This discussion centers on thrust calculation from a high-pressure tank scenario, specifically a tank pressurized to 1000 psi with a one square inch opening. When the opening is created, the pressure differential results in a 1000 lb force acting in the opposite direction, as dictated by Newton's Third Law. The conversation also explores the implications of using air versus water for thrust generation, highlighting that compressed air stores potential energy, while liquids do not, affecting thrust dynamics. A test fixture is being developed to measure thrust using a 4500 psi tank and a two-inch ball valve, with expectations of achieving significant thrust values.
PREREQUISITESEngineers, physicists, and hobbyists involved in fluid dynamics, propulsion systems, or high-pressure testing will benefit from this discussion, particularly those interested in practical applications of thrust calculation and measurement.
If the force on that square inch jet of water is indeed 1000pounds force then Newton's Third law tells you that there is 1000pounds reaction force on the tank. The forces must be equal.bluechipx said:Let's say we have a tank with 1000 psi pushing in all directions, if we remove one square inch from an end, now the tank has 1000 psi more at one end than the other. Does this mean that there is a 1000 lb push in the opposite direction of the removed square inch?
Yes, and that's one way of explaining how a rocket generates thrust in a vacuum where "there's nothing to push against". The combustion chamber of a rocket is basically a high-pressure tank with an opening at the back.bluechipx said:Let's say we have a tank with 1000 psi pushing in all directions, if we remove one square inch from an end, now the tank has 1000 psi more at one end than the other. Does this mean that there is a 1000 lb push in the opposite direction of the removed square inch?
sophiecentaur said:If the force on that square inch jet of water is indeed 1000pounds force then Newton's Third law tells you that there is 1000pounds reaction force on the tank. The forces must be equal.
PS IS someone pumping water into the tank to keep the internal pressure constant?
There will be a big practical difference between to two situations. You will need to shift a lot of air, fast, to maintain the sort of pressure compared with doing it with water. But there is a lot of Potential Energy stored in compressed air, compared with the Energy stored in a compressed liquid.bluechipx said:, just air and air pushing water
The initial thrust will be the same as the pressure times the area but things will change once the fluid starts to flow.bluechipx said:Anybody care to venture a guess as to the actual thrust both ways?