Antares launch/failure discussion.

[Kryten]

I don't really know if there were any issues with engines after successful burn test before. Were there?

SpaceX and Energomash have both had it happen. There are plenty of flaws that'll reduce an engines lifetime rather than flat-out destroy it; in these cases, tests make the situation worse.

[J.Random]

Well, Orbital guys suspect turbopump. So, either defect of the pump itself (I guess burn test should've shown it), or something (extraneous particle?) in the fuel, right?

[Kryten]

Given they're proposing retiring the engine, they seem pretty certain of an actual turbopump issue. The likely replacements would have exactly the same reaction to foreign objects as NK-33.

[J.Random]

Given they're proposing retiring the engine, they seem pretty certain of an actual turbopump issue. The likely replacements would have exactly the same reaction to foreign objects as NK-33.

Not necessarily. They may just be worried that noone will insure their launches again until they step away from "40 years old russian engine refurbished and refit in Ukraine and (at times, explosively) tested by AJR".

[GigaG]

I've noted the irony of the rocket failrue being similar to the N1-5L launch failure - a rocket which used the Antares engine's predecessor. Wasn't the second N1 launch failure caused by debris being sucked into a LOX pump, as J.Random might have been suspecting? (The first also may have had a debris-related failure.)

Note that I highly doubt that this has anything to do with it - the original N1 engines got fuel filters installed after the disaster IIRC, and the Antares engines likely had all the improvements and then some. IIRC, the Antares engines were designed for the 5th N1 that never flew (can somebody back me up on this?)

Here's how I imagine the Antares accident unfolded-

-Rocket launches

-Something happens, turbopump malfunctions. We see the rocket exhaust suddenly change color (Either this forum or Orbiter-Forum had a post which proposed that excessive LOX pumping could cause this.)

-Entire engine explodes, destroying engine and essentially disabling other engine. This also may have ignited some of the rocket's fuel - the initial explosion is fairly big. The rocket loses almost all thrust and beings to fall.

-Rocket trails fire as it falls towards earth. I believe that this is either the (likely damaged) second engine still partially burning or a fuel fire.

-Range safety officer blows up rocket just before it impacts ground.

Some notes-

-The rocket had to have lost almost all of its thrust - it almost immediately quit climbing. The second engine was either shut down or damaged to the point of not functioning - I believe that the rocket would have begun its fall more slowly had the second engine functioned properly throughout the accident.

-The second engine may have still been trying to work. Either this or a fuel fire, would explain why the rocket trailed fire on its way down. (I don't know if the sound stopped pre-explosion or not.)

[GoSlash27]

That doesn't make any sense; everything was going well, until something happened within the turbopump.

As Sgt Flyer pointed out above, there are other staged cycle lean- burn russian engines out there. The difference is this one was so small and light that they didn't have the real-estate to implement proper cooling. They cryo-cooled the impeller bearings and ran both fuel and o2 on a single shaft.

Here's the important part: This engine didn't survive under standard operating conditions using standard metals of the day.

The other engines did.

They actually had to invent new alloys in order to make these engines survive *in normal operation*. It's running close to the redline when there's nothing wrong at all. When things *do* go wrong, it can easily exceed it's design parameters and go kablooey, which these engines did with alarming regularity.

It's not a simple problem of "old engines" or "Russian technology". You could build brand- spanking new ones with modern techniques and still face this problem simply because this design lives on the edge.

Best,

-Slashy

[Kryten]

It's the exact same technology as used in the RD-170 and it's descendants, and they're perfectly reliable. The test stand failure that we do have a proper failure report for was caused by age-related cracks.

[Sky_walker]

So, of course aerojet checked those engines thoroughly (x-rays and such) to check for the smallest crack,

They did not. Otherwise last test stand failure wouldn't happen.

[Mighty1]

Does anyone know what kind of meshanism is used by the Range safety officer to blow it up in case of failure?

[sgt_flyer]

Well, x-raying and other non destructive tests are common in the aerospace industry (other industries use them as well to check welds and such)

However, one problem that might prevent for full tests, is the fact that those engines are already assembled - so it may not be possible to check out some of these. (Especially things stuck between welded parts.

For a fresh part that was checked just before assembly, there's no problems, but for a part which stayed there for 45 years, that might be more of an issue if you can't recheck it

@mighty1 there's not a lot of ways for a liquid rocket booster self destruct - if there's no risks, (ex : the rocket has already enough speed so that it will fall in the ocean) a simple engine shutdown would be enough.

