Part 2 of 5 Parts (Please read Part 1 first)
SpaceX says that when all the components and tests have been completed, the rocket will carry the spacecraft above the Earth and then detach itself to fly back to Earth for inspection and refueling. The spacecraft will fire its engines and achieve Earth orbit. The president of SpaceX says that this might happen as early as 2020.
It will take most of the liquid methane and liquid oxygen fuel in the spacecraft section to get to Earth orbit. SpaceX says that following the entry into Earth orbit, SpaceX will launch tanker spacecraft which will rendezvous with the first spacecraft. It may take as many as a dozen refueling flights and rendezvous’ to fill the tanks of the spacecraft. One of SpaceX’s Mars development engineers has said, “We go from getting 100 tons or more into low-Earth orbit, then refill, and we can take that payload pretty much anywhere — including the surface of Mars.”
If the proper infrastructure on Mars is available, liquid methane and liquid oxygen can be manufactured and used to refuel the spacecraft that are sent to Mars by using water in Martian soil, carbon dioxide in the Martian atmosphere and electricity from the solar panels.
Musk’s plan calls for the entire spacecraft to be constructed from advanced carbon fiber Composites. Composites of carbon fiber contain huge quantities tiny but extremely strong threads made of carbon. These threads are often woven into a fabric which is then embedded in a glue-like epoxy. Once cured in an oven, the epoxy hardens into an extremely strong resin surrounding and penetrating the carbon fiber fabrics. Carbon fiber structures require only one fifth of the material need for steel structures and many types are even stronger than steel. Carbon threads are also able to be made into materials that have similar properties to aluminum but are only half of the mass of aluminum. Together you wind up with a material stronger that steel and lighter than aluminum.
Musk is convinced that the BFR will require such a construction material to live up to expectations. However, building huge structures such as the BFR with carbon fiber can be very difficult. Nothing like the BFR has ever been constructed. The Boeing 787 Dreamliner is about fifty percent composites by weight.
Musk has shown pictures of a metal cylinder about thirty feet in diameter which he said was a tool that will be used to construct the BFR. Analysts think that the cylinder is something called a “mandrel” which is used to apply carbon fiber materials. No one has ever built a mandrel as big as the object showing in Musk’s pictures. As a mandrel rotates, a robot moves along wrapping rolls of carbon-fiber tape around the cylinder.
Greg Autry is the director of the Southern California Spaceflight Initiative and an expert on the space industry. He told a reporter that “You lay layer upon layer of the material. If you're going to make a spacecraft part, you'd probably have dozens of layers of material on top of each other.”
Please read Part 3