Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?

Comment: Re:I love KSP, but sometimes... (Score 2) 84

by Rei (#49567821) Attached to: Kerbal Space Program 1.0 Released After 4 Years of Development

Everything else in KSP has had months of testing (perhaps even years) and they change fundamental things like the aerodynamics model without letting it be tested by the established community?

But isn't that so in the Kerbal spirit? ;) Hmm, what's the coding equivalent of forgetting a ladder? :)

Comment: Re:I love KSP, but sometimes... (Score 4, Interesting) 84

by Rei (#49567797) Attached to: Kerbal Space Program 1.0 Released After 4 Years of Development

Yeah, the old aerodynamics was pretty horrible. Add a nosecone to your blunt-tipped rocket and it increases the drag? What kind of logic is that? It needed to be fixed.

There's a couple balance issues I'd like to see fixed, mind you. For example, it's possible to make small solar ion-powered aircraft in Kerbal. But only small ones, because all of the ion engines available are tiny, and all of the fixed solar panels are tiny, so while technically it's possible to make bigger craft, the necessary part spam makes the game unplayable. Fuel for ion engines is also absurdly and unrealistically expensive for no obvious reason. Yet solar panels and RTGs produce orders of magnitude more power than they should for a given size, if ion engine power to thrust ratios for a given ISP are used as the baseline.

Drop xenon costs, tweak power production / consumption for existing hardware, and add in nuclear reactor power sources (after all, they have nuclear rockets, we know kerbals understand nuclear physics), and and you could balance that out pretty well in terms of both gameplay and at least slightly more approaching realism.

(Note that one may be tempted to say that the ion thrusters are far too high power, but at least that's plausible if we assume that they're MPD thrusters with some type of advanced cooling system - you can get crazy power to weight ratios (by ion standards) out of MPD thrusters if you could somehow supply them many megawatts of power and dissipate all the waste heat - they manage it in pulsed mode, at least. But Kerbal's solar panel area-to-thrust ratios at the given ISP are not even close to being compliant with the laws of physics)

Comment: Re:Awesome! (Score 4, Interesting) 84

by Rei (#49567721) Attached to: Kerbal Space Program 1.0 Released After 4 Years of Development

I love how true that all is. You have Musk making Kerbal references in his tweets. I've seen engineers from SpaceX doing likewise. I was once chatting with a researcher working on a Titan probe concept and he responded at one point with something like, "Well, like what one experiences on Eve in Kerbal Space Program...."

The development team really should be proud.

Comment: Re:danger vs taste (Score 1) 590

by Rei (#49567335) Attached to: Pepsi To Stop Using Aspartame

Thank you, but I said nothing about calories. Did I? I don't see it anywhere. I commented that a sugar SUBSTITUTE actually has more sugar than substitute in it.

By mass only, but thats a complete red herring since you use far less of it than you would of actual sugar.

Nobody is ever going to make a mass-market pure Stevia product because it's way too hard to use - it's just way too concentrated of a sweetener. Trust me, I've used it, I usually have to resort to weighting it out on a jewler's scale. It's silly to point out small amounts of sugar filler; for a given amount of sweetness you'll never consume a significant amount.

They could use something else that wasn't a digestable carb instead.

No, people like you and "food babe" would freak out at the names of indigestible carbs far worse than you do with dextrose. And dextrose won't alter the texture or flavor of the food product like many indigestible carbohydrates such as resistant starches would.

I was talking about ingredients in Stevia products; she has the documentation.

She has a page full of claims, half of which are laughable BS that she just made up, as is her typical modus operandi.

Right. Ok. Whatever. I don't think I told you to believe everything she's ever said, did I?

You're the one who linked to a running joke, its your problem.

