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Comment: Re:It doesn't work that way. (Score 1) 113

by bbn (#49497535) Attached to: An Engineering Analysis of the Falcon 9 First Stage Landing Failure

The engine can throttle between 50% and 100%. It is true that even 50% of just one of the nine engines is enough to shoot the rocket back towards space. Which is why it can not hover.

But hover is not relevant. Hitting zero velocity at height zero is.

Let the rocket drop freely while continuously calculating needed thrust to hit the target velocity zero at zero height. Keep dropping until your algorithm says you need 75% thrust. At this moment you relight your engine at 75%.

Now you can do a control loop with feedback to vary the throttle between 50% and 100% with the perfect descent hitting 75%. This should be plenty to do the job.

In addition you have at least two other mechanism to help a successful landing. One is the braking by aerodynamic mechanisms that can be varied. Those might be more precise than engine throttling. Another is the landing legs. They will be designed to absorb hitting the ground at a small non zero velocity.

Comment: Re:It's not polite to talk with your mouth full (Score 3, Insightful) 298

by bbn (#49358295) Attached to: Ask Slashdot: What Makes Some Code Particularly Good?

FACT: The PC to Server ratio is MILLIONS to 1 alone

This does not stand to even 5 ms of thinking. I am living in a country with 5 million people. You are claiming we have 5 servers or something like that.

Or if you are an american: How many cities do you have with more than 5 million people? How many cities with more than 5 servers? ...

Or ... there are about 7 billion people on the earth. Lets assume that each have a PC (many don't). You are claiming there are only 7000 servers on earth.

Comment: Re:Good Luck (Score 5, Interesting) 331

by bbn (#49358225) Attached to: Amazon Requires Non-Compete Agreements.. For Warehouse Workers

Here we have a very effective law that put a complete stop to the non-compete bullshit: any company that wants a non-compete contract will have to pay half salary for the entire period where said non-compete contract is valid.

So if you stop working somewhere, they have to keep paying you half salary, if they really think that non-compete contract is necessary. They almost never do.

Comment: Re: Strange (Score 1) 80

by bbn (#49177425) Attached to: Linux and Multiple Internet Uplinks: a New Tool

Linux has been able do multipath routing for a long time: it means being able to have routes with multiple gateways and to use them in a (weighted) round-robin fashion. But Linux is missing a tool to actively monitor the state of internet uplinks and change the routing accordingly

No the author is lacking knowledge of such tools. There are at least three major implementations of common routing protocols for Linux.

It is actually surprisingly simple. You activate OSPF on your Linux box and it will add routes on working links and remove them again if the path is no longer viable. Works both ways too, so your routers will not try to deliver traffic to your box on a dead link. Instead the routers will route around the problem.

Comment: Re:(some) cars are gadgets now (Score 1) 158

The car clearly lacks enough sensors to become truly self driving. How is it going to avoid changing lane in front of a faster moving car, when it has no rear facing sensor with longer range than 12 ft? How is it going to tell the difference between a pole and a child on a bicycle before doing a right turn, when it only has simple sonar sensors in that direction?

They could at the very least have added more cameras. Cameras are cheap. Why not let the computer have 360 degree view of what is happening around the car?

But it might also be that there is no way around using LIDAR. It is expensive like hell, but that might change when you need millions of devices a year.

In any case, the new Tesla does not have the hardware necessary to implement the vision of a self driving car. They know it, so that is why they call it "auto pilot" instead. It is just sad that it is nothing new. Every other car in that segment already has this "auto pilot" under different names.

Comment: Re: Failsafe? (Score 3, Interesting) 468

The worse thing that could happen to a view screen is that it gets so smashed up you can't resolve fine details through all the cracks (actually, the absolutely worse thing that could happen is that it ceases to exist, but at that point you've got other problems). But the fine details are hardly necessary for flying and landing.

Not so, This 747 went through a ash cloud from a vulcano and got their windscreen sandblasted: http://en.wikipedia.org/wiki/B...

As Flight 9 approached Jakarta, the crew found it difficult to see anything through the windscreen, and made the approach almost entirely on instruments, despite reports of good visibility. The crew decided to fly the Instrument Landing System (ILS); however, the vertical guidance system was inoperative, so they were forced to fly with only the lateral guidance as the first officer monitored the airport's Distance Measuring Equipment (DME). He then called out how high they should be at each DME step along the final approach to the runway, creating a virtual glide slope for them to follow. It was, in Moody's words, "a bit like negotiating one's way up a badger's arse."[1] Although the runway lights could be made out through a small strip of the windscreen, the landing lights on the aircraft seemed to be inoperable. After landing, the flight crew found it impossible to taxi, due to glare from apron floodlights which made the already sandblasted windscreen opaque.

As you see, they didn't eject. They landed the plane flying blind.

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