For Questions That Don't Merit Their Own Thread

[YNM]

53 minutes ago, Green Baron said:

Long story short: yes, the area has a potential for disaster, from eruptions (Krakatoa), Tsunamis (Aceh) and earthquakes. I am leaving the latter to be filled out in the future :-/.

I know, but to the best of my knowledge we didn't have something of that kind before. Most of the time thrust earthquakes usually "ripples" down the fault, so when one area had a fairly devastating earthquake then some other areas would have it.

The building damages are due to the older structures the population lives in, which are not retrofitted to the latest codes and are very vulnerable to even fairly "small" quakes. Talk about budget availability.

What I'm also concerned is, if this type of earthquake would persists, it'd mean that we have to upgrade the building codes (again) such that the magnitude of earthquakes that could theoretically be withstood without any damage will go up. To reduce cost, usually buildings are only required to have light damage for a certain quake magnitude, but it seems like this won't be possible anymore. I know they will need proper data-crunching to determine...

[Green Baron]

Tbh, i don't know about the exact tectonic situation in your region. I think it is not as good explored and researched as e. g. Europe, Japan or North America. Your country's geological survey may have better info.

I only know that it is difficult to say "It doesn't hit twice", as it is difficult to say "periodically it does this" or "something is overdue or due in". This is mainly because we do not know what the exact composition and conditions are like in the depth. It could theoretically even be that one initial heavy quake triggers others, on different depths in the same fault or on neighboring faults.

Also, if you say "before", this is probably limited to your lifetime or recent history, which spans a maximum of 500 years but rather 200 or so. That isn't enough to try a generalization, i fear. Also, keep in mind, as human settlements and property expands, the risks rise. And, i think, your country has seen explosive population growth from 70million in the 50s to >260m now according to wikipedia (curse it). So, i think that in this, together with what you wrote, lies the problem. Maybe. Or not. Or otherwise. Who knows ? :-)

 

Edit: Wikipedia (sigh) has a list of Indonesian earthquakes, they say it is based on usgs records. According to this list the Lombok earthquakes are not even at the upper end of the scale in the 2000s. There have been quite e few years with more and stronger earthquakes. Remember, 7,5 releases double the energy than 6.5 magnitudes. So, nope, i don't think this is special.

Edited August 19, 2018 by Green Baron
not

[K^2]

Earthquakes do have a tendency to cluster. Usually, a stronger quake will have both preceding and following weaker quakes. The ground is settling, and it's rarely a singular event. Whether it means it's going to get worse or better, that's the bit that's impossible to tell. Sometimes you have a pretty powerful quake, and it turns out that it's just one of the "smaller ones" preceding a really big one. But these really big quakes are rare to begin with.

I live in part of California that probably won't get thoroughly destroyed by a quake, but will definitely be left without power and water when The Big One hits. It's something you make preparations for, because eventually it will happen, and you will have to deal with it. In my case, dealing with it will probably involve grabbing provisions, getting onto a motorcycle, and going to Nevada.

[Green Baron]

30 minutes ago, K^2 said:

Earthquakes do have a tendency to cluster. Usually, a stronger quake will have both preceding and following weaker quakes. The ground is settling, and it's rarely a singular event. Whether it means it's going to get worse or better, that's the bit that's impossible to tell. Sometimes you have a pretty powerful quake, and it turns out that it's just one of the "smaller ones" preceding a really big one. But these really big quakes are rare to begin with.

I live in part of California that probably won't get thoroughly destroyed by a quake, but will definitely be left without power and water when The Big One hits. It's something you make preparations for, because eventually it will happen, and you will have to deal with it. In my case, dealing with it will probably involve grabbing provisions, getting onto a motorcycle, and going to Nevada.

Yep, totally depends on the situation. Earthquakes connected to subduction zones and slabs can originate in the lower mantle were stuff is ductile and an epicenter hard to localize, otoh transform faults that are shallow in the continental crust (like the San Andreas powder barrel) can jam for a long time until the tension is released in one big movement, or one movement can trigger others. As you say, there is no rule. But your area is heavily researched about and constantly monitored, there is a chance that a warning might come in time. Otoh, politics play a role. There was the case where Italian geologists got jailed because they issued warning from a quake that never took place.

I just read that the three Lombok quakes of this year may indeed not be independent and are probably connected to a local fault. Unfortunately, despite it being in such danger, Indonesia is not as good watched over as e.g. California or hotspots like Hawaii and the Canaries ...

Edited August 19, 2018 by Green Baron

[YNM]

7 hours ago, Green Baron said:

I only know that it is difficult to say "It doesn't hit twice"...

