United Launch Alliance has identified the root cause of a failure that destroyed the upper stage of its Vulcan rocket in late March. According to the company\u2019s chief executive, Tory Bruno, the Centaur V upper stage failed due to higher-than-anticipated stress near the top of the liquid hydrogen propellant tank and slightly weaker welding.<\/p>\n
Bruno outlined the nature of the failure and steps the company is taking to remediate it during a teleconference with space reporters on Thursday. He said United Launch Alliance is working toward flying the heavy lift Vulcan rocket on its debut mission during the fourth quarter of this year.<\/p>\n
The Centaur V upper stage was destroyed during pressure testing at Marshall Space Flight Center in Alabama on March 29. Bruno said this was the 15th test in a series of 45 tests to qualify the Centaur stage for all potential mission profiles. However, about halfway through the test the hydrogen tank started leaking, and over the course of four and a half minutes the leak expanded.<\/p>\n
During this time hydrogen leaked into a confined area of the test stand, a relatively enclosed space. After it reached a flammable concentration and found an ignition source, the hydrogen caught fire. This seriously damaged the test stand as well as the hydrogen tank and liquid oxygen tank\u2014loaded with liquid nitrogen for this test.<\/p>\n
Pretty quickly, the failure investigation team identified that the leak occurred in the forward dome, or top section, of the hydrogen tank. Analyzing pieces of the tank using \u201cfractography,\u201d Bruno said investigators were able to pinpoint where the crack in the stainless-steel tank originated, near the top of the dome.<\/p>\n
To understand the nature of the failure, Bruno said the company ran a high-fidelity model of the loads and stresses on the hydrogen dome in this location and found there were unexpectedly higher loads there. Additionally, the team analyzed the strength of the welds nearby and found they were not as high as previously assessed.<\/p>\n
,<\/p>\n
\u201cThe two things together, higher loads and somewhat lower strength in the weld, are what caused the crack to begin,\u201d he said. \u201cThe other thing I would ask you to appreciate, since we\u2019re being completely transparent here, is how we were already 15 tests in, which is considerably more testing and exposure to many more pressure cycles and lots and lots of more time with the structure sitting under pressure than would ever happen in any single flight.\u201d<\/p>\n
To address the failure, Bruno said the fix is relatively straightforward. The area near the failure will be strengthened with an additional ring of stainless steel and strips of metal. These corrective actions will add about 140 kg to the mass of the upper stage, which he characterized as a negligible loss of payload capacity on a vehicle projected to lift 27 metric tons to low-Earth orbit.<\/p>\n
The company is preparing a new dome with these fixes, and this Centaur V tank will undergo a handful of additional pressure tests to verify its predicted behavior. In addition, the Centaur V upper stage that was to be used on the debut flight of the Vulcan rocket\u2014known as the Cert-1 mission, as it is the first of two certification flights for the US Space Force\u2014has been shipped from the launch site back to the company\u2019s factory in Decatur, Alabama. It will undergo similar modifications.<\/p>\n
Bruno said performing the final qualification tests for the Centaur V anomaly and modifying the flight version of the tank are the final two steps needed before Vulcan can launch. He said he was pleased with the performance of the rocket\u2019s first stage during a recent \u201cflight readiness firing\u201d test, when the rocket\u2019s BE-4 engines ignited for a few seconds.<\/p>\n
,<\/p>\n
\u201cWe were really, really pleased with the flight readiness firing,\u201d Bruno said. \u201cEverything was phenomenal. And there were no, I\u2019ll say, no actions required on any of the hardware, any of the procedures.\u201d<\/p>\n
Bruno said he anticipates a period of four to six weeks between the completion of the qualification tests and the launch of Vulcan. This mission will carry a lunar lander for Astrobotic, as well as two test satellites for Amazon\u2019s Project Kuiper megaconstellation. In addition to the rocket\u2019s readiness, the Astrobotic mission launch date will also be determined by lighting conditions on the Moon for the lander, so there are only a few acceptable launch dates per month.<\/p>\n
The second flight of Vulcan will launch the Dream Chaser spacecraft for Sierra Space. CNBC reported this week that one of the two BE-4 engines intended to fly on this Vulcan core exploded during acceptance testing in June at Blue Origin\u2019s facilities in West Texas. Bruno said it was fairly routine for rocket parts to fail this acceptance testing, especially in the early stages of development. He said Blue Origin understands the cause of the problem and has additional engines under construction.<\/p>\n
Assuming this second certification mission occurs during the first quarter of 2024, United Launch Alliance and the US Space Force would need a few months to review data from these first two launches. After that, the Vulcan rocket would be certified for national security launches. Bruno said the company is targeting the second quarter of 2024 for this initial Space Force launch.<\/p>\n
As is often the case in space missions, that timeline seems rather optimistic. But it does appear as though United Launch Alliance has a clear path toward finally launching its Vulcan rocket and getting the vehicle ready for a lengthy manifest that includes both missions for the military as well as dozens of flights for Amazon\u2019s Kuiper constellation.<\/p>\n","protected":false},"excerpt":{"rendered":"
United Launch Alliance has identified the root cause of a failure that destroyed the upper stage of its Vulcan rocket in late March. According to the company\u2019s chief executive, Tory Bruno, the Centaur V upper stage failed due to higher-than-anticipated stress near the top of the liquid hydrogen propellant tank and slightly weaker welding. Bruno […]<\/p>\n","protected":false},"author":1,"featured_media":46094,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[21,364],"class_list":["post-46092","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-space","tag-vulcan"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/46092"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=46092"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/46092\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/46094"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=46092"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=46092"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=46092"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}