The point would be to close clamshell again after separation to have the same aerodynamic shape reenter that went up. And then do trailing ballute, streamer or parachute or whatnot to survive the splash
Quote from: savuporo on 04/09/2016 07:30 pmThe point would be to close clamshell again after separation to have the same aerodynamic shape reenter that went up. And then do trailing ballute, streamer or parachute or whatnot to survive the splashThe shape that went up is not optimal for reentry.It probably has a stable attitude, but the two half fairing have half mass/surface, therefore more chances to survive reentry (if stabilized).
Is it out of the question to have the fairing separation event coincide with MECO and let the fairings attach to the first stage? From my understanding, MECO now happens at around 80 km (correct me if I'm wrong) which is not that far from space.Doesn't the desire to eventually reuse the entire rocket suggest that the first stage needs to stage later in order to give more margin to the second stage?
The cost of jettison isn't cheap here. Remember, you could lose a mission in saving a buck.
Quote from: Radical_Ignorant on 04/09/2016 04:31 pmQuote from: Jim on 04/09/2016 01:49 pmQuote from: Radical_Ignorant on 04/09/2016 10:54 amAnd how to keep them connected? Well, I see on the video were they test separation mechanism that both parts are connected, so it seems possible. And in old days there were those rockets controlled by cables, so there are things which can survive and do the job.not true on either point. The cables would put loads on the fairings and there is no way to bring them together in a controlled matter without them slamming together.Which rockets were controlled by cables?Of course that they would put loads, and so? This load would be symetric, fairings would be tiny bit heavier.No way to bring them together? You mean that it's impossible to control force required to pull the cable? Or you say that using force in only one way it's not possible to gently stop momentum? Like for example on rocket falling from the sky? Or you claim that TOWs (thanks tyrred - I was lazy) weren't working because there is no cable which could easily withstand rocket exhaust? It's always super easy to claim "no it's impossible". But that's rarely true. That would be too hard, or that would not be cost effective, or that could be dangerous/not reliable because of... that I could believe.How about "it's simply unnecessary."
Quote from: Jim on 04/09/2016 01:49 pmQuote from: Radical_Ignorant on 04/09/2016 10:54 amAnd how to keep them connected? Well, I see on the video were they test separation mechanism that both parts are connected, so it seems possible. And in old days there were those rockets controlled by cables, so there are things which can survive and do the job.not true on either point. The cables would put loads on the fairings and there is no way to bring them together in a controlled matter without them slamming together.Which rockets were controlled by cables?Of course that they would put loads, and so? This load would be symetric, fairings would be tiny bit heavier.No way to bring them together? You mean that it's impossible to control force required to pull the cable? Or you say that using force in only one way it's not possible to gently stop momentum? Like for example on rocket falling from the sky? Or you claim that TOWs (thanks tyrred - I was lazy) weren't working because there is no cable which could easily withstand rocket exhaust? It's always super easy to claim "no it's impossible". But that's rarely true. That would be too hard, or that would not be cost effective, or that could be dangerous/not reliable because of... that I could believe.
Quote from: Radical_Ignorant on 04/09/2016 10:54 amAnd how to keep them connected? Well, I see on the video were they test separation mechanism that both parts are connected, so it seems possible. And in old days there were those rockets controlled by cables, so there are things which can survive and do the job.not true on either point. The cables would put loads on the fairings and there is no way to bring them together in a controlled matter without them slamming together.Which rockets were controlled by cables?
And how to keep them connected? Well, I see on the video were they test separation mechanism that both parts are connected, so it seems possible. And in old days there were those rockets controlled by cables, so there are things which can survive and do the job.