Well, sure, it did. Just 12 hrs after the last one. Now magnitude 7. Again.

https://www.bbc.co.uk/news/world-asia-45238018

https://earthquake.usgs.gov/earthquakes/eventpage/us1000gda5#executive

7 hours ago, Green Baron said:

There have been quite e few years with more and stronger earthquakes. Remember, 7,5 releases double the energy than 6.5 magnitudes.

There has been 5 instances of magnitude 6+ quakes until now in the area.

7 hours ago, Green Baron said:

Also, if you say "before", this is probably limited to your lifetime or recent history, which spans a maximum of 500 years but rather 200 or so.

True. But then, who remembered the Toba Supervolcano ?

7 hours ago, Green Baron said:

Also, keep in mind, as human settlements and property expands, the risks rise.

We already took the risk when we started to settle near the volcanoes for better farming I think XD nowhere else in the world you can grow crops 2-3 times yearly...

56 minutes ago, K^2 said:

It's something you make preparations for, because eventually it will happen, and you will have to deal with it.

Well, imagine living in a place hit by 5 consecutive mag. 6+ quakes in the space of a month.

30 minutes ago, Green Baron said:

Unfortunately, despite it being in such danger, Indonesia is not as good watched over as e.g. California or hotspots like Hawaii and the Canaries ...

Probably because it doesn't make much difference XD it's still going to happen... nor does the gov't have enough money for full retrofit (easier to find donors after a disaster than before it !).

 

 

But yeah, that was probably just me asking "how long again would this happen". Usually they travel around the faulting (ie. after Aceh in 2004 there were Nias and Simeulue etc.) so it looks a bit odd for so much fairly large events to take hold in one place. Anecdotal memories also serves that disasters are prone to struck every 5 years, roughly coincident with "political years", but who can be very sure...

[Xd the great]

Would global warming make earthquakes stronger?

Because, expansion of earths crust...

[Green Baron]

In principle: there are external and internal factors that drive earth's dynamics. In short, the border between those actually lies in the crust, where weathering and transport of rocks form sediments. Sediments, ice shields, etc. can exert forces on the earths crust, pressing it deeper into the softer Asthenosphere when they build up or letting it rise when they melt or when mountain ranges weather down. But these processes are slow, taking 100s to ~10.000 of years (ice shield dynamics) or even 10s of millions (weathering of mountain ranges). So, if there is a direct effect, it is slow and will probably not have any cataclysmic consequences or even be noticeable.

The crust is a very effective insulator. It heats and cools over 10s of to ~200 millions of years, example oceanic crust from middle ocean ridge to subduction zone/continental margin, cooling from >1000 to 15°C. And crust has a certain porosity, continental is even less dense than oceanic.

We are talking about 2.5 to 4 degrees global atmospheric warming in the coming decades, depending on modeling, with a fast rising tendency in the past years. While this will have (and already has) catastrophic consequences in the atmosphere, cryospehere and hydrosphere, i doubt that these changes will have enough time to influence the lithosphere and earth's crust, and they still are much too small for the material to expand.

But of course, processes like weathering, melting etc. are also depending on temperature, just imo not enough to cause earthquakes that are distinguishable from those driven by the earth's internal forces.

tl;dr: no probably not.

 

Edited August 22, 2018 by Green Baron

[KG3]

3 hours ago, Xd the great said:

Would global warming make earthquakes stronger?

Because, expansion of earths crust...

The earth would have to heat up an awful lot to effect the earth's crust.  However the melting of large ice sheets can effect the underlying geology just by the redistribution of all that weight.  I think if the earth heats up enough to melt the Greenland ice sheet a few extra earthquakes and volcanoes would be the least of our problems!  

https://en.wikipedia.org/wiki/Post-glacial_rebound#State_of_stress,_intraplate_earthquakes_and_volcanism

"One of the possible impacts of global warming-triggered rebound may be more volcanic activity in previously ice-capped areas such as Iceland and Greenland.[26] It may also trigger intraplate earthquakes near the ice margins of Greenland and Antarctica."

[Ginlucks]

Also real rockets execute the first burn, then wait to reach the apogee to burn again in order to circularize the orbit or they use a constant burning during the flight?

[kerbiloid]

9 minutes ago, Ginlucks said:

Also real rockets execute the first burn, then wait to reach the apogee to burn again in order to circularize the orbit or they use a constant burning during the flight?

Low Kerbin orbit V ~= 2.6 km/s
Low Earth orbit V ~= 7.8 km/s

A real rocket reaches the orbital speed in apogee, then finishes the engine burn.  It takes a proper amount of fuel for that, and usually stops burning when gets out of fuel. No pauses.

