John Smith wrote:

I did not personally hear anyone booing, but I will tell you that it was
a very disappointing performance.
It was a very over hyped event. The name "jetpack" is a gross misnomer.
It is two ducted fans, similar to a project and device that flew in the
US several years ago. It was funded with DARPA money. The prototype was
offered for sale after the initial test flights. Wish I could recall the
name.
It reminds me of the old days of Oshkosh with its unproven performance
statistics, high price, and ambitious but speculative claims.

I am trying to understand how the engine they have developed will
produce the claimed 200 HP.

MythBusters built a similar device last year and failed to achieve the
lift necessary for flight with off the shelf components.

The machine(s) you're thinking of that DARPA funded were Trek Aerospace's
SoloTrek and Springtail. Those machines did fly (see video on their
website, www.trekaerospace.com), but funding dried up once they achieved
DARPA's goals.

The MythBusters machine was built loosely to plans purchased through Popular
Science or Mechanics Illustrated. Unfortunately, the seller of those plans
only ripped off Trek's concept and had not a clue to what was needed to
actually get airborn, let alone to achieve stability.

The stability issue will also plague Martin's Jetpack. All hovering
aircraft are unstable. The lower the moment of inertia (mass), the quicker
the machine can get into trouble. These personal hovercraft are very
light! And very unstable. The Hiller Flying Platform had mechanical gyros
to help stabilize it. The Trek machines had on onboard computer with
electronic gyros (a few steps up from that used on the Segway and RC
helicopters). If Martin's Jetpack doesn't have anything like that, it will
in the near future.

The deadman's zone will be a real problem. With no forward flight speed a
standard BRS parachute can save you from 75'. The chutes that "pop" open
should be ok from 40-50'. The aircraft structure should save you below
5-10'. Unfortunately, the deadman's zone, 10-40' high, is just where the
military wants to use these machines; and just where they'd be the most fun
to fly, darting between trees. Trek was looking at a twin-engined version.
With one engine out you couldn't maintain level flight, but you could
descend under control.

What Mr. Martin has achieved, on a shoestring budget, is very impressive.
He's still got a long way to go before he has anything practical. The fact
that he's taking deposits is the truely sad part.