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Comment Re:Things that I wish wouldn't keep getting repeat (Score 5, Informative) 302

It takes billions (not millions) of years for hydrogen atoms to fuse in the sun - that is precisely why the sun has a billions-of-years lifetime. So in building a fusion reactor, we need many orders of magnitude higher reaction rates, and to achieve them at many orders of magnitude lower densities. One way of doing this is to have much higher temperatures. The solar core temperature is about 15 million degrees and TFA has 50 million degrees for this new result, and 80 million degrees for half a second at a European reactor. This sounds unimpressive, but the reaction rates are very sensitive to temperature - proportional to about T^8 as I recall, but I didn't quickly find an online reference for this. 75 million degrees would therefore give a boost of about 5^8 which is about 400,000.

In the sun, the first reaction in the chain (proton+proton->deuterium) is the rate limiting step. In a reactor, we can provide deuterium enriched fuel and bypass this step. I don't know what the reaction rates are, but I suspect that this will be a greater benefit that the higher temperatures. You can do even better with tritium in the fuel, but your reactor becomes an intense neutron source, leading to induced radioactivity in nearby materials. Some proposed designs use these neutrons to breed more tritium from a lithium blanket around the reactor. (Once I get beyond the proton-proton chain reaction, I'm just relying on pop-science knowledge, so corrections from the more knowledgeable are welcome.)

Stars a bit more massive than the sun burn hydrogen via the CNO cycle, which has even higher temperature dependence (from memory, about T^17). I've never heard of anyone suggesting using the CNO cycle in a fusion reactor - presumably there are good reasons, but I don't know what they are. One problem is you need to wait for radioactive decays, but these have half-lives on the order of 1 to 2 minutes, and a commercial reactor would be running for much longer than that.

Comment /. Poll opportunity (Score 2) 92

Poll 1: Which nation/organization do you think will be next to land people on the moon?
* China (CNSA)
* Japan (JAXA)
* Europe (ESA)
* India (ISRO)
* Russia (RFSA)
* North Korea (KCST)
* Privately funded (e.g. SpaceX, Blue Origin or Cowboy Neal without direct state support) (ETLA)

Poll 2: Which nation/organization do you want be next to land people on the moon?
(same options)

Comment Secondary sources (Score 1) 1829

NASA discovers little green men on the moon. NASA makes a 2 page press release. Bob writes a blog post where he condenses the NASA press release to 1 page, mostly by deleting every second paragraph. (Alternatively it could be a Javascript and advertising heavy commercial news site.) Slashdot posts an article linking to Bob's blog, rather than linking directly to NASA as they should. One of the first comments provides the direct link (with title something like "This is the link you should be using") and instantaneously gets modded to +5, in reward for having done what the Slashdot editor should have done.

I'm not saying never use secondary sources - sometimes Bob has summarized 50 pages to 1 page (and done a good job of it), or added some insightful commentary. Just don't use secondary sources unless they add significant value, and always include a link to the primary source in the summary.

Comment Re:Staged chute deployment - how's that work? (Score 1) 91


It sounds like this system relies critically on the coefficient of friction between the slider grommets and the risers. Too high, and the slider never (or incompletely) slides and the chute does not fully inflate. Too low, and it inflates too fast and soon, bruising or breaking the parachutist or, worse, ripping the chute.

From the abruptness of the transition between slightly inflated and fully inflated in the space capsule chutes, and the prolonged delay before this occurs, I suspect the friction method you describe is not used. However a slider with some other release mechanism seems likely.

Comment Staged chute deployment - how's that work? (Score 3, Interesting) 91

There is a thing that these chutes do, where on initial deployment the open aperture of the chute is quite small, and the chute looks rather like a sausage. Then later on, the chute abruptly opens fully, and looks like a hemisphere. (The transition wasn't shown in the video in TFA, but I've seen it elsewhere and it is also simulated in Kerbal Space Program.)

How is this achieved? Is it some clever aerodynamics where the chute has two stable configurations and a 'catastrophic' transition? Is there some rope which constrains the aperture early on and then is somehow severed to allow fully deployment?

(I understand why - the first configuration slows the payload sufficiently so that the chute is not torn apart when it fully deploys. "How" is what I don't know.)

Comment Re:If AdBlocking is freedom-hating... (Score 1) 539

I've tried to find an article about this recently, but haven't been able to find the article that I read. But it turns out Google actually has your data collection lie to Google on a regular occasion. They get enough data that the lies shift out in the statistics, and in addition, no one at Google can actually trust specific data that you've sent Google...

Comment Re:Amazon has no idea what security is (Score 1) 131

So, I looked up the SMTP RFC, and yeah, the "local-part" (as it is determined) is to be treated as opaque by everyone BUT the domain in the address. Meaning that everyone must treat the addresses differently regardless of how GMail or anyone else interprets the semantics...

AND THEN, it turns out that while things are required to be case-insensitive, things are ALSO required to be case-sensitive. Basically, no one should ever assume that the local-part of the email address can be treated as caseless.

So, there you go, if Amazon doesn't let you sign up as both smith@example.com and Smith@example.com, then they're totally out of spec...

But to the deeper part, why would Amazon not disable an account when someone with a local-part semantic collision calls in to object to getting the emails? "These two addresses are treated as semantically identical by my email provider, please figure out how to fix the other person's account," doesn't seem like a horribly unreasonable request... I'm sure they'd do it for Smith@example.com coming from smith@example.com...

Bitching about the RFCs and complaining that GMail is the problem is entirely misreading the RFC, and misreading reality in fact...

Comment Re:anecdotal or statistical (Score 1) 507

However, statistical evidence is just an aggregation of anecdotal evidence.

No, sorry, completely wrong.

Statistical data comes from a well defined sample which is designed to be representative of an entire population. Anecdotes have no well defined selection criteria (my grandmother smoked until she was 100, and because I don't want to believe smoking is harmful, I remember and put great importance on this, and forget all the other people I have a connection to who were damaged by smoking) or (often where the selection criterion is 'stuff that happened to me') too little data to draw a conclusion (I've never crashed while driving drunk, so it must be safe.)

"I remember really hot days 10 years ago, hotter than now" holds very little weight. It is your experience (perhaps for every person like you there are 100 with the opposite experience), it is subject to biases of memory, and you've chosen the example retroactively to support a given position. The statistical data is thousands of thermometers measuring temperatures every hour over decades.

Comment Re:It's really too soon for this post. (Score 1) 118

You can't sail a drilling platform up to a wharf to unload the rocket, like you can a barge (so your idea would require an extra transfer at sea from platform to barge), nor is it so easy to move around the landing spot to match mission requirements. Having said all that, if barge landings turn out to be sufficiently haphazard, your idea may be economical.

Comment Re:Steam Boat Willy (Score 1) 70

People could animate Hamlet with a certain mouse as the protagonist (so long as it looks like 1930s Willy not 21st century Mickey.) They could distribute the Steam Boat Willy cartoon modified so that the mouse protagonist is naked and has oversized genitalia - just so long as they never call the mouse protagonist "Mickey". I think these are the sorts of possibilities that give Disney executives sleepless nights.

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