The Effect of Acceleration on the Crystallization of Sodium Acetate

Transcription

1 May 29th, 2010 The Effect of Acceleration on the Crystallization of Sodium Acetate Madison West High School New Team First Row: John, Enrique, Zoë, Rose Second Row: Yifan, Duncan, Ben, Jacob, Suhas SLI 2010 Post Launch Assessment Review 1

2 Table of Contents Vehicle... 3 Entire Vehicle... 3 Sustainer... 3 Flight Summary... 4 Payload... 9 Introduction/Overview... 9 Rationale Hypothesis Procedures Post Flight Procedure Crystal Analysis Procedure Collected Data Crystal Structure Data Identified Crystal Deforming Events Crystal Temperature and Impurity Data Analysis Match with Hypothesis Sources of Possible Error Lessons Learned Possible Improvements Further Questions Educational Engagement Summary

3 Vehicle Entire Vehicle Figure 1: A two dimensional schematic of the entire rocket Vehicle Parameters Length [in] Weight [lbs] Diameter [in] Motor Selection Stability Margin [calibers] Thrust to weight ratio AT-K1100T Table 1: The rocket s dimensions, stability and propulsion Sustainer Figure 3: A two dimensional schematic of the sustainer Sustainer Parameters Stability Thrust to Length Weight Diameter Motor Margin weight [in] [lbs] [in] Selection [calibers] ratio AT-J1299N Table 2: The dimensions of the sustainer, stability margin and propulsion 3

4 Flight Summary The booster lifted off the pad without weather-cocking. It coasted to apogee of 1582 feet and deployed the drogue parachute. The booster was safely recovered with no damage. Figure 6: The altitude vs. time graph of our booster flight data from Huntsville The sustainer separated from the booster at 1.7 seconds, and flew to an apogee of 4957 feet. At apogee a charge went off to deploy the drogue parachute. The charge failed to deploy the drogue, and due to our use of an Advanced Rocket Recovery Device (ARRD), the main parachute also failed to deploy. We believe the charge did not work because we increased the free volume of the compartment after the hardware check. The pressure from the charge was not great enough to separate the two sections. At the hardware check, the Safety Officer discovered that our drogue was anchored to a plastic loop on the rear end of the nose cone. This attachment point was not considered robust enough to safely hold the drogue. We were instructed to remove the rear end and attach the drogue to an I-bolt in a ring we had installed inside the nose cone. We failed to notice that with the rear end removed, the free volume of the compartment increased significantly. Due to our oversight, the charge was not powerful 4

5 enough to provide adequate ejection pressure, and the drogue was not deployed. The sustainer tumbled to the ground, receiving damage to the external tube. The fin can did not suffer any damage, and we replaced the external tube and were able to re-fly the full configuration rocket in May. Figure 5: The altitude vs. time graph of our sustainer flight data from Huntsville Booster Sustainer Figure 6: Recorded descent rates from Huntsville Descent Rate 30.1 Feet/sec. 62 Feet/set. (no parachute) 5

6 Figure 7: The rocket launches on a K1100T in Huntsville 6

7 Figure 8: The rocket launches on a K282FJ in Richard Bong State Recreation Area in May 7

8 Figure 9: Flight sequence of the rocket from liftoff to touchdown 1. First stage burn, reaction starts 2. Stage separation 3. Booster coasts to its apogee and deploys drogue parachute 4. Booster deploys main parachute 5. Booster lands safely 6. Second stage motor burn 7. Sustainer reaches apogee, deploys drogue parachute. 8. Sustainer descends under drogue. 9. Sustainer deploys main parachute. 10. Sustainer lands safely. 8

9 Payload Introduction/Overview Our payload was designed to analyze the effects of high and low acceleration on the crystallization of a supersaturated sodium acetate solution. We crystallized multiple tubes of sodium acetate with various impurities during rocket flight. Our experiment involved the analysis of reaction temperature profiles, and a post-flight study of crystal formation. Figure 2: Photographic overview of our payload (Clockwise from Top Left, top of payload showing power connections, side of payload showing RAS and DPSS as well as reaction vessels, and the full payload with bent tie rod from Huntsville) 9

