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Tethered, Water-Powered Jetpack Provides Two Hours of Flight Time
arshadk writes "Unlike 'ordinary' jetpacks, the JetLev is actually two vehicles, tethered by a hose the thickness of your thigh. On the water is a small speedboat-like unit which contains a 250 horsepower motor and a pump. This is connected to the pack — into which you strap your frail body — by a 10-meter hose. The water is pumped from the sea or lake below up to the nozzles on the jetpack, providing a 1,900-Newton thrust, enough to lift a human weighing up to 150 kilos."
This is like hanging onto a firehose.
Maybe it's the American in me, but I was hoping to see the jet pack fail in mid flight as the guy takes a Red Bull flight contest dive.
Seems to me they discovered the FLUDD, nice.
You're then pulling along a 20km hose behind your rocket, and that hose has to be strong enough to support its own weight. You're going to add more weight than you're subtracting.
Unless you built a 20km tall tower that the hose hangs down from and as the rocket ascends you retract the hose so the rocket doesn't have to carry the slack. But then you have to build a 20km tall tower that can hold an enormous amount of hose (still sturdy enough to be 20km long) and the weight of the fuel item you're moving, and since that weight is going to be on one side of the tower you'd have to counterbalance it on the other side. Tricky.
10-20km of hose would be kind of heavy. Especially the top of the hose which has to hold up the rest...
WARNING: Jet Pack does not function as a flotation device.
HEX
Horror & SciFi Erotic Nudes
Why is 2 hours of flight time an apparent selling point for this thing? Why would anyone need or want to hover a few feet above the surface of a lake for 2 hours nonstop? Granted, you can "fly" much longer than in more traditional jetpacks, but it seems a bit like bragging about a car that can go 600 miles on a single tank but is permanently tethered to the gas station.
That said, it sure looks fun to try.
Oh come on. Maybe it doesn't make anything, but it does seem like a relatively cheap and safe way to live out childhood fantasies.
If you build it high enough, then you can just toss the satellite of the roof to get it into orbit.
Orbit is about velocity, not altitude. You would have to "toss" it at orbital velocity, otherwise it would just drop...
A house divided against itself cannot stand.
I think i've seen this before, I wonder where that was. Oh wait, it was two years ago, on /. http://tech.slashdot.org/story/09/02/17/0058202/Jet-Pack-Runs-For-Hours-On-Water
Reminds me of an old joke about a wrist watch with a built in TV and built in radio and photo-camera and various other tools.
The only catch was that if you bought that watch you always had to carry 2 suitcases with you.
They were filled with batteries.
You can't handle the truth.
I'm watching that clip and wondering if you strap on SCUBA gear, make the engine neutrally buoyant, include oxygen tanks for its engine, and just go nuts under water.
Now you have a jet-powered underwater propulsion system. That's got to be rather cool and maybe even useful?
I prefer my Christmas decorations nailed to a cross.
Divide a cake by zero. Is it still a cake?
Not just tensile strength. 10km of head of pressure is not insignificant, and would require one hell of a pump to push it up there, and a lot of strength to hold it in.
Jet Pack Runs For Hours On Water
Posted by kdawson on Tuesday February 17 2009, @06:11AM
from the got-your-back dept.
Ponca City, We love you writes
Jet packs have been around for half a century, but there's always been one problem: they run out of fuel in around 30 seconds. Now a German company has taken the standard jet pack design, run a fat yellow hose out the back, and connected it to a small unmanned boat that houses an engine, pump, and fuel tank and sends pressurized water up the hose, where it's shot out by two nozzles just behind the wearer's shoulders. Called the JetLev-Flyer, the design purportedly can reach a height of 15 meters, a speed of 72 kph, and a range of 300 kilometers based on four hours of flying time. A digital fly-by-wire system is used to control the throttle. Future designs may achieve higher altitudes, higher top speeds, and extended range, and even travel below the water's surface. The American manufacturers claim it is 'amazingly easy to learn and operate' and they're taking orders now at $130,000 each.
It's 2009 again!
This post contains no rudeness or derision of any kind. All arguments are friendly. Terms and exclusions may apply.
Space flight was achieved by addressing technical objections, not by ignoring them and pretending "creativity" is all there is to it.
So for instance, if your creative idea requires a 20km high tower made of solid unobtainium, then you have a problem, until you actually succeed at coming up with a material with the required properties.
You're proposing the idea, it's your job to prove it can be done. So go provide some calculations.
