Tankage Options for Liquid Hydrogen

Single wall metal tanks with foam insulation have been routinely used in launch vehicles where onboard storage times for LH2 is short prior to feeding it to the rocket engines. The primary advantage of this approach is the high mass fraction potential, which is critical for launch vehicles. However, the very poor thermal performance of a single wall tank with foam makes it unsuitable for most mobile applications unless a similar concept of operation is envisioned (i.e., short storage time followed by high consumption rate).

Stationary LH2 storage vessels have an inner wall that contains the fluid, an outer wall exposed to ambient conditions, and an evacuated volume between the walls (akin to a Thermos bottle) [1]. A high level of vacuum must be created and maintained between the walls to ensure adequate thermal performance. Insulation is generally used in the evacuated space to further reduce heat transfer to the inner tank wall. Commonly used insulation types—ordered in increasing thermal performance in a high-vacuum environment—include aerogels, perlite, glass bubbles, and multilayer insulation.

This double wall dewar construction, also referred to as “vacuum-jacketed,” is needed for most mobile applications to achieve an acceptable boil-off rate and to meet other system requirements. Vacuum-jacketed piping, valves, and connections are also used to minimize heat load during transfer and other LH2 operations.

Typical inner wall materials compatible with LH2 service include 300-series stainless steel and aluminum alloys. Composite formulations are currently under development as a lighter-weight option to achieve higher mass fraction LH2 storage. Airbus and the Royal Netherlands Aerospace Centre are developing composite LH2 dewars for aircraft. Gloyer-Taylor Laboratories is also developing single- and double-walled composite storage vessels for a variety of applications. Conformable tanks for improved form factor integration, as well as additive manufacturing techniques, are being developed by various organizations [2].

3.0 Cryogenic Tankage

This post is a continuation of previous video clips from the short course on cryogenic fluid management (CFM) I taught at NASA's Thermal and Fluid Analysis Workshop in September, 2022. The reference report used to present the course topics can be accessed on the Training page at www.moraninnovation.com.

Matt Moran is the Managing Member at Moran Innovation LLC, and previous Managing Partner at Isotherm Energy. He's been developing power and propulsion systems for more than 40 years; and first-of-a-kind liquid, slush and gaseous hydrogen systems since the mid-1980s. Matt was also the Sector Manager for Energy & Materials in his last position at NASA where he worked for 31 years. He's been a cofounder in seven technology based start-ups; and provided R&D and engineering support to hundreds of organizations. Matt has three patents and more than 50 publications including the Cryogenic Fluid Management report series. More about him can be found here.