Comment: Re:danger vs taste (Score 1) 590

by Rei (#49567297) Attached to: Pepsi To Stop Using Aspartame

I just gave you a link to a peer-reviewed study which studied its breakdown components in the bloodstream and you're still claiming otherwise? Tsk tsk. And to help you out with what you're confusing, you're mixing up aspartame with olestra. Olestra is the food additive that doesn't break down in the small intestine, passes through, and if eaten in excess causes loose stools or related problems. The quantities of olestra used, since it's a substitute to fats, are significant. The quantities of aspartame used are far too small to have such an effect even if they didn't break down rapidly in the intestines (which has been amply documented that they do).

Comment: Re:danger vs taste (Score 1) 590

by Rei (#49567283) Attached to: Pepsi To Stop Using Aspartame

find it humorous that you are ranting about me for "anecdotal evidence" when you just challenged someone to "prove me wrong right now in just a couple weeks" by using the same kind of evidence.

Surely you'll admit that "I experienced it myself" is better than "some TV 'documentary' whose name I don't remember had some woman who claimed it"

The human digestive system does not throw away energy from digestible substances.

Uhhh, yeah, it can. Maybe there's more to this than you know? Ok, the digestive system may not, but the excretory system can.


The interior surface of the small intestine is composed of microvilli that dramatically enlarge its absorptive surface, accounting for an extraordinary efficiency in absorbing consumed substrates: 98% of all digestible carbohydrate is absorbed; 95% of all fat is absorbed; and 92% of all protein is absorbed.

That's the baseline. How much more efficient exactly do you think your particular digestive system is than 98% of carbs, 95% of fat and 92% of protein?

Comment: Re:danger vs taste (Score 2) 590

by Rei (#49565763) Attached to: Pepsi To Stop Using Aspartame

I took a look at buying Stevia in the store awhile back. I am also a reader of contents labels, so I put it back on the shelf really fast. The first ingredient listed: dextrose

Boy you're a really clever one aren't you, catching onto secret calories in stevia that nobody else did?

First off, stevia is available in many different forms. Stevia is many times more potent than sugar in terms of sweetness, it's extremely hard to use pure (I have pure stevia - to use it pure you have to make very large batches and very tiny measurements!). To dilute it down you obviously have to mix it with something. There are all sorts of mixes, but there are two main categories: those that try for parity with sugar in terms of how much you use (which generally mix with maltodextrin), and those who try for a product that is much sweeter than sugar but not as extreme as pure stevia (these can come in a variety of forms, but a common blend is with dextrose). So yes, the dextrose has calories - but it's far outmatched in terms of sweetness by the stevia therein, so you only need to use a very small amount (depending on the ratio of the blend). The 1:1 parity versions as mentioned use maltodextrin, which is also caloric - but it's so light and fluffy that there's very little mass (and thus calories) per unit volume; basically, what the stevia is blended with is mostly air.

More fun facts about stevia here [100daysofrealfood.com].

Hahaha, Food Babe? Are you joking? The woman who says she hates air travel because they compress your bodies with high pressure air and it restricts your digestive organs? And how "the air that is pumped in isn’t pure oxygen either, it’s mixed with nitrogen, sometimes almost at 50%. To pump a greater amount of oxygen in costs money in terms of fuel and the airlines know this!" Or her microwave rant, where she talks about how microwave ovens are evil because once water has been microwaved it no longer crystalizes into pure forms when frozen, but rather into forms similar to water that has heard words like "hitler" and "satan"? This is your information source?

Yeah, I think I'll stay over here in the real world and not get my information from a living joke, thanks.

Comment: Re:danger vs taste (Score 1) 590

by Rei (#49565631) Attached to: Pepsi To Stop Using Aspartame

Having a strict target is not impossible, and when the difference between consumption and expenditure is on the order of 500 calories, you have room for error on both ends - on your estimation of your consumption and on the estimation of your burn.

There was a rousing ITV, or BBC, I don't remember, documentary on a woman

Whoa - throw away all of the scientific data, there's an anecdote here involving an TV show about an uncontrolled experiment whose data we can't see and whose name you can't even remember!

