Interplanetary travel, Arctic sea ice

[cosmo777]

I'm a software developer, no formal astro-physics education, but would like to pose some questions/hypotheticals regarding interplanetary travel, and/or dynamic positioning of Earth orbiting objects using extraterrestrial fuel sources.

1. Asteroid-based hitch-hiking to other planets.

Hypothetically, could an Earth-launched spacecraft a) attach to a small asteroid (to be identified in advance), b) use its own rocket fuel to alter the orbit of the asteroid such that it would be drawn into a steeper solar orbit, resulting in a slingshot trajectory which would carry it past a target planet, where it would disconnect from the asteroid, and go into orbit over the target planet? In theory, converting the potential energy of the asteroid's current stable solar orbit, into a free-ride to a distant planet using less on-board propellant than it would otherwise use going direct?

2. Restoring multi-year sea-ice in the Arctic.

At the moment (March, 2018) the Arctic ice-cap has (over four decades or so) lost roughly 80% of the multi-year sea-ice, which determines the annual minimum albedo of the polar cryosphere. During periods when little or no multi-year ice is restored (such as we're in now), this locks in an increase in the amount of solar energy which is absorbed by Arctic seas & winds-aloft (rather than being reflected back into space), which in-turn raises water temperatures -- causing primordially sequestered shallow sea-bed methane-hydrates to melt, which in-turn may accelerate summer snow-melt on the Greenland ice-sheet, and cause anaerobic methane generation on Arctic land-masses due to warming of perma-frost.

Since methane is a very potent greenhouse gas (greater than CO2) this could (theoretically) lead to a feed-back loop, resulting in a catastrophic release of methane into our atmosphere. Question:

Is there a plausible way to deploy what amounts to an orbiting 'solar-shade', permanently positioned to cast a shadow over the Arctic, thereby enabling the restoration of some of the multi-year sea-ice which has been lost?

Assuming such a structure could even be assembled, I believe it would require daily re-positioning, hence a design which would benefit from either the use of solar-wind, or some other extraterrestrial fuel source.

It seems to me, while we cannot be certain current warming trends will continue, and/or that primordial methane-hydrates will actually make it into the atmosphere, climate scientists estimate the potential amount of sequestered methane release at 1000-5000 gigatons in the Arctic alone, compared to an accumulated total of 400-500 gigatons of carbon emissions over the last 200-300 years from anthropogenic sources.

Given the remarkable advances in recoverable booster-rocket technology we're witnessing from SpaceX and others, I would argue that in terms of our priorities for applying those new technologies: containing a potentially existential threat to our biosphere here on Earth, should take precedence over landing humans on Mars. At a minimum, I would hope the scientific community in general (and the United States in particular) should act immediately to quantify the threat posed by Arctic methane releases which are already under way.

Hoping this forum is an appropriate one for these subjects.

 

[Bandersnatch]

Hi, and welcome to PF!

1. Asteroid-based hitch-hiking to other planets.

You don't actually gain anything from doing that. You don't gain any energy from riding an asteroid and then detaching from it, while you do need to expand (a lot!) of energy to change its orbit. You're better off riding your rocket alone.

2. Restoring multi-year sea-ice in the Arctic.

There are some ideas like that thrown around. Google for the key word 'Geoengineering' - just read what legitimate (i.e. academic-related) sites tell you, as e.g. the second hit I get from Google is a crackpot site.
Start e.g. here:
http://www.geoengineering.ox.ac.uk/what-is-geoengineering/what-is-geoengineering/

edit: grammar

 

[phinds]

Your title and your post are not about the same thing

 

[Bandersnatch]

Your title and your post are not about the same thing

It was moved from another thread. Blame the mentors.

 

[phinds]

It was moved from another thread. Blame the mentors.

OK. BAD mentors !

 

[mfb]

I adjusted the title.

2. Restoring multi-year sea-ice in the Arctic.

There are no orbits where things would constantly be above the Arctic as seen from the Sun.
Earth is huge. The largest solar sail (could double as sunshade) ever deployed was a square of just 14m x 14m. You need 5000 of them to cover a single square kilometer, and 6 billion to cover 1% of the surface of Earth as seen from the Sun (ignoring orbits here).