Edited August 23, 2018 by kerbiloid

[Ginlucks]

3 minutes ago, kerbiloid said:

Low Kerbin orbit V ~= 2.6 km/s
Low Earth orbit V ~= 7.8 km/s

A real rocket reaches the orbital speed in apogee, then finishes the engine burn.  It takes a proper amount of fuel for that, and usually stops burning when gets out of fuel.

Cool, Thanks

Wait... what in case, in the future, rockets will be so efficient to reach orbital speed before reach the apogee ?  the will use the ksp technique ?

Edited August 23, 2018 by Ginlucks

[Mad Rocket Scientist]

5 hours ago, Ginlucks said:

Cool, Thanks

Wait... what in case, in the future, rockets will be so efficient to reach orbital speed before reach the apogee ?  the will use the ksp technique ?

Probably not. The upper stage TWR required for that would demand a much heavier engine than necessary, and dividing more of the Delta-V to the booster would probably be non-optimum for some burnout velocity optimization calculations which I don't know.  

Also, engines have to be more complex and heavier to restart more times, although SpaceX's Raptor might solve that problem with spark ignition.

[magnemoe]

On 8/23/2018 at 9:43 PM, kerbiloid said:

Low Kerbin orbit V ~= 2.6 km/s
Low Earth orbit V ~= 7.8 km/s

A real rocket reaches the orbital speed in apogee, then finishes the engine burn.  It takes a proper amount of fuel for that, and usually stops burning when gets out of fuel. No pauses.

This, both the x15 and falcon 9 first stage would be orbital capable in KSP. KSP reentry heat is harder than real life to compensate so you would need more shielding but still SSTO would be pretty standard. 

On Earth forget SSTO unless you have an +1000 m/s from sea level engine. Its an obvious trap. Future technologies like skylon or microwave heated engines might manage it. 

[ARS]

Does a manta-ray submarine design makes sense? Instead of using ballast and rudders to maneuver underwater, it uses "Wings" and "Fins" to basically "Fly" underwater

[K^2]

1 hour ago, ARS said:

Does a manta-ray submarine design makes sense? Instead of using ballast and rudders to maneuver underwater, it uses "Wings" and "Fins" to basically "Fly" underwater

A submarine already can use its fins to go up and down without making alterations to its ballast. And there are recreational minisubs that rely just on that. But it's not a great option for a military submarine, as these things need capability of turning pretty much everything off and staying put. Having to keep moving to stay underwater would be a great disadvantage.

[Kerwood Floyd]

I suspect that the typical modern submarine hull shape represents the optimal trade-off between speed and interior volume. Admittedly, those factors aren't critical in every application, but the exceptions are probably pretty unusual.

[StrandedonEarth]

17 hours ago, K^2 said:

And there are recreational minisubs that rely just on that.

And it makes for a great failsafe. The minisub has to move to create downforce. If it stops moving it floats to the surface. 

19 hours ago, ARS said:

Does a manta-ray submarine design makes sense? Instead of using ballast and rudders to maneuver underwater, it uses "Wings" and "Fins" to basically "Fly" underwater

http://edition.cnn.com/2009/TECH/03/06/eod.luxury.submarines/index.html

Edited August 26, 2018 by StrandedonEarth

[monophonic]

15 hours ago, Kerwood Floyd said:

I suspect that the typical modern submarine hull shape represents the optimal trade-off between speed and interior volume.

Add noisiness to that mix and you are getting close. Active noise cancellation and other advances mean flow noise now dominates over machinery noise. Exact priorities over each other depend on the class; a bomber values maximal silence over all others while an attack boat needs to be fast enough to be useful.

[ARS]

Well, the submarine that I mentioned in my question is strictly recreational submarine, not military submarine, so I guess it makes sense to go for manta ray design (Especially with aforementioned safety)

[tater]

Stop what you are doing, and listen to the first section of This American life. David Kestenbaum interviews Frank Borman. It's fantastic.

https://www.thisamericanlife.org/655/the-not-so-great-unknown

 

[Cunjo Carl]

So, I have some silly questions I've started pondering. By rights this should really be in the 'shower thoughts' thread, but it probably fits better here. I'll probably start taking a crack at some questions soon, but figured I'd pose it to the general crowd in case someone found it to be a good exercise.

One of the key difficulties to terraformming Venus is removing most of its 91bar of green house atmosphere in order to allow the surface to cool. There's no suitable chemical or biological means (without a ton of work), and slamming an asteroid into the surface would apparently only clear away the atmosphere at the area of impact, so according to wiki it would take a couple thousand monster asteroids (700km diameter) to really thin out the atmosphere. So what if...

