The on-board video also turned out great.
The full details of the launch day with lots of pictures and video of the highlights is available here:
http://www.AirCommandRockets.com/day55.htm
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Tuesday, February 26, 2008
Polaron IV Boosted flights
We had a great weekend of flying the Polaron IV rocket with the drop away boosters. The boosters behaved exactly as expected and gave the rocket a nice kick on launch.
The on-board video also turned out great.
The full details of the launch day with lots of pictures and video of the highlights is available here:
http://www.AirCommandRockets.com/day55.htm
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The on-board video also turned out great.
The full details of the launch day with lots of pictures and video of the highlights is available here:
http://www.AirCommandRockets.com/day55.htm
__________________________________________
Friday, February 22, 2008
Successful Booster Test Flights
In preparation for launching Polaron IV we wanted to make sure that the whole launcher will work with the boosters and the main stage all together. We weren't sure if it would come off the launcher cleanly, or if the boosters would fall off, or how the new guide rail would go.
We built a dummy main stage out of old bottles and an old nose cone that used the nosecone-off-at-apogee technique for deploying a parachute. The main stage only had the bottom 2 L bottle pressurised. And had 1.5L of water in it so virtually no air. We added a little ballast into the nose in the form of a zip-lock bag with water in it.
We had two successful vertical take-offs with the boosters all falling off almost simultaneously on both occasions. The boosters were filled with 1L of water and everything was launched at 100psi.
The dummy main stage weighing in at close to 800 grams was still able to reach ~80-90 meters
The parachute opened on the first flight right at apogee, and failed to open on the second flight.
The dummy main stage was destroyed, but luckily all the bits we needed for the Polaron IV rocket survived. The boosters also survived their tumble recoveries.
We proved to ourselves that this particular launcher and booster concept works, and so we are hoping to get at least one flight out of the Polaron IV rocket on Saturday. There are always things that can go wrong on the day, but we will worry about those when they happen.
We have also finished repairing the Hyperon and J4 rockets, so we will have those as backups on Saturday as well.
Full details of the days events with videos of this booster test will be again published on our main site after the launch day.
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We built a dummy main stage out of old bottles and an old nose cone that used the nosecone-off-at-apogee technique for deploying a parachute. The main stage only had the bottom 2 L bottle pressurised. And had 1.5L of water in it so virtually no air. We added a little ballast into the nose in the form of a zip-lock bag with water in it.
We had two successful vertical take-offs with the boosters all falling off almost simultaneously on both occasions. The boosters were filled with 1L of water and everything was launched at 100psi.
The dummy main stage weighing in at close to 800 grams was still able to reach ~80-90 meters
The parachute opened on the first flight right at apogee, and failed to open on the second flight.
The dummy main stage was destroyed, but luckily all the bits we needed for the Polaron IV rocket survived. The boosters also survived their tumble recoveries.
We proved to ourselves that this particular launcher and booster concept works, and so we are hoping to get at least one flight out of the Polaron IV rocket on Saturday. There are always things that can go wrong on the day, but we will worry about those when they happen.
We have also finished repairing the Hyperon and J4 rockets, so we will have those as backups on Saturday as well.
Full details of the days events with videos of this booster test will be again published on our main site after the launch day.
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Sunday, February 17, 2008
Launcher Completed
We spent most of the day in the workshop again today. We are really pushing hard to get Polaron IV and its launcher ready for the next NSWRA launch day. It is only 6 days away.
We did finish the launcher today, which I am really happy about. It now sports a single 2m launch rail. The rocket will use launch lugs to hold onto the rail. We had to switch to this system since there really isn't room for the 3 guide rails we have been using. We ended up using 2 of the feet and guide rails from our medium launcher to support the new launch rail which really reduced the amount of stuff we had to make. The legs are still usable on the other launcher so the nice part is we have less hardware to carry with us when we take both launchers.
We are now finishing off the rocket and the booster retaining mechanisms on the rocket, and then it should be ready to fly. If there is a nice launch opportunity between now and Saturday we may try the boosters with the dummy main stage at our local park.
