Lift Proposal: 50% Helium, 50% Hot Air

Instead of venting expensive helium to change the weight, half of the lift could be provided by helium and half by hot air. To descend, you would vent hot air, and to ascend, you would turn up the burners.

It would be interesting to do a trade. If 50% of the lift is provided by hot air, the hot air part of the envelope will be substantially bigger than the Helium part.

I believe the hot air lift should only support a little more the payload and the He or H2 should support the weight of the craft. This allows for variance of lift to make for easier operations while minimizing size. 

Except  for the fact  Hot air likes to stay in a  bubble shape . That is,  it  remains its hottest  the longest   being in a  sphere shape. It takes  an  elaborate  burner system  to  heat  a foot ball shape  evenly.   If you don't,  the hot air  will slosh  , cooler air  running down hill   hotter air  running up hill and your  ship is out of balance.    This is the problem  the first hot air airships ran into.   

<<<I believe the hot air lift should only support a little more than the payload and the He or H2 should support the weight of the craft. This allows for variance of lift to make for easier operations while minimizing size. >>>

I agree. Hot air is an almost-free buoyancy-adjuster. It can be supplied by the generator's exhaust and by its air cooler stream, so it doesn't cost any added equipment such as burners and propane tanks. When the dirigible wants to descend, it diverts the heat stream out of the ship and soon the ship will cool off and go into negative buoyancy. If you've watched a hot air balloon operate you'll notice how it bounces along, requiring a hot air blast every few minutes. i think that hot air would work well as an altitude manuevering method. Slow but good.

   Hot/cold air "Slosh" shouldn't be a problem since one wouldn't put hot air into the main envelope, probably only into one center-of-lift buoyancy bag, something like a ballonet. Granted, since hot air only has half the lift of H2, this bag would have to be twice as big as the H2 reservoir and thats a lot of bag.

Upsoon!

Just like on a hot air balloon, you'll need a dump valve to dump the hot air as needed. Over all I still think the hot air option is going to make the ship so much bigger that the excess drag won't be worth it.

There has to be a point where the amount of lift provided by the helium out wieghts the size of the hot air envelope. its probalby some thing like 70-30 this Idea has already been explored though look up helium hot air hybrid ballons. There is a wiki for them not much but it exists for this Idea though why not just make a resonaby sizabull hole and let the hot air be on top of the helium secondly who says that the hot air has to come from directly below.

You are correct Dude ,  the parachute top  is  a must have   and  required  for  hot air .   Its  the main safety  to  prevent  damage  to the  envelope   and  crew,  when landing  so  the  Balloon  deflates  rapidly    loosing lift and  resistance to the wind. from its size  so it  wont  get  dragged  by  the  wind ,  BECAUSE OF its large profile to the  wind.   Even in  very light  wind   5 mph,  when  your  inflated  and  ready to  launch , its  a hand full for  2 guys  to   try  to keep it  from swaying  to much.  The  key  word here  is TRY.  You  will never  stop it !  All you can  do  is buffer  or counter it  some .
 It is  also used for  emergency  decent when operated manually and  carefully, for  venting  some of the hot air out.  Not  "ripped out"   like when you land.  Once ripped out ,  it  Will  not  re-plug the hole.  The parachute top  is held in place  by  velcro  strips  , when you pull  slightly on the line  it  puckers the  parachute top around the  edges    letting  hot air breach  around it .   Pull it  hard  and  far  and the  velcro  tabs  let go  and the  hole opens in the  balloon  top. It can not be  put back in place in flight.   
  You  have to have  a "flame zone "  from the top of the  burner   to the  crown of the balloon.   If this distance is not  kept  to known  standards   it will melt  the  fabric,  or  severely  weaken  it   so it will  have to be  replaced  very soon.  250  degrees  is the  do not exceed  temp  at the  crown .  Normal   flights  see  200 to 220 degrees.  You  really have to pay  close attention to the crown  temp. Mater of fact  being  a PIC of a HAB,  thats  your  #1 job  when  flying.  How  do I know  this stuff ?  I'm in training  for  a C rating  for  HAB.        I dont  see any  way  for  a  He./  HAB   hybred  to   work.   

It is called a roziere balloon.
 

This is not something that anyone is going to put a propeller on and fly sideways!

Or  even   to  afford to  build .   With Fossets  and  Sir Bransons wallets maybe. 
   Its  just not doable   in an airship.   Unless  there  was a way to  super heat the  air   and  "pipe and  disburse " it into the  hot air chamber for a low profile  . A complete  new  engineering challenge  costing   ...how much...!?!?!    A typical  burner   system  will not work.  The  height  you  need  to  the  crown of the hot air  chamber  to  keep  the  fabric  from  melting,  will make  the  ship  HUGE to  get  a  flyable  airship shape    .  As in the  size you  see  in   current hot air  airships and  which  are  comparable to  the  helium  filled 4 -6  passenger   Airships.   HUGE!     

