Bubblecam started out as an experiment. After having already constructed a number of rockets - several Estes kits and some home-made designs - the challenge of Bubblecam was to devise a rocket which not only was built from mainly generic household items but would perform an interesting function: taking photographs.
Of course this idea was not new - aerial photography has been achieved through model rocketry on many occasions. But my aim was to fit a standard disposable 35mm camera into a relatively small rocket using very few specialised parts. In fact the only proprietary items which ended up being used in Bubblecam were a tube coupler, two engine hooks and a short section of tubing to hold the engine.
(At this point, a note for readers - particularly those outside Australia. Model rocketry is not widely known in Australia and relatively few hobby stores sell it. These shops usually stock Estes and Quest starter sets, packaged kits and general supplies such as engines and recovery wadding, but other items such as body tubes and nose-cones are only available on special order. The biggest engine available for legal purchase without club membership is the "D" size, which places obvious limits on the types of rockets which can be built and flown. Also at the time of writing there is very limited availability of photographic film in 110 or 126 cartridge type, which largely precludes the use of special-purpose cameras. Estes' Astrocam, for instance, is no longer generally sold in this country.)
So Bubblecam evolved without any detailed plans or known benchmarks, just a few general design parameters which were adapted to fit the materials available. (Okay, in other words I was determined to do it the hard way!) The first decision was where to place the camera. Could it be placed in the middle of the rocket, aiming sideways? Or at the base of the rocket so that a ground shot could be taken? Perhaps two cameras might be used, one at each side to balance the weight? Eventually I decided to situate the camera in an enlarged nose-cone section, for reasons of simplicity and optimum weight distribution. It would be mounted with the lens facing sideways, thereby yielding a view of the horizon (hopefully) rather than a shot towards the ground. A mirror might be added later to achieve a ground shot.
Next: how would the camera be activated? A number of designs were contemplated before the mechanism was made, but the one which was used consisted of a balsawood camera "cradle" and an engine mount angled so that the end pressed against the shutter button. A plastic tab was fashioned to slide between the engine mount and the button. It was then attached to a length of fishing line and the line was hooked onto the rocket body before launch; when the ejection charge fired the nosecone would lift away from the main body, the plastic tab would be pulled from the nosecone through a small tube and the engine mount would then press the camera's shutter button. Once again simplicity was the main consideration, as well as the need to keep the weight down as much as possible.
At this stage I really wasn't sure whether this rocket would perform as I intended. It looked like it might have too much weight, and the survival of the camera was in doubt. Altitude could only be roughly estimated with the "D" engine being smaller than desirable for the rocket's size. But I decided to go ahead and make it anyway! Sometimes other people's skepticism works as an added motivational factor, just for the satisfaction of proving them wrong.
Having proceeded thus far it was time to make the main rocket sections. The propulsion section was constructed from a thick cardboard tube out of a roll of cling film, with custom-designed balsawood fins and layers of cut-down tubing to centre the engine mount. The centre section comprised a short section of the same tube grafted onto the plastic end of a mailing tube. A tube coupler was used externally to slide over the main body tube, small fins were attached and a cut-down plastic kitchen funnel provided a transition between the two different-diameter sections. Finally a piece of the mailing tube, plugged with balsa at the top and with another kitchen funnel attached, formed the nosecone where the camera would be housed. The camera cradle was designed to slide snugly into this section.
Bubblecam was then painted with white spray enamel, and a few decals were applied. Parachutes were cut from plastic sheets and attached in the usual manner via shock cords to each section.
BUBBLECAM SPECIFICATIONS Length 690mm (approx. 27") Motor section diameter 37mm Camera section diameter 74mm Weight (with camera) 327g (approx. 11.5oz) Recovery Twin parachutes Fins Balsa Approximate max. alt. 100m Engine D12-3 (see text)
So what of the launches? The first launch was a great success and the picture was taken exactly as planned. It turned out a little blurred but you get the idea. The second launch, however, didn't go very well - Bubblecam didn't reach as high an altitude and the ejection charge delay was a bit longer and... well, the parachutes didn't deploy until the rocket had already impacted with the ground. It still took the picture though! The impact even caused the camera to partially break open which might explain the weird banding effect on this exposure. Of course the rocket was extensively damaged (think of simply throwing it at the ground, hard, and you can imagine what happened).
The rebuilding of Bubblecam did not turn out entirely as expected - a subsequent launch proved that the rocket had become slightly lopsided or warped, and it arced over somewhat during flight. However this led to a different style of image being produced; two launches in particular yielded good-quality photographs which I have put together here.
More by accident than by design, the rocket reached very similar heights on both launches (evident as the size of the basketball court is nearly the same in the two images) and took both shots facing roughly the same direction. The plume of smoke from one launch is clearly visible at the lower right-hand end of the basketball court, and the nearby experimenters can also be seen in the photograph.
On the second launch the nosecone section's parachute only partially opened and the impact with the ground was quite hard. However the camera survived without any damage and was later used to take another 25 images in a more conventional manner.
Naturally there have been many other, more sophisticated implementations of photography from scale rockets. Bubblecam is kind of unusual since it uses both a normal single-use camera and a purely mechanical shutter-actuating system. Also it ended up using mainly parts which were not rocket-specific and a "home-brew" type of design. If nothing else, it has been an interesting (and occasionally frustrating) experiment. The main problem evident with this rocket is that the D-series motor is not quite powerful enough to ensure sufficient altitude every time. Estes does specify weight limits for various motors, and Bubblecam's lack of altitude illustrates the very good reason for that. Using low-power rocketry to send a regular-sized camera skywards is a bit of a challenge to say the least.
A more recent series of launches had varying degrees of success but unfortunately did not produce any usable images. Of course the orientation and velocity of this rocket's camera section upon ejection cannot be controlled or even readily predicted. An examination of the last series of negatives suggested that the camera was either pointed skywards or moving too rapidly to take any recognisable images. This resulted from four launches on different days, so I thought it was quite bizarre that none of the shots turned out. (The camera was working fine since I used it for other photos between launches.) Go figure!
The next rocket in the series will be Bubblecam II (or Bubblecam Lite if you like - the design is lighter and more streamlined). It will transport a slimline single-use APS camera, so the nosecone can be made smaller in diameter. The general design of the new rocket will be similar to the current Bubblecam and it will use the same D12-3 motors. I am also planning to try out cloth parachutes on this latest unit.
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