Wikipedia:Reference desk/Archives/Science/2016 August 24

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August 24

Does the International Space Station have enough radiation hardening to survive outside LEO?

Does the International Space Station have enough radiation hardening to survive outside LEO?

According to International_Space_Station#Communications_and_computers, there are ~100 regular Thinkpads on board, so those won't survive outside LEO for sure. But I'm unable to find out:

1. Whether those ~100 Thinkpad on the ISS are mission critical or not. Maybe they're just there for the various scientific missions and are not critical to the functioning of the space station.

2. Whether the mission critical computers on the ISS have enough radiation hardening to survive outside LEO. Pizza Margherita (talk) 00:29, 24 August 2016 (UTC)

ISS only orbits at an altitude of ~400km which is within even the ionosphere. Low earth orbit extends out to about 2000km, so I doubt ISS is intentionally "hardened" to survive outside of LEO. It's intentionally hardened to survive precisely where it is. Whether it actually "would" survive outside LEO or not is a different question. Earth's_magnetic_field#Magnetosphere extends out at the "short end" to 65,000km, so even well above LEO I don't think the "radiation" is much worse, AFAIK it only gets really bad once you get outside of the magnetosphere. Discounting CMEs. Vespine (talk) 02:45, 24 August 2016 (UTC)

"Whether it actually 'would' survive outside LEO or not is a different question." Yes, that's the question I'm asking. Pizza Margherita (talk) 03:05, 24 August 2016 (UTC)

Well that's a question of "probabilities". Like I said, I don't think the radiation outside of LEO is dramatically different to the radiation at the normal orbit of the ISS, at least until you start reaching the upper levels of the magnetosphere. So undoubtedly everything would survive for some time, including normal laptops. I'm not sure why you say "those won't survive for sure"? What's your reasoning for that? I don't think anything would necessarily "fry" immediately even if you took it out of the magnetosphere. How long on average would a regular laptop survive in space? Well we didn't take any laptops to the moon so I don't think anyone has done the experiment. Vespine (talk) 04:17, 24 August 2016 (UTC)

This is a bit outside my wheelhouse (and more importantly, not referenced) but my understanding is that ambient solar radiation in the space that Earth's orbit occupies is more than substantial enough to fairly well guarantee that a non-shielded device like a laptop would be rendered non-operational instantly, if moved outside the magnetosphere (indeed, probably well before you cleared what is considered the outermost edge of the magnetosphere). As you say though, LEO is a more nuanced, probabilistic question with quite varied answers depending on the specific circumstances. It's also worth mentioning, in looking at the scenario the OP proposes, that the station itself is shielded, as an essential safeguard of the health of the crew and redundancy on protection of critical hardware--although this protection is variable by module and even at its best allows for significantly higher levels of radiation exposure compared to a typical terrestrial context. Snow ^{let's rap} 08:10, 24 August 2016 (UTC)

You are wrong here. The dangerous ionizing radiation from calm Sun is nil or near so. The really dangerous thing is galactic cosmic rays, which are constantly present and partially deflected by the magnetosphere. There are also solar flares, which can generate beams of accelerated protons and electrons, but they relatively rare and partially predictable. Ruslik_Zero 19:32, 24 August 2016 (UTC)

Yes, I actually do appreciate the prevalence of cosmic rays; I'm not sure why my mind went to focus on stellar emissions so strongly; that said, the sun is a non-trivial source of high-intensity radiation, and not just when there is enough activity to register a geomagnetic storm. Snow ^{let's rap} 07:40, 25 August 2016 (UTC)

Whether the station will survive is a different question from whether the inhabitants of said station will survive. What is your definition of LEO? If you shift up to >1000 km, you're in the inner van Allen belt. Both electronics and inhabitants would be fairly swiftly fried in there (yes radiation is dramatically different there than in LEO). If you leave the Earth's magnetosphere altogether, you'd have both increased background radiation from cosmic rays, and be very much at increased risk from solar events, such as CMEs. The ISS is not designed for these. Have a look at the specialised computer required for BEO work, see Mongoose-V for one. There are significant other issues as well. For instance, the thermal management of the station is designed for LEO, that is regular alternation between orbital day and night. The (near-)constant sunshine in higher orbits would most likely overwhelm the thermal control system. Lastly, it would be a short trip for anyone in the Station, even if all the above wasn't a problem, as no resupply is possible with current craft at above LEO. Fgf10 (talk) 07:15, 24 August 2016 (UTC)

