Part 4 of 5 Parts (Please read Parts 1, 2 and 3)
Steve Nutt said, “There are so many different parts of this thing, the complexity is daunting. There will have to be a variety of materials and joining methods to accomplish everything this has to accomplish. When a metal part gets damaged, there's usually a dent or a scratch or something like that. With composite parts, there can be damage and no manifestations at the surface. It's all subsurface.”
All of the carbon fiber sections will have to be carefully checked for flaws in every square inch with ultrasound scanners. Cáceres said, “You may have some structural problems on an aircraft, but the aircraft won't explode," Cáceres said. "But on a rocket, leaks, cracks, and instability — those things can be catastrophic. It explodes and people die. When you're building something this big, the only real way to test it is once you've completed it, and you launch it. You better have a lot of money, because you're probably going to go through a lot of big, big structures before you get the one that works.”
SpaceX has suffered serious accidents and failures with its current fleet of rockets. Musk will certain run extensive tests and checks on components and, ultimately, on the full prototype of the BRF before any missions are flown. Nutt said, with respect to going to Mars, “It's such a long mission. I think the chances of some kind of damage or failure en route are much greater than a mission of days or weeks that we've seen in our lifetime.”
Tiny pieces of rocks or comet dust in deep space can be very dangerous to a spacecraft because they are traveling at thousands of miles per hour. One strike by a tiny object could cripple and end a deep-space mission if it does not have the ability to carry out repairs during the mission. Nutt said, “Those things can go right through any kind of structure and do a lot of damage.”
It is very hard to repair carbon fiber composites even on Earth. Some jet fights employ carbon fiber composites. If there is a hole in a section of the fuselage, workers sand and polish the damaged area, use trowels to lay down layers of fresh epoxy, put the damaged section in a vacuum chamber and subject it to heat.
Nutt said, “Things that you might be able to repair with some difficulty on Earth are orders of magnitude more difficult to execute and accomplish in space. It's a big structure with a lot of components. The chances of failure are not zero. So you have to worry about those things and have contingency plans for all of them.”
Cáceres said that each launch of the BFR may costs around ten million dollars with most of the cost being for fuel because each BFR will be used many times. SpaceX’s Falcon Heavy launch vehicle costs about one hundred million dollars for each launch. Each Falcon Heavy can only lift half the weight that can be sent into space by the BFR.
Please read Part 5