Like I mentioned in previous posts, this semester I’m in a senior design class where you design, build, and test an experiment. It’s been almost 2 months and boy do we have a lot to show for our efforts!
First off, a little science background. Basically, with radiometric thrust, there exists a thermally conductive material that is dark on one side and white on the other. When a light source is shone on the dark side of the material in a near vacuum, the temperature difference between the black and white side of the vane (thermal gradient) causes the gas around the dark face to move away from the heated dark surface and causes a net force on the vane in the direction of the white side of the vane. This overall net force is a summation of three main forces in play: the pressure (aka area) force, the edge force, and the shear force. The pressure and edge forces are the two main drivers of thrust generation while the shear force is the main source of hindrance to the net force.
To maximize the thrust (by maximizing the pressure and edge force while reducing the shear force), several things can be controlled including vane thickness, thermal gradient between the two faces, and the pressure of the gas around the vane. In my group’s experiment, we determined the vane thickness and thermal gradient to test at based on previous experimental results. So, in our experiment, we are varying the pressure of the surrounding environment around the vanes at different vane configurations to see which combination gives us the most thrust. So yea, that’s the basic technical gist of it. Now, the fun stuff: pictures!
Here is an example of one of our vanes that we made. It has an aluminum front, a balsa wood insulator to increase the thermal gradient, and an aluminum backing for ease of mounting:
Then there’s the base plate and blocks too which the vanes get mounted too:
And then here is what the assembly will look like: