UAE astronaut mission to ISS ‘scrubbed’: Here’s what it means

SpaceX's Crew-6 launch to the International Space Station was scrubbed a little over two minutes before liftoff on Monday due to a reported “ground system issue.”

‘Scrubbing’ is the term used by the launch team to call off the rocket launch, meaning liftoff is delayed until further notice.

Reasons to scrub a launch include inclement weather, such as strong winds in the upper atmosphere, thunderstorm, or cold temperatures. Technical or mechanical issues with the launch rocket, spacecraft, payload or ground systems are also justifications to call off or scrub the launch.

If any of the sensors detect an abnormality, the launch will also be scrubbed to investigate any issues. Aeroplanes, ships, or boats — if they cruise within the determined safety range of the rocket — can cause a launch delay.

And birds, too. Back in 1995, woodpeckers delayed the launch of space shuttle Discovery after they pecked over 200 holes in the foam insulation of its external fuel tank as it sat on a launch pad at Florida’s Kennedy Space Centre.

Always safety first

A scrub can be called even a few minutes before liftoff. According to Nasa, “launch teams always err on the side of caution”, meaning, they are very cautious when launching a vehicle into space. They are even more careful when launching a crewed mission, like what happened to Crew-6 on Monday.

Why is it called scrubbing?

The term has its origin in US Navy missions. Back then, flights were written on a chalkboard and any mission that was no longer happening would be ‘scrubbed’ off the list.

Nasa’s use of ‘scrubbing’ means the launch is only postponed and not cancelled. Scrubbing is not uncommon. Artemis 1 was successfully launched from Kennedy Space Centre in November last year after four scrubbed launch attempts due to engine issues and tropical storms.

How is the new launch date selected?

There are several factors to consider, foremost of which is resolving any technical or mechanical issues that arose during the previous launch attempt. “When a launch is placed on hold, the launch operations team will determine what actions are required for the specific scenario of the mission. Each situation is different,” Nasa noted.

Weather condition is another important factor. Nasa and SpaceX had to forgo a launch opportunity tomorrow, February 28, due to unfavourable weather forecast. Aside from the next available launch attempt on March 2, Nasa is also looking at March 3 and 4 as viable options.

Factors like the rotation of Earth and its distance from the ISS are also considered when selecting a new launch date or time depending on the mission. The microgravity laboratory is orbiting Earth every 90 minutes at a velocity of 28,000 kph and the journey to the space station is a series of rocket burns or engine firings that must be precisely timed to achieve the correct orbit.

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