Please create an account to participate in the Slashdot moderation system


Forgot your password?
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Comment Not technically reasonable (Score 1) 122

The 3d image shows a vehicle with small ducted fans for lift, and minimal aerodynamic lifting surfaces.

Helicopters use very large blades because (for very basic physics: momentum goes as MV, power goes as MV^2) it is more efficient to move a lot of air slowly than a little air quickly. So it will need more power than a helicopter which will make it less efficient, noisier, and the down-wash will be more damaging.

There may be a few applications where the lack of exposed blades will help, but not many. Even if the blades are enclosed, the very high power downwash will prevent landings near anything even slightly fragile.

Helicopters look the way that they do because that is the best design.

Small quad-copters make sense in applications where efficiency and noise are not critical.

Self flying is great, but that technology is mostly available now anyway

Comment Re:Well, duh. Mass transportation is a slush fund. (Score 1) 392

Probably not really incompetent.

I've been involved in a number of government funded projects where the process was:

Government: we need a *thing*, as cheap as you can.
Vendor1: OK, we can build your *think* for X dollars.
Government: X is too much, we can only fund it if its X/2.

Now there are two choices.
IF Vendor 1 responds with "OK X/2 it is", Vendor 1 gets X/2 dollars, then later get an additional X/2 to finish the project
IF Vendor 1 responds with "Sorry, X is the cheapest we can do", then Vendor 2 will respond with "We can do it for X/2". Vendor 2 gets X/2 dollars, then later get an additional X/2 to finish the project

Many of these projects take so long that the people who budgeted and approved them, both in the government and at the vendor have moved to other jobs before the inevitable overruns become apparent.

Comment Not enough content on streaming (Score 3, Interesting) 84

Netflix seems surprised people are not dropping the DVD service, but a lot of content is NOT AVAILABLE on streaming. I total number of titles it may seem OK, but recent blockbusters generally appear on streaming long after they are on netflix DVD.

I'd love to drop DVDs, but netflix doesn't provide the right content on streaming.

Comment Re:Not any more (Score 1) 56

Usually the FAA is very conservative on aircraft design. I'm surprised and dismayed that they would not disallow any connection between entertainment systems and avionics systems. I'm sure that they have carefully designed the firmware in any switches to prevent data from the entertainment system getting into the flight controls, but it seems difficult to prove that the firmware is free of any bugs that could allow such a connection.

The NSA was unable to prevent a very destructive hack, I have little faith that organizations are able to do so.

Comment Re:How do you get slow neutrons? (Score 1) 188

Proton rest mass: 938.28 MeV
Electron rest mass .511 MeV
Neutron rest mass 939.57 MeV

So, when the electron and proton combine, where does the extra energy 780KeV come from to make a neutron. This is ignoring how slow the reaction would be even if it were energetically allowed.

People talk about "heavy" electrons in metals but interactions with atomic fields are likely to be at most in the 100eV range, not 100s of KeV.

Its nonsense.

Comment Not the worst thing to plug into a USB port (Score 1) 243

If you have physical access to a machine, you can do pretty much whatever you want to it.

If someone is planning to leave theses around to destroy computers then they could do a lot more damage with an infected USB drive - to anyone idiotic enough to plug in an unknown usb device.

If you want to maximize damage, an ounce of C4 in a drive will to a lot more damage. Thermite would be more spectacular.

I don't get it. You spend $150 for a device that will make a computer fail in a boring way.

Comment Re:How or Why: I Don't Care! (Score 1) 477

Cheaper and easier to test on earth. If you replace the copper with a superconducting cavity, the circulation power will go up by about a factor of a million. No problem at all seeing the thrust then.

I could do it for a couple million $ - we have the RF and superconducting cavity equipment. We are well set up to do the experiment.

The problem is that science money is limited. If someone wants to fund me, I'd be very happy, but there are a lot of other groups competing for those same funding dollars.

If someone can get the funding, or convince the funding agencies to switch their money to this, I'll do it. I wouldn't recommend it though - I think the odds of finding something are exceptionally small, and the money is better spent on other projects.

Comment Re:If confirmed, does this make it realistic? (Score 1) 477

It is possible to do a better experiment. With a superconducting cavity, you can get probably 10^6X the circulating power, and (based on their surprising linear slow slope of thurst vs power) a very large thrust.

This is a moderately expensive experiment (few million $), but would be very definitive. Lots of labs, including mine could do this.

Comment Re:If confirmed, does this make it realistic? (Score 1) 477

If relativity is correct, then producing more thrust per power than a photon drive without any exhaust can be used (in principal) to to build a perpetual motion machine. Basically this device claims to violate conservation of 4-momentum, so in the correct frame that is violation of conservation of energy.

If it is possible to create thrust against some sort of background (zero point energy, aether etc), that also violates special relativity by providing a unique reference frame (or violates conservation of energy if it doesn't).

Of course special relativity could be wrong - but it has been tested on scales from quarks to galaxies to black holes. This experiment is not unusual - they are at modest electric fields, length scales and frequencies. There is no reason to expect that after all the tests done on relativity it would be violated by using a special shaped box. Its like the idea that you can build a perpetual motion machine from a special shaped linkage and gears.

I may not be a "top" scientist, whatever that is, but I'm a professional physicist, and have discussed this with colleagues and we all agree that this can't be true without a complete re-write of physics as we know it, We also agree that its a very difficult experiment and that there are a lot of ways that they could have gotten the wrong answer from the experiment.

Comment We can test it if you like (Score 1) 711

We have 100MW RF sources at SLAC. Should give about a million times the force they see, or several newtons - easy to see. No mucking about with careful torsion balances - this is enough to see with a bathroom scale. I'm happy to do the test if someone wants to fund it.

It is exceptionally unlikely to work. The frequencies / field levels are not at all unusual. The existing experiments very difficult to get correct. Its difficult to believe that a violation of conservation of momentum wouldn't have been seen in the wide rage of experiments done in E&M.

Slashdot Top Deals

"Well I don't see why I have to make one man miserable when I can make so many men happy." -- Ellyn Mustard, about marriage