3 ms·
The other problem with hydrogen is that it is hard to contain. Leakage and permeability of the envelope would probably end up being a bigger engineering concer
by evgen 8y ago
The other problem with hydrogen is that it is hard to contain. Leakage and permeability of the envelope would probably end up being a bigger engineering concern than would flammability.
- m0zg 8y agoAnd yet another problem with hydrogen is that unlike helium it is reactive, including with some metals. And those metals tend to become brittle fall apart after a while: https://en.wikipedia.org/wiki/Hydrogen_embrittlement https://en.wikipedia.org/wiki/Hydrogen_embrittlement
- philipkglass 8y agohttp://usa.dupontteijinfilms.com/wp-content/uploads/2017/01/Mylar_Chemical_Properties.pdf http://usa.dupontteijinfilms.com/wp-content/uploads/2017/01/... See Figure 2, Gas Permeability of Mylar vs. Temperature Helium permeates Mylar significantly faster than hydrogen over the full temperature range tested. It looks like the helium permeation rate is nearly double that of hydrogen near room temperature. Surprising! I would have guessed that lighter gases permeate faster. Note on the same figure that oxygen permeates faster than nitrogen even though it's heavier. There is more tabular data here: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690004779.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/196900... It confirms the same trend. Helium permeates Mylar faster than hydrogen.