Jet packs | Wikipedia audio article
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Jet packs | Wikipedia audio article

August 10, 2019


A jet pack, rocket belt, or rocket pack is
a device worn on the back which uses jets of gas or liquid to propel the wearer through
the air. The concept has been present in science fiction for almost a century and became widespread
in the 1960s. Real jet packs have been developed using a variety of mechanisms, but their uses
are much more limited than their fictional counterparts because of the challenges of
Earth’s atmosphere, gravity, low energy density of available fuels, and the human body not
being suited to fly, and they are principally used for stunts. A practical use for the jet
pack has been in extra-vehicular activities for astronauts.==Overview==
In the most general terms, a jet pack is a wearable device which allows the user to fly
by providing thrust. With the exception of use in a microgravity environment, this thrust
must be upwards so as to overcome the force of gravity, and must be enough to overcome
the weight of the user, the jet pack itself and its fuel. This necessarily requires the
jet pack to continually push mass in a downwards direction.While some designs have power and/or
mass supplied from an external, ground-based source, untethered flight requires all of
a flight’s fuel to be carried within the pack. This results in problems relating to the overall
mass ratio, which limits the maximum flight time to tens of seconds, rather than the sustained
flight envisaged in science fiction.==Liquid-fuelled rocket pack=====Andreyev: oxygen-and-methane, with wings
===The first pack design was developed in 1919
by the Russian inventor Aleksandr Fyodorovich Andreyev. The project was well regarded by
Nikolai Rynin and technology historians Yu. V. Biryukov and S. V. Golotyuk. Later it was
issued a patent but apparently was not built or tested. It was oxygen-and-methane-powered
(likeliest a rocket) with wings each roughly 1 m (3 feet) long.==Hydrogen peroxide-powered rocket packs
==A hydrogen peroxide-powered engine is based
on the decomposition reaction of hydrogen peroxide. Nearly pure (90% in the Bell Rocket
Belt) hydrogen peroxide is used. Pure hydrogen peroxide is relatively stable, but in contact
with a catalyst (for example, silver) it decomposes into a mixture of superheated steam and oxygen
in less than 1/10 millisecond, increasing in volume 5,000 times: 2 H2O2 → 2 H2O +
O2. The reaction is exothermic, i.e., accompanied by the liberation of much heat (about 2,500
kJ/kg [5,800 BTU/lb]), forming in this case a steam-gas mixture at 740 °C [1,360 °F].
This hot gas is used exclusively as the reaction mass and is fed directly to one or more jet
nozzles. The great disadvantage is the limited operating
time. The jet of steam and oxygen can provide significant thrust from fairly lightweight
rockets, but the jet has a relatively low exhaust velocity and hence a poor specific
impulse. Currently, such rocket belts can only fly for about 30 seconds (because of
the limited amount of fuel the user can carry unassisted).
A more conventional bipropellant could more than double the specific impulse. However,
although the exhaust gases from the peroxide-based engine are very hot, they are still significantly
cooler than those generated by alternative propellants. Using a peroxide-based propellant
greatly reduces the risk of a fire/explosion which would cause severe injury to the operator.
In contrast to, for example, turbojet engines, which mainly expel atmospheric air to produce
thrust, rocket packs are far simpler to build than devices using turbojets. The classical
rocket pack construction of Wendell Moore can be made under workshop conditions, given
good engineering training and a high level of tool-making craftsmanship.
The main disadvantages of this type of rocket pack are: Short duration of flight (a maximum of around
30 seconds). The high expense of the peroxide propellant.
The inherent dangers of flying below minimum parachute altitude, and hence without any
safety equipment to protect the operator if there is an accident or malfunction.
Safely learning how to fly it, given that there are no dual-control training versions.
The sheer difficulty of manually flying such a device.These circumstances limit the sphere
of the application of rocket packs to very spectacular public demonstration flights,
i.e., stunts; for example, a flight was arranged in the course of the opening ceremony of the
1984 Summer Olympic Games in Los Angeles, USA.===Justin Capră’s flying backpack===
Justin Capră claimed that he invented a “flying rucksack” (Romanian: rucsac zburator) in 1956
in Romania, and, without arousing any apparent interest, informed the American Embassy of
his idea. In 1962 a backpack was created at Bell Laboratories, following Justin Capră’s
prototype. The backpack is now displayed in a museum where it’s kept safe.===Jump Belt===
In 1958, Garry Burdett and Alexander Bohr, Thiokol Corporation engineers, created a Jump
Belt which they named Project Grasshopper. Thrust was created by high-pressure compressed
nitrogen. Two small nozzles were affixed to the belt and directed vertically downward.