10 Rationale The sodium acetate crystallization reaction reaches a temperature of 54 degrees Celsius and maintains this temperature for the duration of the reaction. Furthermore, the crystallized solution can be melted and reused indefinitely with zero waste. Because of this the sodium acetate reaction has applications as a renewable energy source, and could potentially be used as a super-efficient method for heating space stations in orbit. Before sodium acetate can be used in this function, it is important to determine whether it will behave the same way under differing gravitational conditions. Hypothesis We expect changes in the crystallization structure, consistent with the varying gravitational forces, and changes in the crystallization gradient. Furthermore, we anticipate that dopes will result in different crystallization structures and crystallization gradients. Procedures Preparation for flight 1. Check electronics for functionality. 2. Check the reactor vessels for leaks and premature crystallization. 3. Secure reactor vessels into each payload module and connect ribbon cables, and servos to the Data Processing and Storage System. 4. Turn the Data Processing and Storage System on. 5. Calibrate the servos. 6. Turn the Data Processing and Storage System off. 7. Slide the payload modules into the rocket. 8. Turn the Data Processing and Storage System on again at the launch pad, immediately before launch. Post Flight Procedure We removed the payload from the rocket by unscrewing the bulkheads holding it in place. Then, we removed the reaction vessels from the payload by unscrewing the tie rods holding the payload together and retracting the activation needles. When the payload was completely disassembled, we removed the membrane caps (which had been punctured by the activation needles) from the reaction vessels and exchanged them with solid caps in order to prevent liquid leakage from the crystallized vessels. The reaction vessels were then placed into foam rubber storage to prevent damage during transportation to the lab where we were to do analysis. Crystal Analysis Procedure We placed the reactor vessels with crystallized sodium acetate solution on a polarizing filter covered light box. We placed another filter on the camera to remove the polarized light that did not pass through any crystals. Using this method, the polarized light that crossed through crystals in the reactor vessels would appear in the macro image, giving 10

11 us enhanced quality. Several pictures were taken across one side of the reactor tube, and then a panorama of the tube was created. We printed a zoomed-in version of the panorama and identified all the major events on it. Then a digital version was made based on the printed version. We used the same method for individual crystal clusters that were extracted from sodium acetate tubes crystallized on ground and compared them to crystallized tubes from our flown payload. Collected Data Crystal Structure Data Using the light box and polarized light filter we were able to produce multiple sets of macro images of our reactor vessels. Examining these photos along with our acceleration data we were able to piece together the deformities caused by flight events. We were able to locate on the picture: initiation, liftoff, first stage burnout, second stage ignition, second stage burnout, coast zone and apogee/flat spin. Using these points as reference we created a timeline of the events and located the corresponding gravitational forces on the photos. We located the areas of high Gs and areas of low Gs and examined the crystal structures in depth at those locations. From this we found that under high Gs there were a lot more nucleation sites, many crystals clumped together, and smaller sized crystals. Under low gravitational forces there were fewer nucleation sites and larger crystals. 11

12 Identified Crystal Deforming Events Initiation: The seed crystals inside the hypodermic needle create a nucleation site and the crystals fan out from that one point. As time passes the crystals form away from the nucleation site in all directions. Liftoff: At the exact moment of liftoff, the crystals begin to cluster and the smooth fan shape disappears. Instead, nucleation sites appear everywhere between liftoff and burnout. The crystals are smaller and are stacked on each other. First stage burnout: The crystals experience a few moments of low Gs. Here the crystals are still small, but there aren t any nucleation sites that we could identify. Second stage ignition: During this high Gs interval, we expected the same crystal formations as liftoff. Again, the crystals are small, and clustered together, branching out from multiple nucleation sites. This time, the crystals are cleaner in a way that the crystals are compressed even closer together and there were not as many bubbles. Second stage burnout: The crystals continue to form from several nucleation sites in random areas, and form compressed, crystal clusters. Coast zone: It is easier to identify the separate crystals because they are not forming compressed clusters anymore and it is in low Gs. The nucleation sites are easier to recognize too. Apogee/flat spin: This area contains numerous bubbles, due to the twirling of the reactor vessels inside the falling rocket. This is the area with the least amount of reliable data Figure 3: Acceleration profile of our flight in Huntsville, with flight events highlighted. 12

