A personal jetpack is something few people will ever attain. While this is one of life's greatest disappointments, a jetpack is probably a lot more dangerous than useful. Therefore, it is actually better off that not everyone is rocketing around with jetpacks.
However, there are some situations where jetpacks would be extremely safe to use, such as when one is otherwise at risk of dying. It is for these instances that Safety Hot Air Balloons should be worn in largish, but still wearably sized backpacks.
Designed much like automobile airbags, Saftey Hot Air Balloons open vertically when triggered, much like a parachute does when someone is freefalling. It opens up quite rapidly like that because a combination of compressed air and inflammable gas is rapidly released into the envelope from pressure vessels. This air and gas is detonated a few moments after when the propane buners ignite.
The detonation rapidly expands the balloon envelope many meters in diameter, and heats the air inside to a high degree. The balloon immediately starts to ascend, dragging your unconscious body from out of the dirt where it layed you down when it inflated, and off the ground to safety.-- rcarty, Sep 03 2012 Cloudhopper http://en.wikipedia.org/wiki/CloudhopperThe objective. [8th of 7, Sep 03 2012] Fulton surface-to-air recovery system http://en.wikipedia...air_recovery_systemPrior Art [8th of 7, Sep 03 2012] //a combination of compressed air and inflammable gas is rapidly released into the envelope from pressure vessels.//
This is not looking good ...
// This air and gas is detonated a few moments after when the propane buners ignite. //
Yes, thought so. Not good. Not good AT ALL ...
// The detonation rapidly expands the balloon envelope many meters in diameter, and heats the air inside to a high degree. //
That part, you got right.
// The balloon immediately starts to ascend, //
Well, actually the fragments disperse in all directions ...
// dragging your unconscious body from out of the dirt //
If you weren't unconscious before, then you certainly will be after the nicely stoic fuel-air explosive detonates ...
// where it layed you down when it inflated, and off the ground to safety. //
<Arthur Dent>
“Ah, this is obviously some strange usage of the word 'safe' that I wasn't previously aware of”
</Arthur Dent>
Compressed air, yes. Flammable gas, yes ... but detonation ? Nononononnono !
This idea can actually work, but the heat-producing reaction needs to proceed at a fairly modest and controlled rate. Firstly, you need a "cool shot" to at least partially inflate the envelope - then a sustained input of heat to give it buoyancy. After all, this is nothing more than a self-deploying Cloudhopper <link>
Please, let us assure you that you don't want or need detonation. Anything beyond rapid oxidation, or simple combustion, will be risky. You might just about get away with deflagration. Detonation of any sort in close proximity to a human body is a Bad Thing. A standard azide electrical detonator, containing a minute amount of primary explosive, will remove your hand above the wrist in milliseconds. We speak in this case from direct observation.-- 8th of 7, Sep 03 2012 When I say detonation I mean combustion, but really mean detonation. Originally I thought If the mixture detonates, but the extent of the explosion is only a few meters in diameter, it could all happily occur within the confines of the envelope.-- rcarty, Sep 03 2012 What part of "No" don't you understand ?-- 8th of 7, Sep 03 2012 I've always liked this part of the Fulton story:
"(the pig)... arrived on board uninjured but in a disoriented state. Once it recovered, it attacked the crew"
One could hardly blame the pig.-- normzone, Sep 03 2012 Indeed, it does seem a little unfair to use a harmless, innocent dumb animal in such circumstances, when they could so easily have got a Marine ...-- 8th of 7, Sep 03 2012 Do you mean no, as in "no, it can", or as in "no, it can't?"-- rcarty, Sep 03 2012 The latter.
We refer you to the published work of Robert Boyle, the General Gas Law, and the Wikipedia article on the Oppau explosion.
And before you ask, it had nothing to do with us. Nothing whatsoever. We were nowhere near the place. We have never been there and don't even know where it is, let alone the times of the buses from Frankenthal ... and we have 43 witnesses who will freely testify that we were enjoying a fish supper in Adelaide at the time.-- 8th of 7, Sep 03 2012 Okay, detonation bad. In imagination land words mean what they are wanted to mean.
What would be a reasonable amount of time to expect this sort of safety balloon to inflate?-- rcarty, Sep 03 2012 Unless you're wedded to the idea of having the thing inflate right out of the backpack, you may want to consider lofting it up aways then inflating it.-- FlyingToaster, Sep 03 2012 // a reasonable amount of time //
About thirty of your Earth seconds.-- 8th of 7, Sep 03 2012 What if it inflates to a massive 'Wacky Waving Inflatable Arm Flailing Tube Man' that bashes your opponents to smithereens?-- rcarty, Sep 03 2012 could be done as a sequence: a detonant contained (tamped) within a deflgrant. Something like multi-stage fireworks. Good luck with the envelope material though.-- FlyingToaster, Sep 03 2012 // Something like multi-stage fireworks. //
Sp. "Assisted suicide".-- 8th of 7, Sep 03 2012 random, halfbakery