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Comment Calculations (Score 5, Interesting) 89

So you harpoon a comet with a velocity relative to you of 10 km/s. You have 1000km of tether. That means that if you didn't apply any braking, you'd have just 100s before your tether ran out. With little bit of physics, I find that the probe would need to accelerate at 50m/s^2 (over 5g) to match velocity with the comet before running out of tether (which takes 200s because now it is accelerating). So the tether and the harpoon need to withstand a tension of 5 times the earth-weight of the probe, without breaking or pulling the harpoon out of the comet. Now assume the probe is 1000kg. (For simplicity I'll ignore the mass of the tether and the rotation of the tether reel, although that would probably be a deal breaker too.) Force = 1000kg x 50m/s^2 = 50000N. Distance acted over = 1000km = 10^6 m, so work = 5x10^4 x 10^6 = 5 x 10^10 J. It is 200 s before the tether runs out, so power = 5x10^10/200 = 2.5x10^8W = 250 MW. That power has to be stored and/or dissipated, and you have at best 1000kg with which to do it.

It all gets very much easier if your relative velocity with the comet is much lower, but then you're not gaining much, and intercepting a comet with only few km/s relative velocity is very hard in itself.

It is a pretty idea, but I can't see it working with anything vaguely like current technology.

Does anyone care to poke holes in my reasoning?

Comment Re:Avoid INTERCAL (Score 1) 427

Avoid INTERCAL job postings at all costs.

So, you mean the fact that I wrote a c-intercal parser that used obscure opcodes to actually perform the interweave and or and xor isn't a good thing to put on my resume?

Also, my favorite obscure language is LIRL, and that has NOTHING AT ALL TO DO WITH ME BEING THE AUTHOR... rather, it's an interesting concept of, "what if Perl raped LISP and LISP was forced by the republican state government to carry that baby to term?"

The answer is: implied parentheses. To be clear, the language is absolutely context sensitive...

Comment Re:Actually, the common saying... (Score 1) 343

I ended up booting into DOS directly for most of these reasons.

Oddly, I barely even use 95... went straight from 3.x to 98. Where I still booted into DOS to do my gaming.

Ah... back in the day... I had to tetris my drivers to make sure I had enough conventional and XMS memory for the game I wanted to play... BOTH WAYS!


NSF Makes It Rain: $722K Award To Evaluate Microsoft-Backed TEALS 64

theodp writes: Microsoft has $92 billion in cash parked offshore, so it's kind of surprising to see a $722K National Science Foundation award is going towards validating the efficacy of Microsoft TEALS, the pet program of CEO Satya Nadella that sends volunteer software engineers with no teaching experience into high schools to teach kids and their teachers computer science. Among its Program Changes for 2015, TEALS said it "explicitly commits to provide a core set of curriculum materials that are complete, organized, and adaptable," which should help improve the outcome of the Developing Computer Science Pedagogical Content Knowledge through On-the-Job Learning NSF study schools are being asked to participate in. Meanwhile, CSTUY, a volunteer organization led by experienced CS teachers (including Slashdot user zamansky), finds itself turning to Kickstarter for $25K to fund Saturday Hacking Sessions. So, as Microsoft-backed — which has also attracted NSF award money to validate its CS program — is fond of saying: What's wrong with this picture? (To be fair to TEALS: it may have Microsoft backing, but it's not strictly a Microsoft effort, and also started out as a pure volunteer effort, as founder Kevin Wang explained earlier this year.)

Comment Re: Even if practical technology was 10-20 years o (Score 1) 395

Maybe. My thought has always been that if fusion is close enough to get ballpark figures, we can build the necessary infrastructure and much of the housing in parallel with fusion development. Because the energy distribution will impose novel demands on the grid, it's going to require a major rethink on communications protocols, over-generation procedures, action plans on what to do if lines are taken out.

With fusion, especially, it's expensive at best to learn after the fact. Much better to get all the learning done in the decade until working fusion.

With all that in place, the ramp time until fusion is fully online at a sensible price will be greatly reduced.

Parallelize, don't serialize. Only shredded wheat should be cerealized.

Comment Re:Might want to read the fine print... (Score 4, Interesting) 165

This is fine - they're not pretending those impacts don't happen, they are just not what they're studying. They are asking "What does the fallout do to people some distance from the accident?"

The exposure people get early in the accident and very close to the reactors depends hugely on the nature of the accident. At Chernobyl, there were many firefighters within meters of an exposed critical core, resulting in a large toll from acute radiation sickness. At Fukushima, the cores ceased to be critical seconds after the quake and tens of minutes before the tsunami, and radiation was only released days later, so there was no acute radiation sickness.

By contrast, the effect of the fallout is much less dependent on the nature of the accident, just on how much radioactive material was released*. It can sensibly be studied without specifying details of how the accident happened.

* There is some dependence: the relative quantity of short lived isotopes such as Iodine-131 in the fallout depends somewhat on how long the radioactive material was contained prior to release.

Comment Causation? (Score 5, Insightful) 87

The more niche your research topic, the longer the title has to be to describe it, and correspondingly the fewer people will be interested. Compare, for example, "A New Hierarchy of Phylogenetic Models Consistent with Heterogeneous Substitution Rates" with "The Origin of Chemical Elements". While one will be much more cited that the other, the reason isn't the title length.

Comment Re:We had one, it was called the Shuttle. (Score 4, Informative) 71

For the cost of one shuttle launch you could more than pay for SpaceX's entire development program so far. For two launches you could pay for their development so far plus the extra they'll need to finish the Dragon capsule and "man-rate" the system, and still have some money left over for a couple of launches (each of which can carry as many crew as the shuttle.)

(I'm taking the cost of a shuttle launch as about $1.5B. Lower values can be argued for, adjust the above as needed for your preferred cost.)

For a few more shuttle launches and a several year wait, Blue Origins would likely be able to field a man-rated rocket, if you want multiple space taxi companies to chose from. ULA could do it too, but that would probably cost you ten shuttle launches.

The shuttle was hideously expensive and needed to go.

Comment Re:Bullshit (Score 1) 106

It isn't clear to me whether they collect heat and use some heat engine, or whether they use a small area of high cost high efficiency high temperature photovoltaic cells. As I've complained elsewhere, the articles provide almost no detail. There is mention of cooling water, but either possibility could use that.

Comment Re:No details (Score 2) 106

You'd use differential GPS. Wikipedia says this has accuracy of 10cm in the best case. Whether that is good enough for this application I'm not sure. Given that affordability is a big part of their goal, if they were taking this approach they'd not attach a GPS to each mirror, but rather have two receivers that they used for a callibration stage and then wouldn't be needed again unless something shifted. You'd need to know orientation as well as location for the mirrors.

I doubt this is what they're doing, but who knows.

Comment No details (Score 4, Informative) 106

TFA is lacking in details about how this works, but if you follow the link you get to a Guardian article which is lacking in details, but links to the projects website which excessively uses gratuitous Javascript and is lacking in details.

They talk about "plonkability" - that the mirror structures can just be plonked on the ground and will 'just work'. This suggests to me that somewhere in their system is some intelligence or calibration which is able to notice where each mirror is relative to the target and adapt its pointing accordingly. Their photos show the target tower having two rectangular surfaces pointed towards the mirrors. I suspect the plane white surface is there to aid mirror pointing calibration in some way, but I don't know.

It's time to boot, do your boot ROMs know where your disk controllers are?