<div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>A launch pad problem prompted SpaceX to delay a flight to the International Space Station on Wednesday to replace </span><a href="https://www.9news.com.au/nasa" rel="" target="" title="NASA"><span>NASA</span></a><span>'s two stuck astronauts.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>The new crew needs to get to the International Space Station before </span><a href="https://www.9news.com.au/world/spacex-to-launch-mission-to-bring-stranded-nasa-astronauts-home/9310c7f8-91d2-484b-8f16-b6d7fe5489c4" rel="" target="_blank" title="Butch Wilmore and Suni Williams can head home after nine months in orbit"><span>Butch Wilmore and Suni Williams can head home after nine months in orbit</span></a><span>.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Concerns over a critical hydraulic system arose less than four hours before the Falcon rocket's planned evening liftoff from NASA's Kennedy Space Centre.</span></div></div><div><div id="adspot-mobile-medium"></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><strong><span>READ MORE:</span></strong><span> </span><a href="https://www.9news.com.au/world/donald-trump-trade-war-eu-retaliates-against-us-trade-moves-and-hits-beef-whiskey-motorcycles-with-targeted-tariffs/4aa62117-1875-41f4-988f-e7024c32de81" target="_blank"><strong><span>Canada and EU retaliate against Trump, hitting beef, whiskey, motorcycles</span></strong></a></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>As the countdown clocks ticked down, engineers evaluated the hydraulics used to release one of the two arms clamping the rocket to its support structure.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>This structure needs to tilt back right before liftoff.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Already strapped into their capsule, the four astronauts awaited a final decision, which came down with less than an hour remaining in the countdown.</span></div></div><div><div class="OUTBRAIN" data-reactroot="" data-src="//www.9news.com.au/world/spacex-delays-flight-to-replace-nasas-stuck-astronauts-after-launch-pad-problem/37495d0d-c39e-48d2-ad50-bd3d69916fe1" data-widget-id="AR_5"></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><strong><span>READ MORE:</span></strong><span> </span><a href="https://www.9news.com.au/world/russia-ukraine-ceasefire-plan-more-details-needed-says-vladimir-putin/9bf4bbba-1be7-414c-9c3a-0bce2120561e" target="_blank"><strong><span>Ukraine calls Putin's bluff, so how will he react?</span></strong></a></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>SpaceX canceled for the day.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Officials later said the launch was off until at least Friday.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Once at the space station, the </span><a href="https://www.9news.com.au/usa" rel="" target="" title="US"><span>US</span></a><span>, </span><a href="https://www.9news.com.au/japan" rel="" target="" title="Japanese"><span>Japanese</span></a><span> and </span><a href="https://www.9news.com.au/russia" rel="" target="" title="Russian"><span>Russian</span></a><span> crew will replace Wilmore and Williams, who have been up there since June.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><strong><span>READ MORE:</span></strong><span> </span><a href="https://www.9news.com.au/national/donald-trump-billionaires-lost-money-supporters-in-pictures/2f25bcae-f0ff-4de9-b45a-4a24c86c5f76" target="_blank"><strong><span>All the billionaires who have lost money by supporting Donald Trump</span></strong></a></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>The two test pilots had to move into the space station for an extended stay after Boeing's new Starliner capsule encountered major breakdowns in transit.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Starliner's debut crew flight was supposed to last just a week, but NASA ordered the capsule to return empty and transferred Wilmore and Williams to SpaceX for the return leg.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><a href="https://www.9news.com.au/national/how-to-follow-9news-digital/29855bb1-ad3d-4c38-bc25-3cb52af1216f" 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