Space shuttle - Helium?

[Hurricane]

Hello everyone! :hello:

I have recently started studying the space shuttle's systems closely for the ssake of developing my own add-on, and stumbled upon this great article, describing the SSMEs and their way of operation. Now, it mentioned in some points the use of Helium in the space shuttle, more correctly after MECO.

So my question is, what was this Helium used for, and how did they calculate the amount they needed to carry?

~Best regards, Oz.

[P.S. I'm not sure if this is the correct forum for that, admins & mods please move it elsewhere if it's not! :thumbup:]

 

[Urwumpe]

So my question is, what was this Helium used for, and how did they calculate the amount they needed to carry?

Primarily for operating the many medium sized valves in the engine, that are too big for pure electrical operation and too small to justify hydraulics.

Second, for purging the propellant lines of gases and liquids that could damage the engine before or after its burn. a bit of helium is also used for pressurizing bearings and seals inside the engine during operation, for separating hot exhaust gases and oxygen. And for a small oscillation damper, that neutralizes pressure waves in the oxygen flow during engine operation, to prevent Pogo oscillations.

Finally, Helium is used for providing a bit of counter pressure inside the engines and the ET umbilical well during reentry, so hot plasma does not leak into the engines (or umbilical well) and damage it.

You can calculate how much you need, by knowing how much you will use valves, how long the engines operate, and how long your reentry is and how much pressure you need to keep the engines clean.

 

[Hurricane]

Primarily for operating the many medium sized valves in the engine, that are too big for pure electrical operation and too small to justify hydraulics.

Second, for purging the propellant lines of gases and liquids that could damage the engine before or after its burn. a bit of helium is also used for pressurizing bearings and seals inside the engine during operation, for separating hot exhaust gases and oxygen. And for a small oscillation damper, that neutralizes pressure waves in the oxygen flow during engine operation, to prevent Pogo oscillations.

Finally, Helium is used for providing a bit of counter pressure inside the engines and the ET umbilical well during reentry, so hot plasma does not leak into the engines (or umbilical well) and damage it.

You can calculate how much you need, by knowing how much you will use valves, how long the engines operate, and how long your reentry is and how much pressure you need to keep the engines clean.

So the Helium wastes over the flight, correct?
And the valves you were speaking of, are those the first oxidizer and fuel combustor stages?

~Take care, Oz. :tiphat:

 

[Urwumpe]

So the Helium wastes over the flight, correct?
And the valves you were speaking of, are those the first oxidizer and fuel combustor stages?

Yes, it gets ejected after it has done its work in the valve.

And no, they are all kinds of valves. The six prevalves in the shuttle are large hydraulic valves, they need much more force than what pneumatics can provide.