Saturday, August 22, 2009

Project 3000 Update: 08-22-2009

It has been another amazingly productive week here at U.S. Water Rockets. We've made a major advance in our nozzle design which has been tested on the bench and proved to be the solution to a major impediment to our world record flights. The issue is an effect we have dubbed "Blowback".

The way we discovered this issue is thanks in part to a question posited by our new friend Steve Porter, who frequents the WRA2 Water Rocket Forum, and noticed something odd in our HD Video from Video Log #1.

Steve noticed that when the rocket was coming down from apogee, the view in the camera lens became blurred and distorted. We had noticed this ourselves back at the time of the launch and we had attributed the effect to fogging of the camera lens. We believed that the heat from the camera and the cold air had somehow condensed moisture and fogged the lens. Since the rocket took a long time to retrieve from the tree it landed in, there was no fog on the lens when we recovered it, so we had no proof. You can see how blurred the HD video image became near the end of the descent in the image below.
We were discussing the theory with Steve and he suggested an alternative idea that never occurred to us. His suggestion was that water dripping from the nozzle would have been blown along the outer skin of the rocket as it fell rapidly thanks to the partially failed parachute. The water drips eventually were blown back up to the nose of the rocket where they collected on the rear-view mirror we placed there. The drops of water eventually collected there and blurred the lens.

We consulted some of our more recent videos and noticed that there indeed was a good deal of water streaming from the nozzle after apogee. The water would drip off and fly down below the rocket. The water could easily be seen spraying around the downward looking views in the HD video. Fortunately, we had a recent launch which had a partially tangled parachute resulting in another rapid descent and just before splashdown we did notice a slight amount of fogging in the video. We believe that this confirms Steve's brilliant observation regarding the water.

We went back and looked at some of our other recent flights and we realized that there was a lot of water dripping from the nozzle during the descent phase. Notice how many water droplets are visible in this recent still-frame shown below.
That was not the end of our story, however... we discussed the dripping water and as you would expect we concluded that it would not be a problem for video in normal flights. We did decide that the amount of leftover water inside the rocket was excessive. It amounts to useless dead weight that needs to be carried to apogee, and it also equates to a loss of thrust that could have been used to lift the rocket.

We ran some static tests and realized that the blowback effect is caused when the water level becomes shallow enough for the air pressure to "punch" through the water, forming an air column through the water and actually splashing the water upwards above the air pulse and all over the inside of the rocket, where it would slowly run down and out long after the rocket had reached apogee.

We have made some changes to our nozzle inlet and added an inverted cone shaped baffle to the rocket just above the nozzle, and we have reduced the amount of blowback by 2/3 what it was. We were able to test this in the lab by weighing the rocket before test firing and then weighing it after test firing and subtracting the mass of the dry rocket to determine the weight of the water remaining. Subsequent test flights have much less water droplets visible, so we are confident we have solved the problem. See the improvement in the image below?
We will be using the new nozzle design in our next round of test launches. A report on the new nozzle performance will be forthcoming. Once again a big thanks to Steve for his insightful observations!

See you next time!

Saturday, August 15, 2009

Water Rocket Launcher Construction Tutorial: Part 13

It has been another long and productive week here at U.S. Water Rockets. We have been working very hard trying to solve a few problems with our Project 3000 design and have made some excellent progress. We will not know for sure if our situation has been corrected completely until our next launch day, which may be this weekend if the weather forecast holds true.

You can expect full details of our progress in an upcoming installment of our video log series, as we have taken a great deal of imagery and video footage of the progress as we move along.

