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Comment: Here's how (Score 1) 195

by IPFreely (#47939031) Attached to: Ask Slashdot: How To Pick Up Astronomy and Physics As an Adult?
I've gone through this. Here's how you do it.

Start gathering a few popular science books on subjects directly on and also near to your goal. Some people reject popular science books as too light weight, but it does have value. This exposes you to the variety of subjects in and around your interest. You might not have been aware of some aspects of your topic and you are introduced to them here without too much effort. You also learn to associate detailed technical topics to the wider areas where they are used.

Read the whole book. Books are better than random google searches and videos because they will guide you into areas you might not have considered relevant. Broadening your base knowledge will allow you to make a more informed decision about your favorite topics. Once you have a broader and more informed understanding of the topics and areas involved, you are better able to identify your interests, or even switch interests.

That is when you start going into a more detailed dive into your target topic. Follow through and read the whole thing. Again, pick one or more text books or deeper science books. The purpose again is to guide you into areas you might not have considered before.

This time, you will hit lots of technical subjects that you might not know. That is when you go searching for online information, wikipedia, online course videos, Youtube content or other textbooks. For these, you will only need to cover enough to support your primary interest, and you will have a fairly good idea how much that is.

You are not going to go professional with this, but it will be more than enough to keep your interest up and curiosity satisfied.

Comment: Re:Blastoff From the Past (Score 2) 18

by AJWM (#47934037) Attached to: ULA and Jeff Bezos' Blue Origin Announce Rocket Engine Partnership
The basic aerospike SSTO design goes back to the mid to late 1960s with Phil Bono's work (and a couple of his patents), and designs by the Douglas (later McDonnell-Douglas) corporation (SASSTO, ROMBUS, Pegasus, Hyperion and Ithacus). Chrysler Aerospace (IIRC) had a similar proposal for the initial Space Shuttle studies. Boeing's "Big Onion" came a bit later, after O'Neill's 1974 "Physics Today" paper kicked off the whole L5/space colony/solar powersat thing.

The designs were revived in the 1980s by Gary Hudson and Pacific-American Launch Systems (Phoenix) and later by General Dynamics (Millennium Express --disclaimer, I helped name it) as their proposal for the DC-X competition.

Yes, New Shepherd was clearly influenced by all that (as have several others, including a Japanese suborbital test vehicle). The design makes sense for a number of reasons:

  • structure weight is critical for SSTO, and the closer you get to a sphere, the better your structure-weight to propellant-volume gets, hence the relatively squat shape
  • the rounded-cone shape makes a great reentry vehicle, with some maneuverability (assuming asymmetric mass distribution)
  • the heat-shield on the base serves to protect against engine exhaust on launch as well as reentry heating
  • aerospike nozzles are inherently altitude-compensating, so potentially more efficient

Of course there are downsides to the design too, particularly in terms of integrating the design so that it's light enough for SSTO, and starting and controlling the large number of thrust chambers (usually at least 16, some designs with 24 or 32).

Comment: Re:Looking for a Job (Score 1) 70

by Animats (#47923925) Attached to: The Case For a Federal Robotics Commission

Is it just me, or does this sound like an ambitious Law Professor looking for a new job as head of a newly minted agency?

Exactly the feeling I got. We don't even have an Federal Internet Commission, and don't seem to need one.

We do need to have the Consumer Product Safety Commission setting safety standards for the Internet of Things. They're properly the lead agency of safety issues. That will probably happen after the first few deaths due to cloud-based control of home devices.

Comment: Re:Of course you use force control to run fast. (Score 2) 90

by Animats (#47920041) Attached to: MIT's Cheetah Robot Runs Untethered

Pardon my ignorant question, but how is it a problem to have traction control? Wouldn't it be enough to glue traction strips to the feet or something?

That's like wearing shoes with golf spikes all the time.

Traction control for feet does roughly the same thing as automotive traction control for cars. The basic idea is to keep the sideways force below the break-loose point. This is the down force on the wheel times the coefficient of friction.

For car wheels, the down force is mostly constant. For a legged robot, it changes throughout the ground contact phase So the side force has to be actively controlled and changed throughout the ground contact. It's also necessary to compensate for leg angle.

Legs have an additional option. If a leg has three joints, you can adjust the angle at which the contact force is applied. This is a big win on hills.

I used to work on this stuff in the mid-1990s, but nobody was interested in building legged robots back then. It could be used for animation, but it was overkill for games. I never expected that DARPA would spend $120 million on BigDog. Robotics projects in the 1990s were tiny.

