The Ephemerality and Reality of the Jetpack 127
First time accepted submitter Recaply writes "Here's a look back at the 1960's Bell Aerosystems Rocket Belt. 'Born out of sci-fi cinema, pulp literature and a general lust for launching ourselves into the wild blue yonder, the real-world Rocket Belt began to truly unfold once the military industrial complex opened up its wallet. In the late 1950s, the US Army's Transportation Research Command (TRECOM) was looking at ways to augment the mobility of foot soldiers and enable them to bypass minefields and other obstacles on the battleground by making long-range jumps. It put out a call to various aerospace companies looking for prototypes of a Small Rocket Lift Device (SRLD). Bell Aerospace, which had built the sound-barrier-breaking X-1 aircraft for the Army Air Forces, managed to get the contract and Wendell Moore, a propulsion engineer at Bell became the technical lead.'"
Re:Almost as if (Score:4, Insightful)
Space elevators and asteroid mining can make sense too, but in those cases (assuming the space elevator can actually be built, which it can't with today's materials) it becomes a cost/benefit analysis. Is it cheaper to mine asteroids, or get the same materials here on earth? As soon as it's cheaper to get them from asteroids, we will get them from asteroids. Is it cheaper to get things into orbit via space elevator? We don't know yet, but if it is, then we will build a space elevator.
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Flanking maneuvers? "Hey everybody, shoot the loud flying things over there!"
A flanking maneuver doesn't need to be a surprise. It just needs to be fast enough to get into position before the defenders can rearrange themselves.
I don't know what place they would have on a modern battlefield.
Whether they have a place on the modern battlefield is equal to the question of whether infantry has a place on the modern battlefield. If they do, then having a mobile infantry is an advantage.
Starship Troopers (Score:2)
"Whether they have a place on the modern battlefield is equal to the question of whether infantry has a place on the modern battlefield. If they do, then having a mobile infantry is an advantage."
There is a big difference between what the jet pack can do, and what the armored suits of the "Mobile Infantry" could do. For a start they had nuclear power, so could keep flying for hours not minutes. And of course they were fighting in alien worlds, there were no civilians around to worry about collateral damage.
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There is a big difference between what the jet pack can do,
Yes, that is why the discussion is about what a jet pack could do if the practical limitations were overcome. Context is important.
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Whether they have a place on the modern battlefield is equal to the question of whether infantry has a place on the modern battlefield. If they do, then having a mobile infantry is an advantage.
Mobile infantry made me the man I am today.
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Whether they have a place on the modern battlefield is equal to the question of whether infantry has a place on the modern battlefield.
No, its not.
Infantry are mobile, versatile, able to perform precision strikes, able to adapt to many situations.
Rocket belts are heavy, unwieldy, unreliable, expensive, noisy, and incredibly niche. Im sure there are circumstances where it happens to be the right tool for the job, Im just not sure what that might be or why youd want to weigh all of your infantry down with it for that one circumstance.
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That might be the case, but it might also not be the case.
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If the ability to fly is important, as opposed to traveling over the ground, you're close enough to get shot while you're flying
Don't fly so close to the guns!
I DON'T HAZ ROKIT BELT (Score:2)
WANTZ tehze CHUCKs, with ZIP on SIDEZ!
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this sounds like computer game logic, not military thinking.
Wars are games. Like Risk or Chess, but with real people. Many of the tactics used were thought up in game-like ways.
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"Flank from above"? Seriously?
That was a direct quote from the person I was responding to (well, their link).
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miniature silent version
Ah.
That would be called a drone.
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miniature silent version
Ah.
That would be called a drone.
You know that they're anything but "silent", right?
"Silent" is a relative term, depending on how close you are and how sensitive your pick-up. A drone can be made as quiet as anything with powered flight can be made, and with sufficient altitude you won't be able to hear it.
There is abundant evidence that with suitable operation many U.S. reconnaissance drones routinely operate without audible detection.
