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Comment Re:SpaceX Dragon 2 should be ready (Score 1) 87

Oooh, more details on the solid oxygen crystals cause idea? I hadn't seen that one yet.

Also, I hadn't heard that SpaceX and NASA disagreed on the cause of the CRS-7 failure... more like SpaceX figured out early that the symptoms matched a failed helium tank strut but didn't believe it at first because none of the struts they tested failed similarly, so they went on reviewing and ended up testing most of their strut inventory before they found a few (just two?) that were also dangerously weak. At no part of this did I hear anything about SpaceX believing that the probable cause was anything else, just that the initially-predicted cause seemed unlikely.

Comment Actual links (Score 1) 132

http://neumannspace.com/ - the web site of the company / research lab building these things. Kind of hype-y, of course, but has some good info.
http://neumannspace.com/scienc... - the section of the site that gives an overview of how the Neumann thruster actually works, how efficient it can get, and so on. Includes links to blog posts about a number of the fuels they've tested, such as http://neumannspace.com/blog/f... (which has an utterly ludicrous specific impulse).

Comment Big difference in these ion thrusters. (Score 1) 132

Neumann thrusters work very differently from existing ion thrusters, though. At a high enough level, the concept is the same - ionize some stuff, accelerate it using an electric field - but the details matter a ton. Or, indeed, several tons. The existing ion thrusters mostly use gases - xenon is popular - as reaction mass. That means your reaction mass is already conveniently in tiny individual particles (single atoms, since it's a noble gas) suitable for extreme acceleration, but it also means you need to have a bunch of tankage, valves, and so on... and once the xenon runs out, you're done. Xenon thrusters - especially the most efficient ones, which use grids that the particles fly through - have a limited lifetime, too; they wear out pretty fast if you use them with a lot of power.

Neumann thrusters use solid fuels, usually metals (though they also tested with pure carbon, and it worked reasonably well). There's no tankage, no moving parts such as valves (although the fuel rods may occasionally need replacement), and no risk of your fuel leaking off into space. What's more, in theory you can simply use metal that is *already in orbit* (such as discarded rocket upper stages, end-of-life satellites, or even outright junk if you can catch it safely) and that means you can easily "refuel" while in orbit. The performance you get varies depending on the reaction mass, with some metals producing absurdly high specific impulses (11000 seconds?!? That's far better than existing ion thrusters) and some producing more moderate efficiency but permitting quite high thrust (well, relative to other ion thrusters; it's still measured in m/s of delta-V per month) if you have the power (without eroding any part of the thruster except the fuel rod, unlike a conventional ion thruster running at such power levels).

Some of it, like the in-space "fueling", is more than a little difficult, but the basic idea seems sound. It's also a pretty new technology, and they've already come up with some improvements (such as a magnetized "nozzle" that gives better thrust, presumably meaning it improves electrical-power-to-thrust efficiency) so I'm sure the technology will mature still further as research on it continues.

Comment Re:And I was modded down... (Score 1) 182

It was already up to the payload owner, not to SpaceX, whether or not the static fire was performed with the payload mounted. The first few Falcon 9s were all tested without payload. However, customers started opting for the post-integration test; it saved time (no need to take the rocket down again, attach the payload, and roll it back out). For people on tight schedules, it was deemed worth the risk; SpaceX had not, and still has not, ever lost a Falcon 9 stage due to engine failure*. I wouldn't be at all surprised if SpaceX's customers do indeed go back to testing without their payloads attached, but it will be, and always has been, their choice. It's not a matter of costs, either, just of schedule.

* There was a single engine failure on CRS-1, but it was non-catastrophic; the rocket shut down that engine and continued to orbit, demonstrating its engine-out capability. CRS-7 failed in the upper stage during the boost phase; the second-stage engine was not ignited (since it was still attached to the first stage) and the first-stage engines continued firing right up until the rocket came apart. This recent failure came before *any* of the engines were ignited, and started in the second stage (which wasn't even going *to* ignite).

Comment Re:Tanker Last ? (Score 1) 202

It takes multiple tanker runs to fully fuel one of the spaceships. They aren't likely to build enough tankers to have them all waiting in orbit for the moment eh spaceship finally launches. If it was a single run (like the video shows), it'd make sense to send the tanker first (unless boil-off is a particularly bad problem), but it's not a single run. More like 4-5 runs per spaceship.

Comment Re:Wow (Score 1) 202

It explicitly says that the booster lands back *on the launch pad*. And, realistically, there's no reason to expect they couldn't do that. SpaceX has had some difficulties with the landings in general, but landing *on the right spot* has not been hard. They've been goo with that from the first attempts, and are only getting more precise.

Comment Re:Unpopular opinion (Score 1) 132

1) Its UI, especially around tab management, is trash. No way to switch tabs in last-used order, no way to see a preview of all open tabs (or even their titles) at once, no way to tell what tab opened another tab, no way to group tabs, can only re-open closed tabs in the reverse order they were closed.
2) Its cookie management is coarse and barely present. It is very much a mobile browser in that way, and this is not a good thing. Ad-blocking extensions make this somewhat more tolerable, but it's still bad.
3) It doesn't provide a way to view the TLS server certificate. It'll give you some basic data about it, but that's it.
4) No RSS reader. That's a deal-breaker for me; I use RSS daily and have no reason to switch to another app when my browser takes care of it for me.
5) Can't re-open a previous browsing session unless set to always do that.

