Chapter 1285 Boeing's Troubles

Almost at the same time.

Delaware, United States.

Boeing Test Center in Wilmington.

X51A project manager Shapur Collinger was leaning over a monitor, concentrating on examining several three-dimensional spectra on the screen, an expression of relief mixed with excitement on his face.

Although it still takes some time to export and organize the detailed test data, as an experienced old engineer, he can basically judge from the sound and light effects produced during the propellant combustion process that the medium and low frequency pressure oscillation stage at the end of the engine operation has been shortened from more than 12 seconds at the beginning to about 7-8 seconds.

Under normal circumstances, the solid rocket engine from the ATACMS missile can maintain an effective working time of more than 40 seconds. However, when the propellant combustion reaches the middle and late stages, the coupling of the fluctuating heat release rate and pressure oscillations is likely to produce a gain effect on the air pressure amplitude. For hypersonic aircraft with relatively sophisticated structures, it is likely to induce abnormal start-up of the scramjet engine or even direct disintegration.

Therefore, the booster section must be jettisoned before pressure shocks cause a sharp rise in combustion chamber pressure to ensure the normal transition from rocket power to air-breathing power.

As a result, the original version of the solid booster had a usable working time of less than 30 seconds.

Although if a hypersonic flying body is to be propelled to above the predetermined Mach 5.5 by relying on solid rockets, the available working time should be close to 40 seconds, which is equivalent to a shock phase of less than 5 seconds, scientific research is not a process that can be achieved overnight.

Excluding the approximately two months spent on the initial contact and mutual adaptation stage, Collinger was already quite satisfied that he had achieved more than half the progress in just half a year.

After all, Pratt & Whitney's SJX51-61 engine, which serves as the core power of the X1A aircraft, has just begun high-altitude simulation tests.

If this efficiency continues, it would no longer be a far-fetched idea to complete the first test flight of the entire project one year ahead of schedule, before 2008.

Thinking of this, Ke Lingjie breathed a sigh of relief. The mood that had been suppressed by the construction schedule for half a year finally became a little smoother.

He began to constantly give himself psychological hints——

Over the past century, the United States has always led the development of humanity's most advanced aviation technology, both in terms of altitude and speed.

Although he inevitably faced many challenges throughout the process, he never handed over his leadership position to others.

Since it was like this in the past, it should be like this now...

Having regained his confidence, Collinger did not dwell on his thoughts for too long. Instead, he immediately prepared to contact the testing department to arrange a test station for the upgraded solid rocket booster.

At this moment, Deputy Charlie Brink happened to push the door open from outside, holding an open folder in his hand.

"Supervisor, the test results have been extracted."

He turned the document in his hand around and placed it in front of Ke Lingjie, pointing to the pressure-time graphs on it and said:

"From the results, it can be seen that after the third metal component was introduced into the propellant, the pressure oscillation range generated by the final stage of solid propellant combustion was indeed significantly shortened. Among the five ratios tested, the longest one was only 5 seconds, while the shortest reached 7.4 seconds, which is very close to our design goal."

"Next, Dr. Hurst will continue to optimize the propellant composition and particle morphology. According to the empirical formula currently used, under ideal conditions, it should be possible to achieve a level of about 3.5 seconds..."

"3.5 seconds..."

Ke Lingjie sat down on the chair behind him and muttered to himself:

"It can work effectively for more than 40 seconds before the booster stage is abandoned, which is about a 5% design margin..."

For most engineering projects, a 5% margin is indeed a bit too much.

But considering that the set starting speed of 5.5 Mach is already a safety value, it is acceptable for the X51A project.

In comparison, the risk that Collinger was worried about was in another area.

After thinking for a few seconds, he raised his head again and looked at Brink standing next to him:

"How to simulate the working conditions under actual conditions? Especially after the ignition process, how are the combustion characteristics of the propellant under pressure different from those in an ideal environment?"

Due to limited conditions, the test method chosen by the Wilmington Test Center is to first use a metal atomization particle generator to disperse the metal particles, then the metal particles enter the carrier gas flow, use the light scattering principle to measure the particle size of single aluminum particles, and finally use carbon dioxide laser ignition to obtain the various characteristics of the particle combustion process.

