If I reduce electrode spacing by 1 cm starting from 5 cm for every decrease of 20 kPa in atmospheric pressure starting from ~100 kPa, then the wind speed produced by an ionic wind thruster will remain constant because although a smaller number of positively charged ions will be produced in lower atmospheric pressures resulting in limited ion-neutral fluid molecule collisions, the net movement of particles attracted towards the collector will be able to retain more kinetic energy due to the minimized drift zone distance, hence, generating a constant wind speed even in conditions with weaker corona discharge.

Ionic Wind Thrusters

Ionic wind thrusters have recently been considered efficient substitutes for traditional atmospheric aviation devices. This technology’s layout is composed of two electrodes separated by the drift zone (air gap) and attached to a high-voltage battery for electrical power. One electrode is classified as the emitter which is characterized by its rough and pointy structure. The emitter typically holds a positive polarity within this device due to a current output and is made of materials with conductive properties such as copper. As higher voltages are applied (approximately 2-6 kV) to the emitter also known as the corona wire a strong electrical field is produced around the electrode. Therefore, instigating corona discharge, a phenomenon where positively charged ions are created out of neutral fluid molecules due to the detachment of electrons from their respective atoms. Corona discharge can be observed as a purple glow of gas plasma signifying a localized area of fluid particles that have experienced electrical breakdown. Electrical breakdown refers to a potential gradient (electric field) around the emitter that surpasses the surrounding fluids' dielectric capacity (the greatest strength of the electrical field an insulating fluid can resist before experiencing ionization). Corona discharge also consists of a current conveyed by positively charged ions being attracted to the negative electrode (collector). However, in this progression, the ions strike neutral air molecules in the air gap. Thus, initiating the Biefield-Brown effect in which the air particles are opposed from the emitter because ions released from the corona wire transfer momentum to neutral fluid molecules, yielding a net movement of neutral particles directed toward the collector while the ions are recoiled to the emitter as a result of the collision. The Biefield-Brown effect is an electrical scenario first discovered in the 1920s by Thomas Townsend Brown. In other words, the overall movement of neutral particles generates ionic wind required to propel the thruster forward. According to the Biefield-Brown effect, thrust is experienced by the emitter since the positively charged ions bouncing back from the particle interactions will slightly thrust against the emitter as two electric fields of the same polarity repel each other. This situation is backed by Newton’s Third Law of Motion which states, “For every action, there is an equal and opposite reaction.”. The collector is the second electrode primarily taking the shape of a hollow tube with a large diameter. This electrode maintains a negative polarity while being made of aluminum which is an efficient conductor of electricity. This property is important in order to attract and provide direction to the ions formed at the corona wire so that particle collisions can take place. 

Atmospheric Pressure

Atmospheric pressure refers to the pressure observed across Earth’s atmosphere. Pressure represents the force per unit area as 1 Pa = 1N/m². This can be measured in pascals (Pa) which is equivalent to 0.001 kilopascals. The average atmospheric pressure at Earth’s sea level is approximately 101.325 kPa. However, when traveling to higher elevations, the air becomes thinner and reduces the atmospheric pressure. This is because the density of air is decreased due to fewer fluid particles present within a certain volume. Eventually, when you reach space, theoretically, the pressure becomes 0 kPa since there is no air This is called a vacuum. The reason behind this is that at lower elevations (near sea level) the gravitational pull is stronger. Hence, the air particles are held tightly in a specific volume leading to a higher atmospheric pressure. However, with higher altitudes, the gravitational pull becomes weaker and therefore the air becomes less dense due to dispersed particles. Consequently, the atmospheric pressure decreases. 

