'safe'?
To avoid getting dragged into the discussion of what makes a high-energy
experimental vehicles 'safe' or not, your question can be answered by it
not being totally insane. The space shuttle and used the oxygen and
hydrogen vapor for pressurizing the ET, so it is practiced.
It would be kind of weird to make the gas and liquid tanks have the same
volume. Store the gas at a higher pressure and use a regulator to step it
down. better yet, use engine heat to vaporize a bit of the propellants and
use that as pressurant. That is known as autogenous pressurization.
http://ntrs.nasa.gov/search.jsp?R=19680052838
Thanks,
Lars Osborne
On Fri, Dec 11, 2015 at 10:32 AM, Brian Feeney <alaiadesign@xxxxxxxxx>
wrote:
Is it safe to use Hydrogen and separately oxygen as pressurizing gasses?
Set up:
- Gaseous Oxygen held in a separate low pressure vessel; about 300 psi.
- Prior to ignition a valve opens allowing O2 gas release into the LOX
tank to pressurize.
- LOX tank and pressure tank are equal volume with small ullage space
allocated in the LOX tank.
- pressure will decline by 50% through the burn based on the set up, that
is mission desirable to reduce thrust proportionately.
Hydrogen gas - same set up as above pressurizing the fuel supply feed side.
Dry nitrogen available to purge tanks, feed lines etc.
If repeat firings then only LOX and fuel lines would be purged up to the
main inlet valves, not the tanks which would be re-filled - some venting
may be necessary for refill even at these relatively low pressures?
Helium is the usual choice however, cost is high and given the description
above, I don't see the added safety benefits?
All comments, suggestions welcome.
Thank you,
Brian Feeney