The human body works on calories. The human digestive system does not throw away energy from digestible substances. It's energy in vs. energy out.

Comment: Re:With the best will in the world... (Score 1) 447

by Rei (#49564703) Attached to: Audi Creates "Fuel of the Future" Using Just Carbon Dioxide and Water

Of that, its 1.4 litre turbo-charged diesel engine weighs about 90kg.

The engine, of course, being only part of the drivetrain components that can be eliminated by a switch to electric drive. Transmission, radiator, all fluids, fuel, the whole exhaust system, etc. In some designs you can even replace the driveshaft. You basically gut 90% of the moving parts.

The fuel tank holds about 42 litres of diesel weighing... whatever that weighs.

About 30 kilos.

It can do 600 miles urban or ~700 miles motorway, driving normally.

And that spec is relevant why? No seriously, please tell me. In what sort of realistic scenario is it critical to be able to drive for 700 miles nonstop without ever setting foot out of your car? How can you even do that? Do you not pee? Do you not eat? Even if you could it's not safe to drive that long nonstop, a person is supposed to take regular rest breaks. You stop for lunch, you plug your car into a fast charger, and you go off on your way afterwards.

The reason gas and diesel cars have such huge tanks has nothing at all to do with that being some sort of remotely practical requirement. It's to minimize a great inconvenience of ICE vehicles, that is, how often you have to go out of your way in your daily life at regular intervals in whatever weather it is and stand outside pumping fuel into your car. In your daily life, you never have to do this with EVs. Not once.

The longest range electric car that I can actually touch right now is the Tesla Model S; It's 3 times the size of my car, weighs over twice as much and has a third of the mileage, and costs 10x as much.

Really, we're going to compare a brand new luxury sports sedan with a used family car? That's the comparison we're going for? Have you tried comparing your car with a Bugatti Veyron?

Comment: Re:With the best will in the world... (Score 1) 447

by Rei (#49564607) Attached to: Audi Creates "Fuel of the Future" Using Just Carbon Dioxide and Water

Slow down there. You're comparing the complete-cycle efficiency for petroleum to just the end-stage efficiency for electric.

You seem to have not noticed what this article is about. It's about making fuel from electricity and then giving it to cars. Both sides start with the same feedstock: electricity. So it doesn't matter how efficient the electricity was to make because it affects both paths equally.

But let's switch back to your "scenario that I want to talk about that's not the one in the article"

Slow down there. You're comparing the complete-cycle efficiency for petroleum to just the end-stage efficiency for electric. That electricity needs to be made somehow. Toss in 40% efficiency for coal plants (we'll leave out pumping/mining and fuel transport costs for now, assuming they're similar for oil and coal), battery charging efficiency of about 75% [futurepundit.com] (discharge efficiency is unspecified, but since the EPA mileage estimates are based on battery capacity it's safe to ignore it), and the 85% motor efficiency you've specified, and suddenly your EV is .4*.75*.85 = 25.5% efficient. Same as a diesel.

I don't see that figure in your link, and I don't really need your link because I'm familiar with the numbers already. It depends on what you mean by "charging efficiency". The US grid averages about 8% distribution losses, plant to breaker. Li-ions are over 99% efficient at slow charging, but depending on the type can drop a few percent in faster charging scenarios, and in an extreme situation down to the lower 90%s. The charger itself has some losses, if I recall correctly from the breaker they're usually 92-94% efficient. So a good middle of the road number is more like 84%.

Also note that EVs automatically also function as hybrids: they regen and don't "idle".

Their EV is cheaper to operate not because the EV is more energy-efficient, but because coal is so much cheaper than gasoline

Coal is of course the dirtiest widely used power source, and its usage is declining in most first-world countries. Natural gas and wind have the highest growth rates. The most efficient combined cycle natural gas plants are upwards of 60% efficient, although that's not an "average" efficiency, but even old plants are generally over 40%. Efficiencies on things like wind, solar, etc are of course not particularly meaningful, since you're not burning a fuel. Nuclear has a low efficiency, but again, that's not particularly meaningful.