Of course first US Navy and Marines will fund the R&D to develop it as AMBaIV (Advanced Marine Boarding and Inspection Vehicle) to serve in the blockade missions. The R&D Center will be in the home district of some powerful senator. So it will get funded. Then the specs will creep up, ability to hover with a machine gun ... 200 rounds of ammunition... SatNav system... eventually a 105 mm naval gun will be added (and 200 rounds of ammunition). Eventually the cost of the system will be so much that actual deployment will never get funded. But using all the R&D knowledge accumulated in the Defense Contractor, they will create a civilian version. Which will start out as a recreational vehicle. Once the production tooling and factories have been paid off the prices will drop. So the early units coming out of service will have very low resale value. These will be bought by the Somali pirates.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Put a 10 meter scissor-lift on a boat?
I can't imagine shooting a massive fire hose directly into the water is exactly "stealthy", I'm not sure how stable the guy floating on that water jet is, making recon photos (at the least) blurry, and if you have to keep a boat and a tether with you, what are you saving versus a boat with a scissor-lift.
Or, perhaps you could use one of those "mobile surveillance towers" I've seen in some parking lots/sporting events
Ken
Its the other way around. Think like a canister vacuum cleaner, you tow the vessel. The article says 35MPH for 2 hours if you wanted.
All of the above was encrypted with a Quad ROT-13 method. Unauthorized decryption is in violation of the DMCA.
or Wile E. Coyote tries to "fly" over a tree branch and then gets wrapped around it in every decreasing circles before sudden and final deceleration occurs.
And don't forget flying over the water falls, realizing the error, looks down and sees the boat falling fast, hose stretching and stretching, and then yeowwwwwwww!
LoB
"Anyone who stands out in the middle of a road looks like roadkill to me." --Linus
This so reminds me of Wile E Coyote. Finally, the Acme Jet Pack!
I'd particularly like to watch this when the flier is up at maximum height and going 35mph, and suddenly the boat hits something and stops.
Don't forget that thrilling ride under a bridge.
Most useless invention ever...
It's called entertainment. Some may call it useless. Frankly, I would say it's the only inherently useful thing humans create -- all other "useful" inventions are useful only to the extent that they further our ability to enjoy. The only useless invention is one that never leads to any increase in human joy. Anything that is properly classified as entertainment does, by definition.
"Convictions are more dangerous enemies of truth than lies."
If Americans read that as pounds they'd tell you that's actually quite a small person.
On second thoughts, even if they understood it correctly they'd say the same thing.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
This device will likely be immensely popular. Even though there are dozens of posts here that dismiss it because one flaw or another, they overlook one of the most obvious and lucrative fields. Tourism. Just like getting parasailing (boat pulling a parachute) is not a practical form of travel, it is quite fun. Also, I suspect the 8.5 meter water jet flight is probably safer than the 15-20m parasail experience. Expect to see jetpack trips on every popular tourist beach in a few years.
From TFA: "The rub is that this costs $100,000 to buy. At this price, it is aimed more at water-sports–rental businesses than at the private user"
“Common sense is not so common.” — Voltaire
First some definitions. For the purposes of this post
Tope is defined as a construction that is built to withstand tension but will simply bend out of the way if subject to compression. Further it has mass. The mass and strength of a rope may or may not be uniform (for a space elavator it most likely wouldn't be)
A space elavator is a rope running from the earths surface and held up by cetrifugal force.
The nice thing is there is no "you need to support the weight of the rope" non-sense because with centripetal forces, it all equates out and the rope doesn't have to support its own weight.
It does kind of.
A mass that is stationary above the equator of a heavy rotating body such as the earth has an effective weight which is the objects weight minus the centrifugal force* acting on it. Weight is proportional to the objects mass multiplied by the inverse square of altitude. Centrifugal force is proportional to the objects mass multiplied by altitude. At some altitude those forces balance out and the effective weight becomes zero, we say an object that is above the equator at this altitude is in geostationary orbit. Above geostationary orbit the effective weight would be negative
This background leads us to the following statements about a space elavator.
1: To keep forces balanced the tension in the rope at any point must be the tension at the ground plus the effective weight below that point minus the effective weight above that point.
2: The rope at the ground must have a tension that is greater than or equal to zero (per defintion that a rope can't resist compressive forces) therefore the overall effective weight of the rope must be negative. This means that the rope (or a weight attatched to it) must extend beyond geostationary orbit.
3: The point of maximum tension in the rope is at geostationary orbit since all mass above geostationary orbit has a negative effective weight and all mass below has a positive effective weight. The rope at geostationary orbit must be able to support the effective weight of the entire run from geostationary orbit to the ground plus the tension at the ground anchor (you don't want this to be zero since it must remain positive even as dynamic changes to the system (such as a climber being attatched to the system) happen.
* http://en.wikipedia.org/wiki/Centrifugal_force#Fictitious_centrifugal_force
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