Virgin Galactic SpaceShip 2 Test Flight Crash 2014-10-31

[Grendal]

What a terrible tragedy. No matter how you look at it sitting on top of a rocket engine is dangerous. We've seen two tragedies for aerospace this week. It's too bad there was loss of life in this instance. The whole point of the Virgin Galactic was to make a safe flight for tourists to experience the incredibly rare opportunity of sub-orbital space. I can't imagine that too many of those waiting in line will want to continue with the plan when the danger is shown to be too high.

I really hope that nothing like either of these tragedies will ever happen to SpaceX, however, the realistic side of me says that it must happen eventually.

 

[Grendal]

The journalist on the other end of the phone line in the CNN report, Joel Glenn Brenner, who has followed this story since Space Ship One days, was extremely upset about what she perceives as a gap between the enthusiasm of the Virgin Galactic team and the 'level of technology' they have employed in pursuit of the dream of commercial space tourism. She minced no words, saying that even if this flight had been successful, there is no way this particular type of engine would have succeeded in powering SS2 into space.

As an armchair commenter, I believe what she is trying to say is that the engine would never have been able to generate enough thrust to get SpaceShipTwo to the suborbital position they were shooting for. There is reason that SpaceShipOne was as small as it was. SpaceShipTwo is four times the size of SpaceShipOne. That means the engine needs to have more than four times the thrust to achieve the same thing.

This is what makes SpaceX achieving reusability so amazing. The fact that they can carry enough fuel to make it to orbit and is not surprising. Having enough fuel left over to bring the ship back and have it land successfully is incredible. This also explains why both SpaceX and Boeing didn't waste their time with a reusable rocket plane. Do the gains of using wings in an atmosphere outweigh the added stress to the structure and extra fuel needed to drive the winged structure out of the atmosphere? Both SpaceX and Boeing did the math and said that it isn't.

 

[c041v]

Okay, I've been a SpaceX follower for some time, and am currently reading "Ignition! An informal History of liquid rocket propellants" so I'd like to think I know slightly more than the average person, but I am also an armchair commentator.

Excuse my ignorance, but how can a 'hard start' the narrator is referring to occur after a rocket has burned for 2 seconds as indicated? Hard starts, to my knowledge are the result of either insufficient ignition sources or an improper fuel/oxidizer ratio pre-ignition. As the fuel was solid (Thermoplastic Polyamide) I don't understand how it could have pooled enough to cause a hard start.

Terrible news. As someone pointed out, it's been a tough week for aerospace. This really emphasis the significance of SpaceX's record to date and decision to use engines of their own design with the more traditional Kerolox fuel/oxidizer combo.

 

[wiztecy]

I personally believe (one side) of the rear tail broke off, then the whole craft broke apart from lack of aerodynamics, the pure forces of the speed, friction, and power of the new engine as well as turbulence from the engine. Both those tails are purely exposed to the fierce forces of the engine's turbulence, with no lateral reinforcement at all, and also they rotate vertically which just look like trouble and weaken the strength. Wow, more points of failure with a single vertical rotation point. Meaning that there's less support for that tail. The newer engine put out significant more force and power which put more stress on that tail and shook it until it broke at the pivot point or middle section of its tail body by the flat section by the Virgin name. I most likely see the failure being at the pivot and they overlooked the specification of that pivot with the enhanced power of the newer engine. But then I also could see stress put on the middle part of the tail section that went unnoticed and untested. The new engine put enough force to cause the stress point to fail.

Why have the tail pivot like that, there is so much stress on that point. Also its right in the turbulence of the rocket engine. There are no lateral supports between the two tail sections out on a long fulcrum.

You can see in this pic that one of the tail sections tore off while spaceship 2 was still being jettisoned. There is no explosion.

The whole concept is too overly complex. Spaceship 2 and WhiteNight 2. Things that are complex tend to have to have more failure points.

You can see above that one of the tail sections made it down in a close to one piece / section. My thought is that since this piece is still intact in a large section, that it had to have broken off first. If the engine blew I'd expect to see smaller pieces from the force of the explosion. This piece above is most likely the piece falling off in the upper right picture two picture that in the pic above it.

 

[Cosmacelf]

Here a good article written one day before this accident. Very prescient.

Apollo, Ansari and the Hobbling Effects of Giant Leaps at Parabolic Arc

Once again, Elon does it right while all else around him makes strategic error after strategic error.

 

[ecarfan]

Remarkably prescient article about the risks in "not knowing what you don't know". I think Elon is keenly aware of that. He stuck with tried and proven propellants and focused on rethinking the concept of rocket reusability while avoiding the known drawbacks associated with designing spacecraft that glide back to an earth landing.

