Expansion of the International Space Station, this is a big project.

First of all, ISS is an international cooperation project, and it really lives up to its name.

NACA has a deep background in deep space exploration and space power, but it is not good at building large in-orbit spacecraft.

The reason is also due to the space race of the last century, when Aramco was a little inflated after the Apollo program won the moon landing, and did not care too much about the number of modules in the low-Earth orbit launch zone.

Of course, it's not that NACA isn't interested in carrying out a permanent mission for low-Earth orbiters, in fact, this project is already included in the Space Shuttle program.

The first space shuttle "Columbia" should actually be called a space laboratory rather than a simple shuttle vehicle, its cabin is equipped with a considerable amount of experimental equipment, and there is no later space shuttle open and close cargo compartment, itself can stay in orbit for a long time.

What's more, a space shuttle is also more than a hundred tons, which is larger than the space station at the beginning of the former alliance.

After finding that its national strength could no longer support the moon landing, the alliance chose the construction of a low-earth orbit space station and accumulated considerable experience.

At first, Ami wanted to take his European friends with him, or even do it alone, but due to the lack of experience and the cliff-like decline in funding at the end of the Cold War, he finally had to pull Lucia in.

In recent years, sometimes when the two quarreled, Lucia would say that the ISS would "separate" the ISS, because if ISS did not have the functional support of the Lucia module, it would really not be able to maintain......

Even the expansion is one that can't ignore Lucia's opinion.

Montal spoke privately to the Lucia space agency before the ISS meeting, and the feedback was ambiguous.

Yuri Borisov made a lot of nonsense through RT, and after thinking about it, Montal saw only two words: ask for money.

Lucia Space Agency because of the inability to join the current race to the moon has become a co-opted sweetheart, a few days ago, after the docking of the module jointly developed by Italy and Hair to the Tiangong space station, they also said that they would carry out a series of space station cooperation with China.

Of course, the specific content is also vague, in fact, it is a good idea to sell at a price.

Now the ISS expansion allows Lucia to contribute, but the money has to be paid, even if the main truss part needs to rely on the shuttle.

Montal couldn't do anything about it, and Lucia really got the sore spot, after all, NACA couldn't build another super space station.

But as the Advance gradually took shape in space and got closer to full form, the Senate became more dissatisfied, and the expansion must be necessary.

Not only must it be expanded, but it must also be advanced, even if it can't achieve the terrifying quality of the Advance, at least there must be a shining point that can be promoted.

……

"Four RS25s, or three RS25Es?"

Rockdyne and Boeing's teams got together to discuss engine options for the new Space Shuttle system.

Endeavour has not had a difficult time replacing the three huge RS25 engines with nuclear engines, and JFT has already given the corresponding engine size data that they are actively building, and the difference is not much.

The center of gravity needs to be adjusted a little, but fortunately, Endeavour has been dismantled and only the skeleton is renovated, which can be overcome with the assistance of modern computers.

The problem is in the launch system.

The original Space Shuttle launch system was very special, when the Space Shuttle lay on a huge orange fuel tank to feed fuel to three RS25s in its tail, and two SRB solid boosters were tied to each side of the fuel tank, which together produced about 2,800 tons of thrust.

When the SRB's solid thrusters burned out and separated, the shuttle continued to fly with fuel tanks until it entered orbit.

The RS25 can reach a single thrust (sea level) of 167 tons, obviously the nuclear engine does not have this ability, the advantage of the latter is in the specific impulse rather than thrust, and the FAA will never give the space shuttle to start the nuclear engine on the ground to take off, otherwise the public will have to rush into the Capitol Hill.

The nuclear-powered Endeavour would need to go into space as a payload rather than part of a rocket, like the former Soyuz Buran space shuttle, so the launch system would also need to be significantly changed.

This seemingly difficult problem did not stump the engineers, in fact, in the last century, there were many solutions for changing the STS to pure load transportation, and it was enough to take one out and change it.

The nuclear-powered version of Endeavour still rests on a fuel tank with four RS25 engines, but these four engines are mounted on the other side of the tank, opposite the Space Shuttle.

It is equivalent to moving the four engines of the original space shuttle to the opposite direction, maintaining the total thrust without decreasing.

The four engines are installed in a triangular body with a circular cone, which draws fuel for the engines like a space shuttle, producing a common 670 tons of thrust, and the extra thrust is to offset the dead weight of the new structure and to compensate for the power loss caused by the thrust angle.

With more than 100 tons on each side and a maximum of 10 tons on both sides of the tank, it was clear that the four RS25s needed a larger declination angle and had to tilt the entire assembly once off the ground so that the thrust intersection of the two SRBs and the four RS25s coincided with the overall center of gravity.

In this way, the shuttle is not "leaning back" as before, but "lying forward", and like the H2, lying on the rocket and being sent into space.

This scheme is very similar to the 1125K "Energy" rocket, both of which can carry more than 100 tons of payload on the side of the rocket, and the original purpose was to develop a giant rocket to replace the Saturn V on the basis of the STS.

The difficulty was small, the scheme was pre-studied, and it was quickly determined to be the basic configuration, which became the launch method of the nuclear-powered space shuttle in the future.

Now Boeing and NACA are struggling with whether the four engines on the side of the fuel tank should be reused.

The original purpose of the design of this scheme must have been to take it, after all, the installation of four RS25 triangles in that shape was to re-enter the atmosphere and bring back the four hydrogen-oxygen engines, which were extremely expensive, close to $200 million.

Otherwise, you can directly follow the SLS routine and put it at the bottom of the fuel tank, which can reduce the workload by more than 50%.

But the question is how to recycle the propulsion part, and Boeing now has two options:

The first is to optimize the triangle into a central lifting body, which glides and lands as a deformed miniature space shuttle with an engine;

The second is that there is no wheel splashing into the sea for recovery, and it falls directly into the sea when landing.

Both options have their own advantages and disadvantages, one is safer and the other is more worry-free, but both require more work, and now Boeing, as a giant that continues to swallow up various near-monopolies, has tasted the bitter fruit, it is NACA's main contractor, there are too many tasks, to reduce the workload.

And Rockdyne's attitude also made them more entangled, the cost of a single RS25 is more than 50 million US dollars, and four RS25s are indeed necessary to be recycled;

But Rockdyne added that they had developed a simplified version of the RS25 (disposable), with thrust increased to 200 tons (sea level), an increase in the specific impulse and thrust-to-weight ratio, and a price reduction to just over $20 million, which would be enough for the RS25E.

Is it to increase the workload for yourself and recover $200 million worth of engines, or to save some trouble and fly away close to $70 million at a time?

To reuse or not to reuse, that's a question.

(End of chapter)