Metabolism

What is the average age that metabolism starts to slow down, ignoring lifestyle etc and only considering the physiological aspects of the human body? 82.132.220.29 (talk) 19:09, 24 August 2016 (UTC)

Here are the google results for "age of peak metabolism". μηδείς (talk) 19:44, 24 August 2016 (UTC)

...These are mostly magazine blurbs, and not very good references. Generally, googling simple phrases is not a good way to get good references. Generally, people who can find our desks are aware that google exists. This is a reference desk, and our goal is to help people find good references. SemanticMantis (talk) 20:12, 24 August 2016 (UTC)

Here [1] is a research article titled Influence of Aerobic Capacity, Body Composition, and Thyroid Hormones on the Age-Related Decline in Resting Metabolic Rate - it discusses how other factors affect the decline, and also gives results for the net decline on average. See Fig.1 for details and trend. SemanticMantis (talk) 20:12, 24 August 2016 (UTC)

Visualizing the Earthlike planet around Proxima

I just asked something similar, but I plead special circumstances: an Earthlike planet found just four light years away, around Proxima Centauri. Now I assume IRL people will keep blundering on like nothing happened, but if any decent author were writing sci-fi, this would be the precise moment when astronomers all over the world *DROP EVERYTHING* and point their telescopes at the planet, time and cost be damned, get the ALMA array pointed at it, improvise whatever kind of VLBI in visible light to analyze the signal is possible, invent anything they can with a few tens of billions of dollars, and come up with an image of what this providential and perilous world might hold for us.

If they do, how much can they see? What kind of data can they get? Proxima is something like 60,000 271,000^[2] [d'oh, forgot to multiply by 4!] AU away, I think, or 12000 50,000 times the distance of Jupiter; in the previous thread we had somebody speculating we could "read a license plate" on Jupiter's moons with the right VLBI around the Earth, so that implies seeing details less than a four thousand feet across, and presumably taking detailed spectra to see which kind of chlorophyll they use. But what can we really do? How far can we go that direction? (Heck, I'd be happy just to see the moon that keeps it from being tidally locked to its star...)

Stoking my interest is that I'm imagining that the polite method of first contact is that you visualize the other planet, you visualize its people, you visualize their telescopes, you see them looking at you, you put out a decoration to show them you see they're looking at you, and they reciprocate... Wnt (talk) 20:03, 24 August 2016 (UTC)

By "ALMA array" I guess you mean the Atacama Large Millimeter Array array. —Tamfang (talk) 02:41, 25 August 2016 (UTC)

• Read Mary Doria Russell's The Sparrow and sequel about intelligent life in Alpha Centauri. It's in my top ten of novel or novel series. Deals with the same star system, and a signal of alien life, although an accidental one. Quite a deep, engaging, and literary read, along the lines of Dune, or Lord of the Rings. μηδείς (talk) 20:42, 24 August 2016 (UTC)
• According to the report in Nature, the next step is to find a transit of the planet across the sun, which might reveal whether it has an atmosphere.[3] Our article on the planet is Proxima Centauri b.-gadfium 23:00, 24 August 2016 (UTC)

One priority for the future will be to get a direct image of the planet.This should be possible with the European Extremely Large Telescope now under construction in Chile. "It is being given a 39m-wide primary mirror and state-of-the-art instrumentation precisely to do this kind of observation.

"A planet around even a wimpy star like Proxima Centauri is going to be more than a billion times fainter than the star itself. So, what you do is block out the light from the star using a special device and that allows you then to go deeper into the star's surroundings," explained Cambridge University's Prof Gerry Gilmore. "This is one of the E-ELT's design goals. There's also a Nasa mission under development called W-First. It will have a high-resolution coronagraphic mode which again is designed for the same purpose."" Count Iblis (talk) 23:25, 24 August 2016 (UTC)

A 100 meter radius screen about 1.4 million km from Earth blocking the starlight would probably do. It would be large enough for diffraction effects to be small enough. The diffracted starlight would still overwhelm the light from the planet in an unprocessed image, but one can subtract the diffracted starlight from the image using the observations of the star and the known shape of the blocking screen. Count Iblis (talk) 23:57, 24 August 2016 (UTC)

See coronagraph for how it's really done. --Wrongfilter (talk) 10:49, 25 August 2016 (UTC)

