Hyperloop is dead. Don’t cry. We can build something better!
It is 10 years since Elon Musk released his technical proposal for Hyperloop in August 2013. Unfortunately, there is no single track in use till today. I think that the concept is dead and there actually might be a better alternative. I call it the Hyper-Tunnels system.
What were the hyperloop expectations?
The traditional bullet trains are expensive to build (200 mil. USD per Mile) and operate. They took a lot of land, are influenced by weather conditions, and are relatively slow compared to airplanes. The tracks also take decades to be built (unless you live in waste countries like China).
So the hyperloop was a fresh idea reenergized by Elon Musk by releasing an alfa design concept paper. It promises much cheaper and faster method of transport than bullet train. And he definitely attracted a lot of attention and organized several student competitions. A few startups started working on the solution and raised significant capital. It looks very optimistic that we would be able to enjoy a ride soon.
What should be hyperloop much more efficent?
The law of physics would help to answer that question. Every transportation vehicle's speed is determined by its ability to overcome some rolling resistance and a force of drag caused by the air.
At high speeds, the force of drag dominates. It is determined by the square of the speed of the vehicle, fluid (air) density, drag coefficient, and cross-section area (Fd = 0.5 x density x speed² x Cd x A)
So to reduce the force, the fast trains have very aerodynamic shapes, like bullets, to reduce the drag coefficient Cd. A person standing will have Cd ~ 1.2. An aircraft with a streamlined body shape would achieve Cd ~ 0.024. The typical car will have Cd ~ 0.4, and the best modern cars would have slightly below Cd ~ 0.2. The sleek design of Aptera has impressively low
drag coefficient of 0.13.
However, the hyperloop concept was optimizing another parameter to reduce the force of drag. It was the air density. The proposed low-pressure tube (100 Pa) would reduce the drag by 1000x. So the train could go much faster using the same force.
I was personally looking forward to a new means of transport after speaking with the student team in Munich, which achieved the fastest hyperloop record of 463 km/h (288 mph) in July 2019. I even bet with a friend that there will be a public test drive by 2021. My hopes were focused on the World EXPO Conference 2020 in Dubai. Unfortunately, I lost my bet. Only a couple of people from Virgin Hyperloop made a very short test ride.
Why the concept didn’t take off?
There are probably many reasons besides the global pandemic.
Firstly, it is hard to build the tracks to achieve so high speeds — the tube turning radius will need to be enormous. A new sufficient tunneling technology, like being developed by The Boring company, would be required. Also, these types of publicly funded projects are slow to implement. However, I think that the risk of people traveling in a practical vacuum might be the key one.
We have some emergency oxygen in the airplanes. However, if anything happened to the pod structure inside the tube, all people onboard would most likely die. Unless they would wear a space suit like astronauts.
It is also a technical challenge to keep thousands the low pressure in thousands of kilometers. They will need to segment while keeping the pods in and out at incredible speeds. Any small imperfection might make the tube implode with the power of a few tons of TNT. Perhaps that is why Virgin Hyperloop recently refocus from passengers to cargo transport.
Could we make it safer and more efficient?
Let’s abundant the idea of reducing the air pressure. Several other parameters of the drag force equation (Fd = 0.5 x density x speed² x Cd x A) could be optimized.
Firstly, we could make the cross-section area A smaller. I was fascinated when I learned about the Volkswagen 1-liter car, named L1, which was first shown to the public at the 2009 Frankfurt Motor Show. The goal of VW was to build a car with a fuel consumption of 1 liter of petrol per 100 km. L1 was a two-seater tandem concept with a frontal area of just 1.02m2. That is less than half of a small sedan like the Tesla Model 3, which has around 2.2 m2. That is 55% less energy assuming about the same Cd (the drag coefficient).
It would actually be much more economical, to have people sitting one after each other than next to each other. However, except for motorbikes and small city vehicles, it is not a popular choice now. People want to have conversations during the long journey. That could be solved by self-driving capability when the driver seat could rotate by 180 degrees and the passengers will enjoy the face-to-face conversation.
