Insulation will be a key component of protecting NASA’s Space Launch System and its super-cold fuels.
Different types of cryogenic foam – used for very low temperatures – will insulate the rocket’s core stage and launch vehicle stage adapter, which connects the core stage to the interim cryogenic propulsion stage (ICPS). The core stage is the backbone of the rocket, and houses the avionics system, propellant and RS-25 engines. On SLS’s first flight with the Orion spacecraft, called Exploration Mission-1, the ICPS will give the Orion the big push needed to fly beyond the moon before the spacecraft returns to Earth.
The rocket’s fuel is cryogenic liquids: hydrogen at -423°F (-253°C) and oxygen -297°F (-183°C). Insulation protects the outside of the core stage from ice build-up resulting from the sub-zero liquids inside the aluminum walls, and reduces heat flow to the propellants, hardware and flight systems during launch and atmospheric re-entry.
“NASA has developed new, more environmentally friendly insulation materials for future launch vehicles,” said Michael Frazier, non-metallic materials branch chief at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “The cryo-insulation materials for SLS are not only more environmentally compliant, but they are also just as efficient and lightweight as the previous generation of materials.”
Three types of foam have been developed. All are closed-cell materials, which are stronger and have greater resistance to heat flow and moisture. They also are non-ozone-depleting and flame resistant.
The insulation is applied automatically by a robot; manually using a hand-held spray system; and hand mixed for pouring into molds. “With some parts of the rocket being so massive, like the core stage, robotic applications help reduce time and manpower with more control and continuous sprays,” said Amy Buck (above), SLS core stage insight lead. The thickness of the insulation varies depending on the hardware, but it is typically about one inch.
Hundreds of 24 x 24in panels have been covered with the three types of foam for a variety of tests being conducted by NASA and Boeing. Tests range from density measurements to exposure in heating environments experienced during ascent.
Testing of the foam systems is anticipated to be completed later this year after which time, the materials will be ready for Exploration Mission-1 in late 2018. “There are some follow-on aging tests that we will run over the next few years, but those are just being done to ensure we don’t have any problems with long-term storage of the cured-foam products,” Frazier said.
The initial SLS configuration, known as Block 1, will have a minimum 70-metric-ton lift capability. The next planned upgrade of SLS, Block 1B, will use a more powerful exploration upper stage for more ambitious missions with a 105-metric-ton lift capacity. Block 2 will add a pair of advanced solid or liquid propellant boosters to provide a 130-metric-ton lift capacity. In each configuration, SLS will continue to use the same core stage with four RS-25 engines.
September 9, 2016