Brief:
High Altitude Pro is a complete kit for a single stage ring fin water rocket from Anti-Gravity Research. This is one of a several water rockets available at AntiGravity. High Altitude Pro is a very simple, high flying water rocket that should prove to be very safe and easy for children. The rocket derives its impulse from a bicycle pump and a small amount of water in a 2-liter water bottle.

Construction:
The kit comes complete with water bottle, fin assembly, pressure nozzle, launch rod, and launch equipment. The buyer must assemble the kit and provide a source of pressurized air from a bicycle pump.

When I opened the box, I was faced with a bewildering array of blue featherweight, pre-molded Styrofoam pieces which at first glance did not seem to resemble the picture of the complete rocket. On closer inspection after reading the instructions, it became clear that a very clever mind must have devised a mold from which the Styrofoam pieces were made and that these pieces when fitted together and secured with rubber bands would make a water rocket. The kit that I received was complete, well packed, and had a few extra rubber bands in case some of them broke.

The detailed instruction sheet has both text and color diagrams and drawings to demonstrate the step-by-step construction of the rocket. The kit includes 4 sizes of rubber bands and it was clear from the instructions which size was needed at each step. The geometric puzzle of assembling the pieces left me initially perplexed but then everything fell into place. I would recommend to anyone buying the kit to assemble the kit at home one time, then take it apart and reassemble it before launch. It took me about 20 minutes to assemble it the first time and now I can do it in probably less than 5 minutes. The kit is very simple to assemble and all of the pieces fit as shown in the instructions. My 9-year old mastered the construction in half the time that I required.

The rubber bands do not hold the pieces together in a vice-like grip. Instead, the pieces are held together just tight enough to survive takeoff and flight but are meant to collapse to some extent on landing to protect the parts from breaking. A nice feature of the kit is that it can be disassembled and repacked into the same box in which it was shipped. The people at antigravityresearch.com provide a table of reasons why their rockets are constructed in the way that they are and what design goals were achieved by so doing. One important factor is safety. Since the rocket essentially self-destructs and includes a padded bumper on the front, it is unlikely that someone could be seriously injured by one of these rockets even if it struck them full force during lift off.

We have built a variety of homemade water rockets before. The High Altitude Pro was different in the following respects: The fins are pre-cut, fit very well, and are held in place by rubber bands rather than with tape or glue. The bottle uses a bottle cap with a narrow hole in it to create a pressure nozzle. All water rockets that we have launched to date have not used a nozzle other than the fully open bottle end. The nozzle is specifically designed to work with the unique launcher that is supplied with each kit. The launch tube is a very simple plastic hose with a little balloon-like device on the end that fits up inside the nozzle. Air is pumped into the bottle through the balloon which will remain tightly secured in the nozzle so long as one continues to pump. Once the pressure drops on the supply side of the launch tube when you stop pumping, the balloon deflates and falls out of the nozzle, allowing the pressure and water to escape through the nozzle, providing thrust for the rocket. This simple launch system eliminates the primary difficulty of launching most water rockets: the need for a release mechanism (typically operated by a pull cord). The entire launch system with the exception of the air source will fit in your pocket and the nozzle cap could easily be applied to other bottles.

Construction Rating: 4 out of 5

Flight:
The instructions suggest using a small amount of water (120 ml I think) and there is a picture in the instructions showing approximately how full to make the bottle. I also read somewhere (I believe at the antigravityresearch.com website) that a small amount of dish soap in the bottle will cause foaming, slowing the expulsion of the water from the nozzle and thus helping to sustain flight for a longer period of time and achieve a higher altitude.

We loaded up the bottle with water according to instructions and added a drop of liquid dish soap. The kit comes with a wooden dowel for a use as a launch rod. The launch rod provided with the kit is meant to be pushed into the dirt and the rocket slides down on the rod with one of the fin supports acting as a launch lug. I used a metal launch rod from our model rocket launcher instead. I reasoned that this longer rod would keep the rocket going more straight in the intended direction. The rocket slid more smoothly along the metal rod than it did on the wooden dowel that came with the kit.

I pumped the bottle with a standard bicycle pump that has a gauge that registers up to 160psi. The flow of air into the bottle is restricted by the balloon on the end of the launch tube. The balloon allows the air to slowly enter the bottle no matter how much pressure the pump exerts. It is thus not necessary to frantically pump. A good steady pumping action is sufficient and the bottle never released prematurely from the tube. The pressure gauge periodically registered 100 psi but then fell to about 70 psi as the air passed through the balloon into the bottle. I never could determine precisely the pressure in the bottle, which is different from the way in which we have filled bottle rockets with other launch systems in the past.

After a couple of minutes of steady pumping, there was a steady but small leak of water past the balloon on the end of the launch hose. Eventually I decided to stop pumping. The tube soon slipped out of the nozzle and the rocket shot off the launch rod spewing sudsy water. The flight was straight and the rocket did not wobble but it probably only went 50 to 60 feet in the air. Subsequent launches provided a bit more altitude but all in all the performance of the rocket was not as exciting as we had hoped. It seems to make little difference in flight performance if I do the pumping or if my kids do it. I believe that the metal launch rod does not detract from the performance and if anything helps keeps the rocket going straight up. We attempted one launch without the launch rod and the rocket tipped over just as the hose released causing the rocket to shoot sideways and bounce across the field. I cannot tell if the soap suds improve performance, since flights with plain water appear to go to about the same altitude. When using the balloon tube launch system, it is difficult to judge when to stop pumping so under-pressurization of the bottle might be the root cause of lackluster performance. I suspect that we could achieve better performance if we used an air compressor and filled for a longer period of time.

Flight Rating: 3 out of 5

Summary:
The High Altitude Pro is a simple, sturdy water rocket that should be safe for kids of all ages. It uses tumble (or more like ballistic) recovery and has a bumper on the front to help in preventing damage or injuries from a falling rocket. The fin assembly partially collapses upon landing, protecting the components but requiring reassembly between launches. The pre-molded Styrofoam ring fin and the launch system are ingenious and merit the purchase of this kit.

Overall Rating: 4 out of 5