 

[Doug_G]

That photo certainly shows structural failure and no sign of an engine failure. The tail fins appear to have broken off first.

That does not necessarily mean that failure of the tail fins initiated the incident; if the vehicle started tumbling then I'm sure they would break off first. The incident could have been initiated by a controls failure, or a structural failure, or even an engine problem (e.g. on Challenger the structural failure was caused by a relatively small jet of hot gas escaping from the solid rocket booster).

 

[ggr]

That photo certainly shows structural failure and no sign of an engine failure. The tail fins appear to have broken off first.

That does not necessarily mean that failure of the tail fins initiated the incident; if the vehicle started tumbling then I'm sure they would break off first. The incident could have been initiated by a controls failure, or a structural failure, or even an engine problem (e.g. on Challenger the structural failure was caused by a relatively small jet of hot gas escaping from the solid rocket booster).

Or, having read the article mentioned above, maybe the motor vibrations got to it.

 

[James Anders]

That photo certainly shows structural failure and no sign of an engine failure. The tail fins appear to have broken off first.

That does not necessarily mean that failure of the tail fins initiated the incident; if the vehicle started tumbling then I'm sure they would break off first. The incident could have been initiated by a controls failure, or a structural failure, or even an engine problem (e.g. on Challenger the structural failure was caused by a relatively small jet of hot gas escaping from the solid rocket booster).

It is amazing how quick some are able to speculate in the absence of the facts. If the vehicle experienced a deviation in attitude then the fins would have been overly stressed. Some have pointed out that the pictures show the vehicle traveling backwards in the photo.

If the engine had exploded it's not out of the question that the resultant force could have caused the vehicle to rotate thus causing extreme forces on the airframe.

The facts will be known soon.

 

[wiztecy]

If you look at the trajectory SS2 takes, it ran into issues 2 minutes into the drop from SS1. Its trajectory takes a rather steep and close to a very quick 90 degree turn up at almost supersonic speeds. I don't know where the 2 minutes would put SS2 in its route to space 62 miles up. Any idea why the tail needs to pivot like that? Is it for re-entry?

 

[ggr]

If you look at the trajectory SS2 takes, it ran into issues 2 minutes into the drop from SS1. Its trajectory takes a rather steep and close to a very quick 90 degree turn up at almost supersonic speeds. I don't know where the 2 minutes would put SS2 in its route to space 62 miles up. Any idea why the tail needs to pivot like that? Is it for re-entry?

View attachment 62806

The tail pivots for re-entry, so that the main body acts like the heat shield on a capsule, and allows the ship to slow down and survive re-entry to the atmosphere.

But bear in mind, this was not a flight that was headed up to space, it was just a test of the new rocket motor.

 

[wiztecy]

Thanks! So most likely they were only going forward for this to test the thrust and performance of the new engine.

Appears in the last test they did some climb, reaching 71,000 feet or 13 miles (from the 46k ft./8.7 mile drop alt. from SS1) and mach 1.4.

SpaceShipTwo sets new altitude and speed records

So the previous SS2 test they say the engines ran for 20 seconds, "The SS2 rocket engine fired for 20 seconds, pushing the suborbital spacecraft to an altitude of 71,000 ft (18 km) and a top speed over Mach 1.4, both of which were new records for SS2."

In the test that failed they said it failed after 2 minutes, counting from the point being dropped from WK2.

So to me it seems like the new engine ran longer. I don't see SS2 falling to the earth for 100 seconds before they fire off the rocket engine to be at the same duration of run-time for the engine as compared to the earlier test. So that alone has more stress on everything, the motor, its components/delivery system, and the tail.

All that black soot in the pic was one issue they were trying to resolve with the new plastic (petroleum) based fueled rocket motor. The previous one was rubber. The new plastic based fuel offered better performance and more thrust.

Here's a video of the tail section, it appears they did rotate it and shoot up in a 90 degree angle after the drop from the test before:

SpaceShipTwo's Intense Rocket Ride - Tail View and Cockpit Recording | Video

In the video following the one in the link above, a person talks about the accident, he stated that the engine after the drop didn't perform properly, it fired then shut down then fired again. They called it a hard restart when it refired. They said the ship broke apart without any explosion.

 

[ggr]

Thanks! So most likely they were only going forward for this to test the thrust and performance of the new engine.

Appears in the last test they did some climb, reaching 71,000 feet or 13 miles (from the 46k ft./8.7 mile drop alt. from SS1) and mach 1.4.

