One thing that always bothered me about airplanes is the energy used to take off. On aircraft carriers, they use a launch device, allowing the airplane to "push off" against the carrier. Compare this to airplanes taking off on land, they just nail the throttle and take off by pushing air...
A land-based launch system would have a lot of advantages; lower peak power would be needed from the motor and batteries, the engines could be made smaller, the energy used to take off doesn't have to be stored on the plane, everything gets lighter and more efficient.
I'm not sure that it would let you lower the peak power. Most takeoffs aren't limited by runway length. You use full power just because it's safer to get off the ground earlier. Max power requirements come from the maximum altitude the plane is expected to reach, or for multi-engine aircraft the need to be able to climb out after an engine failure.
Aircraft carriers (some of them) use catapults because that's a case where runway length is, by far, the limiting factor.
Note that this quote was in reference to the autonomous drone they produce, not the manned trainer that was the subject of the article. I would presume there are more challenges in building a launch assist catapult for a crewed flight.
From the data on the Wikipedia page for the Boeing 747, it looks like the empty weight is around half the maximum take-off weight. Passenger and cargo aircraft seem to usually turn around quite quickly and spend only a small amount of time on the ground. In which case around half of the energy required on take off is just to lift the airframe back to the same altitude it landed from.
Perhaps if aircraft could use some sort of funicular system so that one aircraft taking off could get a "boost" from one slowing down to land?
Or planes could land on giant inflatable runways at 30,000ft, with the passengers and cargo taking a lift down to ground level?
I would think that most of that energy is used to transport the 747 1/3 of the way around the earth, overcoming induced and parasitic drag for 8+ hours.
From a straight lifting standpoint, lifting 910K pounds to 37K feet takes about 45 billion joules, which is the energy content in about 320 gallons (~2200 pounds) of jet fuel (if consumed perfectly efficiently).
A 747 burns about 1 gallon of fuel per second, meaning the straight lifting fuel consumed represents about 5 minutes or 1% of the fuel consumption on the flight.
While it is true that you "nail the throttle" during takeoff in a little general aviation Cessna, the same is not true of jet-powered heavy metal. The big planes that account for most passenger miles are limited by engine noise regulations and scaring passengers, and run the engines at a fraction of peak power during takeoff.
You can find implausible-looking-but-true videos of big ungainly airplanes taking off near the edge of the flight envelope in ways that look very surprising.
Sure, they don't save energy in the sense that the laws of physics must still be obeyed- but by using the power of the catapult to increase the plane's velocity at takeoff, the motor can be optimized for flight rather than takeoff and less battery weight needs to be carried.
That's because catapults are used in places where space is at a premium. Catapult + full throttle will minimize takeoff length. But if space wasn't at a premium, then surely throttles could be reduced, no?
This has been proposed many times but doesn't seem to be practical or cost effective. The airport infrastructure investment would be huge. And aircraft would have to be redesigned so that the nose wheel (catapult attachment point) could handle a much higher sheer force. Making those parts stronger adds weight, which wastes energy during the rest of the flight.
1. Aircraft use 100% power in situations other than takeoff, so it's hard to see how you could lower peak power/use smaller engines just by eliminating takeoff.
2. Typical aircraft takeoff roll is under 30 seconds, and most aircraft have 3hours+ endurance, so you'd be extending the range of the aircraft by < 1/360th.
My 1700x build for video processing has suffered major instabilities -- app crashes and BSODs -- memory corruption type errors. I went through 4 different types of DDR4 memory until I found some that works, even though it isn't on the ASUS's Qualified Vendors List. My advice is to make sure your RAM can do 15-15-15-36 timings (or better).
This is why I'd rather lose 25% of the performance these days and take a canned pre-built PC. I just can't afford the time to find this out. It was bad enough trying to find a working set of drivers for my T440 and that only took an hour or so.
I lived through the age of self build K6's, Athlons, dual Celerons and SLI Voodoo 2's and heatsinks the size of a can of coke. I'd rather just have a shitty old thinkpad and a box in AWS now. This all happened when I realised a naff old Pentium III 1.4 GHz (Compaq AP230) was actually my goto machine despite having things 3-5x the speed.
I run a fair few high CPU/RAM simulations with LTspice as well for ref.
I ran all the usual suspects (memtest86 etc) for 24 hours after I built it, not had a single issue in 2 weeks under Linux (Fedora 25) though I've seen people having a lot of issues with various RAM configurations.
I went for 32GB of Corsair Vengeance over 2x16GB at a conservative timing (the newer beta bios for the mobo I have supports more memory options as was as clocking) since it's a machine at work.
I've also heard the same. I've made comments on this post about the issues and poor performance with transcoding (specifically ffmpeg benchmarks), which is unfortunately why I've had to stay away.
The filter checkboxes are a bit weird, for example elements (such as br and img) which are both self-closing and inline only show up if both self-closing and inline are selected, instead of one or the other. Also there are several elements such as li which are not categorized and show up even if no checkboxes are selected.
To a large extent, my daily driving consists of going to the same 5-10 places. I'd like my car to watch me drive somewhere and then just do that, with minimal improvization. For example, in order to enter my driveway I have to swing wide into the oncoming lane to make the turn. When I drive to work I avoid the same potholes all the time. Pretty trivial to just record my driving once or twice, and replay that back with minimal improvisation.
Oh yes, and nobody cared about the performance aftermarket (basically anything you do is going to violate emissions standards) until Harley started selling bikes already modified for "racing".
I dropped 20 lbs off a 330lb bike (and added about 5hp) by replacing the heavy dual exhaust with a single Ti/carbon pipe, and reprogramming the ECU. I'm sure the manufacturer would have loved to give me a 310lb bike that made more power if they could. (and before you ask, no it's not loud, I hate loud pipes)
Incidentally, the exhaust/ECU upgrade was done by the local shop when the bike was purchased new. Basically the same as what H-D was doing.
Anyway, what H-D got popped for is arguably less egregious than what VW was doing. They admit that the modified bikes bypass emissions requirements, whereas the unmodified VWs didn't meet the requirements and had to cheat to pass inspection.
One megahertz is more than enough. That's enough power to compare like three-thousand integer values per second, which is way more than a human can do. We've got these guys out there, and they've got 3 gigahertz and more! And they're not even using them! They're playing Candy Crush for gosh sakes!
These people are wasting energy and these super-powered CPUs are a potential fire hazard and we need better regulation enforcement now!
If we restricted high-powered CPUs to people with a license and a documented need, the world would be a safer place for me.
...In all seriousness, 1hp is not serious shit. And motorcycles are significantly faster and more dangerous.
You me and the author are on the same page. Top speed isn't the issue that the author is complaining about, and it's not the reason to get more power. It's about acceleration and hill climbing. That's why he wants more power, and it's why he hates hub motors big and small. In the author's case, it's so that he can power a heavy bike with 5.5" wide tires through deep snow. So many people in this thread don't ride like this, so they imagine 2500 watts powering their skimpy road bike with 110psi tires. He talks about it in this post: https://electricbike-blog.com/2016/12/21/electric-fat-biking...
Exactly. I'd happily buy another $3000+ ebike with a top speed of 20 mph if it could get to that speed faster, and maintain it up hills. The hills, especially, slow me down a lot, and more than I'm happy with.
A land-based launch system would have a lot of advantages; lower peak power would be needed from the motor and batteries, the engines could be made smaller, the energy used to take off doesn't have to be stored on the plane, everything gets lighter and more efficient.