From: Jordin Kare <jtk@s1.gov>
Newsgroups: sci.space.tech
Subject: Re: Jetpack
Date: 30 Jul 1996 22:54:38 GMT

In article <4tla1l$e5i@info4.rus.uni-stuttgart.de> Sonja Schubert,
lrt10867@rpool3.rus.uni-stuttgart.de writes:
>Does anyone know something about jetpacks ???
>I only know that one was flying during the opening ceremonies at
>the Olympic Games in LA.
>What kind of fuel was used and how long was this thing able to fly ?

Jetpacks use hydrogen peroxide monopropellant, normally 70% to 85%
concentration, with silver-mesh catalyst to decompose the 
peroxide. These things have flight durations in the 
range of 30 - 45 seconds. The same technology is used in "rocket powered"
stunt racecars.  

>And has anyone developed this technology any further ?

I do recall a magazine article about this in the last year, possibly in
the rather nice magazine "Invention and Technology" which crosses
my desk occasionally.  

The jetpack business has been essentially a one-man effort since
its inception post-WWII, although the one man has changed a few
times.  If I recall, there have been 3 or 4 versions of the jetpack, 
none produced in any quantity.  The military was briefly interested,
but the short flight time and range, plus the fact that a flying
soldier is *such* a tempting target, made them give it up.

In principle, the flight time could be extended to about 2 minutes
by using bipropellant (300 seconds Isp vs. ~100 seconds Isp) such 
as kerosene and peroxide, but the exhaust would be much hotter
and the risks associated with accidents increased.  The flight time 
could be raised even farther if a true air-breathing jet, rather
than a rocket, were used, but the cost would be much higher and
there might be serious controllability problems (turbojets aren't 
noted for quick throttle response...).  If you're going that far, you
can do better still by using a large-diameter propeller, and adding
a frame with landing gear -- and you've reinvented the small helicopter...

From: higgins@fnald.fnal.gov (Bill Higgins-- Beam Jockey)
Newsgroups: sci.space.tech
Subject: Jetpacks, belts, and personal rockets (was Re: Jetpack)
Date: 31 Jul 96 11:28:09 -0600

In article <4tm3rf$ct3@lll-winken.llnl.gov>, Jordin Kare <jtk@s1.gov> writes:
> In article <4tla1l$e5i@info4.rus.uni-stuttgart.de> Sonja Schubert,
> lrt10867@rpool3.rus.uni-stuttgart.de writes:
>>Does anyone know something about jetpacks ???
> Jetpacks use hydrogen peroxide monopropellant, normally 70% to 85%
> concentration, with silver-mesh catalyst to decompose the 
> peroxide. These things have flight durations in the 
> range of 30 - 45 seconds. The same technology is used in "rocket powered"
> stunt racecars.  

Jordin goes on to provide more useful information. I've got my own two
cents on a disk around here...

This is a perennial, if not frequent, topic. I'll excerpt a 1992
posting I made which summarizes everything I know about "jetpacks."

===================
Jo Baute (jbaute@vnet3.vub.ac.be) writes:

>I've got a question about the Jetpacks, like the one they showed
>during the 1984 Olympics in LA.

I know a lot about this. Jetpacks were something I studied when
preparing my slide lecture on flying cars ("Doorman, Call Me an
Aircar!") a number of years ago.

First, references.  Look at *The History of Rocket Technology; Essays
on Research, Development, and Utility*, edited by Eugene M. Emme,
Wayne State University Press, 1964.  There's an excellent essay in
there, "The Man-Rocket" by Robert D. Roach, Jr.  It covers the origins
and history of the Bell Rocket Belt.  Yes, it really was inspired by
Buck Rogers.

More recently, there was an article in *Air and Space* in June/July
1987, "Leapin' Rockets!" by Tom Huntington, which covered the Bell
story and also told a lot about Nelson Tyler, a California camera
specialist who built a copy of the BRB.  Just a few months ago, *Final
Frontier* had a first-person article by the guy who first flew the
BRB, Harold Graham. (*He* mentions Commando Cody movies...)  I thought
I had the issue here in my briefcase, but it doesn't seem to be
present.  It's the one with the International Space Year as the cover
story.

>How do those pilots keep level instead of tumbling forward ?

The Bell Rocket Belt was the brainchild of an engineer named Wendell
Moore.  The question of stability was hotly debated around the Bell
Aircraft coffeepot.  In 1958 Moore constructed a test rig where
nitrogen gas was fed through a hose to nozzles at approximately
shoulder height, looking something like this:

     pilot

     ||||
      oo
     (__)
   // >< \\
  //      \\ <--nozzles
  ^        ^
     ====
     |  |
     |  |
     [][] <--- Landing gear
               (size 11E oxfords)

The operator was tethered for safety. Roach tells us that engineers
who thought the rocket pack would be unstable oscillated, and
optimistic engineers found no difficulty in controlling the rig.
Makes a good folk tale, anyway.

Bell got an Army contract to develop the real thing, a 125-pound
device powered by a throttleable rocket motor.  The motor burned
hydrogen peroxide monopropellant and gave up to 280 pounds of thrust.
First untethered flight was 20 April 1961.  Endurance was very
limited-- 21 seconds of flight-- and, as any computer nerd who's
played "Lunar Lander" knows, you'd better reserve enough propellant to
get you back down gently.

Hey, look, here's the spec sheet.  I haven't looked at this file in a
while.

Propellant weight    47 lb
Empty weight         83 lb
Throttleable thrust  0-300 lb   (your pilot better not weigh over 188!)
Max range            866 ft
Altitude             80+ ft
Maximum speed        60+ mph
Reliablility:        100% in more than 3000 flights

Development continued through the Sixties on rocket chairs and rocket
pogo sticks in attempts to increase endurance and utility.  The
original Belt was used as a PR device and lent its glamor to all sorts
of movies, TV shows, and commercials.

As jsloan@ncar.ucar.edu (John Sloan) writes,

>Baby boomers will recall seeing this model used in the TV Series _Lost
>in Space_ and in one of the early James Bond movies (_Thunderball_ I
>think) with Sean Connery.

Mark Brown (mbrown@convex.com) also mentioned Colonel Keds (Keds
were sneakers, in the days before "running shoes.") commercials.  The
Man from Glad (plastic bags) had a crack at the BRB, too.

Dave Barton (dlb@hudson.wash.inmet.com) also brought up

>the WASP (Williams Aerial Survey Platform) which had a jet engine on
>the bottom; the single occupant essentially stood on the fuel tank.

Williams International, in Walled Lake, Michigan, makes little fanjet
engines for cruise missiles, which were ideal for one-man jet belts.
Bell worked with them on a jet belt with 7-minute endurance, which
first flew on 7 April 1969.

Later Williams developed the WASP, later renamed the "X-JET" for some
reason, which looked like a pilot standing in a garbage can.  The
600-pound turbofan was mounted in front of the pilot, and the WASP
could stay airborne for 30 minutes, reach speeds of 60 mph, and land
in a four-square-foot area.  This is from the info Williams sent me in
1987... I don't know where the project stands today.  It was a
contract with the Army Tank Automotive Command.

-- 
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