What It's Like to Fly Richard Bransonâ€™s Virgin Galactic into Space
J Thoendell stashed this in Space
Accelerating through Mach 0.95, the aircraft wobbles as shock waves develop on its wings and tails. This is known as a burble, and it marks the entry into supersonic flight. The shock waves change the airflow over the conventional control surfacesâ€”the elevonsâ€”and render them almost useless, forcing the pilot in supersonic flight to fly entirely by trimming the stabilizers on the tail. Flying by trim is difficult to do well, but with pilots like these the passengers probably donâ€™t need to worry. At Mach 1, the pilot rolls the pitch trim aft to a pre-determined position, and the spaceship responds by bending the flight path upward at a rate that pushes the passengers straight down into their seats with a force of 2.5 Gs. The passengers are now experiencing a total of 5.5 Gs, divided between two distinct vectors, and are rotated onto their backs as the spaceship accelerates ever more steeply upward. As they approach the vertical, nearing Mach 2, the pilot rolls the trim forward to capture the position, and 2.5 Gs are stripped away. Pointing straight up, the ship rockets into air growing so thin that the aerodynamic speeds decrease rapidly even as the ship keeps accelerating through Mach 3. At around that time, after about one minute of burn, and when an onboard instrument shows that the vehicle has sufficient energy to follow a ballistic path into space, the pilots shut down the rocket motor. The effect for the passengers, who are lying on their backs, facing straight up, is to go immediately from a condition of three Gs to the zero-G state called weightlessness.
This has little to do with being in space. In fact, Bransonâ€™s passengers, now at an altitude of about 150,000 feet, are only halfway there. But even if they were all the way there, somewhere above the KĂˇrmĂˇn line, or three times higher, where the shuttle flew, it would not mean that the earthâ€™s gravitational pull had somehow been escaped. Indeed, the force of gravity at those altitudes is nearly the same as on the ground. Objects achieve low orbits not by levitation but by the energy invested in their speed: with no atmosphere to slow them down they travel so fast horizontally (at least 17,500 miles per hour) that, as they drop toward the surface, their path matches the curvature of the earth. They go into an undiminishing free fall around the planet. It is the free fall, the vertical acceleration, that produces zero Gs. This may be intuitively obvious when it comes to the initial descent from the apogee, before the atmosphere begins to slow things down, but it is equally true during the ascent, after the rocket motor cuts out and the vertical deceleration is due purely to gravityâ€™s pull, without the complications of aerodynamic drag. Pure accelerations, negative or positive, have the same effect. Slowing while going up feels exactly like falling down.
An abrupt transition from three to zero Gs is what shuttle crews went through. A shuttle commander told me it was disconcerting the first time, like stepping off a cliff into a vacuum. It helped to remain strapped into a seat for a while, and then to avoid unusual movements for the first day or two. But aboard the Virgin spaceship, this is the moment the passengers have been waiting for, and they wonâ€™t have time to get acclimated. After a pilot gives the O.K., they can push a single release button, free themselves from their straps, and go floating around. They have about four minutes of this before needing to settle down. Some may be so stunned by the rocket flight that they donâ€™t dare release, but we can assume that having gone this far most will follow through with the plan. Once they release, they can have a great time: do somersaults in midair, assume yoga positions, think lofty thoughts about life on earth, and try not to kick one another in the face. We have also entered here into the realm of projectile vomiting. Virgin Galactic insists that this will not be a problem, but presumably it will equip passengers with quick-access sick bags. Whatever happens in the cabin, the passengers are on their own; the pilots remain strapped in and cannot move aft to help.