SpaceShipTwo sets new altitude and speed records

View attachment 62807

So the previous SS2 test they say the engines ran for 20 seconds, "The SS2 rocket engine fired for 20 seconds, pushing the suborbital spacecraft to an altitude of 71,000 ft (18 km) and a top speed over Mach 1.4, both of which were new records for SS2."

In the test that failed they said it failed after 2 minutes, counting from the point being dropped from WK2.

So to me it seems like the new engine ran longer. I don't see SS2 falling to the earth for 100 seconds before they fire off the rocket engine to be at the same duration of run-time for the engine as compared to the earlier test. So that alone has more stress on everything, the motor, its components/delivery system, and the tail.

All that black soot in the pic was one issue they were trying to resolve with the new plastic (petroleum) based fueled rocket motor. The previous one was rubber. The new plastic based fuel offered better performance and more thrust.

Here's a video of the tail section, it appears they did rotate it and shoot up in a 90 degree angle after the drop from the test before:

SpaceShipTwo's Intense Rocket Ride - Tail View and Cockpit Recording | Video

In the video following the one in the link above, a person talks about the accident, he stated that the engine after the drop didn't perform properly, it fired then shut down then fired again. They called it a hard restart when it refired. They said the ship broke apart without any explosion.

"Hard (re)start" is a euphemism for a small explosion, according to "Ignition!" (which I just read).

 

[wiztecy]

"Hard (re)start" is a euphemism for a small explosion, according to "Ignition!" (which I just read).

Interesting terminology.

In this article it appears the "Feather Tail" began to deploy before it was scheduled to do so. With that, aerodynamics would be breached and those very vulnerable laterally unsupported tails would just snap. Hence the picture of SS2 that appeared it was going backwards. I'm sure without any rear stability the spaceship just tossed around. The mach 1+ forward momentum would keep its motion moving forward while the ship rotated around while breaking up.


SpaceShipTwo 'Feather' Tail System Deployed Prematurely: NTSB - NBC News

"SpaceShipTwo's unique tail section, which can "feather" at an angle to help the Virgin Galactic spacecraft make a safe descent, unfurled as it was ascending during the flight that ended in a fatal breakup Friday and without being ordered to do so, federal investigators said Sunday night.

The "feathering" mechanism isn't supposed to be unlocked until the spacecraft reaches 1.4 times the speed of sound, Christopher Hart, the NTSB's acting chairman, said at a news conference. But on the flight that crashed Friday, co-pilot Michael Alsbury moved the mechanism's lock-unlock lever into the unlocked position earlier, at just slightly above Mach 1, Hart said.

The "feathering" procedure is supposed to require two separate steps to engage: First, a pilot must unlock the feather parameter; then he or she must move a feather handle into position. SpaceShipTwo's feather mechanism began moving almost immediately — even though neither pilot took that second step, Hart said. That would have increased the plane's atmospheric drag at just the wrong moment. "

 

[Cosmacelf]

Is it just me, or does anyone else think that having a gymballed tail on a supersonic craft is asking for trouble? Just seems like a complicated way to maintain stability. SpaceX first stage manages to stay stable and come back to earth in a controlled way with much simpler control surfaces that aren't prone to snapping off.

 

[Matias]

I think the "good" thing is that according to that NTSB report the problem was in the feather mechanism. I think it is easier to fix than engine instability.

 

[HVM]

Both Doug Messier and Joël Glenn Brenner seems to jump the gun here. (e.g. no explosion or hard start)

 

[Doug_G]

That would certainly explain the photo of the incident - spaceship flying backwards, the tail segments trailing behind.

 

[sderrick]

Isn't it amazing how wrong the first reports/guesses were! I don't recall any suggestion of a control surface malfuction or missdirected control input.

Even this report of premature feathering is somewhat early and most likely doesn't tell the whole story.

 

[c041v]

Isn't it amazing how wrong the first reports/guesses were! I don't recall any suggestion of a control surface malfuction or missdirected control input.

Even this report of premature feathering is somewhat early and most likely doesn't tell the whole story.

I'm curious to see what develops. I'm not sure how a system becoming unlocked and supposedly deploying somewhere above Mach 1, but less than the desired Mach 1.4 could cause a catastrophic failure. I don't know enough about aerodynamics to know why it was a problem when when the craft was already supersonic.

Cosmacelf - I with you. Rutna's designs have always been elgant, but IMO, overly complicated. It may have worked well for Aircraft, but I'm not so sure it translates into SapceCraft.