Chapter 228 - 222 There’s Another Way_1

"Our independently developed CZ-10 rocket made its inaugural flight on August 12, and the mission was unsuccessful in its latter half."

As headlines broke the next day, many viewers who had watched the launch found it unbelievable.

Because in the understanding of most people, the CZ-10 had neither exploded nor veered off course, so how could it fail? It was a clear success.

However, during an interview with Chief Engineer Yun Hongjun following the midday news, he only mentioned with exhausted eyes, "We’re actively looking for the cause."

In fact, the team had already preliminarily determined that the problem with the YF77 shutting down was due to the engine itself and not related to the rocket body; it should be an issue for the Sixth Institute.

Meanwhile, Liu Minglu had flown back to Chang’an overnight, dragging out four YF77 prototypes from the factory and placing them on the test stand for trials.

At 7 p.m. on August 13, Liu Minglu ordered grimly,

"Begin the fifth 1000-second long-duration test!"

An hour earlier, all four engines had undergone a 500-second test without any issues, but Liu Minglu immediately organized a second, third, and fourth test and quickly called for more liquid hydrogen tankers.

This time, after 670 seconds of continuous operation, Engine No. 3 exploded with a bang; its turbine pump impeller fractured, and the high-speed debris blew a sizable hole in the nozzle, prompting an emergency shutdown of the engine."

The tests on the other two engines were also immediately halted, as the cause was evidently clear.

Liu Minglu merely glanced into the wreckage of the engine from a distance and knew it was the problem he had in mind.

High-thrust hydrolox engines were still too challenging.

In the early 70s, the space agency developed the YF70 hydrolox engine from the then-active primary YF20 engine; officially, it became the YF73 later on, with four combustion chambers and less than five tons of thrust;

Subsequent was the YF75, with eight tons of thrust per combustion chamber, used for the upper stages of the CZ-3 series; and then in 2002, the YF77 project started.

The vacuum thrust of the YF77 is 70 tons, over eight times that of the YF75. Such a significant leap, combined with the intrinsic difficulty of hydrolox engines, led to numerous problems during the development process.

However, 14 years of development and a cumulative 50,000 seconds of testing had convinced them of the YF77’s reliability, even if this number wasn’t particularly impressive.

America’s Space Shuttle main engine SSME accumulated over 100,000 seconds of testing before its first flight, so the experience with the YF77 couldn’t be described as extensive.

In addition, due to the small molecular size and extremely low temperature of liquid hydrogen, the material and manufacturing specifications for hydrolox engine pipelines were very high, coincidentally in some aspects a weak point for the space agency.

Liu Minglu remained silent for a long while before instructing the remaining three engines to go through a 1500-second extended-duration test.

After running the test twice in succession, Engine No. 2 began to show instability in its thrust at 1020 seconds because of a malfunction in its oxygen pump, leading to discontinuous fuel supply. After several significant fluctuations in thrust, the pale blue tail flame suddenly disappeared, and Engine No. 2 shut down.

Two out of four engines failing clearly indicated that there were design issues with the YF77, rather than mere coincidence.

These extended-duration test trials had never been conducted before, and the most concerning issues had not been discovered, now surfacing at last.

By the afternoon of the 14th, Yun Hongjun and Liu Minglu had put together a lengthy 4000-page accident investigation report and presented it to Academician She.

Academician She didn’t even glance at the stacks of paper as thick as dictionaries, casually pushing them aside and looking at the two men in front of him, who had evidently not gotten proper rest.

"Sit down, both of you, you’re not criminals. What’s the need to stand?"

He stood up himself to let them sit, then brewed two cups of tea and moved a chair opposite the sofa to sit down.

"I laid the foundation for the CZ-10, and the engine selection was predetermined; it’s not your fault;

Within 10 months, getting the CZ-10 out without blowing up the launch pad is a success, and the people of the nation don’t blame you; you’ve done very well."

Indeed, there wasn’t much public outcry, and the engine failure reported by the space agency didn’t seem too serious to people.

For 99% of the population, so long as the rocket had flown out of their sight without exploding, that pretty much counted as a success, and the rest were just minor issues.

But Yun Hongjun obviously didn’t think so, "No, it’s all my responsibility. If an astronaut had been onboard, with some luck they might have returned, but with bad luck..."

"The engine was our..."

"Enough, I’m not here to make you bear responsibility, nor to have you write self-criticisms,"

Academician She pointed to the thick stack of reports behind him:

"Those will just sit in the archives, unseen. What I want to know is whether you have confidence to resolve these issues. By April 2017, can you complete the New Yuan-2 mission with the new generation of manned spacecraft?

Our primary objective is still the Moon!"

The CZ-10’s New Yuan-2 mission would send an unmanned crew vehicle into lunar orbit and then return. The next time, it would carry at least three astronauts for a full-dress rehearsal of a manned circumlunar flight, and after that would be the lunar landing.

If there were issues with the New Yuan-2 mission, then the third would not be able to carry humans, which means unless the fourth flight circumnavigating the Moon directly took the risk to land, the human lunar landing would inevitably be delayed until 2019.

The inaugural flight had only affected one YF77, so all tests were still completed; this time two YF77s were used on the third stage, luckily with no major issues arising.

But it was enough to demonstrate the importance of the YF77 to the CZ-10. Once astronauts left the atmosphere, whether they could successfully fulfill their mission and return depended entirely on the YF77.

Not one of the six YF77s can fail during the mission process!

Liu Minglu clenched his fist and stood up:

"The main issues with the YF77 lie in the turbine pump bearings and impeller. The Sixth Institute has six months to resolve these issues."

Six months to fix the problem, one month for testing, and half a month to manufacture the rocket for the New Yuan-2 mission. The timing should be just about right.

Academician She nodded, not blaming them for the long time it took to develop a 70-ton class YF77, fully aware of the difficulty in developing hydrolox engines and the previous lack of experience at the space agency.

Six months seems long, but one must remember the YF77 project was launched 14 years ago.

"There’s another solution,"

Yun Hongjun suddenly spoke up:

"The Xinyuan Company has two hydrolox engines, the H50 and H240, with vacuum thrusts of 50 and 340 tons respectively. We can use them directly, without changing the design."

The naming convention for the H50 and H240 is different; the H50 is specifically for vacuum use, so the number represents its vacuum thrust; there are two versions of the H240, the sea-level version used on the first stage has a thrust of 240 tons, and the vacuum version—with an enlarged nozzle used on the New Yuan-2A and New Yuan No. 3—has a vacuum thrust of 340 tons and a specific impulse of 466 seconds.

One H240 could completely replace four YF77s, and two H50s could also replace two YF77s. Although slightly less powerful, the specific impulse of the H50 reached 459 seconds, surpassing the YF77’s 432 seconds, and the difference was negligible. It was usable.

As for Xinyuan’s H80, it was currently being tested, so its performance was still unknown.