The wearer of the belt could open a valve, letting out nitrogen from the gas cylinder
through the nozzles, which tossed him upward to a height of 7 m (23 ft). After leaning
forward, it was possible with the aid of the jump belt’s thrust to run at 45 to 50 km/h
(28 to 31 mph). Later, Burdett and Bohr tested a hydrogen peroxide-powered version. The jump
belt was demonstrated by a serviceman in action, but as no financing was forthcoming, there
was no further testing.===Aeropack===
In 1959 Aerojet General Corporation won a U.S. Army contract to devise a jet pack or
rocket pack. At the start of 1960 Richard Peoples made his first tethered flight with
his Aeropack.===U.S. Army interest===
The military did not lose interest in this type of flight vehicle. Transport studies
of the U.S. Army Transportation Research Command (TRECOM) determined that personal jet devices
could have diverse uses: for reconnaissance, crossing rivers, amphibious landing, accessing
steep mountain slopes, overcoming minefields, tactical maneuvering, etc. The concept was
named “Small Rocket Lift Device”, SRLD. Within the framework of this concept the administration
concluded a big contract with the Aerojet General company in 1959 to research the possibility
of designing an SRLD suitable for army purposes. Aerojet came to the conclusion that the version
with the engine running on hydrogen peroxide was most suitable. However, it soon became
known to the military that engineer Wendell Moore of the Bell Aerosystems company had
for several years been carrying out experiments to make a personal jet device. After becoming
acquainted with his work, servicemen during August 1960 decided to commission Bell Aerosystems
with developing an SRLD. Wendell Moore was appointed chief project engineer.===Bell Textron Rocket Belt===In 1960, the Bell Rocketbelt was presented
to the public. The jet of gas was provided by a hydrogen peroxide-powered rocket, but
the jet could also be provided by a turbojet engine, a ducted fan, or other kinds of rockets
powered by solid fuel, liquid fuel or compressed gas (usually nitrogen).
This is the oldest known type of jet pack or rocket pack. One Bell Rocket Belt is on
display at the Smithsonian Institution’s National Air and Space Museum annex, the Steven F.
Udvar-Hazy Center, located near Dulles Airport.===RB-2000 Rocket Belt===This was a successor to the Bell Rocket Belt.===Bell Pogo===The Bell Pogo was a small rocket-powered platform
that two people could ride on. Its design used features from the Bell Rocket Belt.===Powerhouse Productions Rocketbelt===More commonly known as “The Rocketman”, Powerhouse
Productions, owned and operated by Kinnie Gibson, manufactures the 30 second flying
Rocketbelt (June 1994) and organizes Rocketbelt performances. Since 1983 Powerhouse Productions
has performed show flights in over 40 countries such as the Carnival in Rio de Janeiro, Super
Bowls, the Rose Parade, Daytona 500, and the Michael Jackson Dangerous World Tour, as well
as many television shows including Walker, Texas Ranger, The Fall Guy and NCIS. Powerhouse
Rocketbelt pilots include stuntman Kinnie Gibson and Dan Schlund.===Jetpack International===
Jetpack International made three types of wingless jet packs: A Jet Pack H202 was flown for 34 seconds in
Central Park on the 9 April 2007 episode of the Today Show and sold for $150,000. As of
January 2009 their H202 jet packs are for demonstration only, not for sale. Details
of the likely consumer model “Falcon” were scheduled for an official announcement on
May 1, 2012, but the company is currently behind schedule.===Current technology===
At the TechCrunch Disrupt conference in 2014, Astro Teller, head of Google X (Google’s research
laboratory), said they investigated jetpacks but found them too inefficient to be practical,
with fuel consumption as high as 940 L/100 km (1⁄4 mpg‑US), and were as loud as a
motorcycle, so they decided not to pursue developing them.In recent years, the rocket
pack has become popular among enthusiasts, and some have built them for themselves. The
pack’s basic construction is rather simple, but its flying capability depends on two key
parts: the gas generator, and the thrust control valve. The rocket packs being built today
are largely based on the research and inventions of Wendell Moore at Bell Helicopter.
