Chapter 1241: Boosting Phase Extension

"new technology?"

Shapur Klinger frowned slightly:

"What do you think."

As an old-school engineer, he does not reject new technologies themselves, but he does not want to create any complications beyond the original plan.

From an engineering perspective, every change to the R&D plan midway means the introduction of new uncontrollable risks. Even if extra time and money are spent, it is difficult to ensure that the overall reliability performance will return to the original level.

If there were a few more accidents in the middle, there would be no way to end it.

If you want to speed, you can't reach it.

However, once the delay is too long and the external environment changes, Party A will naturally make new demands, which in turn will force Party B to modify the R&D plan again, forming a vicious circle.

As a result, it is easy for the project to become an unfinished project with huge sunk costs.

Therefore, Collinger's original plan was to modify the waverider-like aerodynamic shape of the X51A in the front section to reduce the resistance during the initial acceleration process, while optimizing the outer shell structure to reduce the overall weight of the aircraft.

In this way, without changing the core power system, the entire flight body can reach a speed of Mach 5.5 before jettisoning the booster, ensuring the success rate of starting the SJX61-1 scramjet engine.

However, although this method has the least risk, it does not leave any room for shortcuts.

A lot of numerical calculations and wind tunnel tests are required to ensure the aerodynamic and structural balance after modifications.

But the problem is that NASA's hypersonic wind tunnel only has the gas flow rate that meets the requirements. The total airflow temperature and the duration of a single test are not enough to fully restore the actual hypersonic flight conditions.

Judging from the current situation, I am afraid it will not be possible to meet the new requirements from above.

All I had to do was listen to Charlie Brink's advice.

The other person is almost 20 years younger than Collinger and is a rising star who only entered the hypersonic project in 2001.

Like many researchers of the same age, there is still a gap between my basic skills and those of the older generation, but I am better off with more flexible thinking.

The higher-ups originally assigned Brink as Collinger's deputy with the idea of ​​learning from each other's strengths and weaknesses.

The former was obviously well prepared and answered almost without thinking:

"The time given by the higher-ups is very tight. There is definitely not enough time to temporarily modify the aerodynamic and structural design of the waverider-like body. If we simply extend the booster stage, it will increase the weight and may not bring enough benefits. Secondly, we will also need to rewrite the flight control system, which is equivalent to affecting the entire system."

"Therefore, a simpler and more effective way is to directly modify the booster stage to obtain stronger propulsion performance while keeping the volume and weight distribution unchanged, so as to ensure that the speed at the end of the booster stage can meet the start-up requirements of the scramjet engine."

This idea is indeed simple.

As the saying goes, bricks fly with great force.

It is also very much in line with Boeing’s fine tradition.

However, Ke Lingjie's frown did not relax at all:

"In my experience, simplicity in engineering usually means complexity in technology."

He said with the tone of a person who has experienced it:

"Although the design indicators of X51A are radical, in fact, most of the project's technologies have been verified in different forms in the past. What really determines success or failure is the power system composed of solid rockets and scramjet engines."

"In order to meet the thrust and working time requirements under hypersonic conditions, SJX61-1 has been set to a very extreme working limit. The reason why we chose the ATACM power section as a booster was also out of safety considerations. If we rashly improve it now, the accumulated risks..."

In fact, in addition to the above concerns, Ke Lingjie has another reason that he never made clear -

Like most of his colleagues in aircraft design, his research in the field of aviation propulsion is not very in-depth.

The X51A's scramjet engine is also developed and produced by Pratt & Whitney.

But this was decided when the project was first launched. It is a single project contractor with a status equivalent to Boeing, and the two parties have a cooperative relationship recognized by Party A.

The booster stage was a borrowed part of the aircraft and was handed over to Collinger's technical team for integration.

It’s integration, not R&D.

Now that the project is halfway through, it is simply not feasible to overturn the contract and add another single project contractor.

Therefore, if we want to make something out of solid rockets, we can only go through the process of subcontracting at various levels.

Collinger is old-fashioned and really doesn't like the feeling of potentially losing control at any time.

More importantly, if anything goes wrong with this type of subcontracted work, he, the party B in the contract, will have to take the blame.

However, Brink was very positive about this matter and was not discouraged by Collinger's hesitation:

"Mr. Supervisor, according to our previous test results on the booster stage, the ATACM power stage uses a larger loading ratio, so the actual effective working time can even be extended to more than 40 seconds."

As he spoke, he even pulled out a printed copy of the test results from somewhere, clearly coming prepared:

"However, at the end of the solid rocket engine's operation, there will be strong and irregular pressure oscillations in the combustion chamber, accompanied by a rise in the average air pressure... In order to avoid this unstable working curve, we limit the working time of the boost phase to 29 seconds."

This test was a task that Ke Lingjie personally assigned a few months ago. He still had a deep impression of it, so he quickly grasped the other party's intention:

"You mean to extend the working hours of the boost phase?"

