Spaceship Two accident

[B-rad]

NTSB says the tail "feathers" are used to add drag and slow the spacecraft during re-entry...
...Why would they deploy them if they were not on their way back down? and they were at a lower speed.
...they are supposed to deploy them at a higher speed and during re-entry.

Even tho they were unlocked, it was reported that the feather action was not commanded.

[ogc]

So - I don't get it, and I doubt anyone here would know - but it's worth a shot......

NTSB says the tail "feathers" are used to add drag and slow the spacecraft during re-entry. Test procedures had the crew unlock the feathers and the deploy them above Mach 1.5. The apparently deployed at Mach 1.0. Why would they deploy them if they were not on their way back down? and they were at a lower speed.

I first thought oh - they moved at Mach 1.0 and the machine broke up.........but they are supposed to deploy them at a higher speed and during re-entry. I also wonder why they would not unlock them closer to when they are coming back down rather than in the accent stage....

I imagine that it would have something to do with them being unlocked while the rocket is firing. From reading about spaceship one and previous test flights the feathering is not supposed to be done obviously till after the rocket burn. I dont know if im crazy but looking at the pictures posted in this thread one of them looks like the two feathering wings are seperating from the craft in unison.

[Crusty]

It does look like the tail feathers came off in unison. It also looks like SS2 is flying upside down and backwards. I'm wondering if the feathers failed from overload during the feather and the craft nosed down 180 degrees when they detached.

[AirFrame]

I first thought oh - they moved at Mach 1.0 and the machine broke up.........but they are supposed to deploy them at a higher speed and during re-entry. I also wonder why they would not unlock them closer to when they are coming back down rather than in the accent stage....

It's probably a number of factors at work... Yes, they were slower, but the engine was firing, which wouldn't be happening on re-entry, and they were going up, so moving from thicker air to thinner air, which may have increased the aerodynamic forces on the feathers.

[Driving Rain]

The feather configuration is not supposed to happen until dynamic forces reach zero or close to zero on the ascent, after rocket burn out. I would imagine that would be very close to 100,000 meters or the Karmin line.

[grimey]

http://www.parabolicarc.com/2014/11/03/ ... er-unlock/

That pilot went on to explain that there was a rule that anyone flying the spaceship could not re-configure the vehicle without the verbal acknowledgment of both pilot and co-pilot. It is unclear whether that protocol was followed. Normally, the co-pilot would announce when Mach 1.4 had been reached — the proper speed to unlock the feather. The pilot would acknowledge and command the co-pilot to unlock the feather. Once the feather was unlocked, the co-pilot would announce the maneuver had been completed.
A number of sources, who spoke on the condition of anonymity because the company has forbidden interviews with the media, described seeing Alsbury unlock the feather and then appear to realize there was an error, moving quickly as if he was trying to shut off the motor, but it was too late.

Sounds like it was unintentional, and he knew immediately after he did it that it was a bad thing to do.

's probably a number of factors at work... Yes, they were slower, but the engine was firing, which wouldn't be happening on re-entry, and they were going up, so moving from thicker air to thinner air, which may have increased the aerodynamic forces on the feathers.

The pilot would have been trying to get the aircraft to pitch up at that point for the climb, right? And the elevators would be on the (now unlocked) booms, with the engine on the main fuselage, which likely would have put even more pressure on the pivot than just the engine alone. It'd be interesting to see how strong the mechanism to control the feathering is, I doubt they had the locks there just to make it a 2 step process to move the booms.

[goldeneagle]

So - I don't get it, and I doubt anyone here would know - but it's worth a shot......

NTSB says the tail "feathers" are used to add drag and slow the spacecraft during re-entry. Test procedures had the crew unlock the feathers and the deploy them above Mach 1.5. The apparently deployed at Mach 1.0. Why would they deploy them if they were not on their way back down? and they were at a lower speed.

I first thought oh - they moved at Mach 1.0 and the machine broke up.........but they are supposed to deploy them at a higher speed and during re-entry. I also wonder why they would not unlock them closer to when they are coming back down rather than in the accent stage....

The aerodynamic forces change dramatically thru transonic thru to pure supersonic flight. A lot depends on the shape, but shock waves will start to develop around mach 0.9 for a very blunt body, somewhat higher if it's somewhat sharper. SS2 was not exactly a sharp edged machine, so I would expect transonice range to start somewhere around 0.9, and continue thru to roughly mach 1.1. From 1.1 thru to somewhere just shy of 1.5 aerodynamic forces will make dramatic changes as the shock waves fully develop and move aft. A traditionally configured aircraft (wings, fuselage, tail feathers) will tend to pitch down during this process. If you remember a discussion here on AvCan from some time back regarding concorde, they way they dealt with this on that machine was to pump fuel, tons of it, between forward and aft trim tanks.

I have no direct knowledge of this particular aircraft, but based on reading, its been suggested the wing feather was to be unlocked at mach 1.4. To me, this implies that the locks were required to withstand aerodynamic loads during the transition from subsonic thru to pure supersonic flight, and by mach 1.4 the loads will have moved aft enough the extra strength of the locks was not required to keep the wings properly configured, below that number, it was. I'm also going to guess, that during that phase they vehicle was expected to climb significantly, so it would be in thinner air, further reducing loads.

I have no doubt that exact causes will come out during the investigation. They have telemetry, on board recorders, high speed footage from ground and chase planes as well as on board cameras, all the information to figure out exactly what happened, with little / no guesswork involved.

It's been more than a decade since I've worked in that area of the industry, so my only sources of information these days are the same as everybody else, what's written in the press.