Many families with school-aged kids, including my own, were very excited to watch the launch of the SpaceX Crew Dragon rocket, containing astronauts Doug Hurley and Bob Behnken to the International Space Station. Meteorology is a field where the public and private sectors have to intentionally collaborate, and so it was really neat to see another positive outcome of a successful working relationship between a private company (SpaceX) and a government agency (NASA) to launch American astronauts into space on American soil for the first time since the space shuttle program ended in 2011.
The excitement for my kids, who are too young to remember the last shuttle flight in any detail, was palpable as we watched the launch together. While not as groundbreaking as when families gathered around TV sets in 1969 to watch the moon landing, it was neat to be able to witness a new advance in space flight with my kids in real time. As things often go, the launch of SpaceX Crew Dragon was delayed due to weather on May 27. Spaceflight.com reported that the launch was scrubbed due to lightning around Cape Canaveral. In order to schedule a launch, a specialized team determines the best time window based on a myriad of factors such as: where the rocket is intended to go, the type of rocket, solar requirements for the mission (whether solar power is needed, for example), the type of payload (whether it needs to be at a specific spot at a specific point in time), and whether there is a collision risk with any other of the many objects currently in earth orbit.. The correct trajectory is then developed and a ‘launch window’ is defined. Depending on all of these factors, that window may be very short or several hours. NASA has a great writeup here which goes into much more detail about how the launch window is defined.
However, many circumstances can cause a launch postponement right up to minutes before the scheduled liftoff. These include equipment not passing last-minute checks, and of course, the weather. Weather conditions which may delay a typical rocket launch include wind speeds over 30 miles per hour, thunderstorms which can produce lightning, and any precipitation near the launch pad. In addition to the normal conditions which must be met at the Cape Canaveral launch site, the SpaceX Crew Dragon liftoff was dependent on weather conditions downrange of the launch site over the Atlantic Ocean. The reason for this is that there is an option, should something go catastrophically wrong, that the crew can escape the rocket during its ascent and thus weather conditions must be good even far away from the initial launch site. NASA identifies all of the very specific ‘go’ criteria in this handy reference sheet. As you can see, there are numerous ways for weather to cause a last minute scrub of a launch, particularly if the window is relatively short.
After completion of its mission at the ISS, the crew was ready to return to earth in early August. In order to make a successful landing, seven potential splashdown sites were determined, all located off the east and west coasts of Florida in the Atlantic Ocean and Gulf of Mexico. The Crew Dragon actually has the capability to use thrusters to change its trajectory mid-fall should it become necessary to move to an alternate splashdown site as the craft makes its way back to earth. A primary splashdown target is identified, based on weather and other conditions, about six hours before the craft undocks from the ISS. At 2.5 hours prior to the scheduled undocking time, a go/no-go call is made, although a no-go call can be made even up to shortly before undocking. In order to quickly get to the crew in the capsule, winds must be light, waves must be small, no lightning and a low chance of rainfall must all occur. Specialized parachutes on the capsule assist with deceleration and a smooth landing in the ocean. NASA also has a great reference document here which discusses how the landing occurs.
Although it looked like Hurricane Isaias may interfere with the landing window, a ‘go’ was given and splashdown took place successfully in the Gulf of Mexico, south of Pensacola, on August 2. A full video of the splashdown can be watched here:
It is easy to take events such as rocket launches and landings (with or without human cargo!) for granted in the highly technological age which we live in. However, spaceflight is a feat which requires precision engineering, excellent communication and collaboration between many entities, and yes, great weather forecasts, to happen!