If a part breaks down and it has no spare on the ISS, the equipment that requires the part cannot be operated until spare part arrive with the next launch. That can cause efficiency issue or even life threatening in some case. Emergency launch add costs. Workaround is to ensure there are enough spare parts on the ISS in case of emergency, but then that mean many parts need to be launched and delivered to ISS as long as they are in different shape. With a 3D printer, in theory ISS will not need to stockpile the spare part, just need to stock some materials and print it as needed. That is how it will reduce launch mass in the long run.
Agreed, it would seem that this would be a terrible thing for normal trips with the shuttle. However, for something like the ISS or other long term missions this could be a great thing. Rather than bringing a bunch of spare parts with you, you could bring that same weight in plastics and have it be used for any number of things that you need rather than a predetermined amount of replacements that you may or may not need. That can be extremely useful.
The obvious issue is that anything critical needs to be on-hand which means that they need to pre-print a few things before they are needed, or they just need to bring a starter set of parts to begin with.
I think the real thing to look forward to is when they can increase the printing size capability and start to "print" large parts to make entire space station sections or for craft that can leave orbit.
How difficult is it for a single person to look up ways for cooking food?
I'm single, and I learned this on my own as a kid through simple observation of adults.
Sheesh... with the access people have to the Internet, you have a wealth of information at your fingertips to help you in this process.
As for 3d printing food - good idea actually, but only if the synthetic food in question is designed to be actually HEALTHY for the body and can even augment natural functions (such as boost production of youthful stem-cells and enhance the immune system).
We certainly have the technology and knowledge to do so, but the problem is, given the system we live in, they will probably just make it to be as 'cheap as possible' (monetarily speaking) and end up producing things of questionable quality that are no better, if not worse than GMO foods filled with pesticides and chemicals, which after a prolonged period of time likely produce a cumulative effect in the body and end up causing problems just so you would go to the doctor and be treated.
But, I digress, perhaps it will be different. Only time will tell.
The idea of food printing is to directly create edible food from nuitrients (which is possibly man made as well instead of extract from actual food), so that it can completely bypass the processing of farming or raising live stock. A lot of time is then saved, and there is no need for extra materials or logistics for fertilizer, feeds etc etc. Sort of like a Star Trek food replicator. Will we get there in the near future? Probably doubtful anyway unless we are talking about cream like food, or cream like food being fried or dried.