Catch up on stories from the past week (and beyond) at the Slashdot story archive

 



Forgot your password?
typodupeerror
Get HideMyAss! VPN, PC Mag's Top 10 VPNs of 2016 for 55% off for a Limited Time ×

Comment Re:Harm (Score 1) 93

Kind of funny, our company is on the cutting edge actually, but in fluorescents, not LEDs, which are terrible for producing what we would consider high output of UVB or UVA. There is a huge difference between 320nm and 399nm, yet both are "UVA". 320nm has a lot more energy, and as you up in frequency (down in nm), it forms a Bell curve and gets exponentially more damaging. It also goes down in penetration, which is why you can get a quick flash burn from UVC (100nm-280nm) that doesn't penetrate more than a few layers of skin, but it is very damaging to those layers. And of course, the real kicker is how much you are getting.

And the reason it has that warning on it is simple: anything with any measurable amount of UVA must have that warning by law. The FDA regulates this (CFR 1040.20 for sunlamps, for example). I'm used to seeing them regularly for inspections. For some reason, general lighting fluorescents are excepted from this warning, even though they do produce a measurable amount of UVA.

Comment Re: drone ship landings require a lot less fuel? (Score 1) 101

I don't need to stand by the rotation theory. However, the 2.5 degrees that the Earth rotates are about equivalent to the downrange distance.

The first stage is going about 1/5 of the target LEO orbital velocity at separation. While you might well model the trajectory as a parabola over flat ground, given the lack of fuel I would expect that SpaceX puts a lot more care into their trajectory. So far I've failed to attract the attention of the person responsible for Flight Club, the most trusted modeling of SpaceX flights, but I'll message him directly.

Comment Re: drone ship landings require a lot less fuel? (Score 1) 101

Well, Alastair, you should probably not get snotty and ad-hominem, unless you want me to comment on how a one-time sci-fi author and the Unix guy at Dish doesn't really have more authority than the random person one might find in the SpaceX group on Reddit.

It happens there are a few people over there who are rocketry professionals, have the math, and have followed SpaceX long enough. So, sure, their opinion can indeed be trusted.

So far, we have a suggestion from one of the lesser folks there that raising the apogee takes advantage of the Earth's rotation. We'll see if we get the attention of the right people.

Comment Re: drone ship landings require a lot less fuel? (Score 1) 101

It seems to be a common misconception that orbital mechanics somehow knows when you are in orbit and does not work otherwise. But that is as silly as saying that relativity only works near light speed. These things always work regardless of speed, it's just that their effects are macroscopic at greater speeds.

Comment Re:Harm (Score 3, Informative) 93

385nm is invisible to almost all humans, being on the long-ish wavelength of UV, and I wouldn't really say it was very damaging. Everyone likes to jump on the bandwagon like they actually know something about UV when in fact they don't. I've worked with it over 25 years, still do. Out of the millions of products sold, I've never had an injury reported. People do get hurt with UV, but that is exceedingly rare and usually because they didn't follow directions or did something really stupid.

Inside fiber, it is pretty harmless. Most plastics block it (excepting OP4 acrylic), the vast majority of paints absorb it and won't reflect it. It has a smaller wavelength, thus more waves per centimeter, ie: more data. I'm not saying their plan is good or bad, but blanket calling UV dangerous and not workable is ignorant.

Comment Re: drone ship landings require a lot less fuel? (Score 1) 101

Here's an illustration of the boost-back to RTLS trajectory. You can see that it very definitely goes up. And to prove from observation, you can actually see where the two trajectories separate in photos from yesterday's launch. It's a rather dim curl up, and another continuing East, in Jason Ruck's photo and John Kraus's photo.

At the speed of stage separation, they rocket isn't going fast enough to stay in orbit, but it is definitely in the regime where orbital mechanics has a macroscopic effect. If you think about it, this is going to be the case at some reasonable fraction of orbital velocity.

Comment The perspective of a 3D animation professional (Score 5, Interesting) 300

This is just like the way people whined that color film had ruined the medium, and the ones before them who whined about talkies and yearned for the days of silent films.

I started at the NYIT Computer Graphics Laboratory in 1981 and left Pixar in 2000. These days I produce or am on screen once in a while.

While I was at NYIT they weren't story oriented, and thus all you see of them is demos. Pixar, on the other hand, always put story first. We knew that we could not make a film stand up on effects alone.

Today, a good 3D animation house can make absolutely any scene they like. And thus there isn't anything special about doing so. It's there if it needs to be there to tell the story, and not otherwise.

Comment The wave of the future (Score 2) 255

In a world of autonomous machines, people and animals are squishy bugs. If this sounds extreme, consider how it is actually the case in the world of automobiles, and how previous to that the risk was horse carriages. We can make devices good at not running over people, but never perfect.

Slashdot Top Deals

"Never ascribe to malice that which is caused by greed and ignorance." -- Cal Keegan

Working...