First there's the matter of fuel. We're told in the entry for day 12150 that 3/5 of the original fuel load is left at the end of the acceleration phase. Really? The payload during the acceleration phase is both the manned ship and the fuel required for the deceleration phase. It will take far more fuel during the acceleration phase than is needed during deceleration, so how can 3/5 be remaining? How bad is it? During the deceleration phase, even if the period were only twenty years at an average of 1/2 g, and even if we assume a photon rocket rather than the fusion engine mentioned in the story, the mass of fuel would be tens of thousands of times the mass of the manned ship. During acceleration, the mass of fuel required would be hundreds of millions times the mass of the final payload (at least). The described structure of the ship can't work.
Then there are the matters of time and distance. We also learn in the entry for day 12150 that the ship only reaches a fraction of the speed of light. In a relativistic universe that's always true, but the implication is that it's a small fraction. That won't be so. If Newton ruled, an acceleration of one g would get you to light speed in a bit under one year. He doesn't, of course, but you still reach a healthy fraction of light speed at 1/2 g for even one year. Accelerate for as long as thirty years (ship time!) at 1/2 g and you'll be close to light speed (relative to Earth), the time dilation factor will be huge, and the distance covered in the Earth frame of reference will be many orders of magnitude greater than the distance to Delta Pavonis, the end point of the story's journey (a bit under twenty light years away).
To be up to Analog standards, the story just needs a little work. Dramatically reduce the acceleration so that the speed remains non-relativistic and the journey actually takes the eighty years indicated in the story. Calculate the actual required fuel load, and propose an acceleration curve that works. For starters, it might be well to assume a constant thrust engine with acceleration at any time determined by the current total mass (ship and fuel). Will it be necessary to throttle the engine back near the end of the journey? What is optimum in terms of total fuel requirements and trip time?
On the medical side, I'd have to ask why they didn't put the entire crew to sleep for a year or two back on Earth (using Earth facilities) just to make sure that everyone could tolerate it. However, that would be another letter.
Steve Gray Orlando, FL
The author responds:
Steve Gray is correct to complain that my math in "Life Flight" was not precise. As a devotee (and collaborator) of Larry Niven, I take my "hard" science fiction very seriously. Still, even Larry himself was not perfect. There's a filk song about Larry's most famous example: oh, the Ringworld is unstable, the Ringworld is unstable, did the best that he was able, and that's good enough for me!
For my short works, I usually don't invest the kind of calculating time one might log on a full novel. And if ever I do novelize "Life Flight" I will absolutely be taking Steve's notes and using them to refine the specifics of the Osprey's journey. Just as Larry used criticism of the first Ringworld novel to greatly inform the descriptions and events of the second, to that franchise's credit. Steve, if the novelization does reach fruition, you can expect a nice credit for having done my homework for me.
For "Life Flight" the novelette, I was satisfied with what I call back-of-the-creative-envelope educated guesses. These are reasonably informed by the realities of the physics in question, without dwelling so much on the physics that the human aspect of the story gets swamped by the equations.
I imagined the Osprey as a thick, super-skyscraper-sized fuel tank filled with slush hydrogen isotope. The crew module is a very long, insulated, relatively thin cylinder running centerline through the slush. At one end of the Osprey is the bow shield, to protect against induced cosmic rays and other interstellar debris. At the other end is a pusher/shield plate punctured by the exhaust nozzle of a supremely efficient, yet necessarily very-low-thrust fusion drive. A drive that consumes reaction mass and reactor fuel at an amazingly miserly rate. So, it takes a long time for such a drive to push the Osprey up the relative acceleration curve, and then brake accordingly on the other end of the journey. How long—precisely?—was something I didn't feel the story needed to worry about. Nor did I factor in total time spent at one g, in a per-second-per-second cumulative sense. Just that the ship would never, ever come close to reaching truly relativistic speeds.
Again, all back-of-the-creative-envelope guesswork. Sorry if the way I described the action rang too many physics alarm bells, for those with better arithmetic skills than myself.
Hopefully Steve (and anyone else who noticed my imprecision) will forgive me.
Now, to the instability syndrome that keeps our hero from being able to sleep out the trip to his new world.
For this plot point, I made a single, key assumption: even well-funded, highly engineered operations sometimes can't plan for all possible contingencies.
In the body of the story I dropped the hint that the syndrome is fantastically rare and cannot reasonably be tested for. Why not? Well, maybe it takes different lengths of time for the problem to manifest in different people? Time the pre-mission planners didn't have? Or maybe the testing is prohibitively expensive? So much so that it wasn't in the mission budget? Or maybe medical science assumes that if the parents don't have it, their kids won't either? But the science got it wrong in our hero's case? Or maybe our hero just didn't have the problem when he boarded, but later grew into the problem post-puberty? I left it as a mental puzzle for readers to invent (using their own imaginations) why this problem would have gone unchecked before the Osprey's launch.
As with the math surrounding the Osprey's journey, I didn't dwell so much on the technical details of the instability syndrome so much as I dwelt on its human impact: the way such a discovery would virtually destroy a young man, and condemn him to a life not of his own choosing. How would any of us, faced with such a thing, react? What might our choices entail? How would we derive meaning from living out our days on a ship in a proverbial bottle? I found these questions much more engaging than the actual question of why the syndrome went undetected. And again, I hope Steve (and anyone else who wrinkled his or her brow at the issue) will forgive me.
Cheers, Analog! I look forward to seeing you all next time. And thank you for being the sharpest SF readers in the literary quadrant!
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UPCOMING EVENTS
Anthony Lewis | 331 words
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22–24 August 2014
SHAMROKON/EUROCON 2014 (European continental SF conference) at Dublin, Ireland. Guests of Honor: Jim Fitzpatrick, Seanan McGuire, Andrzej Sapkowski, Ylva Spångberg. Memberships: USD50, USD15 (under 21), concessionary USD35 (students, pensioners, etc); Supporting: USD15. Info:
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26–28 September 2014
SCI-CON TAMPA (Media-oriented SF conference) at Grand Hyatt Tampa Bay. Guests: Richard Hatch (BSG), Jack Stauffer (BSG), Nicki Clyne (BSG), Aron Eisenberg (ST:DS9), Dr. Story Musgrave (astronaut). Membership: $45 (adult) until 19 September, $50 at the door; $30 (age 11–15) until 19 September; kids-in-tow free. Info: http://scicontampa.com/.
3–5 October 2014
CONTRAFLOW IV (New Orleans area SF conference) at New Orleans Airport Hilton. Writer Guest of Honor: Gregory Benford; Fan Guest of Honor: Cherie Cerio. Membership: $40 (adult) until 31 August, $45 at the door; $10 (ages 8–19) until 31 August, $20 at the door; kids-in-tow free (ages 7 and under). Info: http://contraflowscifi.org/;[email protected]; Box 57927, New Orleans, LA 70157-7927.
19–23 August 2015
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