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We did finish the launcher today, which I am really happy about. It now sports a single 2m launch rail. The rocket will use launch lugs to hold onto the rail. We had to switch to this system since there really isn't room for the 3 guide rails we have been using. We ended up using 2 of the feet and guide rails from our medium launcher to support the new launch rail which really reduced the amount of stuff we had to make. The legs are still usable on the other launcher so the nice part is we have less hardware to carry with us when we take both launchers.We are now finishing off the rocket and the booster retaining mechanisms on the rocket, and then it should be ready to fly. If there is a nice launch opportunity between now and Saturday we may try the boosters with the dummy main stage at our local park.
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Monday, February 11, 2008
Splicing Bottles and Pressure Tests
The weather hasn't been too co-operative this weekend so we spent quite a bit of time in the workshop. We have updated our main site with the latest developments here:
http://www.AirCommandRockets.com/day54.htm
The update includes a video tutorial into how we splice our bottles. It also includes an update on the progress of our Polaron IV rocket, and the Acceleron IIIb booster.
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http://www.AirCommandRockets.com/day54.htm
The update includes a video tutorial into how we splice our bottles. It also includes an update on the progress of our Polaron IV rocket, and the Acceleron IIIb booster.
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Wednesday, February 06, 2008
Glueing and PCB layout
Splicing and Couplings
This week it's been a bit of a mixed bag. Now that we have the PL Premium glue, we are gluing together pairs of 1.25L bottles. These glued sections have a thread at either end allowing us to join them to other sections. We have 6 made up, and two more will get made today. They will be used in constructing boosters and rockets bodies as well.
To join these together we have also been experimenting with making simple "Tornado" couplings. We are still waiting for the glue to dry before we do a full pressure test. We've made up four of these so far and if they work well, we have the materials to make a lot more. They weigh around 7 grams. The other nice thing about these couplings is that they have a 19mm hole which is about 6 times bigger in cross sectional area than the Robinson couplings we have been making. This leads to better internal efficiencies and also means we can put a long 19mm launch tube through them.
The simulator predicts well improved altitudes for rockets made out of the spliced pairs and the tornado couplings.
Repairs
We have also been doing repairs to the two crashed rockets from last week. This will require a little more work since the nosecones and deployment systems need to be rebuilt.
PCB Layout for Flight Computer V1.5
As a part of making life easier when doing repairs we have been finalising the PCB layouts for the next iteration of the flight computer. We are going to do a small run of these PCBs and make up a number of the computers so that we can quickly replace them should they become damaged. The board will be about 43mm x 55mm in size or about 30% smaller than what we have been making on the prototype board. It will have dual servo motor outputs making it suitable for single and dual stage rockets. It also has a buzzer for audio feedback of mode changes as well as helping to locate it in tall grass.
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This week it's been a bit of a mixed bag. Now that we have the PL Premium glue, we are gluing together pairs of 1.25L bottles. These glued sections have a thread at either end allowing us to join them to other sections. We have 6 made up, and two more will get made today. They will be used in constructing boosters and rockets bodies as well.
To join these together we have also been experimenting with making simple "Tornado" couplings. We are still waiting for the glue to dry before we do a full pressure test. We've made up four of these so far and if they work well, we have the materials to make a lot more. They weigh around 7 grams. The other nice thing about these couplings is that they have a 19mm hole which is about 6 times bigger in cross sectional area than the Robinson couplings we have been making. This leads to better internal efficiencies and also means we can put a long 19mm launch tube through them.
The simulator predicts well improved altitudes for rockets made out of the spliced pairs and the tornado couplings.
Repairs
We have also been doing repairs to the two crashed rockets from last week. This will require a little more work since the nosecones and deployment systems need to be rebuilt.
PCB Layout for Flight Computer V1.5
As a part of making life easier when doing repairs we have been finalising the PCB layouts for the next iteration of the flight computer. We are going to do a small run of these PCBs and make up a number of the computers so that we can quickly replace them should they become damaged. The board will be about 43mm x 55mm in size or about 30% smaller than what we have been making on the prototype board. It will have dual servo motor outputs making it suitable for single and dual stage rockets. It also has a buzzer for audio feedback of mode changes as well as helping to locate it in tall grass.
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Thursday, January 31, 2008
Launcher Pressure Test
In the last few days we've pressure tested the Polaron IV launcher to make sure there are no leaks. There are a lot of connections and we were not sure how well the seals would seal around the plastic compression seals around some of the copper manifold pipes.
