The military-industrial scientific research system of the academic master

Chapter 1285 Boeing’s Troubles

Almost at the same time.

Delaware, USA.

Wilmington Boeing Test Center.

X51A project director Shapur Collinger was leaning over a monitor, looking at several three-dimensional spectral images on the screen attentively, with an expression of relief mixed with excitement on his face.

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

Under normal circumstances, the solid rocket motor from the ATACMS missile can maintain an effective working time of more than 40 seconds. However, when propellant combustion reaches the middle and late stages, the coupling of fluctuating heat release rate and pressure oscillation may have a gain effect on the air pressure amplitude. , for a hypersonic aircraft with a relatively delicate structure, it is likely to cause the scramjet engine to start abnormally, or even directly disintegrate.

Therefore, the boost stage must be thrown away before the pressure oscillation causes the combustion chamber pressure to rise sharply to ensure the normal conversion from rocket power to air-breathing power.

As a result, the available working time of the initial version of the solid booster is less than 30 seconds.

Although if you want to rely on solid rockets to propel a hypersonic flight body above the scheduled Mach 5.5, then the available working time should reach a level close to 40 seconds, which is equivalent to less than 5 seconds in the oscillation stage, scientific research is not a process that can be accomplished overnight. .

Excluding the approximately two months of early contact and mutual adaptation, Collinger was quite satisfied that more than half of the progress could be made in just half a year.

After all, Pratt & Whitney's SJX61-1 engine, which is the core power of the X51A aircraft, has just begun high-altitude platform simulation tests at this time.

If this efficiency continues, it seems that it will no longer be a whimsical thing for the entire project to be completed one year ahead of schedule and complete the first test flight before 2008.

Thinking of this, Collinger relaxed a little, and his mood, which had been suppressed by the construction period for more than half a year, finally became smoother.

He began to constantly give himself psychological hints -

For more than a century, the United States has always led the development of mankind's most cutting-edge aviation technology, regardless of height or speed.

Despite the inevitable challenges along the way, this leadership role has never been relinquished to others.

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

Collingie, who had returned to a complacent state, did not immerse himself in his thoughts for too long, but 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 in from the outside, holding an open folder in his hand.

"Supervisor, the test results have been extracted."

He turned the document in his hand and put it in front of Collinger. He pointed at the pressure-time curves on it and said:

"Judging from the results, after the third metal component is introduced into the propellant, the pressure oscillation interval generated at the end of the combustion of the solid propellant is indeed significantly shortened. Among the five ratios participating in the test, the longest One is only 7.4 seconds, and the shortest one has reached 5.6 seconds, which is very close to our design goal.”

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

"3.5 seconds..."

Collinger murmured to himself as he sat on the chair behind him:

"It is equivalent to being able to work effectively for more than 40 seconds before abandoning the boost section, which is about a 5% design margin..."

For most engineering projects, a 5% margin does seem a bit limiting.

However, considering that the set starting speed of Mach 5.5 is already an insurance value, it is acceptable to put it on the X51A project.

In comparison, the risks Collinger is worried about lie in another area.

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

"What about simulating working conditions under actual conditions? Especially after the ignition process, what are the differences between the combustion characteristics of propellant under pressure conditions compared with ideal environments?"

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

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

"Already tested."

Brink turned back a few pages of test results. Above was 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 whole band of the spectrum. Among them, the intensity of the characteristic peaks of aluminum and aluminum oxide decreases significantly, indicating that applying additional pressure may reduce the formation of Al vapor and AlO groups, which means that the metal in the propellant will The complete combustion of fuel aluminum plays a certain hindering role. From a quantitative point of view, the magnitude of this impact is not large. For example, at 15 atmospheric pressures, the propellant samples with No. 3 and No. 4 ratios only reduced the energy release by less than 1.5%, while the reductions of No. 1 and No. 2 The amplitude is larger, but it is less than 3%, and it is obvious that this effect will weaken as the diameter of the aluminum particles decreases..."

Collinger did not express his position immediately, but only lowered his head, looking thoughtful.

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

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

Higher speeds, total temperatures and pressures require more capable ultra-high speed wind tunnels.

Neither Boeing nor NASA have the equipment on hand that meets the requirements.

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

Seeing 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 director in a short period of time, the ability to observe people's emotions is bound to be the same.

"Although tests with a higher degree of reduction are not yet available, Dr. Hurst has fitted a semi-empirical and semi-theoretical relationship curve based on the existing test data and the 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. When the working pressure further increases, the trend of the curve has become flat and basically does not change after 15 atmospheres..."

In engineering projects, for parts where the theoretical principles are unclear or cannot be fully considered due to limitations in computing power, it is a common method to perform simulations based on partial test results.

Boeing has indeed been at the forefront of the world in this field for a long time, but it has only been gradually surpassed by rising stars from across the Pacific in recent years.

Therefore, Collinger does not reject this conclusion subjectively.

However, compared with the actual test where one is one and the other is two, the accuracy of the simulation results is highly dependent on the operator's own thinking and ability. Knowing the situation indirectly through technical documents like this still makes him feel a little unsure.

"Where is Dr. Hester himself now?"

After thinking for a moment, Collinger asked:

"I hope to have a face-to-face chat with her about the outcome."

Brink was stunned for a moment:

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

Collinger frowned slightly.

Since the cooperation between the two parties began at the beginning of the year, he had only met Dr. Mellie Hurst once when the research project was initiated.

Although researchers at this level are busy people, and it is normal for them to have several projects on hand at the same time, it has been like this for most of the year, which still makes Collinger groan.

Fortunately, at this time, Brink quickly continued:

"But Dr. Daniel Jablonski, who has been in charge of the work here, is at the ultra-high-speed optical testing center next door. If you have any questions, you can contact him..."

At this point, Collinger could only nod his head, then stood up and took the coat draped on the back of the chair.

But just before going out, he suddenly stopped and looked back at Brink:

"That's right, Charlie."

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

The latter was currently immersed in sorting out the test results that had just been messed up. He hesitated slightly after hearing this sentence:

"If we want to submit an interim report, we must give a more specific timetable..."

Collinger raised his hand to rub his swollen eyebrows, and at the same time went through the recent situation in his mind as quickly as possible -

Although there are still some imperfections, there is generally more optimistic news.

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

(End of chapter)