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Comment: Re:no we can't (Score 1) 31 31

by Rei (#50017541) Attached to: Asteroid Day On June 30 Aims To Raise Awareness of Collision Risks

It is not only possible, but the easiest option, to "blow them up Armageddon style" (minus the drilling and the like). There's a lot of simulation work going on right now and the results have been consistently encouraging that even a small nuclear weapon could obliterate quite a large asteroid into little fragments that won't re-coalesce, while simultaneously kicking them out of their current orbit. A few years ago they were just doing 2d calcs, now they've gotten full 3d runs.

Think for a second about what nuclear weapons can do on Earth. Here's the crater of a 100kt nuclear weapon test. It's 100 meters deep and 320 meters wide. You could nearly fit a sizeable asteroid like Itokawa inside the hole. And that thing had Earth's intense gravity field working against it and was only 1/10th the size of weapons being considered here. In space you don't need to "blast out" debris with great force like on Earth, you merely need to give it a fractional meter-per-second kick and it's no longer gravitationally bound. And the ability of a nuclear shockwave to shatter rock is almost unthinkably powerful - just ignoring that many if not most asteroids are rubble piles and thus come already pre-shattered. Look at the "rubble chimneys" kicked up by even small nuclear blasts several kilometers underground (in rock compressed by Earth's gravity). Or the size of the underground cavity created by the wimpy 3kT Gnome blast - 28000 cubic meters. Just ignoring that it had to do that, again, working against Earth's compression deep underground, if you scale that up to a 1MT warhead the cavity would be the size of Itokawa itself.

You of course don't have to destroy an asteroid if you don't want to - nuclear weapons can also gently kick them off their path. Again, you're depositing energy in the form of X-rays into the surface of the asteroid on one side. If it's a tremendous amount of energy, you create a powerful shattering shockwave moving throughout the body of the asteroid. If it's lesser, however, you're simply creating a broad planar gas/plasma/dust jet across the asteroid, turning that whole side into one gigantic thruster that will keep pushing and kicking off matter until it cools down.

The last detail is that nuclear weapons are just so simple of a solution. There's no elaborate spacecraft design and testing program needed - you have an already extant, already-built device which is designed to endure launch G-forces / vibrations and tolerate the vacuum of space, and you simply need to get it "near" your target - the sort of navigation that pretty much every space mission we've launched in the past several decades has managed. In terms of mission design simplicity, pretty much nothing except kinetic impactors (which are far less powerful) comes close, and even then it's a tossup. Assuming roughly linear scaling with the simulations done thusfar, with enough advance warning, even a Chicxulub-scale impactor could be deflected / destroyed with a Tsar Bomba-sized device with a uranium tamper. Even though it was not designed to be light for space operations, its 27-tonne weight could be launched to LEO by a single Delta-IV Heavy and hauled off to intercept by a second launch vehicle.

Comment: Re:Not surprised (Score 3, Insightful) 226 226

by Rei (#50015665) Attached to: Uber France Leaders Arrested For Running Illegal Taxi Company

Uber drivers are subsidized by everybody else. Taxi drivers have to pay high insurance rates because the act of driving a long distance every day for a ton of strangers is a job that inherently leads to a much higher statistical rate of payouts. If they're driving as a taxi on regular car insurance, it's you that's paying the bill for their swindle of the insurance system.

Comment: Re:What plan? (Score 1) 85 85

How do you come to that assumption?

By linking to a peer-reviewed paper on the subject?

A nuclear warhead has lots of trouble to even "hit" an asteroid.

Essentially every space mission we have launched for the past several decades has had to navigate with a far more precision than that needed to get close to an asteroid and activate a single trigger event when close by.

Comment: Re:What plan? (Score 3, Interesting) 85 85

We send spacecraft on comparable missions all the time. And it doesn't really take a spectacularly large payload to destroy (yes, destroy) an asteroid a few hundred meters in diameter. 1/2-kilometer-wide Itokawa could be blown into tiny bits which would not recoalesce, via a 0,5-1,0 megatonne nuclear warhead, a typical size in modern nuclear arsenals (in addition, the little pieces would be pushed out of their current orbit).

