That’s not a statement, but clearly is a legitimate question. If so, he paid with his life.
Also if so, it’s a pretty easy thing to fix. But it still doesn’t explain why they deployed without the command to do so. And we still don’t really know how well the engine performed, or what kind of vibration environment it will provide the vehicle and passengers. At least publicly.
[Update a few minutes later]
It strikes me as ironic, and a demonstration of one of the major points of my book, that the two main features of the vehicle implemented in the name of safety (hybrid motor, and feathering wings) may have actually made the vehicle more dangerous and less operable. Lynx will be a much simpler system.
Pilot error may be a contributing factor. What Mach number were his instruments indicating? Looking at video from a previous powered flight, they didn’t appear to be following the protocol described in that article. Even if he did make a mistake and unlock the feathering mechanism at too low an airspeed, that should not have caused the mechanism to activate. Unless the pilot was pushing down on the controls just at that moment (possible but unlikely), the stabilators should have been impacting a down force. One possibility is that there was a malfunction in the feathering mechanism that caused it to begin without being commanded. This would’ve caused a strong pitch up which, when combined with the thrust vector, would’ve been very severe, strong enough to tear the plane apart. Some reports indicate the plane may have even flipped 180 degrees. Doing that at Mach 1 under full power is not recommended.
Aviation accidents are seldom caused by a single malfunction or mistake. More often, a chain of events happens to cause the accident. As a hypothetical, in this case the copilot may have seen an erroneous indication that he was at Mach 1.4. Or, he may have made a mistake under the high G loads and vibrations.. He unlocks the feathering mechanism. A malfunction causes the system to feather while at full power, leading to high stresses that cause airframe destruction.
As for safety equipment sometimes killing people, it happens. Most of the time, seatbelts save lives but once in a while, a person gets trapped in a burning or sinking car and dies. Airbags can save lives but have also killed some people (even before the latest set of them exploding and sending fragments out like a grenade). Cockpit automation makes airline flight much safer but has also contributed to accidents. There is no such thing as a completely fool proof system. Lynx, while an interesting design that I hope succeeds in every way, will also have its failure modes that could result in the loss of the vehicle.
If it is true that they were near Mach 1 at the time when the mechanism was unlocked, the answer could be transonic shock wave effects. I thnk it possible that forces on the tails could have been high enough to overcome or even break the feathering mechanism. Just to be clear, I have no insight into the actual forces on this design through the transonic regime or of the feathering mechanism design, but just put that out as a possibility.
Good article from Popular Science on the NTSB investigation. It does contain one minor error:
SpaceShipOne was a brutal ride for the test pilots, with a re-entry that was a brain-scrambling ordeal on both of its suborbital flights. (In 13 years since the SpaceShipOne program began in 2001, the effort has only successfully gone to space twice.)
SpaceShipOne flew into space three times, not two. The first time was flight 15P on June 21, 2004 with Mike Melville at the controls. He climbed to just over 100 KM. Mike was again at the controls for flight 16P on September 29, 2004 for the first of the two flights required to win the X-Prize. He reached an altitude of just under 103 KM. Brian Bennie flew flight 17P on October 4, 2004 to 112 KM to win the X-Prize.
All other things being equal, if that vehicle had come apart at altitude with an all liquid engine there is an extremely high probability that the pilot would not have survived.
Score one for the hybrid.
Given the violence of the breakup, it seems possible the the pilot didn’t bail out but instead was thrown clear. If that happened, it would be similar to what happened to a Blackbird pilot back in the 1960s whose plane came apart at Mach 3+ (how rude and uncalled for!).
It also has this:
“A rubber-based fuel had served SS1 well, but engineers recently switched to a plastic-based fuel to produce greater thrust for the larger SS2.”
He went on to infer that this was the reason they had gone no higher than 71,000 feet in 54 test flights to date.
Otherwise a pretty informative piece and I agree with him that there will be a great focus on the lack of redundancy in the Locking mechanism, especially if the failure was a predictable result of unlocking it prematurely!
Why the Hell would you unlock that feature while the motor was still thrusting?
The most logical answer I’ve read is that you want to ensure the feathering mechanism is going to unlock before you actually need it. If it failed to unlock, they could terminate the burn and recover the aircraft. If they waited until after the burn was over, they’d be going so high and fast that they’d likely lose the aircraft if the feather failed. Without feathering, I don’t know if the attitude control thrusters would have enough power to keep the plane in a high-drag attitude. Without that, it would pick up too much speed on reentry and likely come apart at some point.
