Quote from: AncientU on 04/08/2017 09:01 pmThis line of reasoning is flawed; you are assuming that EM didn't decide to bring back the second stage until that event 1-2 weeks ago. Us not knowing about his plan (and it is likely much more mature than he is letting on) doesn't have any bearing on him having a plan. His time constraints as you've outlined them don't exist... FH has been on drawing boards without a paying customer for years. IIRC, five years ago, he asked -- if you could launch anything into space, what would it be -- he was referring to the FH demo launch. The 'silly' payload and the hardware to return the second stage was probably ready last year when AMOS disrupted all plans.I agree with all that.It's not like Musk was telling us each week "This week we continued to do no work on upper stage recovery" until last week.All we had was one data point that said that at a particular time some time ago their current thinking was that they were de-emphasizing upper-stage reusability.
This line of reasoning is flawed; you are assuming that EM didn't decide to bring back the second stage until that event 1-2 weeks ago. Us not knowing about his plan (and it is likely much more mature than he is letting on) doesn't have any bearing on him having a plan. His time constraints as you've outlined them don't exist... FH has been on drawing boards without a paying customer for years. IIRC, five years ago, he asked -- if you could launch anything into space, what would it be -- he was referring to the FH demo launch. The 'silly' payload and the hardware to return the second stage was probably ready last year when AMOS disrupted all plans.
We really don't know whether that meant nobody working on it or a significant team working on it but considering it risky so not the most likely plan. And we don't know if a week after they spoke they changed their minds and decided to go full speed ahead on upper stage reusability again.
They also might have purposely been sandbagging to avoid bad publicity. Imaging they never really stopped working on upper stage reusability at all, but they wanted the press off their back, and no stories about how they had promised upper stage reusability but failed to deliver.
They might just say they weren't planning for it, which is technically correct because they have a plan to succeed even without upper stage reusability, but, really, it was mainly just to lower expectations.
That's the thing about science. New discoveries invalidate old theories. Looking over those old proposals for stage recovery aerospace companies pitched to the USG in the 60's and 70's none of them show control surfaces on the top end of the stage. In fact SX didn't show them either in their 2011 video. Yet that's what it takes to have adequate authority to get the job done. It took actual flight tests of a high aspect ratio structure to find that out. It's quite conceivable that it was not the only new science that SX have discovered. The trouble is science (except in funding proposals) does not operate on a timetable.
It isn't science, it is engineering.
Quote from: Jim on 04/10/2017 01:36 pmIt isn't science, it is engineering.Maybe a bit of both.
Back to the heat shield for a moment... How about just having the heat shield come up to the end of the thrust chamber and jettisoning the nozzle extension. 2nd stage would return engine first.CG (I assume) would much closer to the heat shield than it would be if it were on the nose of the 2nd stage. Aerodynamic center of pressure (I assume) would be way behind the CG. Jettisoning the huge bell would hopefully reduce the likelihood of it's area causing the 2nd stage to swap ends at hypersonic speeds.Curious what you guys think.
And then there is the hole left in the heatshield... little GNC door style hatch, maybe?
Quote from: ChrisWilson68 on 04/10/2017 10:58 amQuote from: AncientU on 04/08/2017 09:01 pmThis line of reasoning is flawed; you are assuming that EM didn't decide to bring back the second stage until that event 1-2 weeks ago. Us not knowing about his plan (and it is likely much more mature than he is letting on) doesn't have any bearing on him having a plan. His time constraints as you've outlined them don't exist... FH has been on drawing boards without a paying customer for years. IIRC, five years ago, he asked -- if you could launch anything into space, what would it be -- he was referring to the FH demo launch. The 'silly' payload and the hardware to return the second stage was probably ready last year when AMOS disrupted all plans.I agree with all that.It's not like Musk was telling us each week "This week we continued to do no work on upper stage recovery" until last week.All we had was one data point that said that at a particular time some time ago their current thinking was that they were de-emphasizing upper-stage reusability. "de-emphasizing upper-stage reusability " is PR speak.
SpaceX has done their fair share of innovation, but not much of what you might call science.
There might be things you could fairly characterize as science in combustion modeling or metallurgy, but that's a very small part of what SpaceX does.
What SpaceX does could be better characterized as R&D. I build astronomical instruments to do science. The distinction is that tons of research goes into how to implement various 'features' of the instrument -- each of these research projects is jokingly called a 'science project' -- but really they are engineering or technical evaluations, thus R&D. Once the instrument is built, tested, and integrated at an observatory, science begins.
Quote from: Robotbeat on 04/10/2017 01:44 pmSpaceX has done their fair share of innovation, but not much of what you might call science.That would be a fair statement if it was started "AFAIK"Quote from: RobotbeatThere might be things you could fairly characterize as science in combustion modeling or metallurgy, but that's a very small part of what SpaceX does.No company want to do science unless that's it's core function. It is not SpaceX's. Science is unpredictable and difficult to cost. It might work, it might not work or it might work too late to matter.