One of the largest stumbling blocks that would-be rocket pack builders have faced is the difficulty
of obtaining concentrated hydrogen peroxide, which is no longer produced by many chemical
companies. The few companies that produce high-concentration hydrogen peroxide only
sell to large corporations or governments, forcing some amateurs and professionals to
set up their own hydrogen peroxide distillation installations. High-concentration hydrogen
peroxide for rocket belts was produced by Peroxide Propulsion (Gothenburg, Sweden) from
2004 to 2010, but after a serious accident Peroxide Propulsion stopped making it.==Turbojet packs==
Packs with a turbojet engine are fueled with traditional kerosene-based jet fuel. They
have higher efficiency, greater height and a duration of flight of many minutes, but
they are complex in construction and very expensive. Only one working model of this
pack was made; it underwent flight tests in the 1960s and at present it no longer flies.
Jet packs and rocket packs have much better flight time on a tankful of fuel if they have
wings like an aeroplane’s.===Bell Jet Flying Belt: wingless===
In 1965 Bell Aerosystems concluded a new contract with the Defense Advanced Research Projects
Agency (DARPA) to develop a jet pack with a turbojet engine. This project was called
the “Jet Flying Belt”, or simply the “Jet Belt”. Wendell Moore and John K. Hulbert,
a specialist in gas turbines, worked to design a new turbojet pack. Williams Research Corporation
(now Williams International) in Walled Lake, Michigan, designed and built a new turbojet
engine to Bell’s specifications in 1969. It was called the WR19, had a rated thrust of
1,900 newtons (430 lbf) and weighed 31 kg (68 lb). The Jet Belt first flew free on 7
April 1969 at the Niagara Falls Municipal Airport. Pilot Robert Courter flew about 100
m (330 ft) in a circle at an altitude of 7 m (23 ft), reaching a speed of 45 km/h (28
mph). The following flights were longer, up to 5 minutes. Theoretically, this new pack
could fly for 25 minutes at velocities up to 135 km/h (84 mph).
In spite of successful tests, the U.S. Army lost interest. The pack was complex to maintain
and too heavy. Landing with its weight on their back was hazardous to the pilot, and
catastrophic loss of a turbine blade could have been lethal.
Thus, the Bell Jet Flying Belt remained an experimental model. On 29 May 1969, Wendell
Moore died of complications from a heart attack he had suffered six months earlier, and work
on the turbojet pack was ended. Bell sold the sole version of the “Bell pack”, together
with the patents and technical documentation, to Williams Research Corporation. This pack
is now in the Williams International company museum.
The “Jet Belt” used a small turbofan engine which was mounted vertically, with its air
intake downward. Intake air was divided into two flows. One flow went into the combustion
chamber, the other flow bypassed the engine, then mixed with the hot turbine gases, cooling
them and protecting the pilot from the high temperatures generated. In the upper part
of the engine the exhaust was divided and entered two pipes which led to jet nozzles.
The construction of the nozzles made it possible to move the jet to any side. Kerosene fuel
was stored in tanks beside the engine. Control of the turbojet pack was similar to the rocket
pack, but the pilot could not tilt the entire engine. Maneuvering was by deflecting the
nozzles. By inclining levers, the pilot could move the jets of both nozzles forward, back,
or sideways. The pilot rotated left/right by turning the left handle. The right handle
governed the engine thrust. The jet engine was started with the aid of a powder cartridge.
