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SpaceX Rocket Launch Succeeds, But Landing Test Doesn't

ClayJar Re:No KSP at SpaceX? (213 comments)

The SRBs from Shuttle launches were indeed reused... after a fashion. Each booster was four segments. After each flight and recovery, the boosters were disassembled and the segments renovated and reloaded. The segments were not kept together as a set, so each SRB used in a launch would have four segments each with their own history. (This was expressly noted on NASA TV during each launch, with comments about the oldest and newest segments on the flight and so on.)

As for SpaceX, early Falcon 9 flights had parachutes on the first stage, but the stages did not survive reentry (much less make it all the way to landing). Since you can not land anything large on Mars with parachutes, SpaceX would have eventually had to work on hypersonic retropropulsion, propulsive landings, and so on; they merely pivoted away from the parachute "dead end" and went straight to propulsive recovery with Falcon 9 v1.1.

about three weeks ago

Elon Musk Addresses New Jersey's Tesla Store Ban

ClayJar Re:Shooting themselves in the foot (229 comments)

"Our stores will transition to being galleries, where you can see the car and ask questions of our staff, but we will not be able to discuss price or complete a sale in the store. However, that can still be done at our Manhattan store just over the river in Chelsea or our King of Prussia store near Philadelphia."

Sales over the border? Already ready. Collecting tax revenue? If NJ is anything like my state, they'll collect that when you register the vehicle in NJ. The state isn't going to be out much money, but the dealers are protected by the politicians who get their campaign contributions, and neither has to give a hoot about inconveniencing the people. (The people inconvenienced weren't going to buy from the dealers, so no money lost there, and they aren't numerous enough to make a dent in the elections, so that's all fine and dandy, too.)

about 10 months ago

ISS Astronauts Fire-Up Awesome 'Cubesat Cannon'

ClayJar Re:Won't they hit the ISS on a future orbit? (52 comments)

They're launched from the nadir side in a nadir-aft 45-degree direction to prevent collision with the ISS. That imparts a small negative delta-V (with insertion velocity between 1.1 and 1.7 m/s), so their orbit would begin just slightly below the ISS. Additionally, one of the requirements for CubeSats launched from J-SSOD is that they have a ballistic coefficient of 120 kg/m^2 or less. This means that their orbits will decay faster than the ISS orbit, precluding any potential for collisions over time.

(The life expectancy on orbit of a CubeSat launched from J-SSOD is something like 100-150 days, depending on orbital parameters as of deployment, solar activity, etc.)

about a year ago

Come Try Out Slashdot's New Design (In Beta)

ClayJar Can we please make it narrower? (1191 comments)

I'm *so* tired of having slashdot use the entire width of my browser. I've been pining for expansive areas of whitespace for years!

about a year ago

The Grasshopper Can Fly Sideways

ClayJar The first stage is suborbital. (127 comments)

Heat shields are the efficient way to slow from orbital speeds for reentry (e.g. the Shuttle), but conveniently for recovery the first stage isn't orbital. Grasshopper is basically a modified Falcon 9 first stage, and the goal of the testing is recovery of the first stage of Falcon 9-R, which is much easier than reentry from orbit..

We're not talking single stage to orbit here, and recovery of the second stage would certainly involve a heat shield. The first stage is a different animal. SpaceX seems to be intending to use a boost-back trajectory concept. I look forward to seeing how that works. (The controlled water "landing" attempt will be something to see, too, of course.)

about a year and a half ago

Gubernatorial Candidate Speaks Out Against CAS

ClayJar The Last Paper (in free verse) (121 comments)

They wrote a story

typeset in the form of a seventh-grade paper

where only the page count matters.

But the trick never worked

as the teacher docked them anyway.

It was worth one more try.

about 2 years ago

Will Tablets Kill Off e-Readers?

ClayJar Leatherman killed the tool market. (333 comments)

Leatherman killed the tool market when it came out. Why buy a single-purpose tool when you can get many more features for a little bit more money?

Sometimes having something that *doesn't* slice, dice, and julienne fries is the better choice. I mean, sure, I could do many small repairs using just a leatherman, but a nice set of wrenches and drivers makes working on my bike *much* nicer. Or how about crescent wrenches (or shifting spanners, as the case may be)? You can handle all variety of nuts, bolts, and fittings. SAE, metric, square, hex? All are open to you. Yet anyone who spends much time working on mechanical things knows that a crescent wrench, while convenient, is often vastly inferior to a good set of wrenches.

When I'm out on a ride, I carry a small multitool that *does* do a bunch of things in one small, inexpensive, unobtrusive package, just as when I'm out and about, I can get some reading done on my Nexus 7. The Nexus 7 is convenient, but if I ever broke my e-ink Kindle, I'd have a replacement ordered that very day. E-ink readers are basically designed to fill the niche of "electronic trade paperback for avid readers". They fill that niche exceedingly well, and avid readers are a renewable resource.

more than 2 years ago

Why The Hobbit's 48fps Is a Good Thing

ClayJar Awkward... (599 comments)

Actually, I was thinking more along the lines of the Hogfather (specifically from the movie).