They are steadily improving it, so I suppose there's some hope, but right now it's still a shit browser, especially for a PC. Less shit than it was a few months ago, but still definitely shit.

Comment Re: Great (Score 1) 177

Vista had some very silly bugs, and a lot of software would not run on it *effortlessly*, but it would run. Setting the application Compatibility Layer option would fix most things, and either running as Admin or making whatever folder the moronic thing was trying to write to writable would fix the rest.

They did change the driver model, but even then, I only ran into one piece of hardware (between early 2006 betas and when the Win7 public beta arrived) that I couldn't convince to work, and it only barely worked on XP.

Having run XP as a non0admin, trust me when I say that UAC was a life-saver. For people who actually give a damn about security and like having control over what their computer did, Vista was a pretty great OS. That, plus the Start menu instant search, made it utterly painful to go back to XP.

With that said... I only ever ran clean installs of Vista, with no OEM crap on them. I saw some of the shit that OEMs would dump on their Vista machines, and I can see where it got its bad reputation. It's not the OS's fault, though; Microsoft can't control what crap OEMs load their machines down with, including stuff that digs deep into the OS and then falls over, taking everything with it. I personally never got a bluescreen post Beta2 (through the RC1 and RC2 builds, and release) except for a few due to NVidia's really shit-tastic drivers (if your video driver crashes *twice* within the space of a few seconds, Windows gives up on recovering it and just bluescreens instead, figuring something is Really Deeply Wrong. They were right, but the stable NVidia driver for my GPU had 40% as much performance and 40% as many features, too).

Comment W10M is rooted (Score 1) 177

There's actually a full jailbreak available for all W10M devices right now. Arbitrary code execution as SYSTEM. In theory it can be made to work for kernel too, though I don't think anybody has tried it yet. It's only a couple weeks old. Not a lot of software ported yet but we've got SSH and PowerShell, among other things.

Comment Project Astoria (Score 1) 177

They actually did this... briefly. The same Linux subsystem that enables the whole "Bash on Ubuntu on Windows" think in the 1607 release of Win10 was also being used to run Android apps, natively, on early Win10 Mobile builds. It was called "Project Astoria" if you want to read more about it.

Sadly, MS then quietly (but *very* thoroughly) killed off the project. No build released any time recently includes Project Astoria anymore, or will let you install it, or will run it if you hack it into the OS. They shut it down *hard*. They still offer tools for porting Android and iOS apps, but the native runtime is - for now - dead. I bet they could revive it in a hurry if they wanted to, but that doesn't seem to be happening.

The two best explanations that I've heard for why Astoria was killed are that Android's app security model was too different from W10M's (they both use sandbox containers wherein processes are granted access based on the "capabilities" declared in the app's manifest, but the similarities largely stop there), or that they figured it wasn't worth the dev time and install footprint for something that would actually give developers *less* reason to target W10M (just target Android and get two platforms at once). Given Microsoft's godawful history of prioritizing developer time in user-unfriendly ways, the second wouldn't surprise me, but being familiar with the security models of both Android and W10M I have to say the first is pretty plausible. They could have made it work for *most* apps, but it would have been a kludge.

Comment Re:Countdown to endless arguments in 3.. 2.. 1.. (Score 1) 248

The acceleration is constant, hence the energy gain is constant.

Wrong. The formula for kinetic energy is

The following numbers are unrealistic and made up for simplicity.
You have a 1kg object. It includes an EmDrive and some "solar cells or whatever". The solar cells produce 1kW of power. The EmDrive can convert this into 1N of thrust (which will produce an acceleration of 1m/s^2). The object is initially at rest. At t0, the EmDrive is turned on.

  * At t0, the object is experiencing 1m/s^2 instantaneous acceleration, but has not yet started to move. It has 0 kinetic energy.
  * At t1 (1 second later), the object is still experiencing 1m/s^2 of acceleration, and is moving at 1m/s. By E = m*v*v/2, it has gained 0.5J of kinetic energy in one second. In the first second of applying 1kW of electrical power (meaning a total electrical energy input of 1000J), the object gained 0.5J of kinetic energy.
  * At t2, the object is now moving at 2m/s, and has 2J of kinetic energy. This is a change of 1.5J of energy over 1 second, for 1.5W of kinetic power. It still takes 1000W of electrical power to produce this change, though.
  * At t3, the object has a kinetic energy of 4.5J, 2.5J more than it had a second ago. As you can see, the object's kinetic energy increases non-linerarly (specifically, it increases quadratically), even though the input energy is not increasing.
  * Let's jump ahead a bit. At t500, the object has v=500m/s, for kinetic energy of 125000J. We're still faaaaar below the point at which relativistic changes to mass are relevant, so we can safely say that our 1N of thrust is still producing 1m/s^2 of acceleration.
  * At t501, the object now has 125500.5 J of kinetic energy. That's a change of 500.5 J/s, or 500.5 W. Remember that we're still only putting 1000 J/s into driving the EmDrive, but the EmDrive's thrust is now increasing the object's kinetic energy by half that much... and rising.
  * At t1000, the object now has 500000 J of kinetic energy.
  * At t1001, the object now has 501000.5 J of kinetic energy. The input of 1000 J of electrical energy (over the last second) has produced an increase of 1000.5 J of kinetic energy. The EmDrive is now producing more energy than it is consuming!

