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Hope to see the changes to the flight control software & header tanks work! The last flight was neat, just seeing it perform the belly flop maneuver. Today we m

Hope to see the changes to the flight control software & header tanks work! The last flight was neat, just seeing it perform the belly flop maneuver. Today we might see it land if there's enough pressure in the reserve tanks. What's insane about this flight profile is that fuel tanks aren't supposed to do this. The flip it does right before it hits the ground makes all the liquid fuel splash around and slosh to one side. So instead, it uses some of the hot gasses from the rocket engine to pre-heat a small amount of fuel and use it to pressurize a small reserve tank that is used to get the engines going. One of the causes of the explosion from the last test was that they ran out of pressure in the fuel tank, causing oxidizer rich combustion which eventually burnt up the engines. So hopefully they tweak the system a little and we get to see a belly flop and a successful landing!

_Microft 6y ago
> So instead, it uses some of the hot gasses from the rocket engine to pre-heat a small amount of fuel and use it to pressurize a small reserve tank that is used to get the engines going. I think they are still using helium or nitrogen to pressurize the tanks. Autogenuous pressurization is definitely what they want to do (or „have to do“ if you like) but afaik they are not there yet.
- emilecantin 6y ago
  They were using autogenous pressurization for SN8, and that's what failed with the header tanks on landing. For SN9's flight (hopefully today), they'll just use regular helium pressurization for the header tanks. It's a temporary fix to continue testing the rest of the system while they work that particular kink out.
piquadrat 6y ago
> causing oxidizer rich combustion which eventually burnt up the engines Which sometimes is called "engine rich exhaust". I love these sarcastic terms in rocketry. RUD, lithobraking, etc.

_Microft 6y ago

> So instead, it uses some of the hot gasses from the rocket engine to pre-heat a small amount of fuel and use it to pressurize a small reserve tank that is used to get the engines going. I think they are still using helium or nitrogen to pressurize the tanks. Autogenuous pressurization is definitely what they want to do (or „have to do“ if you like) but afaik they are not there yet.

emilecantin 6y ago
They were using autogenous pressurization for SN8, and that's what failed with the header tanks on landing. For SN9's flight (hopefully today), they'll just use regular helium pressurization for the header tanks. It's a temporary fix to continue testing the rest of the system while they work that particular kink out.

piquadrat 6y ago

> causing oxidizer rich combustion which eventually burnt up the engines Which sometimes is called "engine rich exhaust". I love these sarcastic terms in rocketry. RUD, lithobraking, etc.