While testing this starter, a mobile starter on a special cart was used. There were instruments
to control the power of the engine, and a portable radio to connect and transmit telemetry
data to ground-based engineers. On top of the pack was a standard auxiliary landing
parachute; it was effective only when opened at altitudes above 20 m (66 ft). This engine
was later the basis for the propulsion units of Tomahawk and other cruise missiles.===Visa Parviainen’s jet-assisted wingsuit
===On 25 October 2005 in Lahti in Finland, Visa
Parviainen jumped from a hot air balloon in a wingsuit with two small turbojet jet engines
attached to his feet. Each turbojet provided approximately 160 N (16 kgf) of thrust and
ran on kerosene (Jet A-1) fuel. Parviainen apparently achieved approximately 30 seconds
of horizontal flight with no noticeable loss of altitude.===Yves Rossy’s jet wingpack===Swiss ex-military and commercial pilot Yves
Rossy developed and built a winged pack with rigid aeroplane-type carbon-fiber wings spanning
about 2.4 m (8 ft) and four small kerosene-burning Jetcat P400 jet engines underneath; these
engines are large versions of a type designed for model aeroplanes. He wears a heat-resistant
suit similar to that of a firefighter or racing driver to protect him from the hot jet exhaust.
Similarly, to further protect the wearer, the engines are modified by adding a carbon
fiber heat shield extending the jet nozzle around the exhaust tail.
Rossy claims to be “the first person to gain altitude and maintain a stable horizontal
flight thanks to aerodynamic carbon foldable wings”, which are folded by hinges at their
midpoint. After being lifted to altitude by a plane, he ignites the engines just before
he exits the plane with the wings folded. The wings unfold while in free-fall, and he
then can fly horizontally for several minutes, landing with the help of a parachute. He achieves
true controlled flight using his body and a hand throttle to maneuver; jet wingsuits
use small turbojets, but differ from other aircraft in that the fuselage and flight control
surfaces consist of a human.The system is said by Rossy to be highly responsive and
reactive in flight, to the point where he needs to closely control his head, arm and
leg movements to avoid an uncontrolled spin. The engines on the wing must be aligned precisely
during set-up, also to prevent instability. An electronic starter system ensures that
all four engines ignite simultaneously. In the event of a spin, the wing unit can be
detached from the pilot, and pilot and wing unit descend to Earth separately, each with
a parachute. Since 2007, Rossy has conducted some of his
flight tests from a private airfield, Skydive Empuriabrava, in Empuriabrava (Girona, Costa
Brava), Spain. Rossy’s jet pack was exhibited on 18 April 2008 on the opening day of the
35th Exhibition of Inventions at Geneva. Rossy and his sponsors spent over $190,000 to build
the device. His first successful trial flight was on 24 June 2004 near Geneva, Switzerland.
Rossy has made more than 30 powered flights since. In November 2006 he flew with a later
version of his jet pack. On 14 May 2008 he made a successful 6-minute flight from the
town of Bex near Lake Geneva. He exited a Pilatus Porter at 2,300 m (7,500 ft) with
his jet pack. It was the first public demonstration before the world’s press. He made effortless
loops from one side of the Rhone valley to the other and rose 790 m (2,600 ft).
It has been claimed that the military was impressed and asked for prototypes for the
powered wings, but that Rossy kindly refused the request stating that the device was only
intended for aviation enthusiasts.On 26 September 2008, Yves successfully flew across the English
Channel from Calais, France, to Dover, England, in 9 minutes, 7 seconds. His speed reached
300 km/h (190 mph) during the crossing and was 200 km/h (120 mph) when he deployed the
parachute. Since then he has—in several flights—managed
to fly in a formation with three military jets and cross the Grand Canyon, but he failed
to fly across the Strait of Gibraltar—he made an emergency landing in the water.
On 13 October 2015 a show flight was performed in Dubai. Two jet packs operated by Rossy
and Vince Reffet flew in formation with an Airbus A380 jetliner.===Troy Hartman: jetpack and parafoil===In 2008 Troy Hartman started designing a wingless
jetpack with two turbojet motors strapped to his back; later he added a parafoil as
a wing.===Fritz Unger: jetpack with rigid wings
===As at 2013 Fritz Unger in Germany is developing
a jetpack called Skyflash with rigid wings about 3.4 m (11 ft) wingspan and two turbojets
designed to run on diesel fuel. It is designed for takeoff from the ground using four undercarriage
wheels on the front of his chest and abdomen.===JetPack Aviation: Wingless Jetpack===
On 3 November 2015, Jetpack Aviation demonstrated the JB-9 in Upper New York Bay in front of
the Statue of Liberty. The JB-9 carries 4.5 kilograms (10 lb) of kerosene fuel that burns
through two vectored thrust AMT Nike jet engines at a rate of 3.8 litres (1 US gallon) per
minute for up to ten minutes of flying time, depending on pilot weight. Weight of fuel
is a consideration, but it is reported to start with 150 m (500 ft) per minute climb
rate that doubles as the fuel burns off. While this model has been limited to 102 km/h (55
knots), the prototype of the JB-10 is reported to fly at over 200 km/h (110 kn).
