SpaceX Starship Space History: Physics Doesn't Say It's Impossible

In the vast journey of space exploration, October 13, 2024 has become a milestone day. The fifth test flight of the Starship conducted by SpaceX has attracted global attention with its stunning feat of "chopstick picking rocket". This success marks another important breakthrough for SpaceX in rocket recovery technology and paves the way for Musk's Mars dream. At the same time, Musk's unique celebration on the X platform conveyed the immense pride of the SpaceX team and their unwavering belief in the future to the outside world.

This is not only a technological victory, but also a new starting point for human space exploration. Through the first successful capture of the "Chopsticks" robotic arm, SpaceX has demonstrated the perfect collaboration from technology to market, which will directly affect the future pattern and direction of commercial aerospace.

If SpaceX's Falcon 9 recovery rocket is compared to a pencil, the technical difficulty from launch to return is equivalent to flying the pencil over the top of the 453 meter high Empire State Building and landing it precisely on a landing site the size of a shoebox.

The heavy transport system starship that took over from Falcon 9 has set a more extreme goal: to firmly grip this small pencil with a pair of chopsticks.

If the robotic arm stably catches the thruster, it can reduce the damage to rocket components during landing. After simple maintenance and refueling, the rocket can quickly return to work and improve launch efficiency.

After the Starship test flight began in 2023, SpaceX's first three test flights ended with two explosions and one loss of contact. The fourth test flight in June this year saw the starship achieve a "soft landing" on the sea surface after flying for one hour.

In an interview in July this year, Musk confidently predicted that the fifth test flight had a high chance of success because 'we did not violate physics'.

Physics has rewarded Musk. On October 13th, during the fifth test flight of the starship, the massive robotic arm successfully gripped the rocket's booster Super Heavy - with a height of 69 meters, a diameter of 9 meters, an empty weight of 200 tons, and a full load weight of 3600 tons. From then on, the history of human spaceflight entered a new chapter, and the "space bus" is no longer an unattainable fantasy.

In 2023, SpaceX successfully completed 98 rocket launches, accounting for 44% of the world's total launches; These 98 missions launched the 1984 Starlink satellite and put 1600 tons of payload into the designated orbit, accounting for 80% of the global payload.

The best part is having no parts

Space launch generally consists of two parts: carrier rockets and spacecraft (satellites, space stations, deep space telescopes, etc.) sent into space.

Launch vehicles are the power source for aircraft to escape from Earth. In the relatively short history of human space exploration, launch vehicles have always been disposable consumables. After completing the transport mission, it will fall into the atmosphere and burn up.

Analogous to the civil aviation industry, it's like a plane that crashes in place immediately after transporting passengers to their destination.

A one-stage launch vehicle with no return will account for more than 50% of the launch cost, and no commercial organization can afford such a cost. Therefore, space launches can only be funded by government finances and entrusted to specific contractors to undertake launch tasks.

Musk's idea is actually very simple: to enable rockets to be launched repeatedly while making them as large as possible, carrying enough things at once, and greatly diluting the transportation cost per kilogram.

The first product of this idea is not a starship, but NASA's "Space Shuttle Program". The original intention of designing the space shuttle was also to achieve the reuse of launch systems, but the idea was to rely on aerodynamics - that's why it looks like an airplane.

At present, SpaceX's Falcon 9 is the only rocket in the world that has achieved large-scale reuse, and its recovery technology is quite mature. But Musk believes that the cost of the Falcon 9's landing gear vertical landing plan is still too high, so he simply uses chopsticks to clamp the booster.

The starship system is equipped with 33 booster engines, capable of delivering over 100 tons of payload into a predetermined orbit, which is five times that of the Falcon 9. Musk believes that one day it will take 100 passengers to Mars.

Physics doesn't say it's impossible

Musk's first principle: Only physical rules cannot be broken, any standard, common sense, or traditional framework can be broken.

Physics does not stipulate that stainless steel cannot ascend to the sky.

Musk briefly summarized why SpaceX's starships use stainless steel when asked at a joint meeting of the National Academy of Sciences in the United States.

Carbon fiber: In the early stages of development, carbon fiber was used, but the following problems were encountered.

$130 per kilogram is a very expensive material.

