Elon Musk has finally revealed his plans for the Hyperloop.
The Hyperloop is Musk’s plan for a new transportation system that’s faster and cheaper than a high-speed train.
He released a 57-page PDF that outlines his plan for the Hyperloop. That PDF is embedded below.
Here are the highlights of his plan for the Hyperloop:
- Musk thinks that high-speed trains are too expensive, and too slow. He wants a system that’s faster and cheaper.
- Musk says the Hyperloop is best for distances of 900 miles. Beyond 900 miles, he thinks you’re better off in a supersonic jet.
- Musk shoots down previous ideas about how something like a Hyperloop could work. He says vacuum sealed tubes running on magnetics wouldn’t work because it’s too hard to vacuum seal a 700-mile tube. One leak, and you’re toast. Pneumatic tubes wouldn’t work, either, because ” the friction of a 350 mile long column of air moving at anywhere near sonic velocity against the inside of the tube is so stupendously high that this is impossible for all practical purposes. “
- He proposes ” a low pressure (vs. almost no pressure) system set to a level where standard commercial pumps could easily overcome an air leak and the transport pods could handle variable air density would be inherently robust.”
- He wants people to sit in pods that whip through giant steel tubes. ” Sealed capsules carrying 28 passengers each that travel along the interior of the tube depart on average every 2 minutes from Los Angeles or San Francisco (up to every 30 seconds during peak usage hours).”
- An in-depth explanation: ” Hyperloop capsules will float above the tube’s surface on an array of 28 air bearing skis that are geometrically conformed to the tube walls. The skis, each 4.9 ft (1.5 meters) in length and 3.0 ft (0.9 meters) in width, support the weight of the capsule by floating on a pressurized cushion of air 0.020 to 0.050 in. (0.5 to 1.3 mm) off the ground. Peak pressures beneath the skis need only reach 1.4 psi (9.4 kPa) to support the passenger capsule (9% of sea level atmospheric pressure). The skis depend on two mechanisms to pressurize the thin air film: external pressurization and aerodynamics.”
- There is danger in his approach, because: ” Whenever you have a capsule or pod (I am using the words interchangeably) moving at high speed through a tube containing air, there is a minimum tube to pod area ratio below which you will choke the flow. What this means is that if the walls of the tube and the capsule are too close together, the capsule will behave like a syringe and eventually be forced to push the entire column of air in the system. Not good. “
- His solution to this problem: ” Mount an electric compressor fan on the nose of the pod that actively transfers high pressure air from the front to the rear of the vessel. This is like having a pump in the head of the syringe actively relieving pressure.”
- He believes the Hyperloop will cost $7.5 billion at most. The $7.5 billion estimate for a pod+cargo version. For just passengers, he thinks it’s only $6 billion. The pods and linear motors will cost hundreds of millions. The tube will cost billions. For comparison, the California high-speed rail project is projected to cost $70-$100 billion.
- It will be built above ground on pylons, and the prefabricated sections can be dropped into place. By building it above ground, it can mostly follow I-5, and it won’t take up too much land. He actually suggests putting it in the median of I-5.
- It will be self powered. It can have solar panels of top of the tube which will generate electricity. He also says, ” The energy could also be stored in the form of compressed air that then runs an electric fan in reverse to generate energy, as demonstrated by LightSail.”
- It will carry 840 passengers per hour, taking them from Los Angeles to San Francisco, and vice versa. He says, “t he current baseline requires up to 40 capsules in activity during rush hour, 6 of which are at the terminals for loading and unloading of the passengers in approximately 5 minutes. ” (Um, 5 minutes for unloading?)
- He also has a model for a passenger + car version of the Hyperloop pod. It could take people plus three cars.
- Inside the pods, Musk says the chairs will be super comfortable, and a “beautiful landscape will be displayed in the cabin and each passenger will have access their own personal entertainment system.”
- You can only travel with two bags per trip, and the total weight can’t be above 110 pounds.
- He plans on having TSA-like security checks, but hopefully faster and less intrusive.
- What happens if you have a heart attack (or some less serious illness) on the Hyperloop? You’ll be at the station in 30 minutes, so hang on! “All capsules would have direct radio contact with station operators in case of emergencies, allowing passengers to report any incident, to request help and to receive assistance.”
And in conclusion… Musk says there is work to be done. Specifically, these four areas need some kinks ironed out:
- “More expansion on the control mechanism for Hyperloop capsules, including attitude thruster or control moment gyros.”
- “Detailed station designs with loading and unloading of both passenger and passenger plus vehicle versions of the Hyperloop capsules.”
- “Trades comparing the costs and benefits of Hyperloop with more conventional magnetic levitation systems.”
- “Sub-scale testing based on a further optimized design to demonstrate the physics of Hyperloop.”
Here’s a diagram of how it would work:
Here’s the diagram of how fast the Hyperloop would travel. It would top out at 760 miles per hour.
Here’s the in-depth explanation of how it would work:
“Whenever you have a capsule or pod (I am using the words interchangeably) moving at high speed through a tube containing air, there is a minimum tube to pod area ratio below which you will choke the flow. What this means is that if the walls of the tube and the capsule are too close together, the capsule will behave like a syringe and eventually be forced to push the entire column of air in the system. Not good.
Nature’s top speed law for a given tube to pod area ratio is known as the Kantrowitz limit. This is highly problematic, as it forces you to either go slowly or have a super huge diameter tube. Interestingly, there are usually two solutions to the Kantrowitz limit – one where you go slowly and one where you go really, really fast.
The latter solution sounds mighty appealing at first, until you realize that going several thousand miles per hour means that you can’t tolerate even wide turns without painful g loads. For a journey from San Francisco to LA, you will also experience a rather intense speed up and slow down. And, when you get right down to it, going through transonic buffet in a tube is just fundamentally a dodgy prospect.
Both for trip comfort and safety, it would be best to travel at high subsonic speeds for a 350 mile journey. For much longer journeys, such as LA to NY, it would be worth exploring super high speeds and this is probably technically feasible, but, as mentioned above, I believe the economics would probably favor a supersonic plane.
The approach that I believe would overcome the Kantrowitz limit is to mount an electric compressor fan on the nose of the pod that actively transfers high pressure air from the front to the rear of the vessel. This is like having a pump in the head of the syringe actively relieving pressure.
It would also simultaneously solve another problem, which is how to create a low friction suspension system when traveling at over 700 mph. Wheels don’t work very well at that sort of speed, but a cushion of air does. Air bearings, which use the same basic principle as an air hockey table, have been demonstrated to work at speeds of Mach 1.1 with very low friction. In this case, however, it is the pod that is producing the air cushion, rather than the tube, as it is important to make the tube as low cost and simple as possible.
That then begs the next question of whether a battery can store enough energy to power a fan for the length of the journey with room to spare. Based on our calculations, this is no problem, so long as the energy used to accelerate the pod is not drawn from the battery pack.
This is where the external linear electric motor comes in, which is simply a round induction motor (like the one in the Tesla Model S) rolled flat. This would accelerate the pod to high subsonic velocity and provide a periodic reboost roughly every 70 miles. The linear electric motor is needed for as little as ~1% of the tube length, so is not particularly costly.”
Here’s a chart from Musk on how much cheaper it is per person to travel via Hyperloop:
Here’s where the Hyperloop will go:
Here’s the full PDF of the announcement:
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