 

[phinds]

I adjusted the title.
There are no orbits where things would constantly be above the Arctic as seen from the Sun.
Earth is huge. The largest solar sail (could double as sunshade) ever deployed was a square of just 14m x 14m. You need 5000 of them to cover a single square kilometer, and 5 billion to cover 1% of the surface of Earth as seen from the Sun (ignoring orbits here).

See, there you go again, bringing facts into the discussion. Spoilsport

 

[cosmo777]

I adjusted the title.
There are no orbits where things would constantly be above the Arctic as seen from the Sun.
Earth is huge. The largest solar sail (could double as sunshade) ever deployed was a square of just 14m x 14m. You need 5000 of them to cover a single square kilometer, and 6 billion to cover 1% of the surface of Earth as seen from the Sun (ignoring orbits here).

Thanks for the prompt reply. (I figured it was a longshot.) I do believe the scientific community needs to take the situation in the Arctic seriously, at least by carefully monitoring how much primordial methane is entering the water-column. Last I checked, it appears to be remaining there (dissolved perhaps). However, what happens if it reaches a saturation point? (If you search on 'Peter Waddhams methane arctic' on YouTube, you'll find authoritative discussions on the status of this one.

Perhaps an interesting segue for this topic: Could a fleet of trawlers extract the methane from the Arctic sea-water, and either use it directly, or find a way to convert it into hydrogen? There's a startup company here in the Pacific Northwest: www.inentec.com which is pioneering the use of 'plasma-gasification' to convert garbage/refuse into hydrogen (with CO as byproduct). Of course burning the methane itself is an option, but you still need to find a way to re-sequester the CO2. One way or another, most of the commentary I've seen on this subject suggests that large releases of primordially sequestered methane into the atmosphere could have grave consequences.

Thanks again for considering these ideas. The underlying problems need to be addressed by people who fully understand the science.

 

[stefan r]

Could a fleet of trawlers extract the methane from the Arctic sea-water, ...One way or another, most of the commentary I've seen on this subject suggests that large releases of primordially sequestered methane into the atmosphere could have grave consequences.

Yes, large fleet of trawlers could do severe damage to the ocean. Yes, you can actually extract most things from sea water. People have published plans to extract gold and uranium. It is highly unlikely that you would extract enough energy from the methane to power your trawlers. Building the system would also require large energy expenditures.

Fracking is a major source of methane. Fracking is also a major source of methane emission. Off shore operations are much more complicated. It is very likely that the fraction of lost methane would be higher. Fracking close to the surface would be especially prone to leakage. The clatharates that are close to the surface are the most likely to be destabilized by warm ocean currents.

Bio-gas plants can produce methane. There are several thousand in operation in Germany. It is one of the better methods of reducing greenhouse gas emissions. Bio-gas is a known technology that Germans would be thrilled to explain.

Is there a plausible way to deploy what amounts to an orbiting 'solar-shade', permanently positioned to cast a shadow over the Arctic, thereby enabling the restoration of some of the multi-year sea-ice which has been lost?

A solar shade does not need to be positioned over the arctic. Ocean temperatures effect the amount of ice that accumulates. Tropical glaciers are important too.

...
There are no orbits where things would constantly be above the Arctic as seen from the Sun.
Earth is huge. The largest solar sail (could double as sunshade) ever deployed was a square of just 14m x 14m. You need 5000 of them to cover a single square kilometer, and 6 billion to cover 1% of the surface of Earth as seen from the Sun (ignoring orbits here).

Center below(sunward) Lagrange point 1. Place 2,450 million of them over the arctic and antarctic. Make the other 100 million tethers. Tilting some of the shades 45° cuts the light blocked by 29% but could give you a lot of thrust so tethers would not need to be very strong. A fancier version would block the infrared but let red and blue light through for plant growth.

If we are limited to current rocket technology and manufacturing practice then deploying the sun shades would add a lot of greenhouse gasses. You can loft hydrogen filled balloons over the arctic without using a rocket.

Deploying 6 billion solar panels on roof tops should be much easier. Just because something can be done within the laws of physics does not mean that it is a good idea.