While I enjoyed this first Hobbit movie, I found the Radagast scenes awkward (like an old family photo with too-large glasses and sisters with poofy bangs). Radagast and his bunny sled seemed too much like something right out of Discworld, which would be delightful except that combining Discworld and Middle Earth yields a very large impedance mismatch.

more than 2 years ago

I reach my workplace, primarily/typically, by:

ClayJar Intentionally once for me. (566 comments)

I can't speak for his experience, but I can tell my own story about being intentionally run down by a motor vehicle.

It was a dark and stormless night (hehe). To be specific, it was late on the Wednesday night before Thanksgiving, and I was riding across town to drop some goodies off at a friend's place. We have virtually no bike paths, and those we have tend not to be connected to anything, so it's all road riding here. The road was one of those five-lane jobs (two in each direction and a suicide left in the middle), and traffic was extremely sparse. (We're talking maybe half a dozen cars total at the busiest intersection along the route.)

When that light with maybe half a dozen vehicles turned green, I rode on and was passed by the cars that had been waiting. Not far down the road one of them, a pickup truck, moved into the suicide left lane as if he was going to turn into some apartments, but he didn't immediately complete the turn in spite of no oncoming traffic. As I approached (two lanes away, riding near the white stripe on the outside edge of the outside lane), all of the sudden I saw his white reverse lights come on. He floored it and cranked the wheel around, backing hard across both lanes in my direction and continuing all the way into a doctor's office parking lot.

Had I been expecting it, I could likely have quick-turned a bit harder to avoid the hit, but you don't expect someone to try to injure or kill you. So, my turn wasn't quite hard enough, and I went into the side of the pickup as my bike went down. The guy continued back, crushing my front wheel, then paused for a moment before peeling out and driving off. My reaction wasn't quick enough to avoid the assault, but it was just fast enough to let me escape with a broken bike and only minor injuries (scrapes and bruises, mainly).

So, a pickup truck stops in the middle of the road for no reason, waits for the bike, throws it into reverse, and floors it across both lanes and into a parking lot. Can't get much more blatant than that. Moments after the guy drove off, a car pulled into the parking lot to check how badly I was injured. He had seen the whole thing and was virtually dumbfounded. He had never seen something like that in his life, he said, although I'd hope most people would fall into that category. I got a very close and intimate look at the pickup truck (obviously). I had a witness who saw the whole thing. So, why didn't anything come of it? The guy had an illegally obscured license plate. Without being able to ID the vehicle, the police would be happy to take a statement from me, but that was the extent of it.

The vast majority of car/bike incidents I've had are simply oblivious drivers, e.g. passing too closely or returning to your lane before the back of their vehicle has passed you. Even antagonistic drivers are often so due to ignorance, e.g. "Get on the sidewalk!" (which is not only dangerous but also expressly against the law here). Still, every so often you get a psychopath. What can you do (other than mounting a few Go Pro cameras around your bike to gather and preserve evidence)?

more than 2 years ago

Nearly 150 Companies Show Interest in the Tech Love Boat

ClayJar Re:A tsunami in deep water is a non-event. (332 comments)

You are correct. A ship can take much larger waves directly into the bow than it can take abeam. It's perfectly logical if you think about it. The bow is designed to plow into the water, so it'll deflect the wave energy better, and designers know storms will come, so they design to some extent or another for waves breaking over the bow. Waves running directly into the side have a large surface to work on.

Additionally, consider the simple geometry. A ship is going to be much more stable in the pitch axis (where it is a nice, long lever) than in the roll axis (where it's much closer to a round log). Tipping a ship end-over-end would require something more like a Michael Bay movie, while capsizing it by rolling it over requires much less force.

The images I've seen of this ship show something much more like a floating rig platform than a plain old large yacht. It has a long axis, but it's much wider than a "normal" ship. That being the case, it would have more stability in the long axis, but it should be stable enough in the short axis. You *could* just go ahead and build a platform instead of a ship, with deep ballasts well below wave action attached by legs to the main platform well above the waves, but that expense, inconvenience of access, and greatly reduced mobility is apparently undesirable.

more than 2 years ago

Nearly 150 Companies Show Interest in the Tech Love Boat

ClayJar A tsunami in deep water is a non-event. (332 comments)

Off-shore in deep water, there is absolutely no danger whatsoever from a tsunami. A tsunami is only a problem as it reaches shore, as it's there that the very long period waves just keep coming and coming and piling up water. In deep water, there's just a very, very long swell of minuscule amplitude.

