The Hungry Fortress Wants to Build a Battleship in Another World – World of Sandbox

"10… Ten… 9… Nine… 8… Eight… 7… Seven…"
The countdown was underway.

Today, a research rocket was being launched from an improvised launch pad hastily built over the ocean. Frustrated by the lack of valuable resource discoveries, Commander Eve had begged to give the order—and finally, it was decided to allocate a portion of their resources to space development.
This opportunity only became possible thanks to the increasing supply of resources from Fortress No. 2.
That said, once some tangible results were obtained, the launch pad would be dismantled and the area repurposed for building a seafloor platform.

"Ignition… Thrust at target value. 2… Two… 1… One… Lift-off confirmed."
The rocket being launched today was a disposable solid-fuel type.
It carried research equipment in its nose and would continue accelerating as long as the fuel lasted. If it failed to break free from the planet’s gravity well, it would fall back down. If it did succeed, it would function as a makeshift satellite for several days.

Since it had almost no onboard propulsion or orbit correction systems, it was expected to eventually fall back into the atmosphere and burn up.
"Unit One is ascending normally. Passing altitude: 5 km."
"Whoa, fast, fast!"

The rocket was light and a pure launch-and-forget type. The second stage also used solid fuel, and beyond the fuel itself, it had minimal onboard systems.
"Altitude 10 km reached. 11… 12…"
The rocket continued to ascend smoothly. Based on data from high-altitude early warning planes launched earlier, reaching close to 20 km posed no issues.

"Altitude 18 km. Discrepancy detected between the acceleration sensor and radar measurements."
"...It's happening again."
As observed during previous launches, the rocket’s rate of ascent had begun to slow.

Despite no visible issues, its acceleration had clearly dropped.
This time, however, the rocket was equipped with precision accelerometers, allowing the anomaly to be quantified—specifically, a discrepancy between visible acceleration and gravitational acceleration.
"Rocket motor combustion temperature is nominal. No anomalies in body temperature, pressure, or vibration. Based on observational data, there is a possibility that gravitational acceleration is increasing."

"...Huh? Wait—gravitational acceleration can change?"
"It cannot."
"Right!? It can’t, right?!"
There were no signs of abnormalities in the rocket motor’s combustion. Observations across the electromagnetic spectrum revealed nothing strange either.

Internal sensors all reported normal conditions—except the accelerometers. While internal acceleration remained consistent across all axes, the externally calculated acceleration using radar data showed a visible decline.
In short, some unknown external force was acting on the rocket and slowing its acceleration.
The most obvious suspect was air resistance. But for atmospheric density to increase with altitude? That didn’t make sense.

A change in atmospheric composition couldn’t be ruled out, but prior high-altitude flights up to around 30 km had found no such irregularities.
That left gravity—specifically, planetary gravity—as the only remaining possibility.
"I’ve had doubts from the beginning. This planet is significantly larger in diameter than Earth, yet its gravitational acceleration is ★ 𝐍𝐨𝐯𝐞𝐥𝐢𝐠𝐡𝐭 ★ roughly 9.81 m/s²—identical to Earth’s. Since gravity is determined by mass and diameter, the odds of matching Earth’s gravity to the fifth decimal place are vanishingly small."

"...I mean, yeah, that is kinda weird. But I guess it could be that the mass and diameter just happen to balance out?"
"Yes, Commander Ma'am. But the chance of that happening and resulting in Earth-equivalent gravity is nearly zero. And then, this planet just so happens to have water, thriving life, and even a humanoid species genetically almost identical to humans? It’s far more reasonable to assume some kind of intentional design."
Even as explained, the rocket continued to climb. Its speed lagged behind projections, and therefore so did its altitude.

Still, the rocket passed 60 km and kept ascending.
"First-stage motor burnout. Burn complete. Stage separation. Second-stage motor ignition… Combustion stable. Fairing separation: success."
closely monitored the rocket’s trajectory. With the engine now off, they were observing acceleration in near-vacuum conditions where gravity was the only remaining force. The onboard accelerometer data was compared with radar-based speed calculations.

"Commander Ma'am. It’s confirmed. Gravitational acceleration at high altitude appears significantly greater than on the surface."
"...Wait, what? That doesn’t make sense."
The farther you get from the surface, the stronger gravity gets?

That flew in the face of physics. Gravity was supposed to weaken with distance from a mass, not strengthen.
Granted, within 100 km altitude, the difference might fall within the margin of error.
"Commander Big Sister… I just finished the calculations… I think gravity’s about double in the upper atmosphere…"

"Thanks, Olive. So... gravity doubles as you go higher…?"
"Altitude 120 km. Acceleration now stable. Gravity is roughly twice that at the surface. No further increase observed. Due to the higher gravity, target orbital velocity hasn’t been reached."
"Ugh…"

Orbital velocity is, to put it simply, the speed at which an object must travel at the right angle to enter stable orbit without falling back to Earth.
If that velocity isn’t reached, the object will inevitably crash back down.
The rocket’s thrust, as it turned out, wasn’t enough to reach that speed.

"Assuming surface gravity is 9.81 m/s², and the planet’s diameter is about 20,000 km, we calculated that reaching orbital velocity—36,600 km/h at 300 km altitude—would allow the rocket to become a satellite. But based on current acceleration, we might not even reach 25,000 km/h. And with gravity being double, the required orbital velocity would be over 50,000 km/h. We’ll need a complete redesign of the rocket motor."
"...So, basically, we need double the power?"
"Yes, Commander Ma'am."

answered, though the reality wasn’t quite so simple.
Boosting thrust would mean strengthening the rocket motor or adding more nozzles. Either way, that added weight to the rocket. That extra weight required even more fuel, and more fuel meant even more weight.
It was a compounding cycle, where the total rocket mass increased rapidly while launch capability remained fixed.

"Commander Big Sister… what should we do…?"
"...We either pour in more resources or give up for now..."
If left to and Olive, they could probably continue development with minimal resource waste. But new development always consumed resources like water through a sieve. Seafloor platform construction would grind to a halt, and even Fortress No. 2 might suffer delays.

"Ughhh... For now, we’re freezing space development. Redirect the resources to the mines at Fortress No. 2 and the seafloor platform construction. Once the platform is operational, we’ll have more wiggle room. We’ll revisit space development then."
"Yes, Commander Ma'am. Olive, set the priority low, but proceed with designing the solid rocket motor. Once resources free up, we can begin testing immediately."
"...Okay."

Just as the policy was being finalized aboard , the rocket’s acceleration came to an end.
"Second-stage motor cutoff. Stage separation. Third-stage engine ignition… Combustion started, all sensors reading nominal. Fuel tank pressure is stable."
The first rocket launched by ultimately reached an altitude of 400 km.

There, it ran out of fuel and detached its payload.
The observation unit continued to ascend by inertia, but eventually, it was captured by the planet’s gravity and began falling.
"...Observation unit’s surface temperature is rising. High heat detected due to adiabatic compression."

Collecting a wide range of data on its descent, the observation unit finally disintegrated on reentry.
That data, however, would go on to support future advances across multiple disciplines.