From the SpaceX filing, "if a maneuver was needed, typically a single in-track burn would be conducted to reduce collision probability". So, a slight prograde or retrograde burn which will slightly raise or lower the orbit. This would, of course, not just adjust the height of the orbit but also the timing, resulting in a reduction in the probability of a collision. Also, in case you might wonder, with SpaceX's avoidance system, "maneuvers occur approximately 12 hours before the predicted closest approach of the satellites."

(And of course, a retrograde burn would speed you past the potential conjunction point earlier, and a prograde burn would slow you down. Orbital mechanics is fun.)

So, if you somehow block the DNS lookup, the cert is good? If you wanted to include DNS as a validation mechanism, it would seem better to require an affirmative response, not the lack of a negative response.

I loathe robocalls, which quite significantly outnumber the number of legitimate calls I get. Sending them to voicemail, where I have to actively connect and manually delete each one using an annoyingly slow and clunky interface? Oh, please, no.

I've started to get some "calls" that leave voicemail spam without ever ringing the phone, and they are far more irritating than plain old robocalls (which I can just let Google talk to on my Pixel).

Too soon losing Roblimo, but the post seems strangely appropriate.

RIP Roblimo

The subheading in the linked article ("It's the first waiver granted for flight in Class B airspace since the FAA came up with commercial drone rules.") makes sense, but the summary, title, and article are a bit wonky.

It's been perfectly legal for a certified commercial Remote Pilot to fly at an airport since Part 103 went into effect, but only in Class G airspace. Small airports with Class E Surface or Class D airspace would require a waiver, and waivers have been had for those for a while now. Larger airports with Class C airspace took longer before the FAA began processing (and approving) waivers, but there had not been any waivers of Class B airspace. This is the first.

Of course, you can only get a waiver under Part 103, so if you're a hobby pilot, the five-mile rule is in effect. For Part 103 Remote Pilots, on the other hand, it's all about airspace. (Most of the FAA Knowledge Exam is airspace and weather.)

Also, chemical propellant is "heavy", meaning it takes much more mass to get an equivalent kick. If you want real words, the Isp (specific impulse) is lower for chemical propellant engines than for ion engines. With all electric satellites, you can carry much less propellant, meaning you can have a satellite of comparable capability in much less mass. In the case of these two satellites, the Boeing BSS-702SP platform they're built on means you can fit two on a "normal" GTO launch. That basically halves your launch costs.

The tradeoffs are that while all electric propulsion is very "fuel efficient", the thrust of ion engines is a very small fraction of that of the more conventional chemical propellant engines, so instead of taking days to settle in to your final orbit, it can take weeks of slow orbit raising. This is a "cost" that may or may not be worth the trade. Also, since the 702SP satellites are launched in pairs, a launch failure could take out two birds with one... rocket. To give a bit of insurance against this, Eutelsat and ABS chose to split two rockets. They'd each fly one satellite per launch, meaning they only risked one of their two each flight in case of a Very Bad Day.

I never had one, but a friend whose dad worked for IBM did, complete with a whole stack of sidecar expansions. It actually looked rather entertaining as wide as it ended up.

Admittedly, they stacked to the side and were only for expansion, but they did stack (or daisy chain, if you use more mellifluous terminology).

QuickJava lets you add a simple button to enable/disable javascript (and Java, Flash, Silverlight, and more). It doesn't let you whitelist, as it's a set of simple toggles, but it's quite convenient.

https://addons.mozilla.org/en-...

I turned most of its buttons off, but the javascript one comes in quite handy, and I can keep flash completely disabled except in the rare cases I want it for something.

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.

"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.)

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.)

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!

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.)

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.

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.