Maiden Falcon 9 reusability test on Friday

Falcon 9 Rocket The SpaceX Falcon 9 rocket's fifth cargo resupply mission to ISS, which was rescheduled to Friday following a glitc...

Falcon 9 Rocket

The SpaceX Falcon 9 rocket's fifth cargo resupply mission to ISS, which was rescheduled to Friday following a glitch in the second stage thrust vector control actuator on Tuesday, will represent the first in a series of similar tests that will ultimately deliver a fully reusable Falcon 9 rocket, thereby reducing launch costs.


During the flight, SpaceX will attempt precision landing of Falcon 9 first stage for the first time, on a custom-built ocean platform known as the autonomous spaceport drone ship.

The test require the first stage booster to reenter from space at hypersonic velocity, restart main engines, deploy landing legs and touch down at near zero velocity.
SpaceX says the odds of success are not great—perhaps 50% at best. The attempt to recover the first stage will begin after stage separation with priority to complete the cargo resupply mission successfully.

photo:SpaceX

The first stage has a burn time of 180 seconds, reaching over a 100 km. Although reusability of the second stage is more difficult, SpaceX intend to eventually make both stages of the Falcon 9 reusable.
Falcon 9 has about 30 percent more payload capacity than published on its standard price list, reserved for the powered re-entry.

Returning anything from space is a challenge, but returning the 14 storey tall Falcon 9 first stage which travels at 1300 m/s upwards, for a precision landing presents a number of additional hurdles. SpaceX compares stabilizing the first stage for reentry to balancing a rubber broomstick on hand in the middle of a wind storm.

To stabilize the stage and reduce speed during reentry, the nine clustered Merlin 1D engines that constitute the first stage, will be relighted for a series of three burns. The first burn—the boostback burn—adjusts the impact point of the vehicle and is followed by the supersonic retro propulsion burn that, along with the drag of the atmosphere, slows the vehicle’s speed from 1300 m/s to about 250 m/s. The final burn is the landing burn, during which the landing legs deploy and the vehicle’s speed is further reduced to around 2 m/s.

Steerable fins on the reusable falcon 9 photo:SpaceX

A key addition include the four hypersonic grid fins placed in an X-wing configuration around the vehicle to improve landing precison, stowed on ascent and deployed on reentry to control the stage’s lift vector. Each fin moves independently for roll, pitch and yaw, and combined with the engine gimbaling, will allow for precision landing – first on the autonomous spaceport drone ship, and eventually on land.

autonomous landing platform photo:SpaceX

As the rocket stages are designed to fall to ocean post launch, the floating landing platform which has limited size and not entirely stationary, presents added complication. The autonomous spaceport drone ship is 300 by 100 feet, with wings that extend its width to 170 feet. While that may sound huge at first, to a Falcon 9 first stage coming from space, it seems very small. The legspan of the Falcon 9 first stage is about 70 feet and while the ship is equipped with powerful thrusters to help it stay in place, it is not actually anchored, so finding the bullseye becomes particularly tricky.

SpaceX developed the powered reentry technology through the Grasshopper and the Falcon 9 Reusable Development Vehicles (F9R Dev) experimental technology demonstrator suborbital reusable rockets that can takeoff and land vetically. The F9V Dev has already demonstrated two successful soft water landings of first stage.

The previous attempts aimed landing accuracy within 10 km, but this attempt is targeting a landing accuracy within 10 meters.

During the last attempt in July 2014, after landing, the first stage tipped sideways as planned to its final water safing state in a nearly horizontal position. The water impact caused loss of hull integrity.