Rocky's Voyage — After Project Hail Mary
EP.05 — Grace's Equation
그레이스의 방정식
"Grace saved me.
This time, I go."
SCENE 01
Runaway
The first experiment nearly destroyed everything.
After finding Grace's key hypothesis — that Astrophage energy release is a feedback mechanism responding to ambient luminosity — the three species spent three weeks on joint research. The theory was elegant: adjust the luminosity threshold of Tauian-made reverse Astrophage, and you can control energy emission.
Nikky produced the first sample with a molecularly adjusted threshold. A small, safe amount. A prototype.
The prototype went runaway.
Nikky
♫♪♩♫♪♩♫♪♩
"Energy release surging! Twelve times predicted value! Threshold setting was wrong!"
Only the small quantity saved them, but the Eridian pressurized chamber's outer wall hit 340°C — beyond the Eridian survivable limit of 280°C. Nikky's left-side exoskeleton suffered heat damage. The equivalent of second-degree burns in human terms.
The problem was more complex than anyone realized. Not just luminosity, but the rate of change of luminosity was also a variable. Two variables to control simultaneously. Get one right, the other goes wrong.
Captain Shin
"This is a PID controller problem, isn't it? Proportional-Integral-Derivative control. The most basic feedback control method in engineering."
Rocky's entire exoskeleton resonated. An engineer's resonance.
Rocky
♫♩♪♫♩♪♫♩♪♫♩♪♫♩♪♫
"Correct. Correct correct correct. PID. Proportional term is luminosity absolute value. Derivative term is luminosity rate of change. Integral term is cumulative deviation correction. Must encode this into molecular structure. Nikky, possible. Question."
· · ·
SCENE 02
Rocky's Limit
During the second prototype build, Rocky collapsed.
72 consecutive hours of work. System design and Tauian communication simultaneously, skipping meals. His old body gave out — all five legs locking simultaneously.
When Rocky regained consciousness, four hours had passed. Tikky was beside him.
Tikky
♩♫♪♩♫♪♩♫♪♩
"Measured Rocky's exoskeleton hardening. Joint wear rate increased 300% compared to six months ago. At this rate — cannot be certain Rocky survives the return voyage to Erid."
Rocky
♫♩♪♫
"I know."
Tikky
♪♩♫
"Knew and still worked 72 hours straight. Question."
Rocky
♫♩♫♩♫♩
"Because no time."
Grace would have said: "Rocky, you can't solve anything if you're dead. Rest."
...Fair point.
· · ·
SCENE 03
Stellar Thermostat
Three months. Seven failures. Three additional heat-damage scars on Nikky's exoskeleton. Dr. Hassan's spacesuit cooling system hit its limit twice. One Tauian scientist's crystalline surface partially opacified from energy overexposure — partial blindness by Tauian standards.
But they did it.
PID control logic encoded into reverse Astrophage at the molecular level. Three reaction pathways — proportional, integral, derivative — operating automatically. When ambient luminosity changes, reverse Astrophage self-adjusts emission. Positive feedback converted to negative feedback.
Stellar thermostat. Rocky's name for it.
Tau Ceti prototype test: luminosity fluctuations stabilized within 72 hours. Amplitude reduced 95%.
Time to go home. Each species to save their own star.
A Tauian handed Rocky a small crystal. Light patterns fixed inside.
Rocky
♫ ... ♪ ... ♫
"...Good word."
· · ·
SCENE 04
The Stopped Star
Three ships departed Tau Ceti. Second Chance toward the Sun. Hail Rocky toward 40 Eridani.
Day 7 after departure. Rocky was monitoring the Second Chance's thrust signature. A habit inherited from Grace.
The thrust signature vanished.
Kokky
♪♫♩♪♫♩♪♫
"...Confirmed. No thrust signature. Second Chance engine appears to have stopped."
Engine shutdown in interstellar space. Drifting on inertia. No deceleration. No course changes. Even upon reaching the solar system — no way to stop. Pass right through at percent-of-lightspeed.
Death.
The radio response from Captain Shin was urgent.
Captain Shin (radio)
"Rocky! Contamination in our Astrophage fuel tank. The reverse Astrophage sample from Tau Ceti e — containment breached, it leaked into the fuel tank. Fuel Astrophage and reverse Astrophage mixing, energy canceling out. Fuel reserves dropping fast. Cannot restart engine!"
Grace did not regret it. "No regrets," he said. I know. I know from 40 years of daily heartbeat patterns.
The choice is already made. Was always made. From the beginning.