 

[mfb]

Center below(sunward) Lagrange point 1. Place 2,450 million of them over the arctic and antarctic. Make the other 100 million tethers. Tilting some of the shades 45° cuts the light blocked by 29% but could give you a lot of thrust so tethers would not need to be very strong. A fancier version would block the infrared but let red and blue light through for plant growth.

Whatever you put close to L1 has a half shadow larger than Earth. Shadowing all of Earth a bit is the only reasonable option there. Things "below"/"above" are above some point that is typically not over the Arctic/Antarctic due to axial tilt, and they are attracted towards L1. Shift them sidewards to fix it and you get torque. It is not that easy. Halo orbits around L1 to shadow all of Earth would work, but you are still left with ridiculous areas to cover.

 

[sophiecentaur]

I keep telling people to paint all the desert regions white (roofs and roads too). That would be by far the cheapest solution to blocking the Sun's rays and it wouldn't matter if the painters 'missed a bit'.

 

[mfb]

And the first time a bit of wind comes the paint gets covered by darker dust.
Meanwhile heating costs go up for houses and driving could become more dangerous.

If it would be that easy, we would do it.

 

[stefan r]

I keep telling people to paint all the desert regions ...

And exterminate how many species?

..a bit of wind comes the paint gets covered ...

Or goes airborne and spreads the toxic mess. Chokes the only streams near the desert.

There have been proposals to use trimethyl aluminum as aviation fuel. The alumina particles in chemtrails will block sunlight. You could also use H2S (rotten egg odor) to add sulfates in the upper atmosphere. Sulfates reflect UV out and do not block much infra-red.

Ways to disrupt the climate in the Arctic include a dam across the Bering straights, arctic heat exchangers, spraying liquid salt water over the top of the ice sheet in winter. In the tropics you can spray salt water from sailboat masts to seed clouds. They even invented a rotating spiral sail for this purpose.

There are also proposals to dump rust in the oceans and create red tides and algae blooms. The dead diatoms carry some carbon to the deeper ocean.

 

[JMz]

I think the relevant science here is not physics but sociology.

 

[sophiecentaur]

And exterminate how many species?

If we don't do something, there will be extinctions anyway.

And the first time a bit of wind comes the paint gets covered by darker dust.
Meanwhile heating costs go up for houses and driving could become more dangerous.

If it would be that easy, we would do it.

Exposed rocks have hardly changed for thousands of years and non-toxic paint would obviously be chosen.
That objection could apply to any measure that's taken. If the painting system is effective enough to increase the cost of house heating and put ice on roads then clearly it would need less paint. Changing back to the status quo would be much easier with an Earth based solution.

I think the relevant science here is not physics but sociology.

No doubt about that. Strange that wearing thicker jumpers and walking more are such unattractive measures.

 

[JMz]

No doubt about that. Strange that wearing thicker jumpers and walking more are such unattractive measures.

Not strange if you're a billionaire who would lose a great deal of money from abandoning coal and can afford lobbying & public advertising to make all alternatives seem as unattractive as possible.

 

[stefan r]

...Exposed rocks have hardly changed for thousands of years and non-toxic paint would obviously be chosen...

Rocks exposed by retreating glaciers do not have much living on them yet. The topical glaciers get a lot of sunlight.

If we don't do something, there will be extinctions anyway...

Do you prefer trimethylaluminum or hydrogen sulfide? We can do a bit of both. There is also the cheap and lazy option of not removing sulfur from petroleum. The link claims that not using ultra low sulfer jet fuel kills about 80 people per year in the United States.

Not strange if you're a billionaire who would lose a great deal of money from abandoning coal and can afford lobbying & public advertising to make all alternatives seem as unattractive as possible.

Billionaires can make a lot of money selling high efficiency infrastructure. There is a lot of lobbying for lower electricity rates. If we were serious about reducing CO₂ emissions we could simply tell electricity companies to make profits. Allow stockholders to sue for lost dividends.

The low hanging fruit is vegan (not Alpha Lyrae). Dairy farmers are not billionaires. Choice of food is something you normally have complete control over. You can decide to ignore advertising.

