Virgin Galactic Announces Loss of SpaceShipTwo on Test Fligh

[HMS Sophia]

The Saturn IB used the SIVB stage, instead of the SIV stage.

Ah, but the IB used the 200 series while the V used the 500 series. They had minor, but important differences, such as the 200 series being unable to re-ignite for TLI. (The differences here are actually important. The 500 series was pressurised with helium to a higher level, and mounted several ullage motors to assist with re-ignition).
If we're niggling (Which I'll happily do) the equipment on the Saturn V had never flown before the first Saturn V flight. A single very similar stage had flown some 18 months earlier on a Saturn IB, but it was not identical to the SIVB-500 on the Saturn V.

[Starglider]

The Shuttle couldn't be tested like that, it could not be broken down into individual launchable systems. Its first manned flight was its first full test flight.

The shuttle could have been tested unmanned, with a little extra work on the control systems, in the same way that Buran was tested unmanned eight years later. NASA made a policy decision not to do that, presumably because they thought the possibility of human pilots being able to solve a problem and save the flight where an automatic system would have failed, was worth the risk.

[phongn]

The shuttle could have been tested unmanned, with a little extra work on the control systems, in the same way that Buran was tested unmanned eight years later. NASA made a policy decision not to do that, presumably because they thought the possibility of human pilots being able to solve a problem and save the flight where an automatic system would have failed, was worth the risk.

STS was deliberately designed so it could not be fully operated under autopilot (more or less at the demand of the Astronaut Corp) and it wasn't until after the breakup of Columbia that they hacked in an fix to deploy the landing gear via computer. Also, STS-1 was a crazy risky flight that exceeded its flight envelope and only continued because the crew didn't realize that.

[phongn]

"Learning how to do it better" does not necessarily mean "find another engine".

I have no confidence in VG's ability to stabilize a hybrid engine. This is the sort of task we usually throw at NASA or DOD rocket scientists for years and years with lots of money and armored test stands.

[phongn]

NTSB report via ObservingSpace's twitter feed

[HMS Sophia]

Soo... possible preliminary result is co-pilot error in unlocking the manual feather control early, leading to early feather extension, leading to aircraft exceeding flight parameters.
I think?

[Broomstick]

Preliminary results:

- it was not be the engine at fault (despite much hot air in this thread)
- the feathering mechanism deployed early, possibly due to the acting of aerodynamic forces on the control surface.

So it didn't blow up, it was torn apart by aerodynamic forces then the engine blew when the control system was either destroyed or no longer working.

Subject to change with more information, but it's an illustration of how first assumptions can be wrong.

[LadyTevar]

BBC News
Virgin Galactic crash: Pilots' actions analysed

Investigators probing the Virgin SpaceShipTwo accident have established a "human performance" team to help them understand the actions of the pilots.
The new group will look at how the men interacted with the vehicle, and the design and layout of the systems they used to control the craft.

SpaceShipTwo broke apart just seconds after igniting its rocket engine for a test outing above California on Friday. Pilot Peter Siebold parachuted clear; co-pilot Michael Alsbury was killed. Their ill-fated flight was to be part of a series of sorties that Sir Richard Branson's Virgin Galactic company hoped would finally lead to a commercial passenger service to sub-orbital space being introduced next year.

US National Transportation Safety Board acting chairman Christopher Hart told reporters in his final on-site briefing in Mojave that investigators were still waiting to interview Mr Siebold, who was seriously injured.

Mr Hart added a few more details to the information he put in the public domain on Sunday, when he revealed the vehicle's descent system was activated prematurely. This "feathering" technology, which is designed to slow and orientate the craft on its return to Earth, should not have been unlocked so early in the flight, and certainly should not have engaged at the time it did - on an accelerating ascent.

Mr Hart laid out a detailed timeline for SpaceShipTwo's last catastrophic moments.

'Uncommanded' deployment
The vehicle, he said, was dropped from its carrier aircraft, WhiteKnightTwo, at an altitude of almost 50,000ft at 10:07:19 US Pacific time.
The ship's hybrid rocket motor was then ignited just a couple of seconds later, at 10:07:21.
Eight seconds after that (10:07:29), the vehicle was travelling just under the speed of sound (Mach 0.94). Two further seconds into the flight (10:07:31), it was travelling at Mach 1.02.

It is in that period between Mach 0.94 and Mach 1.02 that Michael Alsbury is seen on recovered cockpit video moving a lever to unlock the feathering system - an action that in the pilots' checklist was not called for until the vehicle had reached Mach 1.4.

Investigators have previously described how the feathering system then deployed, apparently "uncommanded" by the pilots. It is probable that aerodynamic forces deployed the mechanism, resulting in the break-up of the ship. This is timed at 10:07:34 - the instant at which video and telemetry were lost.

One line of inquiry will be to ascertain whether the pilots were getting the correct information on their cockpit display throughout this critical period.

