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If helium gets really expensive, they could switch to hydrogen. Maybe even switch inflight, by replenishing lost helium with hydrogen. Maybe by hydrolysis. For

If helium gets really expensive, they could switch to hydrogen. Maybe even switch inflight, by replenishing lost helium with hydrogen. Maybe by hydrolysis. For a plane operating in remote areas at altitude, the explosion risk is not an issue.

0db532a0 8y ago
That is an interesting idea, and I don’t know why this has been downvoted.
- TimTheTinker 8y ago
  Sounds kind of ludicrous to propose switching from helium to hydrogen in flight to save on the cost of helium. You’d still have to buy the helium (how else does it get off the ground?). Probably more if you intend to safely bring it back down.
  - 0db532a0 8y ago
    The idea I got was that for long-term flights, the helium would be used for launch, and lost helium would be replaced with hydrolysed hydrogen. Doesn’t sound too unrealistic.
    - TimTheTinker 8y ago
      That makes sense, thanks. I apologize for my acerbic ignorance in the above comment.
TimTheTinker 8y ago
You could switch in-flight, but you would actually increase the gas costs since you’d need 100% helium for the trip up as well as the trip down. Also, the risks would dramatically increase in exigent circumstances. What if the gas container fails, causing it to make an unexpected descent? Even for a planned descent, there has to be a way to switch back to helium. So now you have to have at least 2 times the helium needed to attain buoyancy, plus mechanisms to generate hydrogen and vent/replace gas. And systems/procedures to handle edge cases. It sounds like a lot of complexity and cost added. However, it might be worth it if extremely high altitude is needed. The altitude ceiling could be increased significantly (not sure how much, but <2x) for a given configuration and payload.
- kcolford 8y ago
  But for an expendible aircraft you don't need it to be buoyant on the way down. Just have a failsafe that dumps the hydrogen into the atmosphere below a certain altitude/air pressure.
  - TimTheTinker 8y ago
    That’s true. But there have to be applicable regulations around dropping expendable aircraft remains over populated areas.

0db532a0 8y ago

That is an interesting idea, and I don’t know why this has been downvoted.

TimTheTinker 8y ago
Sounds kind of ludicrous to propose switching from helium to hydrogen in flight to save on the cost of helium. You’d still have to buy the helium (how else does it get off the ground?). Probably more if you intend to safely bring it back down.
- 0db532a0 8y ago
  The idea I got was that for long-term flights, the helium would be used for launch, and lost helium would be replaced with hydrolysed hydrogen. Doesn’t sound too unrealistic.
  - TimTheTinker 8y ago
    That makes sense, thanks. I apologize for my acerbic ignorance in the above comment.

TimTheTinker 8y ago

You could switch in-flight, but you would actually increase the gas costs since you’d need 100% helium for the trip up as well as the trip down. Also, the risks would dramatically increase in exigent circumstances. What if the gas container fails, causing it to make an unexpected descent? Even for a planned descent, there has to be a way to switch back to helium. So now you have to have at least 2 times the helium needed to attain buoyancy, plus mechanisms to generate hydrogen and vent/replace gas. And systems/procedures to handle edge cases. It sounds like a lot of complexity and cost added. However, it might be worth it if extremely high altitude is needed. The altitude ceiling could be increased significantly (not sure how much, but <2x) for a given configuration and payload.

kcolford 8y ago
But for an expendible aircraft you don't need it to be buoyant on the way down. Just have a failsafe that dumps the hydrogen into the atmosphere below a certain altitude/air pressure.
- TimTheTinker 8y ago
  That’s true. But there have to be applicable regulations around dropping expendable aircraft remains over populated areas.