What if we delivered asteroids to a highly elliptic Venusian orbit where they could 'aerobrake' through the high upper atmosphere at ~7km/s. Could they kick enough molecules free to cause a difference? For the asteroid to actually kick the molecules free, it would need to pass at a high enough altitude (= low enough pressure) that the mean free path of the molecules is large enough they won't interact too many times on the way out.

With such heavy molecules (CO₂, SO₂), and at these altitudes, the thermal velocities of the atoms would contribute only negligibly, so they'd probably wind up in orbit of Venus. Once kicked free, could solar radiation pressure or solar wind slowly push these little molecules further away from Venus? They are green house gasses after all, absorbing and re-emitting IR light is kinda their thing! But would it be enough?
 
From an energy and efficiency standpoint, how many asteroids would we need (in terms of mass)? My hindbrain suggests maybe a few times Venus' atmosphere's mass equivalent is a good starting point for consideration. Is this feasable? Given the estimated number of asteroids in Venus' neighborhood, could enough be persuaded to gravity assist into the Venusian SOI to meet our needs? Once roughly there, could they be aerobraked into Venus' SOI without exploding? An ice asteroid probably not, but would a carbonaceous one be possible? Given the number (mass) of asteroids we'll need, and the fact they'll probably crash to the surface after slowing to low orbital speeds, will they noticeably change the length of a sidereal day? I'd sure imagine they would!

If those issues seem ok, how long would it take? Given the desired mean free path, the mass of asteroids, perhaps a 1km average diameter, a 7km/s velocity when skimming (setting the orbit period), and good (~33%) efficiency, we should be able to strike a rough estimate... It may be a while. For calculation' sake we would hypothetically tweak the orbits to maintain the mean free path as the atmosphere thins.

What's the general thoughts? Sound like fun?

[Mad Rocket Scientist]

My guess would be that the amount of asteroids needed would exceed the amount needed to cool Venus down by just making giant orbital solar shields.

[StrandedonEarth]

1 hour ago, Mad Rocket Scientist said:

My guess would be that the amount of asteroids needed would exceed the amount needed to cool Venus down by just making giant orbital solar shields.

Yup. Block all the sunlight and let Venus cool down. Eventually all that atmosphere will condense out. 

The bigger problem with Venus is the rotation rate. It needs a few grazing asteroid impacts to spin it up. Now how many would that take?

[Cunjo Carl]

56 minutes ago, StrandedonEarth said:

Yup. Block all the sunlight and let Venus cool down. Eventually all that atmosphere will condense out. 

The bigger problem with Venus is the rotation rate. It needs a few grazing asteroid impacts to spin it up. Now how many would that take?

But what'll it condense to? At those temperatures and pressures it would be... supercritical CO₂.You know what, that actually sounds super awesome, let's do it!

Assuming the asteroids come in 'slowly' at near Venus' escape velocity (~10km/s), and hit equatorial (~6000km) with good momentum transfer, each kg of asteroid would impart an angular momentum of 6*10^4 kg*km^2/s.

For a rotating sphere, the angular momentum we'd need would be (4*pi/5)*M*r^2/t . Venus' mass M is ~5*10^24kg, and let's say we want the rotational time t to be one day ~86000s. Assuming Venus is large relative to the asteroids, and that it starts with low angular momentum, that'll come out to be:
(4*pi/5)*5*10^24*6000^2/86000 = ~6*10^27 kg*km^2/s  Required angular momentum for Venus

Then, the required asteroid mass would be:
6*10^27 kg*km^2/s / 6*10^4 (kg*km^2/s)/kg = 10^23kg of asteroids, or about 1/50th the mass of Venus.

Yowza! That's a lot of asteroid. Sure we couldn't clear out the atmosphere with all that while we're at it

Edit: Turns out there's only an estimated ~3*10^21kg of asteroids in the entire asteroid belt (including Ceres). This maaaaay put a damper on things. On the plus side, Europa is 5*10^22kg, so we could make some good headway with that, and turn the atmosphere into soda water all in one strike! Despite the massive technical unfeasibility, I like the mental image enough to stick with it for now.

Edited September 6, 2018 by Cunjo Carl
Slight technical issue: not enough asteroids.

[Mad Rocket Scientist]

I remember a Stephen Baxter book, I think on of the Manifold series, talked about using superconductor rings to spin Venus up. Might be easier than moving 100 solar systems worth of asteroids. Of course, extra-solar asteroids would hit at above solar escape velocity, so you should need less of them. Actually, Venus escape velocity is probably an inaccurate estimate for asteroids from this solar system, since most of the asteroids would be coming in from the asteroid belt.