Rarely heard sonic booms expected Tuesday as SpaceX launches, lands Falcon 9 rocket

A rarely heard cannonade of sonic booms will reverberate across the Space Coast on Tuesday, the result of a SpaceX Falcon 9 rocket launch and subsequent landing at Cape Canaveral Space Force Station.

After a 2:56 p.m. liftoff from Launch Complex 40, the rocket's 162-foot booster will separate from the payload-hauling second stage, flip around, and begin an autonomous descent toward nearby Landing Zone 1. Though it will have flown to an altitude hundreds of thousands of feet above Earth's surface, the booster will touch down just 5 1/2 miles from where it started.

It's been a while since residents and spectators were startled by sonic booms – the last time a Falcon 9 booster returned to the Cape for a local landing was in December. That mission took a classified National Reconnaissance Office payload to low-Earth orbit.

Sonic booms are generated when an aircraft or rocket approaches the speed-of-sound barrier during acceleration or deceleration. Falcon 9's booms aren't heard during ascent due to its altitude, but its landing booms are generated just over the Cape as it fires its Merlin engines to slow down.

"There is a possibility that residents of Brevard, Orange, Osceola, Indian River, Seminole, Volusia, Polk, St. Lucie and Okeechobee counties may hear one or more sonic booms during the landing," SpaceX said in a warning statement Monday. "But what residents experience will depend on weather and other conditions."

Falcon 9 sonic booms during landing

From bottom to top, Falcon 9 generates three sonic booms during its descent: first, the Merlin main engines, then the black landing legs, and finally, the titanium grid finds used to steer the rocket. Though some spectators close to the landing pad might be able to make out two or even all three booms, most will only hear one large rumble by the time it reaches their location.

Though loud enough to rattle windows and startle spectators, studies – including some authored by NASA and Air Force researchers – have shown sonic booms are not dangerous.

Booms used to be much more common on the Space Coast. Returning space shuttles would break through the sound barrier during their approach to Kennedy Space Center's former Shuttle Landing Facility, generating booms that could be heard as far away as Florida's west coast.

Tuesday, just two vehicles generate sonic booms during descent: Falcon 9 and X-37B, a secretive Boeing spaceplane operated by the Space Force that stays in low-Earth orbit years at a time. Hearing unscheduled booms is often a sign that X-37B has returned to the SLF, now called the Launch and Landing Facility.

Tuesday will see SpaceX fly its second Transporter mission, a service that allows several organizations to split launch costs by flying smaller spacecraft in one Falcon 9 payload fairing. The first Transporter flight broke records in January with a whopping 143 spacecraft, while Tuesday's launch will include 88 total payloads.

In Transporter-2 mission, flight path may be visible in South Florida

Transporter-2 has another treat in store for Florida: unlike most missions that fly toward the northeast or even straight out east over the Atlantic, Falcon 9 will rapidly gimbal its engines after launch and turn toward the south on a kind of polar trajectory known as sun-synchronous. If conditions are clear enough, the launch could be visible to residents well into South Florida.

Weather, meanwhile, should be 80% "go" for liftoff during the eight-minute window, according to the Space Force.

"Tuesday should continue the favorable conditions at the spaceport with morning coastal showers, but afternoon convection will remain mostly inland," Space Launch Delta 45 forecasters said Monday. "The primary concerns are the cumulus and anvil cloud rules associated with inland thunderstorm activity."

For the latest, visit floridatoday.com/launchschedule.

Reache Emre Kelly on Twitter at @EmreKelly.

This article originally appeared on Florida Today: SpaceX Falcon 9 rocket launch today: Sonic booms expected at landing