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The Science of a Bottomless Pit 121

Posted by samzenpus
from the free-falling dept.
StartsWithABang writes It's the ultimate dream of many children with time on their hands and their first leisurely attempt at digging: to go clear through the Earth to the other side, creating a bottomless pit. Most of us don't get very far in practice, but in theory, it should be possible to construct one, and consider what would happen to a very clever test subject who took all the proper precautions, and jumped right in. Here's what you would have to do to travel clear through the Earth, come out the other side, and make the return trip to right back where you started.

Comment: Re:Sigh... Yet another scam (Score 1) 233

by catchblue22 (#49070743) Attached to: Mars One: Final 100 Candidates Selected

To be fair, if you're off by 50% on a $1M project, you're out a couple year's salary for one engineer... if you're off by 50% on a $10B project, you owe somebody an aircraft carrier. You'd be an idiot to not be conservative on pricing things when they are that expensive, unless the contract covers development costs.

You do know what cost-plus contracting is, don't you? In essence, the company says, the project will cost what we say. And then add 20% profit on top. The government will then put auditing systems to track almost every purchase. However, that doesn't stop the company over-designing the system, or choosing a design that costs far more than it should. Or hiring layers upon layers of middle managers who do next to nothing. It costs what it will cost. And then Lockmart gets 20% profit on their already inflated prices.

This is why aerospace is so expensive in America. Lockmart and Boeing both rely on cost-plus financing. SpaceX does not. They give price per performance. Price to launch. Price to design and build. They only get paid if they do what they say.

Comment: Re:Sigh... Yet another scam (Score 1) 233

by catchblue22 (#49067673) Attached to: Mars One: Final 100 Candidates Selected

I agree that Mars One sounds fishy. The lack of technical details is suspicious.

I think we can go to Mars. I think we can build the technology. And I don't think that Lockmart and Boeing (through NASA) can do it, because their reflexive position is to magnify costs. I suspect that Elon Musk is the most likely force that will push us to Mars, if only because his obsessive motivation towards that goal causes him not to magnify costs, because he realizes that excessive costs will make his goal impossible. I think that the government would do well to divert some of the funds that were headed towards Lockmart/Boeing towards SpaceX instead. They will get better value for their investment.

Comment: Re:lagrange point (Score 4, Informative) 75

At this point, the pull from the earth will cancel out the pull from the sun, and the satellite will effectively stay positioned exactly between the earth and sun as the earth rotates around.

Not quite. From NASA:

The Lagrange Points are positions where the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them.

Lagrangian Point 1 (L1) is located on the line between the Earth and the Sun. At L1, the opposing gravitational force from the Earth partially cancels the force from the Sun, reducing the overall centripetal force. In orbital mechanics, the periods of Sun orbiting objects increase with increasing radius, due to the decreasing gravitational force (lower force, lower acceleration, lower speed, increasing circumference). Because the satellite at L1 feels a weaker centripital force than it would normally experience at that solar orbital radius, it can orbit the Sun at a period of 365.25 days, in spite of being closer to the Sun than the Earth. Thus it maintains its relative position between the Sun and the Earth.


MIT Randomizes Tasks To Speed Massive Multicore Processors 63

Posted by samzenpus
from the greased-lightning dept.
itwbennett writes Researchers at the Massachusetts Institute of Technology have created a data structure that they claim can help large multicore processors churn through their workloads more effectively. Their trick? Do away with the traditional first-come, first-served work queue and assign tasks more randomly. The SprayList algorithm allows processors with many cores to spread out their work so they don't stumble over one another, creating bottlenecks that hamper performance.

Comment: Re:How did they run out of fluid? (Score 3, Informative) 248

by catchblue22 (#48832873) Attached to: SpaceX Landing Attempt Video Released

Hydraulic systems are in a loop, with the "spent" fluid recirculating back to the reservoir. How did they "run out"?

Where did the fluid go?

The system is an open hydraulic system. Closed systems require tanks and pumps which carry a mass penalty. They only need the system to function for about 4 minutes. Why bother with a closed system when the functioning period is so short. They will increase the amount of fluid by 50% so this shouldn't happen again. All in all a nearly successful experiment.

