Within the vacuum of area, the place temperatures can plunge to minus 455 levels Fahrenheit, it’d seem to be protecting issues chilly can be straightforward. However the actuality is extra complicated for preserving ultra-cold fluid propellants – or gasoline – that may simply overheat from onboard programs, photo voltaic radiation, and spacecraft exhaust. The answer is a technique known as cryogenic fluid management, a collection of applied sciences that shops, transfers, and measures tremendous chilly fluids for the floor of the Moon, Mars, and future long-duration spaceflight missions.
Tremendous chilly, or cryogenic, fluids like liquid hydrogen and liquid oxygen are the commonest propellants for area exploration. Regardless of its chilling surroundings, area has a “sizzling” impact on these propellants due to their low boiling factors – about minus 424 levels Fahrenheit for liquid hydrogen and about minus 298 for liquid oxygen – placing them vulnerable to boiloff.
In a first-of-its-kind demonstration, groups at NASA’s Marshall Area Flight Heart in Huntsville, Alabama, are testing an modern strategy to attain zero boiloff storage of liquid hydrogen utilizing two phases of lively cooling which might stop the lack of worthwhile propellant.
“Applied sciences for lowering propellant loss should be carried out for profitable long-duration missions to deep area just like the Moon and Mars,” mentioned Kathy Henkel, performing supervisor of NASA’s Cryogenic Fluid Administration Portfolio Mission, based mostly at NASA Marshall. “Two-stage cooling prevents propellant loss and efficiently permits for long-term storage of propellants whether or not in transit or on the floor of a planetary physique.”
The brand new method, often known as “tube on tank” cooling, integrates two cryocoolers, or cooling units, to maintain propellant chilly and thwart a number of warmth sources. Helium, chilled to about minus 424 levels Fahrenheit, circulates via tubes connected to the outer wall of the propellant tank.
Groups put in the propellant tank in a take a look at stand at NASA Marshall in early June, and the 90-day take a look at marketing campaign is scheduled to conclude in September. The tank is wrapped in a multi-layer insulation blanket that features a skinny aluminum warmth protect fitted between layers. A second set of tubes, carrying helium at about minus 298 Fahrenheit, is built-in into the protect. This intermediate cooling layer intercepts and rejects incoming warmth earlier than it reaches the tank, easing the warmth load on the tube-on-tank system.
To stop harmful stress buildup within the propellant tank in present spaceflight programs, boiloff vapors should be vented, ensuing within the lack of worthwhile gasoline. Eliminating such propellant losses is essential to the success of NASA’s most bold missions, together with future crewed journeys to Mars, which would require storing massive quantities of cryogenic propellant in area for months and even years. To date, cryogenic fuels have solely been used for missions lasting lower than per week.
“To go to Mars and have a sustainable presence, you should protect cryogens to be used as rocket or lander return propellant,” Henkel mentioned. “Rockets at present management their propellant via margin, the place bigger tanks are designed to carry extra propellant than what is required for a mission. Propellant loss isn’t a difficulty with brief journeys as a result of the loss is factored into this margin. However, human exploration missions to Mars or longer stays on the Moon would require a distinct strategy due to the very massive tanks that might be wanted.”
The Cryogenic Fluid Management Portfolio Mission is a cross-agency group based mostly at NASA Marshall and the company’s Glenn Analysis Heart in Cleveland. The cryogenic portfolio’s work is beneath NASA’s Technology Demonstration Missions Program, a part of NASA’s Space Technology Mission Directorate, and is comprised of greater than 20 particular person expertise improvement actions.
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