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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... |
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