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but no one mentions the Martin http://www.youtube.com/watch?v... [youtube.com]
Re:Almost as if (Score:5, Funny)
Jetpacks make sense if you can get them to work.
As would many, many other things, like Warp Drive [wikipedia.org] and the G Spot [wikipedia.org].
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G-spot? That's crazy talk.
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I think the biggest problem with jetpacks is the logistics of carrying them when you're not actually jetting about with them. They were simultaneously bulky, fragile, and extremely combustible. Plus, the things weighed 60 kg when fueled, and this would almost double the normal amount of weight the average infantryman is required to carry. Even if they had a specific military purpose, getting them to the soldiers who need them at the exact time they need them is problematic.
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How about an army of autogyros, droned with the human shooting from it as a flying weapon platform? That sounds like an evolution of the
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Youre still carrying a massive extra load just for that one time you happen to need jumpjets.
We have a lot of other ways of accomplishing the things a jumpjet does without all of the ridiculous complexity and logistics it requires.
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And you need to bring up your man-catapults before attack.
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Or just make the Humvees fly.
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For the military, I'd go with jump-jets. The "launch" is taken care of by a catepult....
Where I have seen this before? Oh, right. "Run away, run aw-a-a-y...".
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Alernatively, imagine how many more soldiers you could pay for and equip instead of issuing these jetpacks to all of them. You essentially have a choice between more soliders with more versatile gear and better mobility, or rocket soldiers who get one 20 second instance of unstable flight before needing to refuel-- not to mention the tax on their mobility all the rest of the time.
Yea, Ill take more soldiers, thanks. If you need air support, thats what the air force is for.
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Space elevators proponents always miss one very important detail. If you have the material to make the elevator, you can use that material to make traditional rockets too. And it may well make rockets cheaper than a el
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Space elevators proponents always miss one very important detail. If you have the material to make the elevator, you can use that material to make traditional rockets too. And it may well make rockets cheaper than a elevator.
I always thought the most expensive component of a rocket was the fuel, but who knows
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Space elevators proponents always miss one very important detail. If you have the material to make the elevator, you can use that material to make traditional rockets too. And it may well make rockets cheaper than a elevator.
I always thought the most expensive component of a rocket was the fuel, but who knows
This has the matter completely upside down. For rockets the fuel is essentially free (compared to the rocket itself). Honest!
Consider the Delta 7000, an inexpensive launcher that cost $70 million to launch in 2006 dollars. The whole launch system weighed at least 180,000 kg and it burned (except for the boosters) LH2/LOX. Assume as a limiting case that the entire launch weight is fuel - in that case the fuel is 20,000 kg of hydrogen and 160,000 kg of oxygen. How much does LH2 and LOX cost? For LH2 it is abo
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Although making rockets out of nanotube carbon fiber would certainly reduce the weight, it wouldn't reduce it that much. You forget that the bulk of a rocket's weight is fuel; eliminating that is the "big win" a space elevator provides.
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There are a few minor practical problems with jet packs, or more properly, rocket packs as these devices are rockets, not turbojets, and it matters. It matters because there are some pretty fundamental limits on how much fuel/reaction mass a soldier can carry, especially when they have to carry other stuff like body armor, weapons, helmets, ammunition, food, shelter. Let's imagine that a stripped down soldier carrying little but armor, ammo and a rifle has a mass of 100 kilograms, 90 kilograms of which ar
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Jet packs make sense if you can get them to work.
There's the rub right there. Feasibility is a prerequisite of "making sense", and in the real world you have to deal with physics and the physical limitations of human beings. Antigravity would "make sense" if you could get it to work.
The physics of a jet pack are governed by the rocket equation: V = Ve * ln(Mt/Mp). You need to carry enough mass, ejected at a sufficient speed, to produce 9.8 m/s v every second.
The upshot is that to counterbalance the weight of a soldier and his gear you can either have
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To increase the burn time you'd need to carry more fuel than a man could lift.
Nah, all you really need is an arc reactor. Then you're good.