I know it's a common misconception that "nuking" an asteroid would simply create a few large fragments that would hit Earth with even more devastation, but that's not backed by simulation data. And anyway, even if it didn't blow the asteroid to tiny bits (which simulations say it would) and even if it didn't push the remaining pieces off trajectory (which they say it does), anything that spreads an Earth impact out over a larger period of time is a good thing - it means the higher percentage of the energy that's absorbed high in the atmosphere rather than reaching the surface (less ejecta, lower ocean waves, a broader (weaker) distribution of the heat pulse, etc), the weaker the shockwaves, the weaker the total heat at any given point in time, and the more time for Earth to radiate away any imparted energy or precipitate out any ejecta cloud. If the choice is between 15 Chelyabink-sized impactor (most of which will strike places where they won't even be witnessed) or one Meteor Crater-sized impactor (same total mass), pick the Chelyabinsk ones. 50 10-megatonne meteor crater impactors or one 500-megatonne Upheaval Dome impactor? Pick the former. The asteroid impacts calculator shows the former generating a negligible fireball and 270mph wind burst at 2km distance, while the latter creates the same winds 25km away (156 times the area) and a fireball that even 25km away is 50 times brighter than the sun, hot enough to instantly set most materials on fire.

But that's all irrelevant because, quite simply, simulations show that nuclear weapons do work against asteroids.

What we need is enough detection lead time to be able to launch a nuclear strike a few months before the impact date (to give time for the debris to disperse). There is no need to "land" or "drill" for the warhead. There is no pressure wave; instead, an immense burst of X-rays is absorbed through the outer skin of the asteroid on the side of the explosion, causing it to vaporize (unevenly) from within, especially near the ground zero point, and creating powerful shockwaves throughout its body. In addition to ripping it apart, the vaporized material and higher energy ejecta flies off, predominantly on the side where the explosion was detonated, acting a broad planar thruster.

Comment: Re:200 cycles? (Score 3, Insightful) 122 122

by Rei (#50008581) Attached to: Samsung Nanotech Breakthrough Nearly Doubles Li-Ion Battery Capacity

On the other hand, if they're doubling capacity, then you only need half the number of cycles (it actually even works *better* than that, as li-ion cells prefer shallow charges and discharges rather than deep ones - but yes, fractional charge cycles do add up as fractional charge cycles, not whole cycles). If you have a 200km-range EV and you drive 20 kilometers a day, you're using 10% of a cycle per day. If you have a 400km-range EV and you drive 20 kilometers a day, you're using 5% of a cycle per day.

Comment: Re:well then (Score 5, Insightful) 122 122

by Rei (#50008563) Attached to: Samsung Nanotech Breakthrough Nearly Doubles Li-Ion Battery Capacity

Top commercial li-ion capacities are about 30% more than they were 5 years ago. And today's batteries include some of the "advances" you were reading about 5 years ago.

I'm sorry if technology doesn't move forward at the pace you want. But it does move forward when you're not looking. Remember the size of cell phone batteries back in the day?

Comment: From TFA: (Score 4, Insightful) 212 212

by Rei (#49993911) Attached to: France Could Offer Asylum To Assange, Snowden

Taubira doesn’t actually have the power to offer asylum herself, however. She said in the interview that such a decision would be up to the French president, prime minister and foreign minister. And Taubira just last week threatened to quit her job unless French President François Hollande implemented her juvenile justice reforms.

So, basically, "not going to happen".

Comment: Re:Little does we know... (Score 1) 167 167

by Rei (#49983939) Attached to: Elon Musk Probably Won't Be the First Martian

Nothing wrong with a piece of fiction with laughably bad science on almost every page. If someone gets a kick out of the book, then it's met its purpose. But when the author gets treated as a "Mars expert" due to his his "hard sci fi" novel, that's where I start having a problem.