 

[sophiecentaur]

we could simply tell electricity companies to make profits.

Raising taxes on fuel would be better value for us, rather than the wealthy.
Politicians have a serious problem (ahhh). The solution to all this is to Consume Less but what sort of an economy would that lead to, when growth is paramount.

 

[stefan r]

...growth is paramount.

That statement is not physicsy. We can measure biodiversity, top soil, biochemical oxygen demand, water table levels, ice coverage.

 

[sophiecentaur]

That statement is not physicsy. We can measure biodiversity, top soil, biochemical oxygen demand, water table levels, ice coverage.

Not "physicsy", perhaps; it sociological / economy driven. Eliminating the cause of a problem is surely better than repairing the results. My mother used (annoyingly) to say "Prevention is better than Cure.".

 

[mfb]

Exposed rocks have hardly changed for thousands of years and non-toxic paint would obviously be chosen.

And how many exposed rocks do you find and how efficient are you if you only paint these?

That objection could apply to any measure that's taken. If the painting system is effective enough to increase the cost of house heating and put ice on roads then clearly it would need less paint. Changing back to the status quo would be much easier with an Earth based solution.

You can't argue that it doesn't have a relevant impact and that it will have a relevant impact at the same time. That doesn't make sense.
The fraction of the surface covered by houses (and roads) is tiny. If you change something on houses you affect the houses much more than the overall climate.

 

[sophiecentaur]

And how many exposed rocks do you find and how efficient are you if you only paint these?

The exposed rocks would be only a small contributor. Large stones and pebbles would also keep their paint and, in fact, the degradation of most surfaces would only be partial. I realize that a space based solution is attractive but it is easy to ignore the cost and also the fact that we'd be stuck with it, even if there were unexpected results. I never suggested that house roofs would be particularly significant. It would just be a step in the right direction (in the appropriate parts of the world. White roads would only be an ice danger in cold regions. It would be no bad thing if drivers actually went slower and saved fuel that way.
It's a shame that low tech solutions don't appeal to technophiles. There are a lot of very elegant but simple solutions out there.

 

[mfb]

but it is easy to ignore the cost

Where is a cost estimate for what you proposed?

I never suggested that house roofs would be particularly significant.

You at least implicitly assumed their effect would outweigh their downsides. Without quantifying either.

White roads would only be an ice danger in cold regions.

Who said ice would be the only issue?

There are a lot of very elegant but simple solutions out there.

But cost estimates are rare.

You can propose a lot, but without a cost estimate all that is not useful.

 

[sophiecentaur]

Where is a cost estimate for what you proposed?

It is not unreasonable to say that the area of any space structure would be significantly more than an Earth structure and that putting more material up there would cost more than putting less material on the surface. Do you really need a detailed costing? (Agreed - the space structure could well last longer without maintenance.

Who said ice would be the only issue?

Can you suggest any other real issues with white coloured roads?

 

[mfb]

It is not unreasonable to say

It is.
As you do not have any reference for your proposals, I suggest to not continue this discussion, as this would violate the forum rules.

 

[sophiecentaur]

It is.
As you do not have any reference for your proposals, I suggest to not continue this discussion, as this would violate the forum rules.

How about this?
Cost per kg of space launch to geostationary orbit. About $20k.
Cost of international postage for 1kg parcel from UK to Ethiopia . About $60
Aerial application(manual). About $6k per square mile. (Much less with unmanned system)
No great surprises there. Do you still think there's no juice in that lemon?
And the ground application could start tomorrow if we wanted.

 

[mfb]

How about this?
Cost per kg of space launch to geostationary orbit. About $20k.
Cost of international postage for 1kg parcel from UK to Ethiopia . About $60
Aerial application(manual). About $6k per square mile. (Much less with unmanned system)
No great surprises there. Do you still think there's no juice in that lemon?
And the ground application could start tomorrow if we wanted.

None of these things estimate the cost or the impact of what you proposed, or the cost or impact of space-based sun shades. The third "link" is not even an actual link.

 

[sophiecentaur]

None of these things estimate the cost or the impact of what you proposed, or the cost or impact of space-based sun shades.