To clarify, a very large telescope like E-ELT should be able to visually distinguish the planet from its star (E-ELT resolution at that distance ~0.004 AU). This would allow spectroscopic studies of the planet, which could provide us with some interesting observations. Such telescopes would still not be able to resolve any spatial details on the planet itself though, which would still appear as point-like. To resolve spatial details on the planet itself, you'd really need some sort of telescope array whose baseline is comparable to the size of the Earth itself. Maybe some day, some how, but we are very far from being able to do things like that with visible light right now. Also, Proxima Centauri is 260,000 AU away and not 60,000 AU as suggested above. Dragons flight (talk) 07:24, 25 August 2016 (UTC)

Exploding batteries

I have an electric pencil sharpener which can run with either 4 AA batteries or using a 6V AC adapter. The manual is warning me that I should not use the batteries and AC adapter at the same time, because the batteries might explode. Why is that? What would cause the batteries to explode and how likely is it? bamse (talk) 20:51, 24 August 2016 (UTC)

The AC adapter will charge the batteries in some circumstances, and it can be dangerous to charge batteries if they are not designed to be charged. Even rechargeable batteries can explode if incorrectly charged. Dbfirs 21:12, 24 August 2016 (UTC)

Yes, but I am interested in the details (physics) of it. bamse (talk) 21:50, 24 August 2016 (UTC)

• "Explode" is a bit much (for AA at least). It is quite likely that they will be over-pressured and will burst, or at least vent. This dumps corrosive battery contents into your pencil sharpener and so is not a good idea. It's unlikely to be a personal hazard though.

AA batteries will probably be alkaline, could be the older zinc chloride and might well be the rechargeable NiMH. Any of these will "burst" in an operator-safe manner. If it was using Li-ion though (which won't be in AA format, but are becoming much more popular for the next few years - look out for '18650' cells) then mis-charging can and does cause battery explosions sufficient to damage furniture or carpet and sometimes to burn a house down. Those are normally protected by the circuit surrounding them, but still it has (and will) happen. Andy Dingley (talk) 21:58, 24 August 2016 (UTC)

Sorry for being persistent, but I'd really like to know more about the reason for the "explosion". Do they just heat up due to the current running through them? Is some gas produced which causes them to explode? Does the polarity (which way I put the batteries) matter for this? bamse (talk) 22:20, 24 August 2016 (UTC)

Just google "What can happen if Non Rechargeable Batteries are Recharged". There's plenty of articles. Vespine (talk) 22:43, 24 August 2016 (UTC)

This Nature paper, ...materials for safer batteries (January 2016) was described in the Stanford news service a little while ago. That article has a lot of technical information and extensive citations for the electromechanics of the battery overcharge and overheat failure modes.

Nimur (talk) 22:57, 24 August 2016 (UTC)

• Persistence is good - you're going to need it to understand batteries. There are so many different types that you'll not get a single simple answer to this.

Since alkalines replaced zinc-carbon as the general household "torch battery", batteries have been made with steel cases. Before this they leaked because the corrosive contents had etched through the zinc case and the paper wrapper. Now it's usually because internal pressure has caused the end seal (at the negative end for alkaline) to fail. Corrosion as primary cause is now less common, but we've all seen the mess they can make of contacts or a circuit board. An AA is a small battery - small enough that a pressure failure won't make the case fall apart, but larger than a coin cell which can bulge a little and yet still contain the excess.

The mechanism of pressure buildup is complex and depends on the battery technology. It could be simple heating, and thus expansion. This is why fast charging batteries is a problem and why good fast chargers either cool the battery under charge or measure its temperature and limit the current accordingly.

Mis-charging is likely to cause the wrong sort of chemistry to happen. If a battery is charged (when not rechargeable), charged in reverse, for too long or at too high a current, then not only the useful chemical process (which stores energy for recovery later) can happen, but also some other ones. Simple electrolysis is one, especially for excess current - an aqueous electrolyte can be split into hydrogen and oxygen. Gases occupy far more space than liquids, so up the pressure goes...

The classic zinc–carbon cell uses a reaction between zinc and manganese, with an electrolyte of white zinc chloride paste and another black paste of manganese dioxide. The carbon rod is just there as a non-corrodible electrode to give a connection to the manganese paste. As well as being a reactant in the main reaction, the manganese dioxide has a second function to mop up any loose hydrogen produced. It can only do this slowly, so excess current (charge or discharge) can overwhelm it and free gas is released.

