We still need a smaller hydrogen tank - Public Test #2
Hydrogen tanks are too big. Many times, you're happy with a smaller tank that you don't have to design your entire ship around, that doesn't explode your grid size by 50% - you know, just a small tank for a bit of additional thrust, to refill hydrogen bottles with, or simply so you can actually use that huge amount of space for a large cargo container, and fill the niches with fuel instead of doing it the other way around and split up your cargo capacity - because that seems to be okay.
Which is something I do not understand. In any modern aircraft, the one thing you want to have big and concentrated is cargo space. The one thing that is spread out everywhere, filling every free niche... that is fuel tanks. Wings contain fuel. Spaces between the cabin and cargo compartment might contain fuel. Spaces between equipment. Especially fighter jets get bonkers on where they store fuel. Simply because the only two things you need are a) piping and b) weight and balance. Fuel doesn't care if its stored in smaller batches. You can't, however, cut big pieces of cargo in half.
For some reason, Space Engineers does it just opposite of that. The hydrogen engine tank change was a good first step - but since its not actually tank, doesn't act as a tank - ignored by thrusters, can't refill bottles, can't stockpile, doesn't refill when its not running and thus producing power, can't get the hydrogen out again whatever you try - its only adequate for those builds who only need it to power the actual engine.
We need a smaller tank. Whether thats through a new block, or something like Kuroshi suggested with using the oxygen or hydrogen tanks interchangeably is certainly worth discussing. But as it stands, that tank makes for the opposite of the small craft Keen wants us to build. They're oversized. In small grids, often two, three times the size of what they need to be with ions and atmo thrusters. If you do any sort of decorative armour, you're quickly looking at 800+ block small grids even for a tiny non-cargo ship... just because its not tiny anymore. Same goes for small large grids.
Just take a look at the old yellow boat. You could certainly save some space by rearranging the interior, but if you want to keep the interior and refurbish it to use hydrogen, its 50% bigger just by adding a single tank - even though a single thruster in every direction would be sufficient, and a smaller 1x2 tank would likely hold enough to get by. And thats not even considering the additional conveyors you would need.
As it stands, I see no sane reason for me to ever consider hydrogen for a small grid. I like my ships small and compact. A 5x5 tank only matches large containers, meaning cargo vessels - and those need more than one tank due to mass and thrusters, and thus it becomes a nonoption yet again. Not to mention that if my cargo small grids get any bigger, they'll soon become too big for ship hangars.