Comment: Re:The Moon is the way to go (Score 1) 167 167

by Rei (#49983775) Attached to: Elon Musk Probably Won't Be the First Martian

Why would you build a moonbase for a radiotelescope or gravity wave detector? What's the argument for dropping it into a gravity well (where it can be exposed to moonquakes and moon dust) and having people operate it when you can just have it unmanned and in space (Earth-Moon L2 for a radiotelescope, Earth-Sun L5 for a gravity wave detector) at orders of magnitude less cost and far greater effectiveness?

Every one of these sort of proposals just screams "I'm an excuse that was made up solely to give us a reason to go back to the moon". The most glaring is surely 3He mining, of course ;)

Comment: Re:Part of why I didn't become an astronaut (Score 1) 167 167

by Rei (#49983757) Attached to: Elon Musk Probably Won't Be the First Martian

We see the propulsion breakthroughs right now - there's a wide range of propulsion systems possible with current technology. Unfortunately, the turnaround on these sort of things is measured in decades (generally with a number well over "1"). And if it has any form of the word "nuclear" in the title, multiply the average time from conception to deployment by a large number.

Comment: Re:dirt cheap rocket launches (Score 1) 167 167

by Rei (#49983745) Attached to: Elon Musk Probably Won't Be the First Martian

Nobody of course is requiring rockets to be our long-term future. I have a soft spot for the Loftstrom loop concept, for example (aka, a track that holds itself up via the centrifugal force of a rapidly spinning rotor magnetically suspended in a vacuum inside it). Way more efficient and high throughput than a space elevator and requiring no unobtanium.

Comment: Re:dirt cheap rocket launches (Score 1) 167 167

by Rei (#49983737) Attached to: Elon Musk Probably Won't Be the First Martian

It would of course not make fuel cheap until we can learn to mine cheaply in space. And we're not even 1% to that stage. You have to pretty much relearn how to do everything you take for granted on Earth in space. Look at Philae just attempting to softly touch down at very low speeds - it had four different ways to try to stop it from bouncing (shock absorbers, ice screws, harpoon, counter-force rocket), and it still bounced way off and ended up in some rocks somewhere. And you're picturing setting up a whole refinery there? Yes, some day. But that day is not close.

The radiation issue is a big one that a lot of people downplay (they forget that the only reason the Apollo astronauts got away with as little shielding as they did was that their missions were on the order of a week or so long - and even still, they would have been in bad shape if a solar storm had hit. As it was they reported seeing regular flashes of light from cosmic rays impacting their retinas.

There've been a number of proposals for how to deal with shielding. One is to build a mini-magnetosphere around the spacecraft; my last reading on the subject was that it would be a realistic way to deflect most solar radiation but not GCR. You still really need physical shielding (which is a complex topic... beta and gamma are blocked by heavy metals far better than they are by light materials, but neutrons need to be moderated down to be stopped effectively, which means light, high scattering cross section elements like hydrogen; heavy ions tend to multiply high energy neutrons. And to make matters worse, forms of radiation switch around - betas kick off gammas due to bremmstrahlung, gammas can kick off photoneutrons or betas, betas can kick off neutrons too, neutron capture kicks off gammas, transmuted elements decay releasing gamma, beta, positrons, alphas, sometimes neutrons... It's really tough.

Most proposals call for using fuel, water, oxygen, etc as part (but not all) of the shielding - it's particularly good against neutrons, as all of these things are generally composed of CHON, all of which are good moderators (especially the hydrogen). A common proposal is to have the heaviest shielding around the beds, as you get better bang for your kilogram that way. I've pondered a more advanced version of that, having significantly more fuel / water / etc tankage space than you need (the extra mass would be part of your shielding anyway, so it's not really a "penalty") and having a computer system intelligently pump it around to where people are at any given point in time and where the sun is / what the current solar radiation flux is / etc. I wouldn't be surprised if you could cut the radiation dose to less than half in that manner, possibly a lot less. You'd need durable, reliable pumps, of course.

Comment: Re:Little does we know... (Score 3, Interesting) 167 167

by Rei (#49981781) Attached to: Elon Musk Probably Won't Be the First Martian

Are you kidding? I can't help but picture the MST3K characters ribbing it the whole time.

