Quote from: cordor on 05/20/2012 03:24 amTo do cross range, falcon need to boost dragon into higher orbit, there, dragon wait for iss pass by, and then dragon decelerate into lower orbit to meet iss. that is not the definition of cross range. Yaw steering takes out cross range
To do cross range, falcon need to boost dragon into higher orbit, there, dragon wait for iss pass by, and then dragon decelerate into lower orbit to meet iss.
Even if the engine avoided disassembly the unburned kerosene would screw up the burnout mass, leading to underperformance.
Does SpaceX make these check valves themselves? Or do they buy them?Anybody know?
Quote from: deltaV on 05/20/2012 12:10 amEven if the engine avoided disassembly the unburned kerosene would screw up the burnout mass, leading to underperformance.No. Modern rockets fly with adjustable mixture ratio in flight to ensure both burn out nearly simultaneously (LOX first to prevent hardware rich condition).
Well, as long as you don't know exactly what was the fault in the valve and don't have a better design to replace it there is little sense in changing all of them, isn't there? After all, the ones in the engines right now are tested and why would a new one be any better as long as it's the same design/production run?If you can identify a systematic issue you can mitigate it makes sense to change all valves, and given the fact that it seems to be something you can do in a day I would guess SpaceX would do that, they don' want to lose missions or launch opportunities, too, but if you can't, there's no sense in changing something that has worked so far for something you don't know whether it's better or not.
Did some moving around. Remember, this is general discussion, the other is for updates.Noticed someone posted "been reported it's a check valve" an hour after it was in the update thread, with both threads cross posting.Remember the difference between the two threads.
If it is the central engine overheating then it sounds like kind of an expected thing - the solution would be to get rid of a central engine altogether and make an eight engine design; but would'n be possible to just make a good use of heat transferred to it by surrounding engines - like decreasing internal pressure would still produce required thrust due to higher temperature?
By analogy, Formula One cars used to go through a major strip-down between qualifying and the race, due to the short lifetime of the components. When they started locking the cars down post-qualifying as a cost-saving measure, the teams were surprised to find that reliability went up - the strip-down introduced more problems than it avoided.cheers, Martin
1) Is it likely the mixture-adjustment hardware could compensate for a LOX-rich bias in an engine, at least to carry it through the first seconds of flight until the point where the Falcon can struggle on with eight engines? I'm guessing not, as I assume the actual adjustment range would be quite small.2) Also, how does the stage determine the remaining prop levels - does it just integrate the flow levels? If so, would the flow be measured per-engine or before the octopus? If flow is measured per-engine, I guess that would be a useful indication to the engine controller of a problem.
I read that Elon made the same call I was going to make before he knew it was a mechanical failure with a ck vlv. When the call was made that Merlin #5 Chamber Press High was the reason for the Hot Fire Abort he said they could simply "adjust" the software limits in the LCC that monitors Merlin #5 Chamber Press. They could bump up the margin on the high side of its tolerance to allow launch. I'm sure they would agree to do so only if they could prove it was a transient condition and they had backup data to rely on. That was what we might do (Shuttle) if we could prove it was purely a transient transducer reading, it was fully understood and we had backups and it wasn't a "1 of 1" LCC reading. Still it's a big time call Elon would ultimately have to make. My discussion here is of course a mute point now. Still, I throw it into discussion for future reference to all my brother rocket junkies here @nsf.com. One never knows what is forthcoming on their next and future attempt(s)!
Quote from: MP99 on 05/20/2012 10:25 am...2) Also, how does the stage determine the remaining prop levels...?...2) Tank bottom pressure. Flight computer solves for h in P_b = P_ull + rho*g*h. There are patents on it that are available with a web search.
...2) Also, how does the stage determine the remaining prop levels...?
Quote from: MP99 on 05/20/2012 10:25 am1) Is it likely the mixture-adjustment hardware could compensate for a LOX-rich bias in an engine, at least to carry it through the first seconds of flight until the point where the Falcon can struggle on with eight engines? I'm guessing not, as I assume the actual adjustment range would be quite small.2) Also, how does the stage determine the remaining prop levels - does it just integrate the flow levels? If so, would the flow be measured per-engine or before the octopus? If flow is measured per-engine, I guess that would be a useful indication to the engine controller of a problem.1) Hard to say. If there's closed-loop engine control, maybe. Too many branches of the fault tree to say for sure. Not sure it's even desirable to try and fly through it. Abort may be the better choice.2) Tank bottom pressure. Flight computer solves for h in P_b = P_ull + rho*g*h. There are patents on it that are available with a web search.
That's very clever, and after-the-fact seems so obvious. Couldn't this also be used for calculating how full the propellant tanks are on the pad, in order to load an ideal amount of propellant for a certain trajectory?
Quote from: Robotbeat on 05/20/2012 05:39 pmThat's very clever, and after-the-fact seems so obvious. Couldn't this also be used for calculating how full the propellant tanks are on the pad, in order to load an ideal amount of propellant for a certain trajectory?Yes, but liquid level sensors at the top of the tank are more accurate.
