[DOC] [TLE] Patent US5143322 - Ground handling, altitude control and ... - Google [PAR] ... an airship hull or envelope to enclose air-filled ballonets and a lifting gas. ... the 
air pressure in the ballonets, thus forcing compression or allowing expansion of 
the ... non-rigid, pressurized airships can be built and the many advantages to 
this type ... to the other could be a problem if the pitch attitude is allowed to 
change. [DOC] [TLE] Patent US5143322 - Ground handling, altitude control and ... - Google [PAR] Sep 1, 1992 ... The invention involves an airship hull or envelope to enclose air-filled ballonets 
and a lifting gas. ... thus forcing compression or allowing expansion of the lifting 
gas. ... Also, the single cell airship has been flying for many years, and this ... the 
other could be a problem if the pitch attitude is allowed to change. [DOC] [TLE] Airship - Wikipedia [PAR] An airship or dirigible is a type of aerostat or lighter-than-air aircraft that can 
navigate through the air under its own power. Aerostats gain their lift from large 
gas bags filled with a lifting gas that is less dense than the surrounding air. .... As 
altitude is increased, the lifting gas expands and air from the ballonets is expelled
... [DOC] [TLE] Airship Design Issues - GlobalSecurity.org [PAR] Nov 7, 2011 ... Rigid airships are much more expensive to produce than the nonrigid ... As this 
occurs the lifting gas must be allowed to expand for two reasons. ... The ballonets 
are filled with ambient air and expand and contract ... As the airship rises and the 
helium expands within the main envelope, air in the ballonets is... [DOC] [TLE] Material Challenges for Lighter-Than-Air Systems in High ... - TCOM [PAR] such as helium or hydrogen which is contained in the envelope. ... aerostat is 
very power efficient, requiring no power for station keeping or altitude control. ... 
During ascent, the lifting gas in the hull is allowed to expand while air in the .... 
based material, demonstrated much higher strength/weight ratio and excellent 
tear... [DOC] [TLE] Blimp Prezi (Gases Project) by Mark Nielsen on Prezi [PAR] Blimp Prezi (Gases Project) ... If blimps didn't have air filled ballonets they would 
... First off, they would not be able to control what height they hovered at, and 
would be little ... Without ballonets the envelope would expand as the blimp rose 
higher above ... lower pressure at higher altitudes impacts the volume much more
. [DOC] [TLE] X-Plane and Balloons - Chuck's Overview - X-Plane.Org Forum [PAR] Oct 21, 2011 ... Lighter-Than-Air in X-Plane By Chuck Bodeen Buoyant Lift X-Plane has a feature 
that is ... The gas bag passive and is free to expand within the envelope. ... an 
envelope which contains as many as 16 ballonets filled with a lighter gas. .... 
Instead I have made the throttle control the hot air balloons 'burners'. [DOC] [TLE] Airships facts, information, pictures | Encyclopedia.com articles ... [PAR] An airship is a large lighter-than-air gas balloon that can be navigated by using ... 
Filled with hydrogen gas, it was driven by a 3 hp steam engine weighing 350 lb (
160 kg), ... Many of the large passenger-carrying airships using hydrogen instead 
of .... envelope pressure controls to regulate helium and ballonet air pressure;... [DOC] [TLE] How airship is made - material, manufacture, history, used, parts ... [PAR] An airship is a large lighter-than-air gas balloon that can be navigated by ... Filled 
with hydrogen gas, it was driven by a 3 hp steam engine weighing 350 lb (160 ... 
Even though Giffard's airship did achieve liftoff, it could not be completely 
controlled. ... Ballonets are usually made of a fabric lighter than the envelope's 
because... [DOC] [TLE] Hydrogen and Helium in Rigid Airship Operations | Airships.net [PAR] Although helium weighs twice as much hydrogen, because each gas is so much 
.... No balloon would be able to expand with the explosion and then shrink after,

Question: Air-filled ballonets control how much this gas is allowed to expand in the envelope
Answer: helium