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<\/p>\nAfter a series of DARPA-supported tests of an all-composite cryogenic propulsion tank, Boeing has succeeded in advancing the new reduced-mass tank technology to Technology Readiness Level 6 (TRL 6).<\/p>\n
The all-composite design contrasts to the welded tanks commonly used throughout the industry for rockets\u2019 stages \u2014 although Rocket Lab\u2019s Electron is an outstanding example of composites, albeit on a much smaller scale.<\/p>\n<\/p>\n
For Boeing\u2019s new tank, the all-composite structure is 4.3 meters in diameter and \u201csimilar in size to the propellant tanks intended for use in the upper stage of NASA\u2019s Space Launch System (SLS) rocket.\u201d<\/p>\n
And that is the part of the advancement that pushes composite technology forward: large, lightweight tanks that can help increase a rocket\u2019s overall performance by reducing vehicle mass \u2014 which translates into a greater payload-to-destination mass capability for the overall system.<\/p>\n
For the Boeing all-composite tank, testing and modeling so far indicate the potential to increase the SLS Block 1B\u2019s performance by up to 30% if the Exploration Upper Stage\u2019s design with welded tanks were switched to the new all-composite structure.<\/p>\n
\u201cThat\u2019s a near-term system that could benefit pretty greatly from this sort of technology \u2026 should NASA see this as a beneficial upgrade in performance for that part of the mission,\u201d said Jim May, Technology Integration Specialist, Space, and Launch Division, Boeing, in an interview with NASASpaceflight.<\/p>\n
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Boeing\u2019s all-composite cryogenic fuel tank undergoing pressure testing at NASA\u2019s Marshall Space Flight Center. (Credit: Boeing)<\/p>\n
\u201cAnd, as a lot of us in the space industry know, mass is very important to space systems. And so, as we\u2019ve kind of matured this composite technology, where composites are a good place to reduce the structural mass on things like tanks, we saw an ability or a way to reduce, pretty significantly, the mass in propulsion systems in the tank area \u2014 paired with a material that can support and hold in cryogenic fuels.\u201d<\/p>\n
Astronomy (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n But getting to the point of being able to test this technology, bring it to TRL 6, and be ready to offer this new, all-composite structure for future rockets and deep space missions took time and effort.<\/p>\n \u201cSo this kind of validated the scale, the ability to build this at scale and meet the same requirements [as metallic tanks]. And the hard part of this technology is doing it at large scale,\u201d related May.<\/p>\n In particular, having a facility large enough to build the tank was a challenge. According to Boeing, \u201cYou need a fiber placement facility that can handle a structure of this size to layup in one piece within the material out-time and an autoclave that it will fit in. Not many organizations have composite fabrication facilities that can handle a part of this size.\u201d<\/p>\n After finding the location, the tank underwent final assembly between 2020 and 2021 having originally been intended for DARPA\u2019s Experimental Spaceplane Program.<\/p>\n \u201cDARPA\u2019s interest is in advancing the technology of these propulsion systems,\u201d noted May. \u201cAnd we\u2019re building the tank in one large composite piece without an incremental metallic liner. But building it to the same requirements you would build metallic tanks to avoid losing your propellant to permissibility.\u201d<\/p>\n Boeing\u2019s reusable Phantom Express spaceplane would have used all-composite cryogenic tanks to deploy an expendable upper stage for orbital launches. (Credit: Mack Crawford for NSF\/L2)<\/p>\n Following its construction, the tank was taken to NASA\u2019s Marshall Space Flight Center in Huntsville, AL where it underwent a series of pressure tests and inspections.<\/p>\n \u201cWe did a number of pressure cycles and stopped partway through to thoroughly inspect the tank for any damage,\u201d Boeing explained. \u201cThat requires draining the tank, moving it out of the test facility, and removing parts for interior inspection. Then putting it all back together, moving back into the test area, and connecting and testing all the instrumentation again. This was not just one simple test sequence.\u201d<\/p>\n In a final test designed to over-pressurize the tank and burst it \u2013 known as a test to failure to validate computer modeling \u2013 the tank reached a maximum pressure of 3.75 times its design requirement and still did not burst \u2014 with Boeing noting that no major structural failures were identified.<\/p>\n In addition to pressure tests, leak and permeation tests were also conducted to verify tank performance and that the tank was not leaking cryogenics.<\/p>\n On top of the size challenge of the composite tank, \u201cthe cryogenic part is one of the harder parts of getting composites to work,\u201d related Mr. May.<\/p>\n Per Boeing, \u201cWe ran the tank test with liquid nitrogen, but we have done coupon and element tests at both liquid oxygen and liquid hydrogen temperatures. At cold temperatures, some of the properties are slightly lower but coupon and element tests provide the appropriate data that allows us to design a robust composite tank that can meet requirements even at these extremely low temperatures.\u201d<\/p>\n![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2022\/03\/f.jpg\")
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