Underwater Braking System with Water Steam
Rongqing Dai
Abstract
Because water surfaces do not have the same friction as solid surfaces and have greater inertia than air, braking in water is much more difficult than braking on land or in the air. This article explores the potential of using microwaves to heat water in a confined space to generate high-temperature, high-pressure steam for constructing an underwater braking system. While the technology discussed could also be used for underwater propulsion as discussed by the author in 2020, its most valuable application is underwater braking, as it will help humans better mitigate risks at sea and in river, thereby reducing the likelihood of tragedies like the sinking of the Titanic happening again.
Keywords: Underwater, Braking System, High Temperature, High Pressure, Steam
1. Brief Background
At 23:40 on April 14 of 1912, the RMS Titanic struck an iceberg, with over 2,200 people on board, one minute after the Lookout Frederick Fleet sighted the iceberg [[1]]. If, within that minute, some emergency maneuvering measures was available to significantly reduce the speed of the ship, even if they cannot prevent a collision, they could at least mitigate the damage when the collision occurred. More than a century has passed, and we still hear of collisions at sea involving modern ships equipped with advanced technology from time to time. Therefore, the world needs underwater braking systems to help better control the speed of ships at sea.
On the other hand, we cannot use friction to stop ships in water as we do on land, nor can we use the repulsive force of jet engines or rocket flames to stop ships in water as we do in the air. Accordingly, the underwater braking system remains virtually a barren land in the modern world.
In 2020 Dai proposed an idea of underwater propulsion with instant evaporation of water (Dai 2020) [[2]]. While similar ideas have been applied to the manufacture of steam rockets used as spacecraft launching assisting tools, it is clear that attempting to use hot steam propulsion to create underwater braking systems will face much greater challenges for various reasons.
In this short essay, let’s delve into some details of the conception for building the underwater braking system with high temperature and high pressure water steam.
2. The Force from High Speed Water Steam
Owing to the significant difference between the drag forces in water and air, we could use the ratio between the multiplications of medium density and the square of moving velocity (ρV2) to get a very rough idea about how big the difference might be, without more involved details such as viscosity and so on.
Assume that we have the hot steam ejected from an underwater container at the speed around the Mach speed of water. Now because we know that the ratio between the Mach speeds of water and air is roughly 1480/340≈4.35, and the ratio between the densities of water and air is roughly 1000/1.225≈816, we could very roughly have the ratio between the hydrodynamic forces in water and in air to be 15,447. This immense difference shows an indication of the order of magnitude of the potential propulsion power we might have if we could use hot water steam at a very high temperature and a very high pressure.
3. A Natural Idea for Positioning the Underwater Braking System
Item (a) of Figure 1 shows a typical side view of the bulbous bow of a ship, which naturally offers an ideal position for implementing the underwater braking system using hot water steam. We will build the internal space of the bulbous bow as the tank for containing water or hot steam when the water is heated up, and partition the tank into 4 quarters as shown in (b) of Figure 1.
Figure 1. (a) The typical side view of the contour of the bulbous bow of a ship; (b) The schematic of the partition of the inner space of the bulbous bow for the tank of hot steam.
The front nose of the bulbous bow will consist of four lids that can be locked close and unlocked open, each with a curved back, as shown in the schematic diagram in Figure 2. Once the lids are locked close, the water or steam inside cannot escape from the tank, and the external shape of the tank will function as a regular bulbous bow for the ship; once the lids are unlocked and the interior space is filled with high pressure hot steam, the lids will be pushed to slide open and the curved shapes on the back of each lid will help it to slide laterally to allow the high pressure steam to be ejected from the tank. After the high-pressure steam inside the partition is released, external water will automatically flow into the partition until it is filled with surrounding water. Then, due to the balance of pressure inside and outside the partition, the lid can be easily slid back and locked again.
The partition of the tank into four compartments as shown in Figures 1 and 2 not only helps to expedite the microwave heating of the water, but also offers flexibility in thrust configuration. For example, when maximum thrust is needed immediately, we can open covers I through IV simultaneously; but when more sustained thrust is needed, we can open covers I and III first, and then open covers II and IV after the fluid in partitions I and III has been used up. Besides, the partition can also help to reduce the asymmetry distribution of water inside the tank due to the influence of gravity.
Figure 2. (a) The schematic side view of the internal of the bulbous bow with front lids; (b) The schematic front view of the half open lids.
4. The Mechanism of Heating up Water
The ideal way to heat water is to use microwaves or any other form of energy that can provide extremely high heating power in a short time.
For underwater propulsion, as discussed by Dai (2020) [2], we need to periodically and rapidly fill empty water containers with water and heat them to high temperature and pressure in order to maintain constant propulsion. However, for underwater braking, we may need the vessel to decelerate, stop, or even reverse immediately. Therefore, underwater braking systems require much greater thrust than underwater propulsion systems, but do not necessarily require very rapid water refilling and reheating mechanisms.
For underwater propulsion, it is impractical to preheat all the water before starting the propulsion engine. However, for underwater braking, we can preheat the entire tank before it is needed, although we still need and can refill and reheat the water once the hot steam in the tank is used up.
5. Final Remarks
Although humans have been using various methods for underwater propulsion for centuries, we still do not have a good underwater braking mechanism to better control the movement of ships in the water. However, the high thrust generated by high-temperature, high-pressure steam can provide a promising mechanism for braking high-speed ships in water, and the combination of modern microwave technology and efficient energy will make this mechanism more feasible than ever before.
Reference
[[1]]Wikipedia. Sinking of the Titanic. Retrieved from https://en.wikipedia.org/wiki/Sinking_of_the_Titanic. Last edited on 22 April 2026, at 14:00 (UTC).
[[2]]Dai,R. (2020). Instant Evaporation ---the future of underwater propulsion. Retrieved from: https://advance.sagepub.com/doi/full/10.31124/advance.13366658.v1