According to Charlie Blackwell-Thompson, NASA’s Artemis launch director, teams encountered a liquid hydrogen leak while loading the propellant into the rocket’s core stage, and multiple troubleshooting efforts to address the area of the leak by reseating a seal in the quick disconnect where liquid hydrogen is fed into the rocket did not fix the issue.
A Nasa statement reads, “A liquid hydrogen leak has reoccurred again in a cavity between the ground and flight side plates of a quick disconnect in the engine section.”
While it can’t be said definitively what caused the leak, attention is focusing on inadvertent over-pressurisation of the hydrogen line early morning, and incorrect commands to the wrong valve, according to reports.
Engineers attempted to flush helium through the line but without success.
Artemis I is a flight test to launch NASA’s Space Launch System rocket and an uncrewed Orion spacecraft around the Moon before the Artemis II mission with astronauts aboard.
The rocket contained 730,000 gallons (2.76m litres) of liquid hydrogen – which must be stored at -423F – and oxygen. The two failed attempts are believed to cost the US space agency more than $1.2m.
Escaping hydrogen exceeded flammability limits by around two or three times. Dangers to life from hydrogen-related incidents include asphyxiation, blast overpressure, burns, fragments, frostbite and hypothermia.
Liquid hydrogen (LH2) fuel has played an important role in space exploration since NASA’s Apollo program.
The Saturn rockets used it for their secondary stage engines. Later the NASA space shuttle would use it to power its three main rocket engines.
Liquid hydrogen fuel has many benefits, including its low molecular weight and high energy output when burned together with liquid oxygen, according to WHA.
Liquid fuels are often a popular choice for secondary/upper rocket stages after solid rocket fuels provide the extra thrust required for liftoff. Hydrogen also provides low-density liquid fuel for navigation thrusters in orbit.
Liquid hydrogen challenges
Before hydrogen can see widespread use as an alternative fuel, the aerospace industry must overcome several key obstacles to adoption:
Extreme conditions: Hydrogen has a relatively low energy density, meaning that it must be stored in large quantities for any practical application as a fuel. To compensate, modern transportation applications are pushing the limits of technology with higher pressures and extreme cryogenic temperatures.
Public perception: Hydrogen first saw action in aviation not as a fuel, but as a lift mechanism in Zeppelins and airships as early as the mid-1800s. Although hydrogen is no longer used commercially in this capacity, historic events like the Hindenburg incident have left a mark on the industry, even though hydrogen was not the main source of fuel for the event.
Infrastructure: Airports will require significant infrastructure changes to accommodate hydrogen transportation and refuelling. Handling of hydrogen on such a large scale represents additional logistical challenges and fire/explosion hazards.
Alongside R&D programmes, the global space tourism market size is expected to reach US$8.67bn by 2030, and expand at a CAGR of 37.1% from 2022 to 2030.
Helios and Eta Space target oxygen use in space
Two space tech companies, Helios and Eta Space, recently teamed up to try and crack the problem of oxygen in space.
If humanity is to have a sustainable presence beyond Earth, the reusable methane-fuelled rocket systems need liquid oxygen at a ratio of 1:4, so the only cost-effective solution to refuelling in orbit is to create and store oxygen on the Moon and on Mars.
Helios, which is backed by the Israel Space Agency (ISA) and which announced funding from several venture capital firms, has developed an electrochemical reactor capable of extracting oxygen from the lunar regolith, which is made of approximately 45% oxygen.
Its proprietary technology and process has proven effective and is being used terrestrially for the extraction of other elements, such as iron.