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Wow, that is shocking.
I guess there has to be some reason, but for now I cannot think of any good reason to ever unlock the feather system until the ship was a lot higher than that. And I am not talking about the "early" unlock at Mach 1, I mean the intended unlock at 1.4. Mach 1.4 as the point of unlock makes no sense at all by itself, because that does not take into account the altitude and therefore the aerodynamic pressure. I mean, if it did not climb to a higher altitude then the aerodynamic forces at Mach 1.4 would be nearly double (1.96 times) the aerodynamic forces at Mach 1. Now, since it is climbing, then on a normal flight profile it would be higher up at Mach 1.4 than lower down at Mach 1, so the air would be thinner. But still…..why even unlock it at all until the air was very thin, after burnout?
This would make as much sense of "arming" the deployment of the landing gear on a space shuttle during the climb into orbit.
Of course, there is a difference between unlocking, and then activating it to deploy. So the feathering wasn't supposed to happen till much later and the pilots did not activate it. But again why unlock it before burnout?
Incredibly ironic, too. The fatal X-15 crash, where the pilot got disoriented (cockpit attitude readouts had been changed from previous missions, contributing to the confusion) and re-entered at the wrong angle of attack, leading to the X-15 breaking up. Rutan came up with the feather system for re-entry as a "fail safe" way to re-enter. So now the fail-safe feather re-entry system goes alongside the "unsinkable" Titanic.
I would not be surprised if there is no computer code to check for safe flight regime conditions before allowing the feather to activate. Goes to the fact that these things are hand-flown by the pilots, rather than using a guidance system to control the ascent. Space Ship One, on perhaps its first flight into space, went out of control in the roll axis for awhile, near the end of the burn. IIRC it kept rolling for quite a while after burnout. I wondered how the guidance system could screw up that bad until I found out it was manually flown by hand. But, it survived, so apparently they didn't give the new ship any automated system either.
In seeing some onboard video this weekend, of a SS2 test flight, looking aft, you can see the wings rocking back and forth and back and forth a few degrees, which would seem consistent with a pilot needing to make small roll corrections moment by moment. A guidance system would hold the wings level, or at least the corrections would have been a lot smoother (unless perhaps they do have a roll damper system but had not gotten it dialed-in by that flight, or the hybrid burn is THAT rough that even an automatic system has trouble).
So, given that mindset for total pilot control of the vehicle, I do not think the feather system would be relying on a computer to give it permission to be activated only once the computer programming agreed the ship was in thin enough air and/or enough time had elapsed since ignition. It would seem it's pretty much the computer responding directly to the command given by the unlock lever, and then responding to the feather lever. This assumes of course there even is a computer in the loop for that, there might not even be a computer beyond the use of a microcontroller to ensure that both tailbooms are being raised and lowered at the exact same angles, so they are parallel to each other at all times. Same for the control surfaces on the flight controls, they would be computer driven in the sense of electro-mechanical activators moving them, but perhaps more analogous to an R/C plane where the computer is the receiver, and the transmitter is the manual controls for the pilots in the cockpit.
BTW - I could see a few reasons to be concerned about letting a computer decide on whether it was safe to deploy the feather. That would be in case of an emergency where the computer might not allow the feather to activate, when the pilots would rather risk the feather in an out of parameter situation than not being able to deploy it at all. Or the computer getting confused by data outside of its programming. Also fears of the computer screwing up, hanging up on a line of code or something. But that could be addressed by an emergency override toggle switch, with a safety cover over it, so it could never be activated by accident, only on purpose.
Of course, there is the mystery of why the feather activated anyway since the activate lever was not moved. So that could have been a computer problem if the computer was in the loop (or a short in the wiring to the feather activation lever, if it is electromechanical and not some sort of hydraulic activation). Or it could have been something as basic as why the tailbooms were intended to be LOCKED to begin with, so that aerodynamic forces could not cause the actuator systems to be overwhelmed and pitch the wing and fuselage up. In other words, once unlocked, aerodynamic loads could have taken over and forced it to pivot up to feather, then breakup soon after.
So, if this accident is due to the Feather system activating early, that is the sort of thing that can be fixed pretty quickly. But even so, they have two massive issues. For one, the fallout from the accident in so many ways, the most basic one being how many customers would still be willing to go, never mind the regulatory attention they are deservedly going to get before they are ever allowed to carry passengers.
The other is basic rocket science. Even with the new nylon propellant in place of HTPB rubber, from what I read up on over the weekend, it seems that the engine does not have the Newton-seconds to get it high enough to reach space. Of course how high up "space" is, is an arbitrary altitude that was determined by a committee, choosing 100 km , or 62 miles (For the US Air Force, it was 50 miles). So they may need yet another engine to do it, but having squeezed about all they can out of hybrid technology that can fit inside the existing airframe design, they might have to go with a liquid engine to get the performance.
Having seen and read more this weekend, the photos of the bright flame and dense smoke early, then the "wimpy" flame and less smoke seems to have this explanation. For the ignition process of the hybrid, methane and perhaps another gas I do not recall was mixed in, to help get it going. That could explain the bright flame and dense smoke early, the methane and perhaps another gas being burned in the ignition process, then by the time of the other photo it was burning normal, with less flame and less smoke. Also looked very different from the other powered flights since the HTPB rubber fuel produced a lot more flame and a dark smoke.
BTW - a correction to an earlier matter, the pilot that survived didn't climb out of the fuselage, there was no fuselage to climb out of. It seems most of the fuselage disintegrated, including the cockpit, so both pilots were thrown out. The one who didn't make it , still in his seat, was too badly injured to survive. Their personal chutes opened automatically at about 10,000 feet or so.
