Wednesday, April 05, 2017

Sailing Venus: Riding the wave

Which way is up? That's a question I've struggled with a lot lately in relation to Venus. Here's the thing: Sailing Venus is, at its heart, an adventure story, but it's also a hard science fiction story as well. It's not hard SF in the sense that characters have rivets sticking out of their heads and speak in equations, but one where I try to get facts and details as correct as possible. I'm not writing about Venus' dinosaur-infested swamps, after all.

But you know what? As I get deeper into the story, something started going wonky. Venus is a weird world. It's a terrestrial planet like Earth, almost exactly the same size, but it has almost no water, is hotter than a pizza oven on the surface and its upper atmosphere whips around it in a superrotation that circumnavigates the planet every four Earth days (that's really, really fast). Venus has a day (243 Earth days) that is longer than it's year (225 Earth days), and also has a retrograde rotation, meaning the sun rises in the West and sets in the East. One would think that's pretty cut and dried, but it's not. Some Venus researchers don't view Venus as having a retrograde rotation, instead, consider it as flipped, with its north pole pointing "down" when viewed from the plane of the solar system, and a south pole pointing up. This nomenclature doesn't matter to me one iota, except that some websites and books present maps of Venus with one orientation, and others flip it. Clearly these are different schools of thought on which is the proper way to present Venus "right side up," but the trouble is, in most cases, they don't clearly identify which school of thought they subscribe to. So this is my dilemma--if I erroneously choose a "north is down" map, which has been flipped "right side up" so that Venus rotates in a counter-clockwise direction like all the other planets, the westward-blowing superrotation would be going backwards. Not only would that make me look stupid, it completely alters which locations are accessible to my protagonist--indeed, it profoundly affects the plot and even location of the various outposts on the planet. That's not something I can really fudge--which direction a continuous, 200 mph wind blows. To make matters even worse, several online science sites that claimed to set the record straight on this bit of befuddlement contradicted each other. Yeah, I could've emailed some NASA researchers, but I don't like to bother them unless absolutely necessary. And certainly not with a question as mind-numbingly stupid as this one. Fortunately, I stumbled across this graphic:

Is that not a thing of beauty? This is data from the Japanese space probe Akatsuki, super-imposed over a flattened map of the planet's entire surface. The colored elements of the image are infrared and ultraviolet renderings of a huge standing wave over the western portion of Aphrodite Terra. Not only does it clearly show the direction of the superrotation, it also specifically locates, geographically speaking, a significant atmospheric phenomenon that I'm going to put to good use in the narrative. So, yay!

But the hassle with "Which way is up?" got me to more closely examine other numbers floating around in my story. Most books and fact sheets about Venus list the extremes of the planet--highest pressure, fastest wind speed, highest temperature, etc. And it dawned on me that while I was using these numbers in my novel--accurate though they may be--they're not constant across the planet. Each changes with altitude, sometimes significantly. Venus' much-discussed superrotation? The top wind speed is roughly 223 mph around 45 miles up, but a little further down, around 33 miles up, it slows to about 150 mph. That's a big difference. Temperature's another biggie. The surface of Venus is hot enough to melt lead, and 29 miles up, it's still a blistering 197 degrees Fahrenheit. But jump to 35 miles up, and the temperature dips to 46F--enough to start worrying about hypothermia at those wind speeds. That is, were someone to be exposed to those conditions. Which nobody ever would be, certainly not in my book, right? From there I made the leap to realizing terminal velocity would be different on Venus as well. How different? Well, Venus' gravity is very close to that of Earth's, but the atmosphere, made up mostly of CO2, is very different. I thought the atmospheric pressure would have a big impact on terminal velocity, but it turns out that's not true. Pressure has no bearing, but density does. Those are distinct things. Researching density led me to individual gas constants, and from there back to drag coefficients. The irony is that I'm terrible at math, while my main character, Erica, is a whiz. I'm having to make my way very slowly and cautiously through these equations, which she could solve in her head.

And you know what? Ultimately, none of this will show up in the book. Oh, it'll be there, behind the scenes, informing what goes where and how this does that. But strictly as scaffolding and superstructure. I'm not stopping the narrative to deliver a physics lesson or print out some algebraic equations for readers to solve along at home. That's generally referred to as "I've suffered for my art, and now it's your turn" syndrome. No, I'm suffering for my art so you don't have to. Rest assured, though, that no matter how fantastical Erica's adventure may get, I've made a good-faith effort to ground it in reality.

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  1. Personally - I'd just go back and stick with the dinosaur-infested Venus.

    1. Yeah, but that's not this story. Alas...