All was good and we took the pressure up to 215 psi ( ~15 bar ) for both the main stage line and the booster manifold.
When pressurising, we really have to think about what valves get open or closed and in what order.
For the first launch the pressures will be in the order 110 - 130psi.
We made dummy plugs for the booster nozzle seats for the test. This allowed us to test that side of things without having to put the boosters on the launcher. We fitted a strapping tape reinforced small 300ml coke bottle to the main stage release head and used the 7mm aluminium nozzle that the main stage will use. All held up well, and we tested the bleed valves
for both the main stage and the boosters with success.
We are now working on the booster retention mechanisms and getting those attached to the boosters and main stage.
The update from last Saturday's launch event is also now available on the main site:
http://www.AirCommandRockets.com/day53.htm
___________________________________________________
All was good and we took the pressure up to 215 psi ( ~15 bar ) for both the main stage line and the booster manifold.
When pressurising, we really have to think about what valves get open or closed and in what order.
For the first launch the pressures will be in the order 110 - 130psi.
We made dummy plugs for the booster nozzle seats for the test. This allowed us to test that side of things without having to put the boosters on the launcher. We fitted a strapping tape reinforced small 300ml coke bottle to the main stage release head and used the 7mm aluminium nozzle that the main stage will use. All held up well, and we tested the bleed valves
for both the main stage and the boosters with success.
We are now working on the booster retention mechanisms and getting those attached to the boosters and main stage.
The update from last Saturday's launch event is also now available on the main site:
http://www.AirCommandRockets.com/day53.htm
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Sunday, January 27, 2008
NSWRA and Polaron IV Main Stage
Yesterday was a fantastic day for rockets. We are now members of the newly re-grouped NSW Rocketry Association (NSWRA) and went to one of their launch events at Doonside. There were many rockets flown on the day and we got a chance to fly three of ours.
We ended up finishing the Polaron IV main stage rocket at about midnight the night before and so we got a chance to test it. We flew it twice with the full payload (new camera, altimeter and flight computer). Both flights were very good and the new parachute also worked well.
The Polaron IV rocket is now pretty much ready to be fitted with the boosters and ready to go. We will probably run some tests first on the boosters being launched from the new launcher with a dummy main stage.
Full details of the flight day will be published shortly with pictures and videos.
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We ended up finishing the Polaron IV main stage rocket at about midnight the night before and so we got a chance to test it. We flew it twice with the full payload (new camera, altimeter and flight computer). Both flights were very good and the new parachute also worked well.
The Polaron IV rocket is now pretty much ready to be fitted with the boosters and ready to go. We will probably run some tests first on the boosters being launched from the new launcher with a dummy main stage.
Full details of the flight day will be published shortly with pictures and videos.
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Friday, January 25, 2008
Black Tape and Sun
As I was inspecting a couple of our rockets last night and getting them ready for tomorrow's launch day, I noticed that the bottles were warped in a couple of places. It appears that the warping was most severe where the wide black tape was. This also occurred on the unpressurised sections of the rocket.
This was likely to have been caused during the last launch day when we left the rockets sitting out in the sun for a couple of hours. The heat absorbed by the tape was enough to shrink the bottles a little under the tape.
This is likely to occur to other rockets that are painted in dark colours. I think we will be storing our rockets in the shade from now on, and perhaps switch to lighter coloured tape when the black stuff runs out.
I spent most of the last couple of nights trying to get the Polaron IV main stage ready for flight on Saturday. The payload section now has the new FlyCamOne camera built in, the Z-log altimeter, servo motor, batteries and a newly built version of our flight computer (V1.3.2). I just have to attach the door and latch mechanism to the payload bay and then attach the whole thing to the rocket body.
We want to test fly it by itself to make sure all the systems and recovery works before we attach the boosters to it.
If we do get to fly it this weekend, I will post pictures soon after that.
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This was likely to have been caused during the last launch day when we left the rockets sitting out in the sun for a couple of hours. The heat absorbed by the tape was enough to shrink the bottles a little under the tape.
This is likely to occur to other rockets that are painted in dark colours. I think we will be storing our rockets in the shade from now on, and perhaps switch to lighter coloured tape when the black stuff runs out.