13 Figure 4: Crystalized reaction vessel, with acceleration profile and crystal structure deformitites 13

14 Crystal Temperature and Impurity Data During the preparation of the supersaturated supercooled sodium acetate solution prior to our launch, contamination in the reaction vessels prevented us from flying instrumented reactor vessels. The construction of the instrumented reactor vessels allowed small particulate nucleation sites to be harbored in the small spaces between the thermistor and the wall of the tube (See Figure 2). This site allowed both the sodium acetate crystals and the crystals of the various dopes to avoid our vigorous cleaning methods in the lab. We also had three impurities we chose to use for our testing were: sodium chloride, potassium permanganate, and copper sulfate. We began mixing these chemicals into our sodium acetate solution in a small beaker; there we were Figure 5: Diagram of possible nucleation sources able to produce what we believed to be a stable solution. After placing them into the reaction vessels they stayed liquid for about an hour, before crystallizing. We were not able to produce any successful doped solution for the flight. These dope crystals also resulted in an extremely unstable solution. After doing more tests we concluded that the extra dopes in our solution made it to unstable for extended periods of time. These many factors combined unfortunately meant that all of the lab prepared crystallization vessels that were filled with supersaturated solution spontaneously crystallized the night before the launch due to these small nucleation sites that could not be cleaned from the tubes. This also meant that there was not time nor resources to prepare new reaction vessels, so we were forced to fly without a payload at our May 23 rd Launch. Analysis Match with Hypothesis As mentioned before, we believe the thermistors were a possible nucleation site for the sodium acetate crystals because the entire set of reactor vessels equipped with thermistors experienced premature crystallization. The added impurities also made the solution unstable so no data for crystal structure and crystallization gradient was collected. The reactor vessels that were in our flown payload had no thermistors, so we were able to use them in our payload. We analyzed the crystal structures from these crystallized tubes and concluded that the varying acceleration profiles had a significant impact on the crystal structures. We could identify the each flight event based on the obvious change of crystal structure in the crystallized tube. 14

15 Sources of Possible Error Although we produced tubes of pure sodium acetate during the launch, we were not able to test all aspects of our experiment. Our extensive research on the sodium acetate solution concludes that it is a very stable solution. Therefore, we believe the unwanted premature crystallization happened as a result of the added impurities. We also believe the thermistors could have served as a nucleation site for the sodium acetate crystals. During crystal analysis, our lack of dedicated equipment may have resulted in inaccurate observations. Due to an impact at the conclusion of our flight, we believe that the crystals may have shifted forward inside their reactor vessels, causing possible inaccuracies in our comparison of the flight events and time. Lessons Learned We learned many lessons from our experiences this year. We have learned that a liquid chemical payload, especially one that is based on an unstable chemical balance such as a supersaturated solution, is not a very feasible payload option. At every stage in the payload design we had to take into account the possible contamination of the payload, the routing of the many instrumentation wires, and location of moving parts to activate the payload. We also learned that better communication between the electronics and mechanical teams would have resulted in a more integrated payload. Possible Improvements The main problem we faced this year with sodium acetate solutions are the instability of the solutions after we doped them and when there were unwanted nucleation sites where we attached the thermistors. What we could do to improve the results of the experiment is to do more labs testing about dopes. If we had more time to test the impurities we might ve found a combination that was stable enough for flight. Also, we would ve found a better way to attach the thermistors so there wouldn t have been extra nucleation sites created. Further Questions Even though the crystal structures and sizes matched with our hypothesis we still have further questions on the effects of impurities on the crystallization of sodium acetate. We never managed to produce a stable solution with impurities in the sodium acetate. We are wondering why the impurities made the solution so unstable as well as if there are impurities that would be stable with the sodium acetate. Also, we are curious at what changes the impurities would have caused to the sodium acetate. We have considered a new design for the thermistor attachment. If we could eliminate all the extra crystallization points we would be able to find the acceleration gradient with the thermistors. 15

16 Educational Engagement Summary Throughout the year, our club has maintained a high level of community involvement. On several occasions we have helped students at EAGLE (a local K-8 school) build and launch model rockets. We have also participated in the Super Science Fair at Randall Elementary School, built Alka-Seltzer rockets at Lincoln Elementary, and encouraged the pursuit of science and rocketry at various other events. 16