A launch scrubbed four times in nine days shows how narrow the window really is
The payload must reach a specific orbital plane at a specific local solar time. That leaves a launch opportunity of eleven minutes a day — and weather has cooperated on none of them.
- Instantaneous window of about eleven minutes, once per day
- Four scrubs: two for upper-level winds, one for a ground valve, one for a boat
- Each scrub costs roughly 36 hours of turnaround before the next attempt
Four scrubs in nine days is not unusual for a mission with a narrow window, though it is frustrating for everyone watching. The reason the window is narrow has nothing to do with the rocket.
The payload is an Earth observation satellite that must operate in a sun-synchronous orbit, crossing the equator at the same local solar time on every pass — the condition that makes images from different days comparable. Reaching that plane at that crossing time defines an opportunity of about eleven minutes, once per day.
What scrubbed each attempt
The first two attempts were called for upper-level wind shear. Winds at 10 to 12 kilometres can impose structural loads on a vehicle in the transonic phase, and the limits are set by the vehicle’s design margin rather than by judgment on the day.
The third scrub was a ground-side valve that failed to indicate closed, replaced in eighteen hours. The fourth was a boat inside the marine keep-out zone that did not respond to radio and could not be cleared before the window closed.
People assume a scrub means something broke. Most days it means the sky was wrong, or someone went fishing in the wrong square of ocean.— A launch director who has run twenty campaigns
The cost of trying again
Each scrub costs roughly thirty-six hours. Propellant must be drained, the vehicle safed and inspected, the flight termination system’s batteries recharged or replaced, and the range rebooked. Range availability is often the binding constraint, because other users hold slots.
- Window: about eleven minutes, once per day, set by the target orbital plane
- Scrubs: two upper-level winds, one ground valve, one range incursion
- Turnaround: roughly 36 hours between attempts
- Constraint on retry: range availability as often as vehicle readiness
The next attempt is scheduled for tomorrow, with a forecast the launch weather officer put at 60 percent favorable. If the vehicle does not fly within the next six days it will stand down for a planned range maintenance period and wait about three weeks.
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