could you survive on just tablets ?!

Not with just a few, no. The problem you'll run into is simple quantity... on a "typical" 2,000 calorie diet, you'll need 65 grams of fat, 300 grams of carbohydrates, and 50 grams of protein (not including vitamins, minerals, or other nutrients).

The physical limitations of pills would be that a large capsule or softgel can typically fit up to 1 gram of content and the largest tablets can sometimes fit up to 1.5 grams (depending on what it's made up of). Assuming those 65 grams would be softgels, that would be 65 pills... and assuming an average of 1.25 grams per pill of the rest, that would be 280 pills for the others.

So if "minimum survival pills" were made, you would have to take at least 347 pills (65 for fat, 240 for carbs, 40 for protein, and 2 for all the vitamins and minerals) to have the basic minimums. I don't imagine most people would want to be swallowing pills all day long, but that's the basic math from the numbers. You could take liquid or powder forms for some or all of these... but then you might as well eat food and enjoy the taste instead of choking it down. ;-) I hope I helped!


[edit]: Oops, I almost forgot to mention, but the numbers listed above are the RDA levels. Some people take in less of any of these based on personal needs or dietary restrictions, but that is the "basic health" levels of nutrients. The idea from the Jetsons about full meals popping up from tiny pills can never happen without miniaturization and something to reverse it once it hits your stomach. Cool idea, but physically impossible. Sorry.

Health/nutrition and math classes, plus personal research in my role as a Product Specialist for a vitamin company