2. Carbon fiber is porous, and the fuel tanks and oxygen tanks of starships are pressurized in gas, using methane and pure oxygen, respectively. If the heated pure oxygen encounters carbon fiber, it is likely to react and burn with the resin and carbon in the carbon fiber. Therefore, an inert lining needs to be added to the container to prevent leakage, which increases the difficulty and cost of research and development.

3. The diameter of the rocket is nine meters. If carbon fiber is used, it will be wrapped in layers ranging from 60 to 220 depending on its location. So in the process of packaging, it is necessary to be accurate and correct, while also addressing the generation of bubbles The problems that usually need to be faced, such as partitions.

The diameter of the starship is nine meters, and the booster is 70 meters long, which is very huge. In order to achieve good performance of carbon fiber, it is necessary to manufacture an extremely large high-pressure reactor, which is also a very tricky problem.

During re-entry, due to high temperatures, the strength of carbon fiber decreases linearly when it exceeds 200 degrees, requiring thick insulation tiles, which increases the overall weight.

Aluminum lithium alloy: When the progress of carbon fiber was slow, it was replaced with the aluminum lithium alloy of Falcon 9.

$40 per kilogram is still not cheap.

SpaceX has introduced a friction stir welding technology in rocket production, the core of which is to use high-speed rotating nose friction metal plate connections to fuse crystalline structures together. This material is difficult to weld and requires friction stir welding technology.

When the strength of this alloy exceeds 200 degrees, it will decrease linearly like carbon fiber, so it also requires thick insulation tiles to increase weight.

301 series stainless steel: During the research and development process, 301 stainless steel was used, but due to the low-temperature liquid storage required for fuel methane and oxidant pure oxygen in starships, and the problem of easy fracture and insufficient toughness in low-temperature environments, 301 series stainless steel was ultimately abandoned.

304 series stainless steel: The problem has been improved to a certain extent, but it has not been completely resolved, so SpaceX independently developed 30X stainless steel.

30X Stainless Steel: SpaceX's self-developed alloy, even better than the 304 series. Here are his strengths.

1. Strength issue: In low-temperature environments, the strength of stainless steel will increase significantly, twice that of room temperature. Therefore, cold processing is carried out in a low-temperature environment, and the final strength is similar to that of advanced carbon fiber and aluminum lithium alloy.

2. The disadvantage of 301 series not having sufficient toughness and being prone to fracture in low-temperature environments has been solved by 30X, which has good toughness and elasticity.

3. The thickness of stainless steel is sufficient, only one layer is needed, and processing only requires rolling and pressing in a low-temperature environment.

4. In high-temperature environments, compared to carbon fiber and aluminum lithium alloy at 200 degrees, stainless steel has sufficient strength at 800 degrees or even 1000 degrees. Therefore, insulation tiles are very lightweight and only need to be laid on the windward side, without the need for insulation tiles on the leeward side, which reduces weight to a certain extent.

5. Due to various reasons, the reduced weight results in a lower total mass of the stainless steel arrow body compared to carbon fiber.

When the Falcon Heavy rocket was first launched, it was loaded with a Tesla sports car for load testing. The launch was successful, and Musk optimistically predicts that this sports car can drift in orbit between Earth and Mars for billions of years.

Finally, it will come extremely close to Mars, with a tiny chance and extremely slim hope of landing on Mars.

Many SpaceX engineers entered the space industry inspired by a book published in 1998, 'Rocket Boys'. Author Homer Hickam has worked as a NASA engineer, responsible for astronaut training, and participated in maintenance missions for the Hubble Space Telescope.

This book was adapted into the movie "October Sky" in its second year of publication, telling the story of Homer Hickam, as the child of a coal miner, who became interested in space exploration. He test fired 31 "self-developed" rockets in his hometown town and later won the championship at the National Science and Technology Expo.

There is a dialogue in the movie that takes place during a dispute between Homer Hickam and his friends, who are preparing to give up the competition.

The protagonist's friend asked: To be honest, what are the chances of our group of coal mine kids winning the science exhibition?

The protagonist said, 'One in a million.'.

My friend said: Is it that high? Why didn't you say it earlier.

There are many reasons for the advancement of technology. One important reason is that there are always some people who consider a one in a million probability as a reason worth pursuing for a lifetime.