Features, Future Please

Future, Please: Power Armor and Jet Packs

April 5, 2013

Science fiction provides inspiration and escape, but it’s also a project buffer for future engineers. Quirky and inspirational ideas, beyond reach of the writer’s contemporaries, can remain in circulation as fiction while the rest of the world catches up. In Future, Please, EngineerJobs looks at beloved and bizarre fictional gadgets and our attempts to realize them. First up: power armor and jet packs.


Power Armor

Heinlein’s Starship Troopers set the canon for armored combat exoskeletons, though he wasn’t the first to explore the idea. The first set of recognizable power armor in fiction was Edward S. Ellis’ “The Steam Man of the Prairies”, published in 1868, whose protagonist brought justice to the Western US from inside a steam-powered fighting machine. (Purists may rightly claim that Ellis’ Johnny Brainerd was a mech pilot, rather than a cap trooper.) Nonetheless, Heinlein’s vision is most often credited for inspiring modern powered exoskeleton development.

Early Days 

The first attempt to realize a powered exoskeleton for human enhancement used a system of gas bladders as crude pneumatic actuators. Invented by Nicholas Yagin in 1890, the idea came along too early for a supporting power system. It wasn’t until 1917 that steam engines were small and powerful enough to even design the pedomotor, a set of steam-powered legs, though Leslie Kelley’s invention never made it off the drawing board.

GE HARDIMAN Exoskeleton

The GE HARDIMAN Exoskeleton

Development was mostly fallow until the 1960s, when powered exoskeleton projects began at General Electric and Los Alamos labs. GE’s project, the Hardiman, is often honored as the first, true powered exoskeleton. Intended for industrial and commercial use, the suit amplified a user’s strength 25 times with electronically-controlled hydraulics. It was a monstrously unwieldy device, weighing over 1,500 lbs and incapable of moving more than 2.5 feet per second. Perhaps more importantly, feedback control of bipedal locomotion wasn’t possible with existing technology; when activated, the Hardiman’s legs became immediately, terrifyingly spastic. No human ever wore an active Hardiman, and the project was canceled in the early ’70s. The Los Alamos project, codenamed PITMAN, appears to have been an attempt to literally produce Heinlein’s power armor, but they never achieved a testable prototype.


Modern Exoskeletons

Monty Reed LIfesuit

Monty Reed in his LIFESUIT

After PITMAN and the Hardiman, power armor development stayed off the radar until the mid-1980s. A former Army Ranger named Monty Reed, hospitalized with a broken back, read Starship Troopers during his recovery. Explicitly inspired by the Mobile Infantry Power Suit, Reed’s LIFESUIT restores mobility to paralyzed or otherwise disabled people. Currently on its fourteenth iteration, the device has a range of one mile and can lift up to 200lbs. Reed, operating the LS12, holds the current Land Speed Distance Record for walking in a robotic exoskeleton.

If Heinlein’s power suits are the benchmark, however, the two most promising exoskeletons in development are the Sarcos/Raytheon XOS2 and the Cyberdyne Systems HAL-5, each representing different approaches to suit control and application.

The XOS2 started off as a DARPA project under Sarcos, but was acquired by Raytheon during development. The first field-capable generation will be in use by the US military soon, in supply and logistics applications. XOS2 monitors its user’s muscle contractions as a control interface and allows users to lift up to 200 lbs, with a actual-to-perceived weight ratio of 17:1. Currently, the suit operates for eight hours on an internal combustion hydraulics engine and weighs 200 lbs.

As the XOS2 is an active military project, your chances at getting a test drive are slim. You can rent a Cyberdyne HAL-5, on the other hand, for $2,000 a month – if you’re willing to move to Japan.


Cyberdyne’s HAL-5 Exoskeleton

The HAL-5 is in active use in Japanese hospitals as a mobility device and to assist health care workers; it is, in fact, the world’s first UL-certified robotic therapy device. Weighing only 22 lbs, the suit provides five times baseline human strength and takes control input by monitoring nerve impulses through sensors on the user’s skin. Cyberdyne produces a number of specialized HAL chassis, such as legs-only models or suits geared to specific industrial tasks. A HAL incorporating tungsten armor and hazmat protection is in the functional prototype stage, intended for workers dismantling the Fukushima reactor site.


Power Armor, Please

Exoskeletons are wonderful, but you can’t fight giant insects on alien worlds without a fully-armored, robust, and environmentally-sealed suit of power armor. There are a number of engineering challenges left between humanity and the Mobile Infantry Power Suit:

  1. Power supply must be light, dense, and cool. Current battery technology is ill-suited for combat environments, and our best internal combustion hydraulics engines are limited by the density of their fuel source. Solid oxide fuel cells are a possible alternative, but present their own problems; solid oxide cells function best at temperatures above 600C.
  2. Materials used in constructing the suit must be light enough to maintain agility and strong enough to withstand combat environments, while not being prohibitively expensive to produce.
  3. Joints must be enclosed, hardened, and able to reproduce the full range of human movement. NASA partially solved this issue in 1988 with the AX-5 hardshell suit, but its free bearing joints fouled too easily for field use.
  4. Movement Control has to be quick and fluid, for combat maneuvers, while still dampened to prevent Hardiman-style spastics or user injury (either by overextension or exceeding the human range of motion).
  5. Actuators must be lightweight, powerful, and energy efficient.