Brink nodded and was about to speak when he heard the other party change the subject:

"No... no."

Ke Lingjie pointed to the rising air pressure curve 30 seconds later on the graph:

"After 30 seconds, although the booster stage still appears to be functioning normally, the coupling of the fluctuating heat release rate during propellant combustion with the pressure oscillations may have amplified the pressure amplitude."

"I have seen the design of the Army's tactical missiles. They are relatively simple in structure and thick in texture, so they are not sensitive to this kind of shock. However, the X51A is too fast and has little structural redundancy. It is very likely that the engine will deviate from the design state or even disintegrate..."

Brinker took this opportunity to jump in directly:

"But sir, what if there is a way to ensure that the solid rocket motor continues to burn stably within 30-40 seconds... or in other words, there will only be a certain amplitude of pressure fluctuations without an increase in the average air pressure?"

Ke Lingjie was not angry at being interrupted, but just looked surprised:

"Ah?"

Then, he looked at the deputy with a suspicious look:

"I know that you conducted research on solid rockets for a period of time before joining the company, but the unstable combustion of double-base propellants has been a difficult problem that has not been completely solved for decades. Just by asking, you can directly extend the stable working time by one third..."

He had just speculated in his mind that Brink might suggest that he add a high-energy oxidizer, such as RDX or Octogen, to the composite propellant to increase the energy of the propellant.

But I never expected that it would be this kind of plan.

Of course, extending the working time of the boost phase does have minimal impact on the overall design of the X51A...it can even be said that there is almost no noticeable impact.

The additional workload was just to modify a few small modules in the flight control system related to the start of the scramjet engine.

It's something that can be done in a few dozen man-hours at most.

Seeing that Collinger was still questioning but his attitude had obviously changed, Brinker quickly took out a new page of charts:

"Boss, look, according to the current calculation results, the booster stage can accelerate the aircraft to about Mach 29 after working for 4.9 seconds. If it can be extended for another 10 seconds, it will definitely reach a separation speed of Mach 5.4-5.5... And we don't even need to recalibrate this engine. We just need to set a trigger gate to automatically jettison the booster stage after detecting that the speed exceeds Mach 5.5!"

Having said that, he lightly flicked the edge of the paper in his hand, making a crisp "click" sound.

The former had no other choice at the moment, his expression changed for a long time, and finally he gave in helplessly:

“What are the specific technical solutions?”

At this point, Brink knew that although the matter had not yet received final approval, it was already a sure thing.

"This technology was developed by Dr. Mellie Hirst of the Massachusetts Institute of Technology. We may need to contact her for specific details."

He replied:

“In general, the goal is to introduce metals…or more specifically, aluminum oxide nanoparticle catalysts into the conventional AP/HTPB dual-base solid propellant to optimize the burning rate ratio between the two solid fuel particles and to improve the level of linearization of the thermal feedback and burning rate on the propellant surface.”

This explanation was quite logical and had largely eliminated Colin's concerns.

As for more specific content, as Brink just said, we must discuss it in detail with the technicians who are actually responsible for the research.

"All right……"

Ke Lingjie finally gave in:

"How should we contact Dr. Hurst?"

"I have her business card here..."

Brink pulled out his wallet and pulled out a small, beautifully printed card:

"But in this case, they are still the ones who have taken advantage, so I will let them contact us and send us more detailed technical information."

Similar to the situation in all other industries, subcontractors will definitely be treated as grandsons by the general contractor.

Ke Lingjie didn't like subcontracting, but that didn't mean he didn't understand the twists and turns involved, so he just took the business card and glanced at it casually:

"Tell them to contact the legal department as soon as possible regarding the subcontracting contract..."

He originally wanted to say that he would try to share some of the risks through subcontracting contracts.

If something goes wrong, I can't let myself take the blame alone.

But he was halfway through his words when he stood there staring at the business card in his hand.

After hesitating for a moment, he expressed his thoughts:

"This Dr. Hester...seems to be much younger than I thought..."

Then he quickly added:

"Of course I'm not saying that a young lady can't achieve outstanding research results, but she looks like she just graduated from college..."

Halfway through his speech, Collinger looked up at Brinker:

"I remember that you completed all your degrees at Cornell University. How come you know a PhD from MIT who is not very famous?"

The latter obviously did not expect to be asked such a question, and a trace of confusion flashed across his face.

Logically speaking, this is a private topic and you don't need to answer it.

But after all, it is related to the project, so I explained:

"My doctoral advisor later moved to MIT, so she can be considered my junior to some extent. This research topic on new composite propellants was also shared with me by my advisor some time ago."

This explanation made sense, so Ke Lingjie didn't bother with the details any more and just put the business card in his pocket.

"I hope to meet with her within a week... preferably with your tutor. Some things are hard to explain over the phone or email alone."

"Okay, I'll contact you right away!"