I spent most of the last couple of nights trying to get the Polaron IV main stage ready for flight on Saturday. The payload section now has the new FlyCamOne camera built in, the Z-log altimeter, servo motor, batteries and a newly built version of our flight computer (V1.3.2). I just have to attach the door and latch mechanism to the payload bay and then attach the whole thing to the rocket body.
We want to test fly it by itself to make sure all the systems and recovery works before we attach the boosters to it.
If we do get to fly it this weekend, I will post pictures soon after that.
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Tuesday, January 22, 2008
Booster Tests and Launcher Details
We've updated the main site with the latest details of the Polaron IV launcher and the new Gluon boosters.
The name Gluon was chosen because it continues with the sub-atomic particle naming convention we have been using for our rockets and also because it is our first operational spliced rocket using PL Premium glue.
The update can be found here:
http://AirCommandRockets.com/day52.htm
The update also includes a video of the booster tests. It's not overly exciting but included for those who are interested.
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The name Gluon was chosen because it continues with the sub-atomic particle naming convention we have been using for our rockets and also because it is our first operational spliced rocket using PL Premium glue.
The update can be found here:
http://AirCommandRockets.com/day52.htm
The update also includes a video of the booster tests. It's not overly exciting but included for those who are interested.
____________________________________________
Monday, January 21, 2008
Launcher and Booster Tests
We've had a very productive weekend this week. We completed the majority of the new Polaron IV launcher, spending about 8 hours in the workshop on Saturday.
The image below shows the state of the launcher currently. I will do a full update this week and post it on our main website that shows all the details and discuss some of the design issues.
On Sunday it was too windy to launch regular rockets and so we opted to do a number of booster test launches. We fitted a booster with a regular nozzle and launched it from our medium launcher. The main aim of the test was to see how the booster behaved in flight and how its recovery system would work. Full details of the booster will also be posted with the next web update.
The larger parachute is now finished for the Polaron IV rocket and the payload section is also well under way. With the altimeter, flight computer, and video camera, the payload section alone is worth around $300. Hmmm... I think I will add a padded nosecone extension for protection in the trial flights. This padded nosecone will be removed for the higher performance flights once the design is proven.
____________________________________________________________
The image below shows the state of the launcher currently. I will do a full update this week and post it on our main website that shows all the details and discuss some of the design issues.
On Sunday it was too windy to launch regular rockets and so we opted to do a number of booster test launches. We fitted a booster with a regular nozzle and launched it from our medium launcher. The main aim of the test was to see how the booster behaved in flight and how its recovery system would work. Full details of the booster will also be posted with the next web update.The larger parachute is now finished for the Polaron IV rocket and the payload section is also well under way. With the altimeter, flight computer, and video camera, the payload section alone is worth around $300. Hmmm... I think I will add a padded nosecone extension for protection in the trial flights. This padded nosecone will be removed for the higher performance flights once the design is proven.
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Friday, January 18, 2008
Holidays over
Having been OS for the last 3 weeks the holidays are over, and we are back in full time production of the Polaron IV launcher and rocket. We are concentrating our efforts on this in order to get it done as soon as possible. During the holidays dad machined up a lot of the necessary components for the launcher, and now we are pretty much ready to start assembling it all together. Dad also did a bit of work around the workshop putting up some new shelves and fixing a few things making it easier to do development.
The Polaron IV rocket will also be fitted with one of the new FlyCamOne cameras as well as the altimeter. I am weighing up whether to build the next version of the flight computer for this rocket or just use one of the existing ones. I may use V1.3.1 in the first few trials and then upgrade when the next version is finished.
This weekend looks like weather is not going to play ball so workshop time is in order. Hopefully we can get most of the launcher done.
This launcher is intended to take us up to the next level in rocket pressure and size. We eventually intend to be launching reinforced rockets from this launcher and hence it is being designed to handle 35bar (500psi) operational pressure. It will support both single nozzle rockets as well as rockets with 3 boosters. The booster nozzles can slide in and out allowing us to used different sized boosters and main stage.
I'll take some pictures over the weekend of the launcher and post them here or on the main site.
PL Premium Glue
We still have a number of tubes of 10oz (300ml) PL Premium glue available so if anyone in Australia is interested please let us know. Just email me: katz.george at gmail.com.
