On May 29, according to foreign media reports, from a physical point of view, the "hyperloop" envisioned by elonmusk, CEO of Tesla, is feasible, but in the actual construction process, it faces three huge engineering challenges, namely, the problem of gravity, the laying of vacuum pipelines and how to prevent disaster events.
In the atmosphere, the speed of almost every vehicle is limited by air resistance, and lowering the air pressure can make them move faster. Put the high-speed train into a vacuum pipe, and it can run at a speed close to the speed of sound. This is the concept of "super high speed rail" envisioned by musk.
In fact, this idea is not new. Similar proposals were put forward centuries ago. Physicists think this idea is feasible, but engineers point out that there are many thorny problems in actual construction. Fortunately, there may be a way to solve such engineering problems.
At present, Musk's super high-speed railway mainly faces three types of challenges:
- Gravity problem
Human beings have limited tolerance to acceleration, which is called gravity. Acceleration is more than just stepping on the accelerator. It also includes moving forward and turning at a constant speed. So, can you accelerate without making people feel sick or dizzy? Absolutely. The speed of commercial jets exceeds 800 kilometers per hour. Their height keeps rising or falling, and sometimes they even need to reverse the fuselage and be squeezed by the air flow. It takes only a few seconds for them to decelerate from flight speed to taxiing state. Most of the time, however, people don't feel sick or scared. The efficiency of the whole system is amazing. Perhaps the super high speed rail can follow suit.
But there is also a big difference between the two. After all, the plane flies in the air, while the super high-speed rail runs on the ground. There is a lot of work to be done to lay a flat and straight vacuum pipeline, but engineers have done such things before, such as building the Eisenhower interstate highway system, that is, through digging tunnels through mountains, through bridges or undersea tunnels through bays, and flattening the rugged terrain. These engineering challenges can be overcome.
- Vacuum pipe
Super high speed rail is essentially a long, vacuum sealed pipeline. There is almost no air inside, and of course there is no resistance. This is why high-speed trains can travel so fast inside. The speed may exceed 1223 kilometers per hour. However, maintaining this vacuum in a vast space will be a huge challenge. The air pressure inside is about one thousandth of the earth's atmospheric pressure.
Whenever passengers enter or leave the system, the super high-speed rail must be opened briefly. Therefore, the station will need interlocking. Once the passengers get on the train, the vacuum pipe will enter the interlocking state, and the surrounding air will be pumped out. When the inside becomes a vacuum, it opens on the other side, allowing the train to enter the rail.
In order to ensure the integrity of the structure, this huge pipe is likely to be made of steel, rather than the fantasy material seen in the publicity materials. If the steel is welded together, it will greatly prevent air leakage, but it will also expand and contract with thermal changes like a huge iron block. In addition, it will require a lot of engineering design to enable the structure to move freely. On the contrary, if the system is composed of a large number of small steel pipes connected through joints, these joints must be able to maintain the integrity of the vacuum. The project must be perfect, because if a joint fails, the consequences will be disastrous.
- Disaster prevention
There are at least two ways that the super high-speed rail journey could end in disaster.
First, the train may stop for many reasons. As the air supply decreases, passengers may be trapped in deserted places. Perhaps a mechanism can be added to the design of super high-speed rail to break the vacuum in some parts and allow passengers to get off and escape. However, this is not easy, because it may lead to a second disaster scenario.
If the seal breaks, the opening immediately draws in air at an incredible rate to fill the vacuum inside. This will produce an air shock wave that travels along the pipe at a speed equivalent to the speed of sound. If the pipeline bursts at the back, the train will suffer a huge and potentially fatal acceleration impact, and then move forward at a speed of more than 1000 km without braking. If the pipeline fails in the front, the train will also be impacted by the air wave, and the train and everyone inside will be destroyed immediately. Worse, any accident will not only affect a single train. The shock wave will destroy all people and objects inside the super high speed rail.
Engineering may help solve this problem, but it will involve cost and practicality. Will there be many special parts in the vacuum pipe, and large valves can be quickly deployed to maintain the vacuum? Can these special parts withstand the coming shock wave? Or will these special parts become "victims" to avoid a greater disaster?
Finally, the train hitting the pipeline may be enough to burst the latter. Even a small caliber bullet may destroy the entire super high-speed rail system and kill everyone inside. Therefore, the super high speed railway will require a lot of monitoring and safety measures, both inside and outside the vacuum pipeline.
Advantages and disadvantages of super high speed rail
Super high speed rail has many advantages. This will be a faster way to travel, which will greatly reduce traffic related greenhouse gas emissions and help combat climate warming. However, it has many disadvantages, among which how to ensure safety and obtain sufficient construction cost is the most urgent.
It is possible to build super high-speed rail. But, like building settlements on Mars, the biggest question may be how much people need it? (small)