“Ten seconds to go. In ten.”

“Pressures in all tanks nominal.”

“Release the restraints.”

“Vehicle status, all systems normal. All green.”

“AI assessment: permission granted. Go.”

“Two, 2, one, 1, ignition. Ignition.”

“Orbital insertion vehicle No.1, Booby 1, launch. Liftoff.”

The dual-propellant oxygen–methane rocket engine spewed flame and smoke as it pushed the vehicle upward.

The launch rocket steadily gained altitude without incident.

Orbital insertion vehicle No.1, Booby 1. Bearing the name of the seabird “booby,” it was the first space rocket that The Tree had finally completed.

Its launch capacity was roughly five tons to an altitude of 500 km. The second stage housed the injection satellite, and the first-stage rocket was a reusable configuration that would return under its own power to the launch pad. In addition, the second-stage rocket itself had an altitude-maintenance function; after releasing its payload, it would remain in orbit as a satellite platform.

Once the number of units increased, it would even be possible to operate them as a space station.

“Launch successful. ...Commander Sis, it went well...”

“There, there, there, there! Olive, you did it properly!”

To that blatant “please praise me” appeal, Commander Eve responded with everything she had. Of course, the other sisters helping with control would all need head pats later as well, but first she had to reward Olive, who had led the design and manufacture of the orbital insertion vehicle.

“All right, time to unveil our very first reconnaissance satellite. Ichigo, that gravity issue is within expected parameters, right?”

“Yes, Commander Ma’am. Plus ninety-two seconds. Altitude has passed 17 km. We have confirmed the gravity-increase phenomenon. The increase is within our expected range.”

This planet’s peculiar variation of gravitational acceleration with altitude. From around 16 km upward it gradually began to rise, reaching its maximum at roughly 37 km. The value at that point was 1.87 G.

The rocket engine of the orbital insertion vehicle was rated to produce thrust sufficient for this maximum gravity.

“All observed values are within the expected range. Next, at an altitude of approximately 120 km, we will separate the first-stage rocket. About thirty minutes later, at around 500 km, we plan to deploy the satellite.”

“In about ten minutes, the orbital insertion vehicle will be coming back, yeah~”

“Think it’ll be able to land properly?”

Utsugi and Erika were in charge of monitoring each sensor value. The two of them specialized in real-time analysis. They were highly suited not so much to precise final analyses as to calculating trends and predicted values.

Ringo classified this as on-site pragmatism.

“Measured gravitational acceleration: no deviation from the predicted maximum.”

“Thrust nominal. Combustion temperature within tolerance. All tank pressures normal. Vibration frequencies in all sections within tolerance.”

“Altitude still rising; vehicle has reached the designated altitude. First-stage rocket, shutdown. Second-stage separation executed. Completed normally.”

“Second-stage rocket, engine ignition.”

“Ignition confirmed. Second-stage rocket station, resuming acceleration.”

In the transmitted footage, the first-stage rocket deployed its air brakes and rapidly dropped away. At an altitude of 120 km, Booby 1, having lost thrust, soon began freefall.

“Everything’s going smoothly.”

“Yes-affirmative, Commander Ma’am. After this, Booby 1 is scheduled to return to the launch pad. After a simplified inspection and refueling, once we mount the second-stage rocket, it will be ready for another launch in four hours.”

A disposable rocket would have terrible cost performance. For that reason, all space rockets manufactured by The Tree were reusable vehicles.

The second-stage rocket station itself did not have any independent atmospheric reentry function, but by resupplying propellant with a separately launched supply craft, it could continue its ★ 𝐍𝐨𝐯𝐞𝐥𝐢𝐠𝐡𝐭 ★ orbit at an altitude of about 300 km.

“What’s the subsequent launch schedule?”

“Yes-affirmative, Commander Ma’am. Provided Booby 1’s first unit and the subsequent units up through No.3 present no issues, we will launch ten second-stage rocket stations.

“In parallel with this, we will deploy sixteen satellites of various types.

“At the same time, we will bring orbital insertion vehicle No.2, Booby 2, into operation, equipped with additional boosters for geostationary orbit insertion, and inject multiple geostationary satellites for GPS use.”

