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Comment: Re:Unity next (Score 1) 468

by bledri (#49548015) Attached to: Ubuntu 15.04 Released, First Version To Feature systemd


Problem solved. Simpletons like me and my family can use the dumbed-down nursery-school, colour-by-numbers default desktop interface. Clever, technical people can type a few commands starting with 'sudo apt-get install'. I don't get why everyone isn't happy?

Oddly enough, some people want to spend all weekend customizing their desktop while simultaneously resenting the fact that they "have to."

Maybe it's mostly an ego thing. Building oneself up by looking down on people with different strengths and interests. Or now that I think about it, I bet it's mostly that people need something or someone to blame for their own frustrations. "I'm not happy, it must be your fault!"

Comment: Re:Video from the barge (Score 1) 113

by bledri (#49490423) Attached to: An Engineering Analysis of the Falcon 9 First Stage Landing Failure

I'm not trying to fix the wrong problem, I'm trying to add a backup for the fix. Shit happens. Parts will fail, valves will stick, unexpected winds or waves will occur.

I thought the fact that the primary goal was to correct the problem that caused the excessive lateral velocity was so bloody obvious that it didn't need saying, but I guess I forgot I'm on the Internet. The purpose of my idea was not "fuck it, fixing a little problem is hard, let's do something much more complicated", it's "shit happens. What can we do to survive the likely error modes?"

And I stand by my response, it's better to reduce the likelihood of shit happening. There are ways to reduce sticton and there are ways to handle it better when it happens. Trying to fight an oscillation induced by a lag/overcorrection of a main engine with a thruster is a losing battle. If the thruster is up top it will just rotate the stage around the center of mass (which is really what a thrusters job is, to orient the stage. Not move it through space laterally.) If you look at the thruster firing during the failed landing attempt, it's trying to stop the rotation of the stage. It is not trying to stop the stage's "lateral motion." The direction it's firing, a crazy powerful thruster that could have made a difference would have added to it's lateral motion right off the barge. And it would have driven the opposite leg into the deck by using the already collapsing leg as a pivot point.

To some situations the correct response is to do less, not more.

Comment: Re:Video from the barge (Score 5, Insightful) 113

by bledri (#49489699) Attached to: An Engineering Analysis of the Falcon 9 First Stage Landing Failure

So, I asked this in the last thread but the discussion there was already mostly dead: what would it cost (presumably mostly a matter of weird) to upgrade the nose thrusters? These are cold-gas (nitrogen) thrusters, and I can't imagine they have a lot of power.

The Dragon uses hydrazine-based "Draco" thrusters for its RCS system; ...


You, like many people, are trying to solve the wrong problem. Fix the over-correction and there is no need for rocket powered thrusters in place of the cold gas thrusters. Fix the root cause, don't mask it with a heavy/expensive kludge that will come with a host of it's own failure modes.

Comment: Re:I wonder why he bothers... (Score 4, Insightful) 113

by bledri (#49489685) Attached to: An Engineering Analysis of the Falcon 9 First Stage Landing Failure

In a later tweet that was subsequently withdrawn, Musk then indicated that "the issue was stiction in the biprop throttle valve, resulting in control system phase lag."

Anything he leaves for more than 0.5 seconds is going to be reported, retweeted, screenshotted and several articles posted. Just google "musk stiction biprop" and you get plenty hits, no real "undo" button for such a public figure.

He's tech savvy enough to know it's not scrubbed from the internets nor the collective consciousness. This just seems to be how he uses twitter. He regularly tweets things he leaves up, but he also uses twitter to have conversations with people and then he deletes those tweets after the conversation is over. One theory is that he likes a "clean" twitter history. But who the hell knows?

Comment: Re:Not 'close' (Score 1) 342

You need three conditions: 1. Hit the target location 2. Minimal vertical velocity 3. Vertical orientation. They met #1. It was coming in tilted (for varying amounts of tilt), and way too fast.