Data 'rich'
Mr Hart also revealed that small, lightweight pieces of wreckage have been found up to 30-35 miles (55km) northeast of the crash site in the Mojave desert. His investigators expect to finish their work at the site in the next few days. The largest item of wreckage, a piece of fuselage and wing, will be cut into smaller pieces to be transported away for further analysis.

Mr Hart said the NTSB's full report would take many months to produce. "It may be helped by the rich data sources that we have; we may be able to move a little more rapidly," he explained. "But we would anticipate taking as a much as 12 months to complete the analysis that would end up with a probable cause determination, as well as recommendations… in order not to have an incident like this again."

Pressing on
Virgin Galactic issued a statement in which it committed to full and open co-operation with the NTSB over the course of the investigation.

The company also stated its desire to continue with its space venture.
"While this has been a tragic setback, we are moving forward and will do so deliberately and with determination," the statement said.
"We are continuing to build the second SpaceShipTwo (serial number two), which is currently about 65% complete and we will continue to advance our mission over the coming weeks and months.
"With the guidance of the NTSB and the assurance of a safe path forward, we intend to move ahead with our testing program and have not lost sight of our mission to make space accessible for all."

So, the cockpit "black box" shows Asbury hit the feathering unlock too early. Now the question is did the computers make the pilots think they had hit the Mach 1.4 at that point, or did he jump the gun?

[Broomstick]

Just to clarify - SS2 did not have a traditional "black box". It did have an abundance of telemetry which actually resulted in MORE data than if they had used a black box.

Given the present data, I think the lever unlocking pilot jumped the gun, but he may not have known that aerodynamic forces could result in deployment without a human command involved. So he likely knew that he was unlocking it early, but not that doing so would result in disaster.

As always, present theory and subject to change with more information.

[Sky Captain]

I'm wondering why SS2 operating procedures calls for unlocking feathering mechanism so early while the engine is still running? Feathering maneuver is required during reentry so it would make sense to unlock safety mechanism when craft is at apogee or close to it. Main engine burn is when you would absolutely want the tail booms horizontal and locked in place to prevent exactly this sort of disaster.

[Broomstick]

It may have something to do with pilot workload. Sometimes a procedure is done in advance of absolutely necessary because at the necessary time there is so much else going on that cramming everything in at that point makes it more likely something might be overlooked/skipped/simply not done in time due to time constraints. This is especially common during landing procedures, which are generally the part of flight with the highest workload, but can be done during other times of high workload.

Pure speculation, but it's a possibility.

Another speculation comes from a big iron pilot I know. It might be that the pilots had not been told by the engineers that premature unlocking of the mechanism could result in premature deployment of the feathering mechanism (this assumes the engineers knew). So it may be the co-pilot unlocked the lever thinking something like "I'll take care of this now while it's on my mind" without realizing it would result in disaster.

Again, pure speculation.

Both of those scenarios go beyond simply "the human fucked up", which is essential when you're studying human factors. You need to find out why the human fucked up in order avoid future fuck ups, or at least reduce them to a minimum.

[GrandMasterTerwynn]

I'm wondering why SS2 operating procedures calls for unlocking feathering mechanism so early while the engine is still running? Feathering maneuver is required during reentry so it would make sense to unlock safety mechanism when craft is at apogee or close to it. Main engine burn is when you would absolutely want the tail booms horizontal and locked in place to prevent exactly this sort of disaster.

From what I've gathered in other places, they're supposed to unlock it (but not deploy it) to verify that the system is working, since they'd rather not find out that it's not unlocking when they need it for reentry (when they need it to slow the aircraft down.)

Now, why they specify Mach 1.4 as the velocity to do this? Don't know. It's probably because the aircraft is firmly supersonic at that point. The transonic flight regime is one where severe turbulence can be encountered, and the co-pilot unlocked the feathering mechanism right around Mach 1.

[Sky Captain]

I'm wondering why SS2 operating procedures calls for unlocking feathering mechanism so early while the engine is still running? Feathering maneuver is required during reentry so it would make sense to unlock safety mechanism when craft is at apogee or close to it. Main engine burn is when you would absolutely want the tail booms horizontal and locked in place to prevent exactly this sort of disaster.

From what I've gathered in other places, they're supposed to unlock it (but not deploy it) to verify that the system is working, since they'd rather not find out that it's not unlocking when they need it for reentry (when they need it to slow the aircraft down.)

Now, why they specify Mach 1.4 as the velocity to do this? Don't know. It's probably because the aircraft is firmly supersonic at that point. The transonic flight regime is one where severe turbulence can be encountered, and the co-pilot unlocked the feathering mechanism right around Mach 1.

That would make some sense, maybe mach 1.4 is the fastest speed when SS2 can safely slow down without deploying feathers so if the mechanism is jammed they can stop the engine and glide back to landing site.