Most battery cells are sealed, but with the expectation that they will vent in a controlled manner. A few types have a resealable vent, many stay open once ruptured. Some battery chemistry then goes awry because the contents are exposed to the air. Alkaline batteries are noted for this - they may first vent only a small quantity of potassium hydroxide, which then produces a large mass of soft, spongy white potassium carbonate as it reacts with CO₂ from the air. If this starts to happen inside the battery, it may split right in half.

Li-ion and Li-polymer bring in a further range of issues. See Lithium-ion battery#Safety. They're sensitive to almost every form of abuse, are more sensitive to it, react more violently than other domestic types. Oh, and the components are flammable too, if exposed. A fire in stored batteries awaiting disposal led to the closure of the M6 motorway in England [4]. Modern versions are safer, but there are still real hazards from mis-charging with fake chargers [5] or just impact damage [6]. Andy Dingley (talk) 02:39, 25 August 2016 (UTC)

Thanks a lot. That's what I wanted to know. No more questions ;-) bamse (talk) 10:14, 25 August 2016 (UTC)

Just for completeness I'll mention what people are assuming above: as batteries deplete, the voltage they produce drops. Presuming the AC adaptor is not set at a voltage level where the electronics are at the verge of failing, or even at the point where a "low battery" light would flash, a set of batteries wired in parallel with the adaptor would be charged when it is active, at least if they were sufficiently depleted. Of course, some sort of mechanism might be made to interrupt the connection to the batteries when the AC adaptor is in use, but this costs money and volume and if it doesn't work 100.0000% they'll still advise people not to keep batteries in the device when the AC is active, just in case. Wnt (talk) 15:03, 27 August 2016 (UTC)

Titanic

2 questions about the sinking of the Titanic: (1) Had Captain Smith ordered one engine full astern and the other two full ahead (instead of putting them all full astern and trying to steer with the rudder alone, like he did), could he have avoided hitting the iceberg altogether? (2) Once the ship hit the iceberg, it was doomed to sink (that much practically everyone agrees on), but by deliberately flooding one or more of the aft compartments in order to keep the ship's bows up, could they have stayed afloat long enough for help to arrive? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 23:25, 24 August 2016 (UTC)

• File:Stockholm following Andrea Doria collision.jpg

It's been said that if he had hit the berg head-on, the ship would have been disabled but would have stayed afloat. For a practical example, look at the ship that hit the SS Andrea Doria straight on, albeit not on purpose. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:56, 25 August 2016 (UTC)

Captain Smith was not on the bridge at the time. Command had passed to First Officer William Murdoch, who was left with very little time to react. Akld guy (talk) 08:05, 25 August 2016 (UTC)

• If he was equipped with that much hindsight, he could just as well avoided the iceberg altogether.

It's an interesting question in naval architecture - the problem of over-topping the watertight bulkheads - if keeping the ship level, albeit lower, would have kept it afloat, or afloat for longer. Certainly Titanic went down because of the bow-down angle. How well would a lowered but level Titanic still float? As that's accurately calculable (but I haven't) I express no opinion here. It's worth remembering that it's a passenger ship though, not a warship. Decks are connected by staircases, not ladders with sealable hatches. A warship has options for sealing itself into compartments which just aren't practical on a liner. HMS Audacious is an interesting comparison, just a couple of years later - much of the questioning around that sinking was about how well hatches had been closed to control the flooding. Andy Dingley (talk) 10:21, 25 August 2016 (UTC)

It was a moonless night, and they didn't see the berg until they were almost on it. By trying to turn away from it, they hit it with the side of the ship, which popped several plates and doomed the ship. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:42, 25 August 2016 (UTC)

Yes, but the question (which has been debated for decades) was whether it would have been better to 'port around' (Murdock's alleged manouevre - a kind of fish tailing) the iceberg without attempting to slow down by throwing the engines into reverse. Reversing the propellers is known to make a rudder's angle less effective than when at speed. My guess is that in the 37 seconds available, the engines were probably only stopped and there was no time to throw them into reverse, consequently the stationary propellers didn't make any difference in the few seconds remaining. Akld guy (talk) 11:42, 25 August 2016 (UTC)

I recall a television documentary in which a model of Titanic was tested in a water tank. Some of the aft compartments were flooded to test the hypothesis that this would have prevented or sufficiently delayed sinking of the ship. The test suggested flooding aft compartments would not have saved Titanic. I regret I have no details of the documentary. Dolphin (t) 11:54, 25 August 2016 (UTC)

See also Russian Engineers: Did Titanic Have a Chance? for some rather implausible suggestions. Hindsight is a wonderful thing. Alansplodge (talk) 21:51, 25 August 2016 (UTC)