The tubes are AUD$8 each + shipping from Sydney. Standard postage rates apply. You can check the Australian Post office website for shipping charges.
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The Polaron IV rocket will also be fitted with one of the new FlyCamOne cameras as well as the altimeter. I am weighing up whether to build the next version of the flight computer for this rocket or just use one of the existing ones. I may use V1.3.1 in the first few trials and then upgrade when the next version is finished.
This weekend looks like weather is not going to play ball so workshop time is in order. Hopefully we can get most of the launcher done.
This launcher is intended to take us up to the next level in rocket pressure and size. We eventually intend to be launching reinforced rockets from this launcher and hence it is being designed to handle 35bar (500psi) operational pressure. It will support both single nozzle rockets as well as rockets with 3 boosters. The booster nozzles can slide in and out allowing us to used different sized boosters and main stage.
I'll take some pictures over the weekend of the launcher and post them here or on the main site.
PL Premium Glue
We still have a number of tubes of 10oz (300ml) PL Premium glue available so if anyone in Australia is interested please let us know. Just email me: katz.george at gmail.com.
The tubes are AUD$8 each + shipping from Sydney. Standard postage rates apply. You can check the Australian Post office website for shipping charges.
______________________________________________
Monday, January 07, 2008
Katz Stager and new cameras
Katz Stager
While developing our regular rockets we have been working on a new staging mechanism in the background - the Katz stager. We normally don't release details of concepts until we test fly them, but since it's been a while that we've done an update I thought I'd include it. We have built a prototype and test fired it a number of times by hand, but it is still to fly and at full pressure.
The full details of the stager and photos of the prototype can be found here:
http://www.AirCommandRockets.com/day51.htm
New video cameras
We have also bought a pair of FlyCamOne V2 video cameras this week. So far we are very happy with the functionality and performance of these cameras, and are looking forward to mounting them inside rockets and flying them. They can record video at 640 x 480 resolution @ 25fps with sound, which is not bad for a 37 gram package. Recording onto an SD card allows you to get up to 30 minutes of video. Compare that to our existing cameras that record 320 x 240 @ 15fps and can only capture 30 seconds of video.
The other nice feature is the optional external power supply, the swiveling lens+sensor for minimal drag in the air stream and external shutter contacts to allow a flight computer to trigger recording or take 1280 x 1024 pictures.
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While developing our regular rockets we have been working on a new staging mechanism in the background - the Katz stager. We normally don't release details of concepts until we test fly them, but since it's been a while that we've done an update I thought I'd include it. We have built a prototype and test fired it a number of times by hand, but it is still to fly and at full pressure.
The full details of the stager and photos of the prototype can be found here:
http://www.AirCommandRockets.com/day51.htm
New video cameras
We have also bought a pair of FlyCamOne V2 video cameras this week. So far we are very happy with the functionality and performance of these cameras, and are looking forward to mounting them inside rockets and flying them. They can record video at 640 x 480 resolution @ 25fps with sound, which is not bad for a 37 gram package. Recording onto an SD card allows you to get up to 30 minutes of video. Compare that to our existing cameras that record 320 x 240 @ 15fps and can only capture 30 seconds of video.
The other nice feature is the optional external power supply, the swiveling lens+sensor for minimal drag in the air stream and external shutter contacts to allow a flight computer to trigger recording or take 1280 x 1024 pictures.
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Saturday, December 15, 2007
Fire and Water details available
We have updated the main site with the details of the launch event from last Saturday. The update includes a video of the highlights.
http://www.AirCommandRockets.com/day50.htm
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http://www.AirCommandRockets.com/day50.htm
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Monday, December 10, 2007
Fire and Water
We had a great launch day event yesterday. We met up with a couple of pyro guys from the Australian Rocketry forum and the weather at the new launch site co-operated as well. We did a total of five flights (all with on-board video) and they too launched a number of theirs. We also did a combined effort and strapped our video camera to the side of one of their rockets. It's interesting to see how similar the view is from both types of rockets, especially when using foam in the water rocket.
I was fascinated to see their pyro rockets close up, and the preparations needed to get them going. The pyro rockets sure are a lot less messy. Ultimately the same parameters apply to both disciplines in terms of drag, stability, thrust etc.
