion would be the ideal method of propulsion (especially if it could scoop up fuel and reaction mass from the solar wind).
- But we can't get controlled fusion to work on Earth
- Let alone a motor small enough and light enough to fit on a spacecraft.
https://en.wikipedia.org/wiki/Fusion_rocket

A few are working with nuclear power generation and ionized gas propulsion but they are very rare

Dawn spacecraft to the asteroid belt uses ion propulsion, but it gets the power from the Sun (there is still a fair amount of Sunlight at the asteroid belt).
- Spacecraft powered by nuclear energy tend to use thermo-electric generators (TEG), which are not very efficient (but they have no moving parts, which is a bonus in space)
- TEG can't generate the 10 kiloWatts or so required for an ion drive
- For those power levels, you would need a "critical" nuclear reactor, which is a lot more complex.

The Perseverance rover on Mars has a large TEG, which generates just 0.1 kiloWatts
https://en.wikipedia.org/wiki/Perseverance_(rover)#Design

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Physics, Astronomy & Cosmology / Re: What do we do about the orbiting space junk?

« on: 26/02/2021 22:53:43 »

The quickest way to get rid of the orbiting satellites, would be to start a global nuclear war.

This just reduces thousands of satellites in controlled orbits to millions of fragments in uncontrolled orbits.  It would multiply the hazard a thousandfold.
On the plus side, said war would essentially remove the problem since no new satellites would go up and all the new junk up there won't bother anybody anymore.

In such a war the combatant countries, America, Russia and China, would for military purposes, shoot down all the satellites.

You can't shoot one down. At best you can blow it to bits, which just gets you a lot of bits. It's not like an airplane where the bits all fall to the ground when you 'shoot it down'.  A few chunks will be in orbits that now intersect Earth, but most will not.

But these fragments would soon decay from orbit, and burn up as harmless meteors.  Leaving the sky clean!

That would require their kinetic energy to go somewhere. How does that work? If it did, there wouldn't be a significant space junk problem in the first place.
Yes, there are tiny molecules of gas up there and the friction with them will bring down the lower satellites after many centuries, but most orbits are too high to wait for this process.

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Physics, Astronomy & Cosmology / Re: Could there be life on other planets?

« on: 25/02/2021 21:11:13 »

Yes, I think it's one of the main purposes of a universe. To create life. The thread is old but so is the question. Darwin had this idea of it starting in pools bathed in sunlight. It seems he might be correct.

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Physics, Astronomy & Cosmology / Re: What is the point of the UK space weather forecasting satellite?

« on: 23/02/2021 14:43:42 »

It will be interesting to see how you can forecast space weather since nearly all of it comes from one source, so you have to stare at the sun and correlate showers of particles with electromagnetic signals that arrived a few minutes earlier, then predict where the charged particles are going to interact with the magnetosphere.

Quite different from terrestrial weather, which has a relatively constant heat input to an inherently chaotic system, whereas the sun is a chaotic source of  high energy radiations of all sorts which interact with a well-mapped magnetic field.

If predicting solar "weather " was easy, we wouldn't have called it "weather".

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Physics, Astronomy & Cosmology / Re: What is the point of the UK space weather forecasting satellite?

« on: 22/02/2021 20:28:56 »

a well-mapped magnetic field.

The problem with this well-mapped field is that when it reaches out into space, it gets pushed around by eddies and outbursts in the Solar wind plasma, pushing it into poorly understood shapes, and maybe breaking off pieces of it.

UK is about to launch it`s own space weather forecasting satellite which is called SWIMMR

If you check the following link, it appears that SWIMMR is a multi-faceted programme, many parts of which aren't on a satellite.
- One part is looking looking at how the upper atmosphere expands when it is struck by a solar outburst. The ISS is in Low-Earth Orbit (LEO), and normally drops about 100m per day due to atmospheric drag. But due to sudden solar activity, on one occasion it dropped by many kilometers in one day, and they had to give it an immediate altitude boost.

site:https://gtr.ukri.org/ SWIMMR

What is your expectation from this program?

The UK has an established space industry, often producing specialized instruments as payload for other satellites.
- It's not yet clear to what extent the UK will remain as part of ESA, and able to "piggy-back" on ESA launches
- So I guess it is worthwhile to gain experience managing development of a whole satellite

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Physics, Astronomy & Cosmology / Re: What do we do about the orbiting space junk?

« on: 18/02/2021 18:54:27 »

Although I appreciate the environmental issues raised by previous posters on this topic, I do quite like the thought that we've put all those satellites, and even bits of junk, into space.

It gives me a feeling of pride, in our human accomplishment.  Does anyone else feel the same?  I mean, looking up at the starry night sky, and seeing one of our artificial satellites travel quietly and routinely among the stars, and think:

"We did that"!