Storm waves are vastly more significant. Their period is short enough and their amplitude great enough to potentially cause significant damage to oceangoing vessels. Considering also the occasional rogue wave (a wave or short set of waves at several times the amplitude of the prevailing wave conditions at the time), and having lifeboat/evacuation drills every so often would be best practice. At least the area in question is outside the hurricane belt, so hurricane evacuations (such as those from Gulf of Mexico oil rigs) shouldn't be required.

more than 2 years ago

SpaceX Launch To International Space Station Delayed For Code Tweaks

ClayJar Re:Launch window (97 comments)

The Space Shuttle had a launch window of approximately plus or minus five minutes from in-plane, but for the Falcon 9/Dragon COTS-2/3 launch to ISS, they have an instantaneous launch window. From the comments on the COTS-1 webcast, it sounded as if Dragon flights to ISS would have instantaneous launch windows, but I have no data to know whether this is merely a constraint for the initial flights or a constraint for all future COTS/CRS launches.

For the April 30th window (which will not be used), there was also an instantaneous launch window on May 3rd (with the days between those two blocked by ISS orbital constraints, I believe -- SpaceX has additional requirements for the test launch and recovery than for an operational launch). The next set of instantaneous launch windows would be May 7th and May 10th (with the days between blocked), but the May 10th window would mean that in the event of an aborted docking, there would be only time for one additional attempt before Soyuz conflicts (which would push the Dragon docking beyond May 17th, which may or may not be possible depending on fuel constraints, which I am not privy to).

Regarding the failure probabilities, from last week's press conference, it sounded as if SpaceX is the primary driver of mission assurance for this flight, i.e. they want to be sure they have as many of their waterfowl properly queued as possible. A cynic might note that if they don't get it right this time, it costs NASA nothing and SpaceX the full cost of another attempt. Someone with a brighter outlook would likely just say that if *everyone* on earth were watching you (most hoping you'd succeed, some hoping you'd fail), you'd *really* want to double-check everything one last time.

more than 2 years ago

How Many Online Aliases Do You Use?

ClayJar Um, perhaps we're not? (315 comments)

Sure, it may be a bad idea to disclose things like the actual number of aliases one has. On the other hand, what's wrong with disclosing the reported number of aliases one has? Nobody ever said we couldn't omit the secret set from our count, now, did they?

(To borrow a line from "Beethoven's Last Night" by Trans-Siberian Orchestra: "My dear, he's the devil. He lies.")

more than 2 years ago

Failures Mark First National Test of Emergency Alert System

ClayJar Cox Communications (451 comments)

I was watching the test on a friend's Cox Communications cable service, and they also switch to a shopping channel (cable channel 8) for emergency alert activations. Their cable system apparently is incapable of showing the alert on all the (digital?) channels, so they simply show it over analog shopping channel 8 and have a system in place to switch everyone to that channel automatically whenever an alert is triggered. It's a bit annoying if a test is scheduled during, say, an important football game... er... episode of Mythbusters... whatever. On the other hand, it is even more jarring than the alert tones, so you'll certainly know something's afoot.

If you have one of their Motorola digital cable boxes, when it goes into emergency alert mode and auto-switches to analog shopping channel 8 for the message, the front clock display changes to "EAS" as well. If you're suddenly watching the shopping channel and "EAS" is displayed on the cable box *and* you have the wonderfully annoying (and intentionally so) alert tones, you *should* be able to figure out that now's the time to read or listen. At least, that seems to be the general idea.

I did notice that I didn't get the alert over cable until after I'd finished watching it on OTA TV (and chatting about it afterward), so chalk up a minute or two of additional latency to the cable company.

more than 3 years ago

Mathematically Pattern-Free Music

ClayJar Random is trivial, as the TEDx Talk explained. (234 comments)

Actually, as was explained in detail in the video, random is easy. Completely devoid of repetition is vastly more difficult. This was not simply random, this was mathematically non-repetitive. Using random numbers outside of the audible range would not necessarily preclude repetition, and using random frequencies is atonal sound, not tonal non-repetitive "music" as was the intention of the piece.

Completely random is trivial. Mathematically-sound aperiodic and repetition-free is a completely different kettle o' fish.

Note that the composition used the 88-tone chromatic scale of the standard piano keyboard. Without that constraint, you could make a much longer atonal composition, of course, but the point of the exercise was to use discrete mathematics and music to create a tonal composition completely devoid of repetition.

more than 3 years ago

Security Researchers Crack APCO P25 Encryption

ClayJar There are FOUR lights! (37 comments)

I was afraid you were going to tell me there were five researchers, but you don't even *look* Cardassian.

more than 3 years ago

Germany Builds Encrypted, Identity-Confirmed Email

ClayJar Dibs on the nickname! (188 comments)

From the sound of it, it'll almost inevitably end up costing money. With that in mind and by the powers vested in me by absolutely nobody in particular, I hereby dub it "feemail".