Electrode Geometry and Spacing

An emitter is preferred to be rough and consist of spikes in an ionic wind thruster since it needs to concentrate the electric field allowing for greater ionization of nearby air particles. Hence, more collisions can occur between the positively charged ions and air particles leading to a stronger wind guided towards the collector. The collector should be large in diameter and smooth/curved on the sides so that it can provide a larger surface area which increases the attraction of positively charged ions. Curved edges of the collector tube increase ionic wind as the flow of neutral fluids is streamlined into the cylindrical structure. Smooth sides of the collector are also beneficial for a uniform electric field which decreases distortions and irregular sparks on the edges, leading to a stable production of thrust. An interior free of roughness and sharp disturbances allows the collector to conduct a regular flow of neutral molecules, maximizing ionic wind speed. It is also ideal for the collector to be large in length and surface area as this allows for more efficient dissipation of heat obtained from rapid transfers of kinetic energy between particles and strong electrical fields. In conclusion, this arrangement of the two electrodes forms an asymmetrical field stronger towards the emitter and more dispersed near the collector. Electrode spacing also plays a crucial role in ionic wind generation. If the emitter and collector are positioned far away from each other, then the ionic wind will be produced at a decreased speed because the neutral fluid molecules will start to lose their kinetic energy upon approaching the collector. If the electrodes are arranged too closely, then there will be electric discharges such as arcing (current transport through undesired passages) leading to decreased efficiency because the electric field will be too concentrated. 

Ionic Wind Thruster:

1. Cut the cardboard into a base measuring 8.1”x6.9”
2. Cut a repeating pattern of triangles measuring a height of 0.5” on the copper strip
3. Bend the copper strip into a circle 
4. Insert the copper strip (circle) into the hollow plastic ring to secure it firmly in place
5. Cut two square pieces of cardboard measuring 1”x1”
6. Hot glue both cardboard adjacent on top of each other
7. Hot glue the cardboard support vertically onto the 8.1”x6.9” base near the center of one edge 
8. Hot glue copper emitter (pointy end facing away from the edge) on top of the cardboard support 
9. Place the polished aluminum tube (opening facing towards copper roughly in the center) 5 cm away from the emitter (copper). Do not glue or fix in place.
10. Insert 4 AA batteries into the battery holder (ensure it is switched off)
11. Tie the red wire of the battery pack with the red wire of the transformer module (tape connection to secure)
12. Tie the black wire of the battery pack with the green wire of the transformer module (tape connection to secure)
13. Attach securely with tape, any output wire of the transformer to the copper emitter
14. Attach securely with tape, any output wire of the transformer to the aluminum collector
15. Switch on the battery pack to ensure that the thruster is working (there should be a buzzing sound)
16. Place the anemometer in front of the collector and observe wind speed (preferably around 23 m/s at 100kPa)

Testing:

1. Remove the lid of the vacuum chamber
2. Attach the hose of the vacuum chamber to the hose of the pump with a transitioner
3. Place thruster mounted on cardboard base into the vacuum chamber
4. Tape the anemometer (display exposed on the outside) on the wall of the vacuum chamber bordering the output opening of the collector (ensure anemometer fan blades align with the center of the collector opening for precise wind speed measurement)
5. Decrease the distance between the emitter and the collector by 1 cm 
6. Switch on the battery pack 
7. Secure chamber lid in place
8. Adjust vacuum pump pressure until the gauge reads “-0.2” 
9. Observe wind speed displayed on the anemometer and record
10. Repeat steps 5-9 three more times; each time reducing the atmospheric pressure by 0.2kPa on the gauge
11. Repeat steps 5-10 four more times; each time changing the distance decreased between electrodes to one of the following decrements: -0.8 cm, -0.6 cm, -0.4 cm, and -0.2 cm 

* Ensure that in the repetition of steps 5-10 four more times, each of the remaining four distance decrements gets tested once 

Ionic Wind Thruster and Testing Pictures:

Setup of ionic wind thruster in vacuum chamber connected to vacuum pump

Front view of ionic wind thruster setup inside vacuum chamber

Side view of ionic wind thruster setup inside vacuum chamber

Below are some examples of wind speed readings on the anemometer (no specific electrode distance). A reading of “HI” on the anemometer means that the wind speed exceeds 33 m/s (wind speed is too high to be measured).

