Orbital Sciences rocket explodes on launch

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paperburn1
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Re: Orbital Sciences rocket explodes on launch

Post by paperburn1 »

It is my understanding that this was the first test of a new fuel type. It was polymer-plastic based rather than normal rubber tire based product that they were using. Ground test of this fuel were performed successfully with no indication of any problems. It's my understanding that the reason for switching to this fuel type was to provide a little bit more thrust.
I am not a nuclear physicist, but play one on the internet.

KitemanSA
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Re: Orbital Sciences rocket explodes on launch

Post by KitemanSA »

D Tibbets wrote:Probably, as I suspect the clamps holding the rocket down are not released till telemetry indicates both liquid fueled engines operating normally with full thrust built up. This is different from solid boosters where it is goodby once the solid rocket is lit. This happend once with the shuttle. The main engines were started, an anomaly was detected before the solids were lit, so the launch was aborted.
I was in the VIP stands when that happened. Total disappointment.

Aero
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Re: Orbital Sciences rocket explodes on launch

Post by Aero »

Do we have a thread regarding the SS2 failure in flight test? One dead, the other pilot is in critical condition.
Aero

GIThruster
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Re: Orbital Sciences rocket explodes on launch

Post by GIThruster »

Yeah, it's been getting posted here. early rumor is they test pilot rotated the tail section early at Mach 1 instead of the designed Mach 1.4 and this may have led to the failure. Sounds like it just broke up. If this is true, the new plastic based rocket motor would long earlier have burned out. The tail rotates for reentry only.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

D Tibbets
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Re: Orbital Sciences rocket explodes on launch

Post by D Tibbets »

GIThruster wrote:Yeah, it's been getting posted here. early rumor is they test pilot rotated the tail section early at Mach 1 instead of the designed Mach 1.4 and this may have led to the failure. Sounds like it just broke up. If this is true, the new plastic based rocket motor would long earlier have burned out. The tail rotates for reentry only.
This is confusing for me. Rotate the tail may actually have two meanings. Rotation is a term commonly applied when air control surfaces are used during takeoff in order to lift off from the runway. Applied to SS2 this may mean the use of air flight control surfaces to initiate climb after the solid rocket is lit. At Mach 1.0- transonic speeds, there is a lot of turbulence and stresses on different parts of the aircraft. Deploying flaperons or whatever at that point might lead to dangerous stresses- aircraft tears apart. If the pilot initiated flight control inputs to do this, then the results might be this. The flight control rules should prevent this unless the pilot had unlimited manual control, the computer failed, the programing was flawed, or there was a mechanical failure somewhere in the control loop. The new rocket engine may have given a bigger kick as it started and this might have caused some mechanical failure in the control or actuater system. The subsequent actual deployment of airodynamic control surfaces could have then torn the aircraft apart. So, the error could have been the pilot, flight control command system, or mechanical system. It may be that the airframe was just not prepared for the rocket startup kick, though that would seem to be a tested for parameter.

Rotation as applied to feathering the tails for the shuttlecock like stabilization during reentry is a different process entirely. If deployed in relatively dense air at transonic speeds or under rocket thrust it might also tear the aircraft apart. Hopefully the flight control system would prevent it's use except during the appropriate time.

In either case, if the craft broke up for these reasons, it is not a direct engine failure, it is a failure of the integrated systems, either as conceived or as implimented.

Or, none of the above....

Dan Tibbets
To error is human... and I'm very human.

paperburn1
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Re: Orbital Sciences rocket explodes on launch

Post by paperburn1 »

Flying at transonic speeds can cause several problems. The most obvious are control reversal and flutter. Sometimes an aircraft get into a configuration that will cause severe buffeting especially when going from supersonic to transonic speeds. One would think that the engineer that spaceship one would have accounted for the these factors. Perhaps the feathering effect was deployed to soon, the air too thick and it somehow got into a regime of flight that tore apart as it decelerated through mach one. That was the doom of many test flights that manage to make supersonic speed. As soon as they started to slow they tore up into pieces.
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paperburn1
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Re: Orbital Sciences rocket explodes on launch

Post by paperburn1 »

As far as to my understanding, the only good thing that will come out of this problem they will will be able to figure out exactly what went wrong. The flight vehicle was heavily instrumented, aglow with live and recorded telemetry. Even to the point of having six different cameras mounted to observe the control surfaces in-flight
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paperburn1
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Re: Orbital Sciences rocket explodes on launch

Post by paperburn1 »

I just watched an NTSB briefing and the preliminary investigation revealed that the tail feathering mechanism was unlocked at Mach 1.0. This lever is not supposed to be moved to the unlocked position until Mach 1.4. Two seconds after the lever was moved to the unlocked position flight elementary terminated with the disintegration of the aircraft. Currently it is unclear if the secondary switch that actually moves the tail into the feathered position was actuated. In my experience working with aviation for the past 30 years and I have some familiarity with transonic and mach flight this was the absolutely worst time for any control surface to move. Right at the point when they were transitioning from sub Mach to Mach speeds. With the current data that we have in place is my opinion that when they unlock the tail there was a control reversal effect on the tail plane that sucked into a position that cause the aircraft to tear apart.
I am not a nuclear physicist, but play one on the internet.