This is a true jetpack: a backpack that provides jet-powered flight. Most of the volume is
the fuel tank, with twin turbine jet engines gimbal-mounted on each side. The control system
is identical to the Bell Rocket Belt: tilting the handgrips vectors the thrust – left-right
& forward-back – by moving the engines; twisting left hand moves two nozzle skirts
for yaw; twisting the right hand counterclockwise increases throttle. Jetpack Aviation was started
by Australian businessman David Mayman with the technical knowhow coming from Nelson Tyler,
prolific inventor of helicopter-mounted camera stabilizers and one of the engineers that
worked on the Bell Rocketbelt that was used in the 1984 Olympics.===Flyboard Air===
Flyboard Air, invented by Franky Zapata, allows flight up to 3,000 metres (10,000 ft) and
has a top speed of 150 km/h (93 mph). It also has 10 minutes autonomy.===Daedalus Flight Pack===
See full article Daedalus Flight Pack This particular innovation saw two jets attached
to the back of an exoskeleton, worn by the operator. At the same time, two additional
jets were added to the arms, and could be moved with the arms to control movement. It
was devised by Richard Browning of Gravity Industries.==In space==Rocket packs can be useful for spacewalks.
While near Earth a jet pack has to produce a g-force of at least 1 g (a smaller g-force,
providing only some deviation from free fall is of little use here), for excursions outside
a free falling spaceship, a small g-force providing a small deviation from free fall
is quite useful. Hence much less delta-v is consumed per unit time, and not during the
whole EVA. With only small amounts of thrust needed, safety and temperature are much more
manageable than in the atmosphere in Earth’s gravity field.
Nevertheless, it is currently worn to be used only in case of emergency: the Simplified
Aid For EVA Rescue (SAFER).==Hydrojet packs==The 21st century has seen a new approach to
jet packs where water is used as a high-density propulsion fluid. This requires a very large
mass of fluid that makes a self-contained jetpack infeasible. Instead, this approach
separates the engine, fuel and fluid supply from the pilot’s flying apparatus, using a
long flexible hose to feed the water to the jet nozzle pack attached to the pilot’s body.
These inventions are known as “hydro jet packs”, and successful designs have used jetski technology
as the powerplant operating in a body of water (an ocean, lake, or pool) to provide the needed
propulsion. Several hydro jet pack approaches have been successfully tested and put into
production. Flow rate can be controlled by a throttle operator on the jetski, or by the
pilot using a remote actuator. Another significant difference with hydro
jet packs is that they can be operated below the surface as well as above it. As of 2013,
many hydro jet pack rental businesses are operating in various locations around the
world.===JetLev===The JetLev was the first hydroflight jetpack
on the market, and its makers were awarded the first patents, in 2008, for hydrojetpacks.
The JetLev has the appearance of a typical jet pack, with two nozzles on a backpack propelling
the rider upwards. It just has an umbilicus to the powering jetski that provides the water
for the thrust used.===Flyboard===A Flyboard has water jets under each of the
pilot’s feet. An optional feature is a lower-thrust water jet for each arm for greater control.
The powerplant is a regular jetski. Development for this approach was started in the spring
of 2011.==Home-made versions==
Episode 32 of MythBusters investigates the urban legend of an affordable jet pack or
rocket pack that can be built from plans purchased on the Internet. Extensive modifications were
made by the MythBusters team due to vagueness in the plans and because of the infeasibility
of the specified engine mounting system. The jet pack produced by the MythBusters had two
ducted fans powered by ultralight-type piston engines. (Fans complained that the use of
piston engines destroyed the whole idea of the pack’s being truly based on jets, by which,
presumably, they meant self-contained gas turbines.) They found it was not powerful
enough to lift a person off the ground, and was expensive to build. The plans specified
a Rotax 503 ultralight engine, but they intended to use the more powerful and lighter Rotax
583 engine before a similar lighter unnamed engine was substituted.==In fiction==The concept of jet packs appeared in popular
culture, particularly science fiction, long before the technology became practical. Perhaps
the first appearance was in pulp magazines. The 1896 novel The Country of the Pointed
Firs mentions a “fog-shaped” man hovering low with a “the look of a pack on his back”
who “flittered away out o’ sight like a leaf the wind takes with it”. The 1928 cover of
Amazing Stories featured a man flying with a jet pack.