Testing (Quantitative Observations)

Trial 1: Effect of Regular Electrode Distance Decrements on the Wind Speed Produced by an Ionic Wind Thruster Under Regular Decreases in Atmospheric Pressure

Trial 2: Effect of Regular Electrode Distance Decrements on the Wind Speed Produced by an Ionic Wind Thruster Under Regular Decreases in Atmospheric Pressure

Trial 3: Effect of Regular Electrode Distance Decrements on the Wind Speed Produced by an Ionic Wind Thruster Under Regular Decreases in Atmospheric Pressure

Trial 4: Effect of Regular Electrode Distance Decrements on the Wind Speed Produced by an Ionic Wind Thruster Under Regular Decreases in Atmospheric Pressure

Trial 5: Effect of Regular Electrode Distance Decrements on the Wind Speed Produced by an Ionic Wind Thruster Under Regular Decreases in Atmospheric Pressure

Effect of Regular Electrode Distance Decrements on the Wind Speed Produced by an Ionic Wind Thruster Under Regular Decreases in Atmospheric Pressure

Qualitative Observations:

-Electrical arcing occurred when the electrode distance decrement was 1 cm

-Electrical arcing occurred when the electrode distance decrement was 0.8 cm

-The corona discharge glow got progressively dull and less concentrated as the electrode distance decrement was reduced

-The generation of corona discharge was inconsistent and only present on some points of the emitter when the electrode distance decrement was 0.4 cm

-The generation of corona discharge was inconsistent and only present on some points of the emitter when the electrode distance decrement was 0.2 cm

-The buzzing sound’s pitch got progressively weaker as the electrode distance decrement was reduced

-The temperature of both electrodes when touched after testing got progressively weaker as the electrode distance decrement was reduced

-The occurrence of a pungent smell follows the operation of the ionic wind thruster

Evaluation

When comparing the separate electrode distance decrements of 1 cm and 0.8 cm to the control value for every 20 kPa decrease in atmospheric pressure, excessive wind speed along with electrical arcing occurred. This was evident in the data as the average wind speed difference compared to the control value was +3.575 m/s when the electrode distance decrement was 1 cm and +2.025 m/s when the electrode distance decrement was 0.8 cm. This is because decrementing the electrode spacing by 1 cm and 0.8 cm brings the electrodes exceptionally closer causing a minimized drift zone. Consequently, when corona discharge occurs through the ionization of air molecules near the emitter, despite the reduced pressure leading to fewer neutral fluid particles for the ions to collide with, the distance between electrodes remains limited considering the atmospheric pressure decrease of 20 kPa. Hence, the small drift zone increases the attractive force experienced by the ions attracted towards the negatively charged collector. Therefore, increasing the speed of the overall movement of ions and neutral fluid particles, allowing them to quickly travel across the drift zone and collector resulting in a higher wind speed. However, this constant decrease in electrode spacing occasionally resulted in electrical arcing due to the proximity of electrodes. For example, if high voltage is applied to the emitter, then instead of ionizing the surrounding air molecules, an extensively high electric field is produced causing the current to directly travel to the collector. Electrical arcing, however, reduces the thruster’s efficiency because the electrical power is directly discharged rather than being utilized for corona discharge. 

It is crucial to reduce the electrode spacing every time the atmospheric pressure decreases. For example, if you leave the distance between electrodes at 5 cm and regularly decrease the atmosphere pressure by 20 kPa, then it is clear that the wind speed will decrease because fewer air molecules are available to ionize. Therefore, when fewer ions are attracted toward the collector, fewer particles come into contact with the ions. As a result, a sufficient net movement of particles cannot be generated toward the collector. This is simply because not enough neutral fluid particles come into contact with ions in order to produce a stable wind speed. 

When comparing the electrode distance decrement of 0.6 cm to the control value for every 20 kPa decrease in atmospheric pressure, a relatively constant wind speed was produced with minor discrepancies. This was evident in the data as the average wind speed difference compared to the control value was +0.050 m/s when the electrode distance decrement was 0.6 cm. This is because decrementing the electrode spacing by 0.6 cm caused the electrodes to come relatively close, but not close enough to initiate electrical arcing. Thus, all the power was utilized to ionize the air molecules surrounding the emitter. Next, when ionization occurs as part of the corona discharge, the ions are attracted towards the negatively charged collector. Hence, during the Biefield-Brown effect as the ions yield a net movement of neutral fluid molecules toward the collector, the particles have to travel across a slightly larger drift zone. As a result, the wind speed produced by the thruster under an electrode distance decrement of 0.6 cm is comparatively lower than the wind speed produced by the thruster under an electrode distance decrement of 1 cm and 0.8 cm. This is because the drift zone is larger when the electrode distance decrement is 0.6 cm, causing the moving particles to lose more kinetic energy by the time they reach the collector. Therefore, producing a reduced wind speed as the overall movement of particles will not be able to retain a portion of their momentum by the time they reach the collector. 