EngineerJobs will trade a lifetime supply of free PR for three mobile infantry suits. Any takers?

Editor’s Note: There are actually 5 of us so we’ll up the offer to lifetime free PR and a perma subscription to the Cupcake-of-the-Month Club.


Jet Packs

Jump Belts and Rocket Packs

The first rocket pack was the German Himmelstürmer (“Heaven Stormer”), referred to, in some sources, by the far less marketing-savvy name of Einpersonnenfluggerät (“One Personal Flying Apparatus”). It was in the functional prototype stage by the end of World War II but never saw mass production. The  Himmelstürmer was intended to allow combat engineers and light infantry units to cross minefields, rivers, and field fortifications through rocket-assisted leaps of up to 60 meters, with a maximum operating height of 15 meters.

Heaven Stormer Himmelsstürmer

A conceptual illustration of the Himmelsstürmer jet pack.

The Himmelstürmer used stripped-down Schmidt pulse jets in the front and back, similar to those on the V1, for main thrust and maneuvering.  Bell Aerosystems was tasked with testing and reproducing the Himmelstürmer, after the war, but their “jump belt” development program was abandoned by the late ’50s.

Instead, Bell focused on a hydrogen peroxide rocket pack. The first untethered rocket pack flight took place in 1961, just one week after Yuri Gagarin orbited the Earth. While Bell Aerosystems achieved twice the  Himmelstürmer’s range, their design was limited to a flight time of 21 seconds and required the user to wear specially designed heat-resistant clothing. The rocket belt was deployed in a number of high-profile photo opportunities and one James Bond film, but never pursued as useful military technology.


Prototypes and Powered Wings

DARPA funded a second project, also through Bell Aerosystems, to design a proper jet pack. Hydrogen peroxide rockets were too dangerous, inefficient, and volatile for practical military use, so it was hoped that use of turbojet engines would produce a more stable technology. After years of development, only one prototype was ever made, capable of 25 minutes of operation at 135 km/h. While the jet pack itself was abandoned as too expensive and cranky to maintain, a later version of its engines are still in use in the Tomahawk cruise missile.

The most successful jet pack in operation is Yves Rossy’s jet-powered wing. A former military and commercial pilot, Rossy designed, built, and flies his own rig. The design centers around four Jet-Cat P200 kerosene-powered jet engines and a semi-rigid carbon fiber wings, with a span of 2.4 m. Rossy typically launches from a small airplane or hot air balloon, and landing is accomplished by parachute.

Yves Rossy’s jet-powered wing

Yves Rossy’s Jet-powered wing

His first public demonstration flight was no 20-meter rocket hop; in 2008, Rossy crossed the Alps at at average speed of 200 km/h. He has made a number of high-profile flights over the years, including crossings of the English Channel and Grand Canyon.

The FAA officially classified Rossy’s jet pack as an aircraft in 2011.


Jet Pack, Please.

Rocket belts and jet packs resist widespread adoption by commercial or military interests. If we want to trade in our cars for personal jet packs, we need engineers to solve a few outstanding problems:

  1. Propulsion via available jets or rockets is inefficient. Rossy achieves his flight distances only by launching from an aerial platform, like a balloon or small plane; if he had to launch from a standing position with a hydrogen peroxide rocket, his unit would be crippled by the 15 m elevation. For effective flight, we need either a new means of propulsion or fuels with a much greater energy density.
  2. Control and balance are quite difficult, as the human body is terribly adapted for flight. Slight movements of the head, arms, or legs while flying at speed can easily send a jet-pack pilot out of control. A lightweight means of steering and maintaining orientation is needed, but the solution has to maintain the essential character of a jet pack to avoid becoming a wearable ultralight.
  3. Safety is a huge concern. Existing rocket belts operate below effective parachute height, and the Rossy jet-powered wing is very vulnerable to wind conditions. Aside from falling out the sky, however, the propulsion reaction itself can be quite hazardous; the exhaust stream of a hydrogen peroxide rocket is 740C. 

Hopefully, we’re in the early days of personal flight. As it stands, however, jet packs and rocket belts are deadly, impractical, and extremely expensive. If the development of power armor is any example, however, there remains cause for optimism. So long as the idea of a personal jet pack circulates, in fiction and imagination, future engineers and tinkerers will be inspired to take up the problem. 

Our best bet may be to keep Starship Troopers in print.