It did not come down way too fast. It just overcorrected at the end. It's called a hover slam (unfortunately) and it's all about using the minimum amount of fuel and dealing with the reality that even a single engine throttled down to 40% has a T/W > 1. They are extremely close to successful landing a first stage booster used to deliver a payload to orbit. Only experimental rockets have done this before (landers don't count, they are tiny in comparison. Amazing feets but a different kettle of fish.) This is a big deal. This is going to make spaceflight cheaper.

Comment: Re:One second launch window? (Score 1) 77

by bledri (#49465811) Attached to: SpaceX Launch Postponed

I thought I heard the commentator mention a one second launch window. Did I hear that right?

Yes, that's correct. Technically I think it's actually a one minute launch window, but there is not really any scenario where that matters. This is because if there is a launch hold the clock cycles back to T-13 minutes. There is no practical way to have a hold at T-13 or less, resolve the problem, and then target a new launch time within that one minute window. So the launch targets the specific second which optimizes rendezvous with the ISS.

They also call this an instantaneous launch window.

Comment: I am curious what ULA's rocket will look like (Score 1) 78

by bledri (#49451903) Attached to: SpaceX To Try a First Stage Recovery Again On April 13
I am admittedly a fan of SpaceX. But ULA does employ smart people too and I'm really curious what they will propose. While I hope SpaceX is successful and I think they will eventually work through any issues, it's good to have people exploring different approaches and possibilities. I'm assuming it will be a less expensive (than Atlas V), methane powered (via Blue Origin engines), expendable rocket leveraging modern production techniques. But the question is "how low can they go" price wise.

Comment: Re:Wouldn't be a problem for Shuttle or DreamChase (Score 1) 78

by bledri (#49451889) Attached to: SpaceX To Try a First Stage Recovery Again On April 13
I wish Slashdot had an edit capability. It could keep back links to older versions for context to responses. But I just reread this and it's too cranky. Sure, I should have fixed that before I hit submit, but this being human thing seems to be an error prone endeavor.

Comment: Re:Wouldn't be a problem for Shuttle or DreamChase (Score 2) 78

by bledri (#49451873) Attached to: SpaceX To Try a First Stage Recovery Again On April 13

Instead of trying to use Apollo-era designs, how about using something that is designed specifically to fly itself down? The Shuttle and DreamChaser addressed this problem quite well. Piloting a can doesn't work too well when you're going downwards.

When sanity prevails and Shuttle-like designs come back, perhaps space travel will improve. Until then, it's 1960's rehashes all around.

No production first stage has every landed propulsively, so they are not going backward to something that was done before. The Shuttle was more "refurbished" then reused. The main fuel tank was discarded. The booster cases were fished out of the water (how modern) and basically rebuilt. The main engines were removed after each flight and rebuilt. The tiles painstakingly inspected and repaired. It was a technological marvel but a financial disaster. The Dream Chaser is just the payload, not launch system. They planned to launch on an expendable rocket. So your examples are all non-sequitors, not "how to do it right."

"Flying back" is not really an option for a first stage booster. You'd need to add wings (more weight and drag, or complex mechanisms) and you'd need to add some sort of heat shield (more weight.) Propulsive landing requires more fuel (weight). The reentry burn itself acts as the primary thermal protection system (counterintuitive, but true.) It's a very elegant solution for recovering the entire first stage for reuse. And it's ridiculous that no major aerospace company was willing to pursue it. (There was the DC-X experimental rocket, but that was a government funded experiment which McDonnell Douglas dropped as soon as the "cost plus" gravy train left the station.)

Now if you love wings, then the right way to do that is probably something like Skylon, but it's a long way from flying and SpaceX is already forcing launch prices lower.