When comparing the separate electrode distance decrements of 0.4 cm and 0.2 cm to the control value for every 20 kPa decrease in atmospheric pressure, a significantly reduced wind speed was produced. This was evident in the data as the average wind speed difference compared to the control value was -3.525 m/s when the electrode distance decrement was 0.4 cm and -6.225 when the electrode distance decrement was 0.2 cm.  This is because these small distance decrements resulted in a relatively maximized drift zone. Hence, during the Biefield-Brown effect, the ions and neutral fluid particles must travel an extensive distance by the time they reach the collector. This excessive distance also reduces the attractive force experienced by the positively charged ions as they are generated way too far away from the negatively charged electrode. In other words, as the particles drift toward the collector, they start to lose momentum. Consequently, when the particles reach the collector they do not have enough kinetic energy to produce a strong ionic wind. The configuration of small electrode distance decrements and especially lowering atmospheric pressure produced very minimal ionic wind compared to larger decrements because of the lack of dielectric material. For example, air acts as the dielectric material in ionic wind thrusters because it has low conductivity, making it ideal for preventing electrical arcing between the emitter and collector. However, as the atmospheric pressure is regularly reduced, the amount of fluid/air particles present in a specific volume is decreased. Hence, when an asymmetrical electric field is generated as a result of the emitter's pointy characteristics and the collector's smooth and broad structure, the concentrated field around the emitter is not able to ionize many fluid particles because they simply is not available due to the low atmospheric pressure. On the other hand, the available fluid particles are ionized when they experience electrical breakdown. Electrical breakdown refers to high voltages applied to the emitter that cause the local electric field to surpass the dielectric capacity of the surrounding neutral fluid particles. Dielectric capacity refers to the greatest strength of the electric field that fluid particles such as air can withstand before their respective electrons start detaching to produce positively charged ions.

Trend

The primary trend was as expected; a decreased ionic wind speed was produced as the electrode distance decrement was reduced. This was evident in the data as the wind speed difference compared to the control value was the greatest at 1 cm and lowest at 0.2 cm. This is because as different decrements are tested in a constantly decreasing atmospheric pressure of  20 kPa, the drift zone varies. For example, the drift zone will be maximized when the electrode distance decrement is 0.2 cm and minimized at 1 cm. Therefore,  this reduction in electrode spacing needs to be able to keep up with the constantly lowering fluid particles in set volume as the pressure decreases. This means that at 1 cm, the strongest wind speed will be produced as the electrodes are brought exceptionally close. Hence, even though fewer particles are ionized, the ions and neutral fluid particles will have to travel a smaller distance, allowing them to retain more kinetic energy. However, as the electrode distance decrement decreases, the space between the collector and emitter starts increasing, causing the ions and neutral fluid particles to travel a greater distance and progressively lose more momentum. Thus, the wind speed declines. 

Outliers

The first outlier observed in the data was noted during trial one when the 1 cm electrode distance decrement produced an average wind speed difference of +2.125 m/s. For example, this is considered to be an outlier because +2.125 m/s is closer to the average wind speed difference (across five trials) of +2.025 m/s produced when the electrode distance decrement was 0.8 cm. A potential reason for this outlier could be that during the electrode distance decrement of 1 cm, the emitter and collector could have gotten exceptionally close in regards to the atmospheric pressure. Thus, potentially triggers electrical arcing that results in excessive electricity being discharged directly between the electrodes as opposed to the electricity being utilized in the corona discharge process for ionization. If complete electricity was used for the ionization, more ions would be available during the Biefield-Brown effect therefore yielding a greater net movement of particles towards the collector (meaning more ionic wind).

