As for the Starship upper stage, the vehicle began losing the ability to control its attitude during its coast phase in space. This was found to be due to clogged valves used by reaction control thrusters on the upper stage. The company’s update notes that “SpaceX has since added additional roll control thrusters on upcoming Starships.” But it is not clear that they will be available for Flight 4.
This seems like a slightly strange conclusion. Since the main goal for IFT-4 is to survive reentry, why wouldn’t they upgrade the RCS system to address issues found during IFT-3? Or if it’s too late to upgrade, skip S29 entirely?
Goal is to get data on reentry, if it can be achieved with small modification on already build SS, than why not. I’m bit surprised by number of clogging problems in test flight 2 and 3.
What can possibly clog filters on booster? Not like LOX get to tank unfiltered. Some form of ice, but what can from ice there except LOX itself. Any water and CO2 should be purged before fueling by nitrogen.
That’s the big unsolved question. Easiest answer is that they are using preburner exhaust to pressurize the tanks, but putting CO₂, CO, water vapor and maybe a trace of unburned methane into an oxygen tank sounds like such a bad idea - but like you, I can’t think of anything else that could block the filters.
CO2 will froze and sink in LOX tank, water ice will float. SO both clog the lines. I was under impression that they pressurize tanks by pure oxygen.
water ice will float. SO both clog the lines
If water ice floats, wouldn’t it not clog the lines until you run out of propellant, in which case the clog is moot?
I was under impression that they pressurize tanks by pure oxygen
That was my impression as well. I wish I could figure out where people are getting the idea that they are using combustion exhaust to pressurize the tanks. Seems like a weird idea to me.
If there’s nothing that the filter can catch, why are there filters?
Easiest answer is that they are using preburner exhaust to pressurize the tanks
Has there been any evidence that they are doing this? I’ve seen this mentioned in a number of places, but it seems mostly like speculation.
That said, I can’t think of any other source of filter clogs, unless one of the workers left their hat or something inside. Perhaps Tim Dodd can clarify this during his upcoming Starbase tour.