- George Gassaway
I guess there has to be some reason, but for now I cannot think of any good reason to ever unlock the feather system until the ship was a lot higher than that. And I am not talking about the "early" unlock at Mach 1, I mean the intended unlock at 1.4. Mach 1.4 as the point of unlock makes no sense at all by itself, because that does not take into account the altitude and therefore the aerodynamic pressure. I mean, if it did not climb to a higher altitude then the aerodynamic forces at Mach 1.4 would be nearly double (1.96 times) the aerodynamic forces at Mach 1. Now, since it is climbing, then on a normal flight profile it would be higher up at Mach 1.4 than lower down at Mach 1, so the air would be thinner. But still…..why even unlock it at all until the air was very thin, after burnout?
This would make as much sense of "arming" the deployment of the landing gear on a space shuttle during the climb into orbit.
Of course, there is a difference between unlocking, and then activating it to deploy. So the feathering wasn't supposed to happen till much later and the pilots did not activate it. But again why unlock it before burnout?
Incredibly ironic, too. The fatal X-15 crash, where the pilot got disoriented (cockpit attitude readouts had been changed from previous missions, contributing to the confusion) and re-entered at the wrong angle of attack, leading to the X-15 breaking up. Rutan came up with the feather system for re-entry as a "fail safe" way to re-enter. So now the fail-safe feather re-entry system goes alongside the "unsinkable" Titanic.
I would not be surprised if there is no computer code to check for safe flight regime conditions before allowing the feather to activate. Goes to the fact that these things are hand-flown by the pilots, rather than using a guidance system to control the ascent. Space Ship One, on perhaps its first flight into space, went out of control in the roll axis for awhile, near the end of the burn. IIRC it kept rolling for quite a while after burnout. I wondered how the guidance system could screw up that bad until I found out it was manually flown by hand. But, it survived, so apparently they didn't give the new ship any automated system either.
In seeing some onboard video this weekend, of a SS2 test flight, looking aft, you can see the wings rocking back and forth and back and forth a few degrees, which would seem consistent with a pilot needing to make small roll corrections moment by moment. A guidance system would hold the wings level, or at least the corrections would have been a lot smoother (unless perhaps they do have a roll damper system but had not gotten it dialed-in by that flight, or the hybrid burn is THAT rough that even an automatic system has trouble).
So, given that mindset for total pilot control of the vehicle, I do not think the feather system would be relying on a computer to give it permission to be activated only once the computer programming agreed the ship was in thin enough air and/or enough time had elapsed since ignition. It would seem it's pretty much the computer responding directly to the command given by the unlock lever, and then responding to the feather lever. This assumes of course there even is a computer in the loop for that, there might not even be a computer beyond the use of a microcontroller to ensure that both tailbooms are being raised and lowered at the exact same angles, so they are parallel to each other at all times. Same for the control surfaces on the flight controls, they would be computer driven in the sense of electro-mechanical activators moving them, but perhaps more analogous to an R/C plane where the computer is the receiver, and the transmitter is the manual controls for the pilots in the cockpit.
BTW - I could see a few reasons to be concerned about letting a computer decide on whether it was safe to deploy the feather. That would be in case of an emergency where the computer might not allow the feather to activate, when the pilots would rather risk the feather in an out of parameter situation than not being able to deploy it at all. Or the computer getting confused by data outside of its programming. Also fears of the computer screwing up, hanging up on a line of code or something. But that could be addressed by an emergency override toggle switch, with a safety cover over it, so it could never be activated by accident, only on purpose.
Of course, there is the mystery of why the feather activated anyway since the activate lever was not moved. So that could have been a computer problem if the computer was in the loop (or a short in the wiring to the feather activation lever, if it is electromechanical and not some sort of hydraulic activation). Or it could have been something as basic as why the tailbooms were intended to be LOCKED to begin with, so that aerodynamic forces could not cause the actuator systems to be overwhelmed and pitch the wing and fuselage up. In other words, once unlocked, aerodynamic loads could have taken over and forced it to pivot up to feather, then breakup soon after.
So, if this accident is due to the Feather system activating early, that is the sort of thing that can be fixed pretty quickly. But even so, they have two massive issues. For one, the fallout from the accident in so many ways, the most basic one being how many customers would still be willing to go, never mind the regulatory attention they are deservedly going to get before they are ever allowed to carry passengers.
The other is basic rocket science. Even with the new nylon propellant in place of HTPB rubber, from what I read up on over the weekend, it seems that the engine does not have the Newton-seconds to get it high enough to reach space. Of course how high up "space" is, is an arbitrary altitude that was determined by a committee, choosing 100 km , or 62 miles (For the US Air Force, it was 50 miles). So they may need yet another engine to do it, but having squeezed about all they can out of hybrid technology that can fit inside the existing airframe design, they might have to go with a liquid engine to get the performance.
Having seen and read more this weekend, the photos of the bright flame and dense smoke early, then the "wimpy" flame and less smoke seems to have this explanation. For the ignition process of the hybrid, methane and perhaps another gas I do not recall was mixed in, to help get it going. That could explain the bright flame and dense smoke early, the methane and perhaps another gas being burned in the ignition process, then by the time of the other photo it was burning normal, with less flame and less smoke. Also looked very different from the other powered flights since the HTPB rubber fuel produced a lot more flame and a dark smoke.
BTW - a correction to an earlier matter, the pilot that survived didn't climb out of the fuselage, there was no fuselage to climb out of. It seems most of the fuselage disintegrated, including the cockpit, so both pilots were thrown out. The one who didn't make it , still in his seat, was too badly injured to survive. Their personal chutes opened automatically at about 10,000 feet or so.
- George Gassaway
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