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You know, you touch on something that bugged me when I watched the Iron Man movies. Where is the reaction mass for Iron Man's flight coming from? Even a lightweight, unlimited power source wouldn't solve the problem of reaction mass. The Iron Man suit obviously uses some kind of reactionless drive -- not inconceivable, given that it also has "repulsor" technology which has no plausible physical explanation and violates classical physics.
The arc reactor idea actually is interesting to think about. Suppose y
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The arc reactor idea actually is interesting to think about. Suppose you had an unlimited energy source with negligible weight. Could you build something like a rocket belt? I think you could, say by driving a turbine or some more exotic method of accelerating air.
My guess is yes. I feel like one of these approaches at least [wikipedia.org] would be able to take advantage of a massive energy source.
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Suppose you had an unlimited energy source with negligible weight.
Pratt and Whitney's impressive trimodal nuclear [alternatewars.com] rocket [archive.org] seems relevant (sorry about the weird links, this engine has largely disappeared from the internet). Some of the ideas and materials in this design would not doubt be applicable to a rocket belt regardless of the nuclear capability.
sound-barrier-breaking X-1 aircraft (Score:3)
...as opposed to the rocket belt, which was merely eardrum-breaking...
This Day on Slashdot (Score:1)
I know it's offtopic and all, but is it just me, or has this not changed in like a week or more?
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We had to disable updates to most of the Slashboxes, including 'This Day on Slashdot' in order to fix an underlying issue in the code. The work should be completed soon, at which point we'll re-enable everything. Apologies for the inconvenience!
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I am detecting a significantly elevated level of story quality and of course, beta changes, in the last week or so. I guess you guys really did listen...eventually.
Can we discount the possibility that the (Score:2)
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No.
Kids these days...*sigh.
Chuck Taylor's couldn't hold one of the PF Flyers shoestrings!
PF Flyers even came with a 'Magic Ring' that done encoding and decoding...Johnny Quest would never lie to me.
Ankles are lousy landing gear (Score:5, Interesting)
A big problem with jetpacks is that human ankles are weak landing gear. You can't do a parachute landing fall while wearing a jetpack; you have to do a standing landing. With all the mass of the gear on your back.
The other big problem is that rocket systems have a short flight time, and jet engine systems are too expensive. The jet engine powered backpack [youtube.com] worked well, but cost too much. That used a small Williams jet engine. Williams International has tried and tried to make small jet engines cheaper. So have many others. Unfortunately, that's a very hard problem, which is why general aviation is still piston-powered. Below small-bizjet size, jet engines don't seem to get much cheaper as they get smaller. There was a big effort about a decade ago to develop "very light jets", but they ended up costing well over $1 million, most of that being engine cost.
So it can be done, and it has been done, but it just doesn't work very well.
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That and stabilization.
It is easy to launch someone into the air with just a moderate amount of explosives, or a jet engine strapped to your back, doing so in a slow controlled manner when we are talking at least 300 pounds of human, their gear, and the jetpack itself is a whole lot harder. Add to that this engine or rocket has to be in direct contact with a living human being for an extended period.
Practically, you are not going to create a solution light enough to carry around just in-case it is needed. M
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I think they could solve stabilization with modern electronics. Kid's toy quadcopters are already self leveling, and as they weigh much less thank a kilogram, they're far more "twitchy" than 150kg of inertia carried about by the humans and their gear.
As you mentioned, it's the soldier who has to carry the additional 60kg pack that is the real limit.
Re: Ankles are lousy landing gear (Score:1)
Two words:
Robotic Exoskeleton
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Practically, you are not going to create a solution light enough to carry around just in-case it is needed. Maybe you could create something that is usable, but it will be so heavy that, best case scenario, it would just be carry-able by a single man without too much extra gear, and more likely it would be a very limited range vehicle that needed to be transported to where it was to be used by plane or truck
Which is why we still use helicopters. We haven't really figured a way to scale that type of mobility down to a single person. And frankly speaking, unless we get moving on actual mechanized battle-suit technology, we won't. The ultimate problem is your power source, getting it small and light enough while maintaining enough power to be useful.