GIThruster
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Re: Orbital Sciences rocket explodes on launch

Post by GIThruster »

D Tibbets wrote:
GIThruster wrote:Yeah, it's been getting posted here. early rumor is they test pilot rotated the tail section early at Mach 1 instead of the designed Mach 1.4 and this may have led to the failure. Sounds like it just broke up. If this is true, the new plastic based rocket motor would long earlier have burned out. The tail rotates for reentry only.
This is confusing for me. Rotate the tail may actually have two meanings.
That was my term, not theirs. The ship has a variable geometry and the tail section rotates 90* to reenter something like a badminton shuttlecock. That shape change is supposed to occur at Mach 1.4 and appears to have occurred early at Mach 1. Whether this was the cause of the accident or not remains to be seen but this was pilot error.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Skipjack
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Re: Orbital Sciences rocket explodes on launch

Post by Skipjack »

GIThruster wrote:
D Tibbets wrote:
GIThruster wrote:Yeah, it's been getting posted here. early rumor is they test pilot rotated the tail section early at Mach 1 instead of the designed Mach 1.4 and this may have led to the failure. Sounds like it just broke up. If this is true, the new plastic based rocket motor would long earlier have burned out. The tail rotates for reentry only.
This is confusing for me. Rotate the tail may actually have two meanings.
That was my term, not theirs. The ship has a variable geometry and the tail section rotates 90* to reenter something like a badminton shuttlecock. That shape change is supposed to occur at Mach 1.4 and appears to have occurred early at Mach 1. Whether this was the cause of the accident or not remains to be seen but this was pilot error.
I don't think that the actual shape change was meant to occur then, only the unlock of the feather mechanism.

mvanwink5
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Re: Orbital Sciences rocket explodes on launch

Post by mvanwink5 »

Face it, the unlocking procedure based on speed alone as it has been reported makes no sense if the rocket is still firing, as whether speed is mach 1 or 1.4, releasing the manual safety interlock while the rocket is thrusting removes your safety from a catastrophic tail brake system malfunction.

I guess at some point this will be clarified, but for now it makes no sense to me.
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Tom Ligon
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Re: Orbital Sciences rocket explodes on launch

Post by Tom Ligon »

KitemanSA wrote: I was in the VIP stands when that happened. Total disappointment.
I watched the last launch of the Columbia from the road side near Titusville.

Stephanie Osborn, Arlan Andrews, and I have an article in the December Analog Science Fiction and Fact, currently in print. Stephanie lost a good friend on that flight, and was crushed by it.

Trust me, there are worse feelings than watching a scrubbed launch.

We were sufficiently moved that we've been working on an astronaut escape system.

http://www.analogsf.com/2014_12/index.shtml

DeltaV
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Re: Orbital Sciences rocket explodes on launch

Post by DeltaV »

I was at Apollo 12 and STS-3.

Apollo 12 got hit by lightning (inside a cloud, didn't see the strike).

D Tibbets
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Re: Orbital Sciences rocket explodes on launch

Post by D Tibbets »

If the feathering lock was released early, it raises several questions. Why the Mach 1.4 limit during powered assent.It seems it should be locked out until after rocket burnout, and deployed only when in space. Was the lock out lever actuated by the pilot, or was it knocked out of position by the G forces as the rocket fired and the aircraft was jarred and shaken? If there is a lockout switch and also an actuater switch, how did they both get actuated. Again, pilot , mechanical failure, or if one or both actuaters were computer controlled, a failure there?

Dan Tibbets
To error is human... and I'm very human.

paperburn1
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Re: Orbital Sciences rocket explodes on launch

Post by paperburn1 »

As posted by DK in the spaceship two thread
There's some really good discussion on the NASA Spaceflight Forum. The consensus there seems to be that the feather unlock is done during the burn so that you have the option to abort the burn if it won't unlock. Once the burn is done you're headed for space no matter what you do. If you find out at that point that you can't configure for reentry, it's too late.

This makes perfect sense to me as the higher-speed would put them in a flight regime that would not have dynamic instabilities due to crossing the mach threshold. One could theorize that at anything above Mach 1.1 the dynamic forces on the tail plane would hold it in the correct position. As stated earlier in my theory at Mach or slightly below mach control reversal is a distinct possibility not to mention the dreaded flutter that was the death of many test air craft.
I am not a nuclear physicist, but play one on the internet.

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