BUILD
NOTES
Within its steel frame and aluminum skin, our
15-foot backyard rocket encompasses microcontrollers and LEDs, pneumatics, vibration
and sound effects, and the joy of making.
Rocket-Ship
Treehouse
BY JON HOWELL AND JEREMY ELSON
■ RARELY DOES BUILDING A TREEHOUSE
require welding, grinding, painting, riveting,
bending, crimping, plumbing, brazing, laser
cutting, sound design, printed circuit board
fabrication, distributed network protocols,
an embedded operating system, sewing, and
even embroidery. Ours did: a backyard rocket-ship treehouse.
An Engineering Playground
The Ravenna Ultra-Low-Altitude Vehicle
(RULAV), named for our neighborhood in
Seattle, Wash., is a hexagonal capsule 7½ feet
high, atop a tripod of the same height, for an
overall height of about 15 feet. The frame is
welded mild steel with riveted aluminum skin
and a hinged entry panel and window. A ladder made of steel cable runs from the ground
to the rocket’s floor. A rigid interior ladder
lets kids climb up and peek out the top.
“It’s for Jon’s son, Eliot,” was our justification
to friends and co-workers after describing the
growing list of planned features. As our ambitions spiraled and months of construction
stretched into 2 years, it became transparent
that the treehouse was just as much an engineering playground for the adults, a place
for us to share our joy of making and teach it
to the kids. Now that the rocket is complete,
it’s a fun plaything, but the journey was even
more rewarding than the result.
The rocket was conceived in 2008 after
Inside the rocket are nearly 800 LEDs
forming dozens of flashing numeric displays
spread across 14 control panels, each with an
acrylic face laser-cut and etched with labels
such as “Lunar Distance” and “Hydraulic
Pressure.” Working buttons, knobs, and
switches operate the rocket’s software.
Eliot’s mom suggested that Jon install a swing
set under the trees in the backyard.
“A swing set? Everybody has a swing set.”
Mom said, “Then what are you going to
build? A rocket?!”
“Yes. Yes we are. That is exactly what we’re
going to build.”
Underneath the capsule are 3 “thrusters”
that shoot plumes of water and compressed
air under the control of a pilot’s joystick,
simulating real positioning thrusters. Takeoff
and docking sequences are augmented by
a pneumatic paint shaker that simulates the
vibration of a rocket engine (Figures A and B,
page 146).
Sound effects complete the illusion, with
Jeremy Elson and Jon Howell
a powered subwoofer that gives the rocket
a satisfying rumble.
Chassis and Skin
We went to Boeing Surplus and brought home
a few big aluminum sheets and some sturdy
aluminum tube. Our first idea was to build a
geodesic structure formed entirely by bending and riveting, but early prototypes wouldn’t
stand up, proving that we really didn’t know
much about mechanical engineering.
Finally, we realized weight wasn’t a design
144 Make: makezine.com/31