The second outlier observed in the data was observed during trial one when the 0.2 cm electrode distance decrement produced an average wind speed difference of -4.000 m/s. For example, this is considered to be an outlier because -4.000 m/s is closer to the average wind speed difference (across five trials) of -3.525 m/s produced when the electrode distance decrement was 0.4 cm. A potential reason for this outlier could have been minor malfunctions in the vacuum chamber or the gauge not accurately sensing and displaying the atmospheric pressure. In this case, the vacuum chamber may not have displaced a significant amount of air every time the pressure decreased by 20 kPa. Thus, comparatively keeping more air particles in a set volume compared to the other 0.2 cm trials. Therefore, there still could have been more fluid particles available for ionization compared to the other 0.2 cm trials. Hence, with more fluid particles available in a set volume, more electrons can be stripped away from respective atoms, allowing for more ions to be produced. More ions result in a greater amount of neutral fluid particles colliding with ions, therefore, increasing the amount of particles present in the overall movement towards the collector. Hence, a slightly stronger wind speed will be generated. 

Conclusion

In conclusion, my hypothesis stating “If I reduce electrode spacing by 1 cm starting from 5 cm for every decrease of 20 kPa in atmospheric pressure starting from ~100 kPa, then the wind speed produced by an ionic wind thruster will remain constant” was proven incorrect. This was evident in my data as the average wind speed difference compared to the control value (across five trials) was +3.575 m/s at an electrode distance decrement of 1 cm and +0.050 m/s at an electrode distance decrement of 0.6 cm. Therefore, to most accurately answer the initial question, by what distance decrements does the electrode spacing need to be adjusted with decreasing atmospheric pressure to maintain a constant wind speed produced by an ionic wind thruster, it is evident that 0.6 cm decrements in electrode spacing for every 20 kPa decrease in atmospheric pressure will maintain a very similar wind speed compared to the control value. For example, the control wind speed was 26 m/s, and when the electrode distance decrement was 0.6 cm, the wind speed difference compared to the control value was +0.050 m/s. Although the wind speed difference is not 0.000 m/s, this is the most minimal difference out of all electrode distance decrements tested. To elaborate, although the atmospheric pressure was decreasing by 20 kPa, reducing the electrode spacing by 0.6 cm counteracted the lack of fluid particles in a set volume, allowing for an exceptionally constant wind speed to be produced. This is because setting the electrode distance decrement to 0.6 cm did not bring the electrodes close enough for electrical arcing to occur. Therefore, the electricity was fully utilized in the ionization process rather than being discharged directly. Hence, when high voltages are applied to the emitter, the amount of positively charged ions formed will be maximized because more electrons can be stripped away from their respective atoms. Next during corona discharge, the cations will be repelled by the emitter due to the same polarity and attracted to the collector which is negatively charged. However, during the Biefield-Brown effect, the ions travel toward the collector while colliding with neutral fluid molecules in the drift zone, yielding a net movement of particles toward the collector as a result of the kinetic energy transfer between ions and neutral particles. At this stage, it is crucial to reduce the electrode spacing to maintain a constant wind speed even with decreasing atmospheric pressure. This is because decreasing the atmospheric pressure reduces the air particles in a set volume, making fewer particles available for ionization during corona discharge. Thus, if the electrode spacing is decremented by 0.6 cm, the ionic wind particles will have to travel a shorter distance to the collector compared to if the electrode distance decrement was 0.4 cm or 0.2 cm. As a result, the ionic wind particles retain more momentum by the time they approach the collector, therefore, generating a higher wind speed. Consequently, if we keep reducing the electrode spacing by 0.6 cm, the wind speed will remain relatively constant, because although there are fewer air particles available for ionization (due to declining atmospheric pressure), the distance they have to travel will be minimized allowing for a higher wind speed due to more kinetic energy retention. However, it is important not to exceed the electrode distance decrement of 0.6 cm because although it may generate a higher wind speed, it can cause electric arcing even at low atmospheric pressures, leading to the decreased efficiency of ionic wind thrusters. On the other hand, if the electrode distance decrement was set below 0.6 cm, a reduced wind speed would be produced because the larger drift zone would cause the ionic wind particles to lose a major portion of their momentum by the time they reach the collector. To sum it up, if the electrode spacing in an ionic wind thruster is decremented by 0.6 cm for every 20 kPa decrease in atmospheric pressure, a relatively constant wind speed will be produced.