If the rocket might fall back on ground with full fuel tanks, they want to make the fuel + oxydizer to combust before reaching ground. For this, the rocket would have explosives placed and designed to simply tear open the fuel + oxydizer tanks.

For the SRB components of rockets (like the antares upper stage) the self destruct explosives would be used to break the solid fuel into small chunks and discard the casing without creating too much sharpnels.

Edited November 7, 2014 by sgt_flyer

[Frida Space]

Does anyone know what kind of meshanism is used by the Range safety officer to blow it up in case of failure?

When the range safety officers see that something is wrong with the rocket, they either (1) command the rocket to shut-down its propulsion system or (2) they trigger the Flight Termination System (FTS). The FTS had redundant transceivers in the launch vehicle that can receive a command to self-destruct by setting off charges in the launch vehicle to combust the rocket propellants at altitude. (Source Wikipedia)

It's interesting to note that the safety officers, at least for the very first seconds after liftoff, don't look at any data, they just use their eyes. That's because there is too much interference on the ground coming from trees and nearby structures for radar and other monitoring systems to be accurate. If the rocket crosses one of the guide wires the officers use, they know it's veering off course and send an abort call. (Source National Geographic)

[Kryten]

Does anyone know what kind of meshanism is used by the Range safety officer to blow it up in case of failure?

Explosive charges on the domes of the oxidiser and fuel tanks.

[magnemoe]

Well, x-raying and other non destructive tests are common in the aerospace industry (other industries use them as well to check welds and such)

However, one problem that might prevent for full tests, is the fact that those engines are already assembled - so it may not be possible to check out some of these. (Especially things stuck between welded parts.

For a fresh part that was checked just before assembly, there's no problems, but for a part which stayed there for 45 years, that might be more of an issue if you can't recheck it

@mighty1 there's not a lot of ways for a liquid rocket booster self destruct - if there's no risks, (ex : the rocket has already enough speed so that it will fall in the ocean) a simple engine shutdown would be enough.

If the rocket might fall back on ground with full fuel tanks, they want to make the fuel + oxydizer to combust before reaching ground. For this, the rocket would have explosives placed and designed to simply tear open the fuel + oxydizer tanks.

For the SRB components of rockets (like the antares upper stage) the self destruct explosives would be used to break the solid fuel into small chunks and discard the casing without creating too much sharpnels.

Rather they want to create sharpnels of the upper stage, they don't want it to come down as one piece and hit something, if they blow it the pieces will have far higher air resistance than an aerodynamic rocket stage.

[sgt_flyer]

Well, for the srb, i meant that they want to avoid at all cost a pressure buildup inside the casing fragments of casing simply falling off is less dangerous than a pipebomb sending sharpnels everywhere (imagine an srb's solid fuel igniting with it's nozzle bent or blocked by other debris - the pressure inside could rise pretty fast simply breaking up the shape with explosive ensure that there will not be an explosion sending those fragments everywhere at high speeds the fragments after a self destruct would much more follow the old trajectory - but the remains of the solid fuel will simply burn without allowing the resukting gases to create an overpressure. (Even if they have way to predict where the srb would break in case of overpressure (ex, the casing is thinner on one point, so the overpressure would make this pop out before anything else), no overpressure is still safer )

Edited November 7, 2014 by sgt_flyer

[Kulebron]

I don't think something like this can happen to Kerosene (why am I writing it with kapital K?), but worth mentioning.

At 4:12 watch a cylinder lift off like an SRB.

(This is what happens when 90% of drivers are first generation of car owners.)

Edited November 7, 2014 by Kulebron

[Mazon Del]

Towards the end of that video, there is a police car that got all close up for some reason earlier, it decides to move back after a can goes shooting around and almost smashes right into it.

Let that be a warning for you all, in situations like this with canisters of gas laying around, just because the explosions have stopped doesn't mean the canisters are no longer a threat!

[Aethon]

New close up images of the launch failure.

"All of our team’s cameras and image cards were impounded by Orbital’s Accident Investigation Board (AIB) that was assembled quickly in the aftermath of the disaster and charged with determining the root cause of the launch failure.The photos captured on our image cards were used as evidence and scrutinized by the investigators searching for clues as to the cause, and have only just been returned to us in the past two days. Similar NASA and Orbital Sciences photos have not been publicly released."

http://www.universetoday.com/116580/antares-doomed-descent-into-hellish-inferno-up-close-launch-pad-photo-exclusive-pt-1/

[Aethon]

New video. About twice as long as it needs to be.