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Physics, Astronomy & Cosmology / Re: What do we do about the orbiting space junk?

« on: 18/02/2021 00:27:32 »

I would look at it in a different way.....and propose a proof of concept experiment.  We track the big pieces with radar.  I would put a UV or x-ray laser in orbit, and see if we could ionize the junk object, and see what affect it had on it's orbit.    I would not rely on any simulation or opinions.  If that alone doesn't work, a magnetic field can decelerate the charged object. Space robot cowboys.

But even if we could remove the large junk, there is still a great problem, and that is all the "speck" junk.  Perhaps a high powered x-ray emitter, to ionize, flying in a grid search fashion, might charge the specks.

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Physics, Astronomy & Cosmology / Re: What do we do about the orbiting space junk?

« on: 11/02/2021 12:48:03 »

The problem is not about it burning in the atmosphere since if it was in the atmosphere, it wouldn't be space junk. Thus very little of space junk poses a danger to Earth population since most of Earth's population is in said atmosphere where the space junk isn't. Some big pieces de-orbiting (Skylab for instance, also the Columbia) do pose a danger, but humans are remarkably small targets to hit, and the general influx of normal meteors poses a much larger threat, and even then it is incredible news when one of them actually manages to injure somebody.

So the problem is the threat posed by the stuff to non-junk satellites.  There is almost nothing one can do about it unless we can invent some sort of tangential tractor beam, which is pure science fiction. The idea is to get these objects to actually hit the atmosphere instead of continuously missing it.

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General Science / Re: The journey to the red planet: does humanity need Mars colonisation?

« on: 05/02/2021 14:48:56 »

A thing we have to consider too, if we wanna make a living on mars, would also be the irreversible consequences on our human biology. We can mimic a lot in closed facilities: atmosphere, ecosystems, probably even social live if we manage to get enough people there - but there's one thing we can't mimic and that's gravity. Mars only has a third of earth's gravity. Great for earthborns on mars probably, not so much for marsborns on earth. If you were born on mars or even spend a lot of time there, a return to earth might be fatal for you.

All I wanna say is, that if we - humans - colonize mars, our paths WILL split. An earth human can live on mars, but a mars human probably can't live on earth due to its high gravity. A great motivational factor if you are already there, but if you're still undecided, you have to keep in mind, that a stay on mars for at least ten years might be a one-way trip. No return, no familiy visits.

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Physics, Astronomy & Cosmology / Re: Sun-synchronous orbit spacecrafts

« on: 05/02/2021 13:23:09 »

There are actually none.  We currently lack the technology to deliver sufficient delta-V to put an object into a sun-synchronous orbit (an orbit that hangs over a fixed point on the surface of the sun).  Such an orbit would seem to serve no purpose.

Perhaps you mean something else by the term.

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General Science / Re: The journey to the red planet: does humanity need Mars colonisation?

« on: 29/01/2021 14:36:42 »

Average atmospheric pressure on Mars is 7 millibars, compared to 1,013 millibars on Earth. But the Martian atmosphere is almost entirely carbon dioxide. Compared with 400 parts per million on earth, giving a partial pressure of 0.4 mb, this is a factor of 30 richer for plant growth. So we need to import (or find) and conserve water, but there should be no problem growing food and thus generating oxygen in a suitable greenhouse. If we can find a source of hydrogen, even if it requires substantial amounts of electricity to dissociate a hydride mineral, we can then generate water. 

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General Science / Re: The journey to the red planet: does humanity need Mars colonisation?

« on: 28/01/2021 21:35:25 »

Some of us might be interested in what Martian men would be like.  They'd have evolved in a low-gravity environment.  Which allowed them to grow appendages of extraordinary dimensions, by terrestrial standards.

Isn't that a fascinating subject for speculation?

They also have to live in a dry environment with low pressure, low oxygen and high concentration of CO2 atmosphere. If we find Martian lifeforms, they are most likely microscopic.

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Technology / Re: Technology can be used to measure the extent of desertification

« on: 28/01/2021 20:25:13 »

Could you ever thought that in order to fix that stuff scientists start to use satellite technology which helps scientists observe the land?

Observation is often easier than manipulation.
- You can observe the melting ice pack of Greenland via remote sensing, without using much energy (the observation is solar-powered, and can be observed with a telescope only 15 cm across)
- The melting is also solar-powered, but to control the solar power reaching Earth, you need a satellite perhaps 15,000 km across...
- The same satellite could perhaps reduce temperatures in the desert, which might encourage rain. Restoring soils takes a material input...

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General Science / Re: The journey to the red planet: does humanity need Mars colonisation?

« on: 26/01/2021 21:28:13 »

the kind that are reactionless, and simply convert matter into force. yes it's easier to do than you think