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What made this week’s SpaceX rocket landing historic

In what could be a big boon for deep space travel, SpaceX landed the rocket booster portion of its Falcon 9 rocket at Cape Canaveral late Monday. The feat is being described as historic and epic, but how does this mission fare in what’s been a busy year for reusable rockets?

The key difference is distance. No booster has traveled as far as Falcon 9 did last night and then returned gently to Earth. In 2013, SpaceX’s grasshopper rocket jumped about half a mile in the air and returned without destruction.

Blue Origin, a private venture backed by Amazon CEO Jeff Bezos, extended this limit in November to 62 miles. Yesterday, Falcon 9 not only pushed this milestone 130 miles above the planet, but it did so after propelling cargo — 11 satellites for the company ORBCOMM — into orbit.

Since January, SpaceX has twice tried to land the first-stage of its Falcon 9 rockets on sea-based platforms. But both attempts ended in the failure, with the rockets either crashing down sideways or quickly tipping upon touchdown.

SpaceX’s first attempt at landing a Falcon 9 rocket booster on January 10, 2015.

SpaceX made many changes to Falcon 9’s design for this week’s launch though two stand out. First, the new rocket — informally called Falcon 9 v1.1 Full Thrust or Falcon 9 v1.2 — has more thrust, which offers additional cushion as the 13-story rocket approaches the ground. The other change is obvious: the rocket landed on hard ground rather than at sea. When you examine the rocket science behind the two types of landings, as SpaceX CEO Elon Musk did in a blog post prior to launch, the change makes sense.

Landing at sea isn’t only harder because waves physically move the platform, but it also requires more energy, according to Musk:

For a sea platform landing, the Falcon 9 figure of merit is therefore roughly 300 gigajoules (GJ) of kinetic energy and for a return to launch site landing, the number is about 120 GJ.

Restated simply, a soft return to Cape Canaveral requires less than half the energy needed to land at sea. At the same time, SpaceX dropped the temperature of their liquid oxygen fuel, which packs the molecules tighter, so the rocket could hold more fuel. Overall, the rocket used yesterday is 30 percent more efficient than earlier models. The concrete landing site at Cape Canaveral is 282 feet in diameter, meaning it has approximately 30 percent more room compared to the drone ship platform used by SpaceX earlier this year.

Composite image of the launch, re-entry, and landing burns for SpaceX's Falcon-9 rocket on December 21, 2015. The rocket's booster became the first to gently landed after delivering cargo to space. Photo by SpaceX

Composite image of the launch, re-entry, and landing burns for SpaceX’s Falcon-9 rocket on December 21, 2015. The rocket’s booster became the first to gently landed after delivering cargo to space. Photo by SpaceX

Reusable rockets could be crucial for deep space exploration, according to Musk. For instance, astronauts on a future mission to Mars will need a way to leave, and reusable rockets may be the ticket off the Red Planet. Reusable rockets may also reduce the cost of space travel by a factor of 100, given aerospace manufacturers won’t need to build a new booster for every mission.

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