I can see you don't want to consider an Earth based solution but those figures do indicate a difference in the cost of implementation, don't they? What's missing - apart from the area needed, which could be largely the same? If you want the conversation to take this course then the least you can do is to counter my figures with some of your own (preferably not in too cryptic a way, for the benefit of your readers).
If you are talking about the cost and impact to the Earth then the fact that the space based solution is not easily reversible (if there is an unforeseen impact) would make it even less attractive. In many ways, a large structure out in space would be the ultimate eyesore.
What is your actual objection to an Earth based solution? Could it be possible pollution? That could be valid but suitable materials would be chosen, needless to say, to be low toxicity.
Edit: And you never go back on the issue of roads. What's the problem apart from ice?

 

[mfb]

I can see you don't want to consider an Earth based solution

You are wrong. I want to consider all solutions. But I want to consider them based on numbers, not random promises.

but those figures do indicate a difference in the cost of implementation, don't they?

They don't. Not even remotely.
You made a claim. It is not my task to find numbers for what you propose.

What's the problem apart from ice?

White roads reduce the contrast to nearly everything else. Reflective items and white markings on a black road are easily visible. Black markings on a white road are more difficult. Glare from the road would increase a lot. And I don't know how long they would stay white - tires are black. You probably get a weird mixture of white and black quickly. And that is even worse.

 

[sophiecentaur]

They don't. Not even remotely.

If you are refuting my figures so strongly then you must surely have ideas of your own. Are you saying that transport costs are not relevant? Is there a single item in the space solution that would be cheaper than for an Earth based solution? Give me some numbers that could convince me that you have thought this out, rather than rejecting the idea out of hand.

Roads: Roads are mostly black because tar macadam is usually the cheapest material. Sourcing any other colour costs you more. So we are used to black (ish) roads. Do you have figures to justify what you say about roads. (I feel I'm justified to ask for this, in the light of your responses.)

 

[nikkkom]

but you still need to find a way to re-sequester the CO2.

I propose those 500nm light-reflecting, self replicating carbon-based nanostructures. They sequestered so much CO2 over last 500 million years, they nearly choked themselves by driving its concentration below 0.03% in air.

 

[nikkkom]

I keep telling people to paint all the desert regions white.

I have a small correction to that proposal. Paint all deserts in photovoltaics. (more like "tile" rather than "paint"). This would reduce CO2 emissions quite a bit. Tiling "only" the Sahara desert would produce 10 times more electricity than we currently consume.

 

[sophiecentaur]

I have a small correction to that proposal. Paint all deserts in photovoltaics. (more like "tile" rather than "paint"). This would reduce CO2 emissions quite a bit. Tiling "only" the Sahara desert would produce 10 times more electricity than we currently consume.

Where appropriate, it could be a good idea but my solution is suitable for places that are hard to get to for maintenance.(Re-painting or re-spraying is trivial compared with mending PV array or the supply cable.

 

[stefan r]

I have a small correction to that proposal. Paint all deserts in photovoltaics. (more like "tile" rather than "paint"). This would reduce CO2 emissions quite a bit. Tiling "only" the Sahara desert would produce 10 times more electricity than we currently consume.

That still needs some detail. A NbTi superconductor cable stretching from central Africa to San Francisco would pose costs and engineering challenges proportional to building an orbital ring. The yanutskiy model orbital ring uses a thinner cable and is made out of much cheaper raw materials.

The Sahara is habitat for wild Jerboas:

 

[nikkkom]

The Sahara is habitat for wild Jerboas:
View attachment 222245

Oh noes! Sorry, I did not know Sahara is not totally uninhabited!

Since we are going to just assume Jerboas die instantly when they see PV panels, I propose total ban of any and all PV installations in Sahara from now to eternity. I think we also should consider banning all human activity completely.

Please do not report my previous post (one about tiling Sahara with PV) to world-eco-thought-police. I don't know how on Earth I managed to be so callous to these poor oppressed animals, why I totally disregarded their existence, their historic, biological, cultural and artistic value. I am such a neanderthal.

Oh no. I just implied that neanderthals are somehow worse than our species. This is PROBLEMATIC, isn't it?