Extension

Applications

Aircraft Industry: Ionic wind thrusters can be used in a variety of applications with the primary being high-altitude aviation. Ionic propulsion can be revolutionary for the aircraft industry by delivering a silent and zero-combustion pollution flight experience compared to traditional systems. However, the specific data found in the experiment can be applied to the electrode spacing in all aircrafts that potentially will use ionic wind thrusters. This is because as aircrafts travel to higher altitudes, the wind speed will decrease due to lower atmospheric pressure. Hence, if we utilize the data from this experiment we can adjust the electrode spacing to ensure uniform aircraft propulsion (due to a relatively constant wind speed) even at higher altitudes with low atmospheric pressure. It is important to consider that this technology only works for high-altitude aviation and not space propulsion because outer space is a vacuum, restricting ion formation due to a lack of air particles. In conclusion, ionic wind thrusters benefit the environment due to fewer combustion emissions in comparison to traditional propulsion systems. For example, a standard Boeing 747 uses 10,668kg of fuel and emits approximately 33 tonnes of carbon dioxide to travel 530 km. This is equal to roughly 336 gas cars traveling the same distance. Furthermore, by introducing ionic wind thrusters, we can mitigate societal issues such as climate change and decreasing biodiversity. Fewer combustion emissions can actually prevent rapidly decreasing biodiversity since an improved air quality index can improve plant growth by increasing chlorophyll concentrations, which leads to more sugars (food) being produced for the plants. As a result, unbalanced food chains (less producers and more consumers) can be balanced to sustain ecosystem biodiversity. Furthermore, fewer combustion emissions can also benefit certain people in society such as seniors and young children who are more susceptible to respiratory diseases. This was evident according to Harvard University and three other British universities which claim that approximately 18% of deaths worldwide in 2018 were due to fossil fuel emissions. Hence, by implementing ionic wind thrusters in these aviation fields, we can minimize this number to lower the risk of respiratory diseases and deaths among vulnerable populations in society. Lastly, by slowing down climate change, we can help the environment and society in several ways. For example, warming temperatures can result in the acidification of water bodies as more carbon dioxide can be absorbed by the ocean. This can negatively impact aquatic environments and ecosystems such as coral reefs by causing coral bleaching. Therefore, potentially triggering a trophic cascade as all the primary consumers who rely on coral for food or security are less likely to survive. And because the primary consumers are unlikely to survive, the food source for the secondary consumers will also be depleted, and so on.

Low Altitude Satellites: Ionic wind thrusters can be suitable propulsion options for low-altitude satellites. This excludes satellites located in higher layers of the atmosphere such as the exosphere and thermosphere because there simply are not enough air particles that can undergo ionization. Therefore, the data from this experiment can be used to determine the electrode distance decrement required for a satellite to efficiently maneuver itself by generating a constant wind speed. For example, suppose the electrode spacing does not adjust accordingly as the satellite moves to a higher or lower altitude. In that case, there may be discrepancies in its positioning ability. This is because the satellite will be unable to generate the constant wind speed required for stable operation due to an abundance or lack of air particles in a set volume (varying air particle density). Finally, ionic wind thrusters can be beneficial over conventional satellite propulsion systems. This is because traditional satellites primarily rely on chemical reactions between a fuel and an oxidizer to generate thrust. However, in comparison to ionic wind thrusters, these chemical reactions often result in toxic products being released into the atmosphere, hence, damaging our environment. Furthermore, these chemical-based satellite propulsion systems are more complex due to a higher number of safety considerations linked with chemical reactants that can be potentially dangerous for the satellite and environment. While implementing ionic wind thrusters in this field can benefit the environment, it can also benefit society. This is because it can produce jobs in areas where the installation of ion propulsion systems is required. Therefore, potentially boosting the country’s economy by tackling societal issues such as severe unemployment that often leads to increasing poverty. Ionic wind thrusters are more cost-effective compared to traditional systems that carry onboard chemical propellants required for the satellite to operate. This is because not only are these chemicals expensive to produce, but they are also expensive to transport and carry in specialized containers. Lastly, by introducing ionic wind thrusters over chemical-based satellites we can benefit the environment in several ways by slowing down climate change. For example, by reducing the amount of greenhouse gases emitted into the atmosphere, we can boost the agriculture industry as fewer crops will be dehydrated or impacted by harsh environmental conditions such as droughts and extreme heat. Therefore, benefitting society by tackling economic issues such as food shortages that have led to more expensive groceries. This is because if farmers are able to grow and harvest more crops without worrying about them dehydrating, a stable food supply can be established. And a stable supply of crops equates to more stable food prices. More stable food prices make groceries more accessible and affordable to a wider range of people by easing societal issues such as inflation.

