posted on Mar, 2 2019 @ 07:45 PM
originally posted by: Phage
a reply to: LookingAtMars
When you say "gas" it could be hydrazine.
Eeek. Put the tank down and walk away.
No, probably not. The Venera spacecraft was quite large (around 900 kg) and therefore had to have very large bi-propellant (i.e., Nitrogen
Tetroxide/Hydrazine) tanks in order to get enough velocity to escape Earth orbit. The Earth escape stage of this mission blew up while trying to
execute that burn. Usually that occurs when one of the check valves in the thrusters fails and allows the oxidizer (NTO) to leak directly in to the
Hydrazine tank. Since that fuel/oxidizer mix is hypergolic, it will cause an instantaneous explosion in the fuel tank. The tank containing the
Hydrazine almost certainly did not survive the explosion.
Hydrazine/NTO tanks typically operate at a few hundred PSI and in that era were usually constructed out of thin walled Aluminum.That pressure is
customarily supplied from thick walled Titanium pressure vessels filled with Helium to as much as 5,000 PSI, with the pressure supplied to the fuel
tank stepped down through regulators. That tank in the guy's hand is one of those Titanium pressure vessels. NASA's Venus missions from the same era
(i.e., Pioneer Venus) used the same propulsion technology. I happen to have obtained one of those Pioneer Venus era surplus pressure vessels for my
own personal collection and know exactly what they look like. One telltale feature that gives away the identity of this tank is the rather
conspicuous weld bead around the equator of the tank. These Titanium tanks were forged in two halves and then welded together. The width of the weld
bead is roughly the same as the wall thickness of the tank which, in this case appears to be about a quarter of an inch.
When new, these tanks had a short, squat cylindrical stub projecting about an inch above the outer surface of the sphere at the fill port. This stub
was drilled and tapped for a pressure fitting. NASA did studies on the re-entry dynamics of spherical vessels like this to see how likely they were
to survive re-entry. It turns out that when one of these tanks re-enters the atmosphere, there are two stable conditions. If the fill port stub is
facing backwards when the entry starts, it will be shielded from the highest temperatures of entry and will remain in that position all the way to the
ground. On the other hand, if the tank begins entry with the fill port stub facing forward, that is also stable (somewhat counterintuitively) and
will remain facing forward all the way to the ground. However, since it is projecting into the high temperature bow shock of the tank, it will melt
off, leaving only a jagged hole in the wall of the tank. That is obviously what happened here.