This is an idea which I just posted on the Halfbakery website. I suspect people here will be able to tell me if it's been tried.
The basic problem is how to deliver fuel and oxidiser to the combustion chamber of a liquid rocket. Because the combustion chamber is at high pressure (?100bar?), it takes a greater pressure than this to pump the fuels into the chamber. As I understand it, this is normally done either by high-pressure pumps (which are complex and heavy), or by pressurising the fuel and oxidiser tanks (which means they have be very strong and heavy, to take >100bar).
My idea is to do away with pumps, and to avoid the need for the entire fuel and oxidiser tanks to be highly pressurized. Instead, there's a small intermediate high-pressure reservoir (one for the fuel, one for oxidiser), which holds (say) 10 second's worth of each component. There are valves between the main tanks and the pressure tanks, and between the pressure tanks and the combustion chamber.
The gulper rocket fires in bursts of (say) 10 seconds. First, the pressure tanks are closed from the combustion chamber and opened to the large, low-pressure fuel and oxidiser tanks, to fill the high-pressure tanks. Then the h.p. tanks are closed to the main tanks, and opened to the combustion chamber, and driven to high pressure (eg by helium, as in a "standard" pressure-fed rocket). Combustion is ignited, and the rocket burns for 10 seconds. When the fuel in the pressure tank is exhausted, combustion stops, and the whole cycle repeats itself. Hopefully, the pressure tanks could be refilled in 1 second or so, giving a "10 seconds on/1 second coast" pattern.
Basically, it's a way of making a pressure-fed rocket where you only need to pressurize the small, intermediate pressure tanks instead of the whole main tanks.
Any thoughts?
Paul