🚀 go-pugleaf

In article <1993Jan21.074446.15421@nuscc.nus.sg> Perry Morrison,
swkmorri@nuscc.nus.sg writes:
>Some time back I posted a query about dirigible/blimp control surfaces.
>Now I have another query- could a helium filled airship control its
>lift by having some internal heat delivering device such as an electric
>radiator.
>
>I'm aware hot air balloons generate lift by heating the enevelope with
>LPG flame. Could sufficient expansion be delivered by an electric/non
>combustion method?
>
>cheers
>Perry Morrison
>

Lift is not a good choice of words to describe why hot air/helium balloons and 
dirigibles "fly" -- try buoyancy.

Anyways, yes they can, but an electric heater would weigh temendous amount.
It would probably weigh less just to bring more helium along for the ride.

======================================================================
|Michael F. Kamprath                   | The University of Michigan  |
|  kamprath@space-grant.sprl.umich.edu |      Aerospace Engineering  |
|  kamprath@engin.umich.edu            |      Graduate Student       |
======================================================================

kamprath@space-grant.sprl.umich.edu (Michael F. Kamprath) writes:

>In article <1993Jan21.074446.15421@nuscc.nus.sg> Perry Morrison,
>swkmorri@nuscc.nus.sg writes:
>>Some time back I posted a query about dirigible/blimp control surfaces.
>>Now I have another query- could a helium filled airship control its
>>lift by having some internal heat delivering device such as an electric
>>radiator.
>>
>>I'm aware hot air balloons generate lift by heating the enevelope with
>>LPG flame. Could sufficient expansion be delivered by an electric/non
>>combustion method?
>>
>>cheers
>>Perry Morrison
>>

>Lift is not a good choice of words to describe why hot air/helium balloons and 
>dirigibles "fly" -- try buoyancy.

>Anyways, yes they can, but an electric heater would weigh temendous amount.
>It would probably weigh less just to bring more helium along for the ride.


   And thtow away expensive helium when you want to go down?  I think the
point of the original poster is that if heaters are used the dirigible can
go up or down without loss of helium.  But if electric heaters are too
heavy, how about gas burners, like the ones used on hot-air balloons? 
Those should be light enough, and it shouldn't be too hard to construct a
safe heat-exchange system...
   I also heard of a design that uses a hydrogen-filled gas-bag nested
inside a helium gas chamber.  Buoyancy is controlled by inflating (from a
tank?) or deflating (releasing into atmosphere) the hydrogen.  No helium
is lost, and since the hydrogen is surrounded by helium it's not as
dangerous as the Zeppelin.  I don't think it's ever been actually used though.

In article <kkobayas.727919759@husc.harvard.edu> kkobayas@husc8.harvard.edu (Ken Kobayashi) writes:
>kamprath@space-grant.sprl.umich.edu (Michael F. Kamprath) writes:
>
>>In article <1993Jan21.074446.15421@nuscc.nus.sg> Perry Morrison,
>>swkmorri@nuscc.nus.sg writes:
>>>Some time back I posted a query about dirigible/blimp control surfaces.
>>>Now I have another query- could a helium filled airship control its
>>>lift by having some internal heat delivering device such as an electric
>>>radiator.
>>>
>>>I'm aware hot air balloons generate lift by heating the enevelope with
>>>LPG flame. Could sufficient expansion be delivered by an electric/non
>>>combustion method?
>>>
>>>cheers
>>>Perry Morrison
>>>
>
>>Lift is not a good choice of words to describe why hot air/helium balloons and 
>>dirigibles "fly" -- try buoyancy.
>
>>Anyways, yes they can, but an electric heater would weigh temendous amount.
>>It would probably weigh less just to bring more helium along for the ride.
>
>
>   And thtow away expensive helium when you want to go down?  I think the
>point of the original poster is that if heaters are used the dirigible can
>go up or down without loss of helium.  But if electric heaters are too
>heavy, how about gas burners, like the ones used on hot-air balloons? 
>Those should be light enough, and it shouldn't be too hard to construct a
>safe heat-exchange system...

Hang on a sec! As Kamprath wrote, the important part here is the bouyancy.
Blimps, like the Goodyear bunch, keep a constant (or nearly so) amount of
helium in the envelope and regulate the volume of the heluim to regulate 
the lift. By pumping more air into pockets in the envelope, the pockets
expand, compress the heluim, and lower the bouyancy. 


               ______________________________
              /      |              |        \  ______
             /       |              |         \/      \
            /   Air  |              |   Air    \      |
           /         |              |           \_____/
           \_________/    Helium    \__________ /     \
            \                                  /      |
             \                                /\______/
              \______________________________/
                    |      |
                    |______|
                      


If you have seen the Goodyear blimps on the ground, there are two 
chain-saw sized motors that hang near the gondola and appear to 
start randomly. These motors regulate the helium/air ratios.

Back (way back) to Morrison's original question: could heaters be used
to expand the heluim? Yes, but since a source of energy would be needed
to maintain altitude, it would be less practical than regulating the
helium/air ratios.
-- 
________________________________________________________________________ 

   andrew whelan                                                   
     aewhelan@icaen.uiowa.edu    
       university of iowa, idaho city, ohio
________________________________________________________________________

                                                                    

In article <kkobayas.727919759@husc.harvard.edu>, kkobayas@husc8.harvard.edu (Ken Kobayashi) writes:
|> kamprath@space-grant.sprl.umich.edu (Michael F. Kamprath) writes:
|> 
|> >Anyways, yes they can, but an electric heater would weigh temendous amount.
|> >It would probably weigh less just to bring more helium along for the ride.
|> 
|> 
|>    And thtow away expensive helium when you want to go down?  I think the
|> point of the original poster is that if heaters are used the dirigible can
|> go up or down without loss of helium.  But if electric heaters are too
|> heavy, how about gas burners, like the ones used on hot-air balloons? 
|> Those should be light enough, and it shouldn't be too hard to construct a
|> safe heat-exchange system...

Heating the helium in a balloon doesn't buy you very much.  If the absolute 
temperature of the helium were doubled (from 0F to a rather toasty 490F, say), 
the He density would be decreased by a factor of two, but the balloon's lift 
would increase only 7%.  Any of the common plastic balloon envelopes like Nylon 
would probably combust before then.

  Mark Drela                          First Law of Aviation:
  MIT Aero & Astro          "Takeoff is optional, landing is compulsory"