The other day I was watching a documentary about Mars rovers, and at one point a story was told about a computer on the rover that almost had to be completely thrown out because someone dropped a tool on a table next to it. Not on it, next to it. This same rover also was planned to land by a literal freefall; crash landing onto airbags. And that’s not even covering vibrations and G-forces experienced during the launch and reaching escape velocity.
I’ve heard similar anecdotes about the fragility of spacecraft. Apollo astronauts being nervous that a stray floating object or foot may unintentionally rip through the thin bulkheads of the lunar lander. The Hubble space telescope returning unclear and almost unusable pictures due to an imperfection in the mirror 1/50th the thickness of a human hair, etc.
How can NASA and other space agencies be confident that these occasionally microscopic imperfections that can result in catastrophic consequences will not happen during what must be extreme stresses experienced during launch, travel, or re-entry/landing?
​
​
EDIT: Thank you for all the responses, but I think that some of you are misunderstanding the question. Im not asking why spacecraft parts are made out of lightweight materials and therefore are naturally more fragile than more durable ones. Im also not asking why they need to be 100% sure that the part remains operational.
I’m asking why they can be confident that parts which have such a low potential threshold for failure can be trusted to remain operational through the stresses of flight.
In: 3487
The Hubble mirror was not a minor imperfection, it was a serious flaw because the lens system used for measuring the mirror surface was built incorrectly. They ended up polishing the mirror to the wrong shape. “1/50 the thickness of a human hair” is about 2 microns, which is a HUGE error for a telescope mirror. Even an amateur Newtonian telescope you can buy for <$500 is polished to better than 0.2 micron accuracy.
Anyway, spacecraft parts do need to be extremely lightweight and still survive launch. This is achieved through extensive analysis and testing. Everything is modeled in the computer to predict the stresses and make sure it can survive the expected environment. Then every component & sub-system is tested on a vibration table, and in thermal-vacuum chambers, etc. Then the entire spacecraft is put through the same tests. Even something as large as the Space Shuttle was put on a vibration test stand and [shaken](https://www.nasa.gov/centers/marshall/history/this-week-in-nasa-history-space-shuttle-program-s-first-mated-vertical-ground.html).
Also, heritage is very important in the space industry. We try to use components and designs that have flown successfully before, because we know they work. We keep track of every component and assess its heritage; if any component is identified as a new design that hasn’t flown before, it will be replaced with something that HAS flown, or will undergo extra scrutiny.
Latest Answers