<P> Modern hot air balloons are usually made of materials such as ripstop nylon or dacron ( a polyester ) . </P>
<P> Modern hot air balloons are usually made of materials such as ripstop nylon or dacron ( a polyester ) . </P>
what is the envelope of a hot air balloon made of
what is the envelope of a hot air balloon made of
ripstop nylon or dacron ( a polyester )
ripstop nylon or dacron ( a polyester )