The new George Kendall Reserve launch site was also very good. There were only a few people about and the clearance range is greater compared to our usual launch site. Being only about 35 minute drive from home is not bad. It's definitely a place to test the next stage of development.
Over the next few days I will do a full web update with photos and videos again.
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I was fascinated to see their pyro rockets close up, and the preparations needed to get them going. The pyro rockets sure are a lot less messy. Ultimately the same parameters apply to both disciplines in terms of drag, stability, thrust etc.
The new George Kendall Reserve launch site was also very good. There were only a few people about and the clearance range is greater compared to our usual launch site. Being only about 35 minute drive from home is not bad. It's definitely a place to test the next stage of development.
Over the next few days I will do a full web update with photos and videos again.
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Monday, December 03, 2007
Polaron IV progress
We didn't get to fly this weekend due to the adverse weather conditions, but at least we made progress on the Polaron IV rocket. The 8L rocket main stage pressure vessel is now finished, with reinforcement of the bottle bases based on the technique described during our last update. We had to machine up a new base to base coupling that was longer than normal because it has to go through 4 thick PET walls with washers in between. When we now heat shrink the reinforcing sleeves, we fill the inner bottle completely with water and pressurise it to about 15psi. We also use a blow torch set to a low flame to get better control over the heating location.
We have yet to pressure test the main stage, but I am hoping that 130psi will be a safe launch pressure. After a couple of failures at 120psi of similar Robinson coupled 2-liter bottles, we have been reluctant to push the pressures much higher. Hopefully this reinforcement technique will allow us to do that.
We have also started modeling some of the launcher components and staging mechanisms in 3DStudio Max to get a better idea how it's all going to fit together. It also allows us to check for clearances before cutting any metal.
Dad has also prepared hoses and another pressure regulator that goes up to 25 bar (~360psi) with the associated high and low pressure gauges. This will allow us to launch a rocket with a different pressure to that of the boosters. This way we can optimize the performance depending on the structural integrity of the different elements.
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We have yet to pressure test the main stage, but I am hoping that 130psi will be a safe launch pressure. After a couple of failures at 120psi of similar Robinson coupled 2-liter bottles, we have been reluctant to push the pressures much higher. Hopefully this reinforcement technique will allow us to do that.
We have also started modeling some of the launcher components and staging mechanisms in 3DStudio Max to get a better idea how it's all going to fit together. It also allows us to check for clearances before cutting any metal.
Dad has also prepared hoses and another pressure regulator that goes up to 25 bar (~360psi) with the associated high and low pressure gauges. This will allow us to launch a rocket with a different pressure to that of the boosters. This way we can optimize the performance depending on the structural integrity of the different elements.
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Tuesday, November 27, 2007
Polaron IV boosters
We have been working on Polaron IV and its launcher in the background while doing the foam experiments. We have further refined plans now on how the boosters will be attached and how they will separate. The photo above shows three newly machined 13mm aluminium nozzles for the boosters.
Each booster is 90mm wide, 2.3L capacity weighs ~150grams dry including recovery system, has a 13mm nozzle and uses a 450mm launch tube.
The simulator predicts that individually each booster should reach about 130m (430') @ 120psi, however, each of the boosters is intended to lift an additional 900 gram weight. This additional weight being a third of the total weight of the main stage fully loaded with water. Under these conditions the predicted altitude of each booster is around 35m (120'). Giving the main stage a release velocity of ~ 25 m/s.
The calculation gets a little trickier because the main stage also fires at the same time when boosters are launched. Though the main stage only uses a 7mm nozzle and foam so that the overall thrust from the main stage will be much smaller compared to the boosters. The consequence of this additional thrust from the main stage means that each booster has less to lift and therefore will be released at a higher altitude and higher velocity. We will do these additional
calculations when we finish building the main stage and know its parameters in detail.
At 120psi, each booster will produce around 90N of thrust at release and about 190N at the end of the launch tube. That is a combined booster thrust of around 570N as the rocket clears the launch pad. Compare that to the Main stage that will produce around 55N thrust with water only and likely around 35N with foam. From static experiments we found that the main stage should thrust for about 6-7 seconds. Rough estimates for main stage altitude are around 230m (750') at the 120psi level. Actual flight though may vary from this figure if the rocket does not go vertically.