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Based on the prices of some programs, I don't think that "too expensive" is an issue.
When killing people is concerned, I think that no price is too high for our military.
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Price will lower when they will be able to simply print it.
Pretty sure 3-D printing is more expensive than other mass-manufacturing processes (injection molding). The advantage of 3-D printing is, you can do it at home, and in single quantities, it is cheaper.
But if you're expecting 3-D printing to eventually make everything cheaper, you'll probably be disappointed. The most that could be expected is to bring the costs of custom items be the same as mass-manufactured items. Which is still a good thing.
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Anyone expecting printed materials to survive environments typically found inside jet or rocket engines needs to be awfully patient.
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You aren't going to see huge improvements in designs anymore IMO, just some tweaks in manufacturing processes. SLS can do things like progressively blend from one alloy to another in one part. How much that helps I don't know.
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Anyone expecting printed materials to survive environments typically found inside jet or rocket engines needs to be awfully patient.
Or, you know, NASA. [parabolicarc.com]
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One notes that this part is not *inside* the engine, but is a port cover for a secondary system. Pump exhaust covers/baffles, yes. Turbine blades? Not so much.
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or just competent (of course being both patient an (Score:1)
http://www.nasa.gov/press/2013/august/nasa-tests-limits-of-3-d-printing-with-powerful-rocket-engine-check/#.UxSiDvRdU9c
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transmission stations
Also known as "death rays". Dont let China see you pointing it at you or you may see your solar panels destroyed.
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What 3D printers were used in the 80s?
3D Systems was founded in 1986. [3dsystems.com] Stereolithography is older than many people think it is. Early systems produced rather fragile objects, but product designers in the late 1980s were using them to make product models.
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Williams WASP X-Jet (Score:5, Interesting)
This is the reality of how to make a single man fly.
Williams WASP X-Jet [youtube.com]
It worked, it flew, there was no military justification for it, it disappeared.
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It worked, it flew, there was no military justification for it, it disappeared.
Specifically, with fuel lasting only 30 minutes, it didn't have much practical application.
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As I understood it the designer behind that one is a one which worked with Moore until he died (at age 54?) and later continued with the work.
I'm not all that surprised there wasn't much interest for that can though. Then again maybe it was awesome to avoid branches, offer some protection, let you carry gear / rifle, .. Maybe it just looked worse :)
They all controlled great :)
Holy Crap! (Score:2)
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AFAIK power density hasnt really changed that much. You have a pretty fundamental limit on how long flight lasts given a fuel density and a payload.
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I remember seeing this on a TV science program in the 1980's when I was at university in New Zealand. I'm pretty sure that it would have been mentioned in science magazines like "Popular Science" and "Popular Mechanics" - it was well-known at the time.
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To be fair, it could be defeated completely by wearing the crocodile mask.
1950s (Score:4, Insightful)
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Also the way things scale means its easier and cheaper to make some of these things bigger. So its cheaper to make a 2 man-4 man helicopter than a one man jet pack. Range is always a problem with smaller things because of the cube law.
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--Jet packs will likely be much more feasible if/when we start colonizing other planets. If you can get to 60-70% of Earth's gravity or lower, it will be much easier to fly.
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Like another problem (Score:2)
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Jetpacks, flying cars - same problme (Score:5, Informative)
We don't see jetpacks or flying cars for the very same physics reason. In order to hover against gravity you need to produce thrust > weight. Since thrust is proportional to (mass/second) X velocity, and power is proportional to (mass/second) X velocity^2, an efficient source of thrust you want to move a lot of material slowly (assuming you have unlimited reaction mass -> the atmosphere).
So, things that hover need to move lots of air, and have great big propellers. That is why helicopters work, and jet-reaction cars are too inefficient to be practical. It is why airplanes have big wings, not stubby lifting bodies. There may be a few spacial cases where you are willing to tolerate inefficiency, but they are rare.