That makes sense, but I believe I would prefer an “as fool proof as possible” unlock mechanism (emergency explosive bolts as insurance? ) and rely on that rather than unlocking under thrust.
It strikes me as ironic, and a demonstration of one of the major points of my book, that the two main features of the vehicle implemented in the name of safety (hybrid motor, and feathering wings) may have actually made the vehicle more dangerous and less operable. Lynx will be a much simpler system.
Yeah. A lot of people often forget that the more systems you add the higher the chance is that something will fail. If those added systems are in critical paths then you are actually decreasing safety rather than increasing it. Still when I first heard about it I thought that the feathering system was a neat idea. Maybe it is not practical in an everyday business case but it is still a neat idea.
As for the hybrid engine it seems to me like a waste of time on a reusable. It is not as easy to refuel or throttle the engine and the ride is less smooth, which is a problem when carrying passengers as is the case. A simple case of bad design where they went for the novelty factor regardless if the choice made sense or not. Or maybe they thought the engine R&D would be cheaper. It is not. Not really. Not once you take all the fiddling into unknown variables into account versus well established liquid rocket technology. Perhaps Burt should have taken a leaf out of his playbook with his regular airplanes where he seldom uses engines which aren’t common as dirt.
As for the Lynx I reserve judgement until I see it but XCOR does not strike me as having enough airframe design background. Unlike you guys I do not think the airframe is the “easy” part. It might be for someone like Scaled and even they would have issues with going into high Mach flight in the atmosphere. The software tools for that suck last time I heard. Something about not having enough real world data to validate the models.
To me the airframe of a winged spacecraft has the same order of complexity as designing the engine if not more. This is one reason why I am against winged spacecraft designs to begin with. It just makes a difficult problem harder to solve for few good reasons.
XCOR is great at liquid rocket engine design. Scaled was great at airframe design but it seems they made this particular design too hard to operate safely.
As for the Lynx I reserve judgement until I see it but XCOR does not strike me as having enough airframe design background.
They have had extensive expert consulting in that regard.
The software tools for that suck last time I heard. Something about not having enough real world data to validate the models.
They’ve done extensive supersonic wind-tunnel testing.
A lot of people often forget that the more systems you add the higher the chance is that something will fail. If those added systems are in critical paths then you are actually decreasing safety rather than increasing it.
If that is the case in any system, then it’s a major design error. Properly designed redundancy in flight critical systems has two effects: one, it decreases the probability of loss of control (PLOC), by orders of magnitude typically; and two, it increases the chance that you will have to abort a mission because of a failure, i.e., it decreases the mission reliability. It’s easy to see why: more things to fail, as you said, so you abort the mission when, say, one of three redundant air data computers fail, and the chance of that failure is 3x the single redundant vehicle (lower mission reliability), but the effect of the one ADC failure on safety is very small, whereas loss of a single string ADC would typically be loss of control and then loss of vehicle.
I don’t know what kind of redundancy Scaled designed into the feathering mechanism. It would seem to me that the tricky thing is that it (a) has to deploy to re-enter safely, but then (b) has to retract to regain active control and land safely. So it gets harder to make it fail-safe. E.g., for landing gear, you often have an emergency deploy system that will drive the gear down, but typically you can’t then raise the gear again without a major service. I assume that Scaled thought through all of these implications and did a proper PLOC / PLOA analysis, but I have no firsthand knowledge of that. I’m sure the NTSB is asking for that analysis right now…
– The safety advantage of a hybrid rocket is premised on the fuel and oxidizer not being able to mix freely like a liquid in severe failure, nor burn along a fuel grain fracture like a solid. Much of this advantage is lost if either propellant is prone to temper tantrums without mixing.
– I understand that transonic flow is rather messy. With the feathering mechanism unlocked, could aerodynamic forces in that range have overpowered the actuator?
A bit late for this thread, but the Daily Mail has an article about the cockpit footage.
It seems the pilot realized his feathering error and immediately tried to shut the engine down. To me that seems like a design problem where perhaps the decision to feather can’t be immediately undone, on top of not prohibiting a catastrophic mistake (such as accidentally lowering landing gear at Mach 2).