Comment: Of course you use force control to run fast. (Score 5, Insightful) 90

by Animats (#47915427) Attached to: MIT's Cheetah Robot Runs Untethered

That article is written as if that crowd invented running using force control. Of course you use force control. Everybody in the field knows that by now. I patented that 20 years ago. The Scout II robot at McGill, developed by Prof. Martin Buehler, used that approach. Buehler went on to become the designer of BigDog, but never got much public credit for it and quit to work for iRobot.

The key to legged running in non-trivial situations is careful management of ground traction. Traction is first priority, then balance, then foot placement. Historically, everybody worried about foot placement first, but that turns out to be backwards. As soon as you get off flat surfaces with good traction, traction control dominates.

The next unsolved problem in that area is not going fast. It's starting, stopping, and turning fast. Most of the legged robots accelerate very slowly, and don't make abrupt high-speed turns. Big Dog starts by trotting in place, then extending the gait out. Starting fast, stopping fast, and turning fast are all facets of the same problem. You have to take one stride using completely different control algorithms than you use for normal locomotion. That's all I'm going to say about this for now.

Comment: Re:So-to-speak legal (Score 1) 417

by dissy (#47914145) Attached to: Comcast Allegedly Asking Customers to Stop Using Tor

I have a feeling the person you are arguing with spends his days
1) eating lead with the word "beef" chiseled on it,
2) drives his car inside the shopping mall and convenience stores to get to the indoor ATMs, and
3) likes to troll handicap people

Since the first action item somehow hasn't killed him yet, that just gives more weight to the rest as an indicator of just how awful of a person it is ;P

Comment: Re:So-to-speak legal (Score 1) 417

by dissy (#47914039) Attached to: Comcast Allegedly Asking Customers to Stop Using Tor

The legal ( and its sound reasoning ) will be sure the first amendment provides you can say pretty much anything you want but it says nothing about you being able to do it in anonymity.

Says Mister DarkOx, if that is your real name...

Since you are out right admitting you are doing nothing but illegal crimes (perfectly sound reasoning once I saw your not-name in your post after all) - you'll need to do much much better to convince me and all of us why we should take the opinions of a criminal to be worth more than a grain of digital salt.

But it was a nice try, pedo :P

Comment: Re:Uber Fresh? (Score 1) 139

by dissy (#47914009) Attached to: Uber CEO: We'll Run Your Errands

It works for Cafe Courier, and they have been doing just that (and making a profit, including off me) since the late 90s.

For the two years Kroger had their peachtree* delivery service, I used the crap out of that! Groceries and pharmaceuticals to your door, and for some even further and right into your fridge.
(Thou I mainly saw that last bit only for older and disabled people. I am just lazy and not wanting to go to the store)

These days I have to hope I get a regular pizza delivery guy that I can uber-overpay for him to stop and get me something extra, and even then if it isn't on or damn close to his normal route I don't even ask.
Plus it sucks dropping an extra $20 just for two fast-food milkshakes that would be like $6 otherwise :/

But hey, sometimes it can be worth it :P

You still have a point about the drones with claw-machine game arms... Once/if those happen, I say let the two options battle it out on price and time! Should be a good show even if a win.

Comment: Re:Spoilers (Score 1) 131

by dissy (#47913821) Attached to: The FCC Net Neutrality Comment Deadline Has Arrived: What Now?

I don't see why this is such a huge deal in the US. Why not both allow so-called "Fast Lanes" and also mandate a high minimum for the "Not-so-fast Lanes" which will prevent ISPs from serving subpar rates to customers?

Sounds great in theory, but in the US the term "broadband" is defined such that the minimum requirement is 128kbps (the speed of a fully utilized BRI line - the original high speed connection)

Since I don't see them successfully raising that first the past hundred or so attempts, the fact they are moving forward on any neutrality issues is pretty much a certainty your plan will never happen here.

In fact given the lack of evidence in either direction, I would naturally assume they will end up changing that min limit to 64k if anything... we suck just that bad :/

Comment: Re:Welp. (Score 1) 265

by dissy (#47913743) Attached to: Ask Slashdot: What To Do After Digitizing VHS Tapes?

I can second that.

A couple years back a week before christmas my uncles place burnt down in the middle of the night.
Everyone always said that because of the historic covered bridge from the road to back where those few homes were, that everyone best not have a heart attack or play with fire because no emergency vehicles could possibly get there...

Fortunately they both got out unharmed - but at that point with no worldly physical possessions except his truck (which I can't say was the bestest idea to go back in the garage to get) and the PJs on their backs.

