Testing on the ground removes all the characteristics of space that make eddy-currents and other exotic actuators useful there. Specifically, friction (with air or a surface) often overwhelms the small forces of spacecraft actuators that aren’t rocket powered. So, low friction test beds are necessary to experimentally verify things meant to move in space.
Several versions of low-friction test beds are available for spacecraft research, each with their own advantages and disadvantages. The two most common types are air-bearing test beds and rotational test beds. They have a number of advantages. However, unnecessary degrees of freedom, cost, complication and lack of extensibility motivated the construction of a 1-DOF air-track test bed.
Air-bearing test beds have simulated microgravity dynamics, both translational and rotational, for over 45 years. Traditional planar air bearing systems are ideal for testing 2-DOF dynamics, but have a number of drawbacks that make them unattractive for testing 1-DOF systems like early-stage eddy-current actuators. The second degree of freedom introduces extraneous variables when testing 1-DOF systems. Sensing the state of the 2-DOF system in real-time requires video processing software that is either custom built or expensive. Closed loop control requires on-board computing, adding to the complication of the system. Planar air bearings require extremely flat surfaces and rapidly consume compressed gas canisters.
2-D air-bearing test bed. Picture courtesy of The University of Surrey
Rotational test-beds can also simulate 1-DOF microgravity dynamics. These test-beds consist of a target on the end of a long arm attached to a low-friction rotational axis. The throw over which they can approximate linear translation is limited by the length of the arm. The bearings holding the rotational axis experience more off-axis torque as the arm length increases so the friction will increase with the throw of the system.
A rotational test bed. Picture courtesy of the University of Michigan.
Today I inadvertently ran a human toxicity trial with N = 1 data points. I’m calling it ‘the effects of way too much black pepper on human physiology.’ The conclusion is that you should ALWAYS make sure you have the side of the the pepper container with many little holes, rather than one big hole open. If you’ve ever wondered what happens if you eat several tablespoons of cracked black pepper in more detail, read on.
There’s a reason it looks like the Death Star
I ate the pepper around 8:45 pm and noticed nothing before going to bed. However, I woke up the next morning around 7:00 am and thought ‘weird, it feels like my face is on fire.’ The effect was similar to eating something extremely spicy – you feel hot and flushed, sensitivity in the back of your throat, and nothing tastes quite right. Except it has lasted all day (due, I’m guessing to the time-release effects of digestion.)
The heat in my face seemed to come straight from my extremities, which alternated between weirdly numb and just uncomfortably cold. My eyes felt like they do when you’ve had them open underwater far too long. I think the pepper actually acted as a stimulant, because it affected me very similarly to a strong stimulant (even before I had coffee) – giving me tons of energy when I started moving, followed by a spiraling crash.
That being said, the symptoms died down over the past 15 hours, so I assume there are no lasting effects.
I thought this would be worthwhile to write up because a search for ‘black pepper overdose,’ ‘black pepper side effects,’ and ‘black pepper toxicity’ yielded nothing useful. Also as a warning: if you accidentally dump a massive amount of pepper on your dinner, throw it away. It isn’t worth it.
As you may have figured out, I’ve been trying to put up a weekly blog post on our lab website. This week I talk about how you can create your own nifty eddy-current demonstration for about $20. Check it out!