Most rockets are only good for one flight, and fall into the sea once their
fuel is spent. SpaceX wants to change that by adding landing legs to is
rockets
,
allowing them to be reused. Musk has said that a rocket that can return to
Earth and safely touch down could lower the cost of spacecraft by a factor
of 100.
http://www.newscientist.com/article/dn27349-spacex-reusable-rocket-crashes-in-attempted-boat-landing.html#.VS5FVJOPWk8

adding landing legs to is rockets
, allowing them to be reused. Musk has said that a rocket that can return to Earth and safely touch down could lower the cost of spacecraft by a factor of 100.
http://www.newscientist.com/article/dn27349-spacex-reusable-rocket-crashes-in-attempted-boat-landing.html#.VS5FVJOPWk8