But! if the rocket can handle the thrust imbalance, which it should, then you can have three engines fail *anywhere* in the 27 cluster, and probably have even more engines fail if the distribution is favorable.
Of course, having 9 engines on the core would still work but you'd want to cut some off real early and in a sense you'd be throwing engines away after a minute or so of work.
I think that's the preferred approach. You're indeed using some of the engines for only a short period, but these are small 1/9 engines. It's not prohibitive, and it factors into the whole reliability issue.
Flying at an angle is a bitch of course, but unlike the Shuttle for example where the biggest thrusters are very far apart, the aspect ratio inside the single cluster and between the cluster is not that much different, so the flight angle will not be much different.
My guess is that they won't throttle the core down early - they'll kill more engines on the center core, and earlier.You want all three cores at full blast on liftoff, but since all cores are getting lighter and you're only killing center core engines, you can do it faster.
The core in a parallel-staged vehicle is supposed to burn longer so the energy at burnout would be significantly higher than on a single stick F9. Hence you would probably have to kiss any stage recovery goodbye.
You still can't arm wave it away and say the vehicle can take it.
Quote from: Jim on 02/22/2011 07:10 pmYou still can't arm wave it away and say the vehicle can take it. Go back to the list I posted above, you can easily ascertain the thrust imbalance and the torque arm in each of the scenarios - the angle is chiefly determined by that, since you still need the thrust vector to pass through the CG.k?
Didn't an N1 fail that way, just kept on shutting down engines to balance it until it could no longer lift itself over the lithosphere?
No, I'm saying the angle of attack is similar, and the vehicle is actually stronger in that plane. Otherwise, I'm presenting the best calcs I can make from existing data.I still have to hear a single argument why it will be worse - other than "nobody proved it to my satisfaction". We've got this dynamics going where I follow up on the data as best I can, and all you guys are saying is "you're arm waiving" - but you're not presenting anything to the contrary... Of course I can't absolutely prove stuff, since I don't have the SpaceX data... But you're not arguing to the contrary, you're just complaining...
But it makes more sense to stretch the core instead of the boosters.
That appears to make little sense... Unless they can throttle down the core significantly. (which they cannot do on the current Merlin 1c, AFAIK).
a. How is the vehicle "stronger" in that plane?b. The fairing is not strongerIt is worse because the vehicle is flying at an angle of attack it is not designed for. The vehicle is using the same cores as the existing F9.And you have yet to address the propellant utilization.
Get a load of what they appear to be contemplating, from Tim Hughes' AIAA presentation:The image in the PDF is called 'Falcon 9 Heavy extended'. Stretched tanks don't exactly strike me as being just 2 more first stages strapped to the side.
Quote from: ugordan on 02/22/2011 06:02 pmGet a load of what they appear to be contemplating, from Tim Hughes' AIAA presentation:The image in the PDF is called 'Falcon 9 Heavy extended'. Stretched tanks don't exactly strike me as being just 2 more first stages strapped to the side.Where did you get the term "extended"? I don't see it on the presentation. Is there a chance that this image might merely be a mistake? - Ed Kyle