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<\/p>\nStoke Space recently carried out the first test of the full-size 30-thruster version of the innovative engine that the company is producing for its in-development second stage. This will be an integral part of its future Nova rocket, which aims to be a fully reusable medium lifter.<\/p>\n
The engine test took place on Feb. 26 and follows the engine\u2019s first test flight on its prototype vehicle, Hopper 2, in September 2023. Although fitted with only 15 chambers for that flight, Hopper 2 flew for 15 seconds, achieved a maximum altitude of 30 feet, traversed to a landing site, and touched down softly.<\/p>\n<\/p>\n
NSF recently spoke with Stoke Space to discuss the Hopper campaign and the path ahead. According to Stoke, \u201cThe Hopper vehicle was\/is a full-size second stage prototype, equipped with a fully functioning actively cooled heat shield. The test flight provided clear evidence of this functionality, as evidenced by the icy condensation visible on the heat shield during flight in released photos and videos.\u201d<\/p>\n
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Hopper 2 takes to the skies in a mix of fire and ice. Note the ice accumplating on the heat shield, evidence that the active cooling was operating during the flight. (Credit: Stoke Space)<\/p>\n
As to how comprehensive the testing campaign was, the company added, \u201cThe Hopper campaign demonstrated our engine\u2019s full landing burn capabilities, including deep throttle control and precise steering through differential throttle thrust vector control, even under conditions of minimal propellant and no payload.\u201d Furthermore, \u201cIn our tests so far, we\u2019ve successfully achieved burn durations that deplete the entire run tanks.\u201d<\/p>\n
Stoke Space also clarified, \u201cOur heat shield is engineered for active cooling at multiple critical mission stages, ensuring optimal protection, performance, and mobility to, through, and from space.\u201d<\/p>\n
When asked whether there were any specific engineering issues with pumping the hydrogen through the longer-than-usual channels, the company responded, \u201cWe\u2019ve encountered no significant challenges in this regard. Engine test and Hopper flight data validated analytical predictions made by our in-house tools, confirming the ability to manage these requirements.\u201d<\/p>\n
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A test firing of a 15-chamber second stage engine. Note the frost on the heat shield. (Credit: Stoke Space)<\/p>\n
Interestingly, although there are multiple benefits, utilizing several small thrusters has some downsides: \u201cThe smaller size of our thrusters significantly simplifies manufacturing processes, presenting a clear advantage. However, this approach does introduce challenges in propellant distribution and net weight due to the cluster configuration compared to using a single large chamber. Yet, these challenges are offset by the benefits in terms of mass efficiency for flight, re-entry, and rapid reusability, ultimately justifying their presence in our design.\u201d<\/p>\n
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Andy Lapsa \u2013 the Chief Executive Officer for Stoke Space \u2013 recently appeared on an episode of NSF Live with NSF\u2019s John Galloway, expanding on many subjects around the philosophy and design of the company\u2019s vehicles.<\/p>\n
Stoke Space Technologies of Kent, WA, was formed in early 2021 by Andy Lapsa and Tom Feldman. Both had previously held senior positions working for Blue Origin on BE-4 engine development and managed to raise over $9 million in seed funding for their new venture.<\/p>\n<\/p>\n