- Laws: You are currently not allowed to use anything besides pure helium
- Osmosis: Natural separation would occur, so you would need to make sure to mix helium and hydrogen constantly.
- Cleaning: They have to constantly monitoring the humidity of the helium and have to remove it with a specialized machine on a humid day. This would not work with a mixed gas (with the current design).
- (Speculation) Do not mix it in the first place: Create a sealed off hydrogen balloon in a helium balloon. This would have other problem like different expansion based on temperature. The devil is in the details here...
> Venus has a CO2 atmosphere. Because CO2 is about 50% denser than Earth air, ordinary Earth air could be a lifting gas on Venus. This has led to proposals for a human habitat that would float in the atmosphere of Venus at an altitude where both the pressure and the temperature are Earth-like.
1. Hot air balloons get their lift from hot air; and,
2. Dirigibles can get their lift from hydrogen; thus,
3. Hot hydrogen dirigible?
Blah blah blah ... exploding dirigibles ... blah blah blah. The lifting efficiency is outrageous.
Air is about 30 grams per mole and hydrogen is two grams per mole. So going entirely weightless you could go from 28 grams of lift per mole to 30 grams of lift per mole, a 7% increase.
You'd want to be damn sure about the reliability of your thermocontroller though.
Incidentally, using 8.5% hydrogen as lift gas will make a gnat's fart of difference; the lift force is proportional to the difference in density between air and lift gas - both helium and hydrogen are way less dense than air.
My understanding is that the intention is not to create a mixture with better lift, but which is cheaper - helium being significantly more expensive than hydrogen due to supply issues.
What few sources I can find online for elemental prices suggest helium is anywhere from 2x to 10x more expensive than hydrogen, by weight. Even an 8% substitution would be economically significant at those prices - although, as the submission says, you may lose those margins through the bad reputation of hydrogen as a lifting gas.
I haven't read the article, but I presume that the use of hydrogen is a non-starter. No-one wants a flaming fireball raining down on them.
lol. tl;dr (apropos in this case): "So, 8.5% hydrogen in helium appears to be non-flammable, whereas anything above 8.7% is flammable. Eight percent hydrogen really doesn't provide much in the way of cost savings. You probably ought to consider another question concerning your airship business. Are the cost savings by using a 8.5% mixture of hydrogen worth all the trouble and effort it will take to convince your customers that the mixture is safe, as opposed to avoiding the safety questions altogether by using 100% helium?" [implied: probably not]
> but I presume that the use of hydrogen is a non-starter. No-one wants a flaming fireball raining down on them.
it'll probably work just fine on coastal or oceanic automated shipping routes. And oceanic routes would slightly mitigate the risk of someone catastrophically holepunching one with a Class IV laser.
Sorry it’s not the answer [the author] is looking for.
You can have a stoichiometric mixture that will not be flammable because both reagents would be in right proportions but very diluted in the inert gas.
And a mixture that is very non-stoichiometric can still be very flammable, no problem. The extra gas most of the time performs the same role as inert gas -- dilutes the reagents and takes away energy from the reaction. There are exceptions, though, where you can have different results depending on the mix (for example your burning producing CO rather than CO2 because of abundance of carbon relative to oxygen in the mix).
https://www.thecgo.org/benchmark/bring-back-hydrogen-lifting...
NASA has calculations of hydrogen balloons up to 90km, carrying a 10kg object. [0]
Wind at that altitude can be as much as ~50 m/s, and occasionally even travel from west to east (important for orbital launching). [1] http://www.ccpo.odu.edu/SEES/ozone/class/Chap_2/2_4.htm
Low Earth orbit requires at minimum ~6.5km/s, so launching from the equator into the right stratospheric wind could allow a 10kg launch into orbit from a balloon if it can accelerate from Earth's natural rotation plus the wind speed, totaling around 500m/s, to 6500m/s. [2]
Traditional small rockets seem to have a lower limit in the 100s of kg total mass. Using a solid microrocket(s) [3], you might be able to get a payload into orbit between 10-500 grams. I know MIT was working on this as well as micro-jet engines... [4]
[0] https://www.grc.nasa.gov/WWW/K-12/Numbers/Math/Mathematical_...
[1] http://www.ccpo.odu.edu/SEES/ozone/class/Chap_2/2_4.htm
[2] https://en.wikipedia.org/wiki/Orbital_speed
[3] https://www-bsac.eecs.berkeley.edu/projects/microrockets/mas...
[4] https://www.semanticscholar.org/paper/Performance-of-a-High-...
https://en.m.wikipedia.org/wiki/Rockoon
If you mainly care about altitude as with a sounding rocket, it can help quite a bit.
Also some launche loop designs have parts of the structure supported by inflatable members.
And there are even plans for a rather exotic airship design that could be flown to orbit with the help of solar powered electric engines:
Neat!
https://phys.org/news/2021-10-helium-south-africa-gold.html
https://us.eitidc.com/new-helium-reserve-discovered/
It seems the situation isn't nearly as bad as was purported back when the helium crisis was the hot new story.
With positive airflow around possible leaks, sufficient H2 to sustain a flame can be prevented. In a collision, gas released goes up and out of trouble.
You will get a ~8% reduction of cost, but you get other large costs like dealing with hydrogen onsite and dealing with contaminated helium. How does that re-compress? How do you make sure your mixture stays at the right percentage.
What is the purpose here?
Venting helium is expensive, but venting hydrogen is not. You can't do this with a mix but you could vent hydrogen if it's in separate internal bags. That's a possible use, but again you'd need to look at total costs.
Read up properly here for this mixing idea, but there seems little purpose -
Flammability limits of hydrogen-diluent mixtures in air https://prism.ucalgary.ca/bitstream/handle/11023/164/ucalgar... (2012)
"Hydrogen-helium mixtures fail to propagate a flame at 92% helium in the fuel mixture under atmospheric pressure (Calgary, 89k Pa) and ambient temperature. Therefore, only a small percentage of the helium in dirigibles can be safely offset with hydrogen. This is in agreement with previously reported data.
The lean flammability limits of hydrogen binary mixtures with argon, carbon dioxide, and nitrogen diluents in air for upward flame propagation appear to be very close to the limits predicted using the adiabatic flame temperature concept"
