Iceland is a Weird Place

If you were to ask an Icelandic sheep farmer freezing in his longhouse 500 years ago: “hey, will those rainy mountains and geysers make your descendants wealthy?” he would have said “you’re crazy. sheep and fish are natural resources, rainy mountains just get in the way.” 

Fast forward 500 years. Those rainy mountains provide tons of fast-flowing water, which can be turned into something the sheep farmer couldn’t even imagine – cheap electricity. This electricity can be used to smelt something else the sheep farmer didn’t know existed – pure aluminum. This aluminum is valuable because it enables thousands of technologies that – you guessed it – the sheep farmer could barely have imagined.  

With this story and many, many like it, I always find it surprising that many people still say “yes, well NOW we know what the limits are and should really slow down.” 

Inspired by: Planet Money Podcast - “A City on the Moon”

Counterarguments Include: Ah, but now we have science that tells us the value of all resources. 

Learn more: Julian Simon wikipedia. Julian Simon Econtalk. Julian Simon Planet Money. Aluminum. 

 

Why are Rockets like Amphorae? Pt 1.

Short answer: They’re both technological local maxima.

“whoo hoo, I’m a local maxima!”

Long answer:

If asked “what container do you use to ship large volumes of wine?” the answer is  pretty clearly “the barrel, duh.” But if you asked that question two thousand years ago, it would be “amphorae, duh. Barrels are expensive, tiny, shoddy containers made by barbarians.”

(ASIDE) Amphorae were the dominant vessel for liquid transport in the mediterranean world for centuries. You probably think of amphorae as little urns that look something like this:

Achilles (left) is a metaphor for barrels in a historical context

But that will be like someone a thousand years from now thinking of a custom Porsche when someone says “car”: they’re both high-end luxury goods. Instead of being painted with Greek men killing each other, most amphorae were several feet long and looked something like this:

Transport Amphora

Today, it’s clear that barrels have many advantages over amphorae: they’re lighter, less fragile, and don’t need special racks to hold them during transport. So why were they ever chosen over barrels? Historical momentum and initial conditions.

Amphorae were developed in tandem with Mediterranean trade – amphorae enabled trade in valuable liquids and in turn, increased trade incentivized innovations in amphora technology. All of this occurred around the Southeastern Mediterranean (present-day Egypt, Greece, Lebanon etc.) Here, wood was relatively scarce and expensive. What was cheap and plentiful? Rich river mud. What’s made out of mud? Amphorae. As trade expanded from this region into the rest of Europe, so too did the practice of using amphorae to transport liquids. Archeologists have found amphorae in Britain and Northern France, where wood is far more plentiful, so it would have been easy to use barrels instead.

So why didn’t barrels begin to dominate trade as soon as heavily wooded regions connected to the trade routes? The same reason we’re still using rockets to transport everything to space: Historical momentum. What did it take to shift the balance from amphorae to barrels? Something that hasn’t happened yet to space technology: a massive shock.

To come, in no particular order: Werner Von Braun, Muslim Invasions, and space cannons.

 

Spinning > Not Spinning

The changing component of the magnetic fields that produce eddy currents can come from two sources: a relative velocity between the field and the target or change in the strength of the field itself. For a number of reasons the bulk of EC actuation research has focused on the latter mechanism. Time-varying electromagnets are easier to both analyze and implement.

However, two motors spinning magnets to create eddy-currents through moving magnetic fields may be able to achieve something that is much harder with electromagnets: attraction AND repulsion without a complicated scheme.

The motor-magnet actuator says to the plate: “come here”

“Now go away”

Combine that with “sashay left and right”

And you just may be able to dance with a spaceship.

Sliding into testing

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.

Don’t Try This at Home

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.

Black Pepper Kernel

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.