Reusable rockets will reduce cost to space

April 18th, 2016, Published in Articles: EE Publishers, Articles: EngineerIT


When a SpaceX Falcon rocket flew itself back to its Florida launch site last December, the feat was hailed as a key step in Elon Musk’s quest to develop an inexpensive, reliable reusable rocket. But that was only half the story.  On Friday 8 April a more challenging and potentially revolutionary step was accomplished when another Falcon rocket dispatched a cargo ship to the International Space Station, then turned around and landed on a platform gently bobbing in the Atlantic Ocean.

Elon Musk believes a fully and rapidly reusable rocket is the pivotal breakthrough needed to substantially reduce the cost of space access.  “The majority of the launch cost comes from building the rocket, which flies only once. Compare that to a commercial airliner – each new plane costs about the same as a Falcon 9, but can fly thousands of times. A rapidly reusable space launch vehicle could reduce the cost of traveling to space by a hundredfold”, he said

SpaceX would prefer to fly its rockets back to the launch site, saving the time and expense of dispatching one of its floating landing pads and a fleet of recovery ships, but most of its satellite-delivery missions won’t have enough fuel left over for the rocket to make it back to land.

The Falcon 9 1st stage stand proud atop the automated drone ship "Of Course I Still Love You" in the Atlantic Ocean after the first successful ocean landing of the vehicle on 8 April. Credit: SpaceX

The Falcon 9 1st stage stand proud atop the automated drone ship “Of Course I Still Love You” in the Atlantic Ocean after the first successful ocean landing of the vehicle on 8 April. Credit: SpaceX

According to Musk, this was a really good milestone for the future of spaceflight: “It’s another step toward the stars”.  The Falcon rocket that launched a Dragon cargo ship toward orbit on 8 April 2016 likely could have made it back to the launch site, but SpaceX opted to use the mission to test its sea-landings again. Four previous attempts to land a rocket on a barge, or what SpaceX calls a “drone ship” were not successful.

The next two or three flights are going to be drone ship landings. “It’s a good opportunity for us to refine our drone ship landing capabilities something that we need to demonstrate over and over again”, said Musk

The rocket will be taken to SpaceX’s new launch site at the Kennedy Space Centre and test-fired about ten times. If all that goes well, Musk wants to resell that rocket at a discount price to a commercial customer and launch it again within  about two months. “In order for us to really open up access to space, we’ve got to achieve full and rapid reusability,” Musk said. “The cost to refuel the rocket is only $200 000 to $300 000, but the cost of the rocket is $60-million.  It’s a hundred-fold reduction.”

While most rockets are designed to burn up on re-entry, SpaceX rockets are designed not only to withstand reentry, but also to return to the launch pad or ocean landing site for a vertical landing.

In 2014, SpaceX twice re-entered a Falcon 9 first stage from space and landed it in the Atlantic Ocean. Using lessons learned from those attempts, in January 2015 SpaceX attempted a precision landing on the drone ship, nicknamed “Just Read the Instructions”.  The rocket made it to the drone ship, but landed hard. SpaceX attempted a second precision landing the following month, this time over water, and the rocket impressively came within 10 meters of its target. Unfortunately, extreme weather prevented recovery.

The Dragon cargo ship launched on 8 April reached the space station early on 11 April. The Dragon spacecraft delivered  about  3000 kilo of critical supplies and payloads for the space station crew, including materials to support dozens of the approximately 250 science and research investigations that will occur during Expeditions 47 and 48.  Dragon’s unpressurized trunk also carried the approximately 14 000 kilo Bigelow Expandable Activity Module, or BEAM, that will attach to the space station and demonstrate expandable in-space habitat technology.

Dragon will return to Earth after just over a month stay at the ISS.  Approximately five hours after Dragon leaves the station, it will conduct its deorbit burn, which lasts up to 10 minutes. It takes about 30 minutes for Dragon to reenter the Earth’s atmosphere and splash down in the Pacific Ocean off the coast of California.

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