The launcher under construction will have two separate air supply lines allowing us to use different pressures in the boosters compared to the main stage. This should allow us to experiment with a wider variety of rocket configurations. Full plans will be published once the design is finalised and the rocket is tested.
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Wednesday, November 21, 2007
Foam vs. Water-only flight test results
We have updated our main site with the results of the foam vs. water-only test flights.
http://www.AirCommandRockets.com/day49.htm
In the analysis we show that foam flights were about 2-3% lower in altitude than the water only rockets. This was a little dissapointing but also encouraging in other ways and certainly gives us a direction for further research with foam. Since the update We tweaked the simulation's drag coefficient and nozzle loss factor so the simulation matched the highest observed water-only flight altitude. We then added the weight and drag of the attached camera, upped the pressure to 120psi and ran the simulation again. The predicted water-only altitude was 350'. The last camera mission on the day was a foam flight with the camera and the altimeter. The altitude measured was 353'. This would put foam on par with water-only.
The altitudes are too close together to be able to make any definitive conclusions one way or another, and a lot more flights are required.
There are a few reasons we want to pursue foam experiments further:
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http://www.AirCommandRockets.com/day49.htm
In the analysis we show that foam flights were about 2-3% lower in altitude than the water only rockets. This was a little dissapointing but also encouraging in other ways and certainly gives us a direction for further research with foam. Since the update We tweaked the simulation's drag coefficient and nozzle loss factor so the simulation matched the highest observed water-only flight altitude. We then added the weight and drag of the attached camera, upped the pressure to 120psi and ran the simulation again. The predicted water-only altitude was 350'. The last camera mission on the day was a foam flight with the camera and the altimeter. The altitude measured was 353'. This would put foam on par with water-only.
The altitudes are too close together to be able to make any definitive conclusions one way or another, and a lot more flights are required.
There are a few reasons we want to pursue foam experiments further:
- It's a lot of fun.
- The residual foam weight issue, described in the update, could point towards a measurable advantage when solved.
- These tests were only carried out at low pressures, enough to get the rocket off the ground. As the pressures increase, the take-off and peak velocities will also increase. Due to the difference in velocities between water and foam powered rockets (water = faster & shorter burn, foam = slower & longer burn) the difference in drag will play a more signigficant role since drag is proportional to the square of the velocity. This should favour foam at higher pressures.
- Convergent/Divergent (DeLaval) nozzles are yet to be fully analyzed. Although initial tests showed them to be no better at low pressures, higher pressures and nozzle shape optimization are still yet to be tested.
- Use of foam may be more optimal for upper stages of a rocket than for the main stage. More simulation is needed.
- Efficient generation of foam. From foam thrust measurements we found that foam generated using the Jet Foaming technique produced about 14% less total impulse. We have yet to test alternative ways of generating foam that may be more efficient. A couple of new foam generation ideas are already on the drawing board.
- Foam optimisation. So far we have only been using the same ratio of bubble bath to water when mixed, but other combinations will need to be tested.
- Different foaming agents. So far we have only tested kids bubble bath to generate foam. There are much better foaming agents available and foam density and viscosity are likely to play key roles in the efficiency.
- The test results from all these experiments and data from other rocketeers may be used to build a foam simulation model for further research.
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Monday, November 19, 2007
Great Flight Day
We had an excellent flight day on Sunday. The weather was ideal and none of the rockets crashed. We tested the water-only vs foam flights and got altimeter data for all of them. Virtually all the flights were vertical.
I am in the process of doing a full web update but it will take a day or two to collate all the data and get the videos updated.
The update will also cover bottle reinforcing techniques and their results.
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Tuesday, November 13, 2007
Flight Computers & Misc
Most of this week has been spent working on a new design for the flight computer. As mentioned in the web update a couple of weeks back, we want to make it more automated to enable remote operation. We are building our own IR remote so that we can have full control over its operation. Most of that hardware is now designed and part of the remote's software has been written.
The new flight computer will not have any buttons except for the power switch, instead it will have the IR sensor module. It will also have a small speaker to acknowledge mode changes as well as serving as a recovery aid should the rocket fall in tall grass. The flight computer will also support two servos for staging and recovery as well as the capability to support the Zlog altimeters. The flight computer will be able to start the altimeter recording once the flight computer is armed.