Comment: This test was a successful failure (Score 5, Informative) 248

by catchblue22 (#48832677) Attached to: SpaceX Landing Attempt Video Released

This was the first time SpaceX had flown the new grid fin control system on a real first stage under real conditions. They did not know exactly how well the grid fins would behave. As it turned out, the grid fins had to move more than they expected during the descent (or the forces were larger than they expected), so they ran out of hydraulic fluid 30 seconds before landing. This is similar to an airplane losing control of its elevator just before landing. The fact that the rocket reached the barge and that its vertical speed was reasonably slow (certainly not 100m/s) indicates the resiliency of their systems. They are putting 50% more fluid into the system, so this shouldn't happen next time.

I think this video is epically cool. I can watch it again and again. Simply awesome.

Comment: Re: Minor setback (Score 1) 213

by catchblue22 (#48782031) Attached to: SpaceX Rocket Launch Succeeds, But Landing Test Doesn't

...SpaceX being a private entity, they just have a lot of paid PR people to drum up support.

I'm sure this is true. And their enemies in the military-industrial complex (Boeing/Lockheed Martin/ULA) have deep pockets to hire propaganda companies to slander SpaceX. In fact, they already have. Look at the client list of this PR (propagandistic relations) company called Shockey Scofield Solutions.

Reading between the lines, I think this is a company that specializes in greasing palms/pulling levers in Congress and the Senate, as well as constructing sophisticated internet campaigns that include releases to key susceptible news outlets/columnists and hiring fake posters to post on certain widely read comment boards.

Comment: Re:Minor setback (Score 1) 213

by catchblue22 (#48781733) Attached to: SpaceX Rocket Launch Succeeds, But Landing Test Doesn't

This was the first flight with the maneuvering grid fins. The fact that they were able to bring the rocket to the barge with an untested maneuvering technology is quite remarkable. It speaks volumes to their modelling software. I can speculate that because of the untested grid fins, the maneuvering was not quite as precise as needed and the rocket engines had to do a large slew just before landing, which burned up too much fuel. My speculation is that the fuel ran out just before landing.

The fact that the rocket arrived on target and with low enough speed that it didn't crater the barge is quite something, and speaks to the near success of this test.

Comment: The problem is fanaticism (Score 1) 1350

by catchblue22 (#48757433) Attached to: Gunmen Kill 12, Wound 7 At French Magazine HQ

In my opinion, the real problem is fanaticism. During the Enlightenment, the words "enthusiasm" and "fanaticism" both had very negative connotations. To be an "enthusiast" meant that you were someone who passionately believed in an idea without a rational reason. If you were a "fanatic", you were willing to kill for your "enthusiasms". In relation to this, the French philosopher Voltaire once wrote: "Those who can make people believe absurdities can make them commit atrocities." To believe that drawing a cartoon of any particular person merits a death penalty is clearly absurd.

Comment: Re:Tim Cook is an MBA (Score 4, Informative) 598

by catchblue22 (#48742979) Attached to: Tumblr Co-Founder: Apple's Software Is In a Nosedive

He may well have made the right decision... or he may have just made the decision to use a 'mature unix' foundation, because it was basically just reusing his baby from NeXT (and we all remember how that company was taking the PC world by storm right? =scoffs=)

Jobs personally spearheaded NeXT with a small group of engineers. He knew exactly what he was doing. I remember him talking about NeXTStep and he openly boasted about its portability and high degree of hardware abstraction. He tried to sell this idea to other software companies but no one bit. It is no coincidence that OSX is so portable. It is by design.

You seem to imply that if someone is not a coding ninja, then they have nothing to contribute to software. I strongly disagree with this. Job's strength was that he saw the broad arcs of software design. He realized that simplicity and cleanness was key to good software, to maintainable software, to portable software. He realized that if software was not written properly at its earliest stages, it would remain inherently flawed no matter how much it was maintained.

It is no coincidence that Jobs made his best software when he was working with a small team of engineers. This is how he created NeXT. And this is how he created the original iPhone.

As for your comment on NeXT, well it became OSX, so it was in the end extremely successful. And another little thing came of of NeXT workstations. Tim Berners Lee first implemented hypertext on a NeXT workstation...that was the beginning of the web as we know it today. If you had every used an NeXT workstation (as I did), you would realize that the cleanness and elegance of the OS likely had a lot to do with Tim Berner Lee's invention. There was simply nothing like it at the time.

"Being against torture ought to be sort of a multipartisan thing." -- Karl Lehenbauer, as amended by Jeff Daiell, a Libertarian