Secondly, we could reduce the speed v. I mean not the speed of the car, but the speed of the air the car faces. Imagine that we would create a one-directional wind in the tube. A big ventilator will be placed at the exit of the tube pumping the air from the tube. Yes, we could eventually reduce the pressure a bit, but the main goal will be to create a constant airflow. To achieve a wind speed let’s say 30-40 meters per second ( ~ 108-145 km/h, 67-90 Mph), we need to reduce the air pressure by just about 1% (negligance the elevation difference). The ventilator will need to move about 50–100 kg of air per second, which is perfectly achievable and requires a few tens of kW of power. To keep the pressure, the car might need to slow down and go through the parallel narrow tunnel around the ventilator with plastic shades or a pair of sliding doors to avoid unnecessary pressure loss.
As a result, we could achieve high system efficiency and speed. Imagine that we could either drive at 145 km/h with very little force (just the rolling resistance) or double the speed of the car. The round shape of the tunnel will allow to swipe the tunnels curve at blazing speed of 290 km/h.
If we would drive an electric car that fast, we will very quickly drain its battery as we will need 4x more energy than driving at 145km/h and 9x more energy than driving at 96 km/h. However, 75% of energy is saved with the air velocity effectively reduced to half.
Hyper-Tunnels design
The Hyper-Tunnels will consist of a network of pair tubes/tunnels between cities with a big ventilator creating constant wind in the direction of the travel. Each city will have multiple main stop stations allowing fast onboarding.
We will use small electric cars (pods) specifically designed to fit into these tunnels. They will be recharged at their destinations. The reasonable-size batteries of 20–30kWh would allow fast travel for journeys to up to 1000 km (621 Miles) in 3 hours.
That is the distance, where hyper-tunnels will provide the optimal choice for the trip from time (faster than airplane) and cost perspective.
What are the key benefits of the Hyper-Tunnels system compared to the Hyperloop:
- We have everything we need to build it today. We don’t need to design and test complicated vacuum-resistant pods. We can just adopt the small electric cars manufactured today and build 1–6 seater pods like this Colibry concept. The car pods could be owned and maintained by the operator of the hypercar-pod (either a public or private company). We will just pay for each ride.
- The car pods will be equipped with a simple self-driving system, which will be connected to the central system. Each city will have several stations for people to onboard. Eventually, the car pods could pick up the people at their homes making the whole journey extremely comfortable and providing an additional time saving.
- We can use regular tunneling technology or an existing system to build the tubes/pipes. Many road tunnels are already tens of kilometers long nowadays. Thanks to the small dimensions of the car pods, the tunnel diameter of ~2m should be sufficient. It can be partially underground or above the ground to reduce the cost of construction.
- There will be a strong wind in the tunnel, but nothing life-threatening. The system will be safer than traditional highways. The section doors would allow to stop the wind very quickly. People can get off the car and walk to safety exits. Pod could pass one each other in case some emergency happens.
- The system will also be weather-resistant and maintenance less. The above-ground part of the system could be thermally insulated. Airless tires could be used. The dual-engine car pods are self-propellant so no complex infrastructure to fail.
- The setup cost will be 5–10% of the cost of the bullet train track.
The cost of the pods is relatively small (30–40k USD each) and we will need a few thousand. The majority of the cost will be the tunneling, which is estimated to be 5–10 million USD per mile (Thanks to the small diameter of the tube and simple support infrastructure). - A single tube can have the capacity to move up to 20.000 people per hour. That is equivalent to 20–40 trainsets! Computer-controlled pods could be separated by a few seconds (like cars on the highway). You can also travel at any time as the number of pods waiting and available for the passengers.
- The system will have superior energy efficiency. Even with the high speeds, the energy requirements will be 2–3kWh per person per 100km in the form of electricity even for high speeds. That is a fraction of the energy needed for an aircraft and much lower than the current gas car or even the best electric cars.
It seems that the original Hyperloop idea will not be realized. But perhaps we could build something better — the Hyper-Tunnels!
Please like and share this concept. So we can all travel faster, safer, eco friendly and cheaper.
