16 Dec
16Dec

I was halfway through the first draft of Spacewalker when I realized I was drowning under the weight of my own ignorance. I needed a mission concept--how big was Aspire, what did it need to do, where was it going, and when will it get there? It wasn't enough to pants my way into snap selections. I wanted these decisions to synergize, complement one another, and have some basis in scientific reality.

The arbitrary...

Let's start with an artistic baseline of unconstrained elements. Before I ever put pen to paper, these were ideas already floating around in my brain that I thought would make for a cool story.

Timeframe. I love the promise and potential of a near-future story. It has to be near-enough that I can imagine possibly seeing it in my lifetime, but far enough away that there's a freedom to tell a story untethered from today's most obvious problems. So, no COVID pandemics or presidential elections here. I targeted a story in the 2040s-2060s.

What about the mission duration? 14-20 years round trip, long enough to have a substantial impact on the main character when he wakes up missing his memories. Of course, such a long duration requires a suitably remote final destination... 

So Aspire's mission is to visit Neptune's L5 Lagrange point, on the edge of the solar system. This is a nice, remote location that, in real life, humanity has yet to probe or explore. So I can populate it with whatever I'd like for story purposes--in this case, the stability of Lagrange point makes a nice place for someone to leave something behind to be discovered. 

And on the way to Neptune's orbit, the ship flies by Jupiter for gravity assist maneuver. I'll admit this was an extra arbitrary decision (as my struggles with the math will eventually show), but I wanted a contrasting setting and a notable checkpoint in the mission design which could serve as a "ticking clock" hanging over the crew early in the story. Also, Jupiter's radiation is a great excuse for the potential failures plaguing Aspire at the beginning of the story. Also, Jupiter is cool.

How about the size of the crew? When I began my brainstorm, I had already sketched out six characters and I knew roughly their role in the story. But I opted for eight total crew even though I didn't have a precise plan for what to do with those other two characters. Not very compelling, I know. And it kind of showed in my first draft, when they didn't even get the chance to wake up and interact with the rest of the crew until the second half!

Finally, to support a crew of this size on such a long duration mission, I needed to supply a spacecraft with all of the essentials. Food, water, life support, cryogenic sleep pods, and enough room for eight people to coexist at a time. I was keen on incorporating a spinning ring to provide artificial gravity to offset the dreadful side effects of low/no gravity. More on this in the future!

...drives the necessary

With all those arbitrary (ahem, authorial) decisions out of the way, let's plan a space mission! We need...

  1. To pick departure dates, arrival dates, and calculate the required delta-velocity (thrust) required over the course of the mission
  2. Estimate the spacecraft mass, so that...
  3. We can size an engine and power plant to provide enough delta-V to propel our ship to the edge of the solar system
  4. But with a ship this size, and a significant power plant, we'll need a sizable thermal system to reject excess heat...

And more. 

In some future posts, I'll talk about some of these. And I'll share the numbers--most of which didn't make it into the manuscript. I relied on qualitative descriptions or analogies where possible, rather than waxing philosophical about thruster performance. But knowing that I was still working within the realm of the plausible mattered to me and gave me the conceptual backbone I needed to write my earliest drafts.

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