(One *could* say that it is supposed to be a kinder, more respectable alternative to the rough-and-tumble wild west of existing (e)mail, but then there are those who think it's just a prettier version that will inevitably cost a bunch of money.)

more than 3 years ago

Compared to a year or two ago, I find I'm printing ...

ClayJar Water, water, everywhere. That is why I print. (252 comments)

I would *love* it if I had a viable alternative for my primary printing purpose, but alas, there is none. You see, I am now a scuba instructor (in addition to my real job), and there's really no way to carry and use a netbook, tablet, or such underwater (and I don't mean just in the shallow end of a pool).

I picked up a small black and white laser printer (as toner is *absolutely* impervious to running), a pack of very heavy high-quality paper, another pack of card stock, and plenty of hot lamination supplies. When I need something like a class roster, rental equipment assignment sheet, or the like, I print it on both sides of heavy paper and laminate it. (The same thing is on both sides, so no matter where it ends up at the pools, springs, or boats, it's always visible and convenient.) If it's something like a "lesson plan" pick-sheet, I'll print it on card stock, nip a corner, laminate it with thicker plastic, and punch the nipped corner for attachment to a trigger snap. Doesn't last forever, but it'll certainly last more than a few classes, and I'm always optimizing anyway (which would require a revision regardless).

Now, this isn't to say that I'm paper-centric. The class rosters and gear sizes and assignments get typed into an online form, and at a click, they are sorted and arranged into three tables (by student name, by wetsuit number, and by scuba gear number), and a PDF is dynamically generated with maximized text size given the class size. I can login and change anything at any time, and I can always reprint. The paper is only a necessary convenience (and will not cause me to cry if a wayward student sets a scuba cylinder down on top of it, hehe).

Of course, things like student exams are required on paper for record-keeping purposes, but I count those as the students printing-by-proxy. (I *did* completely redesign the multiple choice answer sheet to be *much* more user-friendly. The existing one distributed with the instructor materials is, get this, type-written with single-spaced rows of capital letter O for the answers. I get much lower missed-response averages with an alternating-row shaded, letter-containing oval, sets-of-five answer sheet.)

more than 3 years ago

Google Wants To Take Away Your Capslock Key

ClayJar NumLock off is for remapping! :D (968 comments)

I remapped the non-NumLock keypad to the various keys to control my TiVo in SlingPlayer. Zero is the 30-second skip button, the decimal point is back-skip, nine and six page up and down, five and two play and pause, eight is the TiVo button, and SlingPlayer mute and system mute round out the rest.

It's actually quite a nice system (much nicer than Control-F, Control-B, and other seemingly randomly-chosen keys). I use AutoHotKey to set focus to the SlingPlayer window and send the key or keys, so they work regardless of which window had focus. Makes it trivial to skip commercials, but I retain the use of the numeric keypad.

more than 4 years ago

How Long Until We Commonly Use Flying Cars?

ClayJar My kingdom for a Newton! (606 comments)

I hate to point you out in Hollywood physics, but I believe you have caught yourself one Newton short of a fig idea there. ;) (Everyone misspeaks once in a while, so I do not begrudge you the error.)

The friendly name you give the force is irrelevant. Calling it "lift", "thrust", or "general uppityness" makes no difference to the physics. There is the force due to the acceleration of gravity on the mass of the aircraft, and there must be an equal and opposite force acting on it in order for there to be no net acceleration. This upward force can only come from an equal and opposite force acting on the air in which the aircraft is hovering.

Obviously, with force being the product of mass and acceleration, you can trade off between those. You can have a relatively small mass of air greatly accelerated in a downward direction, or you could have a relatively large mass of air accelerated less.

For a helicopter, the longer the blades, the more air on which they act, and the less acceleration is therefore necessary in order to yield the same force. To go even more extreme, consider a Harrier. The Harrier has a very narrow column of air *greatly* accelerated to yield the required lift, while a helicopter has a much larger column of air and needs not accelerate it nearly so drastically.

Being impinged upon by the jet blast of a hovering Harrier is certainly going to be more "windy" than being in the rotor wash of an equivalently massive hovering helicopter, but it has nothing to do with "lift" versus "thrust". It has solely to do with the mass of air acted upon and the acceleration thereof.

more than 4 years ago



Actual Mid-Air Collision In Pictures

ClayJar ClayJar writes  |  about 7 years ago

ClayJar writes "It's not every day a mid-air collision is caught in pictures, but Aero-News Network recently published an article with precisely that. A photographer happened to be in just the right place to catch two small planes in a classic high-wing/low-wing collision, and the resulting nine photos show quite well how such a situation develops. If you're an aviation enthusiast or just curious in general, you'll want to see the brief article and photos. (Sadly, no YouTube video was included, but both aircraft did land safely.)"
Link to Original Source


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