To this day the things they miss the most are the few old family hand-me-downs, and the massive amounts of photo albums they had amassed.
Including family hand-me-down albums, over a hundred years worth of memories were gone just like that.

As my imediate family is only two people (my mother and her brother/my uncle) - a total of two people asking for computer help is far from problematic for me and so of course I still do.

Somewhere between un-oem'ing his laptops windows install and handing the thing back to him, I set him up an ssh account on one of my servers and a winscp dropbox style icon on the desktop for offsite backup purposes.
But every picture from 1920 to 2009 is now gone and gone for good.

Us "youngins" have a wonderful advantage with digital media that naturally affords us easy copies and easy backups, up to ridiculous extents that simply wouldn't be possible with physical items.

There is no excuse for us not to avail ourselves of them, file format be damned.

In retrospect I now kinda feel bad for the joke I made about the offsite storage thing (long before the fire however)
I told him that machine was "only" backed up to servers in three other states plus a backup server in my basement, but with a slight config change I could add his homedir to be copied to my non-us servers as well - resulting in the possibility of our data out surviving all of us if ww3 happened...

But my point with that is that it is so cheap and easy to fling data around these days that having only one or even two backups is only slightly less painful to hear than someone who has no backups, and the slight time investment most people would need to recover and the relatively tiny cost for something that was literally impossible to do not two generations ago - there is just no excuse not to.

I would even go so far as to say a pirated movie collection would deserve some redundancy right next to personal data like home pictures and movies - and the barriers to doing so are so tiny that they truly are not worth even thinking about at the "yes or no" level.
Only the higher up level of how many copies is worth pondering over (Ex. I don't really feel its worth having a copy of the matrix 2 spread over 8 machines and multiple countries for example ;P )

Comment: Clueless (Score 1) 59

by Animats (#47911665) Attached to: New Data Center Protects Against Solar Storm and Nuclear EMPs

This keeps coming up. The effects of an electromagnetic pulse and a solar storm are completely different. EMP is a big RF pulse with a risetime in the nanoseconds. This is a risk to input transistors connected to external wiring. Twisted pair, coax, and small mobile devices are relatively immune. Fiber optics are totally immune.

Solar storms induce DC voltages across long distances of conductive landscape. This is a risk only to transformers with grounded center taps connected to long transmission lines.

Here are the PJM power grid emergency procedures for geomagnetic events. They had to be implemented for a day two years ago. Almost nobody outside of power grid operators noticed.

Comment: nas4free, raidz2, primary/secondary server, rsync (Score 2) 265

by karlandtanya (#47910967) Attached to: Ask Slashdot: What To Do After Digitizing VHS Tapes?

2 servers are set up raidz2 with 4 disks per server. So about 6-7 TiB of actual storage space.
The servers do dns, mysql, and smb via plugins and a jail.
the primary backs up to the secondary every evening.

All the TVs in the house are really xbmc clients connecting to the SMB shares and mysql.

The most expensive part of it is the 8ea 4T HDDs.
Unless you have 10 people in your house watching different TVs at the same time, you can use real low end computers.
disks are $150 ($120 if you get externals on sale from huevonuevo & open the box). Excellent computer for this is a Dell poweredge T20 ($300).
These T20s have ECC RAM (you want this)
Anyhow 8*150 + 2*300 + a hundred bucks for misc. cables, bootable memory stick, maybe a switch...
Under 2 grand for the whole mess. Put one in your basement and one in your attic. Then you are protected from a flood or a tornado--but not both together.
If your house burns down, though, you're hosed ;).

Upgrade plan is to "destroy" (that's the command...) the zpool in the secondary then change it from raidz2 with 4 disks to raidz2 with 6 disks.
let rsync do its thing, then swap the usb keys with the embedded OS.
Repeat with the old primary which will now be the secondary.
Already tried this once; works no problem. At any given moment I'm tolerant to at least 2 disk failures.

Transportation

3D-Printed Car Takes Its First Test Drive 132

Posted by samzenpus
from the print-and-drive dept.
An anonymous reader points out this advancement in 3D printing. This week, at the International Manufacturing Technology Show (IMTS) in Chicago, Arizona-based automobile manufacturer Local Motors stole the show. Over the six day span of the IMTS, the company managed to 3D print and assemble an entire automobile, called the "Strati," live in front of spectators. Although the Strati is not the first ever car to be 3D printed, the advancements made by Local Motors with help from Cincinnati Inc, and Oak Ridge National Laboratory, have produced a vehicle in days rather than months.

If I have not seen so far it is because I stood in giant's footsteps.

Working...