Planes look like planes for a reason. Helicopters look like helicopters for a reason.
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Stubby lifting bodies can be practical at interesting cruise speeds, but you wouldn't want to take off or land at such speeds. Adding VTOL capability would solve that problem, but then we are back to the big and slow propellers issue you explained so well. I believe it is possible to convert a small, low thrust, high speed jet to a high thrust, low speed one with no moving parts. Air amplifiers actually increase thrust below 5cm in diameter but reduce it for larger sizes, so you have to figure out why it do
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I didn't know that air amplifiers didn't scale, but also didn't know how efficient they were. Turbulent systems can be very non-intuitive - some airplanes have small vortex generators (tabs on the to of the wing that stick into the air flow) because they decrease drag. (they prevent boundary layer separation, but it still feels like exactly the wrong thing to do.....
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Fluids "love" to twist, so laminar flows (such as the curtain of air along the inner surface of air amplifiers) don't always get the best results. The laminar flows seem so quiet and smooth so it is hard for our intuition not to consider them to be the way to move mass with the least energy.
Vortices can scale very well. I always point to the Red Spot on Jupiter as an example. Can one be generated on a scale that could keep a car or a person suspended in mid air while using less fuel than a helicopter? I thi
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Schlock says... (Score:1)
Wisdom from http://www.schlockmercenary.com/2011-05-28
corporal: "Do you know what we call flying soldiers on the battlefield?"
private: "Air support?"
corporal: "skeet"
What if multiple contracts were awarded? (Score:2)
I wonder how things would have been different if multiple identical R&D contracts were awarded to several companies so as to set up competition for the best technology. Basically, set aside R&D money to be given to a company so there is disincentive to risk their own money. I would also throw in there that R&D awards be given to startups rather than huge public companies.
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Because contract competition in the early 1960s would have circumvented the fundamental limits of engineering and materials and produced something that cannot be made in 2014?
Note that there have been dozens of small "flying man" devices from the late 1950s to the present day, none of them practical for any important application. The limits of fuels and propulsion systems constrain everyone and even modern computers and composite materials aren't making flying belts practical today.
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For the search part, a UAV would probably be a cheaper way to put sensors in the air. For the rescue part, you need to hover and lift quite a bit of weight. Consider that many victims need some medical attention or at least assistance in getting aboard the rescue craft. So that means a crew of several people plus rescue gear (basket, stretcher, etc.). Well beyond the capabilities of a jet pack and even some small helicopters.
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Although, much like the paramedics on bicycles or motorbikes, getting somewhere first, even if you can't get back out again is sometimes useful.
As someone above said though, lugging a couple of these about the place, just in case you need to get one person somewhere really quickly seems like an awful overhead for a one-time, niche use.
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Jetpacks are better for civilian rather than military use, e.g. search & rescue;
http://www.martinjetpack.com/
That's not a jetpack, it's a lightweight vehicle. A Jet PACK is something you can pick up with one hand and carry around on your back. This shit isn't it, so stop whoring for page hits asshole.
So the rocket belt was NOT a "jet PACK" by your criteria since at 57 kg you could NOT pick it up with one hand (unless you were perhaps a professional body builder).
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http://www.martinjetpack.com/
Sigh. Calling shit like this a "jetpack" is highly misleading at best. It's not a pack, it's a light-weight vehicle with an open cock-pit that you strap yourself to.
He should have cited the Bell Jet Flying Belt [wikipedia.org] - a flight pack that incorporated a turbofan engine, not a rocket. It could fly up to 25 minutes, with the far more efficient use of fuel (air was essentially the propulsion fluid).
The entire point of calling something a "jetpack" is that it's a PACK which you can strap to your back, pickup with one hand, and hike around with until such a time as you need to use it.
Or not. Did you check out the rocketpack weight? It was 57 kilograms. No one is going to do much hiking "around with until such a time as you need to use it" with that much deadweight - the guy is grossly-overloaded without carrying anything else. The U.S. Army's recommended combat lo [thedonovan.com]