Most of the design for this new hardware is now complete, with about half of the software still to be written.
We have now repaired J4III's body and fins, and are in the process of remounting components in the payload bay in order to protect them better during impact. J4III will now also sport the new shock absorbing nosecone to help provide even more protection should the parachute fail.
We have also made our first jacketed bottle that includes a Robinson coupling. We have pressure tested it to 100psi to check for leaks around the coupling, but will need to burst test it to see how much it can actually hold. If the burst tests are successful we would be aiming for launch pressures of around 180psi. While we believe the bottle burst pressure will be around 220psi+ the Robinson coupling is the biggest unknown.
If the weather holds up this weekend we will try to go back and do the foam and water comparison flights.
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The new flight computer will not have any buttons except for the power switch, instead it will have the IR sensor module. It will also have a small speaker to acknowledge mode changes as well as serving as a recovery aid should the rocket fall in tall grass. The flight computer will also support two servos for staging and recovery as well as the capability to support the Zlog altimeters. The flight computer will be able to start the altimeter recording once the flight computer is armed.
Most of the design for this new hardware is now complete, with about half of the software still to be written.
We have now repaired J4III's body and fins, and are in the process of remounting components in the payload bay in order to protect them better during impact. J4III will now also sport the new shock absorbing nosecone to help provide even more protection should the parachute fail.
We have also made our first jacketed bottle that includes a Robinson coupling. We have pressure tested it to 100psi to check for leaks around the coupling, but will need to burst test it to see how much it can actually hold. If the burst tests are successful we would be aiming for launch pressures of around 180psi. While we believe the bottle burst pressure will be around 220psi+ the Robinson coupling is the biggest unknown.
If the weather holds up this weekend we will try to go back and do the foam and water comparison flights.
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Tuesday, November 06, 2007
Progress
This week we continued working on the stager mechanism. We finished enough of it to test it staging just in the back yard. We used only air at 20psi a couple of times and at 50psi once. Although it worked it was a little stiff to release and that is something we need to look at. We will probably try softer o-rings first. We still have a major design issue to resolve, but have some ideas. (More on this later)
The camera that wasn't behaving during the last launch day appears to be OK, and the cause looks like a poor battery contact. The contacts must have become more compressed inside the camera. We tried it with another battery that has taller solder blobs on the contacts and that worked fine, even when shaking the camera.
We also had a go at building the first prototype of the shock absorbing nosecone. It basically consists of the top 3/4 of a PET bottle which is filled with soft foam. The sides of the bottle have 8 longitudinal cuts all the way around that allow the bottle to easily split and slide over the existing nosecone. It is lightly taped over the top to enable the tape to separate easily on impact. During a crash the padded nosecone slides down and the foam compresses against the internal nosecone, but also the whole thing acts as an air piston to dampen the shock even more. The prototype weighs 35 grams so not a very significant weight penalty. For record flights, this can be removed and the existing nosecone underneath can just be used.
We have also been on the lookout for new launch sites around Sydney with great help from the local rocketry community. We looked at one location (George Kendall Reserve) that looks pretty good and is only about half hour from home.
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The camera that wasn't behaving during the last launch day appears to be OK, and the cause looks like a poor battery contact. The contacts must have become more compressed inside the camera. We tried it with another battery that has taller solder blobs on the contacts and that worked fine, even when shaking the camera.
We also had a go at building the first prototype of the shock absorbing nosecone. It basically consists of the top 3/4 of a PET bottle which is filled with soft foam. The sides of the bottle have 8 longitudinal cuts all the way around that allow the bottle to easily split and slide over the existing nosecone. It is lightly taped over the top to enable the tape to separate easily on impact. During a crash the padded nosecone slides down and the foam compresses against the internal nosecone, but also the whole thing acts as an air piston to dampen the shock even more. The prototype weighs 35 grams so not a very significant weight penalty. For record flights, this can be removed and the existing nosecone underneath can just be used.
We have also been on the lookout for new launch sites around Sydney with great help from the local rocketry community. We looked at one location (George Kendall Reserve) that looks pretty good and is only about half hour from home.
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