The explosion of Virgin Galactic’s SpaceShipTwo is stirring up mixed emotions as scientists, astronauts, space agency officials and others involved in the industry worldwide, express their sadness and comment on what happened over the Mojave Desert. “On behalf of the entire NASA family, I offer our deepest condolences to the family and loved ones of the pilot lost in today’s accident involving Virgin Galactic’s SpaceShipTwo, and we are praying for a speedy recovery of the other pilot," NASA Administrator Charles Bolden said on Friday. "Space flight is incredibly difficult, and we commend the passion of all in the space community who take on risk to push the boundaries of human achievement.” European Space Agency (ESA) head, Jean-Jacques Dordain also expressed his deep sadness over the tragic loss. "On behalf of the European Space Agency and its Member States, its staff and contractors, I express my deepest condolences to the family and the loved ones of the pilot who perished and I wish a quick recovery to the other pilot,” he said in a statement.

United Arab Emirates' Aabar Investments PJS, the first outside investor in the Virgin Galactic company said: "Our thoughts and prayers are with the pilots' families, and everybody at Virgin Galactic and Scaled Composites." In July 2009, Aabar and Virgin Group announced that they had agreed to enter a strategic partnership which will see Aabar take an equity stake in Virgin Galactic.

While several people expressed sadness that one pilot was killed and another was seriously injured Friday, many also said they understand the risks that come. Former NASA top space scientist Alan Stern has seats to fly on Virgin Galactic — and its competitor XCOR aerospace. He isn’t rethinking plans to fly in space at all. "Let’s not be Chicken Littles here," said Stern, now a vice president at Southwest Research Institute. "The birth of aviation was also a very dangerous time period."

But there are also voices of concern. Carolynne Campbell-Knight, a rocket propulsion scientist at the International Association for the Advancement of Space Safety (IAASS), said Virgin Galactic should "give up" following the fatal crash. "They should stop, give up. Go away and do something they might be good at like selling mobile phones - they should stay out of the space business," she said. Campbell-Knight claimed she had contacted those involved in the project in around 2009 or 2010 to raise her concerns about the use of nitrous oxide, which she said can "go bang in a very unpredictable way". 

Tomasso Sgobba, a former head of safety for ESA, said: "They operated in secrecy, which is difficult to understand. They don’t use modern techniques in putting safety into the design... I have been saying for some years now this was an accident waiting to happen."

Sierra Nevada Corporation (SNC), in the past, a subcontractor to Scaled Composites and involved with the three powered flight tests of SpaceShipTwo said that advancing space transportation and flight testing is a difficult and often challenging journey. "SNC has reached out and has offered its assistance to Virgin Galactic, Scaled Composites and the Mojave Spaceport during this difficult time," the company said. SNC also expressed its deepest sympathy to the people of Virgin Galactic, Scaled Composites and all in the Mojave aerospace community.

The New Mexico Spaceport Authority (NMSA) is greatly saddened by the events surrounding the flight test of SpaceShipTwo as Virgin Galactic is one of the spaceport's customers. "Our thoughts and prayers go out to the crew and families and to our friends and colleagues at Scaled Composites and Virgin Galactic." NMSA said in a statement. "We will continue to work with and lend our support to Virgin Galactic through this tragedy and in the coming months as we move forward."

Astronauts always fully aware of spaceflight's deadly hazards shared their condolences too. ESA's British astronaut Tim Peake tweeted: "Heartfelt condolences to the families&friends of the pioneering Virgin Galactic test pilots."

He was followed by NASA's Douglas H. Wheelock: "Our hearts go out to the Virgin Galactic team and our dear friends in Mojave. Those margins are so razor thin and so terribly unforgiving."

Canadian ISS Commander Chris Hadfield said his heart goes out to the families and friends of the test pilots who were killed or injured in "today's Spaceship 2 accident."

Former NASA astronaut Jerry Linenger, who nearly died in a 1997 fire aboard the Russian space station Mir, said that when he first met Richard Branson, founder of Virgin Galactic, he told him the first thing he’d have to worry about is liability insurance. “You will have setbacks,” Linenger said he told Branson. “That is a reality.”

Bill Nye, CEO of the Planetary Society, said the courage of both pilots and the commitment Virgin Galactic has made to space tourism will serve as inspiration as the industry continues to make space travel as safe and reliable as possible. "Space exploration has always carried great risk. Our hearts go out to the people and families of Virgin Galactic and Scaled Composites. The space exploration community has suffered a great loss today," he said. "Nevertheless, we are inspired by Virgin Galactic's commitment to the future. Space is hard, as evidenced by the catastrophic launch earlier this week. Because of the promise of discovery, we can be certain that others will step in to honor the fallen and then carry on to make space more accessible for the benefit of humankind."

The National Space Society said it stands by Virgin Galactic CEO George Whitesides and encouraged the company to press on. “We expect that the cause of the accident will be found and fixed so that the Virgin Galactic dream of ‘opening space to tens of thousands of people’ can become a reality,” said Mark Hopkins, chairman of the NSS Executive Committee.

The politicians also joined the experts and astronauts in expressing the grief over the tragedy. House Science, Space, and Technology Committee Chairman Lamar Smith and Space Subcommittee Chairman Steven Palazzo released a joint statement: “We are deeply saddened to hear of the loss of one of the test pilots during today’s SpaceShipTwo flight. Our thoughts and prayers go out to the entire Virgin Galactic family."

House Majority Leader Kevin McCarthy said his heart and prayers go out to the pilots of SpaceShipTwo and their families. "Their courage and bravery to embark on missions that will lead towards expanding man’s reach into space exemplify the ingenuity and imagination of America. Today’s devastating crash is a reminder how fragile life is in these efforts," he said. "I am confident authorities and Virgin Galactic are working diligently to learn more about the circumstances surrounding this tragedy.”