Cryogenic Sleep 2

Once I decided cryogenic sleep was a plausible enough technology to use in Spacewalker, I needed to work out the So What of the technology. It’s a nice way to skip years of boring travel, but what effect does it have on the characters? I focused on three specific factors. 

• Change in perceived age. I wasn’t interested in aging up my characters seven years over the story. Instead, I decided that cryogenic sleep slows the metabolism to 25% of usual. So, by the end of the story, the characters only look 1.75 years older.
• Hair and Beard growth. Human hair for both hair and beards grows about 6 inches (~15 cm) per year. When applying my slow metabolism rule, that reduces down to 1.5 inches (~3.75 cm) per year.
• Fingernail growth. Human fingernails grow about 0.1 millimeters per day or 3.6 cm per year (~1.4 inches). Again, applying the slow metabolism rule, this reduces down to 0.9 cm or 0.35 inches.

 With rules and rates in place, it was a matter of simple math to figure out the rest. When the characters wake up at Jupiter after 2 years in cryogenic sleep… 

• Their perceived age is about 6 months older.
• Their hair is 3 inches longer.
• Their fingernails are over half an inch longer.

 And again, when the characters wake up at Neptune’s L5 Lagrange Point 5 years later… 

• Their perceived age is about a year and a couple months older.
• Their hair is over seven inches longer. Assuming they didn’t run into an orbital barbershop at Jupiter, that’s nearly a foot of growth since they departed Earth.
• Their fingernails are nearly two inches long. Yuck.

 As it goes for most of my story-relevant calculations, I wanted a quantitative understanding of the problem before I wrote about it qualitatively. Here’s the final representation of all those numbers once Edred wakes at Neptune. 

Mirela still lay in the adjacent cryopod. Maybe she dreamed of the Ancestor Star and how it might transform Earth. It must, to justify the atrocities foundational to their mission. The Seekers and Tribunes traded crimes back and forth to bend the world toward their competing visions of the future. Aspire, and by extension its crew, was little more than a chess piece in a much larger game—blood and metal to feed someone else’s altar of progress. 

Unless they flipped over the table. 

He freshened up. The man in the mirror was an unrecognizable caveman draped in a shaggy mane and unkempt beard. Edred’s laughter at the sight echoed through the empty corridors. He clipped off grotesquely long fingernails, cropped the beard to hug his cheeks, and found a tie to contain most of his hair that now brushed his shoulders. His skin was fully healed, though patchy and pink in places. For all the physical changes, his tired, brown eyes looked about the same. Five years had passed, but cryosleep slowed the metabolism considerably.

Writing a story is quite the opposite of engineering. No one needs to see my math!