When Republic Pictures planned to produce a superhero serial using its renowned “flying
man” scenes as used in The Adventures of Captain Marvel, the character of Captain Marvel was
tied up in litigation with the owners of the character of Superman. For its postwar superhero
serial, Republic used a jet pack in King of the Rocket Men. The same stock special effects
were used in other serials. While several science fiction novels from
the 1950s featured jetpacks, it was not until the “Bell Rocket Belt” in the 1960s that the
jet pack caught the imagination of the mainstream. Bell’s demonstration flights in the U.S. and
other countries created significant public enthusiasm.
Jetpacks were featured in two episodes (“Turu the Terrible” and “The Invisible Monster”),
of the original Jonny Quest (1964-1965) animated television series, and are seen at the end
of the closing credits.In 1965 a jetpack appeared in the James Bond movie Thunderball when James
Bond played by Sean Connery used a jet pack in the pre-title sequence to escape the bad
guys and rendezvous with his French contact. The pack was piloted by Gordon Yaeger and
Bill Suitor. In the Irwin Allen television series Lost
in Space (1965-1968), a jetpack was used by members of the Jupiter II expedition on several
occasions. In 1966 the plot of the 21st book in the Rick
Brant series titled Rocket Jumper was based on a hydrogen peroxide fueled jet pack, The
book included a relatively detailed description of the design including use of a platinum-metal
screen catalyst. In the 1997 video game Crash Bandicoot 2:
Cortex Strikes Back, the titular character Crash, operates a jetpack in two main levels,
“Rock It” and “Pack Attack”. He also uses the jetpack in the final boss fight against
Dr. Neo Cortex. The 1976 television series Ark II featured
a jetpack called the Jet Jumper. In the Star Wars original trilogy, the bounty
hunter Boba Fett used a jet pack. In the prequel trilogy, Jango Fett also used a jet pack.
In the 1982-1995 comics book series, The Rocketeer, the protagonist, Cliff Secord, acquires a
stolen military jet pack and uses it to become the eponymous superhero. It was later adapted
into a motion picture in 1991. The 95 mm (3.75-inch) G.I. Joe action figure
launch in 1982 included the JUMP (Jet Mobile Propulsion Unit) jet pack as an accessory.
It was also featured prominently in the related G.I. Joe comic book series and cartoon.
Jetpacks have been used by the title characters in several episodes of SWAT Kats cartoon series
(1993–94).Jetpacks appear in the popular video game Halo: Reach. On September 13, 2010,
during a Halo: Reach launch party at London, England’s Trafalgar Square, stuntman Dan Schlund
of Powerhouse Productions Inc “Rocketman” firm (which provides jet packs for use by
marketing and sporting companies) donned a Halo-esque “Spartan armor” suit and a jet
pack and maintained flight for 30 seconds before landing safely.
The jet-pack also appears in the 2012 video game Halo 4, developed by 343 Industries.
Jetpacks also appeared in other video games, including BloodRayne (worn by Nazi troopers),
Tribes, Giants: Citizen Kabuto, Armed and Dangerous, and the Pilotwings series, in which
it is referred to as a “Rocket Belt”. It is also accessible in the video game Grand Theft
Auto: San Andreas. Fallout 4 also has a jetpack power armor feature. Grand Theft Auto Online
added a jetpack called “Thruster” as an usable vehicle on a content update on December 12,
2017.Many science fiction movies have included jet packs, most notably Minority Report, Sky
Captain and the World of Tomorrow, and Tomorrowland. Running since 2013, Adventures in Jetpacks
is a semi-regularly updated webcomic in which the cast of characters make regular use of
Jet packs.==See also==Backpack helicopter
History of the jet engine Martin Jetpack, despite its name, is a backpack
helicopter. Space Ranger (device) advertised in Popular
Science 1970s Wingsuit flying

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