Further Areas of Study

Control System Automation: This is basically studying and developing a system that can automatically control the electrode spacing in accordance with the atmospheric pressure. For example, if we were to implement ionic wind thrusters into present low-altitude aircraft, there may be difficulties in ensuring that the electrode spacing gets adjusted precisely as per the external atmospheric pressure. If the electrode spacing is not properly adjusted on time, then it may lead to unstable operation of the ionic wind thruster as it experiences a change in altitude. Hence, we could utilize barometric instruments such as altimeters (devices that measure atmospheric pressure as altitude changes) to develop an automatic ionic wind thruster that adjusts its electrode distance by a set decrement as the atmospheric pressure changes respectively. This technology could eliminate the need for manual adjustments in the electrode distance of ionic wind thrusters in aircraft. Therefore, ultimately benefitting society by providing more cost-effective flight options. This is because, by promoting automatic electrode spacing adjustments, airlines would not need to hire specialized technicians to perform this task. Consequently, in the long term, airlines can save money on aircraft operation to reduce the cost of their flight tickets. Hence, benefitting society by making air travel more affordable and accessible to a broader range of people. 

Hall Effect Thrusters: These are similar to ionic wind thrusters, however, Hall effect thrusters use electrons captured in a magnetic field to strip away electrons from the molecules of chemical propellants such as Xenon and Krypton. This technology can be preferred over traditional propulsion systems because they reduce propellant consumption by 10 times. However, some drawbacks of Hall effect thrusters in comparison to ionic wind thrusters include the fact that they still produce chemical emissions into the atmosphere and environment. On the other hand, an advantage of Hall effect thrusters is the involvement of onboard chemicals that are ionized for propulsion. This can be beneficial because, unlike ionic wind thrusters that are unable to operate efficiently in low atmospheric pressure, Hall effect thrusters can operate for a limited time potentially in space due to their stored chemical propellants. Therefore, it would be interesting to study the wind speed produced by a Hall effect thruster and an ionic wind thruster. Additionally, it would also be interesting to examine the possibilities of combining ionic wind thrusters with Hall effect thrusters to form hybrid propulsion systems that maximize wind speed and minimize the emission of chemical pollutants into the environment and atmosphere. In summary, this propulsion combination can benefit the environment by providing efficient alternatives to high-altitude satellites and spacecrafts that rely solely on chemical propellants. This is because, ultimately, aircrafts that rely solely on chemical propellants produce excessive combustion reaction products like greenhouse gases including carbon dioxide. These gases become trapped in our atmosphere and retain heat, thus, damaging our environment by contributing to the progression of climate change. A possible way that progressing climate change can negatively impact the environment is through rapidly melting glaciers and ice caps. This can have devastating impacts on coastal ecosystems and communities through resultant floods and rising water levels. Therefore, disrupting coastal ecosystems by destroying habitats along the coastline and shallow waters, severely impacting organisms that rely on these environments for survival. Additionally, excessive water levels can affect coastal developments by damaging nearby infrastructure, ultimately, impacting homes for several individuals and families. This phenomenon can also negatively impact the municipality economically as a substantial amount of money is required to repair the damages dealt to the city’s infrastructure.

Electrode Optimization: In the future, I could focus on which electrode materials would produce the most wind speed in ionic wind thrusters. To achieve this I could evaluate which conductive materials work best for either the emitter or collector, and examine the thruster wind speed if both electrodes were composed of the same material. Furthermore, it would be useful to investigate the impact of electrode geometry on the wind speed produced by an ionic wind thruster. For example, you could vary the shape of the emitter and collector to see if there is a change in wind speed. By testing these combinations, we could optimize ionic wind thrusters to maximize the wind speed. Maximizing wind speed without triggering electrical arcing can lead to the more efficient and stable operation of ionic wind thrusters.