Even putting solar panels on your roof and amortizing the costs in most climates makes running an EV cheaper than gasoline. It's not because coal is somehow ridiculously cheap. It's because oil is a really expensive energy source per joule.

Wind is only about twice the costs of coal

If this was true, people would be churning out new coal plants, not wind farms.

Comment: Re:danger vs taste (Score 1) 590

by Rei (#49564477) Attached to: Pepsi To Stop Using Aspartame

No, it doesn't break down in the stomach. It breaks down in the small intestine. Very, very rapidly, leaving no detectable levels in the blood,.

The most recent study I read was in 2008 or so (and yes, I read the entire thing)

You read one study among the hundreds on one of the most highly studied food additives in history? Great, let me know when you're done with the others. ;) And I'm sure there was zero selection bias in your choice of which of the many studies to read ;)

Wikipedia covers the "cancer" thing well enough for a primer:

Reviews have found no association between aspartame and cancer. These reviews have looked at numerous carcinogenicity studies in animals, epidemiologic studies in humans, as well as in vitro genotoxicity studies. These studies have found no significant evidence that aspartame causes cancer in animals, damages the genome, or causes cancer in humans at doses currently used.[8][38][41] This position is supported by multiple regulatory agencies like the FDA[58] and EFSA as well as scientific bodies such as the National Cancer Institute.[47]

Concern about possible carcinogenic properties of aspartame was originally raised and popularized in the mainstream media by John Olney in the 1970s and again in 1996 by suggesting that aspartame may be related to brain tumors. Reviews have found that these concerns were flawed, due to reliance on the ecological fallacy[59] and the purported mechanism of causing tumors being unlikely to actually cause cancer. Independent agencies such as the FDA and National Cancer Institute have reanalyzed multiple studies based on these worries and found no association between aspartame and brain cancer.[41]

As discussed in the article on controversies around aspartame, the Cesare Maltoni Cancer Research Center of the European Ramazzini Foundation of Oncology and Environmental Sciences released several studies which claimed that aspartame can increase several malignancies in rodents, concluding that aspartame is a potential carcinogen at normal dietary doses.[60][61] The EFSA[62] and the FDA[58] discounted the study results due to lack of transparency and numerous flaws in the study, finding no reason to revise their previously established acceptable daily intake levels for aspartame.

Comment: Re:danger vs taste (Score 1) 590

by Rei (#49564405) Attached to: Pepsi To Stop Using Aspartame

This is a strange post.

1) How does this have anything to do with anything that I wrote?

2) How is this anything but agreeing with what I wrote, that it's the concentration of the methanol that matters? (note: it's a myth that only methanol causes hangovers; ethanol does also, although methanol is far worse per unit mass)

3) Methanol poisoning can be acute or chronic. A couple shots of spirits containing 10-20% methanol can cause serious optic nerve damage in one sitting. A few shots of pure methanol can kill you in one sitting.

And yes, I know how one distills liquer. :) While there's no exact rules, a general approach is to toss off anything that has a "chemical" smell (which doesn't come from methanol, but from acetone, which has a fairly similar boiling point to methanol, nearly as high), recycle anything that has a "fruity" smell (ethyl acetate, which has a boiling point very similar to ethanol and much higher than that of methanol), and keep only that which smells only like alcohol. Methanol of course also smells like alcohol but the lower boiling point leads it to get mainly tossed from the first cup.

There's also a home test one can do for methanol if you want to be really sure - you expose it to an oxidizer, such as potassium dichromate with sulfuric acid. Ethanol oxidizes to fruity-scented acetylaldehyde while methanol oxidizes to foul, pungent formaldehyde which is a very easy scent to detect even in small quantities. But that's really not necessary with proper distilling.

"Thank heaven for startups; without them we'd never have any advances." -- Seymour Cray