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201 MPH Pod Run Wins SpaceX's Second Hyperloop Competition (geekwire.com)
An anonymous reader quotes GeekWire:
The speediest team from SpaceX founder Elon Musk's first Hyperloop pod competition has done it again: WARR Hyperloop from Germany's Technical University of Munich won today's second contest by sending its magnetic-levitation pod through a nearly mile-long test tunnel at a peak speed of 201 mph [video]. Musk announced WARR's victory to a crowd in the stands at SpaceX's headquarters in Hawthorne, California, and in a tweet... This weekend's competition brought about two dozen teams to Hawthorne, including a student group from the University of Washington. Each of the teams developed a pod that was designed to test engineering approaches for Musk's Hyperloop rapid-transit concept, which calls for sending people and cargo through low-pressure tubes at near-supersonic speeds.
Musk also tweeted that it "might be possible to go supersonic" in the 0.8-mile test Hyperloop tube, though he conceded it would require an extremely high acceleration (and deceleration) because of the short distance.
"For passenger transport, this can be spread over 20+ miles, so no spilt drinks."
Musk also tweeted that it "might be possible to go supersonic" in the 0.8-mile test Hyperloop tube, though he conceded it would require an extremely high acceleration (and deceleration) because of the short distance.
"For passenger transport, this can be spread over 20+ miles, so no spilt drinks."
Maglev in evacuated tubes can, in theory, be one of the most energy efficient ways of transportation. There is no loss to friction–so not much to fear from Thermodynamic's second law, making the process reversable in theory. And if you can then use the Maglev technology to recover most of the kinetic energy, you're there.
The real technical challenge is not how to build a pod that can accelerate to supersonic speed inside the near-vacuum, the real challenge is how to build a very long vacuum tube that would be safe and cost-efficient to operate. So all those hyperloop competitions do nothing to advance the hyperloop idea -- it is just a show for a gullible public.
Can that maglev do 0-267-0 in 0.8 miles?
No. It was design to carry human passengers without killing them.
Hmm, is there an error in my maths then?
ignoring trivial rounding that is...
267 mph = 430 kph = 120 m/s
0.8 miles = 1.3 km
Assuming a constant acceleration, from rest, to peak speed, followed by constant deceleration, to standstill, pod will use half the track to reach peak speed.
i.e. distance to reach peak speed = 0.65 km = 650 m.
Using: v^2 = u^2 +2as gives:
'v' and 'u' are interchangeable, depending on whether we're accelerating or decelerating. 'a' will have the same magnitude in both cases...
120*120 = 0 + 2*a*650
=> a = 120*120/(2*650)
=> a = 11 m/s^2
Are you really trying to tell us that a human body can't accelerate at 11 m/s^2?
For reference acceleration due to gravity is roughly 9.8 m/s^2
Unless there's an error in my maths of course - it has been 30+ years since I studied these equations in school...
The math is correct, but gravity doesn't go away, so total acceleration with horizontal track is sqrt(11^2+9.8^2) m/s^2=14.7 m/s^2 = 1.5g. Not deadly. Still, killing jokes is no laughing matter.
Slashdot isn't going to change
Given what we have witnessed on this site in the past 10 years, how can you honestly say that with a straight face?
Perhaps he should say "this aspect of Slashdot isn't going to change". It's an American site, and a primarily American readership. Always has been, and there is no indication that's likely to change. And for better or for worse (mostly worse), Americans use the Imperial system, except when we don't even follow that, e.g. US vs Imperial gallon.
[The history of the gallon difference is kind of interesting. The UK had several definitions of "gallon" including the wine gallon (231 in^3, standardized in 1706), the ale gallon (282 in^3, standardized in 1700), the Winchester gallon (272 in^3, standardized in 1697) and the Irish gallon (217 in^3, standardized in 1495). The US standardized on the wine gallon, and that remains the US gallon today. In 1824 the British established a new Imperial gallon which didn't match any of their previous gallons. It was defined as the volume of 10 pounds of water at 62F.
While I'm being pedantic, it's also worth noting that the US gallon wasn't originally well-defined, because the inch wasn't well-defined. The inch was vaguely-defined per the old British definition as the length of three barleycorns, though as of 1814 the canonical inch was a measure stored in the Exchequer chamber in the UK. In 1866, the US inch was defined as 1/39.37th of a meter, which gave it, and therefore the US gallon, a precise measure. In 1959 it was redefined as 1/36th of a yard, which was in turn defined as 0.9144 meters, making the inch exactly 2.54 cm long, and decreasing its length by two millionths, thereby shrinking the gallon by ~6 millionths.
Actually, you can argue that the length of the inch, and hence the gallon, was changed -- or at least clarified -- three more times, when the definition of the meter changed. In 1889 the International Bureau of Weights and Measures replaced the prototype bar in France and created calibrated copies which were distributed around the world. The US received #27, which was calibrated at 0.9999984m ± 0.2 m. That was used to establish the size of the US inch. In 1960 the meter was redefined as 1,650,763.73 wavelengths of the orange line of krypton-86. Then in 1983 the length of the meter was redefined as the distance traveled by light in vacuum in 1/299,792,458 of a second.
This, of course, means that lengths are now defined in terms of time measurements, which raises the question of the definition of a second. The second was defined in 1967 as the duration of 9,192,631,770 cycles of a cesium-133 atomic clock. In 1980 this was further clarified to be a clock at mean sea level, and in 1997 clarified again to specify that the cesium atom should be at rest at 0K (which none are, but corrections to measurements of real atoms can be applied). Future refinements in the definition of a second are all but inevitable, especially since the definition of mean sea level is problematic in various ways.
The US survey inch, by the way, is still defined as 1/39.37th of a meter. So a survey mile is about 1/8th of an inch longer than a regular mile. Over long distances, the difference matters.
And, yes, this post is the result of an hour-long tumble into a wiki-hole which started with a desire to find the history of the difference between US and UK gallons.]
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