Rocky
♫♩♪♫♩♪♫♩♪♫
"Kokky. Nikky. Tikky. Orders."
Rocky
♫♩♪♫♩♪♫♩♪♫♩♪♫♩♪♫
"Separating the Hail Rocky. Main hull — you three take it to Erid. Reverse Astrophage samples, stellar thermostat blueprints, all data. Saving Erid is first priority. Tikky takes command."
Tikky
♩♫♪♩♫
"Rocky is. Question."
Rocky
♫♩♪♫♩♪♫♩
"I take the auxiliary shuttle to Second Chance. Fix the fuel contamination, repair the engine. I am engineer. This is engineer's job."
Tikky
♩♫♪♩♫♪♩♫♪♩♫
"I will go instead. Younger than Rocky. Better engineer than Rocky. Rocky said so."
Rocky
♫♩♫♩♫♩♫♩
"Tikky. You must go to Erid. Erid needs you. Needs an engineer to deploy the stellar thermostat. And —"
Rocky
♫ ♩ ♫
"Second Chance has a 1-atmosphere zone. I know how to communicate with humans through a bulkhead. 40 years experience. This is something Tikky cannot do."
Tikky was silent for a long time. Silence between engineers. Then acceptance.
Tikky
♩ ... ♩
"...Understood."
· · ·
SCENE 05
This Time, I Go
The Hail Rocky split. Main hull toward 40 Eridani with Kokky, Nikky, Tikky. Auxiliary shuttle — Rocky alone — turned around. Toward the Second Chance.
Tikky (comms)
♩♫♪♩♫♪♩♫
"Rocky. Will wait on Erid."
Rocky
♫♩♫
"Do not wait. Deploy thermostat first. Erid first. My return is second."
Tikky (comms)
♩♫♪♩
"Rocky. Can you return. Question."
Rocky
♫ ♩ ♫
"Probability is not zero."
48 hours later, Rocky reached the Second Chance. Drifting on inertia. Engine silent.
He docked. Through the bulkhead — six heartbeats. All alive.
Captain Shin
"Rocky?! Why — how are you here —"
Rocky
♫♩♪♫♩♪♫
"Detected engine failure. Came to fix. I am engineer."
Rocky worked. 18 hours. Isolated the contaminated tank. Transplanted clean Astrophage from his shuttle. Neutralized residual reverse Astrophage. His old exoskeleton screamed. Three legs intermittently locking. But Rocky did not stop.
Rocky
♫♩♪♫
"Start engine."
The Second Chance's engine fired. Astrophage reaction. Thrust. Life.
Captain Shin
"...It works. Rocky, it works!"
· · ·
EPILOGUE
Is Problem. Solve.
Captain Shin proposed it.
Captain Shin
"Rocky. Come aboard the Second Chance. Come with us to Earth. Whether we can send you back to Erid from there — I can't promise. But it's better than drifting alone in interstellar space."
Rocky
♫♩♪♫♩♪♫
"Good. Go to Earth. Grace's planet. Where Grace was born."
The Second Chance resumed acceleration. Toward the Sun. Carrying Rocky.
Toward 40 Eridani, the Hail Rocky flew on. Tikky, Kokky, Nikky aboard. Stellar thermostat loaded.
On Tau Ceti e, the Tauians were stabilizing their own star.
Captain Shin told Rocky what she'd found in Grace's diary.
"If Rocky is reading this diary —
Rocky, you're the best thing that ever happened to me.
Thank you."
— Ryland Grace
Rocky stood there for a long time.
You were the best thing that ever happened to me, too.
I am going to your planet now. Where you were born. Where you looked up at the sky. Through a 29-atmosphere bulkhead, but I will feel that sky too.
There was a problem. Solved it. More problems will come. Will solve those too.
The way you taught me.
Is problem. Solve.
The Second Chance accelerated. Toward the Sun. Toward Earth.
Three civilizations. Three stars. Three languages. One science. One legacy.
Ryland Grace. Earth's scientist. Erid's teacher. Rocky's friend.
His equation was saving three stars.
⟡
— End —
In the original Project Hail Mary, Grace sacrificed his return to Earth to save Rocky. In this story, Rocky sacrifices his return to Erid to save Grace's people. Friendship, perhaps, is exactly that.
All Episodes:
EP.01 The Last Lesson
EP.02 The Hail Rocky
EP.03 Arrival at Tau Ceti
EP.04 Those Who Speak in Light
EP.05 Grace's Equation (Finale)
— 22B Labs · the4thpath.com