Quote from: KelvinZero on 11/05/2013 08:43 amer.. I still dont know, because you asked a series of difficult quantitative questions rather than provide any informative quantitative answers. You speculated about turning the stage sideways *before* the last burn. That implies RCS only. I maintain there's no RCS capability in the stage that can orient it sideways when the CoG is so much more forward than the CoP. As simple as that.
er.. I still dont know, because you asked a series of difficult quantitative questions rather than provide any informative quantitative answers.
What's the estimation margin of error on the m/s?
Nice work hrissan but..Those cannot be the fit values. (Despite Excel being like baby talk for engineers, I use it all the time. One just has to be careful. In it one can use the LINEST array function to get the polynomial terms for the fit. We could also look into the sensitivity of the results to the choice of the minimum altitude time.)Look at the "last 3 seconds" graph. Take out the time bias by setting 82.4 seconds to t'=0. The graph extends 82.4-79.6=2.80 seconds on both sides. The parabola is about 31 meters high. 2*31/2.8^2=7.91. The quadratic term should be 7.91, not 0.156. The units are meters per second squared, SI acceleration.To check, the distance under constant acceleration is 0.5*a*t^2=0.5*7.91*2.80^2=31 meters.At 7.91 m/s^2 this represents 0.81 g for a T/W ratio of 1.81:1. That's pretty close to 2, which is about the value that as been discussed here, IIRC.I would have hoped to see flights with higher terminal decelerations, but Grasshopper has been declared retired.You can do a better job with your original values. (Can we have your spreadsheet with the values?)Again, nice work deriving the values.
Thanks hrissan, the values of the ascent part copes well with the simulation I tried after the flight:http://forum.nasaspaceflight.com/index.php?topic=32718.msg1108494#msg1108494what's really interesting is the final deceleration, really high for GH1, due to the reduced max thrust of his engine and the high empty mass.No way to obtain it in my simulation unless using values of engine thrust greatly outside the 100-70% range.
Is it news, that the stage was intact until it hit the ocean?
An interesting comparison, but one note - the last flight was pretty close to the hexacopter, so the wide angle would make the flame look shorter than it is.
It seems there were never such an intensive thick and long flame as on the last flight. Either SpaceX decided to test Merlin prototype outside its nominal thrust levels or they swapped the engine to production Merlin 1D.
Flame length depends on thrust level, so if we don't know that for the specific frame in question, comparisons aren't very useful.