Meanwhile, we are continuing to refine our launcher tutorial and this week we will be picking up where we left off in our last part of this series where we had just completely painted the wooden parts of the launcher with a product called "Aero Gloss", which is a wood sealer made for modeling applications. This stuff is awesome because it seals wooden pieces and prevents the grain from absorbing paint. The end result is a perfectly smooth finish.
 Even if you are not building a launcher like this one, you will be able to make great use of this product because it can be used on any wooden part of your rocket and will allow you to make it perfectly smooth and really look great with the methods we explain here. For example, we use this product also on our wooden nosecones and rocket fins, for really nice and perfect looking pieces.
When we left off, we had painted the first coat of Aero Gloss on the launcher base, and we allowed it time to completely dry. According to the instructions, you should now sand the wood with fine grit sandpaper and smooth out the wood before the next step. We took progressive gains of sandpaper from 220 to 600 grit and sanded the base. When we were done we use  a towel to wipe off the dust and then compressed air to blow off any remaining particles. We don't want dust to get trapped in our finish, so removing it is a good idea.
A second coat of Aero Gloss was applied to the base at this point. Things went pretty much the same way as they did with the first coat. We found that a good idea is to hang the pieces with a screw temporarily inserted into the hole made for the rubber foot is a nice way to suspend the part so that it can be painted with aero gloss in one coat all over instead of painting one side at a time. The screw in the foot hole can be used to hang the part from a string so that it does not touch anything and ruin the paint.
We actually took the precaution of doing a third coat of Aero Gloss sealer with rounds of sanding and cleaning in between the coats and following the last one, just to be on the safe side. Since this launcher is featured as the sample on our website, we figured we had better be 100% positive that the launcher was as defect free as humanly possible, so we went ahead and did the extra steps. It only added an extra day on the build because we allowed for the final coat of Aero Gloss to dry between the coats and the extra sanding certainly can only make things smoother. While drying out the launcher base, we were able to go to Wal*Mart and pick out a nice bright yellow color for the base color. We thought that the color would look good when combined with the other colors we have planned and would be bright enough to act as a safety precaution as well. We even got "FREE 33% More" paint!
We hung the base up by the screw once more and began applying coats of the yellow paint. Avoid the temptation to douse the whole object with paint because the technique of using many thin coats will produce a much nicer result. It will take longer, but it insures that the paint never becomes too thick to cure properly in the time allotted in the instructions. It also helps produce an even coat without any runs or drips.

We had a small problem in that a little flying insect decided to land on the fresh paint and walk around before being overcome by the fumes but not before leaving footprints as well as his feet, legs, and body stuck in the paint. Having done several thin coats at that time we were able to sand off his handiwork (or footiwork) without cutting through the paint and add another coat on top. The damage is completely fixed now. So remember the benefits of many light coats!
One final thing we discovered was that spray painting the hanging base was not as easy as brush painting it. The spray causes the base to begin to spin around due to the pressure of the paint hitting it. We came up with another idea, going back to painting the bottom side first and then inserting four screws into the leg holes and flipping the base over and standing it on the screws so no paint touched anything, then painting the top side. This worked very well, and we found that painting the base while sitting horizontal was easier to do and that gravity assistance helped get the paint layers on easier. We will remember this in the future.

We are letting the paint cure fully for a few days so we will be back collecting data for Project 3000 in the nice weather. This will give us some more multimedia for our future videos and make sure this paint is not going to be tacky when we go to finish the base build next week.

Thanks again for joining us. See you next time!

Saturday, August 8, 2009

Project 3000 Video Log #1

We've been very busy the past few weeks with more tutorials, but we decided to take a little time during a rainy period to put together the first episode of our Project 3000 Video Log Series. This series began at the end of the Summer of 2008 when we first started working on the new designs for the new rocket.

The design was built around the idea of lifting a fairly hefty payload inexpensively to high altitudes while recording video and logging payload data. The requirements for the payload required us to use a larger tube for the payload section, so we decided to use ordinary soda bottles for the new rocket. A side benefit of using ordinary soda bottles was that it would eliminate criticisms that our FTC rockets had advantages over "pop bottle" rockets.

Prior to the inception of the project, we had been experimenting around with a new camera design based on the controller which will be showing up in the next generation of a famous mobile device. This design is much more advanced than our last one and has programmable resolution and bit rate. The appeal of the new design is that we can take video in any resolution including Full 1080p HD video.

The first Video Log describes the origin of Project 3000, and shows off our very first test flight. This flight was launched in December of 2008 on the day after Christmas. We gained a lot of experience with cold weather launching and the new HD onboard video showed us some issues with the design that we want to investigate.

We took the footage filmed that day and over the past few months and we put together the Video Log series. We hope you enjoy these videos and will subscribe to our channel and of course leave comments!

Enjoy the video!!!!

Tuesday, August 4, 2009

Video Log #1 Coming Soon!

Hello again! This is just a quick post to let you all know that we are hard at work producing our first Vlog post for a new project. We will be posting the first installment of the Project 3000 Video Log in a few days!

See you then!