A mass deployment of satellites by reusable spaceplanes.

The rocket propellants were liquid methane and liquid oxygen. Liquid hydrogen offered better performance, but it was extremely difficult to handle.

Particularly for a reusable configuration intended to endure the harsh conditions of repeated launches, extensive structural reinforcement and measures against vibration and heat were required.

The problem of metal embrittlement caused by liquid hydrogen also had to be addressed.

Thus they used a methane-fueled rocket, whose specific impulse was reasonably high.

Compared to hydrogen—only compared to hydrogen, but still—it was easier to handle, and the fuel tank structure could be made simpler. Also, because its boiling point was close to that of oxygen, the need for thermal insulation measures was almost negligible compared to hydrogen.

In addition, the low procurement cost was attractive: methane could easily be recovered from gas fields and methane hydrate.

“Sounds good. What about effects on the surrounding environment?”

“Yes-affirmative, Commander Ma’am.

“The launch site has been constructed on a rocky reef 2 km south of the fortress The Tree.

“Visual detection range of the rocket is estimated, depending on atmospheric conditions, at about 500 to 800 km.

“All of this area lies within The Tree’s sphere of influence, and there are no continents, islands, or signs of any other human forces.

“The sole concern is the occasional sailing vessel engaged in distant-water fishing, but as they are within our surveillance zone, we can adjust launch times. Also, if it is overcast, there is no need to worry.”

“Okay. Well, I’m not worried about the surveillance posture anyway. We’ve scanned everything around us, including underwater. We have physical monitoring posts, and the drones are running fine.”

Commander Eve nodded and gave her seal of approval to the plans going forward.

While they were exchanging those words, the main screen tagged Booby 1 descending with its exhaust nozzle pointed down.

“It’s back.”

Booby 1 was a somewhat squat, cylindrical rocket.

It had deployed its attitude-control fins and was dropping in a straight line toward the launch pad. Its descent speed was roughly 1,000 km/h and gradually decreasing.

“Descent speed within tolerance. Vehicle status, normal, all green. Transitioning to reverse-thrust ignition sequence.”

“Three, 3, two—‘tow’—2, one, 1, now, ignition.”

“Booby 1, initiating reverse thrust.”

“All instrument values nominal. Descent speed decreasing.”

In the telescopic feed, orbital insertion vehicle No.1, Booby 1, rapidly bled off speed as it closed in on the launch pad.

“Thirty meters to touchdown... twenty... ten... touchdown. Position correction within tolerance. Engaging restraints.”

“Restraints secure. Next, connecting composite cables... complete. Booby 1 switching circuits to external power.”

“Activating cooling systems. Beginning vehicle cooldown.”

“Valve connections complete. Beginning oxidizer and fuel drain.”

“Second-stage rocket station No.4 now being transferred from the hangar.”

The returned Booby 1 immediately underwent various inspections for reuse. If no abnormalities were found, they would mount a second-stage rocket station on it, and about four hours later it would once again wing its way toward space.

“Commander Ma’am. The check sequence is proceeding normally. No significant issues detected.”

“Roger. Then let’s move on to the next.”

“Yes-affirmative, Commander Ma’am. Initiating launch sequence for Booby 1 units two and three.”

The first unit had been launched alone just in case.

As a result, without a single problem, the second-stage rocket station was delivered to satellite orbit.

“Roger. Beginning oxidizer and fuel loading for Booby 1, units two and three.”

“Executing final checks for all components in the launch sequence.”

And so, by evening of that day, The Tree had placed six second-stage rocket stations into satellite orbit.

All ten satellites that had been deployed succeeded in approaching their planned orbits.

The second-stage rocket stations themselves had each now entered orbit and were conducting adjustments of their various systems. From here, while performing orbital changes, they would repeatedly dock to form three station groups.

Commander Eve and the five sisters, having safely wrapped up the major task of injecting satellites into orbit, set off on a journey into the land of dreams.

Meanwhile, the youngest sister, Asahi, was staying up late at the Telek Port City base.