On Sunday, January 7, 2018, SpaceX launched the much delayed and mysterious Zuma payload. This launch occurred at 8pm local time from the newly reactivated SLC-40 launch pad in Florida. The successful launch provided a spectacular light show for viewers in the area and cleared the way for Falcon Heavy to begin its final preparations for it maiden flight.

SpaceX Zuma launch (SpaceX)

Northrop Grumman commissioned the launch and provided the payload for an unknown government office. This alone is unusual, as even with the National Reconnaissance Office and Air Force X-37B missions, the customer was well known, even if the payload was not (or in the case of the X-37B, the payload’s payload). In fact, Northrop Grumman hasn’t given any indication as to what type of payload Zuma actually is, only that it is restricted.

As viewers of SpaceX launches have begun to expect for classified launches, the “RocketCam” views of the launch stopped just after MECO. The public video feed then continued with the landing of the first stage booster at Landing Zone 1. However, SpaceX did confirm a successful fairing separation, so presumably, the balance of the mission was also a success.

UPDATE: As per this tweet by Peter B. de Selding, the Zuma payload may be dead on orbit. More details on this as they emerge.

UPDATE: Apparently, SpaceX performed correctly, per Eric Berger’s Tweet.

UPDATE: In a recent email from Gwynne Shotwell, President of SpaceX, she has stated, “Since the data reviewed so far indicates that no design, operational or other changes are needed, we do not anticipate any impact on the upcoming launch schedule. Falcon Heavy has been rolled out to launchpad LC-39A for a static fire later this week, to be followed shortly thereafter by its maiden flight. We are also preparing for an F9 launch for SES and the Luxembourg Government from SLC-40 in three weeks.”

Zuma booster making a precise arrival at Landing Zone 1.

While it would have been great to watch the Zuma payload be deployed, the landing, as usual, did not disappoint. As the booster arrived, viewers were treated with a view from the rocket, showing a precise arrival dead center on the X painted on the landing pad and oriented such that the legs met with the breaks in the outer circle. This sort of precision will be vital for more advanced landing scenarios with the large BFR vehicle that SpaceX is currently developing.

SpaceX’s Zuma mission as seen from a local beach (John Kraus)

Viewers on the ground were also treated to a spectacle as the nearly cloudless night time launch allowed for an exemplary view of the various portions of the launch sequence. The above image, taken and compiled by John Kraus from three long exposure shots, provides an excellent opportunity to understand what happens when Falcon 9 launches a payload and returns to Landing Zone 1.

Launch

The Falcon 9 launches from its pad and immediately begins moving in the desired direction for the target orbit. At this point, the vehicle is going generally vertically away from the surface, but that changes quickly.

Gravity Turn

Once the vehicle has passed through the thicker parts of the atmosphere, it begins to turn so that it can accelerate to orbital speed relative to the ground. The target speed varies based on the target orbit.

MECO, Staging and Boost Back

The break in the trail illustrated here is called MECO or Main Engine Cutoff. For the Falcon 9 this involves shutting off all nine Merlin engines at the base of the first stage. Following that, the second stage separates from the first stage and continues on its way. This is where Falcon 9 launches differ from other rocket launches.

After staging, the first stage booster rotates using nitrogen thrusters and reignites some of its engines to perform what is called a Boost Back burn. This can be seen in the image where the streak curves upwards. This allows the booster to reduce momentum and also position itself so that it is falling back towards the cape.

Re-entry Burn

As the first stage begins to enter the thicker parts of the atmosphere, it once again ignites a few of the Merlin engines to protect the booster from the heat caused by friction during reentry. It might seem a bit strange that falling into the rocket engine exhaust will protect the rocket from reentry heating, however the shock wave caused by the exhaust acts as a sort of envelope that pushes the air away and keeps conditions surrounding the engines similar to those during launch. This burn also slows the rocket down a bit.

Landing Burn

The landing burn is the final step of landing the stage 1 booster. At this point, the booster is just about lined up with the landing zone (or the ASDS in the case of an ocean based landing). There is still a small correction to be made at this point. The reason this correction is left till the end is that if there is an issue restarting the engines for the landing burn, the Falcon 9 can “ditch” into the ocean, rather than crashing on land in an uncontrolled fashion.

At the point that the landing burn starts, the booster is rapidly slowing down due to drag from the open top of the booster’s interstage and the grid fins used to steer it. For Zuma, the booster was falling at 915 kmh (568 mph) and was 3 km (1.86 mi) from the ground. The approximately 30 second landing burn slows the booster such that the booster speed reaches 0 at the same time that the altitude reaches 0.

The mysterious Zuma launch has marked the beginning of what promises to be a banner year for SpaceX and the space industry in general with the maiden launch of the Falcon Heavy just a few weeks away, the first Crew Dragon expected in April, and an anticipated 30 overall launches this year.

For more information about how SpaceX lands the Falcon 9, check out this excellent video from The Everyday Astronaut! Also, special thanks to John Kraus for permission to use his extraordinary photograph of the launch and landing.