If I were to redo this experiment with unlimited time and resources, I would definitely test more distance decrements for more frequent reductions in atmospheric pressure. This could allow me to further reduce the current average wind speed difference of +0.050 m/s produced when the electrode distance decrement was 0.6 cm. Also, if I were to repeat this experiment, I would ensure more frequent battery changes and regular oil changes in the vacuum pump. Therefore, having a consistent voltage and more precise pressure adjustments for more accurate results. Lastly, I could improve this experiment next time by ensuring an exact alignment of the electrodes and anemometer. By having the emitter aligned directly in the center of the collector, the ions generated will experience an equal attractive force in all directions toward the collector. Therefore, a higher wind speed could be produced as minimal ions will be redirected to travel along the outside of the collector due to an asymmetrical attractive force exerted. By having the anemometer directly in the center of the collector, a more accurate wind speed measurement can be recorded. This is because the neutral particle movement along the edges of the collector could experience some turbulence due to minor imperfections and bumps in the structure. However, by placing the anemometer faced directly in the middle of the collector, we can get a precise wind speed measurement due to the uniform net movement of particles.

Electrode Alignment: Although significant effort was put into ensuring that the emitter remains at the center of the collector, it is possible that the emitter was off-center. Hence, when corona discharge occurred, it may have been more concentrated near a certain end of the electrodes that are positioned more closely. Therefore, the ions generated near the end of the emitter slightly farther from the end of the collector, may not be directed through the collector due to a weaker attractive force. Thus, some ions along with neutral fluid particles travel outside of the collector and cannot contribute to the wind speed measured by the anemometer that is placed directly in the center of the collector.

Inconsistent Voltage: As the ionic wind thruster was switched on over and over again, the primary cells in the battery pack underwent more chemical reactions resulting in the gradual decline of the reactants required for the chemical reactions to occur. Although the batteries were regularly replaced after each trial for good measure, the batteries may generate a lower voltage when the reactants that produce electricity (through chemical reactions) are almost depleted. Consequently, reduced voltage results in declined ionization around the emitter due to a weaker electric field causing a fewer number of electrons to be stripped away from their respective atoms. Therefore, a smaller number of ions equates to fewer ion-neutral fluid particle collisions, and for this reason, a weaker overall ionic wind is produced.

Vacuum Chamber Inaccuracies: The vacuum chamber could have occasionally malfunctioned due to dust particles introduced in the vacuum pump oil, decreasing the overall efficiency. Additionally, the lid could have some potential minor gaps in the seal, allowing air to enter and escape the chamber. These reasons could contribute to errors involving the wrong amount of air particles being displaced from the chamber. This is an issue because if more air particles are left in the chamber, more ions will be produced, and consequently more collisions between ions and neutral fluid particles will occur. Therefore, yielding a stronger-than-expected net movement of particles toward the collector (stronger ionic wind). However, if a significant amount of air particles are displaced from the chamber than expected, fewer ions will be produced, and as a result, fewer collisions between ions and neutral fluid particles will occur. Therefore, yielding a weaker-than-expected overall movement of particles toward the collector (weaker ionic wind).

References

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Chu, J. (2013, April 3). A mighty wind. MIT News. Retrieved August 5, 2024, from https://news.mit.edu/2013/ionic-thrusters-0403

Claiborne, M. (n.d.). How Does an Altimeter Work & How To Read Altitude. Aero Corner. Retrieved December 12, 2024, from https://aerocorner.com/blog/how-altimeter-works/

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Firstly, I would like to acknowledge my parents for their unwavering support throughout the project. They provided me with valuable guidance and suggested contacts for experts in my project’s field. My parents also funded all of my testing and material costs which I am highly thankful for.

Next, I would like to acknowledge Mr. Kevin van Gisbergen, an experienced and professional pilot, for his incredible help with this project. He provided excellent information and insight on the limitations of ionic wind thrusters, and how they could be integrated into the aircraft industry. 

I would like to acknowledge Mr. Aum Trivedi, an expert in the field of cosmology, for providing useful information and guidance whenever I needed it. He helped by elaborately explaining project-related concepts and clarifying information whenever needed.

Last but not least, I would like to acknowledge my science teacher Mr. Ian Stone, and science fair coordinator, Ms. Karen Davis. They have guided me through the science fair process and supported me whenever I had questions. Ms. Davis also helped by suggesting contacts of experts in my project’s field.