Quote from: Robotbeat on 04/30/2018 03:13 amBesides the usual performance improvements like <snip> and using hydrogen instead of methane. Again, if you're making the fuel electrically.So although SpaceX has not pursued hydrogen for a while, I expect them to return to it eventually.Quote from: Robotbeat on 04/30/2018 04:02 amLong term on-orbit storage is irrelevant for point-to-point transport. Also is a solvable problem.Hydrogen is doubtless a solvable problem. And every solution you come up with is not worth the added cost in dollars.The entire storage - transportation - loading - storing - design - fabrication - using chain gets meaningfully more expensive as soon as you introduce hydrogen to it.If I would expect to see that to become a near term reality I could bet a small amount of money on hydrogen never being competitive even if the cost of electrolysis and electricity goes so low electrolysed synthetic methane becomes cheaper than any and all natural gas. That in such a case your operations, safety and hardware all combined end up cheaper if you compare hydrogen against methane.Hydrogen is a solvable problem, at a higher ticket price per passenger seat mile.
Besides the usual performance improvements like <snip> and using hydrogen instead of methane. Again, if you're making the fuel electrically.So although SpaceX has not pursued hydrogen for a while, I expect them to return to it eventually.
Long term on-orbit storage is irrelevant for point-to-point transport. Also is a solvable problem.
Hydrogen is terrible for cars, but if you get high enough scale, it may make sense for things that can’t be easily electrified (like rockets). When the cost of fuel becomes dominant, then it should be considered.I like methane as a rocket fuel and it’s the best choice for BFR right now, but sorry if I’m not in the hydrogen-phobia cult.
Hydrogen on earth may make sense once we have started producing fuel from regenerative power sources or nuclear. Not as long as the source are fossil fuels. On Mars hydrogen will be produced as part of methane production. It is an easier step there, going outward.
But if you generate and distribute very near point of use, such as major space ports, then leakage and distribution cost is small.Hydrogen can make sense at large scale, not at small.
storage of hundreds of tons for only about an hour
The surface area to volume ratio is vastly different, and the state of matter (liquid vs gas) is also different. You have to recalculate.
It's not about hydrogen being a superior storage method,
it's that it has the fewest steps
and fewest losses
You're not storing the hydrogen for long.
When the cost of fuel becomes dominant, then it should be considered.
Quote from: Robotbeat on 05/05/2018 05:06 pmWhen the cost of fuel becomes dominant, then it should be considered.We still haven't even reached the point where a car costs less then it's lifetime fuel... I do admire the forward thinking though!
Quote from: Dave G on 04/29/2018 09:37 amThe President and Chief Operating Officer of SpaceX said 5-10km offshore. She wouldn't have said that unless SpaceX had analyzed all aspects of the offshore pad at those distances, including sound.In the absence of any information, speculation is fine. It's part of what makes this a great forum.But when we have it straight from the horse's mouth, speculation otherwise seems pointless.For example, many of us here speculated that BFR specs from horses mouth at IAC 2016 would change. They did. When far off plans meet reality, especially when they are not engineering constrained, but regulatory, they have an even greater risk of change. SpaceX statements are not stone tablets to be worshiped without question, but current plans subject to change over the many years before possible fruition. I had thought SpaceX was notable for its ability to change course on the fly to adapt to reality intrusions and opportunities previously unknown or not sufficiently vetted. I doubt that BFR P2P is sufficiently vetted as of 2017.
The President and Chief Operating Officer of SpaceX said 5-10km offshore. She wouldn't have said that unless SpaceX had analyzed all aspects of the offshore pad at those distances, including sound.In the absence of any information, speculation is fine. It's part of what makes this a great forum.But when we have it straight from the horse's mouth, speculation otherwise seems pointless.