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Jet Packs, Finally On Sale
Bad_CRC1945 writes "The good news: Not one, but two companies are selling jet packs. The bad news: The tech has a long way to go. In the past, potential buyers have been stymied by two problems: Rocket belts aren't for sale, and even prototypes run on modern-day fuel (as opposed to whatever the Jetsons use) which means rocket belts can weigh upwards of 100 pounds, with only enough fuel to stay aloft for under a minute." That second problem's still with us, but the article hints that jet-fuel options (for the brave) could considerably extend users' time aloft.
What exactly is the point of jetpacks supposed to be? They don't seem to be useful for any civilian or military purposes that other technologies aren't more appropriate. Is the obsession with jetpacks just about being like a comic book superhero?
... and then they built the supercollider.
Why do people think that jet fuel is some futuristic stuff? It is basically kerosene.
A not so big secret is that jet engines became popular, not because they were super-efficient, but because they could burn crappy cheap jet fuel. Thus a less efficient jet engine could run faster and cheaper than a piston-engined aircraft.
On a full tank of hydrogen peroxide the belt weighs 124 to 139 pounds (the bigger the pilot, the bigger the belt), and provides 30 seconds of flight.
From TFA.
The article appears to be from June 14, 2007. Here's one from this year:
http://www.popularmechanics.com/technology/aviation/diy-flying/martin-aircraft-jet-pack-for-sale
(from TFA) Widgery plans to release the T73 Turbine by the end of the year; it's a $200,000 model that will burn jet fuel, allowing it to stay airborne for 19 minutes.
... neither of them provide more performance than Captain Keds got out of his when he punched out of the big paper mache football and flew around the field at halftime of Superbowl 1 in 1967. Armadillo Aerospace is top notch in H2O2 propulsion systems, and they aren't building one. I bet there's a good reason.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
In 1980 they said that by 2010 some of us would be using jet packs to commute to work.
What they did not foresee in 1980 was the rise of telecommuting and that those same commuters would not have to travel very far.
Hence the need for only thirty seconds of flight time - it all make perfect sense.
TFA suggests that replacing "inert" hydrogen peroxide with propane will make jet packs more dangerous. Maybe, maybe not, but hydrogen peroxide is a powerful oxidant that attacks many organic compounds (eg people) and can explode. It's not inert by any stretch of the imagination - how useful would an inert rocket fuel be in any case?
Strapping a propane cylinder to your back might not be great either, but I suspect propane is easier to manage.
There's a summary of H202 safety risks here
Virtually serving coffee
The problem with jet packs has been specific impulse. You simply cannot get enough power density into something you can heft on your back and walk around with, at least not without any usable flight time or performance.
I've often thought small jet engines used in RC planes (~40lbs thrust) could be stacked up (6-8) of them to give you a jet pack. But nowadays you can buy a small jet engine designed for UAVs that might weighs 40 pounds and produces 200+ pounds of thrust, these kind of engines have been fitted to gliders.
In terms of a true jet pack. Allowing some weight for fins, a fuel tank and harness you have a 170lb dry weight with three engines. Not much of a real 'pack' then.
So the problems remain, even with the high specific impulse of a jet. You would need to add about your own weight in fuel for one hours flight time.
More ingenious gadget to me, would be a hot air balloon that fits and deploys from a backpack using the same technology that allows large parachutes to be packed into small spaces.
After logging in slashdot still does not take you back to the page you were on. It's been that way for 20 years.
I remember back in the early 80s some DoD contractor had a prototype of a flying "trashcan" like in the Dick Tray comics.
I thought it had some sort of jet engine with a steerable nozzle on the bottom. I think it was probably the Williams X-Jet, but I swear it was painted stealth black.
I used to dream about having one of those, and even as an adult I think it would be so cool to fly one of those around.
I'm guessing that the program probably got canceled because of stability problems. But I would expect that now, with high speed DSPs and gyros like Dean Kamen has used for his scooter and his ubercool wheelchair, that the stability problems could be overcome.
When information is power, privacy is freedom.
Since if it's anything close to the purity they used to use in ME-163 (T-Stoff) it'd give you severe chemical burns.
Did you know 80 to 90% of the moderators on slashdot wouldn't recognize a troll even if one dragged them under a bridge.
Just wear a pair of Depends(R). It'll cover the heat load of 30 seconds of flight, and the other kind of load encountered when a pilot discovers they have counted to 30 too slowly.
There is a reason why the term "rocket science" is used to suggest something is more than a bit difficult. But thank you for giving an old-timer a bit of amusement at the expense of what I suspect is one of today's teenagers.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Dunno about other humans, but for me it would be mostly about the "without a plane around me" part, when I have to travel long distance. Airlines suck, frankly.
I remember the last time I was in an aircraft, with some leg space that was too small even for a 5 ft tall woman who was with us, listening to a screaming kid, and peering down into some airliner joke food that was at most good for a goat, I remembered the famous Da Vinci quote, "When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return." I thought, you can tell the fucker never tasted _this_ kind of flight :p
If a jetpack could get me from here to there without that hassle, I'm all for it.
Heck, I'd even fork over the money for a zeppelin flight, if they can have some more humane accommodations.
A polar bear is a cartesian bear after a coordinate transform.
Bottom line: above a few thousand KW, piston engines for aircraft are simply too complex, expensive and unreliable. The fuel is immaterial.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
While I agree with your point that the jet is far superior to the ICE engine in everything but low power low cost flight, there's also truth in the OP's original statement about the inexpensive fuel being a valuable benefit of jet turbines. Some time ago, the rail industry started producing Jet Turbine locomotives due to the huge price differential between jet fuel, and diesel fuel. These engines enjoyed the power and weight benefits you describe, with the ability to burn oil that was unsuitable for use in ICE. They were eventually phased out as oil processing techniques improved, and the fuel became more valuable and expensive.
http://en.wikipedia.org/wiki/Union_Pacific_GTELs
The OP also makes a valuable point that Jet Fuel is not expensive or particularly exotic.
Batman has plans for every situation EVER.
In fact, someone "spilling" his plans online was probably his plan all along.
Heck... he has plans about things we can't even imagine happening.
Like DayGlo elephants with machine-guns for limbs raining from the sky. Why would he plan for such an occasion?
Because he is The Batman.
Mit der Dummheit kämpfen Götter selbst vergebens