Houston-based Intuitive Machines’ Nova-C lunar lander is set to launch into space on February 14. NASA engineers on the module’s cryogenic fuel tanks installed experimental sensors fuel level. This technology has not yet been tested during long flights with acceleration and in zero gravity. The new product should provide a more accurate accounting of the fuel remaining in the tanks, which will improve the planning of flight missions.
On Earth, under conditions of normal gravity, fuel accumulates in the lower part of the tanks and determining its level is not difficult in many simple ways, from mechanical (floats, etc.) to electronic. In conditions of weightlessness and when moving with acceleration, fuel can spread over the walls or accumulate in one place. Conventional methods of measuring its level will give nothing but confusion. Therefore, NASA created a radio frequency sensor for measuring fuel mass – RFMG (radio frequency mass gauge).
The sensor “transmits” radio waves into the volume of the fuel tank and determines resonant responses that depend on the thickness of the fuel layer. The result is then compared with the database, after which the program calculates the approximate amount of remaining fuel. The developers claim that the measurement error does not exceed a few percent. NASA has already tested the new system on airplanes in free fall and on the ISS. As part of the Nova-C mission, the test will take place in its entirety, from launch on Earth to landing on the Moon.
Without the use of such sensors, the remaining fuel volume is calculated based on the estimated fuel consumption during engine operation. But cryogenic fuel in tanks tends to boil away during simple storage, which introduces a large error into the traditional method of calculating residues. For flights to the Moon, this, by and large, does not matter much, although the Japanese ispace HAKUTO-R module, it seems, just did not have enough fuel to land on the satellite. But when it comes to missions deep into the solar system, knowing the exact fuel reserves will go a long way toward helping plan the mission.