{....}I'll try offer my criticism, and not just dismissal. Although I would add that "dismissal", when it comes from many veteran sources pretty clued into real world experience with space hardware, is a good hint that an idea may not be great. {....}
So back to the topic of cables....I don't think the cables seen in the SpaceX fairing test video from the Plum Brook facility indicate in any way that cables would work like this in a freefall/zero-g environment. It's nice to imagine in our gravitationally conditioned minds {....}
It's too easy to think of this problem like a household vacuum cord automatically winding itself back inside the appliance housing, but it just won't work like that. Each pull of the cord/cable on attached fairing halves will accelerate the halves in the direction of the pull. Unless the vector of that acceleration exactly moves the halves to a rendezvous, they will impact obliquely, & spin apart from each other from an in-elastic collision, and not rendezvous. Furthermore, once they are accelerating towards each other, cables cant slow them down. Ever try making compression forces with a string? That means RCS and sensors, and you may as well eliminate the cables entirely. I see a a big tangled mass of cable and fairing resulting after a few collisions together.
So at the moment they are looking to recover one half if I am right. But lets say in future after all experience gained they are recovering both halves, if recovery of one half goes wonky would that make other piece useless? Or these halves are designed to be swap-able?
It's always super easy to claim "no it's impossible". But that's rarely true. That would be too hard, or that would not be cost effective, or that could be dangerous/not reliable because of... that I could believe.
2) "Each pull will..." Sure it will. So you have 8 points to attach force. Quite a control system. It's not complicated to simulate it in software. Of course much harder to make it working in this simulation. But I believe it's software problem how to bring them back together gently.3) "Can't slow them down." That's why you do it gently. Like shuttle landing. Once it was over airfield you could not move it up and try again. I don't see it as no go.
Or you claim that TOWs (thanks tyrred - I was lazy) weren't working because there is no cable which could easily withstand rocket exhaust?
Quote from: sevenperforce on 03/25/2016 03:19 pmYou know, if it would be possible to hinge the damn thing, why not simply hinge it along one long edge? Then it could open along that edge and tumble away still connected.If you push a long edge hinged fairing over the other long edge, you get an inward movement of the hinge.You can add a reaction beam to keep the hinge clear from the payload, but this would increase the mass of the fairing.
You know, if it would be possible to hinge the damn thing, why not simply hinge it along one long edge? Then it could open along that edge and tumble away still connected.
Quote from: llanitedave on 04/09/2016 04:53 pmQuote from: Radical_Ignorant on 04/09/2016 04:31 pmQuote from: Jim on 04/09/2016 01:49 pmQuote from: Radical_Ignorant on 04/09/2016 10:54 amAnd how to keep them connected? Well, I see on the video were they test separation mechanism that both parts are connected, so it seems possible. And in old days there were those rockets controlled by cables, so there are things which can survive and do the job.not true on either point. The cables would put loads on the fairings and there is no way to bring them together in a controlled matter without them slamming together.Which rockets were controlled by cables?Of course that they would put loads, and so? This load would be symetric, fairings would be tiny bit heavier.No way to bring them together? You mean that it's impossible to control force required to pull the cable? Or you say that using force in only one way it's not possible to gently stop momentum? Like for example on rocket falling from the sky? Or you claim that TOWs (thanks tyrred - I was lazy) weren't working because there is no cable which could easily withstand rocket exhaust? It's always super easy to claim "no it's impossible". But that's rarely true. That would be too hard, or that would not be cost effective, or that could be dangerous/not reliable because of... that I could believe.How about "it's simply unnecessary."Could you then please explain me what is necessary? I could believe that all is really required it's to reduce speed of impact with water. Pieces found are already quite large, so it would be believable. Can you then help me and explain what for are those tests with controlling them? What could it help?
Quote from: Radical_Ignorant on 04/10/2016 07:54 am2) "Each pull will..." Sure it will. So you have 8 points to attach force. Quite a control system. It's not complicated to simulate it in software. Of course much harder to make it working in this simulation. But I believe it's software problem how to bring them back together gently.3) "Can't slow them down." That's why you do it gently. Like shuttle landing. Once it was over airfield you could not move it up and try again. I don't see it as no go.No, it is not a software problem. Cables are inadequate in that they can not provide 6 DOF control, since the only other anchor is the other fairing.. They will not prevent the fairing from twisting or hitting each other. There still are aero loads at separation.