Recently we have seen many rocket launches such as SpaceX’s Starlink, Falcon Heavy etc. getting postponed. There are various reasons why a rocket launch can’t get launched on time. Today we will try understanding those reasons in detail, but before that lets us go through basic terminology.
Postponements, scrubs, and delays are all terms used to describe launches that do not go off on time. Postponements are when a planned launch date is pushed back to a later date. Scrubs are when a mission is cancelled on the day of launch and rescheduled at a later date. Scrubs are typically a last-minute choice prompted by inclement weather or mechanical faults that raise safety concerns. A delay happens when a launch occurs later in the day than intended, yet still occurs on the same day.
There are specified times or “launch windows” available. The rocket is only allowed to launch within specified launch windows. This can last anything from a half-hour to a few hours per day. Even those windows, however, are not available on a daily basis. There are also “launch periods” which are days when the planetary (or celestial body) alignment aligns with our planet in a way that favours the mission.
The space shuttle is frequently left on the launch pad while the weather clears or maintenance workers address technical issues. However, the shuttle must occasionally be returned to the Vehicle Assembly Building (VAB). This is referred to as a rollback.
Postponements, scrubs and delays tend to occur due any of the following reasons:
The most common reason for rocket launch cancellations is bad weather.
If bad weather is enough to cause commercial aircraft delays and cancellations, you can believe it’s enough to scupper a mission worth hundreds of millions of dollars.
For the safe launch, the flight meteorologist will analyse 14 meteorological data points. The wind is being analysed particularly; the launch cannot take place if the sustained wind speed at the 162-foot level of the launch pad exceeds 30 mph. Upper-atmospheric winds typically blow at much higher speeds, increasing vertical wind shear.
Lightning and thunderstorms are the most important phenomena to monitor in relation to space launches. NASA will not fuel a rocket if there is more than a 20% chance of a lightning strike within a five-mile radius of the launch site; if lightning is seen within 10 nautical miles of the launch site or the flight route, the launch will be postponed for 30 minutes until the required circumstances are met. Another condition that must be measured is thunderstorm-related sky electricity; if the edge of a thunderstorm that has produced lightning in the last 30 minutes is within 10 miles of the launch site, the launch will be cancelled.
Clouds, too, pose a security risk to the rocket. If a cloud layer is more than 4,500 feet thick, stretches into sub-freezing temperatures, and is within 10 nautical miles of cumulus clouds, the launch will be cancelled. A rocket cannot launch if there is any form of precipitation.
In hot weather, rocket launches routinely go off without a hitch. Temperatures below 8.88 degrees Celsius, on the other hand, may result in dangerous ice development.
Another prevalent reason for rocket launch cancellations is the presence of huge amounts of high energy particles in near-orbit space.
The rocket itself is a technical wonder, with a complexity comparable to, but far more delicate than, the human body. A single mechanical failure might jeopardise the entire rocket’s safety and prevent a mission from reaching orbit.
Thousands of sensors collect data up until the last few seconds of any launch to see whether there is anything wrong inside the rocket. If any of them detects anything out of the ordinary or a cause for concern, they can immediately initiate a scrub, assuring the rocket’s and payload’s safety. Not to mention the need of doing integrity testing and maintaining all of the rocket parts beforehand.
A space launch can potentially be hampered by far more odd factors. An ISS resupply mission scheduled to launch from NASA’s Wallops Flight Facility in 2014 was cancelled because a sailboat—a SAILBOAT!—accidentally crossed the rocket’s flight path about 40 miles from the launch site. If the rocket had lifted off and encountered a catastrophic failure, the passengers on the boat would have been in danger. That risk prompted NASA to postpone the launch until another day. In addition, SpaceX recently postponed the launch of Starlink’s satellite due to “constellation optimization.“
However, those expenditures are insignificant when compared to the losses caused by months of delays caused by a rocket explosion (as SpaceX discovered the hard way) or the loss of life. The space business truly takes the old adage “better safe than sorry” to new heights, which few other industries do, and that’s a good thing.
If you know any such miscellaneous or any other reasons please let us know in the comments below.