lvron@earth.lerc.nasa.gov (Ronald E. Graham) (11/10/90)
I included sci.engr in this follow-up, hoping for some extra technical insight. The original posting was sent to sci.space and sci.astro. In article <1990Nov9.145517.1891@cc.ic.ac.uk>, zmapj36@cc.ic.ac.uk (M. S. Bennett) writes... [From an article entitled "Ariane Returns to Business" by Neville Kidger...] > Arianespace, the company which markets and flies the Ariane launcher, >has resumed operations following the loss of the V36 launcher in February >1990. > The loss of the rocket - with two Japanese commercial satellites >aboard - was found to have been due to the presence of a piece of cloth >in the water supply line to one of the four Viking first stage engines. I've never been part of a failure investigation (thankfully ;-)) since I joined NASA, so I don't know much about the procedure. I hope someone can offer insight on the following questions: (1) the failure was due to a piece of cloth. How could this have been isolated after the failure? (2) what is the mechanism by which a piece of cloth was able to cause the failure? By that I mean - was the cloth of sufficient size/porosity to totally restrict water flow? or did it have to be? - how is a piece of cloth able to be in the water line anyway? - what is the sequence of events leading to the failure, given the presence of the cloth? (3) how can Arianespace ensure no repeat of this mechanism/sequence of events? Please don't give any over-simplified answers like "they screwed up," or "they need to look harder." Unless (3) absolutely requires a very simple answer. I won't assume you know what you're talking about. And, if there are some answers out there, I will gladly summarize. RG - lvron@earth (or mars, or saturn - your choice) .lerc.nasa.gov
a752@mindlink.UUCP (Bruce Dunn) (11/12/90)
> lvron@earth.lerc.nasa.gov writes: > > [commenting on a report that a piece of cloth in a water-line to an engine > caused the Ariane V36 failure on February 22] > > I've never been part of a failure investigation (thankfully ;-)) since I > joined NASA, so I don't know much about the procedure. I hope someone can > offer insight on the following questions: > > (1) the failure was due to a piece of cloth. How could this have been > isolated after the failure? > (2) what is the mechanism by which a piece of cloth was able to cause the > failure? By that I mean > - was the cloth of sufficient size/porosity to totally restrict water > flow? or did it have to be? > - how is a piece of cloth able to be in the water line anyway? > - what is the sequence of events leading to the failure, given the > presence of the cloth? > (3) how can Arianespace ensure no repeat of this mechanism/sequence of > events? > The following information, abbreviated from 3 issues of Spaceflight, may be of interest. May, 1990: The Ariane V36 Inquiry Board has presented its findings. They identify a blocked water line as the cause of the accident. The launcher exploded shortly after its launch on February 22. ... The loss of the mission was due to the decrease in thrust of one of the four Viking V motors on the first stage. The drop in thrust occurred 6.2 seconds after motor ignition. It was due to an almost total obstruction of the water feeding circuit of Viking motor D. The engine itself is not at fault. The obstruction occurred upstream of the motor before the water pump. The precise cause of the obstruction is either a foreign object in the pipe or a failure of the main water valve. [The article goes on to talk about how debris from the exploded launcher fell at the shoreline and just off-shore of the launch site.] A search of mangrove swamps in zone 2 located some 350 different objects from the first, second and third stages. In particular, this search located external tubing of engine D as well as water tank elements. The first stage propulsion bay along with the four Viking motors was found. Despite extremely difficult conditions, the suspect elements of the water circuit were recoverd shortly before this issue of Spaceflight went to press. June, 1990: The loss of Ariane V36 was caused by a small piece of cloth that blocked the water supply to one of the vehicle's first stage engines. ... The rag was probably left in the pipe when the tubing was dismantled and readjusted during first stage integration before transfer to French Guiana. Arianespace Chairman Frederic c'Allest said the cause of the failure was "not only shocking but hard to