Richard Branson's dream of commercial space tourism suffered a tragic setback in October when Virgin Galactic's SpaceShipTwo crashed in the Mojave desert, killing test pilot Mike Alsbury. Branson appears undeterred, though, writing in reflection on the accident that he believes "humanity's greatest achievements often come out of our greatest pain."

"When this story is told in years to come, I believe alongside the bravery of Mike and the incredible tale of Pete's survival, will stand the story of the commitment, loyalty, and passion of the world's first private astronauts," Branson writes. "Virgin Galactic goes on, with an unwavering commitment to safety and a renewed sense of purpose."

"Virgin Galactic goes on."

The company's commitment to safety was questioned following the October crash; The Wall Street Journal reported that Virgin Galactic may have been too aggressive in its effort to launching passengers into space, and that Branson's timeline disagreed with the company's technical outlook. A switch to a new type of fuel, engine performance problems, and other technical issues complicated Virgin's target launch date of 2015.

Since the crash, about 20 of the company's 700 potential customers reportedly cancelled their ticket to ride on Branson's spaceship (about 3 percent of the company's queue). A refundable round-trip ticket on a Virgin Galactic flight costs $250,000.

Despite the loss of a SpaceShipTwo and its pilot, Branson believes the work of his company is vital for the future of private space travel. "I found myself questioning seriously for the first time, whether in fact it was right to be backing the development of something that could result in tragic circumstances," Branson writes. "I got a very firm answer to that question immediately when I landed in Mojave. From the designers, the builders, the engineers, the pilots and the whole community who passionately believed — and still believe — that truly opening space and making it accessible and safe is of vital importance to all our futures."