The aim of this experiment was to design an efficient lifter which could carry an extra payload of 100 g. My Spiral Hex lifter V3.0 was designed for this target payload. This EHD thruster has been designed using my own excel worksheet, as shown below.
The equipment was setup for the test as shown below. From left to right you can see the hv probe, 1 kWatt power supply, dc supply for hv supply electronics, multimeter connected to hv probe, and oscilloscope connected to hv probe.
The first video shows the tethered lifter with no load. The power supply is remotely operated by my infra red remote control. Each time that a channel (out of 10) is enabled, both power and mean voltage increase at the output. If you keep an eye on the small oscilloscope trace, you might be able to follow the channel switching at the hv output. The oscilloscope probe is connected to my hv probe output.
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As you can see, with just one channel at 30 kV, the 85 g lifter starts to float around. With 2 channels, voltage rises up to a mean value of about 36 kV, at which the lifter thrust increases for stable flight and some additional payload.Lifter with 100g of payload
Here the lifter is now loaded with 102 g payload in the form of stainless steel nuts (total thrust= 85 gF + 102 gF), distrubuted evenly at each lower vertice balsa rod. Sorry, my webcam has no zoom to get a close up of the payloads in flight, but I am sure you will notice the effort the lifter is doing from the video.
As you can see, 7 channels were required to achieve stable flight with the external 100 g payload. Voltage reached at the output at this point was 46 kV.
|Channels||Mean Voltage||Mean Current||Power supplied|
|1||31 kV||1.9 mA||58.9 Watts|
|2||36 kV||2.6 mA||93.6 Watts|
|3||38 kV||3 mA||114 Watts|
|4||40 kV||3.8 mA||152 Watts|
|5||42 kV||4.0 mA||168 Watts|
|6||44 kV||4.2 mA||184.8 Watts|
|7||46 kV||4.4 mA||202 Watts|
The above are the readings obtained during the experiment. Note, that although 7 channels had to be switched on to lift the 100 g payload, it does not mean that the lifter requires (7 x 100 Watt/channel) 700 Watts. In fact the total power supplied is only 202 Watts, as calculated on my worksheet. However, since every channel helps to increase the maximum mean voltage across the thruster, 7 channels were still required to achieve this. The total thrust efficiency of this lifter exceeds 0.9 gram force per Watt, at approximately 1 gram force/Watt. This means that with a 1 KWatt power supply operating at 46kV, we can power up to 5 such thrusters, reaching a thrust value of (1 kg force) 10 Newtons!