Chapter 1210 High Altitude Test

Yungang.

101 high-altitude simulation test area.

Several Coaster minibuses with dark side windows were filed on the winding mountain road, and finally stopped in a parking lot halfway up the mountain.

Rocket engine testing must of course be conducted away from populated areas.

Combined with a series of requirements such as confidentiality, noise reduction, and energy supply, in most cases, mountains will be chosen.

Therefore, as soon as Chang Haonan got off the car, without even entering the control center, he saw two white and blue-roofed buildings elevated in mid-air, about a few kilometers apart.

Compared with the ground-based high-thrust test benches seen on the road, the scale of these two buildings is significantly smaller.

But it's still complete.

There are also some inconspicuous auxiliary equipment distributed nearby.

Near one of the test stands, several chimney-like things were emitting light white smoke, obviously making final preparations before the test run.

"Academician Chang, this is the GS-2 high-altitude simulation test bed that our institute just built at the end of last year. It is planned to be used for testing the second and third stages of the new generation launch vehicle... But in addition to the acceptance test, this is actually Put into official use for the first time..."

The deputy director of the Yungang Experimental Zone who was responsible for the reception was Wang Zhiwu, who also graduated from Beijing Hang University.

He was following Chang Haonan, walking towards the control center not far away while introducing the basic situation of the test run:

“GS-2 uses the same engine-supersonic diffuser-steam ejector pump combination as the GS-1, but it can withstand greater thrust and fuel pressure and can simulate high-altitude environments up to 60km for full-scale operations. System cold and hot test..."

In order to reduce the design difficulty of the power system, the hypersonic verification projectile adopted the air-launch method at the beginning of the planning. The engine will work at an altitude of more than 15km for almost the entire process, so the test process is also similar to the secondary engine of a general launch vehicle.

"Due to cost and construction period issues, only 8 units of YF76 can be used for testing. Although the total reliability index in the design requirements is not high, considering that the engine is basically a "single point of failure" from the whole machine to the components, we still The edge working condition test method inherited from the 921-4 project is adopted. The single test time is 600 seconds, the cumulative time is not less than 57,600 seconds, and the thrust variation range is 86%-106% of the rated thrust..."

"..."

YF76 is the name given to this engine internally by the Sixth Academy——

The core first-stage and core-secondary engines currently being developed for the new generation of heavy-duty launch vehicles are called YF77 and YF75D respectively.

The engine used in the Gaochao verification bomb, although its thrust is much smaller than the two above, actually uses a lot of the same technology.

So I gave it a name somewhere between the two.

While they were talking, the group of people had already walked into an unprepossessing building nearby.

Since rocket engine test runs are much more noisy than jet engines, and they also involve extremely dangerous propellant components such as liquid oxygen and liquid hydrogen, the control hall and test bench are generally not placed together.

At this time, Zheng Bin, the commander-in-chief of the entire test work and the most powerful person in the Yungang test area, was sitting behind the command podium, waiting for the final moment to issue the engine ignition command.

When he saw Chang Haonan and others walking in, he stood up immediately:

"Reporting to the person in charge, the YF76 engine test run is ready. All indicators are confirmed to be normal and the test can be started at any time!"

Chang Haonan is the overall person in charge of the entire hypersonic weapons research and development task, but he does not directly manage the work of Institute 101. He is under the county magistrate's jurisdiction and is not under current management.

So he didn't answer directly, but looked at Chen Zhiwei, who was half a body behind him.

"Director Chen, we are just conducting on-site observation, you just continue to follow the scheduled schedule."

"yes!"

Duan Zhengbin gave a crisp answer and then sat back at the command station.

The engine test bench is equivalent to a launch tower that cannot be flown.

The test command hall is almost the same in configuration as the control hall of the satellite launch center.

In the upper right corner of the big screen at the front, a countdown with less than 10 minutes left was displayed.

That's when testing was planned to begin.

…

Just like the situation before the rocket was launched, a tense and silent atmosphere filled the entire command hall.

In other words, more than a formal rocket launch.

After all, most of the ones ignited here are immature models that are still in the development process, and the probability of failure is much higher than the official launch.

Only one or two passwords could be heard occasionally, as well as the hurried footsteps of some technicians.

Finally, the time displayed in the upper right corner of the screen reached the countdown of 10 seconds.

Duan Zhengbin took a deep breath, pushed open the cover on the ignition button with his thumb, and at the same time moved closer to the microphone in front of him.

Before counting down to the last five seconds, he used the corner of his eye to check the working conditions of the two subsystems of liquid hydrogen and liquid oxygen.

There are 22 sensor parameters on the screen, all displayed in green.

Everything works fine.

The steady and clear voice was like a bell, ringing in the ears of everyone present:

"5...4...3..."

"..."

"ignition!"

At the moment the sound fell, a brilliant flame flashed at the engine nozzle under the test bench.

The high-temperature airflow generated by the combustion of hydrogen and oxygen gushed out of the thrust chamber at a speed of more than 15 times the speed of sound in less than one tenth of a second, and poured out of the test bench along the steel plate at the bottom of the guide groove.

The dazzling light almost illuminated half of the hillside next to the test bench.

At the same time, the water jacket under the test bench opened and began to cool the load-bearing bracket and cement base.

Where water and fire blended, a white cloud that covered the sky and the sun immediately formed.

On the big screen, the camera lens closest to the test bench was even shaking slightly.

A few seconds later, a roar that was slightly behind the visual effect reached everyone's ears.

Although it was already far away and the sound waves had been significantly weakened by rocks and trees, it was still possible to feel the huge thrust that the test bench was bearing at this time...

Compared with Chang Haonan, the staff of the test center had long been accustomed to such scenes.

YF76 is not even considered to have a relatively large thrust among rocket engines.

Soon, the first report sounded from the loudspeaker:

"The engine operating parameters have reached the initial operating conditions!"

The initial point is the rated operating condition where the engine thrust and mixture ratio are at the design value. The engine operating conditions are relatively the best and it is also the starting point of almost all test processes.

However, the marginal operating condition test method adopted by YF76 takes into account the extreme working state of the engine.

Therefore, the successful ignition can only be regarded as the first step in a long journey.

Duan Zhengbin felt relieved and gave a new follow-up instruction:

"Adjust the working parameters to A1 working condition."

As soon as he finished speaking, Chen Zhiwei leaned close to Chang Haonan's ear and explained:

"A1 working condition is low thrust and low mixing ratio. The working parameters are obviously lower than the rated working condition. The turbine speed is reduced, and the pump outlet pressure is also reduced accordingly, but the pressure required by the thrust chamber does not change much, so the vibration environment is relatively harsh, which is a big test for the main structure of the engine..."

As if to verify this statement, the vibration acceleration curve displayed on the large screen began to fluctuate violently, which in turn caused dozens of other key parameters to change.

Fortunately, the control feedback system started to work almost immediately, controlling the working parameters of each system within an acceptable safety range.

Chen Zhiwei continued:

"We took into account that the vibration and initial ignition posture of the rocket in the case of air launch are much worse than ground launch, so we left a lot of redundant space at the beginning of the design to ensure the reliability of ignition and the initial 10-second posture adjustment phase to the highest state..."

"..."

Looking at the test time jumping on the screen, Chang Haonan also breathed a sigh of relief:

"The bomb bay of our air-launched vehicle was not designed for this kind of mission, so it needs to be specially modified."

"If there is no problem with today's preliminary test data, the basic parameters of the thruster can be sent to Gaofei Group..."