The night sky has drawn thousands of people outdoors over the past week & for very good reason.
We have all been party to a great light show in the sky, partly the Lyrids meteor shower & the other space oddity, a perpetual stream of golden Starlink satellites.
The Starlink satellite spectacle is courtesy of the latest stream of satellites to have been launched by SpaceX, Elon Musk’s advanced rocket & spacecraft manufacturing company. The Starlink project seeks to launch hundreds of thousands of satellites, to beam the internet down to Earth from orbit.
Founded in 2002, SpaceX’s goal is to revolutionize space technologies, with the ultimate goal of enabling people to colonize other planets. (1)
One of SpaceX’s largest projects, is the massive Starship project destined to take humans to Mars & colonize the planet. Elon Musk has already seen two of his Starships’ SN1 & SN2 collapse under cryogenic testing & most recently, on 3rd April 2020, SN3 failed under pressure testing & collapsed.
‘The test, a cryogenic pressure test, was intended to demonstrate that SN3 could withstand the high pressure of very cold fuel that such a vehicle will need to endure before flights. Musk said that SN3 had passed an ambient temperature test the night prior to the failed cryogenic pressure test.
The cryogenic pressure test would have been followed by a static fire, during which the vehicle’s engines would have briefly lit while SN3 was held in place, and a hopping test, when SN3 would have made the first flight of a full-size Starship prototype.’ (2)
One of the greatest challenges faced by any space travel & or rocket launch systems; is how to stabilise the fuelling systems, when under immense pressures.
Therefore, what part does Cryogenics play in space travel, why are cryogenic processes a vital part of the launch & testing process & why have NASA been developing Cryogenic fuel management systems?
‘Cryogenic propellants are fluids chilled to extremely cold temperatures & condensed to form liquids. Fluids such as liquid hydrogen, liquid oxygen & liquid methane, when kept at their ideal operating temperatures of -423 degrees Fahrenheit, -297 degrees and -259 degrees, respectively, can be used to provide high-energy propulsion solutions critical to future human missions beyond low-Earth orbit.’ (3)
Due to the ultra low temperatures of these fluids, storing & handling them is a challenge, which is something the SpaceX teams have come up against recently. Energy given off by the spaceship or rocket structure & solar radiation, continually threatens to raise the fuel temperatures causing it to evaporate & subsequently making it unusable as a propellant. In addition, the ‘boil off’ can also reduce the density of the propellant once in orbit, making it a challenge to ensure fuelling is accurate prior to launch.
NASA’s Evolvable Cryogenics project, or eCryo project managed by NASA’s Glenn Research Center in Cleveland, is seeking ways to integrate cryogenic fluid management technologies at a scale relevant for possible infusion into a variety of future space vehicles and space systems. (3)
NASA’s eCryo project is seeking ways to ensure more stable & huge density fuel loads are capable of sustaining such long distances & as they move towards “Mars ready” missions, the long duration storage of cryogenic fluids is becoming crucial.
The eCryo project is addressing the challenges of fluid management technologies in four stages:
- Analysis tools: Development and validation of computer codes capable of predicting boil-off, tank mixing, pressurization and chill-down phenomena for both settled and unsettled cryogenic fluid systems.
- Multi-layer insulation (MLI) characterization: Testing and analysis to quantify the thermal performance of thick MLI blankets at conditions and configurations representative of SLS upper stage mission implementations.
- Vapor-based heat intercept: Subscale characterization of the potential benefit of using vapor vented from a propellant tank to intercept heat coming into the tank through structural elements. Building on this subscale testing, the eCryo team will demonstrate vapor-based cooling at nearly full scale and in a configuration representative of a potential upper stage.
- Radio frequency mass gauging (RFMG): Quantifying the microgravity performance and accuracy of an RFMG system, an innovative propellant-quantity gauging technology to be implemented in a cryogenic tank flown on the International Space Station as a demonstration. (3)
These four areas are helping to evolve the eCryo project technologies, with a long term view of enabling the maturation of the eCryo analysis tools to be able to predict the behaviour of fluids for long duration storage & transfer of cryogenic fluids in microgravity (4)
Written by Katy-Jane Mason for & on behalf of Dolphin N2