Obviously, in this technical solution, the combustion of the propellant is in a completely open state throughout the entire process, so additional equipment is needed to restore the actual working environment of high temperature and high pressure.

“It has been tested.”

Brink flipped back a few pages of test results, which showed a series of two-dimensional spectra.

Judging from the shape of the curve, it should be extracted from the three-dimensional picture on the computer just now:

"Applying pressure will reduce the intensity of the entire spectrum, among which the intensity of the characteristic peaks of aluminum and aluminum oxide will decrease significantly, indicating that applying additional pressure may reduce the formation of Al vapor and AlO groups, that is, it will hinder the complete combustion of the metal fuel aluminum in the propellant to a certain extent."

"However, from a quantitative perspective, the magnitude of this effect is not large. For example, at 15 atmospheres of pressure, the energy release of propellant samples No. 3 and No. 4 only reduced by less than 1.5%. The reductions of No. 1 and No. 2 were larger, but also less than 3%. And it is obvious that this effect will weaken as the diameter of the aluminum particles decreases..."

Ke Lingjie did not express his opinion immediately, but just half lowered his head, looking thoughtful.

As an old-school engineer, he still hopes to obtain as much data as possible before the flight test to ensure the success rate of the first launch.

But objectively speaking, the current testing conditions only allow restoration to this extent.

Higher speeds, total temperatures and pressures require even higher performance ultra-high-speed wind tunnels.

Neither Boeing nor NASA had the equipment that met the requirements.

This means that he needs to take some additional risk no matter what.

Looking at his leader's uncertain expression, Brink quickly guessed what he was thinking.

To be able to climb from an ordinary engineer to the position of deputy project manager in a short period of time, his ability to read people's expressions must be very good.

“Although tests with a higher degree of reduction are not yet possible, Dr. Hurst has fitted a semi-empirical and semi-theoretical relationship curve based on the existing test data and the melt dispersion reaction mechanism model.”

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He said and turned the page again:

"The actual energy release curve shows a sharp increase in the range of 6-12 atmospheres, and when the working pressure is further increased, the curve tends to be flat and basically does not change after 15 atmospheres..."

In engineering projects, it is common to conduct simulations based on partial test results for parts where theoretical principles are not yet clear or cannot be fully considered due to computing power limitations.

For a long time, Boeing has indeed been at the forefront of the world in this field, but it has only been gradually surpassed by up-and-coming companies on the other side of the Pacific in recent years.

Therefore, Collinger does not subjectively reject this conclusion.

However, compared with actual tests that are sure to be correct, the accuracy of the simulation results is highly dependent on the operator's own thinking and ability. Understanding the situation indirectly through technical documents like this still makes him feel a little uncertain.

"Where is Dr. Hester himself now?"

After thinking for a moment, Ke Lingjie asked:

"I hope to talk to her face to face about this outcome."

Brink was slightly stunned:

"She just returned to Boston the day before yesterday. She said that the professor had some urgent matters to deal with..."

Ke Lingjie frowned slightly.

Since the two sides started collaborating at the beginning of the year, he had only met Dr. Mellie Hurst once, when the research project was launched.

Although researchers of this level are very busy and it is normal for them to have several projects on hand at the same time, it is inevitable that Colinjie is worried when it has been like this for most of the year.

Fortunately, at this time, Brink quickly continued:

"But Dr. Daniel Jablonski, who has been in charge of this work, is at the Ultra-High-Speed Optical Testing Center next door. If you have any questions, you can contact him..."

At this point, Collinger had no choice but to nod, then stood up and took the coat draped over the back of the chair.

But before leaving, he suddenly stopped and looked back at Brink:

"That's right, Charlie."

"The Ministry of Defense and the board of directors have already asked about the progress of the X51A project many times. Please compile the test results into a report and submit it to Chicago as soon as possible."

The latter was busy sorting out the test results that had just been messed up. After hearing this, he hesitated for a moment:

"If you want to submit a mid-term report, you must give a more specific timetable..."

Ke Lingjie raised his hand and rubbed his swollen brows, while going over the recent situation in his mind as quickly as possible -

Although there are still some imperfections, there is more positive news overall.

"According to the military's request, the first test launch can be carried out before 2008!"