This comment was made in the weekend context, when most reasonably assumed that the engine had caused the disaster:
The decision to change the fuel may have been behind the crash. Experts questioned whether pressure from investors might have been a factor in decisions by Sir Richard Branson and Scaled Composites, the spacecraft’s designers, to pursue what many considered to be a flawed design.
“If Sir Richard wants to move forward with his business, he needs to go back to the drawing board,” said Mr Simberg, the author of Safe is Not an Option. “Many in the industry, including me, have been concerned about Virgin’s propellant system for years.”
Obviously, I expect them to continue down the current path now, absent some new engine concern. But my warnings were never that much about safety (though as I wrote on Saturday, the safety of hybrids has been dramatically overhyped), but whether or not it was a good engine from a business standpoint, in terms of performance, operability, turnaround, cost, and getting the vehicle to market soon. Those concerns have not gone away.
[Update a while later]
A pretty comprehensive story, including history, over at Popular Mechanics. He’s not sanguine about the prospects for the vehicle, though (like me) doesn’t see it as a setback for the industry itself.
[Update a while later]
What does this mean for New Mexico? A long but useful backgrounder.
[Update early afternoon]
Someone over at Arocket found a video of a previous SS2 flight in which feathers were unlocked ten seconds into the burn (as opposed to nine seconds on Friday). So if it was early, it wasn’t very. Not obvious pilot error yet.
More ready, fire, aim type of responses….
All you had to do is look at the pictures of the parts on the ground to see that there was no engine explosion.
And the comments by people like Carolynne Campbell and G. Darcy were unconscionable.
The good news here is the wealth of data the NTSB will have available and the close co-operation amongst all parties to the investigation. Yes, this will no doubt slow the investigation, but hopefully we will, in the end, have TWO significant outcomes.
1) The cause (and more importantly)
2) Recommendations for systemic alterations to improve vehicle operation. In all three categories: hardware, software and peopleware.
Of course most of the value of 2 is lost if the program is terminated. Rand, does your book address opportunity loss when this happens?
No, not really.
Difficult to imagine the pilot or co-pilot actually engaging the feather. Did this mishap occur for want of an AND operation?
In terms of business, Branson has a lot customers who paid/ordered a ticket to space- so I would think that’s most important aspect. Next, Branson is not rocket engineer, perhaps he focus more on using his mothership- it’s airplane, people could a need for that airplane. Perhaps focus on being able to commercially use that mothership. Or basically there is going to be a fair amount down time on using a
SpaceShipOne, obviously it’s delusional to imagine one going fly passengers on SpaceShipOne starting
next year. It might not be bad as Space Shuttle accident requiring couple years [though it could be but it if over eager to fly SpaceShipOne, you going to have political problems- or you going to greatly strengthen the hand of government to step in and say, “no you don’t”.
So as said, focus on the customers you have, and work toward them getting what they wanted, and might not be related to being on SpaceShipOne.
Wrong spaceship.
Well that is strange. In that older video we clearly hear them say they’ve unlocked the tail about ten seconds into powered flight. So that’s not what “caused” the accident (though perhaps not doing it could have prevented it).
Why do they do that?
The elevators are, as usual, on the tail. If the tail is unlocked, does that mean it can swing freely? I don’t suppose so — what pitch control would they have then? I don’t think there are vanes or gimbals on the engine.
So the tail position must then be controlled by the feathering mechanism. Do they actively move the entire tail in supersonic flight for pitch control? It wouldn’t need to be be much. As we know, normal elevators don’t work too well in transsonic and supersonic flight and this was the most closely guarded secret of the F-86 Sabre.
Which raises the interesting question of whether the tail can go a little *below* the locked position, to pitch the nose down, or is there a stop there?
Pure speculation, of course, but this could yet come back to the engine, with something like off-axis thrust overpowering the tail movement mechanism.
From the looks of things, it definitely seems like Virgin & Scaled will fix the premature feather issue and press on with the plastic + N2O engine. Given the comments by Doug Messier & Joel Glenn Brenner over the weekend, this may be sewing the seeds for future disaster. It remains to be seen if there are performance, reliability or vibration issues with the new motor. Given the years of slips we’ve seen with SpaceShipTwo, we should also be concerned that corners could be cut in the remaining test flight series so they can get the commercial flights going.
The answer on the question of pilot error will probably be a qualified “yes and no.” Yes the copilot unlocked the feather mechanism too early, but no in the sense that the feather mechanism deployed because of some mechanical fault, without the second lever thrown.
Ahh, no, the outboard horizontal tail surfaces are all-moving, as evidenced by the angle markings painted on the vertical tail (same as jetliners have), and the differing positions in these two photos.:
http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2011/05/ss2-tiffany-1.jpg
http://pansci.tw/wp-content/uploads/2014/11/virgin-galactic-spaceshiptwo-glide-flight-dec-11-2013.jpg
Interestingly, it’s only using a *quarter* of the available up elevator movement in the landing photo, and has very little (marked) down elevator ability.
Can anyone explain the purpose of unlocking the feather mechanism so early in the flight profile? I would have thought it would have remained locked at least until the end of the powered flight phase.
An observation: is SS2 really that unstable about the yaw axis or was that rocking back and forth during the climb intentional?
So in this video, an NTSB guy says they are supposed to unlock the feathers at Mach 1.4, but they did it before that speed.
http://www.bbc.com/news/world-us-canada-29889021
I still don’t get why they’d unlock it at such a time, rather than just before they deploy it for reentry.
SpaceShipOne was also unstable around the yaw axis, to the point that in some flights it was spinning like a top on the way up. I think it’s because of the way the hybrid engine thrust comes out, rather than something aerodynamic.
If they unlock it only when they’re ready for reentry, and it doesn’t work, they’re screwed. If it fails to unlock at Mach 1.4 they’ve still got time to abort before they get too fast and too high.
I’d certainly unlock it on the way up, not the way down, but it seems nuts to do it at a dynamic pressure where the vehicle can be destroyed!
I don’t know how high they got in this flight.
In PF01 a 16 second burn took them to 56200 ft and Mach 1.3. I suspect they didn’t feather.
PF02 was a 20 second burn, with a pull to vertical and feathered descent. The call to unlock was right around the 16 second mark. The scaled flight log doesn’t list the peak speed or height, but in the video Rand posted you can hear them call “65 … 66” just before they pitch down and deploy the feathers, which I assume means they just topped 66,000 ft.
Rand, is Arocket still operational? I haven’t gotten any email postings from them in months.
Bob Clark
Seems to be. Maybe you got unsubscribed.