Comment: Re:What SHOULD have happened... (Score 1) 629

by bledri (#49451791) Attached to: Florida Teen Charged With Felony Hacking For Changing Desktop Wallpaper

OK, I hate our draconian "tough on crime" bullshit and ridiculous "cyber crime" laws. But the summary left off some important information. He'd been busted for this before (WTF school, change your passwords) and:

Green was released on Wednesday from Land O'Lakes Detention Center into the custody of his mother. He'll likely be granted pretrial intervention by a judge, sheriff's detective Anthony Bossone said. Green also received a 10-day school suspension. It's unclear if he'll return to Paul R. Smith to complete the school year after the suspension.

So basically their just giving him a good scare.

Comment: Or we could do something useful instead ... (Score 1) 216

by bledri (#49442759) Attached to: Senate Draft of No Child Left Behind Act Draft Makes CS a 'Core' Subject

This is a really stupid idea. Most people never have to code. First, we don't need it. And second, this will not lead to having more software engineers, this will institutionalize "programming sucks" because now schools will be forcing it on people in a way that turns them off to programming. I'm serious.

If you want to make the world a better place, then add a small mix of logic, critical thinking and basic behavioral economics to the core. Coding is not nearly as important of a foundational skill as getting a clue how to think and how bad we are at it.

Comment: Re:Indiana and say Saudi Arabia are not the same (Score 1) 653

by bledri (#49417605) Attached to: Carly Fiorina Calls Apple's Tim Cook a 'Hypocrite' On Gay Rights

No matter how many times it is repeated, there is no separation of church and state codified in the US Constitution or any state constitution.

Historically, the Supreme Court disagrees, from :

Jefferson's metaphor of a wall of separation has been cited repeatedly by the U.S. Supreme Court. In Reynolds v. United States (1879) the Court wrote that Jefferson's comments "may be accepted almost as an authoritative declaration of the scope and effect of the [First] Amendment." In Everson v. Board of Education (1947), Justice Hugo Black wrote: "In the words of Thomas Jefferson, the clause against establishment of religion by law was intended to erect a wall of separation between church and state."

Comment: Re:Indiana and say Saudi Arabia are not the same (Score 1) 653

by bledri (#49416273) Attached to: Carly Fiorina Calls Apple's Tim Cook a 'Hypocrite' On Gay Rights

No matter how many times it is repeated, there is no separation of church and state codified in the US Constitution or any state constitution. This verbiage is lifted from a letter that Thomas Jefferson wrote to a church to assuage the church's fears that congress would prohibit their free exercise of conscience. Anyone who believes that the founders intended an atheistic system of government simply has no idea what they are talking about. Every single president in our history has invoked the blessings of heaven on our country in their inaugural address.

Yes, Jefferson was trying to assuage the fears of Baptists, Presbyterians, and Methodist among others. And many of the "Founding Father's" were Deist's. And they all knew that giving government religious authority (and, conversely, giving religion authority over government) was a Really Bad Idea (TM). So they very much intended a secular government that did not favor any religion. In other words, they wanted a separation of church and state.

The Jefferson letter, the Treaty of Tripoli, and many other writings of the time are important because the Bill of Rights is not a computer program that can simply be executed. It is a human text that needs context to have usable meaning. The Supreme Court always has to interpret the Constitution. When people agree with their interpretation, then they think the Court is doing a good job. When they disagree, the think the Court is being "activist."

Comment: Re:Good God... (Score 0) 383

by bledri (#49400605) Attached to: Why the Framework Nuclear Agreement With Iran Is Good For Both Sides

It's really hard to get a good deal when your leaders are negotiating for the other side. This deal is exactly what Obama wanted for his friends in Iran. He doesn't care which sect of Islam wins, as long as Islam wins. He's a traitor.

OMG. Are you taking the "Obama is a secret muslim" bait? You realize it's April 3rd, right? You should take a breath and argue history and policy rather than regurgitate the stupidity of talk radio ideologues that exists solely to sucker you in with mindless anger while they laugh all the way to the bank.

Thus spake the master programmer: "When a program is being tested, it is too late to make design changes." -- Geoffrey James, "The Tao of Programming"