As time goes on, that value will only increase. Eventually, it'll reach the point where you could strap the object to a wheel or crank, and input energy until the object is rotating fast enough that you can draw over 1KW of electrical energy out of the machine, with less than 1N of load on the crank, by connecting the crank to a generator. The wheel will keep accelerating, and the EmDrive is now powered by the generator. This is a truly perpetual motion machine, now; it can (ignoring mechanical failures) keep going long after the sun goes out and there is no longer any power source *except* the generator that it is turning.

Comment Re:Countdown to endless arguments in 3.. 2.. 1.. (Score 1) 248

With all due respect, you don't have any idea what you're talking about, and should do some research to avoid embarrassing yourself further.

Your arguments with regard to "the law of conservation of momentum" are basically correct, though poorly stated. Maybe it violates conservation of momentum, in which case conservation of momentum is not a real "law" and becomes merely a widely-used approximation. Maybe it's imparting momentum to something but that isn't a thing we thought could have momentum (see: quantum virtual plasma), in which case the "law" is intact but some other aspect of our understanding of physics gets a major overhaul. Maybe it's actually imparting momentum to a real thing, and there's just been some consistent experimental error that failed to prevent or detect this. Maybe it's not actually imparting momentum to anything at all, and doesn't actually produce thrust, and the observed thrusts are all experimental errors.

Your argument regarding xenon drives (more commonly just called ion drives, ion engines, or electric thrusters) is wrong on all counts. There is absolutely no requirement that your exhaust be moving faster than your vehicle (in what reference frame, anyhow?) for a vehicle to accelerate. Indeed, if there were, rockets could never reach orbit; even Low Earth Orbit requires going faster (relative to Earth) than a chemical rocket's exhaust (relative to the rocket). Relative to an observer on Earth, the exhaust of an orbital rocket during its orbital insertion is actually *in the same direction* as the rocket, not away from it. You should read http://www.real-world-physics-....

Even if that weren't true, though, you're *STILL* wrong. The thing that limits ion drives (including xenon drives) is that they have limited fuel. The ionized gases (xenon or anything else) they use as propellant may have extremely low mass compared to the few tons of chemical rocket fuel that a liquid-fueled spacecraft (including satellites) might carry, but there is still a "fuel tank" and it can still run out. When it does, your ion drive stops working, no matter how much electricity you pump to the electric fields. Thus, the maximum amount of impulse (which, divided by mass-over-time, gives the maximum acceleration; integrate that by time gives the maximum velocity) that an ion drive can produce is determined by its fuel capacity... just like a chemical rocket.

"Photon drive" is one of many terms for a "rocket" that gets its impulse from the momentum of photons. Yes, photons have momentum (even though they don't have mass); this is how a solar sail would work. Even just turning on a flashlight technically produces a (undetectably small) thrust in the direction opposite the beam. See https://en.wikipedia.org/wiki/... for more discussion of how one might build a photon drive. The problem with photon drives is that they have crappy energy-to-thrust efficiency. One of the ways people know the EmDrive is not just a photon drive is because, even at its barely-detectable thrust levels, it's still producing vastly more thrust than a photon drive consuming the same amount of power could manage. Still, the concept of photonic propulsion has some potentially useful applications, and has been known for many decades.

The rest of your post I *mostly* agree with, although the apparent violation of conservation of energy (in addition to apparent violation of conservation of momentum) is another reason to be skeptical of the EmDrive. Maybe it's just transferring energy from some other source we don't yet recognize, like the way uranium "spontaneously" produces energy (heat) from nuclear decay, and a few hundred years ago we couldn't even have understood nuclear decay (in the context of our then-current physics knowledge), much less predicted that we would find it in reality, that it would decrease over time, etc. Maybe the energy required to keep the thrust constant somehow increases as the drive itself is going faster, from a given reference frame; this would allow it to keep up with kinetic energy increasing as the square of velocity, but would turn other aspects of physics on its ears. Maybe it's something else. Maybe there really is perpetual motion, free energy, and all our physics knowledge needs a major overhaul. Maybe our whole existence is a simulation and we found a bug in the modeling of contained electromagnetic radiation, who knows?

I approve of the refusal to state that something is "impossible", but bear in mind that scientific research is still *expensive*, and the expected payout from something that seems as unlikely as the EmDrive is quite low, because the expectation of success is quite low and we don't learn much from it failing (as that would be consistent with our current models). Thus all the (relatively) low-budget experiments so far; as long as they produce findings that violate expectations, the expectation of success gets a little greater, and the expected payout increases commensurately, until it's expected to be worthwhile to fund a higher-budget experiment.

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