I don't think there are any insurmountable problems here. I think using aerodynamics for lift variance is easiest, but gas heating is the second easiest IMO. 

Besides you don't have to use propane burners for heat. You could use solar heating or waste heat from engines. And you don't have to heat air, you could heat helium of hydrogen. Lots of options.

My personal Goals Are not 5-6 passengers I would be happy with just one me. Secondly even a 5-6 passenger helium  or hydrogen blimp is huge my initial musings on this was to get the 500 lbs of lift I want its 100' by 10' by 15' that preaty dam big. Keep in mind my target price is 40K not 10 if i really wanted to go cheap I would just through an engine of cluster ballons. Your lift perhaps need not be 50 / 50 maybe its 70 / 30 heli / hot air with a much smaller hot air envelope smaller burner etc etc.I mean there are plenty of hot air airships out there like the sky yatch I really dont see the big challenge of adding a littel helium to the top of the envelope and doing 70 / 30 hot air / heli. So at the very least I think this is viable. Also I remember reading some place that the heat delivery system does not add to the total wieght under the Utra light ruels for LTA ships. Also  even if the heat coming right from the propane burner is too hot and a littel more room between it and the rest of the ship. Again another option is make your own no offense but propane isnt rocket science Ideal with it alot as a home brewer and its not all that complicated.

He. on top  may be workable .   However you may  find it  difficult to  manage  while inflating   with hot  air   in all but dead calm air .  It would have to be  guyed    to prevent  shifting around. 
  The  He lift  would have to be enough to  lift all  the  fabric envelope.  .  Exhaust  gas or solar  could help  with  keeping the  air warm , but  not  a lot  in the  size ship  your looking at (smaller solar target) .  You  need to  see and maintain  200 to 220  degrees  in the hot air chamber to get any usable lift from hot air.  In colder to cold weather  , 180 - 200 degrees. will get good lift. So how  are you going to  keep  5- 6 thousand  sq foot of space  at a constant  200 degrees ?  and able to reheat it all  fairly quickly. This is a primary  control function for altitude control.  Even  with  lifting body or  elevators in place . The hot air  just keeps the  ship in  a flyable  trim weight   to gravity  situation so  they  work. If your ship goes heavy , losses balance,   they  are not going to  work  well. There has to be a quick way  to  add heat  to regain balance      

the sky yatch guys pitch there ballon to keep it all going in one direction that could be a good solution to most of the problems you face personally if i was going to work any desing like this i would use a ratio of neutral wieght and then use the hot air for lift that would be 3810 cubic feet of helium for 254 lbs  then hot air for lift after that so considerable less gas use and alot more hot air than LTA gas It wold all be about envelope design is sapose.  

It would be more about designing the  burner system   FOR the airship  shape 
 The  Sky yacht uses  a  shaped  hot air balloon  for all practical  purposes .   Flame zone height makes it   A very odd looking , but lovable and  funny at the same time ,  Airship  using  typical HAB  burners. . So   the  burners  need to  be  some how  re done  . The  same BTU output ( maybe slightly less due to the lift gas )   But divided by  smaller  and many  flame out puts  along the keel  of the airship  for  even  heating.  Which  is  another function of the Sky Yacht's shape  of  more  roundness.  That is  for the  flame  plumes heat to  mushroom after hitting the top , into all  parts of the  envelope  evenly.   Longer  than tall  airships  have  a problem  with  slosh  or uneven heating =  uneven lift.   The  design  would need  smaller  flame  height  requirements  but many  points of  flame  output for a good BTU output. along the very bottom keel length of the ship for  even heating.       

I just had a great idea about putting hot air balloons inside an airship envelope and the rest be filled with helium but then i read a post about helium getting "lighter" when heated. So i say just put heating elements in the gas bags and that would be a good way to "land" or go higher

I'm  still at odds  with  putting  somethin that hot   inside  a  fabric  air tight  chamber and having everything sturdy  and  secure  so  the  envelope wont get  melted if  something  sways .     I would much rather  pump  the  gas out  into  a  fixed in place heat exchanger  to  heat it  and  then  back in  the bag in a continous  cycle.  untill it  needs  to  cool   for less lift.   If  this  heat  exchanger  were  copper coils  around  an  exhaust   manifold  or  cadalitic convertor   that  the gas  was  pumper  through ,  that  just  might  get it  ?  

By the same token, I don't like the idea of piping hydrogen around outside of the envelope. More pipes, more potential for a leak near a hot engine. That approach would be fine for helium though. 

You could put a squirrel cage around a heat exchanger inside the envelope. That way the hot surfaces would become much more isolated from the fabric.