[megatiger78]

we all no the problem here. needed more boosters.

[Kryten]

Digging up this thread because they've finally finished the repair work.

[Bill Phil]

Here's to the RD-181! (2 191s?)

*raises glass*

Let's hope nothing explodes again on the next versions of Antares.

[Frida Space]

The Indipendent Review Team Accident Investigation Report is out: www.nasa.gov/sites/default/files/atoms/files/orb3_irt_execsumm_0.pdf

what we are all interested in:

"Based on this analysis,the IRT determined that the proximate cause of the Antares launch vehicle failure was an explosionwithin the AJ26rocket engine installed in the Main Engine 1 position. Specifically, there was anexplosion in the E15 Liquid Oxygen (LO2) turbopump, which then damaged the AJ26 rocket enginedesignated E16 installed in the Main Engine 2 position. The explosion caused the engines to lose thrust,and the launch vehicle fell back to Earth and impacted the ground, resulting in total destruction of thevehicle and its cargo."

and what might have caused it:

"The IRT identified three credible technical root causes (TRCs), any one or a combination of which could have resulted in the E15 failure:

• TRC-1: Inadequate design robustness of the AJ26 LO2 HBA (Hydraulic Balance Assembly) and turbine-end bearing forAntares. After performing extensive technical design evaluation and a number of sensitivityanalyses of the LO2 turbopump, it became apparent to the IRT that the HBA and thrust bearingdesigns have several intricacies and sensitivities that make it difficult to reliably manage bearingloads. As a result, this area of the turbopump is vulnerable to oxygen fire and failures. The AJ26engines were not subjected to a thorough delta-qualification program to demonstrate theiroperational capability and margin for use on Antares. Performing a thorough delta-qualificationprogram for Antares would likely have revealed these issues. Furthermore, the Acceptance TestProgram (ATP) established for the AJ26 engines was not sufficient to test and screen the enginesfor these design sensitivities and potential workmanship issues that could exacerbate thosesensitivities.
  

• TRC-2: Foreign Object Debris (FOD) introduction to the E15 LO2 turbopump. Forensicinvestigation identified the presence of both titanium and silica FOD within E15 prior to itsimpact on the beach. However, no firm conclusions can be drawn with respect to the quantity ofFOD introduced to or already present within the engine prior to or at the time of the explosion.The lack of significant particle impact damage to the recovered impeller and other componentsindicates that there were not gross-levels of FOD present within the system. In addition, there isno clear forensic evidence that FOD directly or indirectly led to the E15.
  

• TRC-3: Manufacturing or other workmanship defect in the E15 LO2 turbopump. Forensicinvestigation performed by Orbital ATK and NASA discovered the presence of a defect on theturbine housing bearing bore that was not consistent with baseline design requirements3. Theinvestigation determined that the defect was introduced during machining of the bearing borehousing and was therefore present prior to the engine ATP and Antares launch for Orb-3.Forensic investigation of Engine E17, which failed during ATP in May 2014, discovered thepresence of a similar non-conforming defect in the housing bearing bore. A limited number ofother engine turbine housings (i.e., Engine E16 and the 1998 test engine) previously andsuccessfully subjected to extended ground tests and ATP, as well as an untested spare turbinehousing, were inspected. Neither E16 nor the spare housing showed any evidence of a similarmanufacturing defect. However, the 1998 test engine that had been subjected to extensive groundtesting exhibited a similar defect to that observed in Engines E15 and E17, but it was not possibleto conclude whether the defect was introduced during manufacturing or was the result of wearfrom extended operation of the engine. Sufficient information is not available without furtherengine inspections and tests to conclude that the presence of this manufacturing defect wouldalways result in failure of the engine during operation."
  

[Elthy]

recovered impeller

Wait, they were able to recover something out of this fireball? Amazing...

[Streetwind]

Well, the turbopumps are subject to the highest stresses in the whole engine assembly, so they are made out of absurdly tough materials. The explosion can't have gotten much hotter than what the engine was designed to handle anyway, since rocket engines are basically controlled explosion devices.

But yeah, good work by the forensics team, they must have combed the area for weeks. to collect all the parts.

[Kryten]

Wait, they were able to recover something out of this fireball? Amazing...

Fireballs aren't very destructive, they just look impressive.