accept." September, 1990: The investigation into the loss of V36 revealed that a first stage engine lost thrust because a small piece of cloth blocked a water pipe. In an unconnected incident a small fire broke out in one of the strap-on liquid boosters due to a fuel leak. From flight V37, the water line and the N2O4 feed line of each engine will be examined. The inspection will take place at Kourou, using a fibroscope type video camera with integrated light source. ... Additional leak checks were made on the first stage and strap-on fuel lines to ensure that there was no repeat of the fire on the previous mission. Also, new thermal protection inside the propulsion bays of the first stage will protect electrical systems in the event of a fire. Spaceflight is an excellent journal received by members of the British Interplanetary Society. Address: 27/29 South Lambeth Road, London, SW8 1SZ, England. My understanding is that as the engine lost thrust, the remaining engines gimbeled to correct for the thrust imbalance. When the running engines reached the end of their gimbel limits the vehicle could no longer be kept on course, and in effect started to skid sideways through the air. Breakup due to aerodynamic forces followed shortly. What I have not been able to find out is why Viking engines need a water supply. This is presumably for cooling, however I have never heard of an engine that used anything other than its own propellants as a cooling source. Can someone familiar with the Viking engine explain the function of the water, and what happens when its supply is interrupted. -- Bruce Dunn Vancouver, Canada a752@mindlink.UUCP
henry@zoo.toronto.edu (Henry Spencer) (11/14/90)
In article <1990Nov10.151130.29117@eagle.lerc.nasa.gov> lvron@earth.lerc.nasa.gov writes: >(1) the failure was due to a piece of cloth. How could this have been > isolated after the failure? They pinned down possible causes based on the symptoms, and then went through the recovered debris very carefully, and found the cloth. >(2) what is the mechanism by which a piece of cloth was able to cause the > failure? By that I mean > - was the cloth of sufficient size/porosity to totally restrict water > flow? or did it have to be? I believe it was large enough and solid enough to completely block the line. We're not talking about 30-cm pipes here. > - how is a piece of cloth able to be in the water line anyway? Good question. Nobody knows for sure. The obvious possibility is some minor blunder during manufacturing. If that's the case, there is little hope that the person responsible will ever admit it. > - what is the sequence of events leading to the failure, given the > presence of the cloth? Water flow to one engine chokes off, chamber pressure and thrust in that engine drop, the other engines gimbal farther and farther to compensate, eventually they hit their gimbal limits and the booster starts to turn, and the attempt to fly sideways exceeds its structural limits and it breaks up. >(3) how can Arianespace ensure no repeat of this mechanism/sequence of > events? The usual: more care during manufacturing, more thorough inspections, and some managerial changes to clarify who's responsible for that water line (one company had hold of each end and nobody was in charge of the whole thing). -- "I don't *want* to be normal!" | Henry Spencer at U of Toronto Zoology "Not to worry." | henry@zoo.toronto.edu utzoo!henry
herve@cvl.umd.edu (Jean-Yves Herve') (11/14/90)
In article <1990Nov13.185458.5052@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >In article <1990Nov10.151130.29117@eagle.lerc.nasa.gov> lvron@earth.lerc.nasa.gov writes: >>(1) the failure was due to a piece of cloth. How could this have been >> isolated after the failure? >They pinned down possible causes based on the symptoms, and then went through >the recovered debris very carefully, and found the cloth. I seem to remember reading some report stating that the piece of cloth was clean (which meant it hadn't been used for cleaning parts and been forgotten there). Now, how clean can a piece of cloth found among debris be? Or is my memory playing tricks again? Jean-Yves Herve' herve@urdr.umd.edu
mikemr@microsoft.UUCP (Michael MRAZ) (11/15/90)
I'd sure like to know what water is doing in a propulsion system. I don't know anything about the Ariane, but I've never heard of water used for anything other than cooling the pad or quenching astronaut/cosmonaut thirsts. ;-> Can anyone enlighten me, please?