A more sensible article is at Saving the Titanic which supports the proposal of ramming the iceberg bows-on and also suggests fothering. Alansplodge (talk) 22:00, 25 August 2016 (UTC)

If you are piloting the Titanic, it would take some extreme confidence to decide that ramming an iceberg head-on was the preferable course of action. Can you imagine trying to defend that action after-the-fact? How many people could you really convince that the "unsinkable" Titanic would be at risk but only if one tried to dodge? After smashing the bow of the boat, the person in charge would probably never work again and have a high risk of going to jail. Dragons flight (talk) 09:54, 26 August 2016 (UTC)

A minor and tangential point, but to correct a common misconception: the "unsinkable" description was used by some newspapers of the time, but Titanic's operators, the White Star Line, never claimed she was unsinkable. [Disclosure: For over 30 years I have lived near and worked in Southampton, Titanic's home port, where the public are still mindful of the disaster and can even be a little touchy about such inaccuracies.] {The poster formerly known as 87.81.230.195} 2.219.83.36 (talk) 15:06, 26 August 2016 (UTC)

They may not have said it, but they "acted like" they had. They were totally unprepared for an emergency. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:44, 26 August 2016 (UTC)

A few note on preparedness:

1) Obviously travelling at high speed through icebergs was a dangerous thing to do, especially without using a speedboat to speed ahead of the ship and communicate icebergs sooner. A searchlight on the bow would have extended visual range further forward, at least in clear weather.

2) The lack of adequate prep to evacuate the ship (like a lack of boats) was also critical.

3) The rivets may also have been more brittle than they should have been, and thus popped more easily (saw this in a documentary).

4) The compartments that didn't seal at the top and the lack of a double hull also sealed Titanic's fate.

5) As for what actions the command staff could have taken, I agree with "all engines in reverse and hit it head on" approach. Of course, there wasn't time to think all this through when the berg was spotted, so they would have needed to think all this through in drills ahead of time. There also wouldn't be time to look it all up in the manual, so the proper response needed to be committed to memory on anyone who pilots the ship. StuRat (talk) 16:26, 26 August 2016 (UTC)

I'm not sure if reduced dark adaption would've hurt less than increased forward visibility would've helped (statistically, obviously it would be better in this specific case). They accidentally left the binoculars in Southampton, 1,500 people died because some dude forget binoculars.

This site says that the binoculars actually were on board... but the guy who knew where they were wasn't. There's a locker full of them waiting to be raised and auctioned off by some entrepreneur. :) However, this source also claims they'd have been of "limited" use given the conditions. Wnt (talk) 15:40, 28 August 2016 (UTC)

Yes, the ambient light level would certainly go up if you used a searchlight during fog, snow, or perhaps rain, impairing forward visibility. This is why I only suggested this option in fair weather. Obviously the searchlight would need to be properly shielded so no light escapes out the sides or back and light doesn't hit a rail in front and reflect back at the watcher(s). The only limitation I see, with that technology, was keeping the light from overheating without letting light escape where the cool air was let it. A long, flexible, black tube with an electric fan forcing cool air in, could provide ventilation, with the hot air venting out the front, or you could add a similar exhaust tube with fan to suck the hot air back out, if additional cooling was needed. StuRat (talk) 18:51, 28 August 2016 (UTC)

Hmmmm, StuRat, that's an inventive proposal even by your standards. Are you going to blow away the fog from in front of the ship so that any icebergs behind it can be seen on a foggy night? Are you sure it wouldn't work better to have some half mile long ultra-light segmented antennae held up by balloons that the ship could use to feel around for icebergs in the dark? Wnt (talk) 11:50, 29 August 2016 (UTC)

Nope, as I've said, I wouldn't use the searchlight in the fog. I'd still use the boat out front and slow way down so that if they did hit a berg, they wouldn't sink. Communicating with the boat out front and keeping it in front of the Titanic could be a problem in heavy fog, though. Wireless telegraphy could solve the communication problem, but the positioning problem is harder to tackle. Maybe a rigid beam would be an option, to connect the ship and boat, but it would need to be designed so it would go off to the side of the Titanic if it hit a berg, not impale the ship. To extend the beam out far enough, it would need floats to support it's weight, or would itself need to be able to float. Not sure if the cost would make this worthwhile, though. Perhaps better to just stop until the fog clears. StuRat (talk) 14:32, 29 August 2016 (UTC)