The previous upper stage uses poison hair, although the technology is very mature, but the cost is still high, and it is highly toxic, and it is still full of danger during use.

As a technology freak, Yang Jie is naturally dissatisfied with this, and Huaxing Rocket Launch Company needs a lower cost, smaller size, larger load, more environmentally friendly, and more reliable upper stage.

After comprehensive consideration, the technical team led by Ban Zhinong finally chose the upper stage technical scheme of liquid oxygen methane engine and magnetic accumulation arc engine, which is mainly to free up more valuable space for the fairing to pay.

This time, instead of adopting Maozi's previous design scheme of constantly growing tumors on the spherical fuel storage tank, Ban Zhinong adopted a design scheme like a bamboo joint.

Although Huaxing Rocket Launch Company is now relatively mature in liquid oxygen kerosene rocket technology, this liquid oxygen methane engine has natural advantages in reuse and cost, especially for commercial development in space.

Su Xiu and Rabbit were more concerned about reliability in the development of liquid rockets in the upper stage, and they took the poison rocket on the technical route, and there was not much research and development in the technology of liquid oxygen methane engines, while Eagle Sauce has always emphasized high performance in the upper stage, and has been pursuing liquid oxygen and liquid hydrogen engines, and once the technical route is determined, it is more difficult to adjust the route after investing a huge amount of money and a lot of manpower.

Huaxing Rocket Launch Company, as a rising star, and very emphasizes the repeated use and low cost of rocket engines, but it is very flexible in the technical route, so the main technical route is liquid oxygen kerosene rocket and liquid oxygen methane rocket.

In terms of basic rockets, Huaxing Rocket Launch Company cooperates more with Da Mao in technology, mainly using high-power liquid oxygen kerosene rockets.

The poison hair was initially used in the upper stage, and now it has been transferred to the liquid oxygen methane engine.

Before Huaxing rocket launch company used liquid oxygen kerosene rocket, it was also found that the liquid oxygen kerosene engine was more complicated, and the remaining kerosene in the inner cavity needed to be discharged from various outlets, and it was blown out for a long time.

Moreover, in the process of cooperating with Da Mao, Da Mao will naturally not hand over the kerosene refining technology, and will not take out the control technology of flame control and fuel filling in the most critical high-pressure refueling technology.

Da Mao has reached the pinnacle in liquid oxygen kerosene rocket engine technology, Ban Zhinong and others feel that the potential of this technical route has almost been dug up by Su Xiu's group of scientists, which is nothing more than in kerosene refining technology and continue to increase the temperature of liquid oxygen kerosene engines, continue to increase the thrust of the engine, and develop the cleaning technology of the engine without removing the arrow.

If you continue to increase the gas temperature, it is easy to sinter, and the engine is prone to problems, although now Huaxing Technology Group has used technical means to reduce the sulfur content of kerosene to a very low level, and now there is no need to purchase from Damao domestically, but compared to the degree that Su Xiu did before, it is not much improved, but because of advanced equipment to make the cost of this kerosene go up.

Therefore, Ban Zhinong's energy has also shifted to liquid oxygen methane engine technology.

Huaxing Rocket Launch Company has carried out electrical heat transfer tests, coking limit temperature tests, carbon deposition tests and material compatibility tests of methane fuel several years ago.

These experiments show that the methane molecule contains only one carbon atom, and only when the temperature exceeds 1470K, the methane carbon deposition is very small, and the methane combustion products will not appear obvious carbon deposition in the range of 400~900 °C in the generator operating temperature, which is more conducive to repeated use.

Under the turbine simulation conditions, there is no carbon deposition in methane, while there is carbon deposition in kerosene, although the sulfur content of methane is relatively high, there is obvious corrosion of the copper inner wall material, but Huaxing Technology Group has the ability to make the sulfur content in methane reach a very low level.

Due to the high coking temperature of methane, higher temperatures are allowed during the regeneration and cooling of the nozzle interlayer, so the thrust of the methane engine can be higher than that of liquid oxygen and kerosene rockets.

Moreover, if methane is used as fuel, the ignition energy of the engine is an order of magnitude lower than that of kerosene, and it can be ignited with high reliability with electric sparks, while the ignition of liquid oxygen kerosene engines is difficult to start.

In particular, when methane is burned, because of its low viscosity and small molecules, it can even be fully burned like liquid hydrogen, and the combustion efficiency is very high.

Generally speaking, methane and kerosene have the same comprehensive density ratio, but they have a huge advantage in cost.

When a team of scientists, including Eagle Sauce, commented on liquid oxygen methane, everyone's reason was that the specific flush was higher than liquid oxygen kerosene, and the density was higher than that of liquid oxygen and liquid hydrogen. In addition, due to the small temperature difference of liquid oxygen methane, the insulation of the co-bottom tank is easier to achieve.

However, methane is a low-temperature fuel, which requires more heat-proof links, increases the weight of the structure, and the density is only half of that of kerosene, requires a larger storage tank, increases the weight of the structure, and under the same diameter, the same take-off scale storage tank is longer, and the lateral load of the arrow body increases under the same force, and the structure needs to be strengthened.

In addition, the methane saturated vapor pressure is higher, the engine needs more inlet pressure, and the tank needs more boost pressure.

All of the above negates the benefits of methane fuels, which are difficult to fully quantify.

Eagle sauce is in pursuit of high performance, without hesitation to choose the liquid oxygen liquid hydrogen engine, although it is difficult to use, but because of the extremely high performance, they have been developing and using.

And Su Xiu plunged headlong into liquid oxygen kerosene rocket engine technology and created an artifact like RD-170, and now Da Mao is still making various improvements on this basis, and has been lacking sufficient funds for so many years, and it is impossible to come up with a lot of money to toss in liquid oxygen methane engine technology.

Da Mao has also been using poison hair on the upper stage engine, and the design scheme of long tumors is used to continuously increase fuel in order to save research and development costs.

However, Huaxing Rocket Launch Company is not short of money, and Yang Jie also agreed to the technical route of liquid oxygen methane engines in the next one or two decades after listening to the reports of Ban Zhinong and others.

The design of this liquid oxygen methane engine system was very fast, and the small liquid oxygen methane engine was trial-produced step by step after the test run of the gas generator, thrust chamber, semi-system, and the whole system.