The main character is a "scientist" who doesn't use a single scientific term, instead using 50s pop-sci-fi style terms like "Oxygenator". I mean, here we have a botanist on Mars who doesn't even know the word "regolith" or understand why you'd have solar panels tilted at a particular angle. But don't worry, the book is full of such award-winning prose as phrases like "My asshole is doing as much to keep me alive as my brain". Seriously, it reads like a 13 year old boy.

But that's minor compared to how on pretty much every page we have Weir demonstrating his complete lack of knowledge of even the most basic aspects of every field of science he covers. Here, let's just pull up a random one:

Not because of the perfect landing, but because he left so much fuel behind. Hundreds of liters of unused Hydrazine. Each molecule of Hydrazine has four hydrogen atoms in it. So each liter of Hydrazine has enough hydrogen for *two* liters of water

High school chemistry, anyone? (Morbo Voice) Stoichiometry Does Not Work That Way! Weir again and again mixes up volume, mass, and moles. (For anyone not seeing it yet: hydrazine is 1,021g/cm^3, hydrogen makes up 12,5% of the mass, or 0,128 g/cm^3; water under STP conditions is 1 g/cm^3 and hydrogen makes up 11% of its mass, or 0,11 g/cm^3. 1 liter of hydrazine gives you 1,16 liters of water under STP conditions, not 2).

Here, let's grab another one of these from just a couple pages earlier:

"Once I get that hooked up to the Hab's power, it'll give me half a liter of liquid CO2 per hour, indefinitely. After 5 days it'll have made 125L of CO2, which will make 125L of O2 after I feed it through the Oxygenator."

Brilliant - not only do we have him once again confusing volume and moles, but we also have "liquid CO2", meaning that for some reason on a planet where a mere shiny bucket will hold frozen CO2 indefinitely, they've decided for no apparent reason to store it as a superfluid in heavy pressurized tanks at dozens to hundreds of atmospheres and elevated temperatures.

Oh, here's a great one: at one point he starts a diary entry by noting that he's now hiding out in a rover because he screwed up and didn't notice that his hydrogen levels in his habitat were climbing and his oxygen levels were dropping over the course of many days until he checked a meter. How much? The hydrogen went up to 64% and the oxygen levels to 9%. Really, the high squeaky voice didn't clue you in? The anoxic unconsciousness didn't clue you in? *Facepalm* Did this guy not get *anyone* to proofread?

The most mind-bogglingly glaringly bad stuff is of course the plants. As we all know, the sun is an incredibly energetic source. Look at the light in your living room for a few seconds. Notice how you're not blind. Now try it with the sun. Yeah, there's a bit of a difference. WIth the sun high overhead on a clear day the ground on Earth receives about 1000 W/m^2 of light energy. Now picture the brightest CFL you can find on the market - maybe one of those giant 40-watters? To match the light output of the noon sun would take 150 to 200 of them per square meter. Even taking into account angles, night, clouds, etc, it's a ton of energy. To grow the couple hundred meters of potatoes to feed a person? Well, you do the math.

So how does our hero plan to grow his plants? Here's Wier's entire justification

Also, the internal lights will provide plenty of 'sunlight''.

That's it. That's his entire justification on how he plans to provide enough light for his potatoes - normal interior lighting powered by a little solar farm on a dusty planet that receives half the light of Earth. Not even normal yields of potatoes, but super yields of potatoes! In regolith that he does nothing to remove the perchlorates or salts from (never mind that he does nothing to shield his electronics in his 100% ventilation-free canister from the humidity which he describes as raining down). And with Weir's humorously bad misunderstanding understanding of gardening we get his interpretation of potato mounding (aka, packing up soil around potatoes once they get to a large enough size to keep them focused on storing starch rather than going to flower):

Also, as their flowering bodies breach the surface, I can replant them deeper, then plant younger plants above them.

You see, the entire part of the potato plant that breaches the surface is merely a "flowering body". You can reuse space just by planting plants successively on top of each other like cordwood! Trust me, I'm a botanist!

Seriously, this thing is MST3K in book form. Hopefully the movie won't be this terrible. Or